JPWO2014014109A1 - Passivation layer forming composition, semiconductor substrate with passivation layer, method for manufacturing semiconductor substrate with passivation layer, solar cell element, method for manufacturing solar cell element, and solar cell - Google Patents

Abstract

A composition for forming a passivation layer comprising a compound represented by the general formula (I): M (OR1) m, a filler, a liquid medium, and a resin. In general formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. R1 independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. m represents an integer of 1 to 5.

Description

  The present invention relates to a composition for forming a passivation layer, a semiconductor substrate with a passivation layer, a method for manufacturing a semiconductor substrate with a passivation layer, a solar cell element, a method for manufacturing a solar cell element, and a solar cell.

The manufacturing process of the conventional silicon solar cell element is demonstrated.
First, a p-type silicon substrate having a texture structure formed on the light-receiving surface side is prepared so as to promote the light confinement effect and increase the efficiency, and then in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen An n-type diffusion layer is uniformly formed by performing several tens of minutes at 800 ° C. to 900 ° C. In this conventional method, since phosphorus is diffused using a mixed gas, n-type diffusion layers are formed not only on the front surface, which is the light receiving surface, but also on the side surface and the back surface. Therefore, side etching is performed to remove the n-type diffusion layer formed on the side surface. Further, the n-type diffusion layer formed on the back surface needs to be converted into a p ⁺ -type diffusion layer. For this reason, by applying an aluminum paste containing aluminum powder and a binder to the entire back surface and heat-treating (baking) it, the n-type diffusion layer is converted into a p ⁺ -type diffusion layer and an aluminum electrode is formed. Get ohmic contact.

  However, an aluminum electrode formed from an aluminum paste has low conductivity. Therefore, in order to reduce the sheet resistance, the aluminum electrode formed on the entire back surface usually must have a thickness of about 10 μm to 20 μm after heat treatment (firing). Furthermore, since silicon and aluminum have different thermal expansion rates, a large internal stress is generated in the silicon substrate during the heat treatment (firing) and cooling in the silicon substrate on which the aluminum electrode is formed, leading to the grain boundaries. Cause damage, increase of crystal defects and warpage.

In order to solve this problem, there is a method of reducing the applied amount of the aluminum paste and reducing the thickness of the back electrode layer. However, if the amount of aluminum paste applied is reduced, the amount of aluminum diffusing from the surface of the silicon semiconductor substrate to the inside becomes insufficient. As a result, the desired BSF (Back Surface Field) effect (the effect of improving the collection efficiency of the generated carriers due to the presence of the P ⁺ -type diffusion layer) cannot be achieved, resulting in a problem that the characteristics of the solar cell deteriorate. .

In relation to the above, a point contact method has been proposed in which an aluminum paste is applied to a part of the surface of a silicon substrate to partially form a p ⁺ -type diffusion layer and an aluminum electrode (for example, Japanese Patent No. 3107287). (See the publication).
In the case of a solar cell having a point contact structure on the surface opposite to the light receiving surface (hereinafter also referred to as “back surface”), it is necessary to suppress the recombination rate of minority carriers on the surface of the portion other than the aluminum electrode. is there. For this purpose, a SiO ₂ film or the like has been proposed as a passivation layer (see, for example, JP-A-2004-6565). As a passivation effect by forming such a SiO ₂ film, there is an effect of terminating the dangling bonds of silicon atoms in the surface layer portion on the back surface of the silicon substrate, and reducing the surface state density causing recombination. .

As another method of suppressing recombination of minority carriers, there is a method of reducing the minority carrier density by an electric field that generates fixed charges in the passivation layer. Such a passivation effect is generally called a field effect, and an aluminum oxide (Al ₂ O ₃ ) film or the like has been proposed as a material having a negative fixed charge (see, for example, Japanese Patent No. 4767110).
Such a passivation layer is generally formed by a method such as an ALD (Atomic Layer Deposition) method or a CVD (Chemical Vapor Deposition) method (for example, Journal of Applied Physics, 104 (2008), 113703-1 to 113703-7). As a simple method for forming an aluminum oxide film on a semiconductor substrate, a sol-gel method has been proposed (for example, Thin Solid Films, 517 (2009), 6327-6330, and Chinese Physics Letters, 26 (2009 ), 088102-1-088102-4).

  Since the technique described in Journal of Applied Physics, 104 (2008), 113703-1 to 113703-7 includes a complicated manufacturing process such as vapor deposition, it may be difficult to improve productivity. Further, in the method described in Thin Solid Films, 517 (2009), 6327-6330 and Chinese Physics Letters, 26 (2009), 088102-1-088102-4, in the composition for forming a passivation layer used in the sol-gel method, Problems such as gelation occur over time, and it is difficult to say that the storage stability is sufficient.

  Moreover, since the said composition for formation of a passivation layer tends to generate | occur | produce a printing blur when provided on a semiconductor substrate, it is difficult to form the passivation layer of a desired pattern shape on a semiconductor substrate. Note that printing bleeding refers to a phenomenon in which a composition for forming a passivation layer applied on a semiconductor substrate spreads.

  Here, when manufacturing a solar cell using the board | substrate which has uneven | corrugated structures, such as a texture, it is thought that the printing bleeding of the said composition for formation of a passivation layer becomes easy to generate | occur | produce. Moreover, when manufacturing the solar cell which has the said point contact structure, the composition for formation of a passivation layer will be formed with the pattern which opened the opening part (contact part) locally. The dimensions of the opening may be, for example, a diameter of 0.5 mm or less and a pitch of 2 mm or less. In order to form a pattern uniformly, the printing bleeding of the composition for forming a passivation layer is significantly suppressed. Is required.

  The present invention has been made in view of the above-described conventional problems, and has excellent storage stability, and a passivation layer can be formed into a desired shape while suppressing printing bleeding by a simple method. It is an object of the present invention to provide a composition for forming a passivation layer capable of forming a passivation layer having an excellent effect on a semiconductor substrate. The present invention also provides a semiconductor substrate with a passivation layer obtained by using the composition for forming a passivation layer, formed in a desired shape and having a passivation layer having an excellent passivation effect, a method for manufacturing a semiconductor substrate with a passivation layer, a solar It is an object to provide a battery element, a method for manufacturing a solar battery element, and a solar battery.

Specific means for solving the above problems are as follows.
<1> A composition for forming a passivation layer comprising a compound represented by the following general formula (I), a filler, a liquid medium, and a resin.

M (OR ¹ ) _m (I)

In general formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. m represents an integer of 1 to 5.

<2> The composition for forming a passivation layer according to <1>, further comprising a compound represented by the following general formula (II).

In the general formula (II), ^{R 2} each independently represent an alkyl group having 1 to 8 carbon atoms. n represents an integer of 0 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.

<3> The above <1> or <1>, wherein the filler contains at least one particle selected from the group consisting of silicon dioxide, aluminum hydroxide, aluminum nitride, silicon nitride, aluminum oxide, zirconium oxide, and silicon carbide. 2> The composition for forming a passivation layer according to 2>.

<4> The composition for forming a passivation layer according to any one of <1> to <3>, wherein the filler has a volume average particle diameter of 0.01 μm to 50 μm.

<5> The composition for forming a passivation layer according to any one of <1> to <4>, wherein the filler includes glass particles.

<6> The composition for forming a passivation layer according to <5>, wherein the glass particles have a glass softening point of 300 ° C to 1000 ° C.

<7> The total content of the compound represented by the general formula (I) and the compound represented by the general formula (II) is 0.1% by mass to 80% by mass, and the content of the filler is 0.1%. The composition for forming a passivation layer according to any one of <2> to <6>, wherein the total content of the liquid medium and the resin is from 5% by mass to 50% by mass, and from 5% by mass to 98% by mass. .

<8> The composition for forming a passivation layer according to any one of <1> to <7>, which is used for forming a passivation layer on a semiconductor substrate.

<9> A semiconductor substrate, and a passivation layer that is a heat treatment product of the composition for forming a passivation layer according to any one of the above <1> to <8> provided on the entire surface or a part of the semiconductor substrate, A semiconductor substrate with a passivation layer.

<10> A step of forming a composition layer by applying the composition for forming a passivation layer according to any one of <1> to <8> on the entire surface or a part of a semiconductor substrate, and the composition layer And a step of forming a passivation layer by heat-treating a semiconductor substrate with a passivation layer.

<11> A semiconductor substrate in which a p-type layer and an n-type layer are pn-junction, and a passivation layer formation according to any one of <1> to <8> provided on the entire surface or a part of the semiconductor substrate. A solar cell element having a passivation layer, which is a heat-treated product of the composition for use, and an electrode provided on at least one of the p-type layer and the n-type layer.

<12> The passivation layer forming composition according to any one of <1> to <8> above is applied to the entire surface or a part of a semiconductor substrate in which a p-type layer and an n-type layer are pn-junctioned. Forming a composition layer; heat-treating the composition layer to form a passivation layer; and forming an electrode on at least one of the p-type layer and the n-type layer. The manufacturing method of the solar cell element which has.

<13> A solar cell comprising the solar cell element according to <11> above and a wiring material disposed on an electrode of the solar cell element.

  According to the present invention, it is possible to form a passivation layer having a superior passivation effect on a semiconductor substrate, which is excellent in storage stability and can be formed into a desired shape by suppressing printing bleeding by a simple method. A possible composition for forming a passivation layer can be provided. The present invention also provides a semiconductor substrate with a passivation layer obtained by using the composition for forming a passivation layer, formed in a desired shape and having a passivation layer having an excellent passivation effect, a method for manufacturing a semiconductor substrate with a passivation layer, a solar A battery element, a method for manufacturing a solar battery element, and a solar battery can be provided.

It is sectional drawing which shows typically an example of the manufacturing method of the solar cell element which has a passivation layer. It is sectional drawing which shows typically another example of the manufacturing method of the solar cell element which has a passivation layer. It is sectional drawing which shows typically another example of the manufacturing method of the solar cell element which has a passivation layer. It is a schematic plan view which shows an example of the light-receiving surface of a solar cell element. It is a schematic plan view which shows an example of the formation pattern in the back surface of a passivation layer. It is a schematic plan view which shows another example of the formation pattern in the back surface of a passivation layer. It is the schematic plan view to which the A section of FIG. 5 was expanded. It is the schematic plan view to which the B section of FIG. 5 was expanded. It is a schematic plan view which shows an example of the back surface of a solar cell element. It is a figure for demonstrating an example of the manufacturing method of a solar cell. It is sectional drawing which showed the structure of the double-sided electrode type solar cell element. It is sectional drawing which shows the 1st structural example of the solar cell element which concerns on reference embodiment. It is sectional drawing which shows the 2nd structural example of the solar cell element which concerns on reference embodiment. It is sectional drawing which shows the 3rd structural example of the solar cell element which concerns on reference embodiment. It is sectional drawing which shows the 4th structural example of the solar cell element which concerns on reference embodiment. It is sectional drawing which shows another structural example of the solar cell element which concerns on reference embodiment.

  In this specification, the term “process” includes not only an independent process but also an after-use if the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes. . Moreover, the numerical range shown using "to" shows the range which includes the numerical value described before and behind "to" as a minimum value and a maximum value, respectively. Furthermore, the content of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. In addition, in the present specification, the term “layer” includes a configuration of a shape formed in part in addition to a configuration of a shape formed on the entire surface when observed as a plan view.

<Composition for forming a passivation layer>
The composition for forming a passivation layer of the present invention contains a compound represented by the following general formula (I) (hereinafter also referred to as “specific metal alkoxide compound”), a filler, a liquid medium, and a resin. The composition for forming a passivation layer may further contain other components as necessary. With this configuration, a composition for forming a passivation layer that has an excellent passivation effect, excellent storage stability, and can suppress printing bleeding is obtained, and the passivation layer is formed into a desired shape by a simple method. be able to.

M (OR ¹ ) _m (I)

In general formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. m represents an integer of 1 to 5.

  The composition for forming a passivation layer is applied to a semiconductor substrate to form a composition layer having a desired shape, and this is heat-treated (fired) to form a passivation layer having an excellent passivation effect in a desired shape. be able to. The method of the present invention is a simple and highly productive method that does not require a vapor deposition apparatus or the like. Further, the passivation layer can be formed in a desired shape without requiring a complicated process such as mask processing.

  In this specification, the passivation effect of a semiconductor substrate refers to an effective lifetime of minority carriers in a semiconductor substrate on which a passivation layer is formed, by reflection microwave conduction attenuation using a device such as Nippon Semi-Lab Co., Ltd. or WT-2000PVN. It can be evaluated by measuring by the method.

Here, the effective lifetime τ is expressed by the following equation (A) by the bulk lifetime τ _b inside the semiconductor substrate and the surface lifetime τ _s of the semiconductor substrate surface. When the surface state density on the surface of the semiconductor substrate is small, τ _s becomes long, resulting in a long effective lifetime τ. Further, even if defects such as dangling bonds in the semiconductor substrate are reduced, the bulk lifetime τ _b is increased and the effective lifetime τ is increased. That is, by measuring the effective lifetime τ, the interface characteristics between the passivation layer and the semiconductor substrate and the internal characteristics of the semiconductor substrate such as dangling bonds can be evaluated.

1 / τ = 1 / τ _b + 1 / τ _s (A)

  In addition, it shows that the recombination rate of a minority carrier is so slow that effective lifetime (tau) is long. Moreover, conversion efficiency improves by comprising a solar cell element using the semiconductor substrate with a long effective lifetime.

(Compound represented by formula (I))
The composition for forming a passivation layer contains at least one compound represented by the general formula (I) (hereinafter also referred to as “specific metal alkoxide compound”). Here, the specific metal alkoxide compound is an alkoxide containing at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. When the composition for forming a passivation layer contains at least one of these alkoxides, a passivation layer having an excellent passivation effect can be formed. The reason can be considered as follows.

  A metal oxide formed by heat-treating (firing) a composition for forming a passivation layer containing a specific metal alkoxide compound is considered to have defects of metal atoms or oxygen atoms and easily generate fixed charges. When this fixed charge is generated near the interface of the semiconductor substrate, the concentration of minority carriers can be reduced, and as a result, the carrier recombination rate at the interface is suppressed, and an excellent passivation effect is achieved. Conceivable.

  Here, the bonding mode in the passivation layer is examined by analyzing the cross section of the semiconductor substrate by electron energy loss spectroscopy (EELS) using a scanning transmission electron microscope (STEM). be able to. Further, by measuring an X-ray diffraction spectrum (XRD, X-ray diffraction), the crystal phase near the interface of the passivation layer can be confirmed. Furthermore, the fixed charge of the passivation layer can be evaluated by the CV method (Capacitance Voltage measurement).

  In the general formula (I), M includes at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. From the viewpoint of the passivation effect, M is composed of Nb, Ta, and Y. It is preferably at least one selected from the group, and more preferably Nb. Further, from the viewpoint of making the fixed charge density of the passivation layer negative, M is preferably at least one selected from the group consisting of Nb, Ta, VO, and Hf.

In the general formula (I), each R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms, and preferably 1 to 4 carbon atoms. The alkyl group is more preferable. The alkyl group represented by R ¹ may be linear or branched. Specific examples of the alkyl group represented by R ¹ include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, hexyl group, octyl group, 2- Examples thereof include an ethylhexyl group and a 3-ethylhexyl group. Specific examples of the aryl group represented by R ¹ include a phenyl group. Specific examples of the aryl group represented by R ¹ include a phenyl group. The alkyl group and aryl group represented by R ¹ may have a substituent. Examples of the substituent for the alkyl group include a halogen atom, an amino group, a hydroxyl group, a carboxyl group, a sulfone group, and a nitro group. Examples of the substituent for the aryl group include a halogen atom, a methyl group, an ethyl group, an isopropyl group, an amino group, a hydroxyl group, a carboxyl group, a sulfone group, and a nitro group.
Among these, R ¹ is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, and more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms, from the viewpoint of storage stability and a passivation effect.

  In general formula (I), m represents an integer of 1 to 5. From the viewpoint of storage stability, m is preferably 5 when M is Nb, m is preferably 5 when M is Ta, and M is VO. M is preferably 3, m is preferably 3 when M is Y, and m is preferably 4 when M is Hf.

In the compound represented by the general formula (I), from the viewpoint of the passivation effect, M is preferably at least one selected from the group consisting of Nb, Ta and Y, and the fixed charge density of the passivation layer is increased. From the viewpoint of making it negative, M is preferably at least one selected from the group consisting of Nb, Ta, VO, and Hf. From the viewpoint of storage stability and a passivation effect, R ¹ has ¹ carbon atom. It is preferable that it is an unsubstituted alkyl group of -4, and it is preferable that m is an integer of 1-3 from a viewpoint of storage stability.

  Compounds represented by the general formula (I) are niobium methoxide, niobium ethoxide, niobium isopropoxide, niobium n-propoxide, niobium n-butoxide, niobium t-butoxide, niobium isobutoxide, tantalum methoxide, tantalum. Ethoxide, tantalum isopropoxide, tantalum n-propoxide, tantalum n-butoxide, tantalum t-butoxide, tantalum isobutoxide, yttrium methoxide, yttrium ethoxide, yttrium isopropoxide, yttrium n-propoxide, yttrium n- Butoxide, yttrium t-butoxide, yttrium isobutoxide, vanadium methoxide oxide, vanadium ethoxide oxide, vanadium isopropoxide oxide, vanadium n-propoxide oxide , Vanadium n-butoxide oxide, vanadium t-butoxide oxide, vanadium isobutoxide oxide, hafnium methoxide, hafnium ethoxide, hafnium isopropoxide, hafnium n-propoxide, hafnium n-butoxide, hafnium t-butoxide, hafnium isobutoxide Niobium ethoxide, niobium n-propoxide, niobium n-butoxide, tantalum ethoxide, tantalum n-propoxide, tantalum n-butoxide, yttrium isopropoxide, yttrium n-butoxide, etc. Can be mentioned. From the viewpoint of obtaining a negative fixed charge density, niobium ethoxide, niobium n-propoxide, niobium n-butoxide, tantalum ethoxide, tantalum n-propoxide, tantalum n-butoxide, vanadium ethoxide oxide, vanadium n-propoxy Preference is given to oxides, vanadium n-butoxide oxide, hafnium ethoxide, hafnium n-propoxide and hafnium n-butoxide.

  Moreover, the compound represented by general formula (I) may use what was prepared, or may use a commercial item. Commercially available products include, for example, pentamethoxyniobium, pentaethoxyniobium, penta-i-propoxyniobium, penta-n-propoxyniobium, penta-i-butoxyniobium, penta-n-butoxyniobium from High Purity Chemical Laboratory, Inc. , Penta-sec-butoxy niobium, pentamethoxy tantalum, pentaethoxy tantalum, penta-i-propoxy tantalum, penta-n-propoxy tantalum, penta-i-butoxy tantalum, penta-n-butoxy tantalum, penta-sec-butoxy tantalum , Penta-t-butoxytantalum, vanadium (V) trimethoxide oxide, vanadium (V) triethoxy oxide, vanadium (V) tri-i-propoxide oxide, vanadium (V) tri-n-propoxide oxide, vanadium (V Tri-i-butoxide oxide, vanadium (V) tri-n-butoxide oxide, vanadium (V) tri-sec-butoxide oxide, vanadium (V) tri-t-butoxide oxide, tri-i-propoxy yttrium, tri-n -Butoxy yttrium, tetramethoxy hafnium, tetraethoxy hafnium, tetra-i-propoxy hafnium, tetra-t-butoxy hafnium, pentaethoxyniobium, pentaethoxy tantalum, pentaboxy tantalum, yttrium-n-butoxide from Hokuko Chemical Co., Ltd. Hafnium-tert-butoxide, vanadium oxytriethoxide, vanadium oxytrinormal propoxide, vanadium oxytrinormal butoxide, vanadium oxy from Nichia Corporation Riisobutokishido, it can be mentioned vanadium oxy-tri secondary butoxide and the like.

  In the preparation of the compound represented by the general formula (I), a halide of a specific metal (M) and an alcohol are reacted in the presence of an inert organic solvent, and ammonia or an amine compound is used to further extract the halogen. Known methods such as a method of adding (JP-A 63-227593 and JP-A 3-291247) can be used.

  As the compound represented by the general formula (I), a compound in which a chelate structure is formed by mixing with a compound having a specific structure having two carbonyl groups described later may be used. The number of carbonyl groups to be chelated is not particularly limited, but when M is Nb, the number of carbonyl groups to be chelated is preferably 1 to 5, and when M is Ta, the number of carbonyl groups to be chelated is Preferably, the number of carbonyl groups to be chelated is preferably 1 to 3 when M is VO, and the number of carbonyl groups to be chelated is 1 to 3 when M is Y. It is preferable that when M is Hf, the number of carbonyl groups to be chelated is preferably 1 to 4.

  The presence of the chelate structure in the compound represented by the general formula (I) can be confirmed by a commonly used analytical method. For example, it can be confirmed using an infrared spectrum, a nuclear magnetic resonance spectrum, a melting point, or the like.

  The content rate of the specific metal alkoxide compound contained in the composition for forming a passivation layer can be appropriately selected as necessary. The content of the specific metal alkoxide compound can be 0.1% by mass to 80% by mass, and 0.5% by mass to 70% by mass in the composition for forming a passivation layer, from the viewpoint of storage stability and a passivation effect. The mass is preferably 1% by mass, more preferably 1% by mass to 60% by mass, and still more preferably 1% by mass to 50% by mass.

(Filler)
The composition for forming a passivation layer contains at least one filler. Thereby, when applying the composition for forming a passivation layer on a semiconductor substrate by screen printing or the like, the printability can be improved. In addition, the improvement of printability said here means reduction of printing bleeding (a phenomenon in which the composition for forming a passivation layer applied on a substrate spreads).

  Moreover, the passivation effect can be improved by including a filler in the composition for forming a passivation layer. The reason for this can be considered as follows. That is, when a composition for forming a passivation layer containing no filler is applied to a semiconductor substrate and subjected to heat treatment (firing), the formed passivation layer tends to be dense while the thickness of the passivation layer tends to be thin. At this time, if there is a defect such as a void in the passivation layer, moisture or impurities may adhere to the semiconductor substrate from the location, and the effective lifetime of the semiconductor substrate may be reduced.

  On the other hand, the composition for forming a passivation layer contains a filler, so that the fillers are networked by sintering or the like during heat treatment (firing), function as a protective film for the semiconductor substrate, and reduce the effective lifetime. It is thought to suppress. The function as a protective layer for the semiconductor substrate is particularly effective for a semiconductor substrate having an uneven structure such as a texture. That is, by forming the network layer derived from the filler, it is considered that the uneven structure portion existing on the surface of the semiconductor substrate can be protected by the passivation layer, and the passivation effect is improved.

  The filler preferably includes at least one particle selected from the group consisting of silicon dioxide, aluminum hydroxide, aluminum nitride, silicon nitride, aluminum oxide, zirconium oxide, and silicon carbide. A filler may be used alone or in combination of two or more. Here, from the viewpoint of reactivity with a specific metal alkoxide compound, passivation effect, storage stability, and workability, at least one particle selected from the group consisting of silicon dioxide, aluminum hydroxide, and zirconium oxide as a filler. It is preferable that it contains at least one kind of particles selected from the group consisting of silicon dioxide and aluminum hydroxide.

  As an advantage that the composition for forming a passivation layer contains particles of silicon dioxide, it does not react with a specific metal alkoxide compound even during heat treatment (firing) and is stably present in the composition for forming a passivation layer. The point which is excellent in the storage stability of the composition for formation of a passivation layer is mentioned.

  Moreover, it is preferable that a filler is a glass particle from the viewpoint of the reactivity with a specific metal alkoxide compound, a passivation effect, storage stability, and workability | operativity. Examples of the glass particles include those containing at least one selected from the group consisting of silicon dioxide, boron oxide, bismuth oxide, aluminum oxide, zinc oxide, titanium oxide, and calcium oxide.

As an advantage that the composition for forming a passivation layer contains glass particles as a filler, a passivation layer having an excellent passivation effect can be formed. This can be considered, for example, as follows.
The glass particles in the composition for forming a passivation layer are softened during the heat treatment (firing) treatment, so that the glass particles are partly or wholly networked, and a heat treatment product (firing product) of a specific metal alkoxide compound. It is considered that it functions as a protective film for the passivation layer, and suppresses a decrease in effective lifetime. At this time, the lower the softening point of the glass particles, the more easily the above effect can be obtained. However, if the softening point is too low, the viscosity of the molten glass becomes too low during the heat treatment (firing), and the passivation layer is formed on the semiconductor substrate. In some cases, it is difficult to form a passivation layer in a desired shape.

  When the composition for forming a passivation layer contains glass particles, the softening point of the glass particles is 300 ° C. to 1000 ° C. from the viewpoint of network forming ability between glass particles, viscosity of glass after melting, prevention of bleeding of the passivation layer, and lifetime. Is preferably 350 ° C., more preferably 350 ° C. to 800 ° C., and still more preferably 350 ° C. to 750 ° C.

  When the composition for forming a passivation layer contains glass particles, the crystallization temperature of the glass particles is 450 ° C. to 450 ° C. from the viewpoint of network forming ability between the glass particles, viscosity of the glass after melting, prevention of bleeding of the passivation layer, and lifetime. The temperature is preferably 950 ° C, more preferably 450 ° C to 900 ° C, and still more preferably 480 ° C to 900 ° C.

  The volume average particle diameter of the filler is not particularly limited, and the particle diameter when the volume-based integrated value in the particle size distribution is 50% (hereinafter also simply referred to as “particle diameter”, sometimes abbreviated as “D50%”). The thickness is preferably 0.01 μm to 50 μm, more preferably 0.01 μm to 30 μm, still more preferably 0.01 μm to 20 μm, and particularly preferably 0.01 to 10 μm. By setting D50% of the filler to 0.01 μm or more, viscosity characteristics suitable for printing can be imparted to the composition for forming a passivation layer, and printing unevenness and printing bleeding tend to be further suppressed. Moreover, by making D50% of a filler into 50 micrometers or less, it exists in the tendency which can form the network layer derived from a filler more uniformly and can improve the passivation effect more. In addition, the printing unevenness refers to a phenomenon in which the thickness of the composition layer varies depending on a location, which is caused when a part of the screen plate is badly separated when the screen plate is separated from the semiconductor substrate.

  The particle size of the filler is measured by a laser diffraction / scattering particle size distribution analyzer (Beckman Coulter, Inc., LS 13 320). Hereinafter, a more detailed method for measuring the particle diameter will be described. For the measurement, 0.01 g to 0.10 g of filler is used and dispersed in 125 ml of solvent (terpineol). At this time, the refractive index of the solvent is set to 1.48, and the refractive index of the filler is set to the value of each substance (for example, 1.57 in the case of aluminum hydroxide particles). From the particle size distribution measured under the above conditions, the particle size (D50%) when the volume-based integrated value is 50% is calculated.

  Although the said measuring method calculates a particle diameter from the particle size distribution of the filler as a raw material, the particle diameter of a filler can also be measured using the composition for passivation layer formation of this invention. In this case, 1 g of the composition for forming a passivation layer and 9 g of terpineol as a solvent are mixed to obtain a particle size measurement sample. For the measurement of the particle diameter, a laser diffraction scattering method particle size distribution measuring apparatus (Beckman Coulter, LS 13 320) is used as described above. In this case, 0.05 g to 0.50 g of the particle size measurement sample is used, and this is measured by dispersing it in 125 ml of a solvent (terpineol).

  The filler content in the composition for forming a passivation layer is not particularly limited. From the viewpoint of suppressing printing unevenness and printing bleeding, the filler content in the composition for forming a passivation layer is preferably 0.1% by mass to 50% by mass, and preferably 1% by mass to 50% by mass. Is more preferable, and it is still more preferable that it is 2 mass%-45 mass%.

(Liquid medium)
The composition for forming a passivation layer contains at least one liquid medium (solvent or dispersion medium). Thereby, the liquid physical properties (viscosity, surface tension, etc.) of the composition for forming a passivation layer can be adjusted to a required range depending on the application method when applying to a semiconductor substrate or the like.

  There is no restriction | limiting in particular as a liquid medium. Specific examples of the liquid medium include acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, methyl n-hexyl ketone, diethyl ketone, Ketone solvents such as dipropyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone; diethyl ether, methyl ethyl ether, methyl-n-propyl ether, diisopropyl Ether, tetrahydrofuran, methyltetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol Rudi-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol di- n-butyl ether, diethylene glycol methyl-n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl-n-butyl ether, triethylene glycol di-n-butyl ether, triethylene Glycolme Ru-n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl n-butyl ether, tetraethylene glycol di-n-butyl ether, tetraethylene glycol methyl n- Hexyl ether, tetraethylene glycol di-n-butyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol di-n-propyl ether, propylene glycol dibutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl Ethyl ether, dipropylene glycol Cyl-n-butyl ether, dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl-n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl Ethyl ether, tripropylene glycol methyl-n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl-n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetra Propylene glycol methyl-n-butyl ether, tetrapropylene glycol Ether solvents such as alkyl di-n-butyl ether, tetrapropylene glycol methyl-n-hexyl ether, tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate Sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2- (2-butoxyethoxy) ethyl acetate, benzyl acetate, Cyclohexyl acetate, methyl cyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, diethylene glycol methyl ether acetate, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate Dipropylene glycol ethyl ether, glycol diacetate, methoxytriethylene glycol acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, lactic acid n-butyl, n-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, propylene Ester solvents such as glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone; acetonitrile, N-methyl Aprotic polar solvents such as pyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide Methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, n-pentanol, isopentanol, 2-methylbutanol, sec-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octa Nord, n-nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, cyclohexanol, methylcyclohexanol, benzyl alcohol, ethylene glycol, 1,2- Alcohol solvents such as propylene glycol, 1,3-butylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol Monoethyl ether, diethylene glycol mono-n-butyl ether Glycol monoether solvents such as diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether Terpinene such as α-terpinene, terpineol such as α-terpineol (terpineol), terpene solvent such as myrcene, alloocimene, limonene, dipentene, α-pinene, β-pinene, carvone, osimene, ferrandrene; water, etc. . These liquid media are used alone or in combination of two or more.

  The liquid medium preferably contains at least one selected from the group consisting of a terpene solvent, an ester solvent, and an alcohol solvent from the viewpoints of impartability to a semiconductor substrate and pattern formation, and is selected from the group consisting of terpene solvents. More preferably, it contains at least one of the above.

  The content rate of the liquid medium in the composition for forming a passivation layer is determined in consideration of the imparting property, pattern forming property, or storage stability. For example, the content of the liquid medium is preferably 5% by mass to 98% by mass in the total mass of the composition for forming a passivation layer, from the viewpoint of the impartability of the composition and the pattern forming property. More preferably, it is 95 mass%.

(resin)
The composition for forming a passivation layer contains at least one resin. By including a resin, the shape stability of the composition layer formed by applying the composition for forming the passivation layer on the semiconductor substrate is further improved, and the passivation layer is desired in the region where the composition layer is formed. It can be selectively formed in the shape.

The type of resin is not particularly limited. When the composition for forming a passivation layer is applied on a semiconductor substrate, the resin is preferably a resin whose viscosity can be adjusted within a range where a good pattern can be formed. Specific examples of the resin include polyvinyl alcohol, polyacrylamide, polyacrylamide derivatives, polyvinylamide, polyvinylamide derivatives, polyvinylpyrrolidone, polyethylene oxide, polyethylene oxide derivatives, polysulfonic acid, polyacrylamide alkylsulfonic acid, cellulose, and cellulose derivatives (carboxymethylcellulose). , Cellulose ethers such as hydroxyethyl cellulose and ethyl cellulose), gelatin, gelatin derivatives, starch, starch derivatives, sodium alginate, sodium alginate derivatives, xanthan, xanthan derivatives, guar gum, guar gum derivatives, scleroglucan, scleroglucan derivatives, tragacanth, Tragacanth derivative, dextrin, dextrin derivative, (meta) Examples include crylic acid resin, (meth) acrylic acid ester resin (alkyl (meth) acrylate resin, dimethylaminoethyl (meth) acrylate resin, etc.), butadiene resin, styrene resin, siloxane resin, and copolymers thereof. . These resins are used alone or in combination of two or more.
In the present specification, “(meth) acrylic acid” means at least one of “acrylic acid” and “methacrylic acid”, and “(meth) acrylate” means at least one of “acrylate” and “methacrylate”. means.

  Among these resins, from the viewpoint of storage stability and pattern formation, it is preferable to use a neutral resin having no acidic or basic functional group, and even when the content is small, viscosity and From the viewpoint of adjusting thixotropy, it is more preferable to use a cellulose derivative such as ethyl cellulose.

  Further, the molecular weight of the resin is not particularly limited, and it is preferable to adjust appropriately in view of the desired viscosity as the composition for forming a passivation layer. The weight average molecular weight of the resin is preferably 1,000 to 10,000,000, and more preferably 1,000 to 5,000,000, from the viewpoints of storage stability and pattern formation. In addition, the weight average molecular weight of resin is calculated | required by converting using the analytical curve of a standard polystyrene from the molecular weight distribution measured using GPC (gel permeation chromatography). The calibration curve is approximated by a cubic equation using a standard polystyrene 5 sample set (PStQuick MP-H, PStQuick B [Tosoh Corporation, trade name]). The measurement conditions for GPC are shown below.

Device: (Pump: L-2130 [Hitachi High-Technologies Corporation])
(Detector: L-2490 RI [Hitachi High-Technologies Corporation])
(Column oven: L-2350 [Hitachi High-Technologies Corporation])
Column: Gelpack GL-R440 + Gelpack GL-R450 + Gelpack GL-R400M (3 in total) (Hitachi Chemical Co., Ltd., trade name)
Column size: 10.7 mm (inner diameter) x 300 mm
Eluent: Tetrahydrofuran Sample concentration: 10 mg / 2 mL
Injection volume: 200 μL
Flow rate: 2.05 mL / min Measurement temperature: 25 ° C

The content of the resin in the composition for forming a passivation layer can be appropriately selected as necessary. For example, the resin content is preferably 0.1% by mass to 50% by mass in the total mass of the composition for forming a passivation layer. From the viewpoint of expressing thixotropy that facilitates pattern formation, the resin content is more preferably 0.2% by mass to 25% by mass, and 0.5% by mass to 20% by mass. Is more preferable, and it is particularly preferably 0.5% by mass to 15% by mass.
In the composition for forming a passivation layer, the total content of the liquid medium and the resin in the composition for forming a passivation layer is 5% by mass to 98% by mass from the viewpoint of improving storage stability, pattern forming property, and printability. Preferably there is.

(Compound represented by formula (II))
The composition for forming a passivation layer may contain at least one compound represented by the general formula (II) (hereinafter also referred to as “organoaluminum compound”). When the composition for forming a passivation layer contains an organoaluminum compound, the passivation effect can be further improved. This can be considered as follows.

The organoaluminum compound includes compounds called aluminum alkoxide, aluminum chelate and the like, and preferably has an aluminum chelate structure in addition to the aluminum alkoxide structure. Further, as described in Nippon Seramikkusu Kyokai Gakujitsu Ronbunshi, vol. 97, pp369-399 (1989), the organoaluminum compound becomes aluminum oxide (Al ₂ O ₃ ) by heat treatment (firing). At this time, since the formed aluminum oxide is likely to be in an amorphous state, a four-coordinate aluminum oxide layer is easily formed in the vicinity of the interface with the semiconductor substrate, and may have a large negative fixed charge due to the four-coordinate aluminum oxide. It is considered possible. At this time, it is considered that a passivation layer having an excellent passivation effect can be formed by compounding with an oxide derived from a specific metal alkoxide compound having a fixed charge.

In general formula (II), R ² each independently represents an alkyl group having 1 to 8 carbon atoms is preferably an alkyl group having 1 to 4 carbon atoms. The alkyl group represented by R ² may be linear or branched. Specific examples of the alkyl group represented by R ² include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, hexyl group, octyl group, 2- Examples thereof include an ethylhexyl group and a 3-ethylhexyl group. Among them, the alkyl group represented by R ² is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms from the viewpoint of storage stability and a passivation effect, and is an unsubstituted alkyl group having 1 to 4 carbon atoms. More preferably.

In general formula (II), n represents an integer of 0 to 3. From the viewpoint of storage stability, n is preferably an integer of 1 to 3, and more preferably 1 or 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. From the viewpoint of storage stability, at least one of X ² and X ³ is preferably an oxygen atom.

R ³ , R ⁴ and R ⁵ in the general formula (II) each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. The alkyl group represented by R ³ , R ⁴ and R ⁵ may be linear or branched. The alkyl group represented by R ³ , R ⁴ and R ⁵ may have a substituent or may be unsubstituted, and is preferably unsubstituted. The alkyl group represented by R ³ , R ⁴ and R ⁵ is an alkyl group having 1 to 8 carbon atoms, and preferably an alkyl group having 1 to 4 carbon atoms. Specific examples of the alkyl group represented by R ³ , R ⁴ and R ⁵ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, and a hexyl group. Octyl group, ethylhexyl group and the like.

Among these, from the viewpoint of storage stability and a passivation effect, R ³ and R ⁴ in the general formula (II) are preferably each independently a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms. Or it is more preferable that it is a C1-C4 unsubstituted alkyl group.
In addition, R ⁵ in the general formula (II) is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms from the viewpoint of storage stability and a passivation effect, and is preferably a hydrogen atom or 1 to 4 carbon atoms. The unsubstituted alkyl group is more preferable.

The compound represented by the general formula (II) is a compound in which n is 1 to 3 and R ⁵ is independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms from the viewpoint of storage stability. It is preferable.

The compound represented by the general formula (II) is a compound in which n is 0, R ² is each independently an alkyl group having 1 to 4 carbon atoms, and n is from the viewpoint of storage stability and a passivation effect. 1 to 3, R ² is independently an alkyl group having 1 to 4 carbon atoms, at least one of X ² and X ³ is an oxygen atom, and R ³ and R ⁴ are each independently a hydrogen atom. or an alkyl group having 1 to 4 carbon atoms, it is preferably at least one R ⁵ is selected from each independently consisting of a hydrogen atom or an alkyl group is a compound having 1 to 4 carbon atoms in the group.
More preferably, in the compound represented by the general formula (II), n is 0, R ² is each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, and n is 1 to 3 R ² is each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, at least one of X ² and X ³ is an oxygen atom, and R ³ or R ⁴ bonded to the oxygen atom is A group consisting of a compound having an alkyl group having 1 to 4 carbon atoms and when X ² or X ³ is a methylene group, R ³ or R ⁴ bonded to the methylene group is a hydrogen atom, and R ⁵ is a hydrogen atom; It is at least one selected from more.

  Specific examples of the aluminum trialkoxide, which is an organoaluminum compound represented by the general formula (II) and n is 0, include trimethoxyaluminum, triethoxyaluminum, triisopropoxyaluminum, trisec-butoxyaluminum, monosec-butoxy -Diisopropoxyaluminum, tri-t-butoxyaluminum, tri-n-butoxyaluminum, etc. can be mentioned.

  Specific examples of the organoaluminum compound represented by the general formula (II) where n is 1 to 3 include aluminum ethyl acetoacetate diisopropylate and tris (ethyl acetoacetate) aluminum.

  Moreover, as the organoaluminum compound represented by the general formula (II) and n is 1 to 3, a prepared product or a commercially available product may be used. Examples of commercially available products include Kawaken Fine Chemical Co., Ltd. trade names, ALCH, ALCH-50F, ALCH-75, ALCH-TR, ALCH-TR-20, and the like.

  The organoaluminum compound represented by the general formula (II) and n is 1 to 3 can be prepared by mixing an aluminum trialkoxide and a compound having a specific structure having two carbonyl groups. A commercially available aluminum chelate compound may also be used.

  When an aluminum trialkoxide and a compound having a specific structure having two carbonyl groups are mixed, at least a part of the alkoxide group of the aluminum trialkoxide is substituted with the compound having the specific structure to form an aluminum chelate structure. At this time, if necessary, a liquid medium may be present, or heat treatment, addition of a catalyst, and the like may be performed. By replacing at least a part of the aluminum alkoxide structure with the aluminum chelate structure, the stability of the organoaluminum compound to hydrolysis and polymerization reaction is improved, and the storage stability of the composition for forming a passivation layer containing this is further improved. To do.

  The compound having a specific structure having two carbonyl groups may be at least one selected from the group consisting of a β-diketone compound, a β-ketoester compound, and a malonic acid diester from the viewpoint of reactivity and storage stability. preferable.

  Specific examples of the β-diketone compound include acetylacetone, 3-methyl-2,4-pentanedione, 2,3-pentanedione, 3-ethyl-2,4-pentanedione, and 3-butyl-2,4-pentane. Examples include dione, 2,2,6,6-tetramethyl-3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione, 6-methyl-2,4-heptanedione, and the like.

  Specific examples of β-ketoester compounds include methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, isobutyl acetoacetate, butyl acetoacetate, t-butyl acetoacetate, pentyl acetoacetate, isopentyl acetoacetate, hexyl acetoacetate, acetoacetic acid n-octyl, heptyl acetoacetate, 3-pentyl acetoacetate, ethyl 2-acetylheptanoate, ethyl 2-butylacetoacetate, ethyl 4,4-dimethyl-3-oxovalerate, ethyl 4-methyl-3-oxovalerate , Ethyl 2-ethylacetoacetate, ethyl hexylacetoacetate, methyl 4-methyl-3-oxovalerate, isopropyl acetoacetate, ethyl 3-oxohexanoate, ethyl 3-oxovalerate, methyl 3-oxovalerate, 3- Methyl oxohexanoate, 2-methylacetoacetate Le, ethyl 3-oxo heptanoic acid, 3-oxo heptanoic acid methyl, can be mentioned 4,4-dimethyl-3-oxo-valerate, such as methyl.

  Specific examples of the malonic acid diester include dimethyl malonate, diethyl malonate, dipropyl malonate, diisopropyl malonate, dibutyl malonate, di-t-butyl malonate, dihexyl malonate, t-butylethyl malonate, methyl malonate Examples include diethyl, diethyl ethylmalonate, diethyl isopropylmalonate, diethyl butylmalonate, diethyl sec-butylmalonate, diethyl isobutylmalonate, diethyl 1-methylbutylmalonate, and the like.

  When the organoaluminum compound has an aluminum chelate structure, the number of aluminum chelate structures is not particularly limited as long as it is 1 to 3. Among these, 1 or 3 is preferable from the viewpoint of storage stability, and 1 is more preferable from the viewpoint of solubility. The number of aluminum chelate structures can be controlled, for example, by appropriately adjusting the ratio of mixing aluminum trialkoxide and a compound having a specific structure having two carbonyl groups. Moreover, you may select suitably the compound which has a desired structure from a commercially available aluminum chelate compound.

  Of the compounds represented by the general formula (II), at least selected from the group consisting of aluminum ethylacetoacetate diisopropylate and triisopropoxyaluminum from the viewpoint of the passivation effect and compatibility with the liquid medium One type is preferably used, and aluminum ethyl acetoacetate diisopropylate is more preferably used.

  The presence of the aluminum chelate structure in the organoaluminum compound can be confirmed by a commonly used analytical method. For example, it can be confirmed using an infrared spectrum, a nuclear magnetic resonance spectrum, a melting point, or the like.

  The organoaluminum compound may be liquid or solid and is not particularly limited. From the viewpoint of the passivation effect and storage stability, an organoaluminum compound having favorable stability at room temperature (25 ° C.) and good solubility or dispersibility is preferable. By using such a specific organoaluminum compound, the homogeneity of the formed passivation layer can be further improved, and a desired passivation effect can be stably obtained.

  When the composition for forming a passivation layer contains an organoaluminum compound, the content of the organoaluminum compound can be appropriately selected as necessary. The total content of the specific metal alkoxide compound and the organoaluminum compound can be 0.1% by mass to 80% by mass in the composition for forming a passivation layer from the viewpoint of storage stability and a passivation effect. It is preferably 1% by mass to 50% by mass, more preferably 0.1% by mass to 45% by mass, still more preferably 0.5% by mass to 45% by mass, and 1% by mass to 40%. It is particularly preferable that the content is% by mass.

(Other ingredients)
The composition for forming a passivation layer may contain an acidic compound or a basic compound. When the composition for forming a passivation layer contains an acidic compound or a basic compound, from the viewpoint of storage stability, the content of the acidic compound or the basic compound is 1% by mass or less in the composition for forming a passivation layer, respectively. It is preferable that the content is 0.1% by mass or less.

  Examples of acidic compounds include Bronsted acid and Lewis acid. Specific examples include inorganic acids such as hydrochloric acid and nitric acid, and organic acids such as acetic acid. Examples of basic compounds include Bronsted bases and Lewis bases. Specifically, examples of the basic compound include inorganic bases such as alkali metal hydroxides and alkaline earth metal hydroxides; organic bases such as trialkylamine and pyridine.

<Semiconductor substrate with passivation layer>
The semiconductor substrate with a passivation layer of the present invention includes a semiconductor substrate and a passivation layer (baked product layer) that is a heat treatment product of the composition for forming a passivation layer provided on the entire surface or a part of the semiconductor substrate. The semiconductor substrate with a passivation layer exhibits an excellent passivation effect by having a passivation layer that is a heat-treated product layer (baked product layer) of the composition for forming a passivation layer.

The semiconductor substrate is not particularly limited, and can be appropriately selected from those usually used according to the purpose. Examples of the semiconductor substrate include those obtained by doping (diffusing) p-type impurities or n-type impurities into silicon, germanium, or the like. In particular, the semiconductor substrate is preferably a silicon substrate. The semiconductor substrate may be a p-type semiconductor substrate or an n-type semiconductor substrate. Among these, from the viewpoint of the passivation effect, it is preferable that the surface on which the passivation layer is formed is a semiconductor substrate having a p-type layer. Even if the p-type layer on the semiconductor substrate is a p-type layer derived from the p-type semiconductor substrate, the p-type layer is formed on the n-type semiconductor substrate or the p-type semiconductor substrate as a p-type diffusion layer or a p ⁺ -type diffusion layer. It may be a thing.

  The thickness in particular of a semiconductor substrate is not restrict | limited, According to the objective, it can select suitably. For example, the thickness of the semiconductor substrate can be 50 μm to 1000 μm, and preferably 75 μm to 750 μm.

  The thickness of the passivation layer formed on the semiconductor substrate is not particularly limited and can be appropriately selected depending on the purpose. For example, the average thickness of the passivation layer is preferably 5 nm to 50 μm, preferably 10 nm to 30 μm, and more preferably 15 nm to 20 μm.

  The semiconductor substrate with a passivation layer can be applied to a solar cell element, a light emitting diode element, or the like. For example, a solar cell element and a solar cell excellent in conversion efficiency can be obtained by applying a semiconductor substrate with a passivation layer to a solar cell element. When the semiconductor substrate with a passivation layer is applied to a solar cell element, the passivation layer may be provided on either the light receiving surface side or the back surface side of the solar cell element. Moreover, the passivation layer may be provided on the side surface side of the solar cell element.

<Method for manufacturing semiconductor substrate with passivation layer>
The method for producing a semiconductor substrate with a passivation layer according to the present invention includes a step of forming the composition layer by applying the composition for forming a passivation layer on the entire surface or a part of the semiconductor substrate, and heat-treating the composition layer ( Firing) to form a passivation layer. The manufacturing method may further include other steps as necessary.

  By using the composition for forming a passivation layer of the present invention, printing bleeding can be suppressed and the passivation layer can be formed into a desired shape by a simple method. Moreover, the passivation layer excellent in the passivation effect can be more uniformly formed on the application surface of the semiconductor substrate by using the composition for forming a passivation layer of the present invention.

  As the semiconductor substrate with a passivation layer, those described for the semiconductor substrate with a passivation layer can be used, and those that can be suitably used are also the same.

  It is preferable that the manufacturing method of the semiconductor substrate with a passivation layer further has the process of providing aqueous alkali solution on a semiconductor substrate before the process of forming a composition layer. That is, it is preferable to wash the surface of the semiconductor substrate with an alkaline aqueous solution before applying the composition for forming a passivation layer on the semiconductor substrate. By washing with an alkaline aqueous solution, organic substances, particles, and the like present on the surface of the semiconductor substrate can be removed, and the passivation effect is further improved.

  As a method for cleaning with an alkaline aqueous solution, generally known RCA cleaning and the like can be exemplified. For example, the semiconductor substrate is immersed in a mixed solution of aqueous ammonia and hydrogen peroxide and treated at 60 ° C. to 80 ° C., whereby organic substances and particles are removed from the surface of the semiconductor substrate, and the semiconductor substrate can be cleaned. The cleaning time is preferably 10 seconds to 10 minutes, and more preferably 30 seconds to 5 minutes.

  There is no particular limitation on the method of forming the composition layer by applying the passivation layer forming composition on the semiconductor substrate. For example, a method for applying a composition for forming a passivation layer on a semiconductor substrate using a known application method or the like can be mentioned. Specifically, examples of the application method include screen printing, an ink jet method, a dispenser method, and the like. From the viewpoint of productivity, screen printing is preferable.

  The application amount of the composition for forming a passivation layer can be appropriately selected according to the purpose. For example, the application amount of the composition for forming a passivation layer can be appropriately adjusted so that the thickness of the formed passivation layer becomes a desired thickness described later.

When the composition for forming a passivation layer is applied by screen printing, the viscosity of the composition for forming a passivation layer can be set to 0.01 Pa · s to 10,000 Pa · s. Among these, from the viewpoint of pattern formability, the viscosity of the composition for forming a passivation layer is preferably 0.1 Pa · s to 1000 Pa · s. The viscosity is measured at 25 ° C. and a shear rate of 1.0 s ⁻¹ using a rotary shear viscometer.

Moreover, it is preferable that the composition for forming a passivation layer has thixotropy. From the viewpoint of pattern formability, thixotropic index is calculated by dividing the shear viscosity eta ₂ of the shear viscosity eta ₁ at a shear rate of 1.0 s ^-1 at a shear rate of ^{_{10s -1 (η 1 / η 2}} ) is 1. It is preferable that it is 05-100, and it is more preferable that it is 1.1-50. The shear viscosity is measured at a temperature of 25 ° C. using a rotary shear viscometer equipped with a cone plate (diameter 50 mm, cone angle 1 °).

A passivation layer is formed on a semiconductor substrate by heat-treating (baking) the composition layer formed by the composition for forming a passivation layer to form a heat-treated material layer (baked material layer) derived from the composition layer. be able to.
The heat treatment (firing) condition of the composition layer is the heat treatment product of the compound represented by the general formula (I) contained in the composition layer and the compound represented by the general formula (II) contained as necessary. If it can convert into the metal oxide or composite oxide which is (baked product), it will not be restrict | limited in particular. In order to effectively give a fixed charge to the passivation layer and obtain a more excellent passivation effect, specifically, the heat treatment (firing) temperature is preferably 300 ° C to 900 ° C, more preferably 450 ° C to 800 ° C. The heat treatment (firing) temperature here means the maximum temperature in the furnace used for the heat treatment (firing). The heat treatment (firing) time can be appropriately selected according to the heat treatment (firing) temperature and the like. For example, the heat treatment (firing) time can be 0.1 hour to 10 hours, preferably 0.1 hour to 5 hours. The heat treatment (firing) time here means the holding time at the maximum temperature.

  In addition, heat processing (baking) can be performed using a diffusion furnace (for example, ACCURON CQ-1200, Hitachi Kokusai Electric). The atmosphere in which the heat treatment (firing) is performed is not particularly limited, and can be performed in the air.

The thickness of the passivation layer produced by the method for producing a semiconductor substrate with a passivation layer is not particularly limited and can be appropriately selected according to the purpose. For example, the average thickness of the passivation layer is preferably 5 nm to 50 μm, more preferably 10 nm to 30 μm, and still more preferably 15 nm to 20 μm.
The average thickness of the passivation layer is calculated as an arithmetic average value obtained by measuring the thickness at three points by an ordinary method using an interference film thickness meter (for example, F20 film thickness measurement system, Filmetrics Co., Ltd.). The

  A method of manufacturing a semiconductor substrate with a passivation layer includes: a composition layer comprising a composition for forming a passivation layer, after the composition for forming a passivation layer is applied to the semiconductor substrate and before the step of forming the passivation layer by heat treatment (firing). You may further have the process of drying-processing. By including the step of drying the composition layer, a passivation layer having a more uniform passivation effect can be formed.

  The step of drying the composition layer is not particularly limited as long as at least a part of the liquid medium contained in the composition for forming a passivation layer can be removed. The drying treatment can be, for example, a heat treatment at 30 ° C. to 250 ° C. for 1 minute to 60 minutes, and is preferably a heat treatment at 40 ° C. to 220 ° C. for 3 minutes to 40 minutes. The drying treatment may be performed under normal pressure or under reduced pressure.

  The manufacturing method of the semiconductor substrate with a passivation layer is a method of degreasing a composition layer made of the composition for forming a passivation layer after applying the composition for forming a passivation layer and before the step of forming the passivation layer by heat treatment (firing). You may have further the process to do. By having a step of degreasing the composition layer, a passivation layer having a more uniform passivation effect can be formed.

  The step of degreasing the composition layer is not particularly limited as long as at least part of the resin contained in the composition for forming a passivation layer can be removed. The degreasing treatment can be, for example, a heat treatment at 250 ° C. to 450 ° C. for 10 minutes to 120 minutes, and preferably a heat treatment at 300 ° C. to 400 ° C. for 3 minutes to 60 minutes. The degreasing treatment is preferably performed in the presence of oxygen, and more preferably performed in the air.

<Solar cell element>
The solar cell element of the present invention is a passivation that is a heat treatment product of a semiconductor substrate in which a p-type layer and an n-type layer are pn-junction, and the passivation layer forming composition provided on the entire surface or part of the semiconductor substrate. A layer, and an electrode provided on at least one of the p-type layer and the n-type layer of the semiconductor substrate. The solar cell element may further include other components as necessary.
A solar cell element is excellent in conversion efficiency by having the passivation layer formed from the composition for passivation layer formation of this invention.

  It does not restrict | limit especially as a semiconductor substrate which provides the composition for formation of a passivation layer, According to the objective, it can select suitably from what is normally used. What was demonstrated by the semiconductor substrate with a passivation layer can be used, and what can be used conveniently is also the same. In addition, the surface of the semiconductor substrate on which the passivation layer is provided may be any of the light receiving surface, the back surface, and the side surface of the solar cell element.

Further, the thickness of the passivation layer formed on the semiconductor substrate is not particularly limited and can be appropriately selected depending on the purpose. For example, the average thickness of the passivation layer is preferably 5 nm to 50 μm, preferably 10 nm to 30 μm, and more preferably 15 nm to 20 μm.
There is no restriction | limiting in the shape and magnitude | size of a solar cell element, For example, it is preferable that one side is a square with 125-156 mm.

<Method for producing solar cell element>
In the method for producing a solar cell element of the present invention, the composition layer is formed by applying the passivation layer forming composition to the entire surface or a part of a semiconductor substrate in which a p-type layer and an n-type layer are pn-junctioned. A step of heat-treating (baking) the composition layer to form a passivation layer, and a step of forming an electrode on at least one of the p-type layer and the n-type layer. The manufacturing method of the solar cell element may further include other steps as necessary.

  By using the composition for forming a passivation layer, it is possible to produce a solar cell element that suppresses printing bleeding and is excellent in conversion efficiency by a simple method. Furthermore, the passivation layer can be formed on the semiconductor substrate so as to have a desired shape, and the productivity of the solar cell element is excellent.

  As a method for forming an electrode on at least one of a p-type layer and an n-type layer in a semiconductor substrate, a commonly used method can be employed. For example, it can be manufactured by applying an electrode forming paste such as a silver paste or an aluminum paste to a desired region of a semiconductor substrate and performing a heat treatment (firing) as necessary.

The surface of the semiconductor substrate on which the passivation layer is provided may be a p-type layer or an n-type layer. Among these, a p-type layer is preferable from the viewpoint of conversion efficiency.
The details of the method for forming a passivation layer using the composition for forming a passivation layer are the same as the method for manufacturing a semiconductor substrate with a passivation layer described above, and the preferred embodiments are also the same.

  The thickness of the passivation layer formed on the semiconductor substrate is not particularly limited and can be appropriately selected depending on the purpose. For example, the average thickness of the passivation layer is preferably 5 nm to 50 μm, more preferably 10 nm to 30 μm, and still more preferably 15 nm to 20 μm.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view schematically showing an example of a method for producing a solar cell element having a passivation layer according to this embodiment. However, this process diagram does not limit the present invention at all.

  In FIG. 1A, the p-type semiconductor substrate 1 is washed with an alkaline aqueous solution to remove organic substances, particles, and the like on the surface of the p-type semiconductor substrate 1. Thereby, the passivation effect improves more. As a cleaning method using an alkaline aqueous solution, generally known RCA cleaning or the like can be used.

  Thereafter, as shown in FIG. 1B, the surface of the p-type semiconductor substrate 1 is subjected to alkali etching or the like to form irregularities (also referred to as texture) on the surface. Thereby, reflection of sunlight can be suppressed on the light receiving surface side. For alkali etching, an etching solution composed of NaOH and IPA (isopropyl alcohol) can be used.

Next, as shown in FIG. 1 (3), by thermally diffusing phosphorus or the like on the surface of the p-type semiconductor substrate 1, an n ⁺ -type diffusion layer 2 is formed with a depth of submicron order, A pn junction is formed at the boundary with the p-type bulk portion.

As a method for diffusing phosphorus, for example, a method of performing several tens of minutes at 800 ° C. to 1000 ° C. in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen can be cited. In this method, since phosphorus is diffused using a mixed gas, the n ⁺ -type diffusion layer 2 is formed not only on the light receiving surface (front surface) but also on the back surface and side surfaces (not shown) as shown in FIG. Is formed. A PSG (phosphosilicate glass) layer 3 is formed on the n ⁺ -type diffusion layer 2. Therefore, side etching is performed to remove the side PSG layer 3 and the n ⁺ -type diffusion layer 2.

Thereafter, as shown in FIG. 1 (4), the PSG layer 3 on the light receiving surface and the back surface is removed using an etching solution such as hydrofluoric acid. Further, as shown in FIG. 1 (5), the back surface is separately etched to remove the n ⁺ -type diffusion layer 2 on the back surface.

Then, as shown in FIG. 1 (6), an antireflection film 4 such as silicon nitride is formed on the n ⁺ type diffusion layer 2 on the light receiving surface by a PECVD (Plasma Enhanced Chemical Vapor Deposition) method or the like at a thickness of about 90 nm. Provide.

  Next, as shown in FIG. 1 (7), the composition for forming a passivation layer of the present invention is applied to a part of the back surface by screen printing or the like, followed by heat treatment (baking) at a temperature of 400 ° C. to 900 ° C. after drying. To form a passivation layer 5.

In FIG. 5, an example of the formation pattern of the passivation layer 5 in the back surface is shown as a schematic plan view. FIG. 7 is an enlarged schematic plan view of a portion A in FIG. FIG. 8 is an enlarged schematic plan view of a portion B in FIG. In the case of the formation pattern of the passivation layer 5 shown in FIG. 5, as can be seen from FIGS. 7 and 8, the passivation layer 5 on the back surface has a dot shape except for a portion where the back surface output extraction electrode 7 is formed in a later step. The p-type semiconductor substrate 1 is formed with an exposed pattern. The pattern of the dot-shaped openings is defined by the dot diameter (L _a ) and the dot interval (L _b ), and is preferably arranged regularly. Dot diameter _{(L a)} and the dot interval _{(L b)} can be arbitrarily set, in view of the recombination-inhibiting passivation effect and minority carriers, it is preferable that _{L a} is _{L b} is 10μm~3mm in 5μm~2mm , more preferably _{L a} is _{L b} is 20μm~2.5mm in 10Myuemu～1.5Mm, it is more preferable _{L a} is _{L b} in 20μm~1.3mm is 30Myuemu～2mm.

  Next, as shown in FIG. 1 (8), a silver electrode paste containing glass particles is applied to the light receiving surface by screen printing or the like. FIG. 4 is a schematic plan view showing an example of the light receiving surface of the solar cell element. As shown in FIG. 4, the light receiving surface electrode includes a light receiving surface current collecting electrode 8 and a light receiving surface output extraction electrode 9. In order to secure a light receiving area, it is necessary to suppress the formation area of these light receiving surface electrodes. In addition, from the viewpoint of the resistivity and productivity of the light receiving surface electrode, the width of the light receiving surface current collecting electrode 8 is preferably 10 μm to 250 μm, and the width of the light receiving surface output extraction electrode 9 is preferably 100 μm to 2 mm. In FIG. 4, two light receiving surface output extraction electrodes 9 are provided. However, from the viewpoint of minority carrier extraction efficiency (power generation efficiency), the number of light receiving surface output extraction electrodes 9 may be three or four. it can.

  On the other hand, as shown in FIG. 1 (8), an aluminum electrode paste containing glass powder and a silver electrode paste containing glass particles are applied to the back surface by screen printing or the like. FIG. 9 is a schematic plan view showing an example of the back surface of the solar cell element. The width of the back surface output extraction electrode 7 is not particularly limited, and the width of the back surface output extraction electrode 7 is preferably 100 μm to 10 mm from the viewpoint of the connectivity of the wiring material in the subsequent manufacturing process of the solar cell.

  After applying the electrode paste to the light receiving surface and the back surface, after drying, the light receiving surface and the back surface are both heat-treated (fired) at a temperature of about 450 ° C. to 900 ° C. in the atmosphere, and the light receiving surface collecting electrode 8 And the light receiving surface output extraction electrode 9 and the back surface collecting electrode 6 and the back surface output extraction electrode 7 are formed on the back surface, respectively.

After heat treatment (firing), as shown in FIG. 1 (9), on the light receiving surface, the glass particles contained in the silver electrode paste forming the light receiving surface electrode react with the antireflection film 4 (fire through), The light-receiving surface electrode (light-receiving surface current collecting electrode 8, light-receiving surface output extraction electrode 9) and the n ⁺ -type diffusion layer 2 are electrically connected (ohmic contact). On the other hand, on the back surface, in the portion where the semiconductor substrate 1 is exposed in the form of dots (the portion where the passivation layer 5 is not formed), the aluminum in the aluminum electrode paste diffuses into the semiconductor substrate 1 by heat treatment (firing). , P ⁺ -type diffusion layer 10 is formed. By using the composition for forming a passivation layer of the present invention, it is possible to form a passivation layer that can suppress printing bleeding and can be formed into a desired shape, and by improving the passivation effect, solar power with excellent power generation performance A battery element can be manufactured.

FIG. 2 is a cross-sectional view showing another example of a method for manufacturing a solar cell element having a passivation layer according to this embodiment, and the n ⁺ -type diffusion layer 2 on the back surface is removed by an etching process. After that, the solar battery cell can be manufactured in the same manner as in FIG. 1 except that the back surface is further flattened. When flattening, a technique such as immersing the back surface of the semiconductor substrate in a mixed solution of nitric acid, hydrofluoric acid and acetic acid or a potassium hydroxide solution can be used.

FIG. 3 is a cross-sectional view showing a process diagram illustrating another example of a method for manufacturing a solar cell element having a passivation layer according to the present embodiment. This method is the same as the method of FIG. 1 until the step of forming the texture structure, the n ⁺ -type diffusion layer 2 and the antireflection film 4 on the semiconductor substrate 1 (FIGS. 3 (19) to (24)).

  After forming the antireflection film 4, a composition for forming a passivation layer is applied as shown in FIG. In FIG. 6, an example of the formation pattern of the passivation layer in the back surface is shown as a schematic plan view. In the formation pattern of the passivation layer shown in FIG. 6, dot-like openings are arranged on the entire back surface, and dot-like openings are also arranged on the portion where the back-surface output extraction electrode is formed in a later step.

Thereafter, as shown in FIG. 3 (26), from the portion where the semiconductor substrate 1 in a dot shape is exposed (the portion passivation layer 5 is not formed) on the rear surface, to diffuse boron or aluminum, p ⁺ -type diffusion layer 10 Form. When boron is diffused when forming the p ⁺ -type diffusion layer, a method of treating at a temperature of about 1000 ° C. in a gas containing boron trichloride (BCl ₃ ) can be used. However, since it is a gas diffusion method as in the case of using phosphorus oxychloride, the p ⁺ -type diffusion layer 10 is formed on the light-receiving surface, the back surface, and the side surface of the semiconductor substrate 1. It is necessary to take measures such as masking the portions other than the dot-shaped openings to prevent boron from diffusing into unnecessary portions of the p-type semiconductor substrate 1.

In addition, when aluminum is diffused when forming the p ⁺ -type diffusion layer 10, an aluminum paste is applied to the dot-shaped opening, and this is heat-treated (fired) at a temperature of 450 ° C. to 900 ° C. to form the dot-shaped opening. A p ⁺ -type diffusion layer 10 is formed by diffusing aluminum from the portion, and then etched with hydrochloric acid or the like to form a heat-treated product layer (baked product layer) derived from the aluminum paste formed on the p ⁺ -type diffusion layer 10 A method of removing can be used.

  Next, as shown in FIG. 3 (27), aluminum electrode 11 is formed by physically depositing aluminum on the entire back surface.

  Thereafter, as shown in FIG. 3 (28), a silver electrode paste containing glass particles is applied to the light receiving surface by screen printing or the like, and a silver electrode paste containing glass particles is applied to the back surface by screen printing or the like. . The silver electrode paste on the light receiving surface is applied in a pattern according to the shape of the light receiving surface electrode shown in FIG. 4, and the silver electrode paste on the back surface is applied in a pattern according to the shape of the back electrode shown in FIG.

After applying the electrode paste to each of the light receiving surface and the back surface, after drying, the light receiving surface and the back surface are both heat-treated (fired) at a temperature of about 450 ° C. to 900 ° C. in the atmosphere, and as shown in FIG. A light receiving surface collecting electrode 8 and a light receiving surface output extraction electrode 9 are formed on the light receiving surface, and a back surface collecting electrode 11 and a back surface output extraction electrode 7 are formed on the back surface, respectively. At this time, the light receiving surface electrode and the n ⁺ -type diffusion layer 2 are electrically connected on the light receiving surface, and the back surface collecting electrode 11 and the back surface output extraction electrode 7 formed by vapor deposition are electrically connected on the back surface. The

<Solar cell>
The solar cell includes the above-described solar cell element and a wiring material provided on the electrode of the solar cell element. FIG. 10 is a diagram for explaining an example of a method for manufacturing a solar cell.
The solar cell includes at least one of the solar cell elements 12 and is configured by arranging the wiring material 13 on the output extraction electrode of the solar cell element. If necessary, the solar cell is formed by connecting a plurality of solar cell elements via a wiring material 13, further sealing with a sealing material 14, and overlapping a glass plate 16 and a back sheet 15. The wiring material and the sealing material are not particularly limited, and can be appropriately selected from those usually used in this field.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<Example 1>
(Preparation of composition 1 for forming a passivation layer)
5.0 g of ethyl cellulose (Nihon Kasei Co., Ltd., ETHOCEL 200 cps, hereinafter sometimes abbreviated as “EC”) as a resin, and terpineol (Nippon Terpene Chemical Co., Ltd., hereinafter abbreviated as “TPO”) as a liquid medium 95.0 g) was mixed and stirred at 150 ° C. for 1 hour to prepare an ethylcellulose solution.
Next, 25.0 g of niobium ethoxide (Wako Pure Chemical Industries, Ltd.) as a compound represented by the general formula (I), and silicon dioxide particles (Nippon Aerosil Co., Ltd., hydrophobic fumed silica “AEROSIL RY 200” as a filler. “The particle diameter (D50%) is 20 nm) 10.0 g, the ethylcellulose solution 30.0 g, and the terpineol 35.0 g were mixed to prepare a composition 1 for forming a passivation layer. Table 1 summarizes the composition and the like.

(Evaluation of storage stability)
The shear viscosity of the composition 1 for forming a passivation layer prepared above was measured immediately after preparation (within 12 hours) and after storage at 25 ° C. for 30 days, respectively. The shear viscosity was measured by attaching a cone plate (diameter 50 mm, cone angle 1 °) to Anton Paar, MCR301, at a temperature of 25 ° C. and a shear rate of 1.0 s ⁻¹ . The shear viscosity at 25 ° C. was 35.6 Pa · s immediately after preparation, and 36.2 Pa · s after storage at 25 ° C. for 30 days.
In the evaluation of storage stability, the change rate of the shear viscosity after storage for 30 days is “A” when the change rate is less than 10%, “B” when the change rate is 10% or more and less than 30%, and “C” when the change rate is 30% or more. ". If evaluation is A and B, it is favorable as the storage stability of the composition for forming a passivation layer. Table 2 shows the values of the shear viscosity immediately after preparation and the evaluation results of storage stability.

(Evaluation of printability)
When evaluating the printability of the composition for forming a passivation layer, a semiconductor substrate having a mirror-shaped single crystal p-type silicon substrate (50 mm square, thickness 625 μm, hereinafter referred to as substrate A), Two types of single crystal p-type silicon substrates (50 mm square, thickness 180 μm, hereinafter referred to as substrate B) on which a texture structure was formed were used.

In the evaluation of printing unevenness, the composition 1 for forming a passivation layer prepared as described above was continuously printed 10 times on each of the substrate A and the substrate B. Visually confirmed that 9 sheets had no printing unevenness.
Here, “A” is the case where printing unevenness is not visually observed during printing is 9 or more out of 10 sheets, “B” is the case of 8 or less and 6 or more, and the case of 5 or less is “ Evaluated as “C”. If evaluation is A and B, it is favorable as printing unevenness of the composition for forming a passivation layer.
The uneven printing refers to a phenomenon in which the thickness of the composition layer varies depending on the location, which is caused when a part of the screen plate is badly separated when the screen plate is separated from the silicon substrate.

In the evaluation of printing bleeding, the prepared composition 1 for forming a passivation layer was printed on the entire surface of the substrate A and the substrate B in a pattern shown in FIG. Here, the dot-shaped opening pattern used in the evaluation has a dot diameter (L _a ) of 368 μm and a dot interval (L _b ) of 0.5 mm.
Then, the board | substrate A and the board | substrate B which provided the composition 1 for passivation layer formation were heated at 150 degreeC for 3 minute (s), and were dried by evaporating a liquid medium. Next, the substrate A and the substrate B were heat-treated (fired) at a temperature of 700 ° C. for 10 minutes, and then allowed to cool at room temperature (25 ° C.).

In the evaluation of printing bleeding, the dot diameter (L _a ) of the dot-shaped opening in the passivation layer formed on the substrate after heat treatment (firing) was measured. In addition, the dot diameter (L _a ) was measured at 10 points, and the average value was calculated. For substrate A, the dot diameter (L _a ) was 348 μm, and for substrate B, it was 340 μm.
Here, when the dot diameter (L _a ) (368 μm) immediately after printing is less than 10%, the decrease rate of the dot diameter (L _a ) after heat treatment (firing) is “A”, 10% or more and less than 30% Were evaluated as “B”, and 30% or more as “C”. If evaluation is A and B, it is favorable as suppression of printing bleeding of the composition for forming a passivation layer.
Note that printing bleeding refers to a phenomenon in which a composition for forming a passivation layer applied on a semiconductor substrate spreads.

(Measurement of effective lifetime)
One of the 10 substrates A to which the passivation layer forming composition 1 prepared by the evaluation of the printing unevenness was applied on the entire surface was heated at 150 ° C. for 3 minutes to evaporate the liquid medium, thereby drying. Next, the semiconductor substrate was heat-treated (baked) at a temperature of 700 ° C. for 10 minutes, and then allowed to cool at room temperature (25 ° C.) to obtain an evaluation substrate.
The heat treatment (firing) was performed using a diffusion furnace (ACCURON CQ-1200, Hitachi Kokusai Electric Inc.) under conditions of a maximum temperature of 700 ° C. and a holding time of 10 minutes in an air atmosphere.
The effective lifetime of the substrate for evaluation obtained above was measured by a reflected microwave photoconductive decay method at room temperature (25 ° C.) using a lifetime measuring device (Nippon Semi-Lab Co., Ltd., WT-2000PVN). In the obtained evaluation substrate, the effective lifetime of the region to which the composition for forming a passivation layer was applied was 380 μs.

(Production of solar cell element)
First, a single crystal p-type semiconductor substrate (125 mm square, thickness 200 μm) was prepared, and texture structures were formed on the light receiving surface and the back surface by alkali etching. Next, in a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen and oxygen, treatment was performed at a temperature of 900 ° C. for 30 minutes to form n ⁺ -type diffusion layers on the light receiving surface, the back surface, and the side surfaces. Thereafter, side etching was performed to remove the side PSG layer and the n ⁺ -type diffusion layer, and the PSG layer on the light-receiving surface and the back surface was removed using an etching solution containing hydrofluoric acid. Further, the back surface was separately etched to remove the n ⁺ -type diffusion layer on the back surface. Thereafter, an antireflection film made of silicon nitride was formed on the n ⁺ -type diffusion layer on the light-receiving surface with a thickness of about 90 nm by PECVD.

Next, the passivation layer forming composition 1 prepared above was applied to the back surface in the pattern of FIGS. 5, 7, and 8, and then dried at a temperature of 150 ° C. for 5 minutes, and a diffusion furnace (ACCURON CQ-1200, The passivation layer 5 was formed by performing a heat treatment (firing) with a maximum temperature of 700 ° C. and a holding time of 10 minutes in the atmosphere using Hitachi Kokusai Electric). 5, 7 and 8, the back surface passivation layer 5 is formed in a pattern in which the p-type semiconductor substrate is exposed in a dot shape except for a portion where the back surface output extraction electrode is formed in a later step. The pattern of the dot-shaped openings has the same shape as that used in the printing bleeding evaluation, the dot diameter (L _a ) is 368 μm, and the dot interval (L _b ) is 0.5 mm.

  Next, a commercially available silver electrode paste (PV-16A, DuPont) was printed on the light receiving surface with the pattern shown in FIG. 4 by screen printing. The electrode pattern is composed of a light receiving surface (output) current collecting electrode 8 having a width of 120 μm and a light receiving surface output extraction electrode 9 having a width of 1.5 mm, and printed so that the thickness after heat treatment (firing) is 20 μm. Conditions (screen plate mesh, printing speed and printing pressure) were adjusted as appropriate. This was heated at a temperature of 150 ° C. for 5 minutes to evaporate the liquid medium, thereby performing a drying treatment.

  On the other hand, a commercially available aluminum electrode paste (PVG-AD-02, PVG Solutions Co., Ltd.) and a commercially available silver electrode paste (PV-505, DuPont Co., Ltd.) are printed on the back surface in the pattern shown in FIG. did. The pattern of the back surface output extraction electrode 7 made of silver electrode paste was constituted by 123 mm × 4 mm.

In addition, the printing conditions (screen plate mesh, printing speed, and printing pressure) of the silver electrode paste were appropriately adjusted so that the thickness of the back surface output extraction electrode 7 after heat treatment (firing) was 20 μm. Moreover, the aluminum electrode paste was printed on the entire surface other than the back surface output extraction electrode 7 to form a back surface current collecting electrode pattern. At this time, the printing conditions of the aluminum electrode paste were appropriately adjusted so that the thickness of the back surface collecting electrode 8 after heat treatment (firing) was 30 μm.
After printing each electrode paste, a heat treatment was performed at a temperature of 150 ° C. for 5 minutes, and the liquid medium was evaporated to perform a drying process.

  Subsequently, heat treatment (firing) was performed using a tunnel furnace (single-line transport W / B tunnel furnace, Noritake Co., Ltd.) under atmospheric conditions at a maximum temperature of 800 ° C. and a holding time of 10 seconds. The solar cell element 1 in which the electrode was formed was produced.

(Production of solar cells)
On the light-receiving surface output extraction electrode 9 and the back surface output extraction electrode 7 of the solar cell element 1 obtained above, a wiring member (soldered rectangular wire for solar cell, product name: SSA-TPS 0.2 × 1.5) (20), specifications in which a Sn-Ag-Cu-based lead-free solder is plated on a copper wire having a thickness of 0.2 mm x a width of 1.5 mm with a maximum thickness of 20 μm per side, Hitachi Metals, Ltd. [(old) Hitachi Cable Co., Ltd.] and using a tab wire connection device (NTS-150-M, Tabbing & Stringing Machine, NPC Corporation) to melt the solder under conditions of a maximum temperature of 250 ° C. and a holding time of 10 seconds. The wiring material was connected to the light receiving surface output extraction electrode 9 and the back surface output extraction electrode 7.

  Then, using a glass plate (white plate tempered glass 3KWE33, Asahi Glass Co., Ltd.), a sealing material (ethylene vinyl acetate; EVA), and a back sheet, as shown in FIG. 10, glass plate 16 / sealing material 14 / wiring material 13 are layered in the order of the solar cell element 12 / sealing material 14 / back sheet 15, and a part of the wiring member is formed by using this multilayer body with a vacuum laminator (LM-50 × 50, NPC Corporation). The solar cell 1 was produced by vacuum lamination at a temperature of 140 ° C. for 5 minutes so as to be exposed.

  Evaluation of the power generation performance of the produced solar cell was performed using pseudo-sunlight (WXS-155S-10, Wacom Electric Co., Ltd.) and a voltage-current (IV) evaluation measuring instrument (IV CURVE TRACER MP-180, This was performed in combination with a measuring device of Eihiro Seiki Co., Ltd.). Jsc (short circuit current), Voc (open voltage), F. F. (Form factor) and η (conversion efficiency) are obtained by measuring in accordance with JIS-C-8913 (2005) and JIS-C-8914 (2005), respectively. The obtained measured value was converted into a relative value with the measured value of the solar cell (solar cell C1) produced in Comparative Example 1 shown later as 100.0.

<Example 2>
22.5 g of tantalum (V) methoxide, 12.5 g of silicon dioxide particles (AEROSIL RY 200, particle diameter (D50%) is 20 nm), 30.0 g of the ethylcellulose solution prepared in Example 1, and 35. of terpineol. A composition 2 for forming a passivation layer was prepared by mixing 0 g.
Thereafter, in the same manner as in Example 1, the storage stability of the passivation layer forming composition 2 was evaluated, the printability (printing unevenness and printing bleeding), and the effective lifetime were measured. Furthermore, the solar cell element 2 and the solar cell 2 were produced in the same manner as in Example 1, and the power generation performance was evaluated.

<Example 3>
16.0 g of niobium ethoxide, 20.0 g of aluminum hydroxide particles (HP-360, Showa Denko KK, particle size (D50%) is 3.2 μm, purity 99.0% by mass), aluminum ethyl acetoacetate di 7.5 g of isopropylate (Kawaken Fine Chemical Co., Ltd., trade name: ALCH), 30.0 g of the ethylcellulose solution prepared in Example 1, and 26.5 g of terpineol were mixed to obtain composition 3 for forming a passivation layer. Prepared.
Thereafter, in the same manner as in Example 1, the storage stability of the passivation layer forming composition 3 was evaluated, the printability (printing unevenness and printing blur) was evaluated, and the effective lifetime was measured. Furthermore, the solar cell element 3 and the solar cell 3 were produced in the same manner as in Example 1, and the power generation performance was evaluated.

<Example 4>
Silicon _(SiO 2) 1.5 parts dioxide, ₍₂ O 3 B) 13.5 parts of boron oxide, bismuth oxide _{(Bi 2} O 3) 83.0 parts of aluminum oxide _{(Al 2} O 3) 1.5 parts, A glass composed of 0.5 part of zinc oxide (ZnO) (hereinafter sometimes abbreviated as “G01”) was prepared. The obtained glass G01 had a softening point of 420 ° C. and a crystallization temperature of over 650 ° C.
By using the obtained glass G01, glass G01 particles having a particle diameter (D50%) of 1.5 μm were obtained. The shape was substantially spherical.

  The glass particle shape was determined by observation using a TM-1000 scanning electron microscope manufactured by Hitachi High-Technologies Corporation. The average particle size of the glass was calculated using a Beckman Coulter, LS 13 320 type laser scattering diffraction particle size distribution analyzer (measurement wavelength: 632 nm). The softening point of the glass was determined from a differential heat (DTA) curve using a Shimadzu Corporation, DTG-60H type differential heat / thermogravimetric measuring device.

A composition for forming a passivation layer by mixing 24.5 g of vanadium (V) oxytriethoxide, 10.5 g of glass G01 particles, 30.0 g of the ethylcellulose solution prepared in Example 1, and 35.0 g of terpineol. 4 was prepared.
Thereafter, in the same manner as in Example 1, the storage stability of the passivation layer forming composition 4 was evaluated, the printability (printing unevenness and printing bleeding), and the effective lifetime were measured. Furthermore, the solar cell element 4 and the solar cell 4 were produced in the same manner as in Example 1, and the power generation performance was evaluated.

<Example 5>
25.0 g of yttrium ethoxide, 10.0 g of aluminum hydroxide particles (particle diameter (D50%) is 3.2 μm), 30.0 g of the ethylcellulose solution prepared in Example 1, and 35.0 g of terpineol were mixed. Thus, a passivation layer forming composition 5 was prepared.
Thereafter, in the same manner as in Example 1, the storage stability of the passivation layer forming composition 5 was evaluated, the printability (printing unevenness and printing blur) was evaluated, and the effective lifetime was measured. Furthermore, the solar cell element 5 and the solar cell 5 were produced in the same manner as in Example 1, and the power generation performance was evaluated.

<Example 6>
14.5 g of hafnium ethoxide, 8.0 g of silicon dioxide particles (AEROSIL RY 200, particle size (D50%) is 20 nm), 12.5 g of aluminum ethyl acetoacetate diisopropylate (ALCH), prepared in Example 1 The composition 6 for forming a passivation layer was prepared by mixing 30.0 g of the ethyl cellulose solution and 35.0 g of terpineol.
Thereafter, in the same manner as in Example 1, the storage stability of the passivation layer forming composition 6 was evaluated, the printability (printing unevenness and printing blur) was evaluated, and the effective lifetime was measured. Furthermore, the solar cell element 6 and the solar cell 6 were produced in the same manner as in Example 1, and the power generation performance was evaluated.

<Example 7>
Silicon dioxide (SiO ₂ ) 49.0 parts, boron oxide (B ₂ O ₃ ) 16.0 parts, aluminum oxide (Al ₂ O ₃ ) 13.5 parts, zinc oxide (ZnO) 8.5 parts, titanium oxide ( A glass composed of TiO ₂ ) 7.5 and calcium oxide (CaO) 5.5 (hereinafter sometimes abbreviated as “G02”) was prepared. The obtained glass G02 had a softening point of 800 ° C. and a crystallization temperature of over 650 ° C.
By using the obtained glass G02, glass G02 particles having a particle diameter (D50%) of 1.5 μm were obtained. The shape of the glass G02 particles was substantially spherical.

20.0 g of niobium ethoxide, 9.5 g of glass G02 particles, 5.5 g of aluminum ethyl acetoacetate diisopropylate (ALCH), 30.0 g of the ethylcellulose solution prepared in Example 1, and 35.0 g of terpineol A composition 7 for forming a passivation layer was prepared by mixing.
Thereafter, in the same manner as in Example 1, the storage stability of the passivation layer forming composition 7 was evaluated, the printability (printing unevenness and printing blur) was evaluated, and the effective lifetime was measured. Furthermore, the solar cell element 7 and the solar cell 7 were produced in the same manner as in Example 1, and the power generation performance was evaluated.

<Example 8>
A composition 8 for forming a passivation layer was prepared by mixing 19.0 g of tantalum methoxide, 16.0 g of glass G01 particles, 30.0 g of the ethylcellulose solution prepared in Example 1, and 35.0 g of terpineol.
Thereafter, in the same manner as in Example 1, the storage stability of the passivation layer forming composition 8 was evaluated, the printability (printing unevenness and printing bleeding), and the effective lifetime were measured. Furthermore, the solar cell element 8 and the solar cell 8 were produced in the same manner as in Example 1, and the power generation performance was evaluated.

<Comparative Example 1>
In forming a passivation layer on a semiconductor substrate, a passivation layer made of aluminum oxide (Al ₂ O ₃ ) was formed using an ALD (Atomic Layer Deposition) method without using a composition for forming a passivation layer.
Specifically, the film forming conditions were adjusted using an atomic layer deposition apparatus so that the Al ₂ O ₃ layer had a thickness of 20 nm. In addition, the thickness of the layer after film formation was measured using the interference type film thickness meter (F20 film thickness measuring system, Filmetrics Co., Ltd.).

  The effective lifetime measurement substrate, the solar cell element C1, and the solar cell C1 were prepared by the above method, and the effective lifetime was measured and the power generation performance of the solar cell C1 was evaluated. In addition, the kind of semiconductor substrate used for each evaluation, the film formation pattern, the light-receiving surface, and the electrode formation method of the back surface are the same as Example 1.

<Comparative example 2>
In the preparation of the composition for forming a passivation layer in Example 1, it is composed of niobium ethoxide, a liquid medium (TPO), and a resin (EC) as shown in Table 1 without using silicon dioxide particles as a filler. A composition C2 for forming a passivation layer was prepared.
Thereafter, in the same manner as in Example 1, the storage stability of the passivation layer forming composition C2, evaluation of printability (print unevenness and print bleeding), and measurement of effective lifetime were performed. Further, a solar cell element C2 and a solar cell C2 were produced in the same manner as in Example 1, and the power generation performance was evaluated.

<Comparative Example 3>
In the preparation of the composition for forming a passivation layer in Example 1, the composition is composed of vanadium ethoxide, a liquid medium (TPO), and a resin (EC) as shown in Table 1 without using silicon dioxide particles as a filler. A composition C3 for forming a passivation layer was prepared.
Thereafter, in the same manner as in Example 1, the storage stability of the passivation layer forming composition C3 was evaluated, the printability (printing unevenness and printing bleeding) was evaluated, and the effective lifetime was measured.

Evaluation results of shear viscosity, storage stability evaluation results, printability evaluation results, lifetime measurement results, and solar cell power generation performance of the compositions for forming a passivation layer implemented in Examples 1 to 8 and Comparative Examples 1 to 3 The results are summarized in Table 2.
It was found that the passivation layer forming compositions prepared in Examples 1 to 8 all had good storage stability and printability.

Moreover, the effective lifetime evaluated in Examples 1-8 and the electric power generation performance of a solar cell are substantially equivalent to what was measured in Comparative Example 1, and by using the composition for forming a passivation layer of the present invention, the ALD method It can be seen that a passivation layer having an excellent passivation effect comparable to that of aluminum oxide (Al ₂ O ₃ ) is formed.

  On the other hand, with respect to Comparative Example 2 and Comparative Example 3, it was found that the storage stability and printability of the composition for forming a passivation layer were significantly lowered. This is due to the fact that no filler is contained in the composition for forming a passivation layer, so that the storage stability is deteriorated by causing phase separation between the liquid medium and a specific metal alkoxide compound in the composition for forming a passivation layer. It is considered that the printability deteriorated due to the decrease in the thixotropy of the composition for forming a passivation layer and the passivation layer.

The power generation performance of the solar cells C2 and C3 produced in Comparative Example 2 and Comparative Example 3 was also significantly lower than that of Comparative Example 1. This above printability deteriorates, i.e. the progression of the bleeding printing, dot-shaped opening in the printed pattern of the passivation layer forming composition (dot diameter L _a is 368Myuemu) is at almost disappeared and will, after step It is considered that when the aluminum electrode paste was printed and heat-treated (fired), the area of the ohmic contact portion formed between the back surface collecting electrode and the semiconductor substrate was greatly reduced.

<Reference Embodiment 1>
The following are the passivation film, the coating material, the solar cell element, and the silicon substrate with the passivation film according to Reference Embodiment 1.

<1> A passivation film used for a solar cell element including aluminum oxide and niobium oxide and having a silicon substrate.

<2> The passivation film according to <1>, wherein a mass ratio (niobium oxide / aluminum oxide) between the niobium oxide and the aluminum oxide is 30/70 to 90/10.

<3> The passivation film according to <1> or <2>, wherein a total content of the niobium oxide and the aluminum oxide is 90% by mass or more.

<4> The passivation film according to any one of <1> to <3>, further including an organic component.

<5> The passivation film according to any one of <1> to <4>, which is a heat-treated product of a coating material containing an aluminum oxide precursor and a niobium oxide precursor.

<6> A coating-type material that includes an aluminum oxide precursor and a niobium oxide precursor and is used to form a passivation film for a solar cell element having a silicon substrate.

<7> A p-type silicon substrate made of single crystal silicon or polycrystalline silicon and having a light receiving surface and a back surface opposite to the light receiving surface;
An n-type impurity diffusion layer formed on the light-receiving surface side of the silicon substrate;
A first electrode formed on the surface of the n-type impurity diffusion layer on the light-receiving surface side of the silicon substrate;
A passivation film comprising aluminum oxide and niobium oxide formed on the back surface of the silicon substrate and having a plurality of openings;
A second electrode forming an electrical connection with the surface on the back side of the silicon substrate through the plurality of openings;
A solar cell element comprising:

<8> A p-type silicon substrate made of single crystal silicon or polycrystalline silicon and having a light receiving surface and a back surface opposite to the light receiving surface;
An n-type impurity diffusion layer formed on the light-receiving surface side of the silicon substrate;
A first electrode formed on the surface of the n-type impurity diffusion layer on the light-receiving surface side of the silicon substrate;
A p-type impurity diffusion layer formed on a part or all of the back side of the silicon substrate and doped with impurities at a higher concentration than the silicon substrate;
A passivation film comprising aluminum oxide and niobium oxide formed on the back surface of the silicon substrate and having a plurality of openings;
A second electrode that forms an electrical connection with the surface of the p-type impurity diffusion layer on the back side of the silicon substrate through the plurality of openings;
A solar cell element comprising:

<9> An n-type silicon substrate made of single crystal silicon or polycrystalline silicon and having a light receiving surface and a back surface opposite to the light receiving surface;
A p-type impurity diffusion layer formed on the light-receiving surface side of the silicon substrate;
A second electrode formed on the back side of the silicon substrate;
A passivation film formed on the light-receiving surface side surface of the silicon substrate and including a plurality of openings and containing aluminum oxide and niobium oxide;
A first electrode formed on the surface of the p-type impurity diffusion layer on the light-receiving surface side of the silicon substrate and forming an electrical connection with the surface on the light-receiving surface side of the silicon substrate through the plurality of openings; ,
A solar cell element comprising:

<10> The solar cell element according to any one of <7> to <9>, wherein the mass ratio of niobium oxide to aluminum oxide (niobium oxide / aluminum oxide) in the passivation film is 30/70 to 90/10.

<11> The solar cell element according to any one of <7> to <10>, wherein a total content of the niobium oxide and the aluminum oxide in the passivation film is 90% by mass or more.

<12> a silicon substrate;
The passivation film according to any one of <1> to <5> provided on the entire surface or a part of the silicon substrate;
A silicon substrate with a passivation film.

  According to the reference embodiment described above, a passivation film having a long silicon carrier lifetime and a negative fixed charge can be realized at a low cost. In addition, a coating type material for realizing the formation of the passivation film can be provided. In addition, a highly efficient solar cell element using the passivation film can be realized at low cost. In addition, a silicon substrate with a passivation film having a long carrier lifetime and a negative fixed charge can be realized at low cost.

  The passivation film of the present embodiment is a passivation film used for a silicon solar cell element, and includes aluminum oxide and niobium oxide.

  In this embodiment mode, the fixed charge amount of the film can be controlled by changing the composition of the passivation film.

  Further, it is more preferable that the mass ratio of niobium oxide and aluminum oxide is 30/70 to 80/20 from the viewpoint that the negative fixed charge can be stabilized. Further, the mass ratio of niobium oxide and aluminum oxide is more preferably 35/65 to 70/30 from the viewpoint that the negative fixed charge can be further stabilized. In addition, it is preferable that the mass ratio of niobium oxide and aluminum oxide is 50/50 to 90/10 from the viewpoint that both improvement of carrier lifetime and negative fixed charge can be achieved.

  The mass ratio of niobium oxide to aluminum oxide in the passivation film is measured by energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), and high frequency inductively coupled plasma mass spectrometry (ICP-MS). be able to. Specific measurement conditions are as follows. Dissolving the passivation film in acid or alkaline aqueous solution, atomizing this solution and introducing it into Ar plasma, measuring the wavelength and intensity by spectroscopically analyzing the light emitted when the excited element returns to the ground state, Element qualification is performed from the obtained wavelength, and quantification is performed from the obtained intensity.

  The total content of niobium oxide and aluminum oxide in the passivation film is preferably 80% by mass or more, and more preferably 90% by mass or more from the viewpoint of maintaining good characteristics. As the components of niobium oxide and aluminum oxide in the passivation film increase, the effect of negative fixed charges increases.

  The total content of niobium oxide and aluminum oxide in the passivation film can be measured by combining thermogravimetric analysis, fluorescent X-ray analysis, ICP-MS, and X-ray absorption spectroscopy. Specific measurement conditions are as follows. The ratio of inorganic components can be calculated by thermogravimetric analysis, the ratio of niobium and aluminum can be calculated by fluorescent X-ray or ICP-MS analysis, and the ratio of oxide can be examined by X-ray absorption spectroscopy.

  Further, the passivation film may contain components other than niobium oxide and aluminum oxide as organic components from the viewpoint of improving the film quality and adjusting the elastic modulus. The presence of the organic component in the passivation film can be confirmed by elemental analysis and measurement of the FT-IR of the film.

  The content of the organic component in the passivation film is more preferably less than 10% by mass, further preferably 5% by mass or less, and particularly preferably 1% by mass or less in the passivation film.

  The passivation film may be obtained as a heat-treated product of a coating type material containing an aluminum oxide precursor and a niobium oxide precursor. Details of the coating type material will be described next.

  The coating material of the present embodiment includes an aluminum oxide precursor and a niobium oxide precursor, and is used for forming a passivation film for a solar cell element having a silicon substrate.

The aluminum oxide precursor can be used without particular limitation as long as it produces aluminum oxide. As the aluminum oxide precursor, it is preferable to use an organic aluminum oxide precursor from the viewpoint of uniformly dispersing aluminum oxide on the silicon substrate and chemically stable. Examples of the organic aluminum oxide precursor include aluminum triisopropoxide (structural formula: Al (OCH (CH ₃ ) ₂ ) ₃ , High Purity Chemical Research Laboratory SYM-AL04, and the like.

The niobium oxide precursor can be used without particular limitation as long as it produces niobium oxide. As the niobium oxide precursor, it is preferable to use an organic niobium oxide precursor from the viewpoint of uniformly dispersing niobium oxide on the silicon substrate and chemically stable. Examples of organic niobium oxide precursors include niobium (V) ethoxide (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21), High Purity Chemical Laboratory Nb-05, etc. be able to.

  A passivation film is formed by forming a coating type material containing an organic niobium oxide precursor and an organic aluminum oxide precursor using a coating method or a printing method, and then removing organic components by a subsequent heat treatment (firing). Can be obtained. Therefore, as a result, a passivation film containing an organic component may be used.

<Structure explanation of solar cell element>
The structure of the solar cell element of the present embodiment will be described with reference to FIGS. 12-15 is sectional drawing which shows the 1st-4th structural example of the solar cell element which used the passivation film for the back surface of this Embodiment.

  As the silicon substrate (crystalline silicon substrate, semiconductor substrate) 101 used in this embodiment mode, either single crystal silicon or polycrystalline silicon may be used. Further, as the silicon substrate 101, either p-type crystalline silicon or n-type crystalline silicon may be used. From the standpoint of exerting the effects of the present embodiment, p-type crystalline silicon is more suitable.

  In the following FIGS. 12 to 15, an example in which p-type single crystal silicon is used as the silicon substrate 101 will be described. Note that single crystal silicon or polycrystalline silicon used for the silicon substrate 101 may be any material, but single crystal silicon or polycrystalline silicon having a resistivity of 0.5 Ω · cm to 10 Ω · cm is preferable.

  As shown in FIG. 12 (first configuration example), an n-type diffusion layer 102 doped with a group V element such as phosphorus on the light-receiving surface side (upper side, first surface in the figure) of a p-type silicon substrate 101. Is formed. A pn junction is formed between the silicon substrate 101 and the diffusion layer 102. On the surface of the diffusion layer 102, a light receiving surface antireflection film 103 such as a silicon nitride (SiN) film, and a first electrode 105 (light receiving surface side electrode, first surface electrode, upper surface electrode) using silver (Ag) or the like. , A light receiving surface electrode) is formed. The light receiving surface antireflection film 103 may also have a function as a light receiving surface passivation film. By using the SiN film, both functions of the light receiving surface antireflection film and the light receiving surface passivation film can be provided.

  Note that the solar cell element of the present embodiment may or may not have the light-receiving surface antireflection film 103. In addition, the light receiving surface of the solar cell element is preferably formed with a concavo-convex structure (texture structure) in order to reduce the reflectance on the surface, but the solar cell element of the present embodiment has a texture structure. It may or may not have.

  On the other hand, a BSF (Back Surface Field) layer 104, which is a layer doped with a group III element such as aluminum or boron, is formed on the back side (lower side, second side, back side in the figure) of the silicon substrate 101. . However, the solar cell element of this embodiment may or may not have the BSF layer 104.

  A second surface made of aluminum or the like is used on the back surface side of the silicon substrate 101 to make contact (electrical connection) with the BSF layer 104 (or the surface on the back surface side of the silicon substrate 101 when the BSF layer 104 is not provided). Electrodes 106 (back side electrode, second side electrode, back side electrode) are formed.

  Further, in FIG. 12 (first configuration example), a contact region (a surface on the back side of the silicon substrate 101 when the BSF layer 104 is not provided) and the second electrode 106 are electrically connected ( A passivation film (passivation layer) 107 containing aluminum oxide and niobium oxide is formed in a portion excluding the opening OA). The passivation film 107 of this embodiment can have a negative fixed charge. With this fixed charge, electrons which are minority carriers among the carriers generated in the silicon substrate 101 by light are bounced back to the surface side. For this reason, a short circuit current increases and it is anticipated that photoelectric conversion efficiency will improve.

  Next, a second configuration example shown in FIG. 13 will be described. In FIG. 12 (first configuration example), the second electrode 106 is formed on the entire surface of the contact region (opening OA) and the passivation film 107. In FIG. The second electrode 106 is formed only in the region (opening OA). The second electrode 106 may be formed only in part on the contact region (opening OA) and the passivation film 107. Even with the solar cell element having the configuration shown in FIG. 13, the same effect as in FIG. 12 (first configuration example) can be obtained.

  Next, a third configuration example shown in FIG. 14 will be described. In the third configuration example shown in FIG. 14, the BSF layer 104 is formed only on a part of the back surface side including the contact region (opening OA portion) with the second electrode 106, and FIG. 12 (first configuration example). Thus, it is not formed on the entire back surface side. Even with the solar cell element having such a configuration (FIG. 14), the same effect as that of FIG. 12 (first configuration example) can be obtained. Further, according to the solar cell element of the third configuration example of FIG. 14, the BSF layer 104, that is, the impurity is doped at a higher concentration than the silicon substrate 101 by doping a group III element such as aluminum or boron. Since there are few areas, it is possible to obtain higher photoelectric conversion efficiency than that in FIG. 12 (first configuration example).

  Next, a fourth configuration example shown in FIG. 15 will be described. In FIG. 14 (third configuration example), the second electrode 106 is formed on the entire surface of the contact region (opening OA) and the passivation film 107, but in FIG. 15 (fourth configuration example), the contact The second electrode 106 is formed only in the region (opening OA). The second electrode 106 may be formed only in part on the contact region (opening OA) and the passivation film 107. Even with the solar cell element having the configuration shown in FIG. 15, the same effect as in FIG. 14 (third configuration example) can be obtained.

  In addition, when the second electrode 106 is applied by a printing method and baked at a high temperature to form the entire surface on the back surface side, a convex warpage tends to occur in the temperature lowering process. Such warpage may cause damage to the solar cell element, which may reduce the yield. Further, the problem of warpage increases as the silicon substrate becomes thinner. The cause of this warp is that stress is generated because the thermal expansion coefficient of the second electrode 106 made of metal (for example, aluminum) is larger than that of the silicon substrate, and the shrinkage in the temperature lowering process is correspondingly large.

  From the above, when the second electrode 106 is not formed on the entire back surface side as shown in FIG. 13 (second configuration example) and FIG. 15 (fourth configuration example), the electrode structure tends to be symmetrical vertically. This is preferable because stress due to the difference in thermal expansion coefficient is not easily generated. However, in that case, it is preferable to provide a separate reflective layer.

<Description of manufacturing method of solar cell element>
Next, an example of a method for manufacturing the solar cell element (FIGS. 12 to 15) of the present embodiment having the above-described configuration will be described. However, the present embodiment is not limited to the solar cell element manufactured by the method described below.

  First, a texture structure is formed on the surface of the silicon substrate 101 shown in FIG. The texture structure may be formed on both sides of the silicon substrate 101 or only on one side (light receiving side). In order to form a texture structure, first, the damaged layer of the silicon substrate 101 is removed by immersing the silicon substrate 101 in a heated potassium hydroxide or sodium hydroxide solution. Then, a texture structure is formed on both surfaces or one surface (light receiving surface side) of the silicon substrate 101 by dipping in a solution containing potassium hydroxide and isopropyl alcohol as main components. Note that, as described above, the solar cell element of the present embodiment may or may not have a texture structure, and thus this step may be omitted.

Subsequently, after the silicon substrate 101 is washed with a solution of hydrochloric acid, hydrofluoric acid, etc., a phosphorus diffusion layer (n ⁺ layer) is formed as the diffusion layer 102 by thermal diffusion of phosphorus oxychloride (POCl ₃ ) or the like on the silicon substrate 101. To do. The phosphorus diffusion layer can be formed, for example, by applying a coating-type doping material solution containing phosphorus to the silicon substrate 101 and performing heat treatment. After the heat treatment, the phosphorous glass layer formed on the surface is removed with an acid such as hydrofluoric acid, whereby a phosphorous diffusion layer (n ⁺ layer) is formed as the diffusion layer 102. The method for forming the phosphorus diffusion layer is not particularly limited. The phosphorus diffusion layer may be formed so that the depth from the surface of the silicon substrate 101 is in the range of 0.2 μm to 0.5 μm, and the sheet resistance is in the range of 40Ω / □ to 100Ω / □ (ohm / square). preferable.

Thereafter, a BSF layer 104 on the back surface side is formed by applying a coating-type doping material solution containing boron, aluminum or the like to the back surface side of the silicon substrate 101 and performing heat treatment. For the application, methods such as screen printing, inkjet, dispensing, spin coating and the like can be used. After the heat treatment, the BSF layer 104 is formed by removing a layer of boron glass, aluminum, or the like formed on the back surface with hydrofluoric acid, hydrochloric acid, or the like. The method for forming the BSF layer 104 is not particularly limited. Preferably, the BSF layer 104 is preferably formed such that the concentration range of boron, aluminum, or the like is 10 ¹⁸ cm ⁻³ to 10 ²² cm ^−3, and the BSF layer 104 is formed in a dot shape or a line shape It is preferable to do. Note that the solar cell element of the present embodiment may or may not have the BSF layer 104, and thus this step may be omitted.

Further, when the diffusion layer 102 on the light-receiving surface and the BSF layer 104 on the back surface are formed using a coating-type doping material solution, the above-described doping material solution is applied to both sides of the silicon substrate 101 to diffuse. The phosphorous diffusion layer (n ⁺ layer) and the BSF layer 104 as the layer 102 may be formed in a lump, and then phosphorous glass, boron glass, or the like formed on the surface may be removed all at once.

  Thereafter, a silicon nitride film as the light-receiving surface antireflection film 103 is formed on the diffusion layer 102. The method for forming the light receiving surface antireflection film 103 is not particularly limited. The light-receiving surface antireflection film 103 is preferably formed to have a thickness in the range of 50 to 100 nm and a refractive index in the range of 1.9 to 2.2. The light-receiving surface antireflection film 103 is not limited to a silicon nitride film, and may be a silicon oxide film, an aluminum oxide film, a titanium oxide film, or the like. The surface antireflection film 103 such as an silicon nitride film can be manufactured by a method such as plasma CVD or thermal CVD, and is preferably manufactured by plasma CVD that can be formed in a temperature range of 350 ° C. to 500 ° C.

  Next, a passivation film 107 is formed on the back side of the silicon substrate 101. The passivation film 107 contains aluminum oxide and niobium oxide. For example, an aluminum oxide precursor typified by an organometallic decomposition coating material from which aluminum oxide can be obtained by heat treatment (firing), and niobium oxide obtained by heat treatment (firing). It is formed by applying a material (passivation material) containing a niobium oxide precursor typified by a commercially available organometallic decomposition coating type material and heat-treating (firing).

  The formation of the passivation film 107 can be performed as follows, for example. The above coating material is spin-coated on one side of a 725 μm thick 8-inch (20.32 cm) p-type silicon substrate (8Ω-12Ωcm) from which a natural oxide film has been previously removed with hydrofluoric acid having a concentration of 0.049% by mass. Then, pre-baking is performed on a hot plate at 120 ° C. for 3 minutes. Thereafter, heat treatment is performed at 650 ° C. for 1 hour in a nitrogen atmosphere. In this case, a passivation film containing aluminum oxide and niobium oxide is obtained. The thickness of the passivation film 107 formed by the above method is usually about several tens of nanometers as measured by an ellipsometer.

  The coating material is applied to a predetermined pattern including the contact region (opening OA) by a method such as screen printing, offset printing, ink jet printing, or dispenser printing. In addition, after apply | coating the said coating type material, after pre-baking in the range of 80 to 180 degreeC and evaporating a solvent, in nitrogen atmosphere or in air, it is 600 to 1000 degreeC, and 30 minutes to 3 hours. It is preferable to perform a degree of heat treatment (annealing) to form a passivation film 107 (oxide film).

  Furthermore, the opening (contact hole) OA is preferably formed on the BSF layer 104 in a dot shape or a line shape.

  As the passivation film 107 used for the above solar cell element, the mass ratio of niobium oxide to aluminum oxide (niobium oxide / aluminum oxide) is preferably 30/70 to 90/10, and 30/70 to 80/20. More preferably, it is more preferably 35/65 to 70/30. Thereby, the negative fixed charge can be stabilized. In addition, it is preferable that the mass ratio of niobium oxide and aluminum oxide is 50/50 to 90/10 from the viewpoint that both improvement of carrier lifetime and negative fixed charge can be achieved.

  Further, in the passivation film 107, the total content of niobium oxide and aluminum oxide is preferably 80% by mass or more, and more preferably 90% by mass or more.

  Next, the first electrode 105 which is an electrode on the light receiving surface side is formed. The first electrode 105 is formed by forming a paste mainly composed of silver (Ag) on the light-receiving surface antireflection film 103 by screen printing and performing a heat treatment (fire through). The shape of the 1st electrode 105 may be arbitrary shapes, for example, may be a known shape which consists of a finger electrode and a bus-bar electrode.

  And the 2nd electrode 106 which is an electrode of the back side is formed. The second electrode 106 can be formed by applying a paste containing aluminum as a main component using screen printing or a dispenser and heat-treating it. The shape of the second electrode 106 is preferably the same shape as the shape of the BSF layer 104, a shape covering the entire back surface, a comb shape, a lattice shape, or the like. The paste for forming the first electrode 105 and the second electrode 106, which are the electrodes on the light receiving surface side, is first printed, and then heat-treated (fire-through), whereby the first electrode 105 and the second electrode 106 are formed. The two electrodes 106 may be formed together.

  Further, by using a paste containing aluminum (Al) as a main component for forming the second electrode 106, aluminum diffuses as a dopant, and the BSF layer 104 is formed in a contact portion between the second electrode 106 and the silicon substrate 101 in a self-alignment manner. Is formed. As described above, the BSF layer 104 may be separately formed by applying a coating-type doping material solution containing boron, aluminum, or the like to the back side of the silicon substrate 101 and heat-treating it. .

  In the above description, a structural example and a manufacturing method example in which p-type silicon is used for the silicon substrate 101 are shown, but an n-type silicon substrate can also be used as the silicon substrate 101. In this case, the diffusion layer 102 is formed by a layer doped with a group III element such as boron, and the BSF layer 104 is formed by doping a group V element such as phosphorus. However, it should be noted that in this case, a leakage current flows through a portion where the inversion layer formed at the interface due to the negative fixed charge and the metal on the back surface are in contact with each other, and the conversion efficiency may be difficult to increase.

  When an n-type silicon substrate is used, a passivation film 107 containing niobium oxide and aluminum oxide can be used on the light receiving surface side as shown in FIG. FIG. 16 is a cross-sectional view illustrating a configuration example of a solar cell element using the light-receiving surface passivation film of the present embodiment.

  In this case, the diffusion layer 102 on the light receiving surface side is p-type doped with boron, and collects holes of the generated carriers on the light receiving surface side and electrons on the back surface side. For this reason, it is preferable that the passivation film 107 having a negative fixed charge is on the light receiving surface side.

  On the passivation film containing niobium oxide and aluminum oxide, an antireflection film made of SiN or the like may be further formed by CVD or the like.

  Hereafter, it demonstrates in detail, referring the reference Example and reference comparative example of this Embodiment.

[Reference Example 1-1]
3.0 g of a commercially available organometallic decomposition coating type material [High Purity Chemical Laboratory, Ltd. SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), and heat treatment A commercially available organometallic decomposition coating-type material [High Purity Chemical Laboratory Nb-05, concentration 5% by mass] from which niobium oxide (Nb ₂ O ₅ ) is obtained by (baking) is mixed with 3.0 g, A passivation material (a-1) which is a coating type material was prepared.

The passivation material (a-1) was spin-coated on one side of a 725 μm-thick 8-inch p-type silicon substrate (8 Ωcm to 12 Ωcm) from which a natural oxide film was previously removed with hydrofluoric acid having a concentration of 0.049% by mass. Pre-baking was performed on the plate at 120 ° C. for 3 minutes. Thereafter, a heat treatment (firing) was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing nitric oxide and niobium oxide [niobium oxide / aluminum oxide = 68/32 (mass ratio)]. It was 43 nm when the film thickness was measured with the ellipsometer. When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition on the passivation film through a metal mask, and a capacitor having a MIS (Metal-Insulator-Semiconductor) structure was produced. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to +0.32 V. From this shift amount, it was found that the passivation film obtained from the passivation material (a-1) showed a negative fixed charge with a fixed charge density (Nf) of −7.4 × 10 ¹¹ cm ⁻² .

  In the same manner as described above, the passivation material (a-1) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 650 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 530 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (a-1) exhibits a certain degree of passivation performance and a negative fixed charge.

[Reference Example 1-2]
As in Reference Example 1-1, a commercially available organometallic decomposition coating material from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) [High Purity Chemical Laboratory, SYM-AL04, concentration 2. 3 mass%] and a commercially available organometallic decomposable coating material from which niobium oxide (Nb ₂ O ₅ ) is obtained by heat treatment (firing) [High Purity Chemical Laboratory, Nb-05, concentration 5 mass%] Then, the materials were mixed at different ratios to prepare passivation materials (a-2) to (a-7) shown in Table 3.

  Similarly to Reference Example 1-1, each of the passivation materials (a-2) to (a-7) was applied to one side of a p-type silicon substrate, and heat treatment (firing) was performed to produce a passivation film. The voltage dependence of the capacitance of the obtained passivation film was measured, and the fixed charge density was calculated therefrom.

  Further, in the same manner as in Reference Example 1-1, the carrier lifetime was measured using a sample obtained by applying a passivation material to both sides of a p-type silicon substrate and performing heat treatment (firing). The results obtained are summarized in Table 3.

  Although the results are different depending on the ratio (mass ratio) of niobium oxide / aluminum oxide after heat treatment (firing), the passivation materials (a-2) to (a-7) also have a carrier lifetime after heat treatment (firing). Since it showed a certain value, it was suggested that it functions as a passivation film. It was found that all of the passivation films obtained from the passivation materials (a-2) to (a-7) stably show negative fixed charges and can be suitably used as a passivation for a p-type silicon substrate. .

[Reference Example 1-3]
3.18 g (0.010 mol) of commercially available niobium (V) ethoxide (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21) and commercially available aluminum triisopropoxide (structural formula: Al ( A passivation material (c-1) having a concentration of 5% by mass was prepared by dissolving 1.02 g (0.005 mol) of OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) in 80 g of cyclohexane.

The passivation material (c-1) is spin-coated on one side of a 725 μm-thick 8-inch p-type silicon substrate (8 Ωcm to 12 Ωcm) from which a natural oxide film has been previously removed with hydrofluoric acid having a concentration of 0.049% by mass. Pre-baking was performed at 120 ° C. for 3 minutes on the plate. Thereafter, heat treatment (baking) was performed at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and niobium oxide. When the film thickness was measured with an ellipsometer, it was 50 nm. As a result of elemental analysis, it was found that Nb / Al / C = 81/14/5 (mass%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition on the passivation film through a metal mask, and a capacitor having a MIS (Metal-Insulator-Semiconductor) structure was produced. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) was shifted from an ideal value of −0.81 V to +4.7 V. From this shift amount, it was found that the passivation film obtained from the passivation material (c-1) had a fixed charge density (Nf) of −3.2 × 10 ¹² cm ⁻² and a negative fixed charge.

  In the same manner as above, the passivation material (c-1) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain silicon. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 330 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (c-1) showed a certain degree of passivation performance and a negative fixed charge.

[Reference Example 1-4]
2.35 g (0.0075 mol) of commercially available niobium (V) ethoxide (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21) and commercially available aluminum triisopropoxide (structural formula: Al ( 1.02 g (0.005 mol) of OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) and 10 g of novolac resin were dissolved in 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to obtain a passivation material (c -2) was prepared.

The passivation material (c-2) is spin-coated on one side of a 725 μm-thick 8-inch p-type silicon substrate (8 Ωcm to 12 Ωcm) from which a natural oxide film has been removed in advance with a hydrofluoric acid having a concentration of 0.049% by mass. Pre-baking was performed at 120 ° C. for 3 minutes on the plate. Thereafter, heat treatment (baking) was performed at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and niobium oxide. When the film thickness was measured by an ellipsometer, it was 14 nm. As a result of elemental analysis, it was found that Nb / Al / C = 75/17/8 (mass%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of 1 mm diameter aluminum electrodes are deposited on the passivation film through a metal mask to form a MIS (Metal-Insulator-Semiconductor) capacitor. did. The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to +0.10 V. From this shift amount, it was found that the passivation film obtained from the passivation material (c-2) showed a negative fixed charge with a fixed charge density (Nf) of −0.8 × 10 ¹¹ cm ⁻² .

  In the same manner as described above, the passivation material (c-2) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (firing) at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain silicon. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute Co., Ltd., RTA-540). As a result, the carrier lifetime was 200 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained from the passivation material (c-2) exhibited a certain degree of passivation performance and a negative fixed charge.

[Reference Example 1-5 and Reference Comparative Example 1-1]
As in Reference Example 1-1, a commercially available organometallic decomposition coating material from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (calcination) [SYM-AL04, Purity Chemical Laboratory Co., Ltd., concentration 2.3]. % By mass] and a commercially available organometallic decomposable coating type material [High Purity Chemical Laboratory Nb-05, concentration 5% by mass] from which niobium oxide (Nb ₂ O ₅ ) can be obtained by heat treatment (firing) The materials were changed and mixed to prepare passivation materials (b-1) to (b-7) shown in Table 4.

  As in Reference Example 1-1, each of the passivation materials (b-1) to (b-7) was applied to one side of a p-type silicon substrate, and heat treatment (firing) was performed to produce a passivation film. Using this, the voltage dependence of the capacitance was measured, and the fixed charge density was calculated therefrom.

  Furthermore, as in Reference Example 1-1, a carrier material was measured using a sample obtained by applying a passivation material (coating material) to both sides of a p-type silicon substrate and curing it. The results obtained are summarized in Table 4.

It was found that the passivation film obtained from the passivation materials (b-1) to (b-6) has a large carrier lifetime and has a function as a passivation. In addition, when the niobium oxide / aluminum oxide ratios were 10/90 and 20/80, the fixed charge density values varied greatly, and a negative fixed charge density could not be stably obtained. It was confirmed that a negative fixed charge density can be realized by using niobium oxide. When measured by the CV method using passivation materials with niobium oxide / aluminum oxide of 10/90 and 20/80, a negative fixed charge is stably generated because a passivation film showing a positive fixed charge is obtained in some cases. It turns out that it has not reached to show. Note that a passivation film exhibiting a fixed charge can be used as a passivation for an n-type silicon substrate.
On the other hand, a negative fixed charge density could not be obtained with the passivation material (b-7) containing 100% by mass of aluminum oxide.

[Reference Comparative Example 1-2]
Commercially available organometallic decomposable coating material that can obtain titanium oxide (TiO ₂ ) by heat treatment (firing) as the passivation material (d-1) [High-Purity Chemical Laboratory Co., Ltd. Ti-03-P, concentration 3 mass%] As a passivation material (d-2), a commercially available organometallic decomposition coating type material [High Purity Chemical Research Institute BT-06, concentration 6 mass%] from which barium titanate (BaTiO ₃ ) is obtained by heat treatment (firing) As a passivation material (d-3), a commercially available organometallic decomposition coating material [High-Purity Chemical Laboratory Co., Ltd., Hf-05, concentration 5 mass%] from which hafnium oxide (HfO ₂ ) is obtained by heat treatment (firing) is used. Got ready.

  As in Reference Example 1-1, each of the passivation materials (d-1) to (d-3) is applied to one side of a p-type silicon substrate, and then heat-treated (fired) to produce a passivation film. Using this, the voltage dependence of the capacitance was measured, and the fixed charge density was calculated therefrom.

  Further, as in Reference Example 1-1, a passivation material was applied to both sides of a p-type silicon substrate, and a carrier lifetime was measured using a sample obtained by heat treatment (firing). The results obtained are summarized in Table 5.

  It was found that the passivation film obtained from the passivation materials (d-1) to (d-3) has a small carrier lifetime and an insufficient function as a passivation. It also showed a positive fixed charge. The passivation film obtained from the passivation material (d-3) had a negative fixed charge, but its value was small. It was also found that the carrier lifetime was relatively small and the function as a passivation was insufficient.

[Reference Example 1-6]
Using a single crystal silicon substrate doped with boron as the silicon substrate 101, a solar cell element having the structure shown in FIG. 14 was manufactured. After the surface of the silicon substrate 101 was textured, a coating type phosphorous diffusion material was applied to the light receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) was formed by heat treatment. Thereafter, the coating type phosphorus diffusing material was removed with dilute hydrofluoric acid.

Next, an SiN film produced by plasma CVD was formed as the light-receiving surface antireflection film 103 on the light-receiving surface side. Thereafter, the passivation material (a-1) prepared in Reference Example 1-1 was applied to the region excluding the contact region (opening OA) on the back surface side of the silicon substrate 101 by an inkjet method. Thereafter, heat treatment was performed to form a passivation film 107 having an opening OA.
In addition, a sample using the passivation material (c-1) prepared in Reference Example 1-3 was separately prepared as the passivation film 107.

  Next, on the light-receiving surface antireflection film 103 (SiN film) formed on the light-receiving surface side of the silicon substrate 101, a paste mainly composed of silver was screen-printed in the shape of predetermined finger electrodes and bus bar electrodes. On the back side, a paste mainly composed of aluminum was screen-printed on the entire surface. Thereafter, heat treatment (fire-through) is performed at 850 ° C. to form electrodes (first electrode 105 and second electrode 106), and aluminum is diffused into the opening OA on the back surface to form the BSF layer 104. Thus, a solar cell element having the structure shown in FIG. 14 was formed.

  In this case, regarding the silver electrode on the light receiving surface, the fire-through process in which the SiN film is not perforated is described, but the opening OA is first formed in the SiN film by etching or the like, and then the silver electrode is formed. You can also.

For comparison, the passivation film 107 is not formed in the above manufacturing process, aluminum paste is printed on the entire back surface, and the p ⁺ layer 114 corresponding to the BSF layer 104 and the electrode 116 corresponding to the second electrode. Was formed on the entire surface to form a solar cell element having the structure shown in FIG. About these solar cell elements, characteristic evaluation (a short circuit current, an open circuit voltage, a fill factor, and conversion efficiency) was performed. Characteristic evaluation was measured based on JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 6.

  From Table 6, the solar cell element having the passivation film 107 including the niobium oxide and aluminum oxide layers has both increased short-circuit current and open-circuit voltage as compared with the solar cell element not having the passivation film 107, and the conversion efficiency ( It was found that the photoelectric conversion efficiency was improved by 1% at the maximum.

<Reference Embodiment 2>
The following are the passivation film, coating material, solar cell element, and silicon substrate with passivation film according to Reference Embodiment 2.

  <1> A passivation film for use in a solar cell element having a silicon substrate, comprising aluminum oxide and at least one oxide of vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide.

  <2> The passivation film according to <1>, wherein a mass ratio of the vanadium group element oxide to the aluminum oxide (vanadium group element oxide / aluminum oxide) is 30/70 to 90/10.

  <3> The passivation film according to <1> or <2>, in which a total content of the oxide of the vanadium group element and the aluminum oxide is 90% or more.

  <4> The oxide of the vanadium group element includes any of oxides of two or three vanadium group elements selected from the group consisting of vanadium oxide, niobium oxide, and tantalum oxide. Any of <1> to <3> The passivation film according to claim 1.

  <5> Heat treatment of a coating-type material comprising: a precursor of aluminum oxide; and a precursor of an oxide of at least one vanadium group element selected from the group consisting of a precursor of vanadium oxide and a precursor of tantalum oxide. The passivation film according to any one of <1> to <4>, which is a product.

  <6> an aluminum oxide precursor, and at least one vanadium group element oxide precursor selected from the group consisting of a vanadium oxide precursor and a tantalum oxide precursor, and having a silicon substrate A coating type material used for forming a passivation film of a solar cell element.

<7> a p-type silicon substrate;
An n-type impurity diffusion layer formed on the first surface side which is the light-receiving surface side of the silicon substrate;
A first electrode formed on the impurity diffusion layer;
A passivation film formed on the second surface side opposite to the light receiving surface side of the silicon substrate and having an opening;
A second electrode formed on the second surface side of the silicon substrate and electrically connected to the second surface side of the silicon substrate through the opening of the passivation film;
The said passivation film is a solar cell element containing aluminum oxide and the oxide of the at least 1 sort (s) of vanadium group element selected from the group which consists of vanadium oxide and a tantalum oxide.

<8> A p-type impurity diffusion layer formed on part or all of the second surface side of the silicon substrate and doped with an impurity at a higher concentration than the silicon substrate,
The solar cell element according to <7>, wherein the second electrode is electrically connected to the p-type impurity diffusion layer through an opening of the passivation film.

<9> an n-type silicon substrate;
A p-type impurity diffusion layer formed on the first surface which is the light-receiving surface side of the silicon substrate;
A first electrode formed on the impurity diffusion layer;
A passivation film formed on the second surface side opposite to the light receiving surface side of the silicon substrate and having an opening;
A second electrode formed on the second surface side of the silicon substrate and electrically connected to the second surface side of the silicon substrate through the opening of the passivation film;
The said passivation film is a solar cell element containing aluminum oxide and the oxide of the at least 1 sort (s) of vanadium group element selected from the group which consists of vanadium oxide and a tantalum oxide.

<10> An n-type impurity diffusion layer formed on a part or all of the second surface side of the silicon substrate and doped with impurities at a higher concentration than the silicon substrate,
The solar cell element according to <9>, wherein the second electrode is electrically connected to the n-type impurity diffusion layer through an opening of the passivation film.

  <11> The solar cell element according to any one of <7> to <10>, wherein a mass ratio of the oxide of the vanadium group element and the aluminum oxide in the passivation film is 30/70 to 90/10. .

  <12> The solar cell element according to any one of <7> to <11>, wherein a total content of the oxide of the vanadium group element and the aluminum oxide in the passivation film is 90% or more.

  <13> The oxide of the vanadium group element includes oxides of two or three vanadium group elements selected from the group consisting of vanadium oxide, niobium oxide, and tantalum oxide, <7> to <12> The solar cell element according to any one of the above.

<14> a silicon substrate;
The passivation film for solar cell elements according to any one of <1> to <5>, provided on the entire surface or a part of the silicon substrate,
A silicon substrate with a passivation film.

  According to the reference embodiment described above, a passivation film having a long silicon carrier lifetime and a negative fixed charge can be realized at a low cost. In addition, a coating type material for realizing the formation of the passivation film can be provided. In addition, a low-cost and highly efficient solar cell element using the passivation film can be realized. In addition, a silicon substrate with a passivation film having a long carrier lifetime and a negative fixed charge can be realized at low cost.

  The passivation film of the present embodiment is a passivation film used for a silicon solar cell element, and includes aluminum oxide and an oxide of at least one vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide. It is what was included.

  In this embodiment mode, the amount of fixed charges included in the passivation film can be controlled by changing the composition of the passivation film. Here, the vanadium group element is a Group 5 element in the periodic table, and is an element selected from vanadium, niobium, and tantalum.

  The mass ratio of the vanadium group element oxide to aluminum oxide is more preferably 35/65 to 90/10, from the viewpoint that the negative fixed charge can be stabilized, and is 50/50 to 90/10. More preferably.

  The mass ratio of vanadium group element oxide and aluminum oxide in the passivation film is determined by energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), and high frequency inductively coupled plasma mass spectrometry (ICP-MS). ) Can be measured. Specific measurement conditions are as follows in the case of ICP-MS, for example. Dissolving the passivation film in acid or alkaline aqueous solution, atomizing this solution and introducing it into Ar plasma, measuring the wavelength and intensity by spectroscopically analyzing the light emitted when the excited element returns to the ground state, Element qualification is performed from the obtained wavelength, and quantification is performed from the obtained intensity.

  The total content of vanadium group oxide and aluminum oxide in the passivation film is preferably 80% by mass or more, and more preferably 90% by mass or more from the viewpoint of maintaining good characteristics. When the components other than the oxide of vanadium group elements and aluminum oxide in the passivation film increase, the effect of negative fixed charges increases.

  Further, in the passivation film, components other than the oxide of vanadium group element and aluminum oxide may be contained as an organic component from the viewpoint of improving the film quality and adjusting the elastic modulus. The presence of the organic component in the passivation film can be confirmed by elemental analysis and measurement of the FT-IR of the film.

As the oxide of the vanadium group element, it is preferable to select vanadium oxide (V ₂ O ₅ ) from the viewpoint of obtaining a larger negative fixed charge.

  The passivation film may include an oxide of a vanadium group element selected from the group consisting of vanadium oxide, niobium oxide, and tantalum oxide as an oxide of a vanadium group element.

  The passivation film is preferably obtained by heat-treating a coating-type material, and can be obtained by forming a coating-type material using a coating method or a printing method, and then removing organic components by heat treatment. More preferred. That is, the passivation film may be obtained as a heat-treated product of a coating type material containing an aluminum oxide precursor and a vanadium group element oxide precursor. Details of the coating type material will be described later.

The coating type material of the present embodiment is a coating type material used for a passivation film for a solar cell element having a silicon substrate, and includes a precursor of aluminum oxide, a precursor of vanadium oxide, and a precursor of tantalum oxide. And a precursor of an oxide of at least one vanadium group element selected from the group. As a precursor of the oxide of the vanadium group element contained in the coating material, a precursor of vanadium oxide (V ₂ O ₅ ) is selected from the viewpoint of the negative fixed charge of the passivation film formed from the coating material. It is preferable. The coating type material is composed of two or three vanadium group elements selected from the group consisting of vanadium oxide precursors, niobium oxide precursors and tantalum oxide precursors as vanadium group oxide precursors. An oxide precursor may also be included.

The aluminum oxide precursor can be used without particular limitation as long as it produces aluminum oxide. As the aluminum oxide precursor, it is preferable to use an organic aluminum oxide precursor from the viewpoint of uniformly dispersing aluminum oxide on the silicon substrate and a chemically stable viewpoint. Examples of the organic aluminum oxide precursor include aluminum triisopropoxide (structural formula: Al (OCH (CH ₃ ) ₂ ) ₃ , Kojundo Chemical Laboratory, SYM-AL04.

  The precursor of the oxide of the vanadium group element can be used without particular limitation as long as it generates an oxide of the vanadium group element. The vanadium group element oxide precursor is preferably an organic vanadium group oxide oxide precursor from the viewpoint of uniformly dispersing aluminum oxide on the silicon substrate and chemically stable. .

Examples of organic vanadium oxide precursors include vanadium (V) oxytriethoxide (structural formula: VO (OC ₂ H ₅ ) ₃ , molecular weight: 202.13), High Purity Chemical Laboratory, V-02 can be mentioned. Examples of organic tantalum oxide precursors include tantalum (V) methoxide (structural formula: Ta (OCH ₃ ) ₅ , molecular weight: 336.12), Kojundo Chemical Laboratory, Ta-10-P Can be mentioned. Examples of organic niobium oxide precursors include niobium (V) ethoxide (structural formula: Nb (OC ₂ H ₅ ) ₅ , molecular weight: 318.21), High Purity Chemical Laboratory, Nb-05. Can be mentioned.

  By forming a coating type material containing an organic vanadium group oxide precursor and an organic aluminum oxide precursor using a coating method or a printing method, and then removing the organic components by a heat treatment, A passivation film can be obtained. Therefore, as a result, a passivation film containing an organic component may be used. The content of the organic component in the passivation film is more preferably less than 10% by mass, still more preferably 5% by mass or less, and particularly preferably 1% by mass or less.

  The solar cell element (photoelectric conversion device) of the present embodiment includes the passivation film (insulating film, protective insulating film) described in the above embodiment in the vicinity of the photoelectric conversion interface of the silicon substrate, that is, aluminum oxide and vanadium oxide. And at least one oxide of a vanadium group element selected from the group consisting of tantalum oxide. By containing aluminum oxide and an oxide of at least one vanadium group element selected from the group consisting of vanadium oxide and tantalum oxide, the carrier lifetime of the silicon substrate can be extended and negative fixed charges can be obtained. And the characteristics (photoelectric conversion efficiency) of the solar cell element can be improved.

  For the description of the structure and manufacturing method of the solar cell element according to the present embodiment, reference can be made to the description of the structure and manufacturing method of the solar cell element according to Reference Embodiment 1.

  Hereafter, it demonstrates in detail, referring the reference Example and reference comparative example of this Embodiment.

<When vanadium oxide is used as the oxide of vanadium group element>
[Reference Example 2-1]
3.0 g of a commercially available organometallic thin film coating type material [High purity chemical research laboratory, SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) And 6.0 g of a commercially available organometallic thin film coating material [Vitamin Purity Laboratory, V-02, concentration 2 mass%] from which vanadium oxide (V ₂ O ₅ ) can be obtained by heat treatment (firing). By mixing, a passivation material (a2-1) which is a coating type material was prepared.

Passivation of passivation material (a2-1) to one side of a 725 μm thick 8-inch p-type silicon substrate (8 Ω · cm to 12 Ω · cm) with natural oxide film removed beforehand with hydrofluoric acid at a concentration of 0.49% by mass It was applied and placed on a hot plate and prebaked at 120 ° C. for 3 minutes. Thereafter, a heat treatment (firing) was performed at 700 ° C. for 30 minutes in a nitrogen atmosphere to obtain a passivation film containing vanadium oxide and vanadium oxide [vanadium oxide / aluminum oxide = 63/37 (mass%)]. It was 51 nm when the film thickness was measured with the ellipsometer. When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a MIS (metal-insulator-semiconductor) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to +0.02 V. From this shift amount, it was found that the passivation film obtained from the passivation material (a2-1) showed a negative fixed charge with a fixed charge density (Nf) of −5.2 × 10 ¹¹ cm ⁻² .

  In the same manner as described above, the passivation material (a2-1) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 650 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured with a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 400 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs. Further, when the carrier lifetime was measured again 14 days after the preparation of the sample, the carrier lifetime was 380 μs. Thereby, it was found that the decrease in carrier lifetime (from 400 μs to 380 μs) was within −10%, and the decrease in carrier lifetime was small.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (a2-1) exhibits a certain degree of passivation performance and a negative fixed charge.

[Reference Example 2-2]
Similar to Reference Example 2-1, a commercially available organometallic thin film coated material from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) [High Purity Chemical Laboratory, SYM-AL04, concentration 2 .3 mass%] and a commercially available organic metal thin film coating type material [Vitamin Purity Laboratory, V-02, concentration 2 mass%] from which vanadium oxide (V ₂ O ₅ ) is obtained by heat treatment, Passivation materials (a2-2) to (a2-7) shown in Table 7 were prepared by changing the ratio.

  As in Reference Example 2-1, each of the passivation materials (a2-2) to (a2-7) was applied to one side of a p-type silicon substrate, and heat treatment (firing) was performed to produce a passivation film. The voltage dependence of the capacitance of the obtained passivation film was measured, and the fixed charge density was calculated therefrom.

  Further, in the same manner as in Reference Example 2-1, the carrier lifetime was measured using a sample obtained by applying a passivation material to both surfaces of a p-type silicon substrate and performing heat treatment (firing).

  The results obtained are summarized in Table 7. Further, when the carrier lifetime was measured again 14 days after the preparation of the sample, the decrease in the carrier lifetime was caused by any of the passivation films using the passivation materials (a2-2) to (a2-7) shown in Table 7. It was within -10%, and it was found that the decrease in carrier lifetime was small.

  Although the results are different depending on the ratio (mass ratio) of vanadium oxide / aluminum oxide after heat treatment (firing), the passivation materials (a2-2) to (a2-7) are all negative after heat treatment (firing). Since it showed a fixed charge and a certain carrier lifetime, it was suggested that it functions as a passivation film. It was found that all the passivation films obtained from the passivation materials (a2-2) to (a2-7) stably show negative fixed charges, and can be suitably used as a passivation for a p-type silicon substrate. .

[Reference Example 2-3]
As a compound for obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (firing), commercially available vanadium (V) oxytriethoxide (structural formula: VO (OC ₂ H ₅ ) ₃ , molecular weight: 202.13) is 1 0.02 g (0.010 mol) and a compound obtained from aluminum oxide (Al ₂ O ₃ ) by heat treatment (calcination), commercially available aluminum triisopropoxide (structure: Al (OCH (CH ₃ ) ₂ ) ₃ , A passivation material (b2-1) having a concentration of 5% by mass was prepared by dissolving 2.04 g (0.010 mol) of molecular weight: 204.25) in 60 g of cyclohexane.

Passivation of passivation material (b2-1) on one side of a 725 μm thick 8-inch p-type silicon substrate (8Ω · cm to 12Ω · cm) from which a natural oxide film was previously removed with hydrofluoric acid having a concentration of 0.49% by mass This was applied and prebaked at 120 ° C. for 3 minutes on a hot plate. Thereafter, a heat treatment (firing) was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and vanadium oxide. When the film thickness was measured with an ellipsometer, it was 60 nm. As a result of elemental analysis, it was found that V / Al / C = 64/33/3 (mass%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a MIS (metal-insulator-semiconductor) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to +0.10 V. From this shift amount, it was found that the passivation film obtained from the passivation material (b2-1) showed a negative fixed charge with a fixed charge density (Nf) of −6.2 × 10 ¹¹ cm ⁻² .

  In the same manner as described above, the passivation material (b2-1) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 400 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (b2-1) exhibited a certain degree of passivation performance and a negative fixed charge.

[Reference Example 2-4]
1.52 g (0.0075 mol) of commercially available vanadium (V) oxytriethoxide (structural formula: VO (OC ₂ H ₅ ) ₃ , molecular weight: 202.13) and commercially available aluminum triisopropoxide (structural formula : Al (OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25), 1.02 g (0.005 mol) and 10 g of novolak resin were dissolved in 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to passivate. Material (b2-2) was prepared.

Passivation of passivation material (b2-2) on one side of a 725 μm thick 8-inch p-type silicon substrate (8 Ω · cm to 12 Ω · cm) with natural oxide film removed beforehand with hydrofluoric acid at a concentration of 0.49% by mass It was applied and placed on a hot plate and prebaked at 120 ° C. for 3 minutes. Thereafter, heating was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and vanadium oxide. When the film thickness was measured with an ellipsometer, it was 22 nm. As a result of elemental analysis, it was found that V / Al / C = 71/22/7 (mass%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a MIS (metal-insulator-semiconductor) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from the ideal value of −0.81 V to +0.03 V. From this shift amount, it was found that the passivation film obtained from the passivation material (b2-2) had a fixed charge density (Nf) of −2.0 × 10 ¹¹ cm ⁻² and a negative fixed charge.

  In the same manner as described above, the passivation material (b2-2) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain silicon. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 170 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by curing the passivation material (b2-2) exhibited a certain degree of passivation performance and a negative fixed charge.

<When tantalum oxide is used as the oxide of vanadium group element>
[Reference Example 2-5]
Commercially available organometallic thin film coating type material [High Purity Chemical Laboratory, SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) and oxidation by heat treatment A commercially available organometallic thin film coating type material [Tapuro Chemical Laboratory Co., Ltd., Ta-10-P, concentration 10% by mass] from which tantalum (Ta ₂ O ₅ ) can be obtained is mixed at different ratios. Passivation materials (c2-1) to (c2-6) shown in Fig. 8 were prepared.

  Each of the passivation materials (c2-1) to (c2-6) is a 725 μm thick 8-inch p-type silicon substrate (8Ω · cm to 12Ω) from which the natural oxide film has been removed in advance with hydrofluoric acid having a concentration of 0.49% by mass. (Cm) was spin-coated on one side, placed on a hot plate, and pre-baked at 120 ° C. for 3 minutes. Thereafter, a heat treatment (firing) was performed at 700 ° C. for 30 minutes in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and tantalum oxide. Using this passivation film, the voltage dependence of the capacitance was measured, and the fixed charge density was calculated therefrom.

  Next, each of the passivation materials (c2-1) to (c2-6) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and heat-treated (fired) at 650 ° C. for 1 hour in a nitrogen atmosphere. ) To prepare a sample in which both surfaces of the silicon substrate were covered with a passivation film. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540).

  The results obtained are summarized in Table 8. Further, when the carrier lifetime was measured again 14 days after the preparation of the sample, the decrease in the carrier lifetime was found in any of the passivation films using the passivation materials (c2-1) to (c2-6) shown in Table 8. It was within -10%, and it was found that the decrease in carrier lifetime was small.

  Although the results differ depending on the ratio (mass ratio) of tantalum oxide / aluminum oxide after heat treatment (firing), the passivation materials (c2-1) to (c2-6) are all negative after heat treatment (firing). Since it showed a fixed charge and a certain carrier lifetime, it was suggested that it functions as a passivation film.

[Reference Example 2-6]
As a compound from which tantalum oxide (Ta ₂ O ₅ ) can be obtained by heat treatment (firing), 1.18 g (0.002) of commercially available tantalum (V) methoxide (structural formula: Ta (OCH ₃ ) ₅ , molecular weight: 336.12) is obtained. As a compound from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), commercially available aluminum triisopropoxide (structural formula: Al (OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25 2.04 g (0.010 mol) was dissolved in 60 g of cyclohexane to prepare a passivation material (d2-1) having a concentration of 5% by mass.

Passivation of passivation material (d2-1) to one side of a 725 μm thick 8-inch p-type silicon substrate (8 Ω · cm to 12 Ω · cm) with natural oxide film removed beforehand with hydrofluoric acid at a concentration of 0.49% by mass It was applied and placed on a hot plate and prebaked at 120 ° C. for 3 minutes. Thereafter, heating was performed at 700 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and tantalum oxide. When the film thickness was measured with an ellipsometer, it was 40 nm. As a result of elemental analysis, it was found that Ta / Al / C = 75/22/3 (wt%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a MIS (metal-insulator-semiconductor) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) was shifted from an ideal value of −0.81 V to −0.30 V. From this shift amount, it was found that the passivation film obtained from the passivation material (d2-1) showed a negative fixed charge at a fixed charge density (Nf) of −6.2 × 10 ¹⁰ cm ⁻² .

  In the same manner as described above, the passivation material (d2-1) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 610 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating the passivation material (d2-1) exhibits a certain degree of passivation performance and a negative fixed charge.

[Reference Example 2-7]
As a compound for obtaining tantalum oxide (Ta ₂ O ₅ ) by heat treatment (firing), 1.18 g (0.005 mol) of commercially available tantalum (V) methoxide (structural formula: Ta (OCH ₃ ) ₅ , molecular weight: 336.12) ) And aluminum oxide (Al ₂ O ₃ ) obtained by heat treatment (firing), a commercially available aluminum triisopropoxide (structure: Al (OCH (CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) 1.02 g (0.005 mol) and 10 g of novolak resin were dissolved in a mixture of 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to prepare a passivation material (d2-2).

Passivation of passivation material (d2-2) on one side of a 725 μm thick 8-inch p-type silicon substrate (8 Ω · cm to 12 Ω · cm) with natural oxide film removed beforehand with hydrofluoric acid at a concentration of 0.49% by mass This was applied and prebaked at 120 ° C. for 3 minutes on a hot plate. Thereafter, heating was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and tantalum oxide. When the film thickness was measured with an ellipsometer, it was 18 nm. As a result of elemental analysis, it was found that Ta / Al / C = 72/20/8 (wt%). When the FT-IR of the passivation film was measured, a peak due to a very few alkyl groups was observed in the vicinity of 1200 cm ⁻¹ .

Next, a plurality of aluminum electrodes having a diameter of 1 mm were formed on the above-described passivation film by vapor deposition through a metal mask, thereby manufacturing a capacitor having a MIS (metal-insulator-semiconductor) structure. . The voltage dependence (CV characteristics) of the capacitance of this capacitor was measured with a commercially available prober and LCR meter (HP, 4275A). As a result, it was found that the flat band voltage (Vfb) shifted from an ideal value of −0.81 V to −0.43 V. From this shift amount, it was found that the passivation film obtained from the passivation material (d-2) had a fixed charge density (Nf) of −5.5 × 10 ¹⁰ cm ⁻² and a negative fixed charge.

  In the same manner as above, the passivation material (d2-2) was applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (baking) at 600 ° C. for 1 hour in a nitrogen atmosphere. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540). As a result, the carrier lifetime was 250 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

  From the above, it was found that the passivation film obtained by heat-treating (sintering) the passivation material (d2-2) exhibited a certain degree of passivation performance and a negative fixed charge.

<When two or more vanadium group element oxides are used>
[Reference Example 2-8]
Commercially available organometallic thin film coating type material that can obtain aluminum oxide (Al ₂ O ₃ ) by heat treatment (firing) [High Purity Chemical Laboratory, SYM-AL04, concentration 2.3 mass%], heat treatment (firing) Commercially available organometallic thin film coating type material (VCO, Co., Ltd., V-02, concentration 2% by mass) from which vanadium oxide (V ₂ O ₅ ) can be obtained by heat treatment, and tantalum oxide (Ta ₂ O ₅ ), a commercially available organometallic thin film coating material [High Purity Chemical Laboratory, Ta-10-P, concentration 10% by mass] is mixed to form a passivation material (e2) that is a coating material. -1) was prepared (see Table 9).

By commercially available organometallic thin film coating type material [Coal Chemical Industries Ltd. SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), heat treatment (firing) Niobium oxide (Nb ₂ O) by commercially available organometallic thin film coating type material (Vitamin Co., Ltd., V-02, concentration 2 mass%) from which vanadium oxide (V ₂ O ₅ ) is obtained, and heat treatment (firing) ₅ ) A commercially available organometallic thin film coating type material [Co., Ltd., High Purity Chemical Laboratory Co., Ltd., Nb-05, concentration 5 mass%] is mixed to obtain a passivation material (e2-2) which is a coating type material. Prepared (see Table 9).

By commercially available organometallic thin film coating type material [Coal Chemical Industries Ltd. SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), heat treatment (firing) Niobium oxide (Nb) by commercially available organometallic thin film coating material [Tapuro Chemical Laboratories Ta-10-P, concentration 10% by mass] from which tantalum oxide (Ta ₂ O ₅ ) can be obtained, and heat treatment (firing) ₂ O ₅ ), a commercially available organometallic thin film coating material [High Purity Chemical Laboratory Nb-05, concentration 5 mass%] is mixed to form a passivation material (e2-3) that is a coating material. Was prepared (see Table 9).

By commercially available organometallic thin film coating type material [Coal Chemical Industries Ltd. SYM-AL04, concentration 2.3 mass%] from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing), heat treatment (firing) Tantalum oxide (Ta ₂ O ₅ ) by commercially available organic metal thin film coating type material [Co., Ltd., Purity Chemical Laboratory V-02, concentration 2 mass%] from which vanadium oxide (V ₂ O ₅ ) is obtained, and heat treatment (firing) Niobium oxide (Nb ₂ O ₅ ) can be obtained by a commercially available organometallic thin film coating type material [High purity chemical research laboratory Ta-10-P, concentration 10% by mass] and heat treatment (firing). Commercially available organic metal thin film coating type material [Co., Ltd. High Purity Chemical Laboratory Nb-05, concentration 5 mass%] was mixed to prepare a passivation material (e2-4) which is a coating type material (see Table 9). ).

  Each of the passivation materials (e2-1) to (e2-4) has a thickness of 725 μm and 8 inches, in which the natural oxide film is previously removed with hydrofluoric acid having a concentration of 0.49% by mass, as in Reference Example 2-1. A p-type silicon substrate (8 Ω · cm to 12 Ω · cm) was spin-coated on one side, placed on a hot plate, and pre-baked at 120 ° C. for 3 minutes. Thereafter, a heat treatment (firing) was performed at 650 ° C. for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and two or more vanadium group element oxides.

  Using the passivation film obtained above, the voltage dependence of the capacitance was measured, and the fixed charge density was calculated therefrom.

  Next, each of the passivation materials (e2-1) to (e2-4) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and heat-treated (fired) at 650 ° C. for 1 hour in a nitrogen atmosphere. ) To prepare a sample in which both surfaces of the silicon substrate were covered with a passivation film. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute, RTA-540).

  The results obtained are summarized in Table 9.

  Passivation using passivation materials (e2-1) to (e2-4), depending on the ratio (mass ratio) of the oxide of two or more vanadium group elements and the aluminum oxide after heat treatment (firing). Regarding the films, all showed negative fixed charges after heat treatment (firing), and the carrier lifetime also showed a certain value, suggesting that it functions as a passivation film.

[Reference Example 2-9]
Similar to Reference Example 2-1, a commercially available organometallic thin film coated material from which aluminum oxide (Al ₂ O ₃ ) can be obtained by heat treatment (firing) [High Purity Chemical Laboratory, SYM-AL04, concentration 2 .3 mass%] and a commercially available organic metal thin film coating type material that can be obtained by heat treatment (firing) vanadium oxide (V ₂ O ₅ ) [High Purity Chemical Laboratory, V-02, concentration 2 mass%] Or a commercially available organic metal thin film coating type material [Tapuro Chemical Laboratory Co., Ltd., Ta-10-P, concentration 10% by mass] from which tantalum oxide (Ta ₂ O ₅ ) can be obtained by heat treatment (firing) is mixed. Then, passivation materials (f2-1) to (f2-8), which are coating-type materials, were prepared (see Table 10).

  Moreover, the passivation material (f2-9) which used aluminum oxide independently was prepared (refer Table 10).

  As in Reference Example 2-1, each of the passivation materials (f2-1) to (f2-9) was applied to one side of a p-type silicon substrate, and then heat treatment (firing) was performed to form a passivation film. This was used to measure the voltage dependence of the capacitance, and the fixed charge density was calculated therefrom.

  Further, as in Reference Example 2-1, samples obtained by applying each of the passivation materials (f2-1) to (f2-9) to both sides of a p-type silicon substrate and heat-treating (firing) were obtained. Used to measure the carrier lifetime. The results obtained are summarized in Table 10.

  As shown in Table 10, when the aluminum oxide / vanadium oxide or tantalum oxide in the passivation material is 90/10 and 80/20, the fixed charge density value varies widely, and the negative fixed charge density is stable. However, it was confirmed that a negative fixed charge density can be realized by using aluminum oxide and niobium oxide. When measured by the CV method using a passivation material in which aluminum oxide / vanadium oxide or tantalum oxide is 90/10 and 80/20, a passivation film showing a positive fixed charge is obtained in some cases. It turns out that it has not reached to show stably. Note that a passivation film exhibiting a positive fixed charge can be used as a passivation film for an n-type silicon substrate. On the other hand, in the passivation material (f2-9) in which aluminum oxide is 100% by mass, a negative fixed charge density could not be obtained.

[Reference Example 2-10]
Using a single crystal silicon substrate with boron as a dopant as the silicon substrate 101, a solar cell element having the structure shown in FIG. 14 was manufactured. After the surface of the silicon substrate 101 was textured, a coating type phosphorous diffusion material was applied only to the light receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) was formed by heat treatment. Thereafter, the coating type phosphorus diffusing material was removed with dilute hydrofluoric acid.

  Next, a SiN film was formed on the light receiving surface side by plasma CVD as the light receiving surface antireflection film 103. Thereafter, the passivation material (a2-1) prepared in Reference Example 2-1 was applied to the region excluding the contact region (opening OA) on the back surface side of the silicon substrate 101 by an inkjet method. Thereafter, heat treatment was performed to form a passivation film 107 having an opening OA. In addition, a sample using the passivation material (c2-1) prepared in Reference Example 2-5 was separately prepared as the passivation film 107.

  Next, on the light-receiving surface antireflection film 103 (SiN film) formed on the light-receiving surface side of the silicon substrate 101, a paste mainly composed of silver was screen-printed in the shape of predetermined finger electrodes and bus bar electrodes. On the back side, a paste mainly composed of aluminum was screen-printed on the entire surface. Thereafter, heat treatment (fire-through) is performed at 850 ° C. to form electrodes (first electrode 105 and second electrode 106), and aluminum is diffused into the opening OA on the back surface to form the BSF layer 104. Thus, a solar cell element having the structure shown in FIG. 14 was formed.

  In this case, regarding the formation of the silver electrode on the light-receiving surface, the fire-through process in which the SiN film is not perforated is described. You can also

For comparison, the passivation film 107 is not formed in the above manufacturing process, aluminum paste is printed on the entire back surface, and the p ⁺ layer 114 corresponding to the BSF layer 104 and the electrode 116 corresponding to the second electrode. Was formed on the entire surface to form a solar cell element having the structure of FIG. About these solar cell elements, characteristic evaluation (a short circuit current, an open circuit voltage, a fill factor, and conversion efficiency) was performed. Characteristic evaluation was measured based on JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 11.

  From Table 11, the solar cell element having the passivation film 107 has both a short-circuit current and an open-circuit voltage that are increased as compared with the solar electronic element not having the passivation film 107, and the conversion efficiency (photoelectric conversion efficiency) is 0 at the maximum. It was found to improve by 6%.

  The disclosures of Japanese Patent Applications Nos. 2012-160336, 2012-218389, 2013-011934, 2013-038895, and 2013-0410153 are incorporated herein by reference in their entirety. All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually stated to be incorporated by reference, Incorporated herein by reference.

In this specification, the term “process” is not limited to an independent process, and is included in this term if the intended purpose of the process is achieved even when it cannot be clearly distinguished from other processes. . Moreover, the numerical range shown using "to" shows the range which includes the numerical value described before and behind "to" as a minimum value and a maximum value, respectively. Furthermore, the content of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. In addition, in the present specification, the term “layer” includes a configuration of a shape formed in part in addition to a configuration of a shape formed on the entire surface when observed as a plan view.

In the general formula (I), each R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms, and preferably 1 to 4 carbon atoms. The alkyl group is more preferable. The alkyl group represented by R ¹ may be linear or branched. Specific examples of the alkyl group represented by R ¹ include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, t-butyl group, hexyl group, octyl group, 2- Examples thereof include an ethylhexyl group and a 3-ethylhexyl group . Specific examples of the aryl group represented by R ¹ include a phenyl group. The alkyl group and aryl group represented by R ¹ may have a substituent. Examples of the substituent for the alkyl group include a halogen atom, an amino group, a hydroxyl group, a carboxyl group, a sulfone group, and a nitro group. Examples of the substituent for the aryl group include a halogen atom, a methyl group, an ethyl group, an isopropyl group, an amino group, a hydroxyl group, a carboxyl group, a sulfone group, and a nitro group.
Among these, R ¹ is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, and more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms, from the viewpoint of storage stability and a passivation effect.

On the other hand, the composition for forming a passivation layer contains a filler, so that the fillers are networked by sintering or the like during heat treatment (firing), function as a protective layer for the semiconductor substrate, and reduce the effective lifetime. It is thought to suppress. The function as a protective layer for the semiconductor substrate is particularly effective for a semiconductor substrate having an uneven structure such as a texture. That is, by forming the network layer derived from the filler, it is considered that the uneven structure portion existing on the surface of the semiconductor substrate can be protected by the passivation layer, and the passivation effect is improved.

Among these resins, from the viewpoint of storage stability and pattern formation, it is preferable to use a neutral resin having no acidic or basic functional group, and even when the content is small, viscosity and from the viewpoint of adjusting the thixotropy, it is more preferable to use a cellulose derivative such as ethyl cellulose scan.

The thickness of the passivation layer formed on the semiconductor substrate is not particularly limited and can be appropriately selected depending on the purpose. For example, the average thickness of the passivation layer is preferably 5 nm to 50 μm, more preferably 10 nm to 30 μm, and still more preferably 15 nm to 20 μm.

Then, as shown in FIG. 1 (6), on the ^{n +} -type diffusion layer 2 of the light-receiving surface, PECVD (Plasma Enhan c ed Chemical Vapor Deposition) method or the like by thickness 90nm of antireflection film 4, such as silicon nitride Provide at the front and back.

In addition, the printing conditions (screen plate mesh, printing speed, and printing pressure) of the silver electrode paste were appropriately adjusted so that the thickness of the back surface output extraction electrode 7 after heat treatment (firing) was 20 μm. Moreover, the aluminum electrode paste was printed on the entire surface other than the back surface output extraction electrode 7 to form a back surface current collecting electrode pattern. At this time, the printing conditions of the aluminum electrode paste were appropriately adjusted so that the thickness of the back surface collecting electrode 11 after heat treatment (firing) was 30 μm.
After printing each electrode paste, a heat treatment was performed at a temperature of 150 ° C. for 5 minutes, and the liquid medium was evaporated to perform a drying process.

<Example 7>
Silicon dioxide (SiO ₂ ) 49.0 parts, boron oxide (B ₂ O ₃ ) 16.0 parts, aluminum oxide (Al ₂ O ₃ ) 13.5 parts, zinc oxide (ZnO) 8.5 parts, titanium oxide ( A glass composed of 7.5 parts of TiO _{2 and} 5.5 parts of calcium oxide (CaO) (hereinafter sometimes abbreviated as “G02”) was prepared. The obtained glass G02 had a softening point of 800 ° C. and a crystallization temperature of over 650 ° C.
By using the obtained glass G02, glass G02 particles having a particle diameter (D50%) of 1.5 μm were obtained. The shape of the glass G02 particles was substantially spherical.

Thereafter, a silicon nitride film as the light-receiving surface antireflection film 103 is formed on the diffusion layer 102. The method for forming the light receiving surface antireflection film 103 is not particularly limited. The light-receiving surface antireflection film 103 is preferably formed to have a thickness in the range of 50 to 100 nm and a refractive index in the range of 1.9 to 2.2. The light-receiving surface antireflection film 103 is not limited to a silicon nitride film, and may be a silicon oxide film, an aluminum oxide film, a titanium oxide film, or the like. Receiving surface antireflection film 103 such as a nitride silicic Motomaku a plasma CVD, can be manufactured by a method such as thermal CVD, it is preferably prepared in a form capable of plasma CVD at a temperature range of 350 ° C. to 500 ° C..

Although the results are different depending on the ratio (mass ratio) of niobium oxide / aluminum oxide after heat treatment (firing), the passivation materials (a-2) to (a-7) also have a carrier lifetime after heat treatment (firing). Since it showed a certain value, it was suggested that it functions as a passivation film. It can be seen that the passivation films obtained from the passivation materials (a-2) to (a-7) all stably show negative fixed charges and can be suitably used as a passivation film for a p-type silicon substrate. It was.

In the same manner as described above, the passivation material (c-2) is applied to both sides of an 8-inch p-type silicon substrate, pre-baked, and subjected to heat treatment (firing) at 600 ° C. for 1 hour in a nitrogen atmosphere to obtain silicon. A sample in which both surfaces of the substrate were covered with a passivation film was produced. The carrier lifetime of this sample was measured by a lifetime measuring device (Kobelco Research Institute , RTA-540). As a result, the carrier lifetime was 200 μs. For comparison, the same 8-inch p-type silicon substrate was measured by passivation using the iodine passivation method, and the carrier lifetime was 1100 μs.

It has been found that the passivation film obtained from the passivation materials (b-1) to (b-6) has a large carrier lifetime and functions as a passivation film . In addition, when the niobium oxide / aluminum oxide ratios were 10/90 and 20/80, the fixed charge density values varied greatly, and a negative fixed charge density could not be stably obtained. It was confirmed that a negative fixed charge density can be realized by using niobium oxide. When measured by the CV method using passivation materials with niobium oxide / aluminum oxide of 10/90 and 20/80, a negative fixed charge is stably generated because a passivation film showing a positive fixed charge is obtained in some cases. It turns out that it has not reached to show. Note that a passivation film exhibiting a fixed charge can be used as a passivation film for an n-type silicon substrate.
On the other hand, a negative fixed charge density could not be obtained with the passivation material (b-7) containing 100% by mass of aluminum oxide.

It has been found that the passivation film obtained from the passivation materials (d-1) to (d-3) has a small carrier lifetime and an insufficient function as a passivation film . It also showed a positive fixed charge. The passivation film obtained from the passivation material (d-3) had a negative fixed charge, but its value was small. It was also found that the carrier lifetime was relatively small and the function as a passivation film was insufficient.

Although the results are different depending on the ratio (mass ratio) of vanadium oxide / aluminum oxide after heat treatment (firing), the passivation materials (a2-2) to (a2-7) are all negative after heat treatment (firing). Since it showed a fixed charge and a certain carrier lifetime, it was suggested that it functions as a passivation film. It can be seen that the passivation films obtained from the passivation materials (a2-2) to (a2-7) all stably show negative fixed charges and can be suitably used as a passivation film for a p-type silicon substrate. It was.

From Table 11, the solar cell element having a passivation layer 107 is different from the solar cells elements having no passivation film 107 has increased short-circuit current and open circuit voltage are both conversion efficiency (photoelectric conversion efficiency) at the maximum It was found to improve by 0.6%.

Claims (13)

A composition for forming a passivation layer, comprising a compound represented by the following general formula (I), a filler, a liquid medium, and a resin.
M (OR ¹ ) _m (I)
[In General Formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y and Hf. R ¹ each independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms. m represents an integer of 1 to 5. ] Furthermore, the composition for passivation layer formation of Claim 1 containing the compound represented with the following general formula (II).

[In General Formula (II), each R ² independently represents an alkyl group having 1 to 8 carbon atoms. n represents an integer of 0 to 3. X ² and X ³ each independently represent an oxygen atom or a methylene group. R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. ]   The said filler contains at least 1 sort (s) of particles selected from the group consisting of silicon dioxide, aluminum hydroxide, aluminum nitride, silicon nitride, aluminum oxide, zirconium oxide, and silicon carbide. A composition for forming a passivation layer.   4. The composition for forming a passivation layer according to claim 1, wherein the filler has a volume average particle diameter of 0.01 μm to 50 μm.   The composition for forming a passivation layer according to any one of claims 1 to 4, wherein the filler comprises glass particles.   The composition for forming a passivation layer according to claim 5, wherein the glass particles have a glass softening point of 300 ° C. to 1000 ° C.   The total content of the compound represented by the general formula (I) and the compound represented by the general formula (II) is 0.1% by mass to 80% by mass, and the content of the filler is 0.1% by mass to The composition for forming a passivation layer according to any one of claims 2 to 6, wherein the total content of 50% by mass and the liquid medium and the resin is 5% by mass to 98% by mass.   The composition for forming a passivation layer according to any one of claims 1 to 7, which is used for forming a passivation layer on a semiconductor substrate.   A passivation layer comprising: a semiconductor substrate; and a passivation layer that is a heat treatment product of the composition for forming a passivation layer according to claim 1, which is provided on the entire surface or a part of the semiconductor substrate. Attached semiconductor substrate.   A step of applying the passivation layer forming composition according to any one of claims 1 to 8 to the entire surface or a part of the semiconductor substrate to form a composition layer, and heat-treating the composition layer And forming a passivation layer, and a method of manufacturing a semiconductor substrate with a passivation layer.   The composition for forming a passivation layer according to any one of claims 1 to 8, which is provided on a semiconductor substrate in which a p-type layer and an n-type layer are pn-junctioned, and on the entire surface or a part of the semiconductor substrate. The solar cell element which has a passivation layer which is the heat processing thing of, and the electrode provided on at least one layer of the said p-type layer and n-type layer.   The composition layer is formed by applying the composition for forming a passivation layer according to any one of claims 1 to 8 to the entire surface or a part of a semiconductor substrate in which a p-type layer and an n-type layer are pn-junctioned. A solar cell element comprising: a step of forming; a step of heat-treating the composition layer to form a passivation layer; and a step of forming an electrode on at least one of the p-type layer and the n-type layer. Manufacturing method. A solar cell element according to claim 11,
A wiring material disposed on the electrode of the solar cell element;
A solar cell having: