JPWO2014014115A1 - Semiconductor substrate with passivation layer and method for manufacturing the same - Google Patents

Abstract

A step of providing a composition for forming a passivation layer containing a compound represented by the following general formula (I) on a semiconductor substrate to form a composition layer, and heat-treating the composition layer at 300 ° C. to 1000 ° C. And forming a passivation layer. A method for manufacturing a semiconductor substrate with a passivation layer. M (OR1) m (I) [wherein M includes at least one metal element selected from the group consisting of Nb, Ta, V, Y and Hf, and each R1 independently has 1 to 8 carbon atoms. An alkyl group or an aryl group having 6 to 14 carbon atoms, and m represents an integer of 1 to 5. ]

Description

  The present invention relates to a semiconductor substrate with a passivation layer and a method for manufacturing the same.

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. Therefore, aluminum powder on the entire back surface, glass frit, an aluminum paste applied containing a dispersion medium and organic binder and the like, by forming an aluminum electrode which heat treatment (firing) to the n-type diffusion layer p ⁺ In addition, an ohmic contact is obtained in the mold diffusion layer.

  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 has a thickness of about 10 μm to 20 μm after the heat treatment. Furthermore, since the thermal expansion coefficients of silicon and aluminum differ greatly, a large internal stress is generated in the silicon substrate during the heat treatment and cooling, which causes damage to crystal boundaries, 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 applied amount of the aluminum paste is reduced, the amount of aluminum diffusing from the surface of the p-type silicon semiconductor substrate 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 side opposite to the light receiving surface (hereinafter also referred to as the back surface), it is necessary to suppress the recombination rate of minority carriers on the surface of the portion other than the aluminum electrode. For this purpose, a SiO ₂ layer or the like has been proposed as a backside semiconductor substrate passivation layer (hereinafter also simply referred to as “passivation layer”) (see, for example, Japanese Patent Application Laid-Open No. 2004-6565). As a passivation effect by forming the SiO ₂ layer, 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 that causes 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 aluminum oxide (Al ₂ O ₃ ) 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 (see, for example, Journal of Applied Physics, 104 (2008), 113703). Further, as a simple method for forming an aluminum oxide layer on a semiconductor substrate, a sol-gel method has been proposed (for example, Thin Solid Films, 517 (2009), 6327-6330 or Chinese Physics Letters, 26 (2009)). , 088102-1 to 088102-4).

  Since the method described in Journal of Applied Physics, 104 (2008), 113703 includes a complicated manufacturing process such as vapor deposition, it may be difficult to improve productivity. In addition, in the composition for forming a passivation layer used in the methods described in Thin Solid Films, 517 (2009), 6327-6330 and Chinese Physics Letters, 26 (2009), 088102-1 to 088102-4, gelation over time, etc. It is difficult to say that the storage stability is sufficient. Further, there has not been sufficiently studied to form a passivation layer having an excellent passivation effect using an oxide containing a metal element other than aluminum.

  This invention is made | formed in view of the above conventional trouble, and makes it a subject to provide the semiconductor substrate which has a passivation layer excellent in the passivation effect, and its simple manufacturing method.

The present invention relates to the following <1> to <5>.
<1> A step of applying a composition for forming a passivation layer containing a compound represented by the following general formula (I) on a semiconductor substrate to form a composition layer, and the composition layer at 300 ° C. to 1000 ° C. And a step of forming a passivation layer by heat treatment with a method of manufacturing a semiconductor substrate with a passivation layer.
M (OR ¹ ) m (I)
In the formula, M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y and Hf, and each R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or 6 to 6 carbon atoms. 14 represents an aryl group, and m represents an integer of 1 to 5.

  <2> The method for producing a semiconductor substrate with a passivation layer according to <1>, wherein the composition for forming a passivation layer further contains a compound represented by the following general formula (II).

Wherein, 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 method for producing a semiconductor substrate with a passivation layer according to <1> or <2>, wherein the composition for forming a passivation layer includes a niobium compound in which M is Nb in the general formula (I).

  <4> The method for producing a semiconductor substrate with a passivation layer according to any one of <1> to <3>, wherein a temperature of the heat treatment is 600 ° C to 800 ° C.

  <5> A semiconductor substrate with a passivation layer obtained by the production method according to any one of <1> to <4>.

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductor substrate which has a passivation layer excellent in the passivation effect, and its simple manufacturing method can be provided.

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 concerning reference embodiment. It is sectional drawing which shows the 2nd structural example of the solar cell element concerning reference embodiment. It is sectional drawing which shows the 3rd structural example of the solar cell element concerning reference embodiment. It is sectional drawing which shows the 4th structural example of the solar cell element concerning reference embodiment. It is sectional drawing which shows another structural example of the solar cell element concerning reference embodiment.

  In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended action of the process is achieved even when it cannot be clearly distinguished from other processes. . In the present specification, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. Further, in the present specification, the content of each component in the composition is 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. Means. 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.

<Method for manufacturing semiconductor substrate with passivation layer>
The method for producing a semiconductor substrate with a passivation layer of the present invention includes a step of forming a composition layer by applying a passivation layer forming composition containing a compound represented by the following general formula (I) on a semiconductor substrate; And heat-treating the composition layer at 300 ° C. to 1000 ° C. to form a passivation layer. The manufacturing method may further include other steps as necessary.
M (OR ¹ ) m (I)
In the formula, M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y and Hf, and each R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or 6 to 6 carbon atoms. 14 represents an aryl group, and m represents an integer of 1 to 5.

  According to the above manufacturing method, a passivation layer having an excellent passivation effect can be formed on the semiconductor substrate. The reason is presumed as follows. That is, a metal oxide obtained by converting a compound represented by the general formula (I) (hereinafter also referred to as a specific organometallic compound) by heat treatment is a compound having a fixed charge. It is considered that the presence of a compound having a fixed charge on the surface of the semiconductor substrate causes band bending and suppresses carrier recombination. Furthermore, the passivation layer comprised from an amorphous metal oxide can be formed by heat-treating on the conditions that the said metal oxide becomes amorphous which does not have a specific crystal structure. If the metal oxide composing the passivation layer is sufficiently amorphous, it is considered that the semiconductor substrate passivation layer can effectively have a fixed charge, and a more excellent passivation effect can be obtained.

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 silicon, germanium and the like doped with p-type impurities or n-type impurities. Of these, a silicon substrate is preferable. 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.

  The thickness of the semiconductor substrate is not particularly limited and can be appropriately selected according to the purpose. For example, it can be set to 50 μm to 1000 μm, and preferably 75 μm to 750 μm.

  The method for producing a semiconductor substrate with a passivation layer preferably further includes a step of applying an alkaline aqueous solution to the semiconductor substrate before the step of forming the composition layer. That is, it is preferable to wash the surface of the semiconductor substrate with an alkaline aqueous solution before applying the passivation layer forming composition onto 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 tends to be 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 organic substance and particles can be removed by immersing the semiconductor substrate in a mixed solution of ammonia water and hydrogen peroxide water and treating the substrate at 60 ° C. to 80 ° C. The treatment time is preferably 10 seconds to 10 minutes, and more preferably 30 seconds to 5 minutes.

  There is no restriction | limiting in particular in the method of providing the said composition for passivation layer formation on a semiconductor substrate, and forming a composition layer. For example, the method of providing the said composition for passivation layer formation on a semiconductor substrate using a well-known coating method etc. can be mentioned. Specific examples include immersion method, printing method, spin method, brush coating, spray method, doctor blade method, roll coater method, and ink jet method. Among these, from the viewpoint of pattern formability, a printing method, an inkjet method and the like are preferable.

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

A passivation layer can be formed on a semiconductor substrate by heat-treating (baking) the composition layer formed by the passivation layer-forming composition to form a heat-treated material layer derived from the composition layer. . In the heat treatment, a specific organometallic compound contained in the composition layer is converted into a metal oxide (M _x O _y ).

In the method for manufacturing a semiconductor substrate with a passivation layer of the present invention, the temperature of the heat treatment is not particularly limited as long as it is in the range of 300 ° C to 1000 ° C. When the temperature of the heat treatment is within a range of 300 ° C. to 1000 ° C., an amorphous M _x O _y layer having no specific crystal structure can be formed. When the temperature of the heat treatment is less than 300 ° C., the organometallic compound tends not to be sufficiently converted into a metal oxide, and when it is higher than 1000 ° C., crystallization tends to proceed excessively.

When the semiconductor substrate passivation layer is composed of an amorphous M _x O _y layer, the semiconductor substrate passivation layer can effectively have a fixed charge, and a more excellent passivation effect can be obtained. From the viewpoint of making the conversion of the organometallic compound into a metal oxide more satisfactory, the heat treatment temperature is preferably 450 ° C. or higher, and more preferably 600 ° C. or higher. From the viewpoint of further suppressing excessive crystallization, the temperature of the heat treatment is preferably 900 ° C. or less, and preferably 800 ° C. or less.
The temperature of heat processing can be made into the range of 600 to 1000 degreeC, for example, and it is preferable to exist in the range of 600 to 800 degreeC. Or the temperature of heat processing can be in the range of 300 to 900 degreeC, for example, and it is preferable to set it in the range of 450 to 800 degreeC.

From the viewpoint of further suppressing excessive crystallization, the heat treatment time is preferably 10 hours or less, more preferably 5 hours or less, and even more preferably less than 3 hours.
The heat treatment time can be, for example, within 10 hours, and is preferably within 5 hours.

  In this specification, the heat treatment time means the length of time during which the temperature of the semiconductor substrate is within the temperature range of the heat treatment. The heat treatment method is not particularly limited, and a general method can be used. For example, it can be performed in an atmospheric composition atmosphere using a firing furnace.

The thickness of the passivation layer manufactured by the method for manufacturing a semiconductor substrate with a passivation layer is not particularly limited and can be appropriately selected according to the purpose. For example, the thickness is preferably 5 nm to 50 μm, preferably 10 nm to 30 μm, and more preferably 15 nm to 20 μm.
The thickness of the passivation layer is measured by a conventional method using a stylus type step / surface shape measuring device (for example, Ambios).

  The method for producing a semiconductor substrate with a passivation layer includes a step of drying the composition layer before the step of heat-treating the composition layer obtained by applying the composition for forming a passivation layer to form the passivation layer. May further be included. By subjecting the composition layer to a drying treatment, a passivation layer having a more uniform passivation effect tends to 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 as necessary. 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.

  A composition for forming a passivation layer containing a specific organometallic compound is applied to a semiconductor substrate to form a composition layer having a desired shape, and this is fired at 300 ° C. to 1000 ° C., thereby providing an excellent passivation effect. The passivation layer can be formed into a desired shape. Since the method of the present invention does not require a vapor deposition apparatus or the like, it is simple and highly productive. Furthermore, the passivation layer can be formed in a desired shape without requiring a complicated process such as mask processing. In addition, since the composition for forming a passivation layer contains a specific organometallic compound, occurrence of problems such as gelation is suppressed, and storage stability with time is excellent.

  In this specification, the passivation effect of a semiconductor substrate is obtained by measuring the effective lifetime of minority carriers in a semiconductor substrate provided with a semiconductor substrate passivation layer by using a lifetime measuring apparatus (Sinton Instruments, WCT-120) or the like. It can be evaluated by measuring by a quasi-steady state photoconductivity method at room temperature (25 ° C.).

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 increases, and as a result, the effective lifetime τ increases. Further, even if defects such as dangling bonds inside 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 of the passivation layer / 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)

  A long effective lifetime indicates a slow recombination rate of minority carriers. 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) (specific organometallic compound). The specific organometallic compound is a compound called a metal alkoxide. The specific organometallic compound becomes a metal oxide (M _x O _y ) by heat treatment.

  The inventors consider the reason why a passivation layer having an excellent passivation effect can be formed by including a specific organometallic compound in the composition for forming a passivation layer as follows. An oxide formed by baking a composition for forming a passivation layer containing a specific organometallic compound tends to be in an amorphous state when heat-treated at 300 ° C to 1000 ° C. When the metal oxide is in an amorphous state, it is considered that a defect of a metal atom or the like is generated and a large fixed charge can be held near the interface with the semiconductor substrate. This large fixed charge generates an electric field in the vicinity of the interface of the substrate, so that the concentration of minority carriers can be reduced, and as a result, the carrier recombination rate at the interface is suppressed, so that the passivation has an excellent passivation effect. It is believed that a layer can be formed.

Note that the fixed charge of the metal oxide can be evaluated by a CV method (Capacitance Voltage Measurement). However, the surface state density of the passivation layer formed from the composition for forming a passivation layer of the present invention may be larger than that of a metal oxide layer formed by ALD or CVD. However, the passivation layer formed from the composition for forming a passivation layer of the present invention has a large electric field effect and a low minority carrier concentration, resulting in an increased surface lifetime τ _s . Therefore, the surface state density is not a relative problem.

  In the general formula (I), M includes at least one metal element selected from the group consisting of Nb, Ta, V, Y, and Hf. M is at least one selected from the group consisting of Nb, Ta, and Y from the viewpoint of the passivation effect, the storage stability of the composition for forming a passivation layer, and the workability in preparing the composition for forming a passivation layer. It is preferable that the metal element is included. Further, from the viewpoint of making the fixed charge density of the passivation layer negative, M preferably contains at least one metal element selected from the group consisting of Nb, Ta, V and Hf, and Nb, Ta, VO and More preferably, it is at least one selected from the group consisting of 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. The alkyl group and aryl group represented by R ¹ may have a substituent. Examples of the substituent of the alkyl group include a halogen element, an amino group, a hydroxyl group, a carboxyl group, a sulfone group, and a nitro group. Can be mentioned. Examples of the substituent for the aryl group include 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 stability, m is preferably 5 when M is Nb, m is preferably 5 when M is Ta, and m is preferably VO when M is VO. 3 is preferable, m is preferably 3 when M is Y, and m is preferably 4 when M is Hf.

As the specific organometallic compound represented by the general formula (I), M includes at least one metal element selected from the group consisting of Nb, Ta and Y, and R ¹ has ¹ to 4 carbon atoms. It is an unsubstituted alkyl group, and m is preferably an integer of 1 to 5.

  The state of the specific organometallic compound may be solid or liquid. The specific organometallic compound is preferably a liquid from the viewpoint of storage stability of the composition for forming a passivation layer and mixing properties when a compound represented by the general formula (II) described later is used in combination.

  Specific organometallic compounds include 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, etc. Among them, niobium ethoxide, niobium n-propoxide, niobium n-butoxide, tantalum ethoxide, tantalum n-propoxide, tantalum n-butoxide, yttrium isopropoxide and yttrium n-butoxide are preferable. 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.

  As the specific organometallic compound, a prepared product or a commercially available product may be used. 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.

  A specific organometallic compound is prepared by reacting a halide of a specific metal (M) with an alcohol in the presence of an inert organic solvent, and further adding ammonia or amines to extract the halogen (special feature). Known manufacturing methods such as Japanese Utility Model Laid-Open No. 63-227593 and Japanese Patent Laid-Open No. 3-291247) can be used.

  The specific organometallic compound may be a compound in which a chelate structure is formed by mixing with a compound having a specific structure having two carbonyl groups described later. When a specific organometallic oxide and a compound having a specific structure having two carbonyl groups are mixed, at least a part of the alkoxide group of the specific organometallic compound is substituted with the compound having the specific structure to form a chelate structure. . At this time, if necessary, a solvent may be present, or heat treatment or addition of a catalyst may be performed. By substituting at least a part of the alkoxide structure with the chelate structure, the stability to hydrolysis, polymerization reaction, etc. of the specific organometallic compound is improved, and the storage stability of the composition for forming a passivation layer containing this is further improved. improves.

  Examples of the compound having a specific structure having the two carbonyl groups include β-diketone compounds, β-ketoester compounds, malonic acid diesters, and the like, from the viewpoint of storage stability, β-diketone compounds, β-ketoester compounds, and malonic acid. It is preferably at least one selected from the group consisting of diesters.

  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, isopropyl acetoacetate, isobutyl acetoacetate, butyl acetoacetate, t-butyl acetoacetate, pentyl acetoacetate, isopentyl acetoacetate, acetoacetic acid Hexyl, n-octyl acetoacetate, heptyl acetoacetate, 3-pentyl acetoacetate, ethyl 2-acetylheptanoate, ethyl 2-methylacetoacetate, ethyl 2-butylacetoacetate, ethyl hexylacetoacetate, 4,4-dimethyl-3- Ethyl oxovalerate, ethyl 4-methyl-3-oxovalerate, ethyl 2-ethylacetoacetate, ethyl hexylacetoacetate, methyl 4-methyl-3-oxovalerate, ethyl 3-oxohexanoate, 3-oxovaleric acid Ethyl, methyl 3-oxovalerate , 3-oxohexanoate methyl, 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 specific organometallic compound has a chelate structure, the number of chelate structures is not particularly limited as long as it is 1 to 5. Among these, from the viewpoint of solubility, the number of chelate structures is preferably 1. The number of chelate structures can be controlled, for example, by appropriately adjusting the ratio of mixing a specific organometallic compound and a compound capable of forming a chelate with a metal element. Moreover, you may select suitably the compound which has a desired structure from a commercially available metal chelate compound.

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

(Compound represented by formula (II))
The composition for forming a passivation layer of the present invention may contain at least one compound represented by the following general formula (II) (hereinafter also referred to as “organoaluminum compound”).

Wherein, 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.

  A passivation effect can be further improved because the composition for forming a passivation layer contains the organoaluminum compound. 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. In addition, Nippon Seramikkusu Kyokai Gakujitsu Ronbunshi, vol. 97, pp. 369-399 (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 organometallic compound having a fixed charge.

  By combining the specific organometallic compound and the organoaluminum compound, it is considered that the passivation effect is further enhanced by the respective effects in the passivation layer. Furthermore, by performing heat treatment (firing) in a state where the specific organometallic compound and the organoaluminum compound are mixed, the composite metal alkoxide of the metal (M) and aluminum (Al) in the specific organometallic compound is used. It is considered that physical properties such as reactivity and vapor pressure are improved, the denseness of the passivation layer as a heat-treated product (baked product) is improved, and as a result, the passivation effect is further enhanced.

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, and ethylhexyl group. Etc. 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 groups represented by R ³ , R ⁴ and R ⁵ are each independently 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. 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 a hydrogen atom or 1 to 4 carbon atoms. It is more preferably an unsubstituted alkyl group.

The organoaluminum compound is preferably 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 and a passivation effect.

From the viewpoints of storage stability and passivation effect, the organoaluminum compound is a compound in which n is 0, R ² is independently an alkyl group having 1 to 4 carbon atoms, and n is 1 to 3, ² is each 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 an alkyl group and at least one selected from the group consisting of compounds in which R ⁵ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

More preferably, the organoaluminum compound is a compound in which n is 0, R ² is each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, and n is 1 to 3, and 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 an alkyl having 1 to ⁴ carbon atoms And when X ² or X ³ is a methylene group, at least one selected from the group consisting of compounds wherein R ³ or R ⁴ bonded to the methylene group is a hydrogen atom and R ⁵ is a hydrogen atom. is there.

  Specific examples of the organoaluminum compound (aluminum trialkoxide) in which n is 0 in the general formula (II) include trimethoxyaluminum, triethoxyaluminum, triisopropoxyaluminum, trisec-butoxyaluminum, monosec-butoxydi Examples thereof include isopropoxyaluminum, tri-t-butoxyaluminum, and tri-n-butoxyaluminum.

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

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

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

  Examples of the compound having a specific structure having the two carbonyl groups include the β-diketone compound, β-ketoester compound, malonic acid diester and the like described above. From the viewpoint of storage stability, the β-diketone compound, β-ketoester compound and It is preferably at least one selected from the group consisting of malonic acid diesters.

  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 is controlled by appropriately adjusting the ratio of mixing the aluminum trialkoxide with a compound capable of forming a chelate with aluminum such as the above-mentioned compound having a specific structure having two carbonyl groups. Can do. Moreover, you may select suitably the compound which has a desired structure from a commercially available aluminum chelate compound.

  The presence of an 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, the homogeneity of the formed passivation layer is further improved by using an organoaluminum compound having good stability at room temperature (25 ° C.) and solubility or dispersibility. 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 in the composition for forming a passivation layer can be appropriately selected as necessary. For example, from the viewpoint of storage stability and a passivation effect, the content of the organoaluminum compound can be 0.1% by mass to 60% by mass in the composition for forming a passivation layer, and 0.5% by mass to 55% by mass. %, More preferably 1% by mass to 50% by mass, and still more preferably 1% by mass to 45% by mass.

  When the composition for forming a passivation layer contains an organoaluminum compound, the organoaluminum when the total content of the specific organometallic compound and the organoaluminum compound (hereinafter also collectively referred to as “organometallic compound”) is 100% by mass. The content of the compound is preferably 0.5% by mass or more and 80% by mass or less, more preferably 1% by mass or more and 75% by mass or less, and further preferably 2% by mass or more and 70% by mass or less. It is particularly preferably 3% by mass or more and 70% by mass or less. By setting the content of the organoaluminum compound to 0.5% by mass or more, the storage stability of the composition for forming a passivation layer tends to be improved. Moreover, it exists in the tendency for the passivation effect to improve by making an organoaluminum compound 80 mass% or less.

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

  The kind of the resin is not particularly limited. Among these, when the composition for forming a passivation layer is applied on a semiconductor substrate, a resin capable of adjusting the viscosity within a range in which a good pattern can be formed is preferable. 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, cellulose derivatives (carboxy Methyl cellulose, hydroxyethyl cellulose, cellulose ethers such as 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 derivatives, dextrin, dextrin derivatives, (me ) Acrylic 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. it can. These resins can be used alone or in combination of two or more.

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.
Further, the molecular weight of these resins 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 100 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 molecular weight distribution measured using GPC (gel permeation chromatography). The calibration curve is approximated by a cubic equation using 5 standard polystyrene sample sets (PStQuick MP-H, PStQuick B [trade name, manufactured by Tosoh Corporation)]. 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

  When the composition for forming a passivation layer contains a resin, 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 composition for forming a passivation layer. From the viewpoint of expressing thixotropy that facilitates pattern formation, the content is more preferably 0.2% by mass to 25% by mass, and more preferably 0.5% by mass to 20% by mass. More preferably, it is more preferably 0.5% by mass to 15% by mass.

  When the composition for forming a passivation layer contains a resin, the content ratio (mass ratio) of the organometallic compound and the resin in the composition for forming a passivation layer can be appropriately selected as necessary. Among these, from the viewpoint of pattern formability and storage stability, the content ratio of the resin to the organometallic compound (resin / organometallic compound) is preferably 0.001 to 1000, and preferably 0.01 to 100. More preferably, it is more preferably 0.1-1.

(Liquid medium)
The composition for forming a passivation layer may contain a liquid medium (solvent or dispersion medium). When the composition for forming a passivation layer contains a liquid medium, the viscosity can be easily adjusted, the impartability is further improved, and a more uniform passivation layer tends to be formed. The liquid medium is not particularly limited and can be appropriately selected as necessary. Among them, a liquid medium capable of obtaining a uniform solution by dissolving the organometallic compound and a resin used as necessary is preferable, and more preferably containing at least one organic solvent. A liquid medium means a medium in a liquid state at room temperature (25 ° C.).

  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, isoamyl acetate, ethyl propionate, n-butyl propionate, isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, lactic acid Ethyl, n-butyl lactate, 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 Ester solvents such as acetate, propylene glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone; Ril, N-methylpyrrolidinone, N-ethylpyrrolidinone, N-propylpyrrolidinone, N-butylpyrrolidinone, N-hexylpyrrolidinone, N-cyclohexylpyrrolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, etc. Aprotic polar solvents; hydrophobic organic solvents such as methylene chloride, chloroform, dichloroethane, benzene, toluene, xylene, hexane, octane, ethylbenzene, 2-ethylhexanoic acid, methyl isobutyl ketone, methyl ethyl ketone; 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-octanol, n- Nonyl alcohol, n-decanol, sec-undecyl alcohol, trimethylnonyl alcohol, sec-tetradecyl alcohol, sec-heptadecyl alcohol, cyclohexanol, methylcyclohexanol, isobornyl cyclohexanol, benzyl alcohol, ethylene glycol, 1, Alcohol solvents such as 2-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, diethylene glycol mono-n-hexyl ether, ethoxytriglycol, tetraethylene glycol mono- Glycol monoether solvents such as n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether; terpinene, terpineol, myrcene, alloocimene, limonene, dipentene, pinene, carvone, Osmen, Terpene solvents such as Erandoren; and water. These liquid media are used alone or in combination of two or more.

  Especially, it is preferable that the said liquid medium contains at least 1 sort (s) chosen from the group which consists of a terpene solvent, an ester solvent, and an alcohol solvent from the viewpoint of the provision property to a semiconductor substrate, and pattern formation property.

  When a liquid medium having a high viscosity and a low boiling point is used among the above liquid media, it is possible to sufficiently maintain the shape of the composition layer when forming the composition layer by applying the passivation layer forming composition to the semiconductor substrate, Since it volatilizes in this heat treatment step, there is an advantage that there is no influence of the residual solvent. Specific examples of the high viscosity low boiling point solvent include isobornyl cyclohexanol.

  When the composition for forming a passivation layer includes a liquid medium, the content of the liquid medium is determined in consideration of the imparting property, the pattern forming property, and the 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%.

(Other ingredients)
The composition for forming a passivation layer of the present invention may contain other components in addition to the components described above. Examples of other components include plasticizers, dispersants, surfactants, thixotropic agents, inorganic fillers, and other metal alkoxide compounds. When forming the passivation layer in a pattern, it is preferable to include at least one selected from a thixotropic agent and an inorganic filler. By including at least one selected from a thixotropic agent and an inorganic filler, the shape stability of the composition layer formed by applying the composition for forming a passivation layer on a semiconductor substrate is further improved, and the passivation layer is It can be formed in a desired shape in the region where the composition layer is formed.

  In the composition for forming a passivation layer, from the viewpoint of storage stability, the content ratios of the acidic compound and the basic compound are each preferably 1% by mass or less in the composition for forming a passivation layer, and 0.1% by mass. % Or less is more preferable.

  Examples of the acidic compound 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. Specific examples include inorganic bases such as alkali metal hydroxides and alkaline earth metal hydroxides, and organic bases such as trialkylamine and pyridine.

The viscosity of the composition for forming a passivation layer is not particularly limited, and can be appropriately selected according to a method for applying to the semiconductor substrate. For example, it can be set to 0.01 Pa · s to 10,000 Pa · s. Among these, from the viewpoint of pattern formability, it 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.

Further, the shear viscosity of the composition for forming a passivation layer is not particularly limited. Among them from the viewpoints of pattern formability, thixotropic ratio calculated by dividing the shear viscosity eta ₁ at shear viscosity eta ₂ at a shear rate of ^{10s -1} at a shear rate of ^{_{1.0s -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 °).

There is no restriction | limiting in particular in the manufacturing method of the said composition for passivation layer formation. For example, it can be produced by mixing an organometallic compound and a resin, a liquid medium, or the like contained as necessary by a commonly used mixing method. Moreover, after dissolving resin in a solvent and obtaining a solution, you may manufacture by mixing the said solution and an organometallic compound.
Further, the organometallic compound may be prepared by mixing a metal alkoxide contained in the organometallic compound and a compound capable of forming a chelate with the metal. At that time, a solvent may be used as necessary, and heat treatment may be performed. The composition for forming a passivation layer may be produced by mixing the organometallic compound thus prepared and a resin or a solution containing a resin.
In addition, content of each component contained in the said composition for formation of a passivation layer is thermal analysis, such as a thermal-thermogravimetric simultaneous measurement (TG / DTA), nuclear magnetic resonance (NMR), and infrared spectroscopy (IR). Etc., and chromatographic analysis such as high performance liquid chromatography (HPLC) and gel permeation chromatography (GPC).

<Semiconductor substrate with passivation layer>
The semiconductor substrate with a passivation layer of the present invention includes a step of providing a passivation layer forming composition containing a specific organometallic compound represented by the general formula (I) on a semiconductor substrate to form a composition layer, A semiconductor substrate with a passivation layer obtained by a method for producing a semiconductor substrate with a passivation layer, comprising: a step of heat-treating the composition layer at 300 ° C. to 1000 ° C. to form a passivation layer.
That is, the semiconductor substrate with a passivation layer of the present invention is provided with a composition for forming a passivation layer containing the semiconductor substrate and the specific organometallic compound represented by the general formula (I) on the entire surface or a part of the semiconductor substrate. And a passivation layer that is a heat-treated product layer (baked product layer) obtained by heat-treating the composition layer formed at 300 ° C. to 1000 ° C. The metal oxide (M _x O _y ) derived from the specific organometallic compound in the passivation layer is sufficiently amorphous. Therefore, the semiconductor substrate with a passivation layer of the present invention exhibits an excellent passivation effect.

  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, the solar cell element excellent in conversion efficiency can be obtained by applying to a solar cell element.

<Solar cell element>
The solar cell element of the present invention provides a semiconductor substrate in which a p-type layer and an n-type layer are pn-junction, and a passivation layer forming composition containing a specific organometallic compound on the entire surface or a part of the semiconductor substrate. And a passivation layer obtained by heat-treating the composition layer formed at 300 ° C. to 1000 ° C., and an electrode disposed 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.
The solar cell element has a passivation layer in which a metal oxide (M _x O _y ) derived from a specific organometallic compound is sufficiently amorphous. Therefore, the solar cell element of the present invention exhibits excellent conversion efficiency.

  The semiconductor substrate is not particularly limited, and for example, the semiconductor substrate described in the method for manufacturing a semiconductor substrate with a passivation layer of the present invention can be used. The surface of the semiconductor substrate on which the passivation layer is provided is preferably a surface where the p-type layer in the solar cell element is present from the viewpoint of conversion efficiency. The thickness of the 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. There is no restriction | limiting in the shape and magnitude | size of the said solar cell element. For example, it is preferable that one side is a substantially square of 125 mm to 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 at 300 ° C. to 1000 ° C. 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 And having. The method for manufacturing the solar cell element may further include other steps as necessary.

<Solar cell>
The solar cell of the present invention includes at least one of the solar cell elements, and is configured by arranging a wiring material on an output extraction electrode of the solar cell element. The solar cell is configured by connecting a plurality of solar cell elements via a wiring material and further sealing with a sealing material as necessary. The wiring material and the sealing material are not particularly limited, and can be appropriately selected from those usually used in the technical field.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” is based on mass.

<Example 1>
(Preparation of a composition for forming a passivation layer)
1.00 g of niobium ethoxide (made by Hokuko Chemical Co., Ltd.), 1.00 g of aluminum ethyl acetoacetate diisopropylate (made by Kawaken Fine Chemical Co., Ltd.), and 18.02 g of isopropanol (made by Wako Pure Chemical Industries, Ltd.) By mixing, a composition 1 for forming a passivation layer was prepared. The contents of niobium ethoxide, (ethylacetoacetate) aluminum isopropoxide, and isopropanol were 5.0%, 5.0%, and 90.0%, respectively.

(Formation of passivation layer)
As the semiconductor substrate, a single crystal p-type silicon substrate (manufactured by SUMCO, 50 mm square, thickness: 770 μm) having a mirror shape was used. The composition 1 for forming a semiconductor substrate passivation layer obtained above was applied to the entire one surface of a silicon substrate by a spin coating method to form a composition layer. Thereafter, the silicon substrate on which the composition layer was formed was dried at 150 ° C. for 5 minutes. Next, the substrate was subjected to heat treatment at 700 ° C. for 10 minutes and allowed to cool at room temperature to produce an evaluation substrate having a passivation layer.

(Measurement of effective lifetime)
The effective lifetime (μs) of the evaluation substrate obtained above was measured by a quasi-steady state photoconductivity method at room temperature (25 ° C.) using a lifetime measuring device (WCT-120, manufactured by Sinton Instruments). did. The effective lifetime of the obtained evaluation substrate was 1765 μs.

<Example 2>
A substrate for evaluation was prepared in the same manner as in Example 1 except that the temperature of the heat treatment was 600 ° C., and the effective lifetime was measured in the same manner as in Example 1. The effective lifetime was 573 μs.

<Example 3>
An evaluation substrate was produced in the same manner as in Example 1 except that the temperature of the heat treatment was 800 ° C., and the effective lifetime was measured in the same manner as in Example 1. The effective lifetime was 713 μs.

<Comparative Example 1>
An evaluation substrate was prepared in the same manner as in Example 1 except that the passivation layer was not formed on the silicon substrate, and the effective lifetime was measured. The effective lifetime was 20 μs.

<Comparative example 2>
An evaluation substrate was produced in the same manner as in Example 1 except that the temperature of the heat treatment was 200 ° C., and the effective lifetime was measured in the same manner as in Example 1. The effective lifetime was 22 μs.

  From the above, the evaluation substrate having a passivation layer formed by heat-treating a composition for forming a passivation layer containing a specific organometallic compound at 300 ° C. to 1000 ° C. has a long effective lifetime and exhibits an excellent passivation effect. I understand. This is presumably because the metal oxide contained in the passivation layer is sufficiently amorphous. Moreover, according to the manufacturing method of this invention, a passivation layer can be formed in a desired shape by a simple process.

<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 according to the present embodiment will be described with reference to FIGS. 2-5 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.

  2 to 5 below, 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. 2 (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. 2 (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. 3 will be described. In FIG. 2 (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. 3, the same effect as that of FIG. 2 (first configuration example) can be obtained.

  Next, a third configuration example shown in FIG. 4 will be described. In the third configuration example shown in FIG. 4, 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. 2 (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. 4), the same effect as that of FIG. 2 (first configuration example) can be obtained. Further, according to the solar cell element of the third configuration example of FIG. 4, 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 the area is small, it is possible to obtain higher photoelectric conversion efficiency than that in FIG. 2 (first configuration example).

  Next, a fourth configuration example shown in FIG. 5 will be described. In FIG. 4 (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. 5 (fourth configuration example), the contact is formed. 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. 5, the same effect as that of FIG. 4 (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. 3 (second configuration example) and FIG. 5 (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 unlikely to occur. 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. 2 to 5) 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. 6 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 2.

  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 2.

  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 material was changed and mixed to prepare passivation materials (b-1) to (b-7) shown in Table 3.

  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 3.

  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 4.

  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. 4 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. 4 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 5.

  From Table 5, 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 6 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 6. 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 (a2-2) to (a2-7) shown in Table 6. 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. The passivation materials (c2-1) to (c2-6) shown in 7 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 7. Further, when the carrier lifetime was measured again 14 days after the preparation of the sample, the decrease in the carrier lifetime was any of the passivation films using the passivation materials (c2-1) to (c2-6) shown in Table 7. 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 8).

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 8).

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 8).

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 8). ).

  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 8.

  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 9).

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

  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 9.

  As shown in Table 9, when the aluminum oxide / vanadium oxide or tantalum oxide in the passivation material is 90/10 and 80/20, the fixed charge density varies greatly, 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. 4 was produced. 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. 4 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 10.

  From Table 10, the solar cell element having the passivation film 107 has both the short-circuit current and the open-circuit voltage increased as compared with the solar electronic element not having the passivation film 107, and the conversion efficiency (photoelectric conversion efficiency) is 0 at maximum. It was found to improve by 6%.

  The disclosures of Japanese Patent Application Nos. 2012-160336, 2012-218389, 2013-011934, 2013-0410153, and 2013-103573 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.

There is no restriction | limiting in particular in the method of providing the said composition for passivation layer formation on a semiconductor substrate, and forming a composition layer. For example, the method of providing the said composition for passivation layer formation on a semiconductor substrate using a well-known coating method etc. can be mentioned. Specifically, a dipping method, a printing method, a spin coating method, brush coating, spraying, doctor blade method, Roruko method, a jet method, or the like. Among these, from the viewpoint of pattern formability, a printing method, an inkjet method and the like are preferable.

The thickness of the passivation layer manufactured by the method for manufacturing a semiconductor substrate with a passivation layer is not particularly limited and can be appropriately selected according to the purpose. For example, the thickness is preferably 5 nm to 50 μm, more preferably 10 nm to 30 μm, and further preferably 15 nm to 20 μm.
The thickness of the passivation layer is measured by a conventional method using a stylus type step / surface shape measuring device (for example, Ambios).

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

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. In addition, Nippon Seramikkusu Kyokai Gakuj u tsu Ronbunshi , vol. 97, pp. 369-399 (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 organometallic compound having a fixed charge.

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. Nitride silicic Motomaku such surface reflection preventing film 103 of 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 apparatus (Kobelco Research Institute , Inc. , 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.

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. In FIG. 1, reference numeral 111 denotes a silicon substrate, reference numeral 112 denotes a diffusion layer, reference numeral 113 denotes a light-receiving surface antireflection film, and reference numeral 115 denotes a first electrode. 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 5.

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 10, 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 (5)

A step of providing a composition for forming a passivation layer containing a compound represented by the following general formula (I) on a semiconductor substrate to form a composition layer, and heat-treating the composition layer at 300 ° C. to 1000 ° C. And forming a passivation layer. A method for manufacturing a semiconductor substrate with a passivation layer.
M (OR ¹ ) m (I)
[Wherein, M includes at least one metal element selected from the group consisting of Nb, Ta, V, Y and Hf, and each R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or 6 carbon atoms. Represents an aryl group of -14, and m represents an integer of 1-5. ] The method for producing a semiconductor substrate with a passivation layer according to claim 1, wherein the composition for forming a passivation layer further contains a compound represented by the following general formula (II).



Wherein, 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. ]   The method for producing a semiconductor substrate with a passivation layer according to claim 1, wherein the composition for forming a passivation layer contains a niobium compound in which M is Nb in the general formula (I).   The manufacturing method of the semiconductor substrate with a passivation layer according to any one of claims 1 to 3, wherein a temperature of the heat treatment is 600 ° C to 800 ° C.   The semiconductor substrate with a passivation layer obtained by the manufacturing method as described in any one of Claims 1-4.