TW201410694A - Semiconductor substrate having passivation layer and production method thereof - Google Patents

Abstract

A method of producing a semiconductor substrate having a passivation layer, the method comprising forming a composition layer by applying, onto a semiconductor substrate, a composition for forming a passivation layer, the composition comprising a compound represented by following Formula (I), and subjecting the composition layer to a thermal treatment at a temperature of from 300 DEG C to 1000 DEG C: M(OR1)m (I) wherein in Formula (I), M comprises at least one metal element selected from the group consisting of Nb, Ta, V, Y and Hf; each of R1 independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms; and n is an integer of 1 to 5.

Description

Semiconductor substrate with passivation layer and method of manufacturing same

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

The manufacturing steps of the conventional tantalum solar cell element will be described.

First, in order to promote the light-blocking effect and achieve high efficiency, a p-type germanium substrate having a textured structure formed on the light-receiving surface side is prepared, followed by a mixed gas atmosphere of phosphorus oxychloride (POCl ₃ ), nitrogen, and oxygen. The treatment was carried out at 800 ° C to 900 ° C for several tens of minutes to uniformly form an n-type diffusion layer. In this conventional method, since phosphorus is diffused by using a mixed gas, an n-type diffusion layer is formed not only on the surface as the light-receiving surface but also on the side surface and the back surface. Therefore, side etching for removing the n-type diffusion layer formed on the side surface is performed. In addition, the n-type diffusion layer formed on the back surface must be converted into a p ⁺ -type diffusion layer. Therefore, an aluminum paste containing aluminum powder, glass frit, a dispersion medium, an organic binder, or the like is applied to the entire back surface, and heat-treated (calcined) to form an aluminum electrode, thereby adjusting the n-type diffusion layer. It is a p ⁺ type diffusion layer, and an ohmic contact is obtained.

However, the aluminum electrode formed of the aluminum paste has a low electrical conductivity. Therefore, in order to reduce the sheet resistance, the aluminum electrode which is usually formed on the entire back surface must have a thickness of about 10 μm to 20 μm after the heat treatment. Further, since the thermal expansion coefficients of bismuth and aluminum differ greatly, large internal stresses are generated in the ruthenium substrate during heat treatment and cooling, resulting in damage of grain boundaries, growth of crystal defects, and warpage.

In order to solve this problem, there is a method of reducing the amount of the aluminum paste applied and making the thickness of the back electrode layer thin. However, when the amount of the aluminum paste applied is reduced, the amount of aluminum diffused from the surface of the p-type germanium semiconductor substrate to the inside becomes insufficient. As a result, there is a problem that the desired back surface field (BSF) effect (the effect of increasing the collection efficiency of the carrier by the presence of the p ⁺ -type diffusion layer) cannot be achieved, so that the characteristics of the solar cell are lowered.

In the above, a point contact method is proposed in which an aluminum paste is applied to a part of the surface of the substrate, and a p ⁺ -type diffusion layer and an aluminum electrode are partially formed (for example, refer to Japanese Patent No. 3107287). .

In the case of such 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 speed of the minority carrier in the surface of the portion other than the aluminum electrode. An SiO ₂ layer or the like has been proposed as a passivation layer for a semiconductor substrate (hereinafter also referred to simply as a "passivation layer") for the purpose of this purpose (for example, refer to Japanese Laid-Open Patent Publication No. 2004-6565). As a passivation effect obtained by forming the SiO ₂ layer, there is an effect that the unbonded bond of the germanium atoms in the surface layer portion of the back surface of the tantalum substrate is lowered, and the surface energy density of the recombination is lowered.

Further, as another method of suppressing recombination of minority carriers, there is a method of reducing the density of minority carriers by an electric field generated by a fixed charge in the passivation layer. Such a passivation effect is generally called an electric field effect, and as a material having a negative fixed charge, alumina (Al ₂ O ₃ ) or the like has been proposed (for example, refer to Japanese Patent No. 4767110).

Such a passivation layer is usually formed by an atomic layer deposition (ALD) method or a chemical vapor deposition (CVD) method (for example, refer to the Journal of Applied Physics, 104 (2008), 113703). Further, as a simple method for forming an aluminum oxide layer on a semiconductor substrate, a method using a sol-gel method has been proposed (for example, refer to "Thin Solid Films", 517 (2009), 6327-6330 or "China" Chinese Physics Letters, 26 (2009), 088102-1~088102-4).

The methods described in Journal of Applied Physics, 104 (2008) and 113703 include complicated manufacturing steps such as vapor deposition, and thus it is sometimes difficult to improve productivity. In addition, it is used in the methods described in "Thin Solid Films", 517 (2009), 6327-6330, and "Chinese Physics Letters", 26 (2009), 088102-1 to 088102-4. The composition for forming a passivation layer causes a problem such as gelation over time, and it is difficult to say that the storage stability is sufficient. Further, studies on the use of an oxide containing a metal element other than aluminum to form a passivation layer having an excellent passivation effect have not been sufficiently hitherto.

The present invention has been made in view of the above conventional problems, and an object thereof is to provide a A semiconductor substrate having a passivation layer excellent in passivation effect, and a simple manufacturing method thereof.

The present invention relates to the following <1> to <5>.

<1> A method for producing a semiconductor substrate with a passivation layer, comprising the steps of: providing a composition for forming a passivation layer containing a compound represented by the following formula (I) on a semiconductor substrate to form a composition layer; And a step of heat-treating the composition layer at 300 ° C to 1000 ° C to form a passivation layer; M (OR ¹ ) _m (I)

Wherein M comprises at least one metal element selected from the group consisting of niobium (Nb), tantalum (Ta), vanadium (V), yttrium (Y), and hafnium (Hf), and R ¹ independently represents carbon An alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, and m is an integer of 1 to 5.

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

In the formula, R ² each independently represents an alkyl group having 1 to 8 carbon atoms; n represents an integer of 0 to 3; and X ² and X ³ each independently represent an oxygen atom or a methylene group; and R ³ , R ⁴ and R ⁵ Each independently represents 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 the above aspect, wherein the composition for forming a passivation layer contains a ruthenium compound in which M is Nb in the above formula (I).

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

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

According to the present invention, it is possible to provide a semiconductor substrate having a passivation layer excellent in passivation effect, and a simple manufacturing method therefor.

101, 111‧‧‧矽 substrate

102, 112‧‧‧ diffusion layer

103, 113‧‧‧ anti-reflection film

104‧‧‧BSF layer

105, 115‧‧‧ first electrode

106‧‧‧2nd electrode

107‧‧‧passivation film

114‧‧‧p ⁺ layer

116‧‧‧electrode

OA‧‧‧ openings

Fig. 1 is a cross-sectional view showing the structure of a double-sided electrode type solar cell element.

2 is a cross-sectional view showing a first configuration example of a solar battery element according to the embodiment.

3 is a cross-sectional view showing a second configuration example of a solar cell element according to the embodiment.

Fig. 4 is a cross-sectional view showing a third configuration example of the solar battery element of the embodiment.

Fig. 5 is a cross-sectional view showing a fourth configuration example of the solar battery element of the embodiment.

Fig. 6 is a cross-sectional view showing another configuration example of the solar battery element of the embodiment.

In the present specification, the term "step" means not only an independent step, but even in the case where it cannot be clearly distinguished from other steps, it is included in the term as long as the intended effect of the step can be achieved. In addition, in this specification, the numerical range represented by "~" is a range which contains the numerical value of the before and after "~" as a minimum and maximum. Further, in the present specification, when a plurality of substances corresponding to the respective components are present in the composition in the content of each component in the composition, unless otherwise specified, it means the plurality of substances present in the composition. Total measurement. In addition, in the present specification, the term "layer" includes, in addition to the configuration of the shape formed on the entire surface when viewed in a plan view, the shape formed on a part. Composition.

<Method of Manufacturing Semiconductor Substrate with Passivation Layer>

The method for producing a semiconductor substrate with a passivation layer according to the present invention includes the steps of: providing a composition for forming a passivation layer containing a compound represented by the following formula (I) on a semiconductor substrate to form a composition layer; The step of heat-treating the composition layer at 300 ° C to 1000 ° C to form a passivation layer. The above manufacturing method may further include other steps as needed.

M(OR ¹ ) _m (I)

Wherein M comprises at least one metal element selected from the group consisting of Nb, Ta, V, Y and Hf, and R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or an aromatic group having 6 to 14 carbon atoms; Base, m represents an integer from 1 to 5.

According to the above manufacturing method, a passivation layer having an excellent passivation effect can be formed on a semiconductor substrate. The reason for this can be presumed as follows. That is, the metal oxide obtained by converting the 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 by the presence of a compound having a fixed charge on the surface of the semiconductor substrate, band bending is generated and recombination of the carrier is suppressed. Further, by performing heat treatment under the condition that the metal oxide is amorphous without a specific crystal structure, a passivation layer composed of an amorphous metal oxide can be formed. It is considered that if the metal oxide constituting the passivation layer is sufficiently amorphous, the semiconductor substrate can be made blunt The layer is more effective in having a fixed charge, so that a more excellent passivation effect can be obtained.

The semiconductor substrate is not particularly limited, and may be appropriately selected from those generally used depending on the purpose. Examples of the semiconductor substrate include those in which p-type impurities or n-type impurities are doped in ruthenium, osmium or the like. Among them, a tantalum substrate is preferred. Further, the semiconductor substrate may be a p-type semiconductor substrate or an n-type semiconductor substrate. Among them, from the viewpoint of the passivation effect, a semiconductor substrate in which the surface on which the passivation layer is formed is a p-type layer is preferable. The p-type layer on the semiconductor substrate may be a p-type layer derived from a p-type semiconductor substrate, or may be formed on an n-type semiconductor substrate or a p-type semiconductor substrate as a p-type diffusion layer or a p ⁺ -type diffusion layer.

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

The method for producing a semiconductor substrate with a passivation layer is preferably a step of providing an aqueous alkaline solution to the semiconductor substrate before the step of forming the composition layer. In other words, it is preferable to clean the surface of the semiconductor substrate with an alkaline aqueous solution before applying the composition for forming a passivation layer on the semiconductor substrate. By washing with an alkaline aqueous solution, organic substances, particles, and the like existing on the surface of the semiconductor substrate can be removed, and the passivation effect tends to be further improved. A cleaning method using an alkaline aqueous solution can be exemplified by RCA (Radio Corporation of America) cleaning or the like which is generally known. For example, the organic substance and the particles can be removed by immersing the semiconductor substrate in a mixed solution of ammonia water and hydrogen peroxide water and treating at 60 ° C to 80 ° C. The treatment time is preferably from 10 seconds to 10 minutes, and preferably from 30 seconds to 5 minutes.

The method of forming the composition layer by providing the composition for forming a passivation layer on the semiconductor substrate is not particularly limited. For example, a method of providing the composition for forming a passivation layer on a semiconductor substrate by a known coating method or the like can be mentioned. Specific examples thereof include a dipping method, a printing method, a spinning method, a brush coating method, a spray method, a doctor blade method, a roll coater method, and an inkjet method. Among these methods, from the viewpoint of pattern formability, a printing method, an inkjet method, and the like are preferable.

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

The composition layer formed by the composition for forming a passivation layer is subjected to heat treatment (calcination) to form a heat-treated material layer derived from the composition layer, whereby a passivation layer can be formed on the semiconductor substrate. In the above 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 producing 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. By the heat treatment temperature in the 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 organic metal compound is not sufficiently converted into a metal oxide. When the temperature of the heat treatment is higher than 1000 ° C, crystallization tends to proceed excessively.

Since the passivation layer of the semiconductor substrate is composed of an amorphous M _x O _y layer, the passivation layer of the semiconductor substrate can be more effectively fixed with a charge, so that a more excellent passivation effect can be obtained. From the viewpoint of more fully converting the organometallic compound into a metal oxide, the temperature of the heat treatment is preferably 450 ° C or higher, preferably 600 ° C or higher. From the viewpoint of further suppressing excessive crystallization, the temperature of the heat treatment is preferably 900 ° C or lower, preferably 800 ° C or lower.

The temperature of the heat treatment can be set, for example, in the range of 600 ° C to 1000 ° C, preferably in the range of 600 ° C to 800 ° C. Alternatively, the temperature of the heat treatment may be set, for example, in the range of 300 ° C to 900 ° C, preferably in the range of 450 ° C to 800 ° C.

From the viewpoint of further suppressing excessive crystallization, the heat treatment time is preferably 10 hours or shorter, more preferably 5 hours or shorter, and further preferably less than 3 hours.

The heat treatment time can be set, for example, within 10 hours, preferably within 5 hours.

In the present specification, the heat treatment time refers to the length of time during which the temperature of the semiconductor substrate is within the temperature range of the heat treatment. The method of the heat treatment is not particularly limited, and a usual method can be used. For example, a calcination furnace can be used for heat treatment in an atmosphere composition environment.

The layer thickness of the passivation layer produced by the above-described method for producing a semiconductor substrate with a passivation layer is not particularly limited, and may be appropriately selected depending on the purpose. For example, it is preferably 5 nm to 50 μm, more preferably 10 nm to 30 μm, and still more preferably 15 nm to 20 μm.

The layer thickness of the above passivation layer is measured by a usual method using a stylus type step/surface shape measuring device (for example, Ambios).

The method for producing a semiconductor substrate with a passivation layer may further include a step of drying the composition layer before the step of heat-treating the composition layer obtained by providing the composition for forming a passivation layer to form a passivation layer. By Drying the composition layer has a tendency to form a passivation layer having a more uniform passivation effect.

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 is optionally removed. The drying treatment can be set, for example, at 30 ° C to 250 ° C for 1 minute to 60 minutes, preferably at 40 ° C to 220 ° C for 3 minutes to 40 minutes. Further, the drying treatment can be carried out under normal pressure or under reduced pressure.

A composition for forming a passivation layer containing a specific organometallic compound is applied onto a semiconductor substrate to form a composition layer of a desired shape, and is subjected to calcination treatment at 300 ° C to 1000 ° C, whereby excellent passivation can be obtained The passivation layer of the effect is formed into a desired shape. Since the method of the present invention does not require a vapor deposition device or the like, it is simple and highly productive. Further, the passivation layer can be formed into a desired shape without complicated steps such as masking treatment. In addition, since the composition for forming a passivation layer contains a specific organometallic compound, the occurrence of defects such as gelation is suppressed, and the storage stability over time is excellent.

In the present specification, the passivation effect of the semiconductor substrate can be evaluated by the following means: a life measuring device (Sinton Instruments, WCT-120), etc., which is constant by simulation at room temperature (25 ° C). The state photoconductivity method measures the effective lifetime of a minority carrier in a semiconductor substrate to which a passivation layer of a semiconductor substrate is applied.

Here, the effective lifetime τ is expressed by the following formula (A) by the bulk lifetime τ _b in the semiconductor substrate and the surface lifetime τ _{s of the} surface of the semiconductor substrate. When the surface energy density of the surface of the semiconductor substrate is small, τ _s becomes large, and as a result, the effective lifetime τ becomes large. Further, even if defects such as dangling bonds in the semiconductor substrate are reduced, the body life τ _{b is} increased and the effective life τ is increased. That is, the interface characteristics of the passivation layer/semiconductor substrate and the internal characteristics of the semiconductor substrate such as dangling bonds can be evaluated by measuring the effective lifetime τ.

1/τ=1/τ _b +1/τ _s (A)

A long effective life means that the recombination speed of a few carriers is slow. Further, by using a semiconductor substrate having a long effective life to constitute a solar cell element, conversion efficiency is improved.

(compound represented by the formula (I))

The composition for forming a passivation layer contains at least one of a compound (specific organometallic compound) represented by the formula (I). The above specific organometallic compound is a compound called a metal alkoxide. Further, the specific organometallic compound described above is a metal oxide (M _x O _y ) by heat treatment.

The reason why the passivation layer having an excellent passivation effect can be formed by the composition for forming a passivation layer containing a specific organometallic compound is considered by the inventors as follows. When the oxide formed by the calcination treatment of the composition for forming a passivation layer containing a specific organometallic compound is subjected to heat treatment at 300 ° C to 1000 ° C, the oxide tends to be in an amorphous state. It can be considered that if the metal oxide is In the amorphous state, a defect of a metal atom or the like is generated to have a large fixed charge in the vicinity of the interface with the semiconductor substrate. It is considered that the large fixed electric charge generates an electric field in the vicinity of the interface of the substrate, whereby the concentration of the minority carrier can be lowered, and as a result, the carrier recombination speed at the interface is suppressed, so that a passivation layer having an excellent passivation effect can be formed.

Furthermore, the fixed charge of the metal oxide can be evaluated by Capacitance Voltage Measurement (CV). Among them, the surface energy density of the passivation layer formed of the composition for forming a passivation layer of the present invention may be a larger value than the case of the metal oxide layer formed by the ALD or CVD method. However, the passivation layer formed of the composition for forming a passivation layer of the present invention has a large electric field effect and a small concentration of a carrier decreases, and the surface lifetime τ _s becomes large. Therefore, the surface energy density is relatively unproblematic.

In the formula (I), M contains at least one metal element selected from the group consisting of Nb, Ta, V, Y and Hf. From the viewpoint of the passivation effect, the storage stability of the composition for forming a passivation layer, and the workability in preparing a composition for forming a passivation layer, M preferably contains a group selected from the group consisting of Nb, Ta, and Y. At least one metal element. 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 more preferably contains Nb selected from At least one of a group consisting of Ta, VO, and Hf.

In the formula (I), R ¹ each 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, more preferably 1 to 8 carbon atoms. 4 alkyl groups. The alkyl group represented by R ¹ may be linear or branched. Specific examples of the alkyl group represented by R ¹ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a second butyl group, a tert-butyl group, a hexyl group, an octyl group, and a 2-ethyl group. Hexyl, 3-ethylhexyl and the like. Specific examples of the aryl group represented by R ¹ include a phenyl group. The alkyl group and the aryl group represented by R ¹ may have a substituent, and examples of the substituent of the alkyl group include a halogen element, an amine group, a hydroxyl group, a carboxyl group, a thiol group, and a nitro group. The substituent of the aryl group may, for example, be a methyl group, an ethyl group, an isopropyl group, an amine group, a hydroxyl group, a carboxyl group, a decyl group or a nitro group.

Among them, from the viewpoint of storage stability and passivation effect, R ^{1 is} preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms.

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

The specific organometallic compound represented by the formula (I) preferably has at least one metal element selected from the group consisting of Nb, Ta and Y, and R ¹ is an unsubstituted carbon number of 1 to 4. Alkyl, m is an integer from 1 to 5.

The state of the particular organometallic compound can be either solid or liquid. The specific organometallic compound is preferably a liquid from the viewpoint of the storage stability of the composition for forming a passivation layer and the mixing property in the case of using the compound represented by the following formula (II).

Specific organometallic compounds include methanol hydrazine, hydrazine ethoxide, hydrazine isopropoxide, hydrazine n-propoxide, hydrazine n-butoxide, hydrazine tert-butoxide, hydrazine isobutoxide, hydrazine hydrazine, hydrazine ethoxide, hydrazine isopropoxide , n-propanol oxime, n-butanol oxime, t-butanol oxime, isobutanol 钽, methanol oxime, ethanol oxime, bismuth isopropoxide, ruthenium n-propoxide, ruthenium n-butoxide, ruthenium tert-butoxide, ruthenium isobutoxide, vanadium oxyhydroxide, vanadium oxide, oxidized vanadium isopropoxide, n-propyl Alcohol oxide vanadium oxide, n-butanol vanadium oxide, third butanol vanadium oxide, isobutanol vanadium oxide, methanol oxime, ethanol oxime, bismuth isopropoxide, ruthenium n-propoxide, ruthenium n-butoxide, ruthenium tert-butoxide Isobutanol oxime or the like, among which, ethanol oxime, ruthenium n-propoxide, ruthenium n-butoxide, ruthenium ethoxide, ruthenium n-propoxide, ruthenium n-butoxide, ruthenium isopropoxide and ruthenium n-butoxide are preferable. From the viewpoint of obtaining a negative fixed charge density, ethanol ruthenium, ruthenium n-propoxide, ruthenium n-butoxide, ruthenium ethoxide, ruthenium n-propoxide, ruthenium n-butoxide, vanadium oxide, and vanadium oxide of n-propanol are preferred. , n-butanol oxide vanadium, ethanol oxime, n-propanol oxime and n-butanol oxime.

As the specific organometallic compound, a preparation can be used, and a commercially available product can also be used. Commercially available products include, for example, pentamethoxy hydrazine, pentaethoxy hydrazine, pentaisopropoxy fluorene, penta-n-propoxy fluorene, penta-isobutoxy fluorene, and five. n-Butoxy fluorene, penta-butoxy fluorene, pentamethoxy fluorene, pentaethoxy hydrazine, pentaisopropoxy fluorene, penta-n-propoxy fluorene, penta-isobutoxy fluorene, five-positive Butoxy oxime, penta-second butoxy ruthenium, penta-t-butoxy ruthenium, vanadium oxyhydroxide (V), triethoxy vanadium oxide (V), triisopropanol vanadium oxide (V) , tri-n-propanol vanadium oxide (V), triisobutanol vanadium oxide (V), tri-n-butanol vanadium oxide (V), tri-second butanol vanadium oxide (V), tri-tert-butanol oxidation Vanadium (V), triisopropoxy ruthenium, tri-n-butoxy ruthenium, tetramethoxy ruthenium, tetraethoxy ruthenium, tetraisopropoxy ruthenium, tetra-t-butoxy ruthenium; Beixing Chemical Industry Co., Ltd.'s pentaethoxy oxime, pentaethoxy hydrazine, pentabutoxy fluorene, n-butanol oxime, t-butanol oxime; Nichia Chemicals Co., Ltd. oxytriethanol vanadium, oxy three Vanadium n-propoxide, vanadium oxy-n-butoxide, vanadium oxytriisobutoxide, Oxygen tri-second butanol vanadium and the like.

In the preparation of a specific organometallic compound, a known method such as reacting a specific metal (M) halide with an alcohol in the presence of an inert organic solvent, and further adding ammonia or an amine for capturing halogen can be used. A method of the invention is disclosed in Japanese Laid-Open Patent Publication No. SHO63-227593, and Japanese Patent Application Laid-Open No. Hei No. 3-291247.

The specific organometallic compound can also be formed into a compound having a chelate structure by mixing with a compound having a specific structure of two carbonyl groups to be described later. When a specific organometallic oxide is mixed with a compound having a specific structure of two carbonyl groups, at least a part of the alkoxide group of the specific organometallic compound is replaced with a compound having a specific structure to form a chelate structure. At this time, a solvent may be present as needed, and heat treatment or addition of a catalyst may be performed. By replacing at least a part of the alkoxide structure with a chelate structure, the stability of the specific organometallic compound to hydrolysis, polymerization, and the like is improved, and the storage stability of the composition for forming a passivation layer containing the same is further improved.

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

Specific examples of the β-diketone compound include acetamidineacetone, 3-methyl-2,4-pentanedione, 2,3-pentanedione, 3-ethyl-2,4-pentanedione, and 3-butyl Base-2,4-pentanedione, 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 the β-ketoester compound include methyl ethyl acetate and ethyl acetate Ester, propyl acetate, isopropyl acetate, isobutyl acetate, butyl acetate, butyl acetate, amyl acetate, isoamyl acetate, Hexyl acetate, n-octyl acetate, heptyl acetate, 3-pentyl acetate, ethyl 2-ethylhydrazine heptanoate, ethyl 2-methylacetate, 2-butyl Ethyl acetate, ethyl hexylacetate, ethyl 4,4-dimethyl-3-oxopentanoate, ethyl 4-methyl-3-oxopentanoate, 2-ethylethyl hydrazine Ethyl acetate, ethyl hexylacetate, methyl 4-methyl-3-oxopentanoate, ethyl 3-oxohexanoate, ethyl 3-oxopentanoate, 3-oxopentanoate Ester, methyl 3-oxohexanoate, ethyl 3-oxoheptanoate, methyl 3-oxoheptanoate, methyl 4,4-dimethyl-3-oxopentanoate and the like.

Specific examples of the malonic acid diester include dimethyl malonate, diethyl malonate, dipropyl malonate, diisopropyl malonate, dibutyl malonate, and malonic acid di- Third butyl ester, dihexyl malonate, tert-butyl ethyl malonate, diethyl methyl malonate, diethyl ethyl malonate, diethyl isopropyl malonate, Diethyl butyl malonate, diethyl second butyl malonate, diethyl isobutyl malonate, diethyl 1-methylbutyl malonate, and the like.

In the case where the specific organometallic compound has a chelate structure, there is no particular limitation as long as the number of the chelate structures is from 1 to 5. Among them, from the viewpoint of solubility, the number of chelating structures is preferably 1. The number of chelating structures can be controlled, for example, by appropriately adjusting the ratio of mixing a specific organometallic compound with a compound which can form a chelate with a metal element. Further, a compound having a desired structure may be appropriately selected from commercially available metal chelate compounds.

The presence of a chelating structure in a particular organometallic compound can be utilized Often used analytical methods to confirm. For example, it can be confirmed using an infrared spectroscopic spectrum, a nuclear magnetic resonance spectrum, a melting point, or the like.

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

(compound represented by the formula (II))

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

In the formula, R ² each independently represents an alkyl group having 1 to 8 carbon atoms. n represents an integer from 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 passivation effect can be further improved by including the above-described organoaluminum compound in the composition for forming a passivation layer. This case can be considered as follows.

The organoaluminum compound contains a compound called aluminum alkoxide, aluminum chelate or the like, and preferably has a chelate aluminum structure in addition to the aluminum alkoxide structure. In addition, as described in "Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi", vol. 97, pp. 369-399 (1989), the above organoaluminum compound is alumina by heat treatment (calcination). (Al ₂ O ₃ ). At this time, it is considered that the formed alumina is likely to be in an amorphous state, so that a tetracoordinated alumina layer can be easily formed in the vicinity of the interface with the semiconductor substrate, and a large negative fixed charge caused by the tetracoordinate alumina is obtained. . At this time, it can be considered that by combining with an oxide derived from a specific organometallic compound having a fixed charge, a passivation layer having an excellent passivation effect can be formed.

It is considered that the passivation effect is made higher by utilizing the respective effects in the passivation layer by combining a specific organometallic compound with an organoaluminum compound. Further, it is considered that the composite metal alkoxide of metal (M) and aluminum (Al) in a specific organometallic compound is subjected to heat treatment (calcination) in a state in which a specific organometallic compound is mixed with an organoaluminum compound. The physical properties such as reactivity and vapor pressure are improved, and the density of the passivation layer as a heat-treated product (calcined product) is improved, and as a result, the passivation effect is further improved.

In the formula (II), R ² each independently represents an alkyl group having 1 to 8 carbon atoms, 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 a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a second butyl group, a tert-butyl group, a hexyl group, an octyl group, an ethylhexyl group, and the like. . In view of the storage stability and the passivation effect, the alkyl group represented by R ² is preferably an unsubstituted alkyl group having 1 to 8 carbon atoms, more preferably an unsubstituted carbon group having 1 to 4 carbon atoms. alkyl.

In the 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, more preferably 1 or 3. Further, 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 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, 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 second butyl group, a tert-butyl group, a hexyl group, and a octyl group. Base, ethylhexyl and the like.

In view of the storage stability and the passivation effect, R ³ and R ⁴ in the formula (II) are preferably independently a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms, more preferably Preferably, it is a hydrogen atom or an unsubstituted alkyl group having 1 to 4 carbon atoms. Further, R ⁵ in the formula (II) is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 8 carbon atoms, more preferably a hydrogen atom or a carbon number, from the viewpoint of storage stability and passivation effect. 1 to 4 unsubstituted alkyl groups.

From the viewpoint of storage stability and passivation effect, 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.

The organoaluminum compound is preferably at least one selected from the group consisting of: n is 0, and R ^{2 is} independently an alkyl group having 1 to 4 carbon atoms, from the viewpoint of storage stability and passivation effect. a compound; and n is 1 to 3, R ^{2 is} independently an alkyl group having 1 to 4 carbon atoms, at least one of X ² and X ³ is an oxygen atom, and R ³ and R ⁴ are each independently a hydrogen atom or carbon. A compound having 1 to 4 alkyl groups and R ⁵ being a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

More preferably, the organoaluminum compound is at least one selected from the group consisting of: n is 0, and R ^{2 is} independently a compound having an unsubstituted alkyl group having 1 to 4 carbon atoms; and n is 1 ~3, R ² are 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 above oxygen atom is a carbon number of 1 The alkyl group of ~4, when X ² or X ³ is a methylene group, is a compound in which R ³ or R ⁴ of the above methylene group is a hydrogen atom and R ⁵ is a hydrogen atom.

Specific examples of the organoaluminum compound (aluminum trialkoxide) wherein n is 0 in the formula (II) include trimethoxy aluminum, triethoxy aluminum, triisopropoxy aluminum, and tri-second butoxide aluminum. , single second butoxy-diisopropoxy aluminum, tri-t-butoxy aluminum, tri-n-butoxy aluminum, and the like.

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

The organoaluminum compound in which n is 1 to 3 in the formula (II) can be used as a preparation. Commercial products can also be used. Commercially available products include, for example, trade names ALCH, ALCH-50F, ALCH-75, ALCH-TR, and ALCH-TR-20 of Kawasaki Seika Co., Ltd.

The organoaluminum compound in which n is 1 to 3 in the formula (II) can be produced by mixing the above aluminum trialkoxide with a compound having a specific structure of two carbonyl groups. Further, a commercially available chelated aluminum compound can also be used.

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

Examples of the compound having a specific structure of two carbonyl groups include the above-mentioned β-diketone compound, β-ketoester compound, malonic acid diester, etc., and from the viewpoint of storage stability, it is preferably selected from β-diketone. At least one of a group consisting of a compound, a β-ketoester compound, and a malonic acid diester.

When the organoaluminum compound has a chelate aluminum structure, the number of the chelate aluminum structures is not particularly limited as long as it is from 1 to 3. Among them, from the viewpoint of storage stability, it is preferably 1 or 3, and more preferably 1 in terms of solubility. The number of the aluminum chelate structures can be controlled, for example, by appropriately adjusting the ratio of the above aluminum trialkoxide and the compound which can form a chelate compound with aluminum, and the like having a specific structure of two carbonyl groups. In addition, commercially available chelated aluminum compounds are also available. A compound having a desired structure is appropriately selected.

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

The organoaluminum compound may be in the form of a liquid or a solid, and is not particularly limited. From the viewpoint of 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 good solubility or dispersibility. The desired passivation effect is obtained stably.

In the case where 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 may be appropriately selected as needed. For example, the content of the organoaluminum compound can be set to 0.1% by mass to 60% by mass, preferably 0.5% by mass to 55% by mass, based on the storage stability and the passivation effect. More preferably, it is 1 mass% - 50 mass%, and further preferably 1 mass% - 45 mass%.

In the case where the composition for forming a passivation layer contains an organoaluminum compound, the total content of the specific organometallic compound and the organoaluminum compound (hereinafter collectively referred to as "organometallic compound") is 100% by mass, and the organoaluminum is used. 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, further preferably 2% by mass or more and 70% by mass or less, and particularly preferably 3% by mass or more. 70% by mass or less. When the content of the organoaluminum compound is set to 0.5% by mass or more, the storage stability of the composition for forming a passivation layer tends to be improved. In addition, by setting the organoaluminum compound to 80% by mass or less, there is The tendency to improve the passivation effect.

(resin)

The composition for forming a passivation layer may further contain at least one resin. The shape stability of the composition layer formed by imparting the composition for forming a passivation layer onto the semiconductor substrate by the resin is further improved, and can be selectively selected in a desired shape in a region where the composition layer is formed. A passivation layer is formed.

The kind of the above resin is not particularly limited. In particular, when the composition for forming a passivation layer is applied to a semiconductor substrate, the viscosity can be adjusted to a resin in a range in which good pattern formation can be performed. Specific examples of the above resin include polyvinyl alcohol, polypropylene decylamine, polypropylene decylamine derivative, polyvinyl decylamine, polyvinyl decylamine derivative, polyvinylpyrrolidone, polyethylene oxide, and poly Ethylene oxide derivative, polysulfonic acid, polypropylene decylalkylsulfonic acid, cellulose, cellulose derivative (cellulose ether such as carboxymethyl cellulose, hydroxyethyl cellulose, ethyl cellulose, etc.) , gelatin, gelatin derivatives, starch, starch derivatives, sodium alginate, sodium alginate derivatives, xanthan, trisin derivatives, guar gum, guar gum derivatives, Scleroglucan, scleroglucan derivative, tragacanth gum, tragacanth derivative, dextrin, dextrin derivative, (meth)acrylic resin, (methyl Acrylate resin (alkyl (meth) acrylate resin, dimethylaminoethyl (meth) acrylate resin, etc.), butadiene resin, styrene resin, decane resin, copolymers thereof Wait. These resins may be used alone or in combination of two or more.

Among these resins, from the viewpoint of storage stability and pattern formation, It is preferred to use a neutral resin which does not have an acidic or basic functional group, and it is more preferable to use a cellulose derivative from the viewpoint of easily adjusting the viscosity and thixotropy even when the content is small.

Further, the molecular weight of the resins is not particularly limited, and is preferably adjusted as appropriate in consideration of the desired viscosity as a composition for forming a passivation layer. The weight average molecular weight of the above resin is preferably from 100 to 10,000,000, more preferably from 1,000 to 5,000,000, from the viewpoint of storage stability and pattern formation. Further, the weight average molecular weight of the resin was determined by conversion using a calibration curve of standard polystyrene by a molecular weight distribution measured by Gel Permeation Chromatography (GPC). The calibration curve was obtained by a three-time approximation using five sample sets of standard polystyrene (PStQuick MP-H, PStQuick B [Tosoh Corporation, trade name]). The measurement conditions of GPC are shown below.

Device: (Pump: L-2130 [Hitachi High-Technologies Co., Ltd.])

(Detector: L-2490 Refractive Index (RI) [Hitachi High-Technologies Co., Ltd.])

(column oven: L-2350 [Hitachi High-Technologies Co., Ltd.])

Pipe column: Gelpack GL-R440+Gelpack GL-R450+Gelpack GL-R400M (3 in total) (Hitachi Chemical Co., Ltd., trade name)

Column size: 10.7mm (inside diameter) × 300mm

Dissolution: tetrahydrofuran

Sample concentration: 10mg/2mL

Injection volume: 200μL

Flow rate: 2.05mL/min

Measuring 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 may be appropriately selected as needed. For example, the content of the resin is preferably from 0.1% by mass to 50% by mass based on the composition for forming a passivation layer. The content ratio is more preferably from 0.2% by mass to 25% by mass, even more preferably from 0.5% by mass to 20% by mass, even more preferably 0.5% by mass, from the viewpoint of exhibiting thixotropy in which pattern formation is more easily performed. 15% by mass.

In the case where the composition for forming a passivation layer contains a resin, the content ratio (mass ratio) of the organometallic compound in the composition for forming a passivation layer and the above resin may be appropriately selected as necessary. In view of the pattern formation property and the storage stability, the content ratio of the resin to the organometallic compound (resin/organometallic compound) is preferably 0.001 to 1,000, more preferably 0.01 to 100, and still more preferably 0.1 to 0.1. 1.

(liquid medium)

The composition for forming a passivation layer may also contain a liquid medium (solvent or dispersion medium). When the composition for forming a passivation layer contains a liquid medium, the viscosity is adjusted more easily, and the impartability is further improved, and a more uniform passivation layer tends to be formed. The liquid medium is not particularly limited and may be appropriately selected as needed. Among them, a liquid medium in which the above organometallic compound and a resin used as needed are dissolved to obtain a uniform solution is preferred, and more preferably at least one organic solvent is contained. Liquid The medium refers to a medium in a state of being liquid 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, and methyl n-amyl ketone. Methyl n-hexyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, trimethyl fluorenone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, Ketone solvent such as acetone-acetone; diethyl ether, methyl ethyl ether, methyl n-propyl ether, diisopropyl ether, tetrahydrofuran, methyl tetrahydrofuran, dioxane, dimethyl dioxane, ethylene glycol Ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, two 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, triethyl Diol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl n-butyl ether, triethylene glycol di-n-butyl ether, triethylene glycol methyl Ether, tetraethylene glycol dimethyl ether, tetraethylene glycol 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 methyl n-butyl ether, two Propylene 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, three Propylene glycol di-n-butyl ether, tripropylene glycol methyl n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetrapropylene glycol methyl n-butyl ether, tetrapropylene glycol di-n-butyl ether, Ether solvent such as tetrapropylene glycol methyl n-hexyl ether or tetrapropylene glycol di-n-butyl ether; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, second acetic acid Ester, n-amyl acetate, second amyl acetate, 3-methoxybutyl acetate, methyl amyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, 2-(2-acetic acid) Butoxyethoxy)ethyl ester, benzyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, decyl acetate, methyl acetate, ethyl acetate, diethylene glycol methyl ether, Diethylene glycol monoethyl ether, dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether, diacetate glycol, methoxy triethylene glycol acetate, isoamyl acetate, ethyl propionate, n-butyl propionate , isoamyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-amyl lactate, ethylene glycol methyl ether propionate, ethylene glycol ether Acid ester, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol diethyl ether acetate, propylene glycol ethyl ether Esters, γ-butyrolactone, γ-valerolactone and other ester solvents; acetonitrile, N-methylpyrrolidone, N-ethylpyrrolidone, N-propylpyrrolidone, N-butylpyrrolidone, N-hexylpyrrolidone, N- Aprotic polar solvents such as cyclohexyl pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylhydrazine; dichloromethane, chloroform, dichloroethane, benzene Hydrophobic organic solvents such as toluene, xylene, hexane, octane, ethylbenzene, 2-ethylhexanoic acid, methyl isobutyl ketone, methyl ethyl ketone; methanol, ethanol, n-propanol, isopropyl Alcohol, n-butanol, isobutanol, second butanol, tert-butanol, n-pentanol, isoamyl alcohol, 2-methylbutanol, second pentanol, third pentanol, 3-methoxy Butanol, n-hexanol, 2-methylpentanol, second hexanol, 2-ethylbutanol, second heptanol, n-octanol, 2-ethylhexanol, second octanol, n-nonanol, N-nonanol, second-undecyl alcohol, trimethyldecyl alcohol, second - myristyl alcohol, second heptadecyl alcohol, cyclohexanol, methylcyclohexanol, isobornyl cyclohexanol, benzyl alcohol, ethylene glycol, 1,2-propanediol, 1,3-butane Alcohol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol and other alcohol solvents; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, two Ethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, ethoxy triethylene glycol, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, a glycol monoether solvent such as dipropylene glycol monoethyl ether or tripropylene glycol monomethyl ether; terpinene, terpineol, myrcene, allophymene, limonene, dipentene, decene, carbon, basil a terpene solvent such as ocimene or phellandrene; water or the like. These liquid mediums may be used alone or in combination of two or more.

In view of the impartability and pattern formation property of the semiconductor substrate, the liquid medium preferably contains at least one selected from the group consisting of a terpene solvent, an ester solvent, and an alcohol solvent.

In the liquid medium, when a high viscosity and a low boiling point are used, there is an advantage that the shape of the composition layer can be sufficiently maintained when a composition for forming a passivation layer is applied to a semiconductor substrate to form a composition layer; Since it is volatilized in the subsequent heat treatment step, the influence of the residual solvent or the like does not occur. Specific examples of the high-viscosity low-boiling solvent include isobornylcyclohexanol.

When the composition for forming a passivation layer contains a liquid medium, the content of the liquid medium is determined in consideration of impartability, pattern formation property, and storage stability. For example, the content of the liquid medium is preferably from 5% by mass to 98% by mass based on the total mass of the composition for forming a passivation layer, from the viewpoint of the impartability of the composition and the pattern formation property. %, more preferably 10% by mass to 95% by mass.

(other ingredients)

The composition for forming a passivation layer of the present invention may contain other components in addition to the above components. Other components include plasticizers, dispersants, surfactants, thixotropic agents, inorganic fillers, and other metal alkoxide compounds. In the case where the passivation layer is formed into a pattern, it is preferred to contain at least one selected from the group consisting of a thixotropic agent and an inorganic filler. The shape stability of the composition layer formed by imparting the composition for forming a passivation layer onto the semiconductor substrate by at least one selected from the group consisting of a thixotropic agent and an inorganic filler is further improved, and the composition layer can be formed. A passivation layer is formed in the desired shape in the region.

In view of the storage stability of the composition for forming a passivation layer, the content of the acidic compound and the basic compound is preferably 1% by mass or less, and more preferably 0.1% by mass or less, based on the composition for forming a passivation layer. .

Examples of the acidic compound include Bronsted acid and Lewis acid. Specific examples thereof include inorganic acids such as hydrochloric acid and nitric acid; and organic acids such as acetic acid. Further, examples of the basic compound include a Bruce base and a Lewis base. Specific examples thereof include an inorganic base such as an alkali metal hydroxide or an alkaline earth metal hydroxide, an organic base such as a trialkylamine or a pyridine.

The viscosity of the composition for forming a passivation layer is not particularly limited, and can be appropriately selected depending on the method of applying the semiconductor substrate or the like. For example, it can be set to 0.01Pa. s~10,000Pa. s. Among them, from the viewpoint of pattern formation, it is preferably 0.1 Pa. s~1000Pa. s. Further, the above viscosity was measured at a shear rate of 1.0 s ^-1 at 25 ° C 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 viewpoint of pattern formation, the shear viscosity η ₁ at a shear rate of 1.0 s ^-1 is divided by the shear viscosity η ₂ at a shear rate of 10 s ^-1 (η _{1 )} /η ₂ ) is preferably from 1.05 to 100, more preferably from 1.1 to 50. Further, the shear viscosity was measured at a temperature of 25 ° C using a rotary shear viscometer equipped with a cone plate (having a diameter of 50 mm and a taper angle of 1 °).

The method for producing the composition for forming a passivation layer is not particularly limited. For example, it can be produced by mixing an organometallic compound with a resin, a liquid medium or the like which is optionally contained, by a mixing method which is usually used. Alternatively, it may be produced by dissolving a resin in a solvent to obtain a solution, and then mixing the above solution with an organometallic compound.

Further, the organometallic compound may be prepared by mixing an alkoxide of a metal contained in the organometallic compound with a compound capable of forming a chelate with the above metal. At this time, a solvent may be used as needed, and heat treatment may be performed. The organometallic compound thus prepared may be mixed with a resin or a resin-containing solution to produce a composition for forming a passivation layer.

Further, the content of each component contained in the composition for forming a passivation layer can be determined by thermal analysis such as thermogravimetric-differential thermal analysis (TG/DTA) or nuclear magnetic resonance (Nuclear Magnetic Resonance, NMR, Infrared spectroscopy (IR) and other spectral analysis, high performance liquid chromatography (High Performance Liquid) Chromatography, HPLC), gel permeation chromatography (GPC), and the like were confirmed by chromatography analysis.

<Semiconductor Substrate with Passivation Layer>

The semiconductor substrate with a passivation layer of the present invention is a semiconductor substrate with a passivation layer obtained by a method for producing a semiconductor substrate with a passivation layer comprising the steps of: providing a semiconductor substrate with a formula (I) a step of forming a passivation layer of a specific organometallic compound to form a composition layer; and 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 has a semiconductor substrate and a passivation layer which is a heat-treated material layer (calcined material layer) obtained by heat-treating the following composition layer at 300 ° C to 1000 ° C, The composition layer is formed by providing a composition for forming a passivation layer containing a specific organometallic compound represented by the general formula (I) on the entire surface or a part of the semiconductor substrate. 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 above semiconductor substrate with a passivation layer can be applied to a solar cell element, a light emitting diode element, or the like. For example, a solar cell element excellent in conversion efficiency can be obtained by being applied to a solar cell element.

<Solar battery component>

The solar cell element of the present invention comprises: a semiconductor substrate obtained by pn-bonding a p-type layer and an n-type layer; and a passivation layer which is at 300 ° C for the following composition layer Obtained by heat treatment at 1000 ° C, wherein the composition layer is formed by providing a composition for forming a passivation layer containing a specific organometallic compound on the entire surface or a part of the semiconductor substrate; and an electrode disposed on the above At least one of the p-type layer and the n-type layer of the semiconductor substrate. The above solar cell element may have other components as needed.

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 producing a semiconductor substrate with a passivation layer of the present invention can be used. From the viewpoint of conversion efficiency, the surface of the semiconductor substrate provided with the passivation layer is preferably a surface on which a p-type layer in the solar cell element exists. The thickness of the passivation layer is not particularly limited and may be appropriately selected depending on the purpose. For example, the average thickness of the passivation layer is preferably from 5 nm to 50 μm, more preferably from 10 nm to 30 μm, and even more preferably from 15 nm to 20 μm. The shape and size of the above solar cell element are not limited. For example, it is preferably a substantially square having a side of 125 mm to 156 mm.

<Method of Manufacturing Solar Cell Element>

The method for producing a solar cell element according to the present invention includes the step of providing a composition for forming a passivation layer on the entire surface or a part of a semiconductor substrate obtained by pn-bonding a p-type layer and an n-type layer to form a composition layer. a step of heat-treating (calcining) the composition layer at 300 ° C to 1000 ° C to form a passivation layer; and forming an electrode on at least one of the p-type layer and the n-type layer Step. The method of manufacturing the above solar cell element may further include other steps as needed.

<solar battery>

The solar cell of the present invention comprises at least one of the solar cell elements described above, and is configured by disposing a wiring material on an output extraction electrode of the solar cell element. The solar cell may be connected to a plurality of solar cell elements via a wiring material as needed, and further sealed by a sealing material. The wiring material and the sealing material are not particularly limited and may be appropriately selected from those generally used in the technical field.

[Examples]

Hereinafter, the invention will be specifically described by way of examples, but the invention is not limited to the examples. In addition, "%" is a quality standard unless otherwise specified.

<Example 1>

(Preparation of a composition for forming a passivation layer)

1.00g of ethanol oxime (manufactured by Behind Chemical Industry Co., Ltd.), 1.00g of ethyl acetoacetate diisopropylate (manufactured by Kawasaki Seika Co., Ltd.), isopropyl alcohol (manufactured by Wako Pure Chemical Industries Co., Ltd.) 18.02 g was mixed to prepare a composition 1 for forming a passivation layer. The contents of ethanol hydrazine, (ethyl acetoacetic acid) aluminum isopropoxide and isopropyl alcohol were 5.0%, 5.0% and 90.0%, respectively.

(formation of passivation layer)

A single crystal type p-type ruthenium substrate (manufactured by Mitsubishi Sumitomo (SUMCO), 50 mm square, thickness: 770 μm) having a mirror shape was used as a semiconductor substrate. The semiconductor substrate passivation layer forming composition 1 obtained above was applied to the entire surface of one side of the tantalum substrate by a spin coating method to form a composition layer. Thereafter, a group will be formed The tantalum substrate of the resultant layer was dried at 150 ° C for 5 minutes. Then, heat treatment was performed at 700 ° C for 10 minutes, and the mixture was cooled at room temperature to prepare a substrate for evaluation having a passivation layer.

(Measurement of effective life)

The life measuring device (manufactured by Sinton Instruments Co., Ltd., WCT-120) was used to measure the effective life (μs) of the substrate for evaluation obtained by the simulated constant state photo-conductivity method at room temperature (25 ° C). ). The effective life of the obtained evaluation substrate was 1765 μs.

<Example 2>

An evaluation substrate was produced in the same manner as in Example 1 except that the temperature of the heat treatment was set to 600 ° C, and the effective life was measured in the same manner as in Example 1. The effective life is 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 set to 800 ° C, and the effective life was measured in the same manner as in Example 1. The effective life is 713 μs.

<Comparative Example 1>

An evaluation substrate was produced in the same manner as in Example 1 except that the passivation layer was not formed on the substrate, and the effective lifetime was measured. The effective life is 20μs.

<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 set to 200 ° C, and the effective life was measured in the same manner as in Example 1. Effective life is 22μs.

As described above, the evaluation substrate having the passivation layer formed by heat-treating the composition for forming a passivation layer containing a specific organometallic compound at 300 ° C to 1000 ° C has a long effective life and exhibits an excellent passivation effect. . The reason for this is considered to be that the metal oxide contained in the passivation layer is sufficiently amorphous. Further, according to the manufacturing method of the present invention, the passivation layer can be formed into a desired shape by a simple procedure.

<Reference Embodiment 1>

The following is a passivation film, a coating material, a solar cell element, and a tantalum substrate with a passivation film according to the first embodiment.

<1> A passivation film containing aluminum oxide and cerium oxide, which is used in a solar cell element having a ruthenium substrate.

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

<3> The passivation film as described in <1> or <2>, wherein the above oxidation The total content of cerium and the above alumina is 90% by mass or more.

The passivation film of any one of <1> to <3> further contains an organic component.

The passivation film according to any one of <1> to <4> which is a heat-treated material of a coating material containing an alumina precursor and a cerium oxide precursor.

<6> A coating type material comprising an alumina precursor and a cerium oxide precursor for forming a passivation film of a solar cell element having a ruthenium substrate.

<7> A solar cell element comprising: a p-type germanium substrate comprising a single crystal germanium or a polycrystalline germanium, having a light receiving surface and a back surface opposite to the light receiving surface; and an n-type impurity diffusion layer formed on the germanium substrate a light-receiving surface side; a first electrode formed on a surface of the n-type impurity diffusion layer on a light-receiving surface side of the ruthenium substrate; and a passivation film formed on a surface on a back surface side of the ruthenium substrate Each of the openings includes aluminum oxide and ruthenium oxide, and the second electrode is electrically connected to a surface on the back surface side of the ruthenium substrate via the plurality of openings.

<8> A solar cell element comprising: a p-type germanium substrate comprising a single crystal germanium or a polycrystalline germanium, having a light receiving surface and a back surface opposite to the light receiving surface; and an n-type impurity diffusion layer formed on the germanium substrate The light-receiving surface side; the first electrode is the n-type impurity formed on the light-receiving surface side of the ruthenium substrate a p-type impurity diffusion layer formed on a part or all of the back surface side of the germanium substrate, and having impurities added at a higher concentration than the germanium substrate; and a passivation film formed on the surface a surface of the back surface of the ruthenium substrate having a plurality of openings and containing aluminum oxide and ruthenium oxide; and a second electrode that passes through the plurality of openings and the p-type impurity diffusion layer on the back side of the ruthenium substrate The surface forms an electrical connection.

<9> A solar cell element comprising: an n-type germanium substrate comprising a single crystal germanium or a polycrystalline germanium, having a light receiving surface and a back surface opposite to the light receiving surface; and a p-type impurity diffusion layer formed on the germanium substrate a light-receiving surface side; a second electrode formed on a back surface side of the ruthenium substrate; and a passivation film formed on a surface on a light-receiving surface side of the ruthenium substrate, having a plurality of openings and containing aluminum oxide and oxidized And a first electrode formed on the surface of the p-type impurity diffusion layer on the light-receiving surface side of the ruthenium substrate, and electrically connected to a surface on the light-receiving surface side of the ruthenium substrate via the plurality of openings .

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

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

<12> A ruthenium substrate having a passivation film, comprising: a ruthenium substrate; and a passivation film according to any one of <1> to <5>, which is provided on the entire surface or a part of the ruthenium substrate.

According to the above-described reference embodiment, the passivation film which has a carrier life of the ruthenium substrate and has a negative fixed charge can be realized at 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 germanium substrate with a passivation film which has a long carrier life and a negative fixed charge can be realized at low cost.

The passivation film of this embodiment is a passivation film used for a tantalum solar cell element, and contains aluminum oxide and ruthenium oxide.

Further, in the present embodiment, the amount of fixed charge of the film can be controlled by changing the composition of the passivation film.

Further, from the viewpoint of stabilizing the negative fixed charge, it is more preferable that the mass ratio of cerium oxide to aluminum oxide is 30/70 to 80/20. Further, from the viewpoint of making the negative fixed charge more stable, it is preferable that the mass ratio of cerium oxide to aluminum oxide is 35/65 to 70/30. Further, from the viewpoint of improving the life of the carrier and the negative fixed charge, the mass ratio of cerium oxide to aluminum oxide is preferably 50/50 to 90/10.

The mass ratio of cerium oxide to aluminum oxide in the passivation film can be determined by Energy Dispersive X-ray spectroscope (EDX) or Secondary Ion Mass Spectrometer (SIMS). And measured by Inductively coupled plasma-mass spectrometry (ICP-MS). The specific measurement conditions are as follows. Dissolving the passivation film in an acid or alkaline aqueous solution, forming the solution into a mist and introducing it into the Ar plasma, and splitting the light emitted by the excited element back to the ground state to measure the wavelength and intensity, according to the obtained The wavelength is used to characterize the element, and the amount is quantified based on the obtained intensity.

The total content of cerium 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 of cerium oxide and aluminum oxide in the passivation film are increased, the effect of negatively fixing charges becomes large.

The total content of cerium oxide and aluminum oxide in the passivation film can be determined by combining thermogravimetric analysis, fluorescent X-ray analysis, ICP-MS, and X-ray absorption spectroscopy. The specific measurement conditions are as follows. The ratio of the inorganic component was calculated by thermogravimetric analysis, and the ratio of cerium to aluminum was calculated by fluorescence X-ray or ICP-MS analysis, and the ratio of the oxide was examined by X-ray absorption spectroscopy.

Further, in the passivation film, from the viewpoint of improving the film quality or adjusting the elastic modulus, components other than cerium oxide and aluminum oxide can be contained in the form of an organic component. The presence of the organic component in the passivation film can be confirmed by elemental analysis and Fourier transform infrared spectroscopy (FT-IR) measurement of the film.

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

The passivation film can also be obtained in the form of a heat-treated product of a coating type material containing an alumina precursor and a cerium oxide precursor. The coating type material will be described in detail below.

The coating material of the present embodiment contains an alumina precursor and a cerium oxide precursor, and is used to form a passivation film for a solar cell element having a ruthenium substrate.

The alumina precursor can be used without particular limitation as long as it forms alumina. The alumina precursor preferably uses an organic alumina precursor in terms of uniform dispersion of alumina on the tantalum substrate and chemical stability. Examples of the organic alumina precursor include aluminum triisopropoxide (structure: Al(OCH(CH ₃ ) ₂ ) ₃ ), SYM-AL04 of the Institute of High Purity Chemicals, etc. .

The cerium oxide precursor can be used without particular limitation as long as it forms cerium oxide. From the viewpoint of uniformly dispersing cerium oxide on the cerium substrate and chemical stability, the cerium oxide precursor is preferably an organic cerium oxide precursor. Examples of the organic cerium oxide precursor include cerium (V) (structural formula: Nb(OC ₂ H ₅ ) ₅ , molecular weight: 318.21), and Nb-05 of the High Purity Chemical Research Institute.

A coating type material containing an organic cerium oxide precursor and an organic alumina precursor is formed into a film by a coating method or a printing method, and the organic component is removed by heat treatment (calcination) thereafter. Passivation film. Therefore, the result may also be a passivation film containing an organic component.

<Structure Description of Solar Cell Components>

The structure of the solar cell element of the present embodiment will be described with reference to Figs. 2 to 5 . 2 to 5 are cross-sectional views showing a first configuration example to a fourth configuration example of a solar battery element using a passivation film on the back surface of the embodiment.

As the tantalum substrate (crystalline germanium substrate, semiconductor substrate) 101 used in the present embodiment, any of single crystal germanium or polycrystalline germanium can be used. Further, as the tantalum substrate 101, any of a crystalline germanium having a p-type conductivity type or a crystalline germanium having a conductivity type n-type can be used. From the viewpoint of further exerting the effects of the present embodiment, it is more preferable that the conductivity type is a p-type crystal ruthenium.

In the following FIGS. 2 to 5, an example in which a p-type single crystal germanium is used as the germanium substrate 101 will be described. In addition, the single crystal germanium or polycrystalline germanium used in the germanium substrate 101 may be any, preferably having a resistivity of 0.5 Ω. Cm~10Ω. Cm single crystal germanium or polycrystalline germanium.

As shown in FIG. 2 (the first configuration example), an n-type diffusion layer 102 doped with a group V element such as phosphorus is formed on the light-receiving surface side (upper side, first surface) of the p-type germanium substrate 101. Further, a pn junction is formed between the germanium substrate 101 and the diffusion layer 102. On the surface of the diffusion layer 102, a light-receiving surface anti-reflection film 103 such as a tantalum nitride (SiN) film or a first electrode 105 (such as an electrode on the light-receiving surface side, a first surface electrode, and an upper surface) using silver (Ag) or the like is formed. Surface electrode, light receiving surface electrode). The light-receiving surface anti-reflection film 103 can also function as a light-receiving surface passivation film. By using the SiN film, both the function of the light-receiving surface anti-reflection film and the light-receiving surface passivation film can be achieved.

Further, the solar cell element of the present embodiment may have the light-receiving surface anti-reflection film 103 or may not have the light-receiving surface anti-reflection film 103. In addition, in solar cell components In order to reduce the reflectance of the surface on the light-receiving surface, it is preferable to form a concavo-convex structure (texture structure), and the solar cell element of the present embodiment may have a textured structure or may have no texture structure.

On the other hand, a back surface field (BSF) layer which is a layer doped with a group III element such as aluminum or boron is formed on the back side (the lower side, the second surface, and the back surface of the substrate) 101. 104. However, the solar cell element of the present embodiment may have the BSF layer 104 or may not have the BSF layer 104.

In order to contact (electrically connect) the BSF layer 104 (the surface on the back side of the ruthenium substrate 101 when the BSF layer 104 is not present) on the back surface side of the ruthenium substrate 101, a second layer made of aluminum or the like is formed. Electrode 106 (electrode on the back side, second surface electrode, back surface electrode).

Then, in FIG. 2 (the first configuration example), a contact region electrically connected to the second electrode 106 is provided in addition to the BSF layer 104 (the surface on the back side of the ruthenium substrate 101 when the BSF layer 104 is not present). A passivation film (passivation layer) 107 containing aluminum oxide and cerium oxide is formed in a portion other than the opening OA). The passivation film 107 of the present embodiment may have a negative fixed charge. By this fixed electric charge, electrons, which are a minority carrier in the carrier generated in the crucible substrate 101 by light, are reflected back to the surface side. Therefore, the short-circuit current is increased, and the photoelectric conversion efficiency can be expected to be improved.

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 portion OA) and the passivation film 107, and in FIG. 3 (second configuration example), only the contact is made. The second electrode 106 is formed in the region (opening OA). Can also be set as contact area The second electrode 106 is formed in a region (opening OA) and only a part of the passivation film 107. Even in the solar cell element having the configuration shown in Fig. 3, the same effects as those in Fig. 2 (the 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 on only a part of the back surface side including the contact region (the opening portion OA portion) of the second electrode 106, instead of FIG. 2 (the first configuration) Example) is formed on the entire surface on the back side. Even in the solar cell element (FIG. 4) having such a configuration, the same effects as those of FIG. 2 (the 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 is doped with a group III element such as aluminum or boron, and a region having a higher concentration than the germanium substrate 101 is doped with impurities. Photoelectric conversion efficiency higher than that of Fig. 2 (first configuration example) can be obtained.

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, and in FIG. 5 (fourth configuration example), only the contact is made. The second electrode 106 is formed in the region (opening OA). It is also possible to adopt a configuration in which the second electrode 106 is formed on only a part of the contact region (opening OA) and the passivation film 107. Even in the solar cell element having the configuration shown in FIG. 5, the same effects as those of FIG. 4 (the third configuration example) can be obtained.

In addition, when the second electrode 106 is applied by a printing method and is formed on the entire surface on the back side by firing at a high temperature, warping of the upward convexity is likely to occur during the temperature lowering process. Such warpage sometimes causes damage to the solar cell components, and the yield may be lowered. In addition, the thinning of the ruthenium substrate develops when warped The problem has become bigger. The reason for this warpage is that the second electrode 106 including a metal (for example, aluminum) has a thermal expansion coefficient larger than that of the tantalum substrate, and thus the shrinkage during the cooling process is large, so that stress is generated.

According to the above, when the second electrode 106 is not formed on the entire surface on the back side as shown in FIG. 3 (the second configuration example) and FIG. 5 (the fourth configuration example), the electrode structure is likely to be vertically symmetrical and is less likely to be generated. The stress caused by the difference in thermal expansion coefficient is therefore preferred. In this case, it is preferable to further provide a reflective layer.

<Method of Manufacturing Solar Cell Components>

Next, an example of a method of manufacturing the solar cell element (Figs. 2 to 5) of the present embodiment having the above configuration will be described. However, the present embodiment is not limited to the solar cell element produced by the method described below.

First, a texture structure is formed on the surface of the ruthenium substrate 101 shown in FIG. 2 and the like. The formation of the texture structure may be formed on both surfaces of the ruthenium substrate 101, or may be formed only on one side (the light-receiving surface side). In order to form a texture structure, the tantalum substrate 101 is first immersed in a solution of heated potassium hydroxide or sodium hydroxide to remove the damaged layer of the tantalum substrate 101. Thereafter, it is immersed in a solution containing potassium hydroxide and isopropyl alcohol as a main component, whereby a texture structure is formed on both surfaces or one side (light-receiving surface side) of the ruthenium substrate 101. Further, as described above, the solar cell element of the present embodiment may have a textured structure or a textured structure, and this step may be omitted.

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

Thereafter, a solution containing a coating type doping material such as boron or aluminum is applied to the back surface side of the tantalum substrate 101, and heat treatment is performed to form the BSF layer 104 on the back side. At the time of application, methods such as screen printing, inkjet, dispensing, and spin coating can be used. After the heat treatment, a layer such as borosilicate glass or aluminum formed on the back surface is removed by hydrofluoric acid, hydrochloric acid or the like to form the BSF layer 104. The method of forming the BSF layer 104 is not particularly limited. It is preferable that the BSF layer 104 is formed in such a manner that the concentration of boron, aluminum, or the like is in the range of 10 ¹⁸ cm ^-3 to 10 ²² cm ^-3 , and it is preferable to form the BSF layer 104 in a dot shape or a line shape. . Further, the solar cell element of the present embodiment may have the BSF layer 104 or may not have the BSF layer 104, and 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 solution of a coating-type dopant, the solution of the dopant may be applied to the substrate 101, respectively. On both sides, a phosphorus diffusion layer (n ⁺ layer) as the diffusion layer 102 is formed together with the BSF layer 104, and thereafter phosphorus glass, borosilicate glass or the like formed on the surface is removed together.

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

Then, a passivation film 107 is formed on the back side of the germanium substrate 101. The passivation film 107 contains aluminum oxide and cerium oxide, and is formed, for example, by imparting heat treatment (calcination) to a material (passivation material) containing an organic material which can be obtained by heat treatment (calcination) to obtain alumina. An alumina precursor represented by a metal decomposition coating type material and a cerium oxide precursor represented by a commercially available organometallic decomposition coating type material which can be obtained by heat treatment (calcination) to obtain cerium oxide.

The formation of the passivation film 107 can be performed, for example, as follows. The coated material was spin-coated on a single side of a 8 吋 (20.32 cm) p-type ruthenium substrate (8 Ω cm to 12 Ω cm) having a thickness of 725 μm in which the natural oxide film was 725 μm, which was previously removed by using hydrofluoric acid having a concentration of 0.049% by mass. The prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment was performed at 650 ° C for 1 hour under a nitrogen atmosphere. In this case, a passivation film containing aluminum oxide and cerium oxide can be obtained. The film thickness of the passivation film 107 formed by the method described above by an ellipsometer is usually about several tens of nanometers (nm).

The coating type material is imparted to the contact-containing region by screen printing, pattern printing, printing by inkjet, printing by a dispenser, or the like (opening) Part OA) on the established pattern. Further, it is preferable that the coating material is prebaked in a range of from 80 ° C to 180 ° C after the application, and the solvent is evaporated, and then subjected to a nitrogen atmosphere or air at 600 ° C to 1000 ° C for 30 minutes. Heat treatment (annealing) for about 3 hours to form a passivation film 107 (film of an oxide).

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

The passivation film 107 used in the above solar cell element preferably has a mass ratio of cerium oxide to aluminum oxide (yttria/alumina) of 30/70 to 90/10, more preferably 30/70 to 80/20, and further preferably It is 35/65~70/30. Thereby, the negative fixed charge can be stabilized. Further, from the viewpoint of improving the life of the carrier and the negative fixed charge, the mass ratio of cerium oxide to aluminum oxide is preferably 50/50 to 90/10.

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

Then, 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 containing silver (Ag) as a main component on the light-receiving surface anti-reflection film 103 by screen printing, and performing heat treatment (burn-through). The shape of the first electrode 105 may be any shape, and may be, for example, a well-known shape including a finger electrode and a bus bar electrode.

Then, the second electrode 106 which is an electrode on the back side is formed. The second electrode 106 is formed by applying a paste containing aluminum as a main component using a screen printing or a dispenser, and heat-treating the same. Further, the shape of the second electrode 106 is preferably the same shape as that of the BSF layer 104, and covers the entire surface on the back side. Shape, comb shape, lattice shape, and the like. In addition, printing of the paste for forming the first electrode 105 and the second electrode 106 as electrodes on the light-receiving surface side may be performed first, and then heat treatment (burn-through) may be performed to form the first electrode 105 and the second electrode together. Electrode 106.

Further, when the second electrode 106 is formed, aluminum is diffused as a dopant by using a paste containing aluminum (Al) as a main component, and the contact portion between the second electrode 106 and the ruthenium substrate 101 is self-aligned. A BSF layer 104 is formed. Further, as described above, a solution containing a coating type doping material such as boron or aluminum may be applied to the back surface side of the tantalum substrate 101, and heat-treated to form the BSF layer 104.

Further, the above shows a configuration example and a manufacturing example in which a p-type germanium is used for the germanium substrate 101, and an n-type germanium substrate can be used as the germanium 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. In this case, it is necessary to pay attention to the fact that the negative electrode formed on the interface and the portion in contact with the metal on the back side communicate with each other and the leakage current flows, and the conversion efficiency is hard to be improved.

Further, in the case of using an n-type germanium substrate, the passivation film 107 containing cerium oxide and aluminum oxide can be used for the light-receiving surface side as shown in Fig. 6 . FIG. 6 is a cross-sectional view showing a configuration example of a solar cell element using the light-receiving surface passivation film of the embodiment.

In this case, the diffusion layer 102 on the light-receiving surface side is doped with boron to form a p-type, and the holes in the generated carriers are collected on the light-receiving surface side, and electrons are collected on the back surface side. Therefore, it is preferable that the passivation film 107 having a negative fixed charge is located on the light receiving surface side.

An antireflection film made of SiN or the like may be further formed on the passivation film containing cerium oxide and aluminum oxide by CVD or the like.

Hereinafter, the reference embodiment and the reference comparative example of the present embodiment will be described in detail.

[Reference Example 1-1]

A commercially available organometallic decomposition coating material which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [SYM-AL04 of High Purity Chemical Research Institute Co., Ltd., concentration: 2.3% by mass] 3.0 g, a commercially available organometallic decomposition coating material which can obtain cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [Nb-05 of High Purity Chemical Research Institute Co., Ltd., concentration: 5% by mass ] 3.0 g was mixed to prepare a passivation material (a-1) as a coating type material.

The passivation material (a-1) was spin-coated on a single surface of an 8-inch p-type tantalum substrate (8 Ωcm to 12 Ωcm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.049% by mass. Prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was carried out at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing alumina and cerium oxide [cerium oxide/alumina = 68/32 (mass ratio)]. The film thickness was measured by an ellipsometer and found to be 43 nm. The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition in the metal mask to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to +0.32V. From the amount of movement, it was found that the passivation film obtained from the passivation material (a-1) showed a fixed charge having a fixed charge density (Nf) of -7.4 × 10 ¹¹ cm ^-2 and a negative value.

In the same manner as described above, the passivation material (a-1) was applied to both surfaces of a p-type ruthenium substrate of 8 Å, prebaked, and heat-treated (calcined) at 650 ° C for 1 hour in a nitrogen atmosphere to prepare a ruthenium substrate. A sample covered on both sides by a passivation film. The measurement of the carrier lifetime of these samples was carried out by a life measuring device (Kobelco Research Institute Co., Ltd., RTA-540). The resulting carrier lifetime was 530 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by subjecting the passivation material (a-1) to heat treatment (calcination) exhibits a certain degree of passivation performance and exhibits a negative fixed charge.

[Reference Example 1-2]

In the same manner as in Reference Example 1-1, a commercially available organometallic decomposition coating material which can be obtained by heat treatment (calcination) of alumina (Al ₂ O ₃ ) [High Purity Chemical Research Institute Co., Ltd., SYM -AL04, a concentration of 2.3% by mass], and a commercially available organometallic decomposition coating material capable of obtaining cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute Co., Ltd., Nb -05, the concentration was 5% by mass], and the ratio was changed and mixed, and the passivation material (a-2) to passivation material (a-7) shown in Table 2 was prepared.

Passivation material (a-2) to passivation material as in Reference Example 1-1 (a-7) was applied to one surface of the p-type germanium substrate, and heat-treated (calcined) to prepare a passivation film. The voltage dependence of the capacitance of the obtained passivation film was measured, and the fixed charge density was calculated based on this.

Further, in the same manner as in Reference Example 1-1, a passivation material was applied to both surfaces of the p-type ruthenium substrate, and heat treatment (calcination) was performed, and the obtained sample was used to measure the carrier lifetime. The results obtained are summarized in Table 2.

Depending on the ratio (mass ratio) of cerium oxide/alumina after heat treatment (calcination), the results are different, but regarding the passivation material (a-2) to passivation material (a-7), the carrier life after heat treatment (calcination) It also shows a certain degree of value, so it is suggested to function as a passivation film. It is known that the passivation film obtained from the passivation material (a-2) to the passivation material (a-7) stably exhibits a negative fixed charge, and can also be preferably used as a passivation film of a p-type germanium substrate.

[Reference Example 1-3]

Commercially available ruthenium (V) (structural formula: Nb(OC ₂ H ₅ ) ₅ , molecular weight: 318.21) 3.18 g (0.010 mol), commercially available aluminum triisopropoxide (structural formula: Al (OCH (CH) ₃ ) ₂ ) ₃ , molecular weight: 204.25) 1.02 g (0.005 mol) was dissolved in 80 g of cyclohexane to prepare a passivation material (c-1) having a concentration of 5 mass%.

The passivation material (c-1) was spin-coated on a single surface of an 8-inch p-type tantalum substrate (8 Ωcm to 12 Ωcm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.049% by mass. Prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 600 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The film thickness was measured by an ellipsometer and found to be 50 nm. As a result of performing elemental analysis, it was found that Nb/Al/C = 81/14/5 (% by mass). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition in the metal mask to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to +4.7V. From the amount of movement, it was found that the passivation film obtained from the passivation material (c-1) exhibited a fixed charge having a fixed charge density (Nf) of -3.2 × 10 ¹² cm ^-2 and a negative value.

In the same manner as described above, the passivation material (c-1) was applied to both surfaces of a p-type ruthenium substrate of 8 Å, prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare a ruthenium substrate. A sample covered by a passivation film on both sides. The measurement of the carrier lifetime of these samples was carried out by a life measuring device (Kobelco Research Institute Co., Ltd., RTA-540). The resulting carrier lifetime was 330 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by subjecting the passivation material (c-1) to heat treatment (calcination) exhibits a certain degree of passivation performance and exhibits a negative fixed charge.

[Reference Examples 1-4]

Commercially available ruthenium (V) (structural formula: Nb(OC ₂ H ₅ ) ₅ , molecular weight: 318.21) 2.35 g (0.0075 mol), commercially available aluminum triisopropoxide (structural formula: Al (OCH (CH) ₃ ) ₂ ) ₃ , molecular weight: 204.25) 1.02 g (0.005 mol), 10 g of novolak resin was dissolved in 10 g of diethylene glycol monobutyl ether acetate and 10 g of cyclohexane to prepare a passivation material (c-2).

The passivation material (c-2) was spin-coated on a single surface of an 8-inch p-type ruthenium substrate (8 Ωcm to 12 Ωcm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.049% by mass. Prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 600 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The film thickness was measured by an ellipsometer and found to be 14 nm. As a result of elemental analysis, Nb/Al/C = 75/17/8 (% by mass) was obtained. The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition through a metal mask to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to +0.10V. From the amount of movement, it was found that the passivation film obtained from the passivation material (c-2) showed a fixed charge having a fixed charge density (Nf) of -0.8 × 10 ¹¹ cm ^-2 and a negative value.

In the same manner as described above, the passivation material (c-1) was applied to both surfaces of a p-type ruthenium substrate of 8 Å, prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare a ruthenium substrate. A sample covered by a passivation film on both sides. The measurement of the carrier lifetime of the sample was carried out by a life measuring device (Kobelco Research Institute Co., Ltd., RTA-540). The resulting carrier lifetime was 200 μs. For comparison, the same 8 吋 p is obtained by iodine passivation. The ruthenium substrate was passivated and measured, and the carrier lifetime was 1100 μs.

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

[Reference Examples 1-5 and Reference Comparative Example 1-1]

In the same manner as in Reference Example 1-1, a commercially available organometallic decomposition coating material which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [SYM of High Purity Chemical Research Institute Co., Ltd.] -AL04, a concentration of 2.3% by mass], and a commercially available organometallic decomposition coating material capable of obtaining cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [Nb of High Purity Chemical Research Institute Co., Ltd. -05, a concentration of 5% by mass] was mixed and changed, and the passivation material (b-1) to passivation material (b-7) shown in Table 3 was prepared.

In the same manner as in Reference Example 1-1, the passivation material (b-1) to the passivation material (b-7) were respectively applied to one surface of the p-type germanium substrate, and heat treatment (calcination) was performed to prepare a passivation film. The passivation film measures the voltage dependence of the electrostatic capacitance, and calculates the fixed charge density based on this.

Further, in the same manner as in Reference Example 1-1, a passivation material (coating type material) was applied to both surfaces of the p-type ruthenium substrate, and the carrier life was measured using the cured sample. The results obtained are summarized in Table 3.

It is known that the passivation film obtained from the passivation material (b-1) to the passivation material (b-6) has a large carrier life and functions as a passivation. Further, in the case where the cerium oxide/alumina is 10/90 and 20/80, the value of the fixed charge density is largely deviated, and the negative fixed charge density cannot be stably obtained, but it can be confirmed that alumina and cerium oxide can be used. Achieve a negative fixed charge density. It has been found that when a passivation material having yttria/alumina of 10/90 and 20/80 is used for measurement by the CV method, it may become a passivation film which exhibits a positive fixed charge, and thus does not stably exhibit a negative fixation. Charge. Further, a passivation film exhibiting a positive fixed charge can be used as a passivation film of an n-type germanium substrate. On the other hand, the passivation material (b-7) in which the alumina reaches 100% by mass cannot obtain a negative fixed charge density.

[Reference Comparative Example 1-2]

A commercially available organometallic decomposition coating material which can be obtained as a passivation material (d-1) by heat treatment (calcination) to obtain titanium oxide (TiO ₂ ) [Ti-03- of High Purity Chemical Research Institute Co., Ltd. P, a concentration of 3% by mass], a commercially available organometallic decomposition coating material capable of obtaining barium titanate (BaTiO ₃ ) by heat treatment (calcination) as a passivation material (d-2) [High Purity Chemistry Research] BT-06 of the company, a concentration of 6% by mass], and commercially available organometallic decomposition coating of lanthanum oxide (HfO ₂ ) which can be obtained by heat treatment (calcination) as a passivation material (d-3) Type material [Hf-05 of High Purity Chemical Research Institute Co., Ltd., concentration of 5% by mass].

In the same manner as in Reference Example 1-1, the passivation material (d-1) to the passivation material (d-3) were respectively applied to one surface of the p-type germanium substrate, and then heat treatment (calcination) was performed to prepare a passivation film. The passivation film measures the voltage dependence of the electrostatic capacitance, and calculates the fixed charge density based on this.

Further, in the same manner as in Reference Example 1-1, a passivation material was applied to both surfaces of the p-type ruthenium substrate, and a sample obtained by heat treatment (calcination) was used to measure the carrier lifetime. The results obtained are summarized in Table 4.

It is known that the passivation film obtained from the passivation material (d-1) to the passivation material (d-3) has a small carrier lifetime, and the function of passivation is insufficient. In addition, a positive fixed charge is shown. The passivation film obtained from the passivation material (d-3) has a negative fixed charge, but its value is small. In addition, the carrier lifetime is relatively small, and the function of passivation is insufficient.

[Reference Examples 1-6]

A solar cell element having the structure shown in Fig. 4 was produced by using a single crystal germanium substrate doped with boron as the germanium substrate 101. After the surface of the ruthenium substrate 101 is subjected to a texture treatment, a coating-type phosphorus diffusion material is applied to the light-receiving surface side, and a diffusion layer 102 (phosphorus diffusion layer) is formed by heat treatment. Thereafter, the coated phosphorus diffusion material was removed using dilute hydrofluoric acid.

Then, an SiN film formed by plasma CVD is formed on the light-receiving surface side as the light-receiving surface anti-reflection film 103. Thereafter, the passivation material (a-1) prepared in Reference Example 1-1 was applied to a region other than the contact region (opening portion OA) in the back surface side of the ruthenium substrate 101 by an inkjet method. Thereafter, heat treatment is performed to form a passivation film 107 having an opening OA.

Further, as the passivation film 107, a sample using the passivation material (c-1) prepared in Reference Example 1-3 was also prepared.

Then, on the light-receiving surface anti-reflection film 103 (SiN film) formed on the light-receiving surface side of the ruthenium substrate 101, a paste containing silver as a main component is screen-printed in the shape of a predetermined finger electrode and a bus bar electrode. On the back side, a paste with aluminum as a main component was screen printed onto the entire surface. Thereafter, heat treatment (burn-through) was performed at 850 ° C to form electrodes (first electrode 105 and second electrode 106), and aluminum was diffused into a portion of the opening OA of the back surface to form a BSF layer 104, and FIG. 4 was formed. The solar cell element of the structure shown.

In the silver electrode of the light-receiving surface, a burn-through step that does not open a hole in the SiN film is described. However, the opening portion OA may be formed in advance in the SiN film by etching or the like, and then a silver electrode may be formed.

For comparison, in the above-described fabrication step, the formation of the passivation film 107 is performed, and the aluminum paste is printed on the entire surface on the back side, and the p ⁺ layer 114 and the second electrode corresponding to the BSF layer 104 are formed on the entire surface. The corresponding electrode 116 forms a solar cell element of the structure shown in Fig. 1. The solar cell elements were evaluated for characteristics (short circuit current, open circuit voltage, curve factor, and conversion efficiency). The evaluation of the characteristics was carried out in accordance with JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 5.

As shown in Table 5, the solar cell element having the passivation film 107 containing the yttrium oxide and the aluminum oxide layer has an increase in the short-circuit current and the open circuit voltage, and the conversion efficiency (photoelectric conversion efficiency) is the largest as compared with the solar cell element having no passivation film 107. Increase by 1%.

<Reference Embodiment 2>

The following is a passivation film, a coating material, a solar cell element, and a tantalum substrate with a passivation film according to the second embodiment.

<1> A passivation film containing an oxide of at least one vanadium element selected from the group consisting of vanadium oxide and cerium oxide, and is used for In a solar cell element with a germanium substrate.

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

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

The passivation film according to any one of <1> to <3> containing an oxide of two or three kinds of vanadium elements selected from the group consisting of vanadium oxide, cerium oxide and cerium oxide. It is an oxide of the above-mentioned vanadium group element.

The passivation film according to any one of <1> to <4> which is a heat-treated material of a coating material containing a precursor of alumina and a precursor selected from vanadium oxide. A precursor of an oxide of at least one vanadium element in the group consisting of precursors of cerium oxide and cerium oxide.

<6> a coating type material comprising a precursor of an alumina, a precursor of an oxide of at least one vanadium element selected from the group consisting of a precursor of vanadium oxide and a precursor of cerium oxide, and It is a passivation film for forming a solar cell element having a germanium substrate.

<7> A solar cell element comprising: a p-type germanium substrate; an n-type impurity diffusion layer formed on a first surface side as a light-receiving surface side of the germanium substrate; and a first electrode formed on the impurity diffusion On the floor a passivation film formed on the second surface side opposite to the light-receiving surface side of the ruthenium substrate and having an opening; and a second electrode formed on the second surface side of the ruthenium substrate and passing through the passivation film The opening portion is electrically connected to the second surface side of the ruthenium substrate; and the passivation film contains alumina and an oxide of at least one vanadium group element selected from the group consisting of vanadium oxide and ruthenium oxide.

<8> The solar cell element according to <7>, which has a p-type impurity diffusion layer formed on a part or all of the second surface side of the tantalum substrate, and is larger than the tantalum substrate Impurities are added to a higher concentration, and the second electrode is electrically connected to the p-type impurity diffusion layer through an opening of the passivation film.

<9> A solar cell element comprising: an n-type germanium substrate; a p-type impurity diffusion layer formed on a first surface side as a light-receiving surface side of the germanium substrate; and a first electrode formed on the impurity diffusion a passivation film formed on the second surface side opposite to the light-receiving surface side of the ruthenium substrate and having an opening; and a second electrode formed on the second surface side of the ruthenium substrate and via The opening of the passivation film is electrically connected to the second surface side of the tantalum substrate; and the passivation film contains alumina and an oxide of at least one vanadium element selected from the group consisting of vanadium oxide and niobium oxide. .

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

The solar cell element according to any one of the above aspects, wherein the mass ratio of the oxide of the vanadium group element to the aluminum oxide in the passivation film is 30/70 to 90/10.

The solar cell element according to any one of the above aspects of the present invention, wherein the total content of the oxide of the vanadium group element and the aluminum oxide of the passivation film is 90% or more.

The solar cell element according to any one of <7> to <12> containing oxidation of two or three kinds of vanadium elements selected from the group consisting of vanadium oxide, cerium oxide and cerium oxide. The substance acts as an oxide of the above vanadium group element.

<14> A solar cell element according to any one of <1> to <5>, wherein: Passivation film.

According to the above-described reference embodiment, the passivation film which has a carrier life of the ruthenium substrate and has a negative fixed charge can be realized at 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, it can be implemented at low cost. A germanium substrate with a passivation film having a negative carrier lifetime and a negative fixed charge is now available.

The passivation film of the present embodiment is a passivation film used in a tantalum solar cell element, and contains an oxide of at least one vanadium group element selected from the group consisting of alumina oxide and cerium oxide.

Further, in the present embodiment, the amount of the fixed charge which the passivation film has can be controlled by changing the composition of the passivation film. Here, the vanadium group element refers to a group 5 element of the periodic table of elements, and is an element selected from the group consisting of vanadium, niobium and tantalum.

Further, from the viewpoint of stabilizing the negative fixed charge, the mass ratio of the oxide of the vanadium element to the alumina is preferably 35/65 to 90/10, and more preferably 50/50 to 90/10.

The mass ratio of the oxide of the vanadium group element to the aluminum oxide in the passivation film can be determined by energy dispersive X-ray spectroscopy (EDX), secondary ion mass spectrometry (SIMS), and high frequency inductively coupled plasma mass spectrometry ( ICP-MS) to determine. The specific measurement conditions are as follows, for example, in the case of ICP-MS. Dissolving the passivation film in an acid or alkaline aqueous solution, forming the solution into a mist and introducing it into the Ar plasma, and splitting the light emitted by the excited element back to the ground state to measure the wavelength and intensity, according to the obtained The wavelength is used to characterize the element, and the amount is quantified based on the obtained intensity.

The total content of the oxide of the vanadium group element and the 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 oxide of the vanadium group element and the components other than the alumina in the passivation film are increased, the effect of negatively fixing the charge becomes large.

Further, in the passivation film, from the viewpoint of improving the film quality and adjusting the elastic modulus, an oxide other than a vanadium element and a component other than alumina can be contained as an organic component. The presence of the organic component in the passivation film can be confirmed by elemental analysis and Fourier transform infrared spectroscopy (FT-IR) measurement of the film.

From the viewpoint of obtaining a larger negative fixed charge, the oxide of the above-mentioned vanadium element is preferably selected from vanadium oxide (V ₂ O ₅ ).

The passivation film may further contain an oxide of two or three kinds of vanadium elements selected from the group consisting of vanadium oxide, cerium oxide, and cerium oxide as an oxide of a vanadium group element.

The passivation film is preferably obtained by heat-treating a coating type material, and is more preferably obtained by coating a coating type material by a coating method or a printing method, and thereafter by heat treatment. Organic ingredients are removed. That is, the passivation film can also be obtained as a heat-treated product of a coating material containing a precursor of an oxide of an alumina precursor and an oxide of a vanadium group. The details of the coating material will be described later.

The coating material of the present embodiment is a coating material used for a passivation film for a solar cell element having a ruthenium substrate, and contains a precursor of alumina and a precursor selected from a precursor of vanadium oxide and ruthenium oxide. A precursor of an oxide of at least one vanadium element in the group formed. From the viewpoint of the negative fixed charge of the passivation film formed of the coating material, the precursor of the oxide of the vanadium element contained in the coating type material is preferably a precursor of selecting vanadium oxide (V ₂ O ₅ ). . The coating material may also contain a precursor of an oxide of two or three kinds of vanadium elements selected from the group consisting of a precursor of vanadium oxide, a precursor of cerium oxide, and a precursor of cerium oxide as a vanadium group. The precursor of the oxide of the element.

The alumina precursor can be used without particular limitation as long as it forms alumina. From the viewpoint of uniformly dispersing alumina on the ruthenium substrate and chemical stability, the alumina precursor is preferably an organic alumina precursor. Examples of the organic alumina precursors include aluminum triisopropoxide (structural formula: Al(OCH(CH ₃ ) ₂ ) ₃ ), and SYM-AL04 of the Institute of High Purity Chemicals.

The precursor of the oxide of the vanadium group element can be used without particular limitation as long as it forms an oxide of a vanadium group element. The precursor of the oxide of the vanadium group element is preferably a precursor of an oxide of an organic vanadium group element from the viewpoint of uniformly dispersing the alumina on the tantalum substrate and chemical stability.

Examples of the organic vanadium oxide precursor include vanadium oxyacetate (V) (structural formula: VO(OC ₂ H ₅ ) ₃ , molecular weight: 202.13), and V- of the High Purity Chemical Research Institute (share). 02. Examples of the precursor of the organic cerium oxide include methanol oxime (V) (structural formula: Ta(OCH ₃ ) ₅ , molecular weight: 336.12), and Ta-10-P of the High Purity Chemical Research Institute. Examples of the organic cerium oxide precursor include cerium (V) (structural formula: Nb(OC ₂ H ₅ ) ₅ , molecular weight: 318.21), and Nb-05 of the High Purity Chemical Research Institute.

A coating material containing an organic oxide-containing vanadium element oxide precursor and an organic alumina precursor coating film is formed by a coating method or a printing method, and the organic component is removed by heat treatment thereafter. This gives a passivation film. Therefore, the passivation film can also be a passivation film containing an organic component. Passive film of organic components The content is preferably less than 10% by mass, more preferably 5% by mass or less, and still more preferably 1% by mass or less.

The solar cell element (photoelectric conversion device) of the present embodiment has the passivation film (insulating film, protective insulating film) described in the above embodiment in the vicinity of the photoelectric conversion interface of the germanium substrate, that is, contains alumina and is selected from vanadium oxide. And a film of an oxide of at least one vanadium element in the group consisting of cerium oxide. By using an oxide containing at least one vanadium element selected from the group consisting of alumina and vanadium oxide and cerium oxide, the carrier life of the ruthenium substrate can be extended and a negative fixed charge can be obtained, thereby improving solar cell elements. Characteristics (photoelectric conversion efficiency).

The description of the structure and the manufacturing method of the solar cell element of the present embodiment can be referred to the description of the structure and the manufacturing method of the solar cell element according to the first embodiment.

Hereinafter, the reference embodiment and the reference comparative example of the present embodiment will be described in detail.

<Case of using vanadium oxide as an oxide of a vanadium group element> [Reference Example 2-1]

A commercially available organometallic thin film coating type material which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) [High Purity Chemical Research Institute, SYM-AL04, concentration: 2.3% by mass] 3.0 g, a commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V-02, concentration 2% by mass ] 6.0 g of a mixture was used to prepare a passivation material (a2-1) as a coating type material.

The passivation material (a2-1) was spin-coated on a 8-inch p-type tantalum substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, it was placed on a hot plate and prebaked at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 700 ° C for 30 minutes in a nitrogen atmosphere to obtain a passivation film containing alumina and vanadium oxide [vanadium oxide / alumina = 63 / 37 (% by mass)]. The film thickness was measured by an ellipsometer and found to be 51 nm. The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to +0.02V. From the amount of movement, it was found that the passivation film obtained from the passivation material (a2-1) exhibited a fixed charge having a fixed charge density (Nf) of -5.2 × 10 ¹¹ cm ^-2 and a negative value.

In the same manner as described above, the passivation material (a2-1) was applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and heat-treated (calcined) at 650 ° C for 1 hour in a nitrogen atmosphere to prepare ruthenium. A sample covered by a passivation film on both sides of the substrate. The carrier life of the sample was determined by a life measuring device (Kobelco Research Institute, RTA-540). The resulting carrier lifetime was 400 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs. In addition, after making the sample, After 14 days, the carrier lifetime was measured again, and the resulting carrier lifetime was 380 μs. From this, it was found that the decrease in carrier lifetime (400 μs to 380 μs) was within -10%, and the decrease in carrier lifetime was small.

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

[Reference Example 2-2]

In the same manner as in Reference Example 2-1, a commercially available organometallic thin film coating type material (High Purity Chemical Research Institute, SYM) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) is used. -AL04, a concentration of 2.3% by mass], and a commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment [High Purity Chemical Research Institute, V-02, The passivation material (a2-2) to the passivation material (a2-7) shown in Table 6 were prepared by mixing at a concentration of 2% by mass.

In the same manner as in Reference Example 2-1, the passivation material (a2-2) to the passivation material (a2-7) were respectively applied onto one surface of the p-type germanium substrate, and heat-treated (calcined) to prepare a passivation film. The voltage dependence of the capacitance of the obtained passivation film was measured, and the fixed charge density was calculated based on this.

Then, a passivation material was applied onto both surfaces of the p-type ruthenium substrate in the same manner as in Reference Example 2-1, and heat treatment (calcination) was performed, and the obtained sample was used to measure the carrier lifetime.

The results obtained are summarized in Table 6. In addition, after 14 days from the preparation of the sample, the carrier life was measured again, and the use of the passivation material (a2-2) shown in Table 6 was obtained. ~ The passivation film of the passivation material (a2-7) has a carrier life reduction of -10% or less, and the carrier lifetime is reduced.

Depending on the ratio (mass ratio) of vanadium oxide/alumina after heat treatment (calcination), the results are different, but the passivation material (a2-2) to passivation material (a2-7) show a negative fixation after heat treatment (calcination). The charge and carrier lifetime also show a certain degree of value, so it is suggested to function as a passivation film. It is known that the passivation film obtained from the passivation material (a2-2) to the passivation material (a2-7) stably exhibits a negative fixed charge, and can also be preferably used as a passivation film of a p-type germanium substrate.

[Reference Example 2-3]

Commercially available vanadium oxyacetate (V) as a compound which can be obtained by heat treatment (calcination) to obtain vanadium oxide (V ₂ O ₅ ) (structural formula: VO(OC ₂ H ₅ ) ₃ , molecular weight: 202.13) 1.02 g (0.010 mol), and commercially available aluminum triisopropoxide as a compound which can be obtained by heat treatment (calcination) to obtain alumina (Al ₂ O ₃ ) (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 (b2-1) having a concentration of 5 mass%.

The passivation material (b2-1) was spin-coated on a 8-inch p-type tantalum substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and vanadium oxide. The film thickness was measured by an ellipsometer and found to be 60 nm. As a result of elemental analysis, it was found that V/Al/C = 64/33/3 (% by mass). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to +0.10V. From the amount of movement, it was found that the passivation film obtained from the passivation material (b2-1) showed a fixed charge having a fixed charge density (Nf) of -6.2 × 10 ¹¹ cm ^-2 and a negative value.

The passivation material (b2-1) was applied to both surfaces of a 8-inch p-type tantalum substrate in the same manner as described above, prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare a crucible. A sample covered by a passivation film on both sides of the substrate. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540). Result carrier lifetime It is 400μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by subjecting the passivation material (b2-1) to heat treatment (calcination) exhibits a certain degree of passivation performance and exhibits a negative fixed charge.

[Reference Example 2-4]

Commercially available vanadium oxyacetate (V) (structural formula: VO(OC ₂ H ₅ ) ₃ , molecular weight: 202.13) 1.52 g (0.0075 mol), commercially available aluminum triisopropoxide (structural formula: Al ( OCH(CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) 1.02g (0.005mol), and 10g of novolak resin were dissolved in 10g of diethylene glycol monobutyl ether acetate and 10g of cyclohexane to prepare passivation material (b2) -2).

The passivation material (b2-2) was spin-coated on a 8-inch p-type tantalum substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, it was placed on a hot plate and prebaked at 120 ° C for 3 minutes. Thereafter, the film was heated at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and vanadium oxide. The film thickness was measured by an ellipsometer and found to be 22 nm. As a result of elemental analysis, it was found that V/Al/C = 71/22/7 (% by mass). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to +0.03V. From the amount of movement, it was found that the passivation film obtained from the passivation material (b2-2) exhibited a fixed charge having a fixed charge density (Nf) of -2.0 × 10 ¹¹ cm ^-2 and a negative value.

In the same manner as described above, the passivation material (b2-2) was applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare ruthenium. A sample covered by a passivation film on both sides of the substrate. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540). The resulting carrier lifetime was 170 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by hardening the passivation material (b2-2) exhibits a certain degree of passivation performance and exhibits a negative fixed charge.

<Case of using cerium oxide as an oxide of a vanadium group element> [Reference Example 2-5]

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A ratio of change in a commercially available organometallic thin film coating type material (high purity chemical research institute, Ta-10-P, concentration: 10% by mass) which can be obtained by heat treatment to obtain cerium oxide (Ta ₂ O ₅ ) While mixing, the passivation material (c2-1) to passivation material (c2-6) shown in Table 7 was prepared.

The passivation material (c2-1) to the passivation material (c2-6) were spin-coated on the 8-inch p-type germanium substrate having a thickness of 725 μm in which the natural oxide film was removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance ( One side of 8 Ω.cm~12 Ω.cm) was placed on a hot plate and pre-baked at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 700 ° C for 30 minutes in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The passivation film was used to measure the voltage dependence of the electrostatic capacitance, and the fixed charge density was calculated based on this.

Then, the passivation material (c2-1) to the passivation material (c2-6) were respectively applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and subjected to a nitrogen atmosphere at 650 ° C for 1 hour. Heat treatment (calcination), and a sample covered with a passivation film on both sides of the tantalum substrate was prepared. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540).

The results obtained are summarized in Table 7. Further, after 14 days from the preparation of the sample, the carrier life was measured again, and as a result, it was found that the carrier life of the passivation film using the passivation material (c2-1) to the passivation material (c2-6) shown in Table 7 was lowered. Within -10%, the decrease in carrier lifetime is small.

Depending on the ratio (mass ratio) of cerium oxide/alumina after heat treatment (calcination), the results are different, but the passivation material (c2-1) to passivation material (c2-6) show negative fixation after heat treatment (calcination). The charge and carrier lifetime also show a certain degree of value, so it is suggested to function as a passivation film.

[Reference Example 2-6]

Commercially available methanol oxime (V) (structure: Ta(OCH ₃ ) ₅ , molecular weight: 336.12) 1.18 g (0.0025 mol) as a compound capable of obtaining cerium oxide (Ta ₂ O ₅ ) by heat treatment (calcination) And commercially available aluminum triisopropoxide as a compound which can be obtained by heat treatment (calcination) to obtain alumina (Al ₂ O ₃ ) (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 mass%.

The passivation material (d2-1) was spin-coated on a 8-inch p-type tantalum substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, it was placed on a hot plate and prebaked at 120 ° C for 3 minutes. Thereafter, the film was heated at 700 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The film thickness was measured by an ellipsometer and found to be 40 nm. As a result of elemental analysis, it was found that Ta/Al/C = 75/22/3 (wt%). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to -0.30V. From the amount of movement, it was found that the passivation film obtained from the passivation material (d2-1) showed a fixed charge having a fixed charge density (Nf) of -6.2 × 10 ¹⁰ cm ^-2 and a negative value.

In the same manner as described above, the passivation material (d2-1) was applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and heat-treated (calcined) at 600 ° C for 1 hour in a nitrogen atmosphere to prepare ruthenium. A sample covered by a passivation film on both sides of the substrate. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540). The resulting carrier lifetime was 610 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

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

[Reference Examples 2-7]

Commercially available methanol oxime (V) (structure: Ta(OCH ₃ ) ₅ , molecular weight: 336.12) 1.18 g (0.005 mol) as a compound capable of obtaining cerium oxide (Ta ₂ O ₅ ) by heat treatment (calcination) , commercially available aluminum triisopropoxide as a compound which can be obtained by heat treatment (calcination) to obtain alumina (Al ₂ O ₃ ) (structural formula: Al(OCH(CH ₃ ) ₂ ) ₃ , molecular weight: 204.25) 1.02 g (0.005 mol) and 10 g of a 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).

The passivation material (d2-2) was spin-coated on a 8-inch p-type ruthenium substrate (8 Ω.cm to 12 Ω.cm) having a thickness of 725 μm of a natural oxide film removed by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side, prebaking was carried out on a hot plate at 120 ° C for 3 minutes. Thereafter, the film was heated at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing aluminum oxide and cerium oxide. The film thickness was measured by an ellipsometer and found to be 18 nm. As a result of elemental analysis, it was found that Ta/Al/C = 72/20/8 (wt%). The FT-IR of the passivation film was measured, and as a result, a very weak peak derived from an alkyl group was observed in the vicinity of 1200 cm ^-1 .

Then, on the passivation film, a plurality of aluminum electrodes having a diameter of 1 mm were formed by vapor deposition to form a capacitor of a metal-insulator-semiconductor (MIS) structure. The voltage dependence (CV characteristic) of the capacitance of the capacitor was measured by a commercially available prober and an LCR meter (HP company, 4275A). The results show that the flat band voltage (Vfb) is shifted from the ideal value of -0.81V to -0.43V. From the amount of movement, it was found that the passivation film obtained from the passivation material (d-2) showed a fixed charge having a fixed charge density (Nf) of -5.5 × 10 ¹⁰ cm ^-2 and a negative value.

The passivation material (d2-1) was applied to both surfaces of a 8 Å p-type ruthenium substrate in the same manner as above, prebaked, and subjected to a nitrogen atmosphere at 600 ° C for 1 hour. The heat treatment (calcination) was performed to prepare a sample covered by a passivation film on both sides of the tantalum substrate. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540). The resulting carrier lifetime was 250 μs. For comparison, the same 8-inch p-type ruthenium substrate was passivated and measured by iodine passivation, and the carrier lifetime was 1100 μs.

From the above, it is known that the passivation film obtained by subjecting the passivation material (d2-2) to heat treatment (calcination) exhibits a certain degree of passivation performance and exhibits a negative fixed charge.

<Case of using two or more oxides of vanadium elements> [Reference Example 2-8]

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V-02, concentration: 2% by mass], and A commercially available organometallic thin film coating type material obtained by heat treatment (calcination) of lanthanum oxide (Ta ₂ O ₅ ) [High Purity Chemical Research Institute, Ta-10-P, concentration: 10% by mass] The passivation material (e2-1) as a coating type material was prepared by mixing (refer to Table 8).

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V-02, concentration: 2% by mass], and A commercially available organometallic thin film coating type material (high purity chemical research institute, Nb-05, concentration: 5% by mass) which can obtain cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination), A passivation material (e2-2) as a coating type material was prepared (refer to Table 8).

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A commercially available organometallic thin film coating type material obtained by heat treatment (calcination) of lanthanum oxide (Ta ₂ O ₅ ) [High Purity Chemical Research Institute, Ta-10-P, concentration: 10% by mass] And a commercially available organometallic thin film coating type material which can obtain cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, Nb-05, concentration: 5% by mass] The passivation material (e2-3) as a coating type material was prepared by mixing (refer to Table 8).

A commercially available organometallic thin film coating type material (high purity chemical research institute, SYM-AL04, concentration: 2.3% by mass) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination), A commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V-02, concentration: 2% by mass], A commercially available organometallic thin film coating type material obtained by heat treatment (calcination) of lanthanum oxide (Ta ₂ O ₅ ) [High Purity Chemical Research Institute, Ta-10-P, concentration: 10% by mass], And a commercially available organometallic thin film coating type material (high purity chemical research institute, Nb-05, concentration: 5% by mass) which can obtain cerium oxide (Nb ₂ O ₅ ) by heat treatment (calcination) A passivation material (e2-4) as a coating type material was prepared (refer to Table 8).

The passivation material (e2-1) to the passivation material (e2-4) were spin-coated in the same manner as in Reference Example 2-1, respectively, and the thickness of the natural oxide film was 725 μm by using hydrofluoric acid having a concentration of 0.49% by mass in advance. On one side of a 8 inch p-type ruthenium substrate (8 Ω.cm to 12 Ω.cm), it was placed on a hot plate and prebaked at 120 ° C for 3 minutes. Thereafter, heat treatment (calcination) was performed at 650 ° C for 1 hour in a nitrogen atmosphere to obtain a passivation film containing an oxide of alumina and two or more kinds of vanadium group elements.

The voltage dependence of the electrostatic capacitance was measured using the passivation film obtained above, and the fixed charge density was calculated based on this.

Then, the passivation material (e2-1) to the passivation material (e2-4) were respectively applied to both surfaces of a 8 Å p-type ruthenium substrate, prebaked, and subjected to a nitrogen atmosphere at 650 ° C for 1 hour. Heat treatment (calcination), and a sample covered with a passivation film on both sides of the tantalum substrate was prepared. The carrier life of the sample was measured by a life measuring device (Kobelco Research Institute, RTA-540).

The results obtained are summarized in Table 8.

Depending on the ratio (mass ratio) of oxides of two or more kinds of vanadium elements after heat treatment (calcination), the results are different, but passivation using passivation material (e2-1) to passivation material (e2-4) The film showed a negative fixed charge after heat treatment (calcination), and the carrier lifetime also showed a certain value, so it was suggested to function as a passivation film.

[Reference Example 2-9]

In the same manner as in Reference Example 2-1, a commercially available organometallic thin film coating type material (High Purity Chemical Research Institute, SYM) which can obtain alumina (Al ₂ O ₃ ) by heat treatment (calcination) is used. -AL04, a concentration of 2.3% by mass], a commercially available organometallic thin film coating type material capable of obtaining vanadium oxide (V ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, V- 02, a concentration of 2% by mass], or a commercially available organometallic thin film coating type material which can obtain cerium oxide (Ta ₂ O ₅ ) by heat treatment (calcination) [High Purity Chemical Research Institute, Ltd., Ta- 10-P, a concentration of 10% by mass] was mixed, and a passivation material (f2-1) to a passivation material (f2-8) as a coating material was prepared (refer to Table 9).

Further, a passivation material (f2-9) using alumina alone was prepared (refer to Table 9).

In the same manner as in Reference Example 2-1, the passivation material (f2-1) to the passivation material (f2-9) were applied to one surface of the p-type germanium substrate, respectively, and then heat-treated (calcined) to prepare a passivation film. Using the passivation film to measure the voltage dependence of the electrostatic capacitance, Based on this, the fixed charge density is calculated.

Further, in the same manner as in Reference Example 2-1, the passivation material (f2-1) to the passivation material (f2-9) were respectively applied to both surfaces of the p-type germanium substrate, and heat treatment (calcination) was performed, and the obtained sample was used. To determine the carrier lifetime. The results obtained are summarized in Table 9.

As shown in Table 9, when the alumina/vanadium oxide or yttrium oxide in the passivation material is 90/10 and 80/20, the deviation of the value of the fixed charge density is large, and the negative fixed charge density cannot be stably obtained. However, it was confirmed that a negative fixed charge density can be achieved by using alumina and cerium oxide. It has been found that when a passivation material using alumina, vanadium oxide or yttrium oxide of 90/10 and 80/20 is measured by the CV method, it may become a passivation film which exhibits a positive fixed charge, and thus is not stably Showing a negative fixed charge. Further, a passivation film exhibiting a positive fixed charge can be used as a passivation film of an n-type germanium substrate. On the other hand, the passivation material (f2-9) in which the alumina reaches 100% by mass cannot obtain a negative fixed charge density.

[Reference Example 2-10]

A single crystal germanium substrate using boron as a dopant was used as the germanium substrate 101, and a solar cell element having the structure shown in Fig. 4 was produced. After the surface of the ruthenium substrate 101 is subjected to a texture treatment, only the coating-type phosphorus diffusion material is applied to the light-receiving surface side, and the diffusion layer 102 (phosphorus diffusion layer) is formed by heat treatment. Thereafter, the coated phosphorus diffusion material was removed using dilute hydrofluoric acid.

Then, on the light-receiving side, a SiN film is formed as a light-receiving surface anti-reflection film 103 by plasma CVD. Thereafter, the passivation material (a2-1) prepared in Reference Example 2-1 was applied to a region other than the contact region (opening portion OA) on the back side of the tantalum substrate 101 by an inkjet method. Thereafter, heat treatment is performed to form a passivation film 107 having an opening OA. Further, as the passivation film 107, a sample using the passivation material (c2-1) prepared in Reference Example 2-5 was separately prepared.

Then, the light-receiving surface formed on the light-receiving surface side of the ruthenium substrate 101 is anti-reflection On the film 103 (SiN film), a paste containing silver as a main component is screen-printed in the shape of a predetermined finger electrode and a bus bar electrode. On the back side, a paste with aluminum as a main component was screen printed onto the entire surface. Thereafter, heat treatment (burn-through) was performed at 850 ° C to form electrodes (first electrode 105 and second electrode 106), and aluminum was diffused into a portion of the opening OA of the back surface to form a BSF layer 104, and FIG. 4 was formed. The solar cell element of the structure shown.

Further, in the formation of the silver electrode on the light-receiving surface, a burn-through step in which the SiN film is not formed is described. However, the opening portion OA may be formed in advance in the SiN film by etching or the like, and then the silver electrode may be formed. .

For comparison, in the above-described fabrication step, the formation of the passivation film 107 is performed, and the aluminum paste is printed on the entire surface on the back surface side, and the p ⁺ layer 114 and the second electrode corresponding to the BSF layer 104 are formed on the entire surface. The corresponding electrode 116 forms the solar cell element of the structure of Fig. 1. The solar cell elements were evaluated for characteristics (short circuit current, open circuit voltage, curve factor, and conversion efficiency). The evaluation of the characteristics was carried out in accordance with JIS-C-8913 (2005) and JIS-C-8914 (2005). The results are shown in Table 10.

As shown in Table 10, the solar cell element having the passivation film 107 has an increase in short-circuit current and open-circuit voltage as compared with the solar cell element having no passivation film 107, and the conversion efficiency (photoelectric conversion efficiency) is increased by 0.6% at the maximum.

Japanese Patent Application No. 2012-160336, Japanese Patent Application No. 2012-218389, Japanese Patent Application No. 2013-011934, Japanese Patent Application No. 2013-040153, and Japanese Patent Application No. 2013-103573 All disclosures are incorporated herein by reference. All the documents, Japanese patent applications, and technical standards described in the present specification are incorporated herein by reference in the same manner as the following, which are specifically and separately described in the respective documents, Japanese Patent Applications, and The case where the standard is incorporated by reference.

101‧‧‧矽 substrate

102‧‧‧Diffusion layer

103‧‧‧Anti-reflective film

104‧‧‧BSF layer

105‧‧‧1st electrode

106‧‧‧2nd electrode

107‧‧‧passivation film

OA‧‧‧ openings

Claims (5)

A method for producing a semiconductor substrate with a passivation layer, comprising: a step of forming a composition layer by providing a composition for forming a passivation layer containing a compound represented by the following formula (I) on a semiconductor substrate; a step of forming a passivation layer by heat treatment at 300 ° C to 1000 ° C, M(OR ¹ ) _m (I) [wherein M comprises a group selected from the group consisting of Nb, Ta, V, Y, and Hf At least one metal element in the group, R ¹ independently represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 14 carbon atoms, and m is an integer of 1 to 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 formula (II). Wherein R ² each independently represents an alkyl group having 1 to 8 carbon atoms; n represents an integer of 0 to 3; and X ² and X ³ each independently represent an oxygen atom or a methylene group; and R ³ , R ⁴ and R; ⁵ independently represents 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 the first or second aspect of the invention, wherein the composition for forming a passivation layer contains a ruthenium compound in which M is Nb in the above formula (I). The method for producing a semiconductor substrate with a passivation layer according to any one of claims 1 to 3, wherein the heat treatment temperature is 600 ° C to 800 ° C. A semiconductor substrate with a passivation layer obtained by a method for producing a semiconductor substrate with a passivation layer as described in any one of claims 1 to 4.