CN105814665A - Method for manufacturing semiconductor substrate, semiconductor substrate, method for manufacturing solar cell element, and solar cell element - Google Patents

Abstract

Provided is a production method for a semiconductor substrate in which an n-type diffusion layer and a p-type diffusion layer are formed at different locations on a single semiconductor substrate by a first diffusion step and a second diffusion step. When the first diffusion step comprises a step in which a composition that is for forming a p-type diffusion layer and that contains a dispersion medium and glass particles comprising an acceptor element is applied to a semiconductor substrate and a step in which the acceptor element is diffused onto the semiconductor substrate by heat treatment in order to form a p-type diffusion layer, the second diffusion step comprises a step in which the heat-treated product of the composition for forming a p-type diffusion layer is used as a mask and phosphorus is diffused. The composition for forming a p-type diffusion layer of the first diffusion step may be substituted with a composition for forming an n-type diffusion layer that contains a dispersion medium and glass particles comprising a toner element. On this occasion, the heat-treated product of the composition for forming an n-type diffusion layer is used as a mask and boron is diffused at the second diffusion step.

Description

Method for manufacturing semiconductor substrate, semiconductor substrate, method for manufacturing solar cell element, and solar cell element

technical field

The present invention relates to a method for manufacturing a semiconductor substrate, a semiconductor substrate, a method for manufacturing a solar cell element, and a solar cell element.

Background technique

In a conventional solar cell element, a pn junction is formed by diffusing impurities of a conductivity type opposite to that of the silicon substrate to the light-receiving surface of the silicon substrate on the side where sunlight is incident. Furthermore, electrodes are respectively formed on the light-receiving surface and the back surface opposite to the light-receiving surface of the silicon substrate.

In the solar cell element described above, since the electrodes are formed on the light-receiving surface, there is a problem that the electrodes prevent the incidence of sunlight and lower the power generation efficiency. Therefore, a back contact type (back electrode type) solar cell in which an electrode is not formed on the light-receiving surface of a silicon substrate but only on the back surface has been proposed. There is, for example, US Pat. No. 4,927,770 as a prior document related to a method of manufacturing such a back contact solar cell. In U.S. Patent No. 4,927,770, after forming a dielectric layer of SiO ₂ , SiNx, etc. on the back surface of a silicon substrate, a portion is opened, and a dopant source compound is applied to the opening to make the dopant diffused into the silicon substrate.

In addition, U.S. Patent No. 7,883,343 discloses a method in which a p-type diffusion layer (hereinafter also referred to as a p ⁺ layer) is formed on the light-receiving surface and the entire back surface of an n _- type silicon substrate using BBr gas, and then Resist is pattern-coated on the back surface, and the portion other than the resist-coated portion and the light-receiving surface on the back surface are etched, and an n-type diffused layer (hereinafter also referred to as “n-type diffused layer”) is formed on the etched portion and light-receiving surface of the back surface. for n ⁺ layers).

In addition to the above-mentioned single-side light-receiving type solar cells, double-side light-receiving type solar cells capable of receiving light from both sides are also known. For such solar cells, not only solar cells of the type that can be installed on walls and receive light from both sides have been proposed, but also those that have reflective functions on the back sheet for installation on structures such as roofs, so that the elements in the module can A solar cell of the type in which the light transmitted to the back side of the solar cell is reflected by the gap between the solar cells and the light is also taken from the back side (for example, refer to Japanese Patent Application Laid-Open No. 2012-195489). This improves the power generation efficiency of the solar cell.

Regarding the formation method of the diffusion layer of the silicon substrate used in double-sided light-receiving solar cells, first, using BBr ₃ gas or the like, p ⁺ layers are collectively formed on both sides of the silicon substrate with the textured structure, and then the single The surface is etched to remove the resulting borosilicate glass layer and p ⁺ layer. Next, after forming a mask layer on the surface where the p ⁺ layer remained, an n ⁺ layer was formed on the surface where the borosilicate glass layer and the p ⁺ layer were removed by etching using POCl ₃ gas or the like. It is a common method to form the p ⁺ layer and the n ⁺ layer by separate steps in this way (for example, refer to Jpn. J. Appl. Phys., Vol. 42 (2003), pp. 5397-5404). In addition, there is also disclosed a method of leaving the borosilicate glass layer without removing it and utilizing it as a mask layer (for example, refer to Japanese Patent No. 3170445).

In addition, a method of forming a p-type diffusion layer using a p-type impurity diffusing agent containing boron oxide, boric acid, an organoboron compound, a boron-aluminum compound, an organoaluminum compound, or an aluminum salt, and using its residue to burn A part of the product is used as a mask layer to form an n-type diffusion layer (for example, refer to Japanese Patent Application Laid-Open No. 2011-35252).

Contents of the invention

The problem to be solved by the invention

In a conventional manufacturing process of a solar cell element, the n ⁺ layer and the p ⁺ layer of the semiconductor substrate are formed in separate steps. This is because it is difficult to collectively form the n ⁺ layer and the p ⁺ layer for the following reasons. In the diffusion using gas such as POCl ₃ , BBr ₃ , it is difficult to perform site-selective doping (diffusion), and even when a coating-type conventional dopant material is used instead of the gas, the dopant It is also easy to volatilize at the temperature of diffusion (800°C to 1000°C), and it is difficult to perform site-selective doping.

In addition, in order to form the n ⁺ layer after forming the p ⁺ layer, it is necessary to cover the p ⁺ layer with a barrier layer or the like, which inevitably increases the number of steps. As mentioned in the descriptions of US Pat. No. 4,927,770 and US Pat. No. 7,883,343, when the p ⁺ layer and the n ⁺ layer are patterned on the back surface, many steps are usually required.

In addition, as described in Japanese Patent No. 3170445, in the method of using a borosilicate layer formed by _BBr3 gas as a mask layer, since the borosilicate layer is formed on the entire surface of the silicon substrate Therefore, there is a problem that the number of steps increases after forming a borosilicate layer on the entire surface of a silicon substrate in order to locally form a p ⁺ layer and an n ⁺ layer, and then patterning using a resist.

In addition, as described in Japanese Patent Laid-Open No. 2011-35252, in the method of using a p-type impurity diffusing agent and using its baked product as a mask layer, the boron compound has high volatility, and boron diffuses to impart In addition, there is a problem that pinholes and cracks are easily generated in the fired product of the p-type impurity diffusing agent, and the shielding performance against the diffusion of phosphorus and the like is not sufficient.

In view of the above situation, the technical problem of the present invention is to manufacture a semiconductor substrate having an n-type diffusion layer and a p-type diffusion layer in different parts of one semiconductor substrate by a simple method without complicated steps.

means of solving problems

The present invention includes the following schemes.

<1> A method of manufacturing a semiconductor substrate having a diffusion layer, comprising:

A step of applying a p-type diffusion layer-forming composition containing glass particles containing an acceptor element and a dispersion medium to at least a part of the semiconductor substrate;

A step of forming a p-type diffusion layer by diffusing the acceptor element into the semiconductor substrate by heat treatment; and

A step of forming an n-type diffusion layer by diffusing phosphorus into the semiconductor substrate by using at least a part of the heat-treated product of the p-type diffusion layer-forming composition as a mask.

<2> The method for manufacturing a semiconductor substrate according to the above <1>, wherein the acceptor element contains at least one element selected from the group consisting of B (boron), Al (aluminum), and Ga (gallium).

<3> The method for producing a semiconductor substrate according to the above <1> or <2>, wherein the glass particles containing an acceptor element contain an element selected from B ₂ O ₃ , Al ₂ O ₃ and Ga ₂ O ₃ . At least one acceptor element-containing substance selected from SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, Tl ₂ O, V ₂ O ₅ , SnO, ZrO ₂ , WO ₃ , MoO ₃ , and at least one glass component substance selected from MnO.

<4> A method of manufacturing a semiconductor substrate having a diffusion layer, comprising:

A step of applying an n-type diffusion layer-forming composition to at least a part of the semiconductor substrate, the n-type diffusion layer-forming composition containing glass particles containing a donor element and a dispersion medium;

A step of forming an n-type diffusion layer by diffusing the above-mentioned donor element into the above-mentioned semiconductor substrate by heat treatment; and

A step of forming a p-type diffusion layer by diffusing boron into the semiconductor substrate by using at least a part of the heat-treated product of the n-type diffusion layer-forming composition as a mask.

<5> The method for manufacturing a semiconductor substrate according to the above <4>, wherein the donor element is at least one selected from P (phosphorus) and Sb (antimony).

< ₆ > _The method for producing a semiconductor substrate according to < ₄ > or < ₅ > above, wherein the glass particles containing a _donor element _contain at least 1 kind of material containing donor element and selected from SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ and At least one glass component substance in MoO ₃ .

<7> The method for manufacturing a semiconductor substrate according to any one of <1> to <6> above, further including a step of forming a passivation layer on the p-type diffusion layer and the n-type diffusion layer.

<8> The method for manufacturing a semiconductor substrate according to the above <7>, wherein the passivation layer contains at least one selected from silicon oxide, silicon nitride, and aluminum oxide.

<9> A semiconductor substrate having a p-type diffusion layer and an n-type diffusion layer obtained by the production method according to any one of the above <1> to <8>.

<10> A method for producing a solar cell element, comprising the step of forming an electrode on the p-type diffusion layer of the semiconductor substrate obtained by the production method according to any one of <1> to <3> above.

<11> A method for producing a solar cell element, comprising the step of forming an electrode on the n-type diffusion layer of the semiconductor substrate obtained by the production method according to any one of <4> to <6> above.

<12> A solar cell element obtained by the production method described in <10> or <11> above.

Invention effect

According to the present invention, a semiconductor substrate having an n-type diffused layer and a p-type diffused layer in different parts of one semiconductor substrate can be manufactured by a simple method without complicated steps.

Description of drawings

FIG. 1 is a cross-sectional view schematically showing an example of a method for manufacturing a back contact solar cell element according to this embodiment.

FIG. 2 is a cross-sectional view schematically showing an example of a method for manufacturing a double-side light-receiving type solar cell element according to this embodiment.

detailed description

In this specification, the term "process" is not just an independent process, and even if it cannot be clearly distinguished from other processes, as long as the intended purpose of the process can be achieved, it is included in this term. In addition, the numerical range represented by "-" used in this specification shows the range which includes the numerical value described before and behind "-" as a minimum value and a maximum value, respectively. In addition, when the amount of each component in the composition of this specification exists in a composition, when there exists a plurality of substances corresponding to each component, unless otherwise specified, it refers to the amount of the plurality of substances present in the composition. total amount.

In addition, in this specification, unless otherwise stated, "content rate" means the mass % of each component when the total amount of the composition for forming an impurity diffusion layer is 100 mass %. In addition, in this specification, the term "layer" includes not only a shape formed on the entire surface when viewed from a plan view, but also a configuration formed in a part of a shape viewed from a plan view.

<Manufacturing method of semiconductor substrate with diffusion layer>

The method for manufacturing a semiconductor substrate having a diffusion layer according to the present invention includes the step of applying a p-type diffusion layer-forming composition containing glass particles containing an acceptor element and a p-type diffusion layer-forming composition to at least a part of the semiconductor substrate a dispersion medium; a step of diffusing the acceptor element into the semiconductor substrate by heat treatment to form a p-type diffusion layer (first diffusion step); and using at least a part of the heat-treated product of the p-type diffusion layer forming composition as a mask , a step of diffusing phosphorus into the semiconductor substrate to form an n-type diffusion layer (second diffusion step). The diffusion of phosphorus in the second diffusion step may be a gas diffusion method using POCl ₃ or the like, or a method of partially or entirely applying a liquid containing phosphoric acid or the like.

In addition, the method for manufacturing a semiconductor substrate having a diffusion layer according to the present invention includes the step of applying an n-type diffusion layer-forming composition containing glass particles containing a donor element to at least a part of the semiconductor substrate. and a dispersion medium; a step of diffusing the above-mentioned donor element into the above-mentioned semiconductor substrate by heat treatment to form an n-type diffusion layer (first diffusion step); and using at least a part of the heat-treated product of the above-mentioned n-type diffusion layer forming composition as a mask , a step of diffusing boron into the semiconductor substrate to form a p-type diffusion layer (second diffusion step). Diffusion of boron in the second diffusion step may be a gas diffusion method using BBr ₃ , BCl ₃ , or the like, or a method of partially or entirely applying a liquid containing boric acid or the like.

Thus, in the present invention, an n-type diffusion layer and a p-type diffusion layer are formed in different parts of one semiconductor substrate through the first diffusion step and the second diffusion step. In the case where the first diffusion step has a step of imparting a composition for forming a p-type diffusion layer and a step of diffusing an acceptor element into a semiconductor substrate to form a p-type diffusion layer, the second diffusion step has a step of forming a p-type diffusion layer. A process in which the heat-treated product of the composition is used as a mask to diffuse phosphorus. The p-type diffusion layer-forming composition in the first diffusion step can be replaced by an n-type diffusion layer-forming composition. At this time, in the second diffusion step, the heat-treated product of the n-type diffusion layer-forming composition is used as a mask and Diffuse boron.

In the first diffusion step, by using glass particles containing a donor element or glass particles containing an acceptor element as a dopant material, the donor element or the acceptor element becomes less volatile and can be site-selectively formed on the semiconductor substrate. Any of p ⁺ layers or n ⁺ layers. In addition, the glass particles containing a donor element or the glass particles containing an acceptor element are softened or melted when the donor element or the acceptor element is diffused into the semiconductor substrate, so the heat-treated product forms a dense layer with few cracks. Therefore, the layer of the heat-treated material has high shielding performance and can be used as a mask layer as it is. Thus, in the present invention, the etching step and the mask layer forming step required in the conventional manufacturing method can be simplified, and the n ⁺ layer or p ⁺ layer can be easily formed in the second diffusion step.

Hereinafter, first, the n-type diffusion layer-forming composition, the p-type diffusion layer-forming composition, and the semiconductor substrate used in the production method of the present invention will be described, and then a method of forming a diffusion layer on the semiconductor substrate using them will be described.

(n-type diffusion layer forming composition)

The n-type diffused layer forming composition of the present invention contains at least one kind of glass particles containing a donor element and at least one kind of dispersion medium, and may further contain other additives if necessary in consideration of applicability and the like.

Here, the n-type diffused layer forming composition refers to a material that contains a donor element and can form an n-type diffused layer on a semiconductor substrate by thermally diffusing the donor element after being applied to the semiconductor substrate. By using an n-type diffusion layer-forming composition containing a donor element in glass particles, it is possible to form an n-type diffusion layer at a desired location and suppress formation of an n-type diffusion layer at an unnecessary region.

Therefore, when the composition for forming an n-type diffused layer of the present invention is applied, unlike the gas phase reaction method widely used in the past, the patterning of the region to be provided can be performed, and the process can be simplified. It should be noted that if it is desired to use a highly volatile phosphorus compound such as phosphoric acid, phosphorus pentoxide, or phosphoric acid ester to form an n-type diffusion layer and a p-type diffusion layer at the same time, phosphorus will diffuse into the region to which the phosphorus compound is applied. outside. This is due to: Generally, compared with phosphorus, the diffusion rate of acceptor elements such as boron into the semiconductor substrate is slower, so if you want to fully diffuse the acceptor element, you must diffuse it at a higher temperature than phosphorus (for example, 900 ℃～950℃), and the donor elements such as phosphorus become easy to volatilize.

It should be noted that the glass particles contained in the n-type diffused layer-forming composition of the present invention are melted by heat treatment (firing) to form a glass layer on the n-type diffused layer. However, in the conventional gas phase reaction method and the method of applying a phosphate-containing solution or paste, a glass layer is formed on the n-type diffusion layer, so the glass layer produced in the present invention can be used in the same manner as the conventional method. etch to remove. Therefore, the composition for forming an n-type diffused layer according to the present invention does not generate unnecessary products and does not increase the number of steps compared with conventional methods.

In addition, the donor component in the glass particles is less likely to volatilize even during heat treatment (firing) for diffusion, so it is possible to suppress the formation of the n-type diffusion layer beyond the desired region due to the generation of volatile gas. The reason for this is considered to be that the donor component is less likely to volatilize because it is bound to an element in the glass particle or incorporated into the glass.

In addition, in the n-type diffused layer forming composition of the present invention, by adjusting the concentration of the donor element, an n-type diffused layer with a desired concentration can be formed at a desired position, so it is possible to form a composition with a high n-type dopant concentration. selective area. On the other hand, it is generally difficult to form a selective region with a high n-type dopant concentration by a gas phase reaction method or a method using a phosphate-containing solution, which are common methods for n-type diffusion layers.

Hereinafter, the glass particles containing a donor element of the present invention will be described in detail.

The donor element refers to an element capable of forming an n-type diffusion layer by being doped into a semiconductor substrate. As the donor element, an element of Group 15 can be used, and examples thereof include P (phosphorus), Sb (antimony), Bi (bismuth), and As (arsenic). From the viewpoint of safety, easiness of vitrification, etc., at least one selected from P and Sb is preferable.

Glass particles containing a donor element can be formed, for example, by containing a donor element-containing substance and a glass component substance. Examples _of the donor element _- containing substance used to introduce the donor element into glass _{particles include P2O3 , P2O5} , _Sb2O3 , _Bi2O3 , and _{As2O3 .} At least one of O ₃ , P ₂ O ₅ and Sb ₂ O ₃ .

Examples of glass components include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ , WO ₃ , MoO ₃ , MnO, La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , ZrO ₂ , GeO ₂ , TeO ₂ , Lu ₂ O ₃ , etc., preferably selected from SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ and MoO ₃ at least one, more preferably used At least one selected from SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, V ₂ O ₅ , SnO, ZrO ₂ and MoO ₃ .

Glass particles containing a donor element can control melting temperature, softening point, glass transition temperature, chemical durability, etc. by adjusting the component ratio as necessary.

Specific examples of glass particles containing a donor element include a system containing _both the above _- mentioned donor element _- containing substance and the above-mentioned glass component substance. , and the same below), glass particles containing P ₂ O ₅ -K ₂ O, glass particles containing P ₂ O ₅ -Na ₂ O, glass particles containing P ₂ O ₅ -Li ₂ O , glass particles containing P ₂ O ₅ -BaO, glass particles containing P ₂ O ₅ -SrO, glass particles containing P ₂ O ₅ -CaO, glass particles containing P ₂ O ₅ -MgO, glass particles containing P ₂ O ₅ -BeO glass particles, P ₂ O ₅ -ZnO containing glass particles, P ₂ O ₅ -CdO containing glass particles, P ₂ O ₅ -PbO containing glass particles, P ₂ O ₅ -V ₂ O ₅ containing glass particles Glass particles containing _{P2O5 - SnO} , glass particles containing _{P2O5 - GeO2} , glass particles containing _{P2O5 -} TeO2, etc. Glass containing _P2O5 as a donor element _- containing substance Particles; glass particles containing Sb ₂ O ₃ instead of P _{2 O 5 in the above-mentioned glass particles containing P 2 O 5 as the} donor element-containing substance.

It should be noted that, like glass particles containing P ₂ O ₅ -Sb ₂ O ₃ , glass particles containing P ₂ O ₅ -As ₂ O ₃ , etc., it may be a glass containing two or more kinds of donor element-containing substances. particle.

The composite glass particles containing two components were exemplified above, but glass particles containing three or more components such as P ₂ O ₅ -SiO ₂ -V ₂ O ₅ and P ₂ O ₅ -SiO ₂ -CaO may be used.

Regarding the content ratio of the glass component substance in the glass particles, it is desirable to appropriately set the melting temperature, softening point, glass transition temperature and chemical durability in consideration, and usually, it is preferably 0.1% by mass to 95% by mass, and more preferably It is 0.5 mass % - 90 mass %.

In addition, at least one selected from SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, SnO, ZrO ₂ and MoO ₃ is used as In the case of glass particles of a glass component material, since the reaction product with the silicon substrate generated during the heat treatment for diffusion does not remain as a residue during the hydrofluoric acid treatment, it is preferable. In addition, in the case of glass particles containing vanadium oxide V ₂ O ₅ as a glass component (for example, glass particles containing P ₂ O ₅ -V ₂ O ₅ ), V ₂ The content ratio of O ₅ is preferably 1% by mass to 50% by mass, more preferably 3% by mass to 40% by mass.

The softening point of the glass particles is preferably from 200°C to 1000°C, more preferably from 300°C to 980°C, from the viewpoint of diffusivity during heat treatment for diffusion, liquid sagging, etc. From the viewpoint of high wettability of the semiconductor substrate to uniformly diffuse the donor element into the semiconductor substrate, it is more preferably 400°C to 970°C, and from the viewpoint of low volatility of the glass at the diffusion temperature, it is particularly preferably 800°C ~960°C.

By using glass particles with a softening point in the above range, it is possible to uniformly follow the semiconductor substrate during heat treatment for diffusion, and the shielding performance when using the heat-treated product of the n-type diffusion layer composition as a mask layer becomes sufficient.

It should be noted that, in contrast to conventional coating-type dopant materials, which have pinholes and the like in the heat-treated product after heat treatment, the n-type diffused layer-forming composition of the present invention softens once during heat treatment and covers the semiconductor. Therefore, the occurrence of pinholes and the like in the heat-treated object is suppressed, and the shielding performance of the heat-treated object becomes high.

The softening point of glass can be measured by differential thermal analysis (DTA) method. Specifically, a differential thermal analysis (DTA) device can be used, and α-alumina can be used as a reference to measure under the condition of a heating rate of about 10K/min, and the second endotherm of the differential curve of the obtained DTA curve The peak was set as the softening point. The measurement atmosphere is not particularly limited, but it is preferable to measure glass particles in an atmosphere with stable chemical properties.

The shape of the glass particles containing the donor element can be roughly spherical, flat, massive, plate-like, scaly, etc. From the coating property on the semiconductor substrate and the uniform diffusion of the n-type diffusion layer forming composition In terms of properties, it is preferably approximately spherical, flat or plate-shaped.

The particle size of the glass particles containing the donor element is preferably 100 μm or less. When glass particles having a particle diameter of 100 μm or less are used, a smooth coating film is easily obtained. Furthermore, the particle size of the glass particles is more preferably 50 μm or less, further preferably 30 μm or less, particularly preferably 10 μm or less, and most preferably 1 μm or less. In addition, although the lower limit is not specifically limited, It is preferable that it is 0.01 micrometer or more.

Here, the particle diameter of the glass particles containing the donor element means the particle diameter D50% corresponding to 50% volume accumulation from the diameter side in the particle size distribution, and can be measured by a laser scattering diffraction particle size distribution measuring device or the like.

Glass particles containing donor elements were fabricated using the following steps.

First, raw materials, for example, the aforementioned donor element-containing substance and glass component substance are weighed and filled into a crucible. Examples of the material of the crucible include platinum, platinum-rhodium, iridium, alumina, quartz, carbon, and the like, and can be appropriately selected in consideration of melting temperature, atmosphere, reactivity with molten substances, and the like.

Next, heating is performed at a temperature corresponding to the composition of the glass in an electric furnace to form a molten liquid. At this time, stirring is preferably performed so that the melt becomes uniform. Next, the obtained melt is flowed onto a zirconia substrate, a carbon substrate, or the like to vitrify the melt. Then, the glass is pulverized into a powder form. For pulverization, known devices such as jet mills, bead mills, and ball mills can be used.

The content ratio of the glass particles containing a donor element in the n-type diffused layer forming composition is determined in consideration of applicability, diffusivity of the donor element, and the like. Usually, the content ratio of the glass particles in the n-type diffusion layer forming composition is preferably 0.1% by mass to 95% by mass, more preferably 1% by mass to 90% by mass, still more preferably 1.5% by mass to 85% by mass, particularly preferably It is 2 mass % - 80 mass %.

The content ratio of the inorganic compound component in the total solid content of the n-type diffusion layer forming composition is preferably 40% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, particularly preferably 80% by mass or more.

The content of glass particles containing a donor element in the inorganic compound component is preferably 50% by mass or more, more preferably 75% by mass or more, still more preferably 85% by mass or more, particularly preferably 90% by mass or more.

Next, the dispersion medium will be described.

The dispersion medium is a medium for dispersing the aforementioned glass particles in the composition. Specifically, as a dispersion medium, a binder and a solvent are used.

As the binder, polyvinyl alcohol; polyacrylamide resin; polyvinylamide resin; polyvinylpyrrolidone resin; polyethylene oxide resin; polysulfone resin; acrylamide alkylsulfone resin; cellulose ether, Carboxymethyl cellulose, hydroxyethyl cellulose, ethyl cellulose and other cellulose derivatives; gelatin, gelatin derivatives; starch, starch derivatives; sodium alginate compounds; xanthan gum; guar gum, guar gum Derivatives; scleroglucan, scleroglucan derivatives; tragacanth, tragacanth derivatives; dextrin, dextrin derivatives; (meth)acrylic resins; (meth)alkyl acrylate resins, (meth)acrylate resins such as dimethylaminoethyl (meth)acrylate resins; butadiene resins; styrene resins; butyral resins; copolymers thereof; These can be used alone or in combination of two or more.

Here, (meth)acrylic acid means acrylic acid or methacrylic acid, and (meth)acrylate means acrylate or methacrylate.

Among them, from the standpoint of decomposability and prevention of liquid sagging during screen printing, the binder preferably contains an acrylic resin, a butyral resin, or a cellulose derivative, and preferably contains at least a cellulose derivative. Examples of cellulose derivatives include ethyl cellulose, nitrocellulose, acetyl cellulose, carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, and hydroxyethyl cellulose, among which ethyl cellulose is preferably used. base cellulose. A binder can be used individually by 1 type or in combination of 2 or more types.

The molecular weight of the binder is not particularly limited, and it is desirable to appropriately adjust it in consideration of the desired viscosity of the composition. When the composition for forming a p-type diffusion layer contains a binder, the content of the binder in the composition for forming a p-type diffusion layer is preferably 0.5% by mass to 30% by mass, more preferably 3% by mass to 25% by mass , More preferably, it is 3 mass % - 20 mass %.

Examples of solvents include: acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl isopropyl ketone, methyl n-butyl ketone, methyl isobutyl ketone, methyl n-amyl ketone, methyl n-hexyl Ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, trimethylnonanone, cyclohexanone, cyclopentanone, methylcyclohexanone, 2,4-pentanedione, acetonylacetone, etc. Ketone solvents; diethyl ether, methyl ethyl ether, methyl n-propyl ether, diisopropyl ether, tetrahydrofuran, methyl tetrahydrofuran, dioxane, dimethyldioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol dibutyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol di Ethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl n-propyl ether, diethylene glycol methyl n-butyl ether, diethylene glycol di-n-propyl ether, diethylene glycol Di-n-butyl ether, diethylene glycol methyl n-hexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl n-butyl ether, triethylene glycol di-n-butyl ether, triethylene glycol methyl n-hexyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether Base 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, Dipropylene glycol di-n-propyl ether, dipropylene glycol di-n-butyl ether, dipropylene glycol methyl n-hexyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol methyl ethyl ether, tripropylene glycol methyl n-butyl ether, tripropylene glycol di-n-butyl ether, tripropylene glycol methyl n-hexyl ether, tetrapropylene glycol dimethyl ether, tetrapropylene glycol diethyl ether, tetrapropylene glycol methyl ethyl ether, tetrapropylene glycol methyl n-butyl Ether, tetrapropylene glycol di-n-butyl ether, tetrapropylene glycol methyl n-hexyl ether, tetrapropylene glycol di-n-butyl ether and other ether solvents; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate ester, isobutyl acetate, sec-butyl acetate, n-pentyl acetate, sec-pentyl acetate, 3-methoxybutyl acetate, methylpentyl acetate, 2-ethylbutyl acetate, 2-ethyl acetate Hexyl acetate, 2-(2-butoxyethoxy)ethyl acetate, benzyl acetate, cyclohexyl acetate, methylcyclohexyl acetate, nonyl acetate, methyl acetoacetate, ethyl acetoacetate, acetic acid Diethylene glycol methyl ether, diethylene glycol monoethyl ether acetate, dipropylene glycol methyl ether acetate, dipropylene glycol ethyl ether acetate, ethylene glycol diacetate, methoxytriethylene diacetate Alcohol ester, ethyl propionate, n-butyl propionate, isopentyl propionate, diethyl oxalate, di-n-butyl oxalate, methyl lactate, ethyl lactate, n-butyl lactate, n-pentyl lactate, ethyl Glycol methyl ether propionate, ethylene glycol ethyl ether propionate, ethylene glycol methyl ether acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, propylene glycol ethyl Ether acetate, propylene glycol propyl ether acetate, γ-butyrolactone, γ-valerolactone and other ester solvents; acetonitrile, N- Methylpyrrolidone, N-ethylpyrrolidone, N-propylpyrrolidone, N-butylpyrrolidone, N-hexylpyrrolidone, N-cyclohexylpyrrolidone, N,N-dimethylformamide, N,N-dimethyl Aprotic polar solvents such as acetamide and dimethyl sulfoxide; methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-pentanol, isopentyl alcohol Alcohol, 2-methylbutanol, sec-pentanol, tert-amyl alcohol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, sec-hexanol, 2-ethylbutanol, sec-heptanol, n-octanol, 2-ethylhexanol, sec-octyl alcohol, n-nonanol, n-decyl alcohol, sec-undecanol, trimethylnonanol, sec-tetradecanol, sec-heptadecanol, phenol, cyclo Hexanol, Methylcyclohexanol, Benzyl Alcohol, Isobornylcyclohexanol, Ethylene Glycol, 1,2-Propanediol, 1,3-Butanediol, Diethylene Glycol, Dipropylene Glycol, Triethylene Glycol, Alcohol solvents such as tripropylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether (cellosolve), ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether Diethylene glycol mono-n-butyl ether, diethylene glycol mono-n-hexyl ether, triethylene glycol ethyl ether, tetraethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether , dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether and other glycol monoether solvents; terpinene, terpineol, myrcene, alloocimene, limonene, dipentene, pinene, carvone, Terpene solvents such as ocimene and phellandrene; isobornylcyclohexanol, isobornylphenol, 1-isopropyl-4-methyl-bicyclo[2.2.2]oct-5-ene-2,3- dicarboxylic anhydride, p-menthenylphenol; and water. These solvents may be used alone or in combination of two or more.

Among them, from the viewpoint of applicability to semiconductor substrates, water, alcohol solvents, glycol monoether solvents, or terpene solvents are preferred as the dispersion medium, and water, alcohol, cellosolve, terpineol, diethylene glycol, and diethylene glycol are more preferred. Alcohol mono-n-butyl ether or diethylene glycol mono-n-butyl acetate, more preferably water, alcohol, terpineol or cellosolve.

The content ratio of the dispersion medium in the n-type diffusion layer forming composition is determined in consideration of applicability, donor element concentration, and the like. In consideration of applicability, the viscosity of the n-type diffused layer-forming composition is preferably 10 mPa·s to 1,000,000 mPa·s, more preferably 50 mPa·s to 500,000 mPa·s.

Furthermore, the composition for forming an n-type diffusion layer may contain other additives. As another additive, the metal which reacts easily with the said glass particle is mentioned, for example.

The n-type diffused layer-forming composition is applied to a semiconductor substrate and heat-treated at a high temperature to form an n-type diffused layer. At this time, glass is formed on the surface. The glass is removed by dipping in an acid such as hydrofluoric acid, but it may be difficult to remove depending on the type of glass. At this time, glass can be easily removed after acid cleaning by adding metals such as Ag, Mn, Cu, Fe, Zn, and Si. Among them, at least one selected from Ag, Si, Cu, Fe, Zn and Mn is preferably used, at least one selected from Ag, Si and Zn is more preferably used, and Ag is particularly preferred.

The content ratio of the metal is desirably adjusted appropriately according to the type of glass and the type of the metal, but usually, it is preferably 0.01% by mass to 10% by mass relative to the glass particles.

(p-type diffusion layer forming composition)

The composition for forming a p-type diffusion layer of the present invention contains at least one kind of glass particles containing an acceptor element and at least one kind of dispersion medium, and may further contain other additives as necessary in consideration of coatability and the like.

Here, the composition for forming a p-type diffusion layer refers to a material that contains an acceptor element and can form a p-type diffusion layer on a semiconductor substrate by thermally diffusing the acceptor element after being applied to the semiconductor substrate. By using a p-type diffusion layer-forming composition containing an acceptor element in glass particles, it is possible to form a p-type diffusion layer at a desired location and suppress formation of a p-type diffusion layer at an unnecessary region.

In addition, the acceptor element in the glass particles does not volatilize easily even in the heat treatment (firing) for diffusion, so it is possible to suppress the formation of the p-type diffusion layer beyond the desired region due to the generation of volatile gas. The reason for this is considered to be that the acceptor element is not easily volatilized because it combines with an element in the glass particles or enters the glass.

In addition, in the composition for forming a p-type diffusion layer of the present invention, by adjusting the concentration of the acceptor element, a p-type diffusion layer with a desired concentration can be formed at a desired position, so that the concentration of the p-type dopant can be adjusted. High selectivity area.

Hereinafter, the glass particle containing the acceptor element of this invention is demonstrated in detail.

The acceptor element refers to an element capable of forming a p-type diffusion layer by being doped into a semiconductor substrate. As the acceptor element, an element of Group 13 can be used, such as B (boron), Al (aluminum), Ga (gallium), etc., preferably containing elements selected from B (boron), Al (aluminum), and Ga (gallium). At least one element in is preferably B or Ga from the viewpoint of easiness of vitrification and the like.

Glass particles containing an acceptor element can be formed, for example, by containing an acceptor element-containing substance and a glass component substance. Examples _of the acceptor element _- containing substance used to introduce the acceptor element into glass particles include B ₂ O ₃ , Al ₂ O ₃ and _{Ga 2} O _{3 .} At least one of ₂ O ₃ .

Examples of glass components include SiO ₂ , K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, Tl ₂ O, V ₂ O ₅ , SnO, ZrO _2. WO ₃ , MoO ₃ , MnO, La ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , Y ₂ O ₃ , TiO ₂ , GeO ₂ , TeO ₂ and Lu ₂ O ₃ etc., preferably selected from SiO _2. K ₂ O, Na ₂ O, Li ₂ O, BaO, SrO, CaO, MgO, BeO, ZnO, PbO, CdO, Tl ₂ O, V ₂ O ₅ , SnO, ZrO ₂ , WO ₃ , MoO ₃ and at least one of MnO.

In addition, glass particles containing an acceptor element can control melting temperature, softening point, glass transition temperature, chemical durability, and the like by adjusting the component ratio as necessary.

Specific examples of glass particles containing an acceptor element include glass particles containing both an acceptor element-containing substance and a glass component substance, such as: B ₂ O ₃ -SiO ₂ (referred to as an acceptor element-containing substance-glass The order of the component substances is described in the following, the same as below), glass particles containing B ₂ O ₃ -ZnO, glass particles containing B ₂ O ₃ -PbO, glass particles containing Al ₂ O ₃ -SiO ₂ , glass particles containing B ₂ O ₃ -Al ₂ O ₃ glass particles, Ga ₂ O ₃ -SiO ₂ containing glass particles, Ga ₂ O ₃ -B ₂ O ₃ containing glass particles, glass particles containing B ₂ O ₃ alone, etc. .

The single-component glass and the composite glass containing two components were exemplified above, but composite glasses of three or more kinds as necessary, such as B ₂ O ₃ -SiO ₂ -Na ₂ O, may be used. In addition, glass particles containing two or more kinds of acceptor element-containing substances such as B ₂ O ₃ -Al ₂ O ₃ system may be used.

The content ratio of the glass component substance in the glass particles is preferably set appropriately in consideration of the melting temperature, softening point, glass transition temperature and chemical durability, and is usually preferably 0.1% by mass to 95% by mass, more preferably It is 0.5 mass % - 90 mass %.

Specifically, in the case of glass particles containing B ₂ O ₃ -SiO ₂ -CaO, the content of CaO is preferably 1% by mass to 30% by mass, more preferably 5% by mass to 20% by mass.

The softening point of glass particles containing an acceptor element is preferably from 200°C to 1000°C, more preferably from 300°C to 900°C, from the viewpoint of diffusivity during heat treatment for diffusion, liquid sagging, and the like. From the viewpoint of uniformly diffusing the acceptor element into the semiconductor substrate by utilizing the high wettability of the glass particles to the semiconductor substrate, and from the viewpoint of the diffusion rate of the acceptor element, it is more preferably 400°C to 880°C. From the perspective of the diffusion temperature From the viewpoint of low volatility of the glass below, it is particularly preferably 700°C to 860°C.

By using glass particles having a softening point in the above range, it is possible to uniformly follow the semiconductor substrate during heat treatment for diffusion, and the shielding performance when using the heat-treated product of the p-type diffusion layer composition as a mask layer becomes sufficient. That is, in contrast to conventional coating-type dopant materials, which have pinholes and the like in the heat-treated product after heat treatment, the composition for forming a p-type diffusion layer of the present invention softens once during heat treatment and covers the semiconductor substrate. The generation of pinholes etc. in the heat-treated material is suppressed, and the shielding performance of the heat-treated material is improved. The softening point of glass particles containing an acceptor element is measured in the same manner as the softening point of glass particles containing a donor element.

The shape of the glass particles containing the acceptor element can be roughly spherical, flat, massive, plate-like, scaly, etc. From the coating properties and uniformity of the n-type diffusion layer forming composition to the semiconductor substrate From the viewpoint of diffusivity, it is preferably approximately spherical, flat or plate-shaped.

The average particle diameter of the glass particles containing an acceptor element is preferably 100 μm or less. When glass particles having a particle diameter of 100 μm or less are used, a smooth coating film is easily obtained. In addition, the average particle diameter of the glass particles is more preferably 50 μm or less, and still more preferably 10 μm or less. In addition, although the lower limit is not specifically limited, It is preferable that it is 0.01 micrometer or more.

Here, the average particle diameter of the glass containing the acceptor element means the particle diameter D50% corresponding to the cumulative volume of 50% from the diameter side in the particle size distribution, and can be measured with a laser scattering diffraction particle size distribution measuring device or the like.

Glass particles containing acceptor elements were produced using the following steps.

First, raw materials, for example, an acceptor element-containing substance and a glass component substance are weighed and filled into a crucible. Examples of the material of the crucible include platinum, platinum-rhodium, iridium, alumina, quartz, carbon, and the like, and can be appropriately selected in consideration of melting temperature, atmosphere, reactivity with molten material, contamination of impurities, and the like.

Next, heating is performed at a temperature corresponding to the composition of the glass in an electric furnace to form a molten liquid. At this time, stirring is preferably performed so that the melt becomes uniform. The obtained melt is flowed onto a zirconia substrate, a carbon substrate, or the like to vitrify the melt. Then, the glass is pulverized into a powder form. For pulverization, known devices such as jet mills, bead mills, and ball mills can be used.

The content ratio of the glass particles containing an acceptor element in the composition for forming a p-type diffusion layer is determined in consideration of applicability, diffusibility of the acceptor element, and the like. Usually, the content ratio of the glass particles in the composition for forming a p-type diffusion layer is preferably 0.1% by mass to 95% by mass, more preferably 1% by mass to 90% by mass, still more preferably 1.5% by mass to 85% by mass, particularly preferably It is 2 mass % - 80 mass %.

The content of the inorganic compound component in the total solids of the p-type diffusion layer forming composition is preferably 40% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, particularly preferably 80% by mass or more.

The content ratio of glass particles containing an acceptor element in the inorganic compound component is preferably 50% by mass or more, more preferably 75% by mass or more, still more preferably 85% by mass or more, particularly preferably 90% by mass or more.

The dispersion medium that can be used in the p-type diffusion layer-forming composition is the same as the dispersion medium exemplified in the n-type diffusion layer-forming composition, and the preferred dispersion medium is also the same.

The content ratio of the dispersion medium in the composition for forming a p-type diffusion layer is determined in consideration of applicability, acceptor element concentration, and the like. In consideration of applicability, the viscosity of the composition for forming a p-type diffusion layer is preferably 10 mPa·s to 1,000,000 mPa·s, more preferably 50 mPa·s to 500,000 mPa·s.

(semiconductor substrate)

The semiconductor substrate is not particularly limited, and ordinary semiconductor substrates can be used. Examples include silicon substrates, gallium phosphide substrates, gallium nitride substrates, diamond substrates, aluminum nitride substrates, indium nitride substrates, gallium arsenide substrates, germanium substrates, zinc selenide substrates, zinc telluride substrates, and cadmium telluride substrates , cadmium sulfide substrate, indium phosphide substrate, silicon carbide substrate, silicon germanium substrate, copper indium selenide substrate, etc. When used in a solar cell element, the semiconductor element is preferably a silicon substrate, a germanium substrate, or a silicon carbide substrate, more preferably a silicon substrate.

(Manufacturing method of semiconductor substrate)

In the manufacturing method of the semiconductor substrate of the present invention, in the first diffusion step, the composition for forming a p-type diffusion layer or the composition for forming an n-type diffusion layer is applied to at least a part of the semiconductor substrate, and then the acceptor is formed by heat treatment. The element or donor element diffuses into the semiconductor substrate to form a p-type diffusion layer or an n-type diffusion layer. Moreover, in the second diffusion step, at least a part of the heat-treated product of the p-type diffusion layer forming composition or the heat-treated product of the n-type diffusion layer forming composition is used as a mask to diffuse phosphorus or boron into the semiconductor substrate to form an n-type diffusion layer. diffusion layer or p-type diffusion layer.

The first diffusion step and the second diffusion step can be performed in series. For example, when the gas diffusion method is applied in the second diffusion process, the heat treatment in the first diffusion process can be performed in a gas atmosphere (for example, nitrogen atmosphere) that does not contain dopants and acceptors, and then switch to The gas atmosphere containing a dopant or an acceptor is continuously transferred from the first diffusion step to the second diffusion step, and a series of heat treatment steps are set.

In the manufacturing method of the semiconductor substrate of this invention, you may further have the process of forming a passivation layer on a p-type diffused layer and an n-type diffused layer. The passivation layer preferably contains at least one selected from silicon oxide, silicon nitride, and aluminum oxide.

Hereinafter, an example of a method for manufacturing a semiconductor substrate of the present invention will be described in a method for manufacturing a back contact type solar cell element. In this method of manufacturing a back contact solar cell element, a method in which a silicon substrate is used as a semiconductor substrate, a p ⁺ layer is formed in a first diffusion step and an n ⁺ layer is formed in a second diffusion step will be described. However, the present invention is not limited to this sequence of steps, and a p ⁺ layer may be formed after forming an n ⁺ layer. In this case, the terms n and p are interchanged, the acceptor element is changed to a donor element, and phosphorus Read it as boron.

In the method of manufacturing a back-contact solar cell element, first, a damaged layer located on the surface of a silicon substrate, for example, an n-type silicon substrate is etched using an acidic or alkaline solution to remove the damaged layer. For example, the damaged layer located on the surface of the silicon substrate can be removed by immersing the silicon substrate in a 30% by mass or more high-concentration NaOH aqueous solution heated to about 80° C. for 5 minutes or more.

Next, only the light-receiving surface side of the silicon substrate is etched using an alkaline solution to form a fine uneven structure called a texture structure on the light-receiving surface. The texture structure can be formed, for example, by immersing a silicon substrate provided with a protective layer on the portion where the texture structure is not desired, in a liquid containing potassium hydroxide and isopropyl alcohol (IPA) at about 80°C.

In order to form a textured structure only on one side of the silicon substrate, it can be formed by applying a water-resistant resist on the other side of the silicon substrate, immersing the entire silicon substrate in an aqueous potassium hydroxide solution, or using a floating device to only One side of the silicon substrate was immersed in an aqueous potassium hydroxide solution. When a resist is used, the resist is removed after the texture formation step.

Next, the composition for forming a p-type diffusion layer is patterned on the back surface of the silicon substrate opposite to the light-receiving surface, followed by heat treatment to form a p ⁺ layer on the back surface of the silicon substrate.

The method of imparting the p-type diffused layer forming composition is not particularly limited, and generally used methods can be employed. For example, printing methods such as screen printing method and gravure printing method, spin coating method, brush coating method, spray method, doctor blade method, roll coating method, inkjet method, etc. can be used, preferably printing method, spray method, inkjet method, etc. can be used. patterning method.

There is no particular limitation on the amount of the composition for forming a p-type diffusion layer. For example, the composition for forming a p-type diffusion layer can be applied to a silicon substrate so that the amount of glass particles is 0.01 g/m ² to 100 g/m ² , preferably 0.1 g/m ² to 10 g/m ² .

After applying the p-type diffusion layer forming composition on the silicon substrate, a heating step of removing at least a part of the dispersion medium may be provided. In the heating step, for example, by performing heat treatment at 100°C to 300°C, at least a part of the solvent can be volatilized. In addition, for example, at least a part of the binder may be removed by heat treatment at 200°C to 700°C.

The heat treatment temperature for forming the p-type diffusion layer is preferably 800°C to 1100°C, more preferably 850°C to 1050°C, still more preferably 870°C to 1030°C, particularly preferably 900°C to 1000°C.

The gas atmosphere for the heat treatment for forming the p-type diffusion layer is not particularly limited, but is preferably a mixed gas atmosphere of nitrogen, oxygen, argon, helium, xenon, neon, krypton, or the like.

Next, while leaving the heat-treated product of the p-type diffusion layer-forming composition as a mask layer, an n-type diffusion layer was formed. The n-type diffusion layer can be formed by any of the gas diffusion method and the coating diffusion method. In the gas diffusion method, phosphorus is diffused into the silicon substrate by heating the silicon substrate to a temperature of 750° C. to 950° C. while flowing bubbling gas such as POCl ₃ . In the coating diffusion method, a liquid containing phosphoric acid, ammonium dihydrogen phosphate, phosphorus oxide, phosphoric acid ester, etc. is applied to a silicon substrate, and then the silicon substrate is heated to a temperature of 750°C to 950°C to diffuse phosphorus into the silicon substrate . The imparting method is not particularly limited, and generally used methods can be used. For example, printing methods such as screen printing method and gravure printing method, spin coating method, brush coating method, spray method, doctor blade method, roll coating method, inkjet method, etc. can be used, and printing method, spray method, and inkjet method are preferred. and other methods capable of patterning.

Even when the n-type diffusion layer is formed in the first diffusion step and then the p-type diffusion layer is formed in the second diffusion step, any of the gas diffusion method and the coating diffusion method may be used in the second diffusion step. When the p-type diffusion layer is formed by the polysurface gas diffusion method, the silicon substrate is heated to a temperature of 850° C. to 1050° C. to diffuse boron into the silicon substrate while flowing bubbling gas such as BBr ₃ or BCl ₃ . In the case of forming a p-type diffusion layer by coating diffusion, a liquid containing boric acid, boron oxide, boric acid ester, etc. is applied to a silicon substrate, and then the silicon substrate is heated to a temperature of 850°C to 1050°C to diffuse boron into the silicon substrate. in the silicon substrate.

Next, an antireflection layer is formed on the light receiving surface. Here, as the antireflection layer, for example, a nitride layer formed by plasma CVD can be used. In addition, it is preferable to form a passivation layer on the back side. Examples of the passivation layer include a thermal oxide layer, an aluminum oxide layer, a SiNx layer, and an amorphous silicon layer, which can be formed by a vapor deposition method or a coating method. In the case of a SiNx layer, both passivation and anti-reflection functions can be combined. The passivation layer may be a single-layer structure, or a multi-layer structure such as a two-layer structure or a three-layer structure. For example, passivation may be performed on a silicon substrate in the order of a thermal oxide layer and a SiNx layer.

Next, electrodes are formed on the back surface of the silicon substrate. A generally used method can be used without particular limitation in forming the electrode.

For example, a metal paste for surface electrodes containing metal particles and glass particles is provided on the diffusion layer forming region to form a desired shape, and heat treatment (firing) is performed to make the p-type diffusion layer and the n-type diffusion layer Surface electrodes are formed on the upper electrode formation region. As the metal paste for surface electrodes, for example, a silver paste or the like commonly used in this technical field can be used.

Next, another example of the manufacturing method of the semiconductor substrate of the present invention will be described in the manufacturing method of the double-side light-receiving type solar cell. In this method of manufacturing a double-sided light-receiving solar cell, a method in which a silicon substrate is used as a semiconductor substrate, a p ⁺ layer is formed in a first diffusion step, and an n ⁺ layer is formed in a second diffusion step will be described. However, the present invention is not limited to this sequence of steps, and a p ⁺ layer may be formed after forming an n ⁺ layer. In this case, the terms n and p are interchanged, the acceptor element is changed to a donor element, and phosphorus Read it as boron.

In the method of manufacturing a double-sided light-receiving solar cell, first, a damaged layer located on the surface of a silicon substrate, for example, an n-type silicon substrate is etched using an acidic or alkaline solution to remove the damaged layer. For example, the damaged layer located on the surface of the silicon substrate can be removed by immersing the silicon substrate in a 30% by mass or more high-concentration NaOH aqueous solution heated to about 80° C. for 5 minutes or more.

Next, both surfaces of the silicon substrate are etched using an alkaline solution to form a fine uneven structure called a texture structure on both surfaces. The texture structure can be formed, for example, by immersing the silicon substrate in a liquid containing potassium hydroxide and isopropyl alcohol (IPA) at about 80°C.

Next, the p-type diffusion layer-forming composition is applied to at least a part of the silicon substrate, and the silicon substrate to which the p-type diffusion layer-forming composition is applied is heat-treated to form a p-type diffusion layer locally.

The method of providing the p-type diffused layer forming composition is not particularly limited, and a commonly used method can be used. For example, printing methods such as screen printing method and gravure printing method, spin coating method, brush coating method, spray method, doctor blade method, roll coating method, inkjet method, etc. can be used, preferably printing method, spray method, inkjet method, etc. can be used. patterning method.

There is no particular limitation on the amount of the composition for forming a p-type diffusion layer. For example, the composition for forming a p-type diffusion layer can be applied to a silicon substrate so that the amount of glass particles is 0.01 g/m ² to 100 g/m ² , preferably 0.1 g/m ² to 10 g/m ² .

After applying the p-type diffusion layer-forming composition to the silicon substrate, a heating step of removing at least a part of the dispersion medium may be provided. In the heating step, for example, by performing heat treatment at 100°C to 300°C, at least a part of the solvent can be volatilized. In addition, for example, at least a part of the binder may be removed by heat treatment at 200°C to 700°C.

The heat treatment temperature for forming the p-type diffusion layer is preferably 800°C to 1100°C, more preferably 850°C to 1050°C, still more preferably 870°C to 1030°C, particularly preferably 900°C to 1000°C.

The gas atmosphere in the heat treatment for forming the p-type diffusion layer is not particularly limited, but is preferably a mixed gas atmosphere of nitrogen, oxygen, argon, helium, xenon, neon, krypton, or the like.

Next, while leaving the heat-treated product of the p-type diffusion layer-forming composition as a mask layer, an n-type diffusion layer was formed. The n-type diffusion layer can be formed by any of the gas diffusion method and the coating diffusion method. In the gas diffusion method, phosphorus is diffused into the silicon substrate by heating the silicon substrate to a temperature of 750° C. to 950° C. while flowing N ₂ bubbling gas such as POCl ₃ . In the coating diffusion method, a liquid containing phosphoric acid, ammonium dihydrogen phosphate, phosphorus oxide, phosphoric acid ester, etc. is applied to a silicon substrate, and then the silicon substrate is heated to a temperature of 750°C to 950°C to diffuse phosphorus into the silicon substrate . The imparting method is not particularly limited, and generally used methods can be used. For example, printing methods such as screen printing method and gravure printing method, spin coating method, brush coating method, spray method, doctor blade method, roll coating method, inkjet method, etc. can be used, and printing method, spray method, and inkjet method are preferred. and other methods capable of patterning.

Even in the case where the n-type diffusion layer is formed in the first diffusion step and then the p-type diffusion layer is formed in the second diffusion step, any of the gas diffusion method and the coating diffusion method can be used in the second diffusion step. . In the case of forming the p-type diffusion layer by the polysurface gas diffusion method, the silicon substrate is heated to a temperature of 850°C to 1050°C while flowing N ₂ bubbled with gas such as BBr ₃ and BCl ₃ to diffuse boron into the silicon. substrate. In the case of forming a p-type diffusion layer by coating diffusion, a liquid containing boric acid, boron oxide, boric acid ester, etc. is applied to a silicon substrate, and then the silicon substrate is heated to a temperature of 850°C to 1050°C to diffuse boron into the silicon substrate. in the silicon substrate.

Next, antireflection layers or passivation layers are formed on both surfaces. Here, examples of the layer that can serve both as the antireflection layer and the passivation layer include a nitride layer formed by plasma CVD. In addition, the layer may have a single-layer structure, or may have a multi-layer structure such as a two-layer structure or a three-layer structure. For example, there are layers in which a thermal oxide layer, an aluminum oxide layer, a SiNx layer, and an amorphous silicon layer are stacked, and it can be formed by vapor deposition methods such as plasma CVD, ALD (atomic layer deposition), or coating methods. .

Next, electrodes are respectively formed on both surfaces of the silicon substrate. A generally used method can be used without particular limitation in forming the electrode.

For example, a metal paste for surface electrodes containing metal particles and glass particles is provided on the diffusion layer forming region to form a desired shape, and heat treatment (firing) is performed to make the p-type diffusion layer and the n-type diffusion layer Surface electrodes are formed on the upper electrode formation region. As the metal paste for surface electrodes, for example, a silver paste or the like commonly used in this technical field can be used.

＜Method for manufacturing solar cell elements＞

The manufacturing method of the solar cell element of this invention has the process of forming an electrode on the p-type diffused layer or the n-type diffused layer of the semiconductor substrate obtained by the said manufacturing method.

Hereinafter, an embodiment of a method for manufacturing a solar cell element will be described with reference to the drawings.

FIG. 1 is a diagram showing, as a cross-sectional view, process diagrams schematically showing an example of a method for manufacturing a back contact solar cell element according to the present embodiment. However, the present invention is not limited by this process diagram.

An example in which an n-type silicon substrate is used as a silicon substrate will be described with reference to FIG. 1 . First, an n-type silicon substrate 10 having a thickness of approximately 50 μm to 300 μm is prepared. The n-type silicon substrate 10 is obtained by slicing a single crystal or polycrystalline silicon ingot or the like formed by the CZ method, FZ method, EFG method, casting method, etc., and has a thickness of, for example, 1×10 ¹⁵ cm ⁻³ to 1×10 ¹⁹ cm ^-3 or so of phosphorus and other n-type impurities. Next, the n-type silicon substrate 10 is preferably cleaned with an aqueous alkali solution. By washing with an aqueous alkali solution, organic substances, particles, and the like existing on the surface of the n-type silicon substrate 10 can be removed, and the passivation effect can be further improved. As a method of washing with an aqueous alkali solution, generally known RCA washing and the like can be exemplified. For example, by immersing the n-type silicon substrate 10 in a mixed solution of ammonia water-hydrogen peroxide and treating it at 60° C. to 80° C., organic substances and particles can be removed and cleaned. The cleaning time is preferably 10 seconds to 10 minutes, more preferably 30 seconds to 5 minutes.

Next, with respect to the n-type silicon substrate 10 shown in FIG. 1( a ), a textured structure (pyramidal shape, not shown) is formed on the light receiving surface (surface) by alkali etching or the like to suppress reflection of sunlight from the light receiving surface. Thereafter, as shown in FIG. 1( b ), the p-type diffused layer forming composition 11 is applied to a part of the back surface opposite to the light receiving surface. As shown in FIG. 1( c ), thermal diffusion is performed to form the p-type diffusion layer 12 . At this time, the p-type diffusion layer-forming composition 11 becomes a heat-treated product 11' through heat treatment for thermal diffusion. As the p-type diffusion layer forming composition 11, a diffusion paste containing glass particles containing boron, aluminum, or gallium can be used. As thermal diffusion temperature, it is preferable to set it as 850 degreeC - 1050 degreeC. The p-type diffused layer composition of the present invention uses low-volatility glass particles as a dopant, and since the dopant does not volatilize easily at a high temperature for thermal diffusion, the dopant does not easily diffuse beyond the portion to which it was applied.

As shown in FIG. 1( d ), the silicon substrate is heated to 750° C. to 950° C. while bubbling phosphorus oxychloride, and the phosphosilicate glass layer 13 and the n-type diffusion layer 14 are collectively formed. The heat-treated product 11' of the p-type diffusion layer-forming composition serves as a mask layer and suppresses the diffusion of phosphorus to the portion where the p-type diffusion layer 12 is formed.

Next, as shown in Fig. 1(e), the heat-treated product 11' of the p-type diffusion layer forming composition and the phosphosilicate glass layer 13 are removed by immersing in an etching solution such as hydrofluoric acid.

Next, as shown in FIG. 1( f ), an antireflection layer and passivation layer 15 is formed on the light receiving surface and the back surface. As the antireflection layer and passivation layer 15, a silicon nitride layer, a titanium oxide layer, a silicon oxide layer, an aluminum oxide layer, etc. are mentioned. On the rear surface, the antireflection layer and passivation layer may be formed on the entire surface or a part of the area, and the part belonging to the contact portion with the electrode may be etched. Compounds such as ammonium fluoride can be used for etching. In addition, when the antireflection layer and passivation layer 15 is a silicon nitride layer, ohmic contact can also be obtained by using a paste containing glass particles having firethrough properties as the paste for electrode formation. Between the anti-reflection layer and passivation layer 15 and the n-type silicon substrate 10, there may also be a surface protection layer (not shown) such as silicon oxide or aluminum oxide, and the anti-reflection layer and passivation layer 15 may be partially changed. composition.

Thereafter, as shown in FIG. 1( g ), the electrode-forming paste is applied on the back side, followed by heat treatment to form p-electrode 16 and n-electrode 17 . By using a paste containing glass particles having fire-through properties as the paste for electrode formation, even if the antireflection layer and passivation layer 15 is formed on the entire back surface, the antireflection layer and passivation layer 15 can be penetrated and diffused. An electrode is formed on the layer, thereby obtaining an ohmic contact. As described above, a solar cell element can be obtained.

FIG. 2 is a cross-sectional view showing process diagrams schematically showing an example of a method of manufacturing a double-side light-receiving type solar cell element according to the present embodiment. However, the present invention is not limited by this process diagram. In FIG. 2 , an n-type silicon substrate is used as a silicon substrate for description.

First, it is preferable to wash the n-type silicon substrate 10 with an aqueous alkali solution. By washing with an aqueous alkali solution, organic substances, particles, and the like existing on the surface of the n-type silicon substrate 10 can be removed, and the passivation effect can be further improved. As a method of washing with an aqueous alkali solution, generally known RCA washing and the like can be exemplified. For example, by immersing the n-type silicon substrate 10 in a mixed solution of ammonia water-hydrogen peroxide and treating it at 60° C. to 80° C., organic substances and particles can be removed and cleaned. The cleaning time is preferably 10 seconds to 10 minutes, more preferably 30 seconds to 5 minutes.

Next, with regard to the n-type silicon substrate 10 shown in FIG. 2( a ), a textured structure (pyramidal shape, not shown) is formed on both surfaces by alkali etching or the like to suppress reflection of sunlight. After that, as shown in FIG. 2( b ), the p-type diffusion layer forming composition 11 is applied to one surface. Next, as shown in FIG. 2( c ), thermal diffusion is performed to form the p-type diffusion layer 12 . At this time, the p-type diffusion layer-forming composition 11 becomes a heat-treated product 11' through heat treatment for thermal diffusion. As the p-type diffusion layer forming composition 11, a diffusion paste containing glass particles containing boron, aluminum, or gallium can be used. As thermal diffusion temperature, it is preferable to set it as 850 degreeC - 1050 degreeC. The p-type diffused layer composition of the present invention uses low-volatility glass particles as a dopant, and since the dopant does not volatilize easily at a high temperature for thermal diffusion, the dopant does not easily diffuse beyond the portion to which it was applied.

As shown in FIG. 2( d ), the n-type silicon substrate 10 is heated to 750° C. to 950° C. while bubbling phosphorus oxychloride, and the phosphosilicate glass layer 13 and the n-type diffusion layer 14 are collectively formed. The heat-treated product 11' of the p-type diffusion layer-forming composition serves as a mask layer, and can suppress the diffusion of phosphorus to the back surface on which the p-type diffusion layer 12 is formed.

Next, as shown in Fig. 2(e), the heat-treated product 11' of the p-type diffusion layer forming composition and the phosphosilicate glass layer 13 are removed by immersing in an etching solution such as hydrofluoric acid.

Next, as shown in FIG. 2( f ), an antireflection layer and passivation layer 15 is formed on the light receiving surface and the back surface. As the antireflection layer and passivation layer 15, a silicon nitride layer, a titanium oxide layer, a silicon oxide layer, an aluminum oxide layer, etc. are mentioned. The antireflection layer and passivation layer 15 may be formed on the whole or a part of the light-receiving surface, or may be etched at a portion that is in contact with an electrode. Compounds such as ammonium fluoride can be used for etching. Moreover, when the antireflection layer and passivation layer 15 is a silicon nitride layer, ohmic contact can also be acquired by using the paste containing the glass particle which has fire-through property as the paste for electrode formation. Between the anti-reflection layer and passivation layer 15 and the n-type silicon substrate 10, there may also be surface protection layers (not shown) such as silicon oxide and aluminum oxide, and the composition of the anti-reflection layer and passivation layer 15 may be locally changed. .

Thereafter, as shown in FIG. 2( g ), the electrode-forming paste is applied to the light-receiving surface and the back surface, respectively, and then heat-treated to form the p-electrode 16 and the n-electrode 17 . By using a paste containing fire-through glass particles as the paste for electrode formation, even if the antireflection layer and passivation layer is formed on the entire back surface, the antireflection layer and passivation layer can be penetrated and formed on the diffusion layer. Electrodes are formed so that ohmic contacts are obtained. As described above, a solar cell element can be obtained.

＜Solar Cell Elements＞

The solar cell element of the present invention is obtained by the above-mentioned production method. Accordingly, in the solar cell element of the present invention, it is possible to suppress formation of a diffusion layer in an unnecessary region of the semiconductor substrate, and to improve cell performance.

In the solar cell element, wiring materials such as tab wires are arranged on the electrodes, and a plurality of solar cell elements are connected via the wiring material to form a solar cell module. In addition, the solar cell module may be configured by sealing with a sealing material.

Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. It should be noted that, unless otherwise specified, all reagents were used as raw materials. In addition, unless otherwise specified, "part" and "%" are based on mass.

[Example 1]

Glass particles (containing B ₂ O ₃ , SiO ₂ and CaO as main components, each containing 30% by mass, 50% by mass and 20% by mass) 10 g, 6 g of ethyl cellulose, and 84 g of terpineol were mixed and pasted to prepare a p-type diffusion layer forming composition.

In addition, the shape of a glass particle was observed and judged using the TM-1000 scanning electron microscope of Hitachi High-tech Co., Ltd.. The average particle diameter of glass was calculated using Beckman Coulter Co., Ltd.'s LS13320 laser scattering diffraction particle size distribution analyzer (measurement wavelength: 632 nm). The softening point of the glass was obtained from a differential thermal (DTA) curve using a DTG-60H differential thermal-thermogravimetric simultaneous measuring device of Shimadzu Corporation. In the differential thermal analysis measurement, using α-alumina as a reference, the measurement was performed at a heating rate of 10 K/min while flowing air at a rate of 5 mL/min. The second endothermic peak of the differential curve of the obtained DTA curve was calculated as the softening point.

Next, a p-type diffusion layer-forming composition was applied in a solid form (beta shape) on one side of the n-type silicon substrate (surface texture processing) by screen printing, and dried at 150° C. for 1 minute.

Next, in a diffusion furnace (Koyo Thermal Systems Co., Ltd., 206A-M100) with O ₂ : 8 L/min, N ₂ : 2 L/min, put the n-type silicon substrate in a state set at 700°C, Thereafter, the temperature was raised to 950° C. at 15° C./min, and heat-treated at 950° C. for 30 minutes to form a p-type diffusion layer. Next, the temperature was lowered at 10°C/min to 830°C, and at 830°C, in a system of circulating O ₂ : 0.3 L/min, N ₂ : 4.5 L/min, N ₂ bubbling POCl ₃ gas: 1.5 L/min After treatment in the diffusion furnace for 5 minutes, stop the flow of N ₂ bubbled with POCl ₃ gas, and heat-treat at the same temperature for 12 minutes in the gas of O ₂ : 0.3 L/min, N ₂ : 4.5 L/min, and the p-type An n-type diffused layer is formed outside the region of the diffused layer composition. Thereafter, the temperature was lowered to 700° C. at 10° C./min, and the n-type silicon substrate was taken out from the diffusion furnace.

Next, the glass layer (the heat-treated product 11' of the composition for forming a p-type diffusion layer and the phosphosilicate glass layer 13) remaining on the surface of the n-type silicon substrate was removed by hydrofluoric acid. The average value of the sheet resistance of the p-type diffusion layer region (electrode formation region) to which the p-type diffusion layer-forming composition was applied was 46 Ω/□. The average value of the sheet resistance of the n-type diffusion layer region (electrode formation region) was 55Ω/□.

Next, the edge (side surface) of the n-type silicon substrate was immersed in a 10% by mass NaOH aqueous solution heated to 80°C for 1 min to perform edge insulation treatment.

Next, silicon nitride was vapor-deposited on the surface on which the n-type diffusion layer was formed, thereby forming an antireflection layer. In addition, aluminum oxide was vapor-deposited on the surface on which the p-type diffusion layer was formed by the ALD method to form a passivation layer.

Next, silver electrodes (DuPont, PV159A) were formed on both surfaces by screen printing using a printing mask. Next, after drying at 150° C., it was fired at 700° C. using a tunnel-type firing furnace (Noritake Co., Ltd.) to produce a solar cell element. The power generation characteristics of the manufactured solar cell elements were evaluated using a solar simulator (Wacom Electric Co., Ltd., XS-155S-10). Regarding the power generation performance, Jsc (short-circuit current density), Voc (open-circuit voltage), FF (fill factor) and η (conversion efficiency) were tested in accordance with JIS-C-8913 (2005) and JIS-C-8914 (2005), respectively. determined. Jsc (short circuit current density), Voc (open circuit voltage), FF (fill factor) and η (conversion efficiency) were 30.93 mA/cm ² , 594 mV, 0.78 and 14.3%, respectively.

(Evaluation of shielding performance)

The composition for forming a p-type diffusion layer was applied to an n-type silicon substrate (mirror-finished surface), and placed in a diffusion furnace with O ₂ : 8 L/min and N ₂ : 2 L/min at 700°C. Insert the n-type silicon substrate, then raise the temperature to 950°C at 15°C/min, and heat-treat at 950°C for 30 minutes to form a p-type diffusion layer. Next, the temperature was lowered at 10°C/min to 830°C, and at 830°C, O ₂ : 0.3 L/min, N ₂ : 4.5 L/min, N ₂ bubbling POCl ₃ gas: 1.5 L/min were diffused. After processing in the furnace for 5 minutes, stop the flow of N ₂ bubbled with POCl ₃ gas, and heat-treat at the same temperature for 12 minutes in the gas of O ₂ : 0.3 L/min, N ₂ : 4.5 L/min, and the p-type diffusion An n-type diffused layer is formed outside the region of the heat-treated product of the layer composition. Thereafter, the temperature was lowered to 700° C. at 10° C./min, and the n-type silicon substrate was taken out from the diffusion furnace.

Next, the glass layer remaining on the surface of the n-type silicon substrate (the heat-treated product 11' of the composition for forming a p-type diffusion layer and the phosphosilicate glass layer 13) is removed by hydrofluoric acid. Thereafter, the concentration of phosphorus element in the n-type silicon substrate surface layer of the p-type diffusion layer forming composition application portion was measured using SIMS (secondary ion mass spectrometer, CAMECA Corporation, IMS-7F). The primary ion uses Cs ⁺ . The phosphorus concentration in the surface layer of the n-type silicon substrate was below the detection limit (10 ¹⁶ atom/cm ³ ), and it can be seen that the heat-treated product of the p-type diffusion layer forming composition inhibits the diffusion of phosphorus.

[Example 2]

Glass particles (containing P ₂ O ₅ , SiO ₂ , and CaO as main components, each containing 30% by mass, 60% by mass, and 10% by mass), 10 g of ethyl cellulose, and 84 g of terpineol were mixed and pasted to prepare an n-type diffusion layer forming composition. The softening point of the glass particles was 780°C.

Next, the n-type diffused layer-forming composition was solidly applied to one side of the n-type silicon substrate (surface texture processing) by screen printing, and dried at 150° C. for 1 minute.

Next, in a diffusion furnace (Koyo Thermal Systems Co., Ltd., 206A-M100) that flows N ₂ : 10 L/min, put the n-type silicon substrate in a state set at 700°C, and then set it at 15°C/min Raise the temperature to 930°C, and after reaching 930°C, heat treatment at 930°C while flowing N ₂ : 19 L/min, O ₂ : 0.06 L/min, N ₂ bubbling BBr ₃ : 0.06 L/min For 30 minutes, the n-type diffusion layer and the p-type diffusion layer were formed together. Thereafter, the gas was switched to N ₂ : 10 L/min, the temperature was lowered to 700° C. at 10° C./min, and the substrate was taken out from the diffusion furnace.

Next, the glass layer (the heat-treated product of the n-type diffusion layer forming composition and the borosilicate glass layer) remaining on the surface of the n-type silicon substrate was removed by hydrofluoric acid.

The average value of the sheet resistance of the n-type diffusion layer region (electrode formation region) to which the n-type diffusion layer-forming composition was applied was 75Ω/□. The average value of the sheet resistance of the p-type diffusion layer region (electrode formation region) was 38Ω/□.

Next, the edge (side surface) of the silicon substrate was immersed in a 10% by mass NaOH aqueous solution heated to 80° C. for 1 minute to perform edge insulation treatment.

Next, silicon nitride was vapor-deposited on the surface on which the n-type diffusion layer was formed, thereby forming an antireflection layer. In addition, aluminum oxide was vapor-deposited on the surface on which the p-type diffusion layer was formed by the ALD method to form a passivation layer.

Next, silver electrodes (DuPont, PV159A) were formed on both surfaces by screen printing using a printing mask. Next, after drying at 150 degreeC, it baked at 700 degreeC using the tunnel type firing furnace (Noritake Co., Ltd.), and produced the solar cell element. The power generation characteristics of the manufactured solar cell elements were evaluated using a solar simulator (Wacom Electric Co., Ltd., XS-155S-10). Regarding the power generation performance, Jsc (short-circuit current density), Voc (open-circuit voltage), FF (fill factor) and η (conversion efficiency) were tested in accordance with JIS-C-8913 (2005) and JIS-C-8914 (2005), respectively. determined. Jsc (short circuit current density), Voc (open circuit voltage), FF (fill factor) and η (conversion efficiency) were 30.67 mA/cm ² , 588 mV, 0.79 and 14.2%, respectively.

(Evaluation of shielding performance)

Apply the composition for forming an n-type diffusion layer to an n-type silicon substrate (mirror surface finish), and set the temperature at 700 in a diffusion furnace (Koyo Thermal Systems Co., Ltd., 206A-M100) that flows N ₂ : 10 L/min. Put the substrate in the state of ℃, then raise the temperature to 930℃ at 15℃/min, and after reaching 930℃, flow N ₂ : 19L/min, O ₂ : 0.06L/min, N ₂ with BBr ₃ bubbled : An n-type diffusion layer and a p-type diffusion layer were collectively formed by heat treatment at 930° C. for 30 minutes in a gas state of 0.06 L/min. Thereafter, the gas was switched to N ₂ : 10 L/min, the temperature was lowered to 700° C. at 10° C./min, and the n-type silicon substrate was taken out from the diffusion furnace.

Next, the glass layer (the heat-treated product of the n-type diffusion layer forming composition and the borosilicate glass layer 13 ) remaining on the surface of the n-type silicon substrate was removed by hydrofluoric acid. Thereafter, the concentration of boron element in the surface layer of the n-type silicon substrate in the n-type diffusion layer-forming composition-applied portion was measured using SIMS (secondary ion mass spectrometer, CAMECA Corporation, IMS-7F). The primary ion uses Cs ⁺ . The boron concentration in the surface layer of the n-type silicon substrate was below the detection limit (10 ¹⁶ atom/cm ³ ), and it can be seen that the heat-treated product of the n-type diffusion layer forming composition inhibits the diffusion of boron.

[Example 3]

Glass particles (mainly composed of B ₂ O ₃ , SiO ₂ , CaO, Al ₂ O ₃ and BaO, each containing 20 %, 65% by mass, 5% by mass, 5% by mass and 5% by mass) 10 g, 6 g of ethyl cellulose, and 84 g of terpineol were mixed and paste-formed to prepare p-type diffusion layer forming composition 2.

Evaluation was performed in the same manner as in Example 1 except that the p-type diffused layer-forming composition 2 was used instead of the p-type diffused layer-forming composition.

The average value of the sheet resistance of the portion to which the p-type diffusion layer-forming composition 2 was applied was 43Ω/□, and the thin layer of the n-type diffusion layer region formed on the surface opposite to the surface to which the p-type diffusion layer-forming composition was applied The average value of the resistance was 55Ω/□.

Regarding power generation performance, Jsc (short-circuit current density), Voc (open-circuit voltage), FF (fill factor), and η (conversion efficiency) were 30.91 mA/cm ² , 595 mV, 0.78, and 14.3%, respectively.

The concentration of phosphorus in the surface layer of the n-type silicon substrate in the p-type diffusion layer-forming composition-applied portion was below the detection limit (10 ¹⁶ atom/cm ³ ), and it can be seen that the heat-treated product of the p-type diffusion layer-forming composition 2 inhibits the formation of phosphorus. diffusion.

[Comparative example 1]

10 g of boric acid, 6 g of ethyl cellulose, and 84 g of terpineol were mixed and formed into a paste to prepare a p-type diffusion layer forming composition C.

A solar cell element was produced and evaluated in the same manner as in Example 1, except that the p-type diffused layer-forming composition C was used instead of the p-type diffused layer-forming composition. Regarding power generation performance, Jsc (short-circuit current density), Voc (open-circuit voltage), FF (fill factor), and η (conversion efficiency) were 27.51 mA/cm ² , 561 mV, 0.76, and 11.7%, respectively.

(Evaluation of shielding performance)

In the same manner as in Example 1, the concentration of phosphorus in the p-type diffused layer-forming composition C-applied portion of the silicon substrate was measured. The phosphorus concentration was 10 ¹⁹ atom/cm ³ , and it was seen that phosphorus diffused into the p-type diffusion layer forming composition C imparting portion. This is considered to be because the heat-treated product of the p-type diffused layer forming composition C had cracks and phosphorus was mixed through the cracks. From the above, it can be seen that the shielding performance of the p-type diffused layer-forming composition C is inferior to that of the p-type diffused layer-forming composition.

[Comparative example 2]

10 g of ammonium dihydrogen phosphate, 6 g of ethyl cellulose, and 84 g of terpineol were mixed and formed into a paste to prepare an n-type diffusion layer forming composition C.

A solar cell element was produced and evaluated in the same manner as in Example 2, except that the n-type diffused layer-forming composition C was used instead of the n-type diffused layer-forming composition. Regarding power generation performance, Jsc (short-circuit current density), Voc (open-circuit voltage), FF (fill factor), and η (conversion efficiency) were 27.11 mA/cm ² , 556 mV, 0.76, and 11.5%, respectively.

(Evaluation of shielding performance)

The concentration of boron in the n-type diffused layer-forming composition C application portion of the silicon substrate was measured in the same manner as in Example 2. The concentration of boron was 5×10 ¹⁸ atom/cm ³ , and it was seen that boron diffused into the n-type diffusion layer forming composition C imparting portion. This is considered to be because the heat-treated product of the n-type diffusion layer-forming composition C is porous, and the surface of the silicon substrate cannot be firmly covered with the n-type diffusion layer-forming composition C, so the diffusion of boron cannot be suppressed. From the above, it can be seen that the n-type diffused layer-forming composition C is inferior in shielding performance to the n-type diffused layer-forming composition.

In addition, the disclosure content of Japanese application 2013-257039 is incorporated in this specification as a whole as a reference.

All documents, patent applications, and technical standards described in this specification are incorporated by reference in this specification to the same extent as if each document, patent application, and technical standard were specifically and individually described.

Claims (12)

1. there is a manufacture method for the semiconductor substrate of diffusion layer, comprising:

At least some of imparting p-type diffusion layer on semiconductor substrate is formed the operation of compositions, and described p-diffusion layer forms compositions and contains the glass particle and disperse medium that comprise recipient element；

Described recipient element is made to be diffused into the operation forming p-diffusion layer in described semiconductor substrate by heat treatment；With

Form heat treatment thing at least some of as mask of compositions using described p-diffusion layer, make phosphorus be diffused into the operation forming n-type diffusion layer in described semiconductor substrate.

2. the manufacture method of semiconductor substrate according to claim 1, wherein, described recipient element comprises at least one element in B (boron), Al (aluminum) and Ga (gallium).

3. the manufacture method of semiconductor substrate according to claim 1 and 2, wherein, described in comprise recipient element glass particle contain selected from B₂O₃、Al₂O₃And Ga₂O₃In at least one containing recipient element material with selected from SiO₂、K₂O、Na₂O、Li₂O、BaO、SrO、CaO、MgO、BeO、ZnO、PbO、CdO、Tl₂O、V₂O₅、SnO、ZrO₂、WO₃、MoO₃And at least one glass ingredient material in MnO.

4. there is a manufacture method for the semiconductor substrate of diffusion layer, comprising:

To at least some of operation giving n-type diffusion layer formation compositions on semiconductor substrate, described n-type diffusion layer forms compositions and contains the glass particle and disperse medium that comprise donor element；

Described donor element is made to be diffused into the operation forming n-type diffusion layer in described semiconductor substrate by heat treatment；With

Form heat treatment thing at least some of as mask of compositions using described n-type diffusion layer, make boron be diffused into the operation forming p-diffusion layer in described semiconductor substrate.

5. the manufacture method of semiconductor substrate according to claim 4, wherein, described donor element is at least one in P (phosphorus) and Sb (antimony).

6. the manufacture method of the semiconductor substrate according to claim 4 or 5, wherein, described in comprise donor element glass particle contain selected from P₂O₃、P₂O₅And Sb₂O₃In at least one containing donor element material with selected from SiO₂、K₂O、Na₂O、Li₂O、BaO、SrO、CaO、MgO、BeO、ZnO、PbO、CdO、V₂O₅、SnO、ZrO₂And MoO₃In at least one glass ingredient material.

7. the manufacture method of the semiconductor substrate according to any one of claim 1～6, it is additionally included in the operation forming passivation layer in described p-diffusion layer and described n-type diffusion layer.

8. the manufacture method of semiconductor substrate according to claim 7, wherein, described passivation layer contains at least one in silicon oxide, silicon nitride and aluminium oxide.

9. having a semiconductor substrate for p-diffusion layer and n-type diffusion layer, it is to be obtained by the manufacture method according to any one of claim 1～8.

10. a manufacture method for solar cell device, it has the operation forming electrode in the p-diffusion layer of the semiconductor substrate obtained by the manufacture method according to any one of claims 1 to 3.

11. a manufacture method for solar cell device, it has the operation forming electrode in the n-type diffusion layer of the semiconductor substrate obtained by the manufacture method according to any one of claim 4～6.

12. a solar cell device, it is to be obtained by the manufacture method described in claim 10 or 11.