TWI638388B - Method for diffusing impurity diffusion component and method for manufacturing solar cell - Google Patents

Abstract

The method for diffusing an impurity diffusion component in the same state of the present invention comprises the steps of: polymer containing an alcoholic hydroxyl group containing an impurity diffusion component (A) and thermally decomposing and disappearing at 600 ° C for 30 minutes in an oxygen atmosphere. a step of applying a diffusing agent composition of the compound (B) and the organic solvent (C) on the surface of one side of the first semiconductor substrate to form a diffusing agent layer; and a second semiconductor substrate to which the diffusing agent composition is not applied a step of bonding the surface of one of the surfaces to the diffusing agent layer to form a laminate; and heating the laminate to diffuse the impurity-diffusing component (A) to the first semiconductor substrate and the second semiconductor substrate.

Description

Method for diffusing impurity diffusion component and method for manufacturing solar cell

The present invention relates to a diffusion method for impurity diffusion components and a method for producing a solar cell.

In the past, the fabrication of transistors, diodes, ICs, and the like used a germanium semiconductor device having a P-type region in which boron was diffused. A method of diffusing boron in the ruthenium substrate can be mainly a thermal decomposition method, a counter NB method, a dopant host method, a coating method, or the like. Among these, the coating method is preferably used without requiring an expensive device and uniformly diffusing, and in terms of mass productivity. In particular, a method of applying a coating liquid containing boron by a spin coater or the like is often used.

For example, Patent Document 1 discloses a boron-containing diffusing agent composition used in a diffusing agent coating method such as a spin coating method. The diffusing agent composition is a so-called polyboron film (PBF). Further, Patent Document 1 discloses that a coating liquid for boron diffusion is applied onto the surface of a semiconductor element by a spin-on method or the like, and the formed coating film is dried and then fired at a specific temperature to decompose and burn to remove organic substances. The composition forms a B ₂ O ₃ inorganic film, and then raises the temperature to diffuse boron on the surface of the semiconductor device.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 9-181010

In recent years, in the field of semiconductor manufacturing, particularly in the field of solar cell manufacturing, cost reduction has been demanded. Specifically, for example, when manufacturing a lanthanoid solar cell, it is required to further reduce the amount of use of the coating liquid for diffusion to reduce the cost. On the other hand, in the conventional spin coating method, the amount of the coating liquid used per substrate is large, and there is room for improvement in cost reduction.

Further, the boron diffusion system using the conventional PBF forms a B ₂ O ₃ inorganic film before the boron diffusion as described above. Boron easily scatters from the boron film to the outside of the film. Therefore, boron diffuses to the side of the back side of the substrate or the region of the adjacent substrate which is opposite to the surface of the boron film, which is not intended to diffuse, and is likely to cause outward diffusion. This outward diffusion is a problem to be solved in order to improve the accuracy of impurity diffusion.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a technique for achieving cost reduction in semiconductor manufacturing while suppressing occurrence of out-diffusion.

In order to solve the above problems, the present invention is a diffusion method of an impurity diffusion component. The method for diffusing the impurity diffusion component is characterized by comprising the steps of: coating a diffusing agent composition of the following composition on the first a step of forming a diffusing agent layer on the surface of one side of the semiconductor substrate, and bonding a surface of one side of the second semiconductor substrate on which the diffusing agent composition is not applied to the diffusing agent layer to form a laminate; And heating the laminate to diffuse the impurity diffusion component (A) to the first semiconductor substrate and the second semiconductor substrate; and the diffusing agent composition includes an impurity diffusion component (A) and an oxygen atmosphere. The polymer compound (B) having an alcoholic hydroxyl group and the organic solvent (C) which are thermally decomposed and disappeared by heating at 600 ° C for 30 minutes.

According to this aspect, cost reduction in semiconductor manufacturing can be achieved while suppressing occurrence of out-diffusion.

Another aspect of the invention is a method of manufacturing a solar cell. The solar cell manufacturing method is characterized in that the impurity diffusion component (A) of the first conductivity type is diffused on the semiconductor substrate by one side of the semiconductor substrate by using the diffusion method of the impurity diffusion component in the above-described state. a step of forming an impurity diffusion layer of the first conductivity type on the surface, and diffusing the impurity diffusion component (A) of the second conductivity type on the surface of the other side of the semiconductor substrate on the surface of the other side of the semiconductor substrate a step of forming the impurity diffusion layer of the second conductivity type, a step of providing a first electrode on a surface side of the one side of the semiconductor substrate, and electrically connecting the first electrode to the impurity diffusion layer of the first conductivity type, and A second electrode is provided on the surface side of the other side of the semiconductor substrate, and the second electrode is electrically connected to the impurity diffusion layer of the second conductivity type.

1‧‧‧1st semiconductor substrate

S1, S2‧‧‧ surface

2‧‧‧P type diffuser layer

3‧‧‧2nd semiconductor substrate

4‧‧‧Layer

5‧‧‧P type impurity diffusion layer

6‧‧‧N type diffuser layer

7‧‧‧Layer

8‧‧‧N type impurity diffusion layer

9‧‧‧ Passivation layer

9a‧‧‧Contact hole

10‧‧‧ surface electrode

11‧‧‧Back electrode

100‧‧‧ solar cells

200‧‧‧Diffusion furnace

201‧‧‧ base

202‧‧‧Outer tube

202a, 202b‧‧‧ openings

203‧‧‧ furnace room

204‧‧‧mounting table

206‧‧‧Support members

208‧‧‧ gas supply line

210‧‧‧ gas discharge line

212‧‧‧heater

1(A) to 1(E) are process diagrams showing a method of diffusing an impurity diffusion component and a method of manufacturing a solar cell according to an embodiment.

2(A) to 2(E) are process diagrams showing a method of diffusing an impurity diffusion component and a method of manufacturing a solar cell according to an embodiment.

The invention will now be described with reference to preferred embodiments. However, this is not intended to limit the scope of the invention, but is merely illustrative of the invention.

Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The same or equivalent constituent elements, members, and processing units are denoted by the same reference numerals, and the description thereof will not be repeated. Further, the embodiments are not intended to limit the invention, and all of the features described in the embodiments or combinations thereof are not necessarily essential to the invention.

Referring to Fig. 1(A) to Fig. 1(E) and Figs. 2(A) to 2(E), a method of diffusing an impurity diffusion component and a method of manufacturing a solar cell according to an embodiment will be described. 1(A) to 1(E) and 2(A) to 2(E) are process diagrams of a method of diffusing an impurity diffusion component according to an embodiment and a method of manufacturing a solar cell.

<Modulation of diffusing agent composition>

The diffusing agent composition used in the method for diffusing the impurity-diffusing component of the present embodiment includes the impurity-diffusing component (A), the alcohol-containing hydroxyl group-containing polymer compound (B), and the organic solvent (C).

(impurity diffusion component (A))

The impurity-diffusing component (A) is a compound which is generally used as a dopant in the manufacture of a solar cell. The impurity-diffusing component (A) is an impurity-diffusion component of a P-type (first conductivity type) containing a compound of a group III (Group 13) element, or an N-type (second conductivity type) of a compound containing a group V (Group 15) element. ) Impurity diffusion component. In the step of forming an electrode in a solar cell, a P-type impurity diffusion layer can be formed in the N-type semiconductor substrate, and a P ⁺ type (high concentration P type) can be formed in the P-type semiconductor substrate. Impurity diffusion layer. Further, the N-type impurity diffusion component can form an N-type impurity diffusion layer (impurity diffusion region) in the P-type semiconductor substrate in the step of forming an electrode in the solar cell, and can form an N ⁺ type in the N-type semiconductor substrate. (High concentration N type) impurity diffusion layer.

The compound of the group III element is exemplified by a boric acid ester such as B ₂ O ₃ or trioctyl boron, Al ₂ O ₃ or gallium trichloride, and the like, and the impurity-diffusing component (A) contains one or more of these compounds. The compound of the group V element is exemplified by, for example, P ₂ O ₅ , Bi ₂ O ₃ , Sb(OCH ₂ CH ₃ ) ₃ , SbCl ₃ , As(OC ₄ H ₉ ) ₃ , containing monomethyl phosphate, dimethyl phosphate, Phosphate esters such as monoethyl phosphate, diethyl phosphate, triethyl phosphate, monopropyl phosphate, dipropyl phosphate, monobutyl phosphate, dibutyl phosphate, and tributyl phosphate, etc., impurity diffusion component (A) ) comprising more than one of these compounds. The content of the impurity-diffusing component (A) in the diffusing agent composition is appropriately adjusted depending on the thickness of the impurity diffusion layer formed on the semiconductor substrate or the like. Further, the content of the impurity-diffusing component (A) is preferably from 5 to 60% by mass, more preferably from 10 to 40% by mass, based on the total mass of the solid content of the diffusing agent composition (when the solid content is taken as 100). More preferably 15 to 30% by mass.

(Polymer compound (B) containing an alcoholic hydroxyl group)

The polymer compound (B) having an alcoholic hydroxyl group is a compound which is thermally decomposed and disappeared by heating at 600 ° C for 30 minutes in an oxygen atmosphere. By having this characteristic of the alcohol-containing hydroxyl group-containing polymer compound (B), it is possible to prevent carbon from remaining on the surface of the semiconductor substrate when the impurity-diffusing component (A) is thermally diffused. Therefore, an impurity diffusion layer having a smaller variation in resistance value can be formed. Further, it is possible to avoid the case where the carbon is diffused into the semiconductor substrate together with the thermal diffusion of the impurity-diffusing component (A), and the desired resistance value cannot be obtained. Further, since the diffusibility of the diffusing agent composition can be improved, the impurity-diffusing component (A) can be sufficiently diffused to the second semiconductor substrate bonded to the diffusing agent layer on the first semiconductor substrate to be described later, and the second semiconductor can be used in the second semiconductor. A good impurity diffusion layer is formed on the substrate.

Here, the term "disappearance by thermal decomposition" means that, for example, the polymer compound (B) having an alcoholic hydroxyl group is a total mass of the polymer compound (B) having an alcoholic hydroxyl group of about 95%, preferably about 99%. , better about 100% disappeared.

The polymer compound (B) containing an alcoholic hydroxyl group may, for example, be polyethylene oxide, polyhydroxymethyl acrylate, polyhydroxyethyl acrylate, polyhydroxypropyl acrylate or methacrylate equivalent thereto. Polyhydroxyalkyl acrylate or methacrylate, polyvinyl alcohol, polyethylene condensate Aldehyde, polyvinyl butyral, and the like. These may be used alone or in combination of two or more. The content of the polymer compound (B) having an alcoholic hydroxyl group is preferably from 40 to 95% by mass, more preferably from 60 to 90% by mass, even more preferably 70%, based on the total mass of the solid component of the diffusing agent composition. 85 mass%.

(Organic solvent (C))

The organic solvent (C) may be any one which can dissolve the impurity-diffusing component (A) and the alcohol-containing hydroxyl group-containing polymer compound (B). Specific examples of the organic solvent (C) include, for example, alcohols such as methanol, ethanol, isopropanol, and butanol, and ketones such as acetone, diethyl ketone, and methyl ethyl ketone, methyl acetate, ethyl acetate, and acetic acid. Esters such as butyl ester, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, ethylene glycol monomethyl ether, ethylene glycol single ethyl Monoether glycols such as propyl ether, propylene glycol monomethyl ether (PGME) and propylene glycol monoethyl ether, cyclic ethers such as tetrahydrofuran and dioxane, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether An ether ester such as acetate. These may be used singly or in combination of two or more. The content of the organic solvent (C) is preferably from 50 to 97% by mass, more preferably from 75 to 97% by mass, based on the total mass of the diffusing agent composition.

The diffusing agent composition uniformly mixes the impurity diffusing component (A), the alcoholic hydroxyl group-containing polymer compound (B), and the organic solvent (C), and is prepared by filtration through a membrane filter or the like.

<Formation of P-type diffusing agent layer>

As shown in FIG. 1, for example, an N-type germanium wafer is prepared as the first semiconductor substrate 1. Here, the first semiconductor substrate 1 is a solar cell substrate having a texture structure (not shown) on the surface S1 on one side. Further, the surface S2 (see FIG. 1(E)) on the other side of the first semiconductor substrate 1 may have a textured structure or may have no texture structure. Here, the term "texture structure" refers to a structure in which irregularities are continuously arranged in parallel, and those having irregularities of the same pitch or height are arranged in a regular manner, or those having irregular pitches or heights are randomly arranged. The distance between the concavities and convexities (the distance from the vertex of the convex portion to the surface direction of the deepest portion of the concave portion) is, for example, 1 to 10 μm. The height of the concavities and convexities (the height from the deepest portion of the concave portion to the apex of the convex portion) is, for example, 1 to 10 μm. Light reflection on the surface of the first semiconductor substrate 1 can be prevented by the texture structure. The texture construction can be formed using conventional wet etching methods.

Next, a P-type diffusing agent composition containing a P-type impurity diffusing component (A) is applied onto the surface S1 (the surface having the texture structure side) on one side of the first semiconductor substrate 1 to form a P-type diffusing agent layer 2 . The P-type diffusing agent composition is applied to the first semiconductor substrate 1 by, for example, a spin coating method. After the P-type diffusing agent composition is applied to the first semiconductor substrate 1, the P-type diffusing agent layer 2 is subjected to a drying treatment. The amount of application of the P-type diffusing agent composition to the surface of the first semiconductor substrate is a conventional method in which the impurity-diffusing component is thermally diffused in a state in which the diffusing agent layer is exposed, and the amount of the impurity-diffusing component is diffused to one semiconductor substrate. The same amount.

<Formation of laminates>

Next, as shown in FIG. 1(B), for example, an N-type germanium wafer is prepared as The second semiconductor substrate 3. Here, the second semiconductor substrate 3 is a substrate for a solar cell having a textured structure on the surface S1 on one side. Further, the other surface S2 of the second semiconductor substrate 3 (see FIG. 2(A)) may have a texture structure or may have no texture structure. Then, the surface S1 (the surface having the side of the texture structure) on the side of the second semiconductor substrate 3 on which the P-type diffusing agent composition is not applied is bonded to the surface of the first semiconductor substrate 1 to form a P-type diffusing agent. On layer 2. Thereby, the laminate 4 of the first semiconductor substrate 1, the P-type diffusing agent layer 2, and the second semiconductor substrate 3 is laminated in this order.

<Diffusion of P-type impurity diffusion component (A)>

Next, as shown in FIG. 1(C), the laminate 4 is placed in the diffusion furnace 200. The diffusion furnace 200 is, for example, a conventional vertical diffusion furnace, and includes a base portion 201, an outer cylinder 202, a mounting table 204, a support member 206, a gas supply line 208, a gas discharge line 210, and a heater 212.

The outer cylinder 202 is attached to the base portion 201 such that the axial direction thereof is parallel to the vertical direction, and the furnace portion 203 is formed by the base portion 201 and the outer cylinder 202. The mounting table 204 has a circular shape in plan view and is disposed at the center of the furnace chamber 203. The support member 206 has a columnar shape, and is provided in plural in the circumferential direction of the outer edge portion of the mounting table 204. The interval between the adjacent two supporting members 206 is set to be at a specific portion, and the laminated body 4 can be placed in parallel with the mounting table 204, passing between the two supporting members 206. A plurality of grooves are formed in the side surface of each of the support members 206 at intervals in the axial direction. The laminate 4 is supported by the support member by engaging the outer edge portion with the groove of the support member 206. 206 to support. According to this, the plurality of laminated bodies 4 are spaced apart from each other, and are arranged in a vertical direction in a state of being parallel to each other.

The gas supply line 208 is a line for supplying ambient gas to the furnace chamber 203, and one end thereof is connected to an environmental gas tank (not shown), and the other end is connected to the opening 202a of the outer cylinder 202. The gas discharge line 210 is a line for discharging the gas in the furnace chamber 203, and one end thereof is connected to the opening 202b of the outer tube 202. The heater 212 is provided on the outer circumference of the outer cylinder 202, and is configured to be heatable in the furnace chamber 203.

By arranging the plurality of laminates 4 in the furnace chamber 203, for example, nitrogen gas (N ₂ ) as an ambient gas is supplied from the gas supply line 208 into the furnace chamber 203. Next, the laminate 4 is heated in an N ₂ gas atmosphere, and the P-type impurity diffusion component (A) is diffused to the first semiconductor substrate 1 and the second semiconductor substrate 3. The heating temperature of the laminate 4, that is, the heat diffusion temperature is preferably from 800 to 1000 ° C, more preferably from 850 to 1000 ° C. By setting the thermal diffusion temperature to 800 ° C or higher, the impurity diffusion component (A) is more reliably thermally diffused. Further, by setting the thermal diffusion temperature to 1000 ° C or lower, it is possible to more reliably prevent the impurity diffusion component (A) from diffusing into the semiconductor substrate beyond the desired diffusion region, and to prevent damage of the semiconductor substrate due to heating.

The polymer compound (B) containing an alcoholic hydroxyl group contained in the P-type diffusing agent layer 2 is thermally decomposed and disappeared by heating by the laminate 4. Thereby, the P-type diffusing agent layer 2 is a layer composed of a film of a high-concentration impurity-diffusing component (A). Then, the impurity-diffusing component (A) is diffused from the P-type diffusing agent layer 2 formed by the film to the first semiconductor substrate 1 and The second semiconductor substrate 3. Therefore, the resistance value deviation is made smaller, and an impurity diffusion layer having a desired resistance value can be formed on the semiconductor substrates on both sides.

In the state of the laminate 4, the P-type diffusing agent layer 2 formed on the surface of the first semiconductor substrate 1 is covered with the second semiconductor substrate 3, and the heat of the impurity-diffusing component (A) is applied. diffusion. Therefore, the impurity diffusion component (A) from the P-type diffusing agent layer 2 can be prevented from being released into the gas atmosphere of the furnace interior 203 by the second semiconductor substrate 3. When the second semiconductor substrate 3 is used as a reference, the impurity diffusion component (A) from the P-type diffusing agent layer 2 can be prevented from being released by the first semiconductor substrate 1. Thereby, it is possible to suppress the diffusion of the impurity-diffusing component (A) into a region where the diffusion of the impurity-diffusing component (A) is not intended, that is, to suppress the occurrence of outward diffusion.

The method of preventing outward diffusion considers that the distance between the ruthenium substrates arranged in the diffusion furnace is increased, and the boron released from the boron film of the substrate on one side is prevented from reaching the adjacent ruthenium substrate. However, this method reduces the number of substrates that can be placed at one time in the diffusion furnace, which may hinder high processing quantization. Moreover, it is difficult to prevent the outward diffusion of the back side of itself. Further, a method of covering the mask for preventing outward diffusion to a region where boron diffusion is not scheduled may be considered. However, in this method, the number of manufacturing steps is increased, which may hinder high processing quantization. On the other hand, in the present embodiment, the P-type diffusing agent layer 2 is sandwiched between the first semiconductor substrate 1 and the second semiconductor substrate 3, and the outward diffusion is suppressed. Therefore, the distance between the adjacent laminates 4 can be made closer, and the number of semiconductor substrates which can be subjected to thermal diffusion treatment at one time can be increased. Further, it is not necessary to cover the mask for preventing outward diffusion on the semiconductor substrate. therefore, It does not hinder the high processing quantization of semiconductor manufacturing, and can suppress the occurrence of out-diffusion.

Further, in the related art, a diffusing agent layer is formed on the surface of one semiconductor substrate, and a thermal diffusion treatment of the impurity diffusing component is performed in a state where the diffusing agent layer is exposed. This conventional method considers the release of the impurity-diffusing component into the gas atmosphere, and forms the diffusing agent layer so as to contain an impurity diffusion component of a required amount or more for forming an impurity diffusion layer on one semiconductor substrate. On the other hand, in the present embodiment, the second semiconductor substrate 3 prevents the impurity-diffusing component (A) from diffusing into the gas atmosphere, and the second semiconductor substrate 3 is released into the gas atmosphere without being coated. The impurity diffusion component (A) is used to form an impurity diffusion layer on the second semiconductor substrate 3. Therefore, the impurity diffusion layer can be formed on the two semiconductor substrates in the same amount as that required in the conventional method of forming the impurity diffusion layer for one semiconductor substrate. Therefore, the amount of the diffusing agent composition per semiconductor substrate can be halved, so that the cost of semiconductor manufacturing can be reduced.

Further, since the step of applying the P-type diffusing agent composition to the second semiconductor substrate 3 can be omitted, the number of semiconductor manufacturing steps and the manufacturing time can be reduced. Therefore, high processing quantization of semiconductor manufacturing can be achieved.

Further, before the step of diffusing the impurity-diffusing component (A), the P-type diffusing agent layer 2 is preferably heated and fired at 600 ° C or higher in an oxygen atmosphere. By carrying out this baking step, the polymer compound (B) containing an alcoholic hydroxyl group contained in the P-type diffusing agent layer 2 can be thermally decomposed and disappeared. Thereby, the P-type diffusing agent layer 2 can be formed as a layer made of a film of the high-concentration impurity-diffusing component (A) before the thermal diffusion of the impurity-diffusing component (A) is performed. Therefore, the thermal diffusion of the impurity diffusion component (A) in the thermal diffusion step can be smoothly performed, and the impurity diffusion layer can be formed on the first semiconductor substrate 1 and the second semiconductor substrate 3 with higher precision. Specifically, for example, in a state in which the laminate 4 of the plurality of layers is arranged in the furnace chamber 203, a firing step of about 10 to 60 minutes is performed in an oxygen atmosphere at a temperature of from 600 ° C to 800 ° C, and then, After the inside of the furnace chamber 203 is made into an N ₂ gas atmosphere as described above, thermal diffusion treatment is performed which is increased to a thermal diffusion temperature of 800 to 1000 ° C. Each step is preferably carried out continuously in the furnace chamber 203 while alternately treating the treatment temperature and the treatment environment.

<Disintegration of laminates>

After the thermal diffusion step, the second semiconductor substrate 3 is peeled off from the P-type diffusing agent layer 2. The second semiconductor substrate 3 is bonded to the P-type diffusing agent layer 2 on the surface S1 having one side of the texture structure. Therefore, the second semiconductor substrate 3 can be easily peeled off from the P-type diffusing agent layer 2. In a state in which the second semiconductor substrate 3 is peeled off, the P-type diffusing agent layer 2 is in a state of being almost completely adhered to the surface S1 on one side of the first semiconductor substrate 1. Further, an oxide film made of boron and tantalum can be formed on the second semiconductor substrate 3 by heat. Therefore, after the second semiconductor substrate 3 is peeled off from the P-type diffusing agent layer 2, the first semiconductor substrate 1 and the second semiconductor substrate 3 are washed with a peeling solution such as hydrofluoric acid. By the above steps, as shown in FIG. 1(D), the first semiconductor substrate 1 having the P-type impurity diffusion layer 5 formed by diffusing the P-type impurity diffusion component (A) on the surface S1 side is obtained. Similarly, a P-type impurity formed by diffusing a P-type impurity diffusion component (A) on the surface S1 side of one side is obtained. The second semiconductor substrate 3 of the diffusion layer 5.

In the present embodiment, after the second semiconductor substrate 3 is peeled off from the P-type diffusing agent layer 2, the first semiconductor substrate 1 and the second semiconductor substrate 3 are cleaned (peeling of the P-type diffusing agent layer 2 and the oxide film). Therefore, compared with the case where the laminated body 4 is immersed in the peeling liquid and peeled off from the P-type diffusing agent layer 2, and the first semiconductor substrate 1 and the second semiconductor substrate 3 are washed, the peeling liquid (or washing) can be completed. In terms of the area of the liquid contact, an increase in processing efficiency can be achieved. Further, since the occurrence of the outward diffusion as described above can be suppressed, unnecessary diffusion of the back surfaces of the first semiconductor substrate 1 and the second semiconductor substrate 3 is not caused. Therefore, after the P-type impurity diffusion layer 5 is formed, an additional etching process for removing the unnecessary diffusion layer is not required, so that high processing quantization can be realized.

<Formation of N-type diffuser layer>

Next, as shown in FIG. 1(E), an N-type diffusing agent composition containing an N-type impurity diffusing component (A) is applied onto the surface S2 on the other side of the first semiconductor substrate 1 to form an N-type diffusing agent layer. 6. The application of the N-type diffusing agent composition to the first semiconductor substrate 1 is carried out, for example, by a spin coating method. After the N-type diffusing agent composition is applied onto the first semiconductor substrate 1, the N-type diffusing agent layer 6 is subjected to a drying treatment. The coating amount of the N-type diffusing agent composition on the surface of the first semiconductor substrate is the same as the amount required to diffuse the impurity-diffusing component on one semiconductor substrate in the conventional method.

<Formation of laminates>

Next, as shown in FIG. 2(A), the P-type impurity diffusion layer 5 is formed on the surface S1 side of one side, and the surface S2 of the other side of the second semiconductor substrate 3 to which the N-type diffusion agent composition is not applied is formed. It is bonded to the N-type diffusing agent layer 6. Thereby, the first semiconductor substrate 1, the N-type diffusing agent layer 6, and the second semiconductor substrate 3 are laminated in this order to form the laminated body 7.

<Diffusion of N-type impurity diffusion component (A)>

Next, as shown in FIG. 2(B), the laminate 7 is placed in the diffusion furnace 200. In the diffusion furnace 200, the plurality of laminated bodies 7 are spaced apart from each other, and are arranged in a direction perpendicular to each other in the vertical direction. In this state, for example, nitrogen (N ₂ ) gas, which is an ambient gas, is supplied from the gas supply line 208 into the furnace chamber 203. Next, the laminate 7 is heated in an N ₂ gas atmosphere, and the N-type impurity diffusion component (A) is diffused on the first semiconductor substrate 1 and the second semiconductor substrate 3. The heating temperature of the laminate 7 is preferably from 800 to 1000 °C. The polymer compound (B) containing an alcoholic hydroxyl group contained in the N-type diffusing agent layer 6 is thermally decomposed and disappeared by heating by the laminate 7, and the N-type diffusing agent layer 6 becomes a high-concentration impurity-diffusing component (A). The layer formed by the film. Then, the impurity-diffusing component (A) is diffused from the N-type diffusing agent layer 6 formed of the film to the first semiconductor substrate 1 and the second semiconductor substrate 3. Therefore, an impurity diffusion layer having a smaller resistance value deviation and having a desired resistance value can be formed on the semiconductor substrates on both sides.

Further, in the present embodiment, the N-type impurity diffusing component (A) can be prevented from being released into the gas atmosphere of the furnace chamber 203 by the second semiconductor substrate 3. Thereby, high processing quantization of semiconductor manufacturing can be prevented and suppressed The spread of outbreaks. Moreover, the amount of use of the diffusing agent composition per semiconductor substrate can be reduced more than ever, and the cost of semiconductor manufacturing can be reduced. Further, since the step of applying the N-type diffusing agent composition to the second semiconductor substrate 3 can be omitted, high processing and quantization of semiconductor manufacturing can be achieved. Further, before the impurity-diffusing component (A) is diffused, the N-type diffusing agent layer 6 is preferably heated at 600 ° C or higher in an oxygen atmosphere to be fired. By performing this baking step, the impurity diffusion layer can be formed with higher precision on the first semiconductor substrate 1 and the second semiconductor substrate 3. Further, as described above, the firing step and the heat diffusion step can be continuously performed in the furnace chamber 203.

<Disintegration of laminates>

After the thermal diffusion step, the first semiconductor substrate 1 and the second semiconductor substrate 3 are peeled off from the N-type diffusing agent layer 6 and washed. When the surface S2 on the other side of the second semiconductor substrate 3 bonded to the N-type diffusing agent layer 6 does not have a texture structure, it is relatively difficult to peel off the second semiconductor substrate 3 from the N-type diffusing agent layer 6. Therefore, it is preferred to directly immerse the laminate 7 in a stripping liquid such as hydrofluoric acid. Further, when the texture structure is formed on the other surface S2, the laminate 7 may be disassembled in the same order as the disassembly of the laminate 4. According to the above procedure, as shown in FIG. 2(C), the first semiconductor substrate 1 having the N-type impurity diffusion layer 8 formed by diffusing the N-type impurity diffusion component (A) is provided on the other surface S2. In the same manner, the second semiconductor substrate 3 having the N-type impurity diffusion layer 8 formed by diffusing the N-type impurity diffusion component (A) on the surface S2 side of the other side is obtained.

<Formation of Solar Cells>

Next, as shown in FIG. 2(D), a P-type impurity diffusion layer is formed on the first semiconductor substrate 1 and the second semiconductor substrate 3 by a conventional chemical vapor deposition method (CVD method), for example, a plasma CVD method. A passivation layer 9 made of a tantalum nitride film (SiN film) is formed on the surface (the surface S1 on one side) on the side of 5. The passivation layer 9 also functions as an antireflection film.

Next, as shown in FIG. 2(E), the passivation layer 9 is selectively removed by a conventional photolithography method and etching method to form a contact hole 9a so that a specific region of the P-type impurity diffusion layer 5 is exposed. Then, a metal such as silver (Ag) is filled in the contact hole 9a by the electrolytic plating method, the electroless plating method, or the screen printing using an Ag paste, and the first semiconductor substrate 1 and the second semiconductor. A surface electrode 10 (first electrode) electrically connected to the P-type impurity diffusion layer 5 is formed on the surface S1 side on one side of the substrate 3. In order to increase the efficiency of the solar cell, the surface electrode 10 is formed into a comb pattern. Further, for example, an aluminum (Al) paste is screen-printed on the surface (the other surface S2) on the side where the N-type impurity diffusion layer 8 is formed on the first semiconductor substrate 1 and the second semiconductor substrate 3, On the surface S2 side of the other side of the first semiconductor substrate 1 and the second semiconductor substrate 3, a back surface electrode 11 (second electrode) electrically connected to the N-type impurity diffusion layer 8 is formed. The solar cell 100 of the present embodiment can be manufactured by the above steps.

As described above, the method of diffusing the impurity-diffusing component of the present embodiment is to apply the diffusing agent composition to the surface of the first semiconductor substrate 1 to form a diffusing agent layer, and then to apply the second semiconductor substrate 3 to which the diffusing agent composition is not applied. The laminate is bonded to the diffusing agent layer to form a laminate. Next, heat the layer In combination, the impurity diffusion component (A) is diffused to the first semiconductor substrate 1 and the second semiconductor substrate 3. Thereby, since the coating amount of the diffusing agent composition can be reduced more than in the related art, the cost of semiconductor manufacturing can be reduced. Further, the second semiconductor substrate 3 can suppress the diffusion of the impurity-diffusing component (A) from the first semiconductor substrate 1 into the environment, thereby suppressing the occurrence of outward diffusion. Moreover, by manufacturing a solar cell by using the diffusion method of the impurity diffusion component, it is possible to reduce the cost of solar cell manufacturing and improve the performance of the solar cell.

The present invention is not limited to the above-described embodiments, and various modifications such as design changes may be added based on the knowledge of those skilled in the art, and embodiments including such modifications are also included in the scope of the present invention. The new embodiment produced by the combination of the above embodiment and the following modifications has the individual effects of the combined embodiment and modification.

In the above embodiment, the diffusion method of the impurity diffusion component of the present embodiment is used for both the diffusion of the P-type impurity-diffusing component (A) and the diffusion of the N-type impurity-diffusing component (A), but it is also possible to The diffusion method of the present embodiment is the diffusion method of the impurity diffusion component (A) of any type. In this case, at least the diffusion of the impurity-diffusing component (A) of the one type can also reduce the amount of the diffusing agent used and suppress the outward diffusion. In the present embodiment, the P type is the first conductivity type, and the N type is the second conductivity type. However, the N type may be the first conductivity type and the P type may be the second conductivity type.

Further, in the above embodiment, the impurity diffusion layer is formed on the N-type germanium wafer, but the impurity diffusion layer may be formed on the P-type germanium wafer. Further, in the above embodiment, the diffusion furnace 200 is a vertical diffusion furnace, but may be It is a horizontal diffusion furnace known in the past.

[Examples]

The embodiments of the present invention are described below, but the examples are merely illustrative of the invention and are not intended to limit the invention.

<Modulation of P-type diffusing material composition>

According to the composition and content of the components shown in Table 1, the components were uniformly mixed, and filtered through a membrane filter of 0.45 μm to prepare a P-type diffusing agent 1 and a diffusing agent 2. The diffusing agents 1 and 2 used B ₂ O ₃ as the P-type impurity diffusing component (A). Further, in the diffusing agent 1, polyvinyl alcohol is used as the polymer compound (B) having an alcoholic hydroxyl group. The diffusing agent 2 uses a condensation product (SiO ₂ ) using tetraethoxysilane as a starting material instead of the alcohol-containing hydroxy polymer compound (B). The diffusing agent 1 used propylene glycol monomethyl ether (PGME) as an organic solvent (C) as a solvent component. The content of the impurity-diffusing component (A), the polymer compound (B) containing an alcoholic hydroxyl group, the SiO ₂ , and the solvent (wt%) shown in Table 1 are the total mass of the composition of the diffusing material, and the components of the solvent composition. The content (wt%) is the content relative to the total mass of the solvent.

<Formation of P-type diffusing agent layer>

A plurality of N-type mirror-finished wafers subjected to mirror treatment were prepared, and a diffusing agent 1 or a diffusing agent 2 was applied to one surface of a part of the wafer using a spin coater (manufactured by MIKASA Co., Ltd.). Next, the coated wafers were placed on a hot plate, and the applied diffusing agent composition was dried at 150 ° C for 3 minutes to form a P-type diffusing agent layer. The film thickness of the P-type diffusing agent layer was 2410 Å. Next, the wafer to which the diffusing agent is not applied is bonded to the P-type diffusing agent layer to form a laminate. Hereinafter, the wafer to which the diffusing agent 1 is applied is referred to as "the coated wafer of the first embodiment", and the wafer to which the diffusing agent 2 is applied is referred to as "the coated wafer of Comparative Example 1." Further, a wafer in which a diffusing agent is not applied is referred to as a "opposing wafer."

<Thermal diffusion of impurity diffusion components>

The laminate of Example 1 and the laminate of Comparative Example 1 were respectively arranged in Inside the diffusion furnace. Next, the laminates were heated at 950 ° C for 30 minutes to thermally diffuse the impurity diffusion component (A) in the P-type diffusing agent layer to form a P-type impurity diffusion layer in each wafer. Subsequently, the P-type diffusing agent layer of each laminate was removed with hydrofluoric acid.

<Measurement of resistance value>

The coated wafer and the counter wafer of Example 1 and Comparative Example 1 were measured by a four-probe method and a P-type diffusing agent layer using a sheet resistance measuring device (VR-70: manufactured by International Electric Co., Ltd.). The sheet resistance value to the bonding surface (that is, the P-type impurity diffusion layer formed on each wafer). The measurement of the sheet resistance value was performed at 25 points in a region where each of the wafers was aligned with the wafer facing the coated wafer and overlapped with the P-type diffusing agent layer. Further, the standard deviation of the obtained sheet resistance value was calculated. The results are shown in Table 2.

<P/N judgment>

With respect to the coated wafers of Example 1 and Comparative Example 1 after the thermal diffusion treatment, the P/N determining machine (PN/12α: manufactured by NAPSON Co., Ltd.) was used to determine the side opposite to the side on which the P-type diffusing agent layer was formed. The conductive type of the surface (hereinafter referred to as the "back surface" as appropriate). The results are shown in Table 2.

<Diffusion agent layer - evaluation of distance between wafers>

Since the counter wafer of the first embodiment described above is bonded to the P-type diffusing agent layer, the distance from the P-type diffusing agent layer is substantially 0 mm. Relative to Therefore, the coated wafer of the diffusing agent 1 and the counter wafer are arranged in a space in the diffusion furnace so that the distance between the P-type diffusing agent layer and the counter wafer is 2.4 mm. Thermal diffusion treatment. Hereinafter, the coated wafer and the counter wafer are referred to as the coated wafer and the counter wafer of Comparative Example 2. Next, the above-described resistance value measurement and P/N determination were performed on the coated wafer and the counter wafer of Comparative Example 2. The results are shown in Table 2.

Further, the coating wafer to which the diffusing agent 1 is applied as described above and the counter wafer are spaced apart from each other in the diffusion furnace so that the distance between the P-type diffusing agent layer and the counter wafer is 4.2 mm is performed. Thermal diffusion treatment. Hereinafter, the coated wafer and the counter wafer are referred to as the coated wafer and the counter wafer of Comparative Example 3. Next, the above-described resistance value measurement and P/N determination were performed on the coated wafer and the counter wafer of Comparative Example 3. The results are shown in Table 2.

As shown in Table 2, in Example 1, both the coated wafer and the opposite wafer showed the same sheet resistance value (Ω/sq) and standard deviation. Moreover, the conductivity type of the back surface of the coated wafer is not reversed. In contrast, in comparison In Example 1, the standard deviation of the coated wafer was large, and the sheet resistance and standard deviation of the wafer were large. In Comparative Example 2, the sheet resistance value and the standard deviation of the coated wafer and the sheet resistance value of the wafer were small, but the standard deviation of the wafer was large. Moreover, the conductivity type of the back surface of the coated wafer is reversed. In Comparative Example 3, the sheet resistance value and the standard deviation of the coated wafer were small, but the sheet resistance value of the counter wafer was larger than the standard deviation. Moreover, the back surface of the coated wafer is reversed in conductivity.

Therefore, compared with Comparative Example 1, it was confirmed that Example 1 has a good diffusibility of the impurity diffusion component (A) for both the coated wafer and the opposite wafer, and the resistance value of the two wafers can be formed. Small good impurity diffusion layer. Further, in comparison with Comparative Examples 2 and 3, it was confirmed that Example 1 has good diffusibility of the impurity diffusion component (A) for the opposite wafer, and good impurity diffusion which is small in resistance to the opposite wafer can be formed. Floor. Further, according to Example 1, it was confirmed that the outward diffusion can be suppressed.

<Evaluation of coating amount>

The coated wafer to which the diffusing agent 1 is applied as described above is placed in a diffusion furnace, and the above-described thermal diffusion treatment is performed without providing a counter wafer. Hereinafter, the coated wafer was referred to as a coated wafer of Comparative Example 4. Next, the above-described resistance value measurement was performed on the coated wafer of Comparative Example 4, and the measurement results of the coated wafer and the counter wafer of Example 1 were compared. The results are shown in Table 3.

As shown in Table 3, the coated wafer and the counter wafer of Example 1 showed sheet resistance values and standard deviations which were as small as Comparative Example 4. Therefore, it was confirmed that the impurity diffusion layer can be formed on twice the wafer in the conventional method in which the diffusion agent layer is exposed in a state in which the diffusion agent layer is exposed by thermal diffusion treatment.

<Evaluation of wafers for solar cells> <Modulation of P-type diffusing material composition>

According to the composition and content of the components shown in Table 4, the components were uniformly mixed, and filtered through a membrane filter of 0.45 μm to prepare a P-type diffusing agent 3 and a diffusing agent 4.

<Formation of P-type diffusing agent layer>

A plurality of N-type solar cell wafers having a textured structure on the surface thereof were prepared, and a diffusing agent 3 or a diffusing agent 4 was applied to one surface of a part of the wafer using a spin coater (manufactured by MIKASA Co., Ltd.). Next, the coated wafers were placed on a hot plate, and the applied diffusing agent composition was dried at 150 ° C for 3 minutes to form a P-type diffusing agent layer. The film thickness of the P-type diffusing agent layer was 2410 Å. Next, the counter wafer is bonded to the P-type diffusing agent layer to form a laminate. Hereinafter, the wafer to which the diffusing agent 3 is applied is appropriately referred to as "the coated wafer of the second embodiment", and the wafer to which the diffusing agent 4 is applied is referred to as "the coated wafer of the third embodiment".

<Thermal diffusion of impurity diffusion components>

The laminates of Examples 2 and 3 were each placed in a diffusion furnace, and a P-type impurity diffusion layer was formed in each wafer by the above method. Subsequently, the P-type diffusing agent layer of each laminate was removed with hydrofluoric acid.

<Measurement of resistance value>

With respect to the coated wafer and the counter wafer of Examples 2 and 3, the sheet resistance value on the opposite surface to the P-type diffusing agent layer was measured by the above method, and the standard deviation of the sheet resistance value was calculated. The results are shown in Table 5.

<P/N judgment>

For the coated wafers of Examples 2 and 3 after the thermal diffusion treatment, the conductivity type of the back surface was determined by the above method. The results are shown in Table 5.

As shown in Table 5, in Examples 2 and 3, both the coated wafer and the counter wafer showed the same sheet resistance value and standard deviation. Therefore, even a wafer with a textured structure for solar cells is confirmed. A good impurity diffusion layer having a small resistance value deviation can be formed for both the coated wafer and the opposite wafer. Moreover, it was confirmed that the outward diffusion can be suppressed.

For example, embodiments of the following combinations are also included in the scope of the present invention.

(Item 1)

A method for diffusing an impurity-diffusing component, comprising the steps of: applying a diffusing agent composition of the following composition to a surface of one side of a first semiconductor substrate to form a diffusing agent layer; a step of bonding a surface of one side of the second semiconductor substrate of the diffusing agent composition to the diffusing agent layer to form a laminate; and heating the laminate to diffuse the following impurity-diffusing component (A) to the first semiconductor a step of the substrate and the second semiconductor substrate; the diffusing agent composition includes an impurity-diffusing component (A), and an alcohol-containing hydroxyl group-containing polymer which is thermally decomposed and disappeared by heating at 600 ° C for 30 minutes in an oxygen atmosphere. Compound (B) and organic solvent (C).

(Project 2)

In the method of diffusing an impurity diffusion component according to the item 1, the first semiconductor substrate and the second semiconductor substrate are substrates for a solar cell having a textured structure on the surface of the one side.

(Item 3)

The method for diffusing an impurity diffusion component according to the above item 1 or 2, further comprising the steps of: separating the second semiconductor substrate from the diffusion agent layer; and separating the diffusion agent from the first semiconductor substrate using a stripping solution The steps of the layer.

(Item 4)

The method for diffusing an impurity diffusion component according to any one of items 1 to 3, wherein, in the method of thermally diffusing the impurity diffusion component in a state where the diffusion agent layer is exposed, the impurity diffusion component is diffused on the semiconductor substrate for one piece. The required amount of the diffusing agent composition is applied to the surface of the first side of the first semiconductor substrate.

(Item 5)

The method for diffusing an impurity diffusion component according to any one of items 1 to 4, wherein the heating temperature of the laminate in the step of diffusing the impurity diffusion component (A) is 800 to 1000 °C.

(Item 6)

The method for diffusing an impurity-diffusing component according to any one of items 1 to 5, further comprising the step of heating the above-mentioned diffusing agent layer at 600 ° C or higher and firing the mixture before the step of diffusing the impurity-diffusing component (A).

(Project 7)

A method for producing a solar cell, comprising the step of diffusing an impurity diffusion component (A) of a first conductivity type onto a semiconductor substrate by using a diffusion method of an impurity diffusion component according to any one of items 1 to 6 a step of forming a first conductivity type impurity diffusion layer on a surface of one side of the semiconductor substrate, and diffusing the second conductivity type impurity diffusion component (A) on the other surface of the semiconductor substrate, a step of forming the second conductivity type impurity diffusion layer on the other surface of the semiconductor substrate, and providing a first electrode on the surface side of the semiconductor substrate, and the first electrode and the first conductivity type impurity The step of electrically connecting the diffusion layer and the step of providing a second electrode on the surface side of the other side of the semiconductor substrate and electrically connecting the second electrode to the impurity diffusion layer of the second conductivity type.

Claims (6)

A method for diffusing an impurity diffusion component, the method comprising the steps of: applying a diffusing agent composition of the following composition to a surface of one side of a first semiconductor substrate to form a diffusing agent layer, and uncoating a step of bonding a surface of one side of the second semiconductor substrate of the diffusing agent composition to the diffusing agent layer to form a laminate; and heating the laminate to diffuse the impurity diffusion component (A) described below a step of separating the semiconductor substrate and the second semiconductor substrate; a step of peeling off the second semiconductor substrate from the diffusing agent layer; and a step of separating the diffusing agent layer from the first semiconductor substrate using a stripping liquid; and the diffusing agent composition includes The impurity-diffusing component (A) and the polymer compound (B) having an alcoholic hydroxyl group which is thermally decomposed and disappeared by heating at 600 ° C for 30 minutes in an oxygen atmosphere, and an organic solvent (C). The method of diffusing an impurity diffusion component according to claim 1, wherein the first semiconductor substrate and the second semiconductor substrate are substrates for a solar cell having a texture structure on a surface of the one side. A method for diffusing an impurity diffusion component according to claim 1, wherein in the method of thermally diffusing the impurity diffusion component in a state in which the diffusion agent layer is exposed, the diffusion diffusion component is diffused in the amount of the diffusion agent required for diffusion on a semiconductor substrate The composition is applied to the aforementioned side of the first semiconductor substrate On the surface. The method for diffusing an impurity diffusion component according to claim 1, wherein the heating temperature of the laminate in the step of diffusing the impurity diffusion component (A) is 800 to 1000 °C. The method for diffusing an impurity diffusion component according to claim 1, further comprising the step of heating the diffusion agent layer at 600 ° C or higher and firing the mixture before the step of diffusing the impurity diffusion component (A). A method of manufacturing a solar cell, comprising the steps of: diffusing an impurity diffusion component (A) of a first conductivity type onto a semiconductor substrate by using a diffusion method of an impurity diffusion component according to claim 1, on one of the semiconductor substrates a step of forming an impurity diffusion layer of the first conductivity type on the surface of the side, and diffusing the impurity diffusion component (A) of the second conductivity type on the other surface of the semiconductor substrate, on the other side of the semiconductor substrate a step of forming the second conductivity type impurity diffusion layer on the surface, and providing a first electrode on the surface side of the semiconductor substrate and electrically connecting the first electrode and the first conductivity type impurity diffusion layer And providing a second electrode on a surface side of the other side of the semiconductor substrate, and electrically connecting the second electrode to the impurity diffusion layer of the second conductivity type.