JP2011119341A - Method of forming diffusion-preventive mask, and method of manufacturing solar cell using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a diffusion-preventive mask that can reduce manufacturing costs while suppressing generation of diffusion unevenness, and to provide a method of manufacturing a solar cell using the same. <P>SOLUTION: The method of forming the diffusion-preventive mask includes a process of forming a mask layer 2 to serve as the diffusion-preventive mask by coating a substrate 1 with mask ink containing a silicon compound by using an ink jet method and a process of baking the substrate 1 including the mask layer 2. A thickness of the mask layer 2 in a first region 5b is larger than a mask-property securing minimum film thickness which is a minimum film thickness needed for the mask layer 2 to function as a dopant diffusion preventive mask, and a thickness of the mask layer 2 in a second region 5b is smaller than a crack resistance film thickness which is a maximum film thickness at which the mask layer 2 does not crack in a state of diffusion temperature of a dopant, the mask layer 2 being formed thicker in the second region 5a than in the first region 5b. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for forming a diffusion prevention mask and a method for manufacturing a solar cell using the same.

  As a method for forming a pn junction on a substrate, a doping technique for diffusing a p-type material or an n-type material into the substrate is widely applied to the semiconductor field including the solar cell field. In addition, in order to form the doped regions of the p-type material and the n-type material in a predetermined pattern, development of a diffusion prevention mask for preventing the material from diffusing into a region that does not require doping is in progress. .

  Patent Document 1 is a prior art document disclosing a solar cell in which a doped region is formed in a pattern. The solar cell described in Patent Document 1 is a back electrode type solar cell in which no electrode is formed on the light receiving surface and an n-type electrode and a p-type electrode are formed only on the back surface. In a back electrode type solar cell, n-type and p-type doped regions are formed in a pattern on a semiconductor substrate on the back side of the solar cell.

  FIG. 6 is a cross-sectional view schematically showing an example of the back electrode type solar cell. In FIG. 6, the side indicated by the arrow is the back surface. As shown in FIG. 6, p-type diffusion layers 24 and n-type diffusion layers 25 are alternately formed in the back surface side of a silicon substrate 21 that is a semiconductor substrate. A passivation film 28 is formed on the upper surface on the back surface side of the silicon substrate 21, thereby suppressing carrier recombination.

  Contact holes are formed in the passivation film 28 above the p-type diffusion layer 24 and above the n-type diffusion layer 25. A back electrode is formed on the top surface of the passivation film 28 and inside the contact hole. The back electrode includes a p-type electrode 30 electrically connected to the p-type diffusion layer 24 and an n-type electrode 31 electrically connected to the n-type diffusion layer 25.

  The diffusion prevention mask is used when the p-type diffusion layer 24 and the n-type diffusion layer 25 are formed. The diffusion prevention mask layer is formed in a region that is not diffused in advance so that the material does not diffuse into an unnecessary region. Is responsible.

  Conventionally, the diffusion prevention mask layer has been formed by photolithography. For example, when forming an n-type diffusion layer, a silicon oxide film is first formed on the entire back surface of the silicon substrate 21. A silicon nitride film is formed as a passivation film 28 on the upper surface of the silicon oxide film. Thereafter, exposure, development, and etching are sequentially performed, and a portion of the passivation film 28 corresponding to the portion where the n-type diffusion layer 25 is formed is removed. Finally, an n-type diffusion layer 25 is formed by diffusing a gas containing an n-type dopant such as phosphorus on the silicon substrate 21 exposed through the removed portion.

  However, in the above manufacturing method, since the manufacturing cost is high, an inexpensive patterning method has been demanded from the viewpoint of cost reduction.

Other patterning methods generally include various solution processes such as an inkjet method and a printing method. Patent Document 2 is a prior art document that discloses a method for manufacturing a solar cell using a solution process. In the manufacturing method of the solar cell described in Patent Document 2, a mask is formed by screen printing or application by a dispenser nozzle. As the mask solution, SiO ₂ sol-gel paste is used.

  Patent Document 3 is a prior art document disclosing a method for manufacturing a solar cell element using an ink jet method. In the method for manufacturing a solar cell element described in Patent Document 3, a dopant layer is formed after an annular mask layer is formed using an inkjet method.

JP 2003-298078 A JP 11-97726 A JP 2003-338632 A

  In the manufacturing method of the solar cell described in Patent Document 2, masking is performed by screen printing or application by a dispenser nozzle. However, in screen printing, a printing pattern is fixed by a screen plate. Therefore, it is necessary to form a screen plate in accordance with the pattern shape, resulting in an increase in manufacturing cost.

  In application by a dispenser nozzle, since the width of the mask pattern is determined by the nozzle width, the width of the mask pattern cannot be changed, and the mask solution may be applied to unnecessary areas.

  Each of the above methods is a pattern forming method using a relatively high viscosity ink, but it is difficult to form a thin mask layer using a high viscosity mask solution. In addition, when the thickness of the formed mask layer is large, the degradation of the solar cell characteristics due to the generation of cracks in the mask during firing, the longer removal of the mask layer by etching, and the production cost due to the decrease in yield Problems such as increase occur.

  In the method using the ink jet method described in Patent Document 3, the above-described problems can be solved, but the mask shape to be formed is not considered. Depending on the mask shape, the n-type diffusion layer and the p-type diffusion layer cannot be formed in a desired region.

  FIG. 7A is a cross-sectional view schematically showing a state in which a diffusion prevention mask is formed on a substrate by a conventional ink jet method, and FIG. 7B is a cross-sectional view schematically showing a state in which a diffusion layer is formed. It is. As shown in FIG. 7A, a mask layer 42 is formed on the upper surface of the silicon substrate 41. In this state, the dopant 43 is diffused in the gas phase. When the conventional ink jet method is used to form a mask layer 42 having a uniform film thickness, as shown in FIG. 7A, the central portion is formed with a certain thickness or more, and the end portion Is formed to be smaller than the film thickness of the central portion.

  Generally, a diffusion prevention mask can exhibit diffusion prevention performance by having a film thickness of a certain level or more. As shown in FIG. 7B, since the end portion 45 of the mask layer 42 is thin, the dopant is likely to wrap around the lower portion of the mask layer 42, and the diffusion preventing performance is low. Therefore, uneven diffusion occurs in the end portion 45 of the mask layer 42 in each of the film thickness direction and the substrate horizontal direction, so that the diffusion layer cannot be formed only in a desired region. As a result, some p-type diffusion layers and n-type diffusion layers are short-circuited, so that the characteristics of the solar cell are deteriorated.

  The present invention has been made in view of the above problems, and by simply forming a diffusion prevention mask having a thickness of a certain thickness or more as a whole, while suppressing the occurrence of uneven diffusion, An object of the present invention is to provide a method for forming a diffusion prevention mask and a method for manufacturing a solar cell using the same, which can reduce the manufacturing cost.

  The method for forming a diffusion preventing mask according to the present invention is a method for forming a dopant diffusion preventing mask on a substrate. The diffusion prevention mask is formed by applying a mask ink containing a silicon compound on a substrate by using an inkjet method to form a mask layer serving as a diffusion prevention mask, and firing the substrate containing the mask layer. Process. The mask layer after firing includes a first region located in the central portion and a second region located in the end portion surrounding the first region as viewed in a plan view. The thickness of the mask layer in the first region is larger than the minimum masking ensuring minimum film thickness that is the minimum film thickness necessary for the mask layer to function as a dopant diffusion preventing mask, and the thickness of the mask layer in the second region is The mask layer is formed to be smaller than the crack-resistant film thickness, which is the maximum film thickness at which cracks do not occur in the dopant diffusion temperature state, and to be thicker than the first region in the second region.

  In the above diffusion prevention mask forming method, the mask is formed so as to be thinner than the crack-resistant film thickness in the second region, thicker than the minimum masking ensuring film thickness in the first region, and thicker than the first region in the second region. By forming the layer, it is possible to form a diffusion prevention mask having a thickness of a certain thickness or more as a whole. Thereby, the performance of the diffusion preventing mask is improved, and the occurrence of uneven diffusion can be suppressed. In addition, the manufacturing cost can be reduced by simply forming a diffusion prevention mask using an inkjet method.

  Preferably, the mask ink contains at least two kinds of solvents having different boiling points. In this case, when the substrate is baked, the low boiling point solvent is volatilized first to increase the viscosity of the film and maintain the desired film shape while volatilizing the high boiling point solvent. A mask having a desired shape can be formed.

Preferably, the mask ink has the general formula R ¹⁴ _-n Si (OR ² ) _n (wherein R ¹ and R ² are any hydrocarbon group or aromatic hydrocarbon group having 1 to 10 carbon atoms). , N is an integer of any one of 2 to 4), a siloxane compound obtained by hydrolytic polymerization of one or more alkoxysilanes, a first solvent having a boiling point of 150 ° C. or lower, and the first solvent And a second solvent having a high boiling point and viscosity. The viscosity of the mask ink is 1 mPa · s or more and 30 mPa · s or less.

  In this case, when the mask layer is formed using the ink jet method, the mask ink has an appropriate viscosity, so that the mask ink can be discharged with high accuracy. Further, when the mask ink contains the above-described silicon compound, the durability of the mask layer at a high temperature can be improved, and it can be easily removed when the mask layer is removed.

  Preferably, the first solvent has a boiling point of 150 ° C. or less and a viscosity of 30 mPa · s or less, and the second solvent has a boiling point of 150 ° C. or more and 250 ° C. or less and a viscosity of 30 mPa · s or more. In this case, the film thickness of the mask layer in the first region and the second region is adjusted to a range in which cracks can be prevented from occurring in the mask during firing while maintaining the mask diffusion preventing performance. be able to.

  Preferably, the ratio of the siloxane compound in the mask ink is 10 wt% or more and 25 wt% or less, and the ratio of the first solvent is 5 wt% or more and 25 wt% or less. In this case, the film thickness of the mask layer in the first region and the second region is adjusted to a range in which cracks can be prevented from occurring in the mask during firing while maintaining the mask diffusion preventing performance. be able to.

  Preferably, the mask ink is a siloxane compound obtained by hydrolyzing tetraethoxysilane, the thickness of the mask layer in the first region is 0.4 μm or more, and the thickness of the mask layer in the second region is 1 0.0 μm or less. In this case, it is possible to form a diffusion preventing mask having a thickness necessary for preventing the diffusion of the dopant throughout. Further, by preventing the diffusion prevention mask from becoming too thick, it is possible to prevent cracks from being generated in the mask layer during firing, and to suppress an increase in the time required to remove the diffusion prevention mask.

  Preferably, in the step of forming the mask layer, the substrate is heated to 40 ° C. or higher and 80 ° C. or lower. In this case, the mask layer can be formed such that the end face of the mask layer rises rapidly from the upper surface of the substrate. As a result, the formation accuracy of the diffusion region can be improved.

  Preferably, in the step of forming the mask layer, the mask ink is applied in a plurality of times with a time for drying the applied mask ink being interposed. In this case, when adjacent masks are close to each other, it is possible to prevent the masks from affecting each other and being unable to be formed into a desired shape. Specifically, a mask layer separated so as not to have an influence is formed, and after the mask layer is dried, another mask layer close to the mask layer is formed. As a result, each mask layer can be accurately formed in a desired shape.

  The manufacturing method of the solar cell based on this invention includes the process of forming a diffusion prevention mask in the partial area | region of a substrate surface at least using the formation method of the diffusion prevention mask in any one of said. In the above solar cell manufacturing method, since a desired diffusion region can be formed on the substrate with high accuracy, the characteristics of the solar cell can be improved.

  The manufacturing method of the solar cell based on this invention is a manufacturing method of the solar cell using the diffusion prevention mask formed on the board | substrate. In the method of manufacturing a solar cell, a step of forming a first diffusion prevention mask using one of the above-described diffusion prevention mask formation methods and a first diffusion prevention mask are formed in one region of a substrate surface. A step of forming an n-type diffusion layer by diffusing an n-type dopant on a portion of the substrate surface that is not formed and a step of removing the first diffusion prevention mask are provided. In addition, a method for manufacturing a solar cell includes a step of forming a second diffusion prevention mask on another region of the substrate surface using the diffusion prevention mask forming method described above, and a second diffusion prevention mask. The method includes a step of forming a p-type diffusion layer by diffusing a p-type dopant on a portion of the substrate surface that is not formed, and a step of removing the second diffusion prevention mask. Furthermore, a method for manufacturing a solar cell includes a step of forming a passivation film provided with a contact hole on a surface of a substrate on which an n-type diffusion layer and a p-type diffusion layer are formed, and an upper portion of the passivation film and in the contact hole. Forming a back electrode composed of an n-type electrode electrically connected to the n-type diffusion layer and a p-type electrode electrically connected to the p-type diffusion layer.

  In the above solar cell manufacturing method, the n-type diffusion layer and the p-type diffusion layer can be accurately formed in a desired pattern, so that the characteristics of the solar cell can be improved. In addition, since the diffusion prevention mask is formed using the inkjet method, the manufacturing cost of the solar cell can be reduced.

  By forming the mask layer so as to be thinner than the crack-resistant film thickness in the second region, thicker than the minimum mask property ensuring film thickness in the first region, and thicker than the first region in the second region, the entire region is constant. A diffusion prevention mask having a thickness equal to or greater than the thickness can be formed. Thereby, the performance of the diffusion preventing mask is improved, and the occurrence of uneven diffusion can be suppressed. In addition, the manufacturing cost can be reduced by simply forming a diffusion prevention mask using an inkjet method.

(A) is sectional drawing which shows typically the board | substrate with which the diffusion prevention mask was formed by the formation method of the diffusion prevention mask which concerns on one Embodiment of this invention, (B) formed the diffusion layer in the board | substrate. It is sectional drawing which shows a state typically, (C) is sectional drawing which expands and shows a part of board | substrate with which the diffusion prevention mask was formed. (A) is a cross-sectional view schematically showing a state immediately after the mask ink is applied on the substrate, and (B) is a cross-sectional view schematically showing a state in which the first solvent is volatilized. C) is a cross-sectional view schematically showing a state in which the second solvent is volatilized. It is sectional drawing for demonstrating the manufacturing method of the solar cell which concerns on the same embodiment. It is a figure which shows the result of having measured the shape of the mask layer formed in Example 1. FIG. In FIG. 4, it is a figure which expands and shows the part located in the edge part of a mask layer. It is sectional drawing which shows an example of a back electrode type solar cell typically. (A) is sectional drawing which shows typically the state which formed the diffusion prevention mask on the board | substrate by the conventional inkjet method, (B) is sectional drawing which shows typically the state which formed the diffusion layer. .

  Hereinafter, a method for forming a diffusion prevention mask according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1A is a cross-sectional view schematically showing a substrate on which a diffusion prevention mask is formed by a diffusion prevention mask forming method according to an embodiment of the present invention, and FIG. It is sectional drawing which shows typically the formed state, (C) is sectional drawing which expands and shows a part of board | substrate with which the diffusion prevention mask was formed.

  As shown in FIG. 1A, a diffusion prevention mask forming method according to an embodiment of the present invention is a method of forming a diffusion prevention mask on a silicon substrate 1. The mask layer 2 serving as a diffusion prevention mask is formed by applying a mask ink containing a silicon compound on the substrate 1 using an ink jet method. A diffusion preventing mask is formed by baking the substrate 1 including the mask layer 2. A diffusion layer is formed by vapor-phase diffusing the dopant 3 on the substrate 1 in this state.

  As shown in FIG. 1B, the mask layer 2 after firing has a first region 5b located in the central portion and a second portion located in the end portion surrounding the first region 5b in plan view. Region 5a is included. In the present embodiment, when the total width of the mask layer 2 is L, the portion from the end face of the mask layer 2 to a portion located inside the mask layer 2 by 0.1 L is defined as the second region 5a. In the mask layer 2, a portion other than the second region 5a is the first region 5b.

As shown in FIG. 1C, the mask layer 2 is formed in the second region 5a so as to be thicker than the first region 5b. Here, the most thickness T ₁ is the thickness of the thin portion, the most thickness of the film thickness of the thick portion as T ₂ in the second region 5a in the first region 5b.

As shown in FIGS. 1B and 1C, the mask layer 2 is formed in the second region 5a so as to be thicker than the first region 5b, so that the entire thickness has a certain thickness or more. A diffusion prevention mask can be formed. Further, T ₁ was set larger than the minimum masking ensuring film thickness, and T ₂ was made smaller than the crack resistant film thickness. Here, the minimum film thickness ensuring masking property is the minimum film thickness necessary for the formed film to function as a mask for dopant diffusion. The crack-resistant film thickness is the maximum film thickness at which cracks do not occur when the formed film is at the diffusion temperature.

  The minimum mask property ensuring film thickness and the crack resistant film thickness are determined by the composition of the ink material or the rigidity of the film after formation. In the present embodiment, the minimum film thickness ensuring maskability is about 0.4 μm. The crack-resistant film thickness is about 2 μm. When tetraethoxysilane (TEOS) is used as a raw material for the mask ink, the denseness of the film tends to be high, and the crack resistance film thickness is about 1.0 μm.

  When the dopant 3 is vapor-phase diffused on the substrate 1 on which such a diffusion prevention mask is formed, diffusion unevenness occurs in the film thickness direction and the substrate horizontal direction due to the dopant 3 wrapping around the diffusion prevention mask. This can be suppressed. As a result, for example, the n-type diffusion layer 4 can be formed only in a desired region. That is, the region of the diffusion layer can be matched with the mask accuracy, and the end of the diffusion layer can be formed as designed.

  In order to obtain a diffusion prevention mask having the above-described film shape, in this embodiment, the mask ink used for mask formation contains at least two kinds of solvents having different boiling points. Specifically, the mask ink used was composed of a solid content containing at least a silicon compound, a first solvent having a low boiling point and a low viscosity, and a second solvent having a high boiling point and a high viscosity. In the process of volatilization of the first solvent from the low viscosity of the mask layer immediately after inkjet printing, the film is formed so that the film thickness at the edge of the film is larger than the film thickness at the center of the film, and then the shape The diffusion preventing mask of the present invention can be formed by volatilizing the second solvent while maintaining the above.

  2A is a cross-sectional view schematically showing a state immediately after the mask ink is applied on the substrate, and FIG. 2B is a cross-sectional view schematically showing a state in which the first solvent is volatilized. (C) is a cross-sectional view schematically showing a state in which the second solvent is volatilized.

  As shown in FIG. 2A, the mask layer 2a immediately after being applied to the upper surface of the substrate 1 using the ink jet method has a convex lens shape. Since the mask layer 2a contains the first solvent, the mask layer 2a has a low viscosity and high fluidity, and as indicated by an arrow 11, a flow occurs from the center to the end of the mask layer 2a. At this time, the first solvent 12 is volatilized from the surface of the mask layer 2a.

  Therefore, in the mask layer 2a, due to the fluidity, solute movement to the end of the mask layer 2a occurs, the thickness of the end increases, and the viscosity rapidly increases as the first solvent volatilizes. .

  As shown in FIG. 2B, the mask layer 2b in which the first solvent 12 has volatilized is in a state where the viscosity is very high and the fluidity of the solute is hardly present. By volatilizing the second solvent 13 from the mask layer 2b, the viscosity of the mask layer 2b is further increased while maintaining its shape.

  As shown in FIG. 2C, the dried mask layer 2c from which the second solvent 13 has volatilized is thicker than the first region 5b in the second region 5a, as shown in FIGS. 1B and 1C. Formed as follows.

Hereinafter, the mask ink will be described in detail.
The mask ink preferably has a viscosity of 1 mPa · s or more and 30 mPa · s or less in order to form a diffusion prevention mask using an inkjet method. The mask ink preferably has a surface tension of 20 mN / m or more and 35 mN / m or less.

  When the viscosity of the mask ink is less than 1 mPa · s, the mask ink cannot be stably ejected from the inkjet head because the viscosity of the mask ink is low. Specifically, the mask ink droplets ejected from the inkjet head are not ejected perpendicularly to the nozzle surface, but are split into a large number of minute droplets and spread easily to be splashed. is there.

  As a result, when the viscosity of the mask ink is less than 1 mPa · s, it becomes difficult to control the position where the mask ink droplets adhere to the substrate 1, and the mask ink is originally applied to the area where the mask ink is to be applied. There are cases where it is impossible. When this phenomenon occurs in the formation process of the solar cell, the reverse current increases due to a mask defect, and the characteristics of the solar cell deteriorate. On the other hand, droplets of the mask ink may adhere to areas where the mask ink should not be applied. When this phenomenon occurs in the process of forming the solar cell, the formation of the diffusion layer is hindered and the power generation efficiency of the solar cell is reduced.

  When the viscosity of the mask ink exceeds 30 mPa · s, the viscosity of the mask ink is high, so that nozzle clogging of the inkjet head is likely to occur. Due to the occurrence of nozzles that do not eject mask ink droplets, there are cases where mask ink cannot be applied to the area where mask ink is to be applied. When this phenomenon occurs in the formation process of the solar cell, the reverse current increases due to a mask defect, and the characteristics of the solar cell deteriorate.

  The mask ink preferably has a solute weight ratio of 10 wt% or more and 25 wt% or less, and a weight ratio of the first solvent 12 of 5 wt% or more and 25 wt% or less. It is preferable that the viscosity of the first solvent 12 is 30 mPa · s or less, the viscosity of the second solvent 13 is 30 mPa · s or more, and the boiling point of the second solvent 13 is 150 ° C. or more and 250 ° C. or less.

  When the weight ratio of the first solvent 12 is 5% by weight or less, since the amount of increase in the viscosity of the mask ink when the first solvent 12 is completely volatilized is small, solute movement continues. Therefore, the difference in film thickness between the end portion and the central portion of the mask layer 2a becomes too large. As a result, it becomes difficult to reduce the crack-resistant film thickness at the end of the mask layer 2a while ensuring the minimum film thickness ensuring maskability at the center of the mask layer 2a.

  When the weight ratio of the first solvent 12 is 25% by weight or more, the viscosity of the mask ink increases rapidly when the first solvent 12 is volatilized. Therefore, since solute movement hardly occurs, the film thickness at the end of the mask layer 2a does not become thicker than the film thickness at the center. In addition, since part of the mask ink volatilizes in the vicinity of the ink jet head, nozzle clogging of the ink jet head is likely to occur, and it becomes difficult to stably discharge the mask ink.

  When the boiling point of the first solvent 12 is set to 150 ° C. or more, it takes time for the first solvent 12 to volatilize. Therefore, the difference in film thickness between the end portion and the central portion of the mask layer 2a is large due to the solute flow occurring during this time. Thus, it becomes difficult to simultaneously achieve the above conditions for ensuring the mask property minimum film thickness and crack resistance film thickness.

  When the boiling point of the second solvent 13 is 250 ° C. or higher, the time from the volatilization of the first solvent 12 to the volatilization of the second solvent 13 becomes very long. The difference in film thickness between the end portion and the central portion becomes large, and it becomes difficult to simultaneously achieve the above-described conditions for ensuring the mask property minimum film thickness and crack resistance film thickness.

  When the viscosity of the second solvent 13 is 30 mPa · s or less, the viscosity of the mask ink when the first solvent 12 volatilizes is small and the fluidity of the mask ink is maintained. Therefore, it becomes difficult to achieve the above conditions for ensuring the minimum masking film thickness and the crack-resistant film thickness at the same time. The reason why the viscosity of the first solvent 12 is set to 30 mPa · s or less is to make the viscosity of the mask ink formed by blending from 1 mPa · s to 30 mPa · s.

  When the weight ratio of the solute is 10% by weight or less, the film thickness of the mask layer 2c after baking is small, and in particular, the film thickness at the center of the mask layer 2c is less than the minimum film thickness ensuring the mask performance. For this reason, when the dopant is diffused in the subsequent steps, the dopant is diffused even in a portion where the dopant does not need to be diffused, and the mask performance cannot be exhibited.

  When the weight ratio of the solute is 25% by weight or more, the film thickness of the mask layer 2c after drying is too large. In particular, the film thickness at the end of the mask layer 2c is equal to or greater than the crack resistance film thickness. Cracks occur. When the solute weight ratio is 25% by weight or more, the stability of the mask ink is low, and the viscosity of the mask ink changes with time and the solute is precipitated during storage.

  The first solvent 12 has a boiling point of 150 ° C. or less, high volatility, and low viscosity. For example, methanol, ethanol, IPA (isopropyl alcohol), propylene glycol propyl ether, propylene glycol n-methyl ether, propylene glycol n -Methyl ether acetate and propyl acetate can be used.

  The second solvent 13 is not particularly limited as long as it has a boiling point of 150 ° C. or higher and 250 ° C. or lower and has a viscosity of the first solvent 12 or higher, and is an aliphatic or aromatic hydrocarbon solvent, unit price or Solvents such as polyhydric alcohol solvents, ketone solvents, ether solvents, ester solvents, and sulfur-containing solvents can be used.

  A silicon compound was used as the solute of the mask ink. By using the silicon compound, it is possible to improve the durability of the mask layer 2c at a high temperature and the ease of removing the mask layer 2c after the diffusion of the dopant and the like.

Specifically, a siloxane compound obtained by hydrolytic polymerization of one or more types of alkoxysilanes represented by the general formula R ¹⁴ _-n Si (OR ² ) _n was used as the silicon compound. Alternatively, a compound containing a silanol group may be used.

In said alkoxysilane, a C1-C10 organic group is mentioned as a monovalent organic group of R < ¹ > in the said general formula. Examples of the organic group include an alkyl group such as a methyl group, an ethyl group, and a propyl group, an alkenyl group such as a vinyl group, an allyl group, and a propenyl group, an aryl group such as a phenyl group and a tolyl group, a benzyl group, and a phenylethyl group. And groups substituted with an aralkyl group such as, an epoxy-containing group such as a glycidyl group or a glycidyloxy group, or an amino-containing group such as an amino group or an alkylamino group.

Examples of the alkoxy group represented by OR ² in the above general formula include alkoxy groups such as methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, sec-butoxy group, t-butoxy group, vinyloxy group, 2- Examples thereof include alkenoxy groups such as propenoxy group, acyloxy groups such as phenoxy group and acetoxy group, oxime groups such as butanoxime group, and amino groups. Among these, an alkoxy group having 1 to 5 carbon atoms is preferable, and a methoxy group, an ethoxy group, an isopropoxy group, and a butoxy group are particularly preferable because of easy control during hydrolysis and condensation.

  From the viewpoint of polymerizing the siloxane compound, n in the above general formula is preferably an integer of 2 to 4. Specific examples of such compounds include, for example, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraiso-propoxysilane, tetraphenoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltri-n. -Propoxysilane, methyltri-iso-propoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, Examples include diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane.

  The compound represented by the above general formula is hydrolyzed and partially condensed by mixing with water and a catalyst in an organic solvent to form a siloxane polymer. As this organic solvent, an organic solvent described later can be used. Moreover, as a catalyst, an organic acid, an inorganic acid, an organic base, an inorganic base, etc. can be used.

  Examples of organic acids include acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oxalic acid, maleic acid, methylmalonic acid, adipic acid, sebacic acid, gallic acid Acid, butyric acid, meritic acid, arachidonic acid, mikimic acid, 2-ethylhexanoic acid, oleic acid, stearic acid, linoleic acid, linolenic acid, salicylic acid, benzoic acid, p-aminobenzoic acid, p-toluenesulfonic acid, benzenesulfone Acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, trifluoroacetic acid, formic acid, malonic acid, sulfonic acid, phthalic acid, fumaric acid, citric acid, tartaric acid and the like can be used.

  Examples of inorganic acids that can be used include hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, and phosphoric acid. As the organic base, for example, amine compounds such as methanolamine and ethanolamine can be used. As the inorganic base, for example, ammonia, sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide and the like can be used.

  Further, a surfactant may be added to the mask ink in order to improve the coating property of the mask ink. As this surfactant, for example, nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used. Furthermore, a silicone-based surfactant, a polyalkylene oxide-based surfactant, a poly (meth) acrylate-based surfactant, or the like may be added.

  As a method for preparing the mask ink, for example, first, alkoxysilane is added to a solution containing water, a catalyst, and a solvent such as alcohol capable of dissolving alkoxysilane, and stirred. After proceeding with hydrolysis in this way, the amount of alcohol and water present by hydrolysis are adjusted as necessary, and then the first solvent 12 and the second solvent 13 are added to the solution. Then, stir well.

  Here, the amount of the catalyst to be added is adjusted so that, for example, the concentration in the reaction solution of the hydrolysis reaction is 1 ppm or more and 1000 ppm or less. The amount of water added is 1.5 mol or more and 4.0 mol or less per mol of the hydrolysis group in the whole compound represented by the above general formula in consideration of the progress of hydrolysis and the progress of the subsequent polymerization reaction. It is preferable that

  The reaction conditions for the hydrolysis are not particularly limited, but the reaction temperature is preferably 0 ° C. or higher and 80 ° C. or lower, more preferably 5 ° C. or higher and 60 ° C. or lower. The reaction time is 0.1 hours or more and 24 hours or less. As a method for adjusting the amount of alcohol and water present by hydrolysis, for example, distillation under reduced pressure at a temperature of 20 ° C. or more and 100 ° C. or less.

  The diffusion prevention mask according to the present embodiment is formed by using the above mask ink, forming a pattern by inkjet printing, drying at a predetermined temperature, and baking at a higher temperature. The drying conditions are determined by the boiling point of the solvent contained in the mask ink, and the drying temperature and drying time are, for example, 2 to 30 minutes at a temperature of 150 ° C. or higher and 250 ° C. or lower. The firing conditions are determined by the solute contained in the mask ink, and the firing temperature and firing time are, for example, fired at a temperature of 500 ° C. to 700 ° C. for 10 minutes to 60 minutes.

  The pattern of the diffusion preventing mask is formed in a linear shape or a dot shape so as to coincide with a region where diffusion of dopants and the like is finally prevented. In order to form the end face of the diffusion prevention mask so as to rise rapidly from the upper surface of the substrate, it is preferable that the substrate is heated when the mask ink is applied.

  By heating the substrate to 40 ° C. or higher, the end face of the diffusion preventing mask can be rapidly raised from the upper surface of the substrate. However, when the temperature of the substrate is too high, the nozzle portion of the ink jet head dries at the time of printing, making it difficult to stably perform ink jet printing. Accordingly, the heating temperature of the substrate is preferably 40 ° C. or higher and 80 ° C. or lower.

  When ink jet printing is performed, the drawing may be completed once. However, when the drawing shape is affected by the discharged solvent or the like, it is preferable to draw the drawing in a plurality of times. In other words, it is preferable to apply the mask ink in a plurality of times with the time for drying the applied mask ink being divided.

  Specifically, for example, when drawing a linear mask layer having a width of 0.9 mm and an interval of 0.1 mm over the entire surface of the substrate 1, first, the first time at a width of 0.9 mm and an interval of 1.1 mm. Draw. After the solvent is dried for a certain time, the second drawing is performed with a width of 0.9 mm and an interval of 1.1 mm with a shift of 1 mm from the first drawing pattern. By doing so, a linear mask layer having a width of 0.9 mm and an interval of 0.1 mm can be drawn over the entire surface of the substrate 1. The solvent drying time at this time is, for example, about 10 seconds to 5 minutes, depending on the drying rate of the solvent, the degree of influence of the remaining solvent, and the time required for the actual process.

  Hereinafter, an example of the manufacturing method of the solar cell using the formation method of a diffusion prevention mask is demonstrated. In addition, the manufacturing method of the solar cell of this invention is not limited to the following, It applies to the manufacturing method of the general solar cell using the formation method of the diffusion prevention mask of this invention.

  FIG. 3 is a cross-sectional view for explaining the method for manufacturing the solar cell according to the present embodiment. The method for manufacturing a solar cell according to this embodiment is a method for manufacturing a solar cell in which a diffusion prevention mask is formed using an inkjet method.

  As shown in FIG. 3A, the mask layer 2 is formed on the upper surface of the silicon substrate 1 by applying the above-described mask ink to a predetermined region using an inkjet method. The substrate 1 including the mask layer 2 is baked.

  Here, as the silicon substrate 1, for example, a silicon substrate made of p-type or n-type silicon crystal is used. A fine uneven structure called a texture structure may be formed on the front surface or the back surface of the silicon substrate 1. A texture structure may be formed in any step of the method for manufacturing a solar cell in the present embodiment.

  As shown in FIG. 3B, the n-type dopant 3 is diffused on the surface of the silicon substrate 1. As a method for diffusing the n-type dopant 3, for example, phosphorus, which is an n-type dopant, is vapor-phase diffused, and the diffusion temperature at this time is 850 ° C. or higher. As a result, as shown in FIG. 3C, the n-type diffusion layer 4 is formed on the upper surface of the substrate 1 on which the mask layer 2 is not formed. Next, as shown in FIG. 3D, the mask layer 2 is removed, for example, by immersing the substrate 1 in a predetermined concentration of hydrofluoric acid.

  Thereafter, as shown in FIG. 3E, the mask layer 14 is formed by applying the above-described mask ink to the upper surface of the substrate 1 so as to cover the n-type diffusion layer 4 using an inkjet method. The substrate 1 including the mask layer 14 is fired.

  As shown in FIG. 3F, the p-type dopant 6 is diffused on the surface of the silicon substrate 1. As a method for diffusing the p-type dopant 6, for example, bromine as the p-type dopant 6 is vapor-phase diffused, or a solution containing bromine is applied on the substrate 1 and then baked at a temperature of 850 ° C. or higher. As a result, as shown in FIG. 3G, the p-type diffusion layer 7 is formed on the upper surface of the substrate 1 on which the mask layer 14 is not formed. Next, as shown in FIG. 3H, the mask layer 14 is removed, for example, by immersing the substrate 1 in a predetermined concentration of hydrofluoric acid.

  Subsequently, as shown in FIG. 3I, a passivation film 8 is formed on the upper surface of the substrate 1 by using a method such as thermal oxidation for the purpose of suppressing recombination of electrons and holes on the back surface of the substrate 1. Form. When the above texture structure is formed on the silicon substrate 1, for example, the light receiving surface of the substrate 1 opposite to the side on which the passivation film 8 is formed is immersed in a solution of about 80 ° C. containing potassium hydroxide and IPA. By making it, the texture structure which has a fine uneven structure on the surface can be formed. Thereafter, for example, a silicon nitride film having an antireflection effect of sunlight is formed on the upper surface.

  As shown in FIG. 3 (J), the passivation film 8 is formed by forming a contact hole at a position above the n-type diffusion layer 4 and the p-type diffusion layer 7 in the passivation film 8 using a photoetching method or the like. Patterning into a dot or line shape.

  Next, as shown in FIG. 3K, a back electrode is formed on the upper surface of the passivation film 8 and inside the contact hole. The back electrode includes an n-type electrode 9 electrically connected to the n-type diffusion layer 4 and a p-type electrode 10 electrically connected to the p-type diffusion layer 7.

  The n-type electrode 9 and the p-type electrode 10 can be formed by an evaporation method or the like heated by an electron beam in a high vacuum. As a material constituting the n-type electrode 9 and the p-type electrode 10, titanium, palladium, silver, or the like can be used. Furthermore, ohmic contact can be formed between the electrode 1 and the substrate 1 by heating the substrate 1 on which these electrodes are formed, for example, to a temperature of 400 ° C. or higher and 500 ° C. or lower.

  In the method for manufacturing a solar cell according to this embodiment, since the diffusion prevention mask is formed by the above method, it is possible to make the formation region of the diffusion layer coincide with the region where the diffusion prevention mask is formed. It is possible to suppress the occurrence of uneven diffusion in the part. Accordingly, the n-type diffusion layer 4 and the p-type diffusion layer 7 can be prevented from being short-circuited due to diffusion unevenness caused by the diffusion of the dopant at the end portion of the diffusion prevention mask as in the prior art. A solar cell can be manufactured. In addition, since the diffusion prevention mask is formed using the inkjet method, the manufacturing cost of the solar cell can be reduced.

  In addition, in this embodiment, although the manufacturing method of the solar cell was demonstrated, the formation method of the spreading | diffusion prevention mask of this invention is not limited to the solar cell field | area, In the semiconductor field | area, for example in the case of ion doping to a semiconductor layer, for example The present invention can be applied to various semiconductor formation methods such as formation of a diffusion prevention mask.

  Hereinafter, in the diffusion preventing mask, the minimum film thickness required for preventing the dopant from diffusing and the crack resistant film thickness, which is a limit for preventing the diffusion preventing mask from cracking when fired, were confirmed. Experimental example 1 will be described.

Experimental example 1
As the evaluation of the minimum film thickness for ensuring the masking property, film preparation samples having different film thicknesses were prepared by the spin coating method using the prepared mask ink, and calculated by VOC (volatile organic compounds) scan evaluation. The VOC scan evaluation is a probe scan of a voltage generated when light is irradiated on a sample from which the mask layers 2 and 14 are removed after the dopants 3 and 6 are diffused on the substrate 1 coated with the mask ink. This is a method for confirming whether or not a pn junction is formed.

  When the diffusion preventing mask has mask performance, an electromotive force is generated. Therefore, by performing this evaluation on samples having different film thicknesses, the minimum masking ensuring film thickness can be confirmed.

In addition, regarding the crack-resistant film thickness, using the prepared mask ink, spin-coating methods were used to prepare film-forming samples with different film thicknesses, and the presence or absence of cracks in the diffusion prevention mask after baking for 30 minutes at a temperature of 900 ° C. Was calculated by a method of confirming with a microscope.
(Sample 1)
Sample 1 was prepared as follows, and the minimum film thickness and the crack-resistant film thickness were confirmed. As a first solute, 18 g of TEOS (tetraethoxysilane) was dissolved in 17.7 g of ethanol as a second solvent. In this solution, 3.9 g of water in which 0.1 g of 35.5% hydrochloric acid was dissolved as a catalyst was added dropwise with stirring.

Then, it was made to react for 24 hours and the siloxane compound solution was obtained. Subsequently, 22.6 g of hexylene glycol was added to the solution as a first solvent and stirred, and then concentrated under reduced pressure using a rotary evaporator to obtain 22.6 g of ethanol (including ethanol generated by TEOS hydrolysis). The mask ink was prepared by removing. The composition of the prepared mask ink had a solute concentration (SiO ₂ conversion) of 12.4% by weight, a second solvent concentration of 22% by weight, and a viscosity of 7.7 mPa · s. Sample 1 had a minimum masking film thickness of 300 nm and a crack resistance film thickness of 1 μm.
(Sample 2)
Sample 2 was prepared as follows, and the minimum film thickness and the crack-resistant film thickness were confirmed. As the first solute, 19.3 g of TEOS was dissolved in 10.7 g of ethanol as a preparation solvent. Into this solution, 4.18 g of water in which 0.06 g of 35.5% hydrochloric acid was dissolved as a catalyst was added dropwise with stirring.

Then, it was made to react for 24 hours and the siloxane compound solution was obtained. Subsequently, 18.5 g of dipropylene glycol was added to the solution as a first solvent and stirred, and then concentrated under reduced pressure using a rotary evaporator to remove all the ethanol. Thereafter, 8 g of propylene glycol propyl ether was added as a second solvent and stirred to prepare a mask ink. The composition of the prepared mask ink had a solute concentration (SiO ₂ conversion) of 15.2% by weight, a second solvent concentration of 23% by weight, and a viscosity of 17.5 mPa · s. Sample 2 had a minimum masking film thickness of 300 nm and a crack resistance film thickness of 1 μm.

(Samples 3, 7, 9-10)
In the same manner as for sample 1, the first solute (for sample 7, the second solute) was dissolved in the second solvent. Into this solution, water in which the catalyst was dissolved was dropped and reacted to prepare a siloxane compound solution. Subsequently, after adding the first solvent and stirring, a mask ink was prepared by removing a part of the second solvent by concentration under reduced pressure. At this time, the added material and the composition of the prepared mask ink are shown on the left side of Table 1. In addition, the viscosity of the formed mask ink, the minimum mask property ensuring film thickness, and the crack-resistant film thickness are shown on the right side of Table 1.

(Samples 4-6, 8, 11, 12)
In the same manner as in sample 2, the first solute (for samples 6 and 8, the second solute) was dissolved in the second solvent. In this solution, water in which the catalyst was dissolved was dropped and reacted to prepare a siloxane compound solution. Subsequently, the first solvent was added and stirred, and then the solvent for adjustment was completely removed by concentration under reduced pressure, and then the second solvent was added and stirred to prepare a mask ink. At this time, the added material and the composition of the prepared mask ink are shown on the left side of Table 1. In addition, the viscosity of the formed mask ink, the minimum mask property ensuring film thickness, and the crack resistant film thickness are shown on the right side of Table 1.

  Table 1 summarizes the additive materials, weight ratios, viscosities, minimum maskable film thicknesses and crack-resistant film thicknesses of Samples 1 to 12. From this experiment, it was confirmed that the minimum film thickness ensuring the mask property was 0.3 μm and the crack-resistant film thickness was 1 μm.

  In Table 1, each abbreviation represents the following compound. TEOS: Tetraethoxysilane, TPOS: Tetrapropoxysilane, MTES: Methyltriethoxysilane, DMDES: Dimethyldiethoxysilane, PGP: Propylene glycol propyl ether, IPA: Isopropyl alcohol, PGME: Propylene glycol n-methyl ether, HG: He Xylene glycol, DPG: dipropylene glycol.

  Hereinafter, in Experimental Example 2 in which a mask defect region, which is a region that is equal to or less than the minimum film thickness ensuring the mask property, is confirmed in the diffusion prevention mask formed using the inkjet method. explain.

Experimental example 2
(Example 1)
The diffusion preventing mask of Example 1 was produced as follows. The silicon single crystal substrate from which the damaged layer has been removed is heated to 50 ° C., the mask ink prepared in the above sample 1 is applied to the surface by ink jet printing, and the mask layer is dried at 200 ° C. for 15 minutes. Formed.

FIG. 4 is a diagram showing the results of measuring the shape of the mask layer formed in Example 1. As shown in FIG. 4, the mask layer had a thickness b of the thinnest portion at the center portion of 0.65 μm and a film thickness a of the thickest portion at the end portion of 0.92 μm. FIG. 5 is an enlarged view showing a portion located at the end of the mask layer in FIG. As shown in FIG. 5, the mask defect region c that is 0.3 μm or less, which is the minimum film thickness ensuring maskability, was 0.04 μm.
(Examples 2 to 8)
The diffusion prevention masks of Examples 2 to 8 were produced as follows. A mask layer was formed on the silicon single crystal substrate by the same method as in Example 1 except that the mask inks used in inkjet printing were prepared in Samples 2 to 8 above. Table 2 summarizes the results of confirmation of the film thickness at the center, the film thickness at the end, and the mask defect area in the diffusion prevention masks of Examples 1 to 8.

  As shown in Table 2, in the diffusion preventing masks in Examples 1 to 8, the thickness of the thinnest portion in the central portion exceeds 0.3 μm, which is the minimum film thickness ensuring mask property, and is the thickest in the end portion. The film thickness of the part was less than 1 μm which is the crack-resistant film thickness.

  Hereinafter, Experimental Example 3 in which the characteristics of the solar cell in which the diffusion prevention mask is formed using the inkjet method will be described.

Experimental example 3
(Examples 9 to 16)
The silicon single crystal substrate having the mask layer produced in the above Examples 1 to 8 was baked at a temperature of 600 ° C. for 30 minutes, and then phosphorus was vapor-phase diffused at a temperature of 900 ° C. As a result, the n-type dopant 3 was diffused in the region where the mask layer 2 of the substrate 1 was not formed, and the n-type diffusion layer 4 was formed. Subsequently, the mask layer 2 remaining on the surface was removed by immersing the silicon substrate 1 on which the n-type diffusion layer 4 was formed in hydrofluoric acid.

  Thereafter, the silicon substrate 1 is again heated to a temperature of 50 ° C., the mask ink prepared in Sample 1 is applied to the surface of the silicon substrate 1 by ink jet printing, and dried at a temperature of 200 ° C. for 15 minutes to thereby form a mask layer. 14 was formed. Next, after baking for 30 minutes at a temperature of 600 ° C., boron was vapor-phase diffused at a temperature of 900 ° C. As a result, the p-type dopant 6 was diffused in the region where the mask layer 14 of the silicon substrate 1 was not formed, and the p-type diffusion layer 7 was formed. By immersing the silicon substrate 1 on which the n-type and p-type diffusion layers 4 and 7 were formed in hydrofluoric acid, the mask layer 14 remaining on the surface was removed.

  Subsequently, a silicon nitride film is formed as a passivation film 8 on the surface of the silicon substrate 1 on which the n-type and p-type diffusion layers 4 and 7 are formed, and the n-type diffusion layer 4 and the p-type are formed by photolithography. A contact hole was formed above the diffusion layer 7. Thereafter, a back electrode was formed on the upper surface of the passivation film 8 and inside the contact hole. The back electrode includes an n-type electrode 9 electrically connected to the n-type diffusion layer 4 and a p-type electrode 10 electrically connected to the p-type diffusion layer 7. The conversion efficiency and Id (reverse current) were confirmed as characteristics of the solar cell manufactured as described above.

  Table 3 summarizes the results of confirming the characteristics of the solar cells of Examples 9-16.

  As shown in Table 3, the solar cells of Examples 9 to 16 had a conversion efficiency of about 18%, an Id of 0.02, and exhibited good characteristics.

  Hereinafter, Experimental Example 4 in which the characteristics of the solar cell using the mask ink adjusted in Samples 9 to 13 were confirmed as a comparative example will be described.

Experimental Example 4
(Comparative Examples 1-5)
A mask layer 2 was formed by the same method as in Example 1 except that the mask ink used in ink jet printing was prepared in Samples 9 to 13. Here, in Comparative Examples 1 and 2, the same mask ink was used, and the mask layer 2 having a different film thickness was formed by adjusting the coating amount of inkjet printing.

  In Comparative Examples 4 and 5, by using the same mask ink and adjusting the application region of inkjet printing, the mask layer 2 having a different line width (the same line width as in Examples 9 to 16 for Comparative Example 4 and Comparative Example) About 5, the line width twice as large as Examples 1-8 was formed. Subsequently, a solar cell was produced in the same manner as in Example 9. Table 4 summarizes the results of confirming the film thickness of the thinnest part in the central portion of the formed mask layer 2 and the film thickness of the thickest part at the end, the defective mask region, and the characteristics of the solar cell.

  In Comparative Examples 1 and 2, since the mask ink having a large weight ratio of the second solvent was used as in Samples 9 to 10, the difference in film thickness between the central portion and the end portion of the mask layer 2 was large. As a result, in Comparative Example 1, since the thickness of the central portion of the mask layer 2 is thin, the mask performance of the region is insufficient, the dopant diffuses, and the conversion efficiency of the solar cell is reduced and the reverse current is reduced. An increase occurred. In Comparative Example 2, since the film thickness in the central portion of the mask layer 2 is set to be equal to or greater than the minimum film thickness ensuring the mask property, the film thickness of the thickest portion at the edge of the mask layer 2 is equal to or greater than the crack resistance film thickness. Since the crack occurred in that region, the conversion efficiency of the solar cell was lowered and the reverse current was increased.

  In Comparative Example 3, since the solute concentration was high as in Sample 11, when ink jet printing was performed, aggregates were deposited inside the ink, resulting in a decrease in mask performance at that portion.

  In Comparative Examples 4 and 5, since the mask ink having a small weight ratio of the second solvent was used, the film thickness at the center portion of the mask layer 2 was the largest, and the size of the defective mask region at the end portion was increased. It became. In Comparative Example 4, since inkjet printing was performed with the same line width as in Example 1, the p-type diffusion layer 7 and the n-type diffusion layer 4 partially contacted, resulting in a decrease in conversion efficiency of the solar cell. As a result, the reverse current greatly increased. On the other hand, in Comparative Example 5, since the mask layer 2 was drawn with a space twice as large as the mask width drawn in Example 1, the width of the diffusion layer could not be secured, and the conversion efficiency of the solar cell The result was not raised.

  In the diffusion prevention mask forming method of the present invention, the diffusion prevention mask having a thickness of a certain thickness or more as a whole is formed by forming the mask layer in the second region so as to be thicker than the first region. can do. Thereby, the performance of the diffusion preventing mask is improved, and the occurrence of uneven diffusion can be suppressed. In addition, the manufacturing cost can be reduced by simply forming a diffusion prevention mask using an inkjet method.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It does not become a basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description of the scope of claims. Further, all modifications within the meaning and scope equivalent to the scope of the claims are included.

  1 silicon substrate, 2 mask layer, 3 n-type dopant, 4 n-type diffusion layer, 5a second region, 5b first region, 6 p-type dopant, 7 p-type diffusion layer, 8 passivation film, 9 n-type electrode, 10 p-type electrode, 12 first solvent, 13 second solvent, 14 mask layer.

Claims (10)

A method of forming a dopant diffusion prevention mask on a substrate,
Forming a mask layer to be a diffusion prevention mask by applying a mask ink containing a silicon compound on a substrate using an inkjet method;
Baking the substrate including the mask layer,
The mask layer after firing includes a first region located in a central portion and a second region located in an end portion surrounding the first region in plan view,
The thickness of the mask layer in the first region is larger than a minimum masking ensuring film thickness that is a minimum film thickness necessary for the mask layer to function as a dopant diffusion preventing mask, and the mask in the second region is The thickness of the layer is smaller than the crack-resistant film thickness that is the maximum film thickness at which cracks do not occur in the mask layer in the state of the diffusion temperature of the dopant, and the mask layer is thicker in the second region than the first region. A method of forming a diffusion prevention mask formed to be   The method of forming a diffusion prevention mask according to claim 1, wherein the mask ink contains at least two kinds of solvents having different boiling points. The mask ink the general formula _{^{R 1 4-n Si (OR}} 2) n ( wherein R ^1, R ² _is any hydrocarbon group or an aromatic hydrocarbon group having 1 to 10 carbon atoms, n Is an integer of any one of 2 to 4), a siloxane compound obtained by hydrolytic polymerization of one or more alkoxysilanes, a first solvent having a boiling point of 150 ° C. or lower, a boiling point higher than that of the first solvent, and A second solvent having a high viscosity,
The method for forming a diffusion preventing mask according to claim 1, wherein the viscosity of the mask ink is 1 mPa · s or more and 30 mPa · s or less. The first solvent has a boiling point of 150 ° C. or lower and a viscosity of 30 mPa · s or lower,
2. The method for forming a diffusion prevention mask according to claim 1, wherein the second solvent has a boiling point of 150 ° C. or higher and 250 ° C. or lower and a viscosity of 30 mPa · s or higher.   The diffusion prevention mask according to claim 1, wherein a ratio of the siloxane compound in the mask ink is 10 wt% or more and 25 wt% or less, and a ratio of the first solvent is 5 wt% or more and 25 wt% or less. Forming method.   The mask ink is a siloxane compound obtained by hydrolyzing tetraethoxysilane, the thickness of the mask layer in the first region is 0.4 μm or more, and the thickness of the mask layer in the second region The method for forming an anti-diffusion mask according to claim 4, wherein the thickness is 1.0 μm or less.   The method for forming a diffusion prevention mask according to claim 3, wherein in the step of forming the mask layer, the substrate is heated to 40 ° C. or more and 80 ° C. or less.   The formation of the anti-diffusion mask according to any one of claims 3 to 6, wherein in the step of forming the mask layer, the mask ink is applied in a plurality of times with a time for drying the applied mask ink. Method.   The manufacturing method of a solar cell including the process of forming a diffusion prevention mask in the partial area | region of the substrate surface at least using the formation method of the diffusion prevention mask in any one of Claim 1-8. A method of manufacturing a solar cell using a diffusion prevention mask formed on a substrate,
Forming a first anti-diffusion mask in a region of the substrate surface using the method of forming a non-diffusion mask according to any one of claims 1 to 9,
Forming an n-type diffusion layer by diffusing an n-type dopant in a portion of the substrate surface where the first diffusion prevention mask is not formed;
Removing the first diffusion preventing mask;
Forming a second anti-diffusion mask in another region of the substrate surface using the method for forming an anti-diffusion mask according to any one of claims 1 to 9,
Forming a p-type diffusion layer by diffusing a p-type dopant in a portion of the substrate surface where the second diffusion prevention mask is not formed;
Removing the second diffusion preventing mask;
Forming a passivation film provided with contact holes on the surface of the substrate on which the n-type diffusion layer and the p-type diffusion layer are formed;
A back electrode composed of an n-type electrode electrically connected to the n-type diffusion layer and a p-type electrode electrically connected to the p-type diffusion layer is formed on the passivation film and in the contact hole. The manufacturing method of a solar cell provided with a process.

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