TWI402995B - Processing method of semicondutor substrate - Google Patents

Description

Semiconductor substrate manufacturing method

The present invention relates to a process method, and more particularly to a method of fabricating a semiconductor substrate, and the fabricated semiconductor substrate can be applied to a photoelectric conversion module.

As the world's petrochemical fuels are gradually depleted, people are actively looking for and developing alternative energy sources, such as solar power, wind power and hydropower. Among them, the use of solar energy is the most important technological development direction. Sunlight can be irradiated in various parts of the world, and the process of solar energy conversion does not pollute the environment. For example, in the process of converting solar energy into electricity, there is no need to consume other energy sources and thus not cause greenhouses. The problem of the effect. However, the conversion efficiency of solar energy into electrical energy is easily limited by the mechanical design of the entire solar cell system.

At present, the steps of solar cell fabrication are to clean the impurity surface of the wafer surface by Deionized water; the surface of the wafer is structured and then the structured surface is cleaned by pickling; The surface of the wafer is subjected to a diffusion process. For example, a general solar cell adopts a P-type semiconductor substrate, so that an N-type semiconductor layer can be formed on the P-type semiconductor substrate by high-temperature thermal diffusion treatment; and then plasma etching is performed. Etching the edge of the wafer; removing the oxide generated on the surface of the wafer by etching; then forming an anti-reflective layer on the surface of the wafer by coating or chemical vapor deposition; and further resisting the anti-reflective layer A conductive electrode is formed on the surface. For example, the fabricated semi-finished wafer can be fabricated on the surface of the semi-finished product by silver offset screen printing or vapor deposition, and baked and dried at a high temperature; Finally, after a series of electrical tests, the current known solar cells can be fabricated. It can be seen that the fabrication of solar cells has to go through many complicated processes, and each of them has a significant influence on the overall efficiency of the solar cells.

Therefore, in order to improve the efficiency of today's solar cells, whether it is 24% conversion efficiency that can be achieved in the research and development stage, or 12 to 14% conversion efficiency that can be achieved by existing products, compared with the theoretical conversion value of 27%. More, there is still considerable room for improvement. Therefore, how to provide a semiconductor substrate processing method to produce a semiconductor substrate closer to the theoretically calculated photoelectric conversion efficiency value and to improve the photoelectric conversion efficiency of the solar cell has become one of important subjects.

In view of the above problems, an object of the present invention is to provide a method for fabricating a semiconductor substrate in which at least one surface of a semiconductor substrate is processed by a mechanical surface to improve photoelectric conversion efficiency of the semiconductor substrate.

To achieve the above object, the present invention provides a method for fabricating a semiconductor substrate, which is applied to a photoelectric conversion module, the process method comprising the steps of: providing a semiconductor substrate having two surfaces; and structuring at least one surface of the semiconductor substrate Processing; diffusing the surface of the semiconductor substrate; coating an anti-reflective layer on the surface of the semiconductor substrate; and mechanically surface treating at least one of the two surfaces of the semiconductor substrate, and the step is performed on any of the above two consecutive Between steps.

In one embodiment of the present invention, between the step of providing a semiconductor substrate and the step of structuring at least one surface of the semiconductor substrate, performing at least one of two surfaces of the mechanical surface-treated semiconductor substrate step.

In an embodiment of the invention, the method of performing the step of structuring at least one surface of the semiconductor substrate and the step of diffusing the surface of the semiconductor substrate is performed to perform mechanical surface treatment on both surfaces of the semiconductor substrate. At least one of the steps.

In an embodiment of the invention, the step of diffusing the surface of the semiconductor substrate and the step of applying the anti-reflective layer to the surface of the semiconductor substrate are performed to perform mechanical surface treatment on both surfaces of the semiconductor substrate. At least one of the steps.

As described above, the manufacturing method of the semiconductor substrate of the present invention is mainly a process of adding a mechanical surface treatment to the surface of the semiconductor substrate in the process steps of the conventional semiconductor substrate, and the surface system for performing the mechanical surface treatment may be a semiconductor substrate. At least one surface, the surface of the semiconductor substrate after mechanical surface treatment can be roughened, and at the same time, defects originally present in the interior of the semiconductor substrate can be collected on the surface and collectively processed by subsequent processes The defects accumulated on the surface are removed to improve the photoelectric conversion efficiency of the entire semiconductor substrate.

The method for manufacturing a semiconductor substrate according to a preferred embodiment of the present invention is applied to a photoelectric conversion module. The process method includes the steps of: providing a semiconductor substrate having two surfaces; and structuring at least one surface of the semiconductor substrate; Spreading the surface of the semiconductor substrate; applying an anti-reflection layer to the surface of the semiconductor substrate; mechanically treating at least one of the two surfaces of the semiconductor substrate, and performing the step of the two consecutive steps between.

According to the manufacturing method of the semiconductor substrate described above, the manufacturing method of the semiconductor substrate will be described below in three embodiments, and the description will be made with reference to the related drawings.

First embodiment

Please refer to FIG. 1 , which is a flow chart of a process of a semiconductor substrate according to a first embodiment of the present invention. The manufacturing method thereof includes steps S11 to S15.

Step S11 provides a semiconductor substrate which is a germanium substrate, which in turn may be a single crystal germanium substrate, a polycrystalline germanium substrate or an amorphous germanium substrate. In addition, the semiconductor substrate has two surfaces, which are respectively a first surface and a second surface, wherein the first surface can be incident on the light incident surface of the semiconductor substrate, and the second surface is disposed corresponding to the first surface. Backlit surface.

In this embodiment, after the semiconductor substrate is provided in step S11, the semiconductor substrate may be cleaned by ultrapure water and a chemical solvent to remove various fine particles (even nanometer-sized particles) on the surface of the wafer, and may be repeated. The cleaning process is repeated to completely clean the semiconductor substrate.

Step S12: treating at least one of the first surface and the second surface of the semiconductor substrate by mechanical surface treatment, in other words, the mechanical surface treatment may be performed only on the first surface of the semiconductor substrate, or only on the semiconductor The second surface of the substrate, or simultaneously applied to the first surface and the second surface of the semiconductor substrate, wherein the mechanical surface treatment method may be sandblasting, grinding (for example: wheel grinding, drilling, precision grinding, etc.) or other non- A chemical roughening method, after mechanical surface treatment, the surface of the semiconductor substrate has a microstructural feature.

In this embodiment, after at least one of the first surface and the second surface of the semiconductor substrate is mechanically surface-treated in step S12, a chemical solvent such as hydrofluoric acid is used to clean the semiconductor substrate, which may be due to mechanical surface treatment. A large amount of microparticles may be left to contaminate the surface of the semiconductor substrate. To reduce the degree of influence of such contamination on the next step, the surface of the semiconductor substrate may be cleaned after the mechanical surface treatment step is completed to ensure the next Process yield of the steps.

Step S13: structuring at least one surface of the semiconductor substrate. The surface generally refers to the first surface on which light is incident. However, depending on different product design specifications or requirements, the backlight may also be used. The structured treatment is performed on the two surfaces, and the mechanical surface treatment is different from the above-mentioned mechanical surface treatment. The means for structuring in this step may be a chemical acid etching process (the etching solvent may be, for example, hydrofluoric acid or nitric acid). Or a chemically alkaline etching process (the etching solvent may be, for example, potassium hydroxide or isopropyl alcohol), and the surface of the semiconductor substrate (including the first surface and/or the second surface) is anisotropic by any of the above methods. Anisotropic etching, for example, when the first surface of the semiconductor substrate (that is, the light incident surface) is structured, a plurality of micro pyramid-like structures are formed on the first surface of the semiconductor substrate. The minute structure caused by the structuring may be a spherical shape, a diamond shape, or various shapes and combinations thereof in addition to the pyramid shape. The main function of the structuring treatment is to remove the adhesion of metal impurities and organic substances on the surface, and also to form a roughening effect on the surface on which the reaction is performed, thereby reducing the reflection of light and thereby increasing the amount of light entering the inside of the semiconductor substrate. , so that the solar cell light conversion efficiency can be improved.

Step S14 is to perform a diffusion process on the surface of the semiconductor substrate (including the first surface and/or the second surface). For example, when the semiconductor substrate is a P-type semiconductor substrate, the N-type semiconductor is used in the diffusion process. The material diffuses onto the surface of the P-type semiconductor substrate. Conversely, when the semiconductor substrate is an N-type semiconductor substrate, the P-type semiconductor material is diffused onto the surface of the N-type semiconductor substrate during the diffusion process. Therefore, the interface between the P-type and N-type semiconductor layers is in contact with each other to form a PN junction. When the light enters the semiconductor substrate subjected to the diffusion process, the N-type semiconductor layer is formed due to the action of light and electricity conversion. The electrons are poured into the P-type semiconductor layer and fill the holes therein. At the same time, in the vicinity of the PN junction, a carrier-depletion region is formed by recombination of electron-holes, and in the P-type and N-type semiconductor layers. Because of the negative and positive charges, respectively, a built-in electric field is formed, and thus electrons generated in the semiconductor can flow in the battery, and an electron current (or current) is generated.

In addition, while the surface of the semiconductor substrate is diffused, an oxide layer containing phosphorus ruthenium oxide remains on the surface of the semiconductor substrate. However, since the generated oxide has a high resistance value, it is rather unfavorable for the electrical performance of the solar cell. Therefore, after the surface of the semiconductor substrate (including the first surface and/or the second surface) is diffused to form an oxide layer, the more dilute hydrofluoric acid solvent removes the oxide layer, thereby preventing the overall conductivity from being affected.

Step S15 is to apply an anti-reflection layer on the surface of the semiconductor substrate (including the first surface and/or the second surface). Since the refractive index difference between air and germanium is very large, light rays may be reflected when the light passes through the interface between the air and the crucible. In this case, an anti-reflective layer made of tantalum nitride (SiN) is applied to the semiconductor substrate to reduce reflection of incident light, and also has a function of passivation. Alternatively, other materials which can passivate the surface of the crucible may be coated on the semiconductor substrate to form an anti-reflection layer.

In this embodiment, after the anti-reflective layer is coated on the surface of the semiconductor substrate (including the first surface and/or the second surface) in step S15, an electrode layer may be further formed on the first surface and the second surface of the semiconductor substrate. For example, the first surface (that is, the incident surface of the light) can form the negative electrode layer, and the second surface (ie, the backlight surface) forms the positive electrode layer, and is on the first surface. The negative electrode layer formed may be composed of a plurality of bus bar electrodes and a plurality of finger electrodes. Therefore, when the semiconductor substrate converts the absorbed light into electrons, the finger electrode can be used to collect electrons generated by the semiconductor substrate to the electrically connected junction electrode, and finally, by connecting the bus electrode to the external load. The electrons generated by the photoelectric conversion reaction are collected and transmitted to the outside.

Second embodiment

Please refer to FIG. 2, which is a flow chart of a process for manufacturing a semiconductor substrate according to a second embodiment of the present invention. The manufacturing method thereof includes steps S21 to S25. The process method of this embodiment differs from the process method of the first embodiment in that the step of mechanically surface treating at least one of the two surfaces of the semiconductor substrate is performed by the step of structuring at least one surface of the semiconductor substrate Between the step of diffusing the above-described surface of the semiconductor substrate.

Step S21 provides a semiconductor substrate which is a germanium substrate. In addition, the semiconductor substrate has two surfaces, which are respectively a first surface and a second surface. Similar to the first embodiment, the first surface described herein is incident on the light incident surface of the semiconductor substrate. The two surfaces are backlight surfaces disposed corresponding to the first surface.

In this embodiment, after the step S21 is similar to the step after the step S11 of the first embodiment, the semiconductor substrate can be cleaned by ultrapure water and a chemical solvent to clean the semiconductor substrate.

Step S22 is also similar to step S13 in the first embodiment, and can be performed by a chemical acid etching process (the etching solvent can be, for example, hydrofluoric acid or nitric acid) or a chemical alkaline etching process (the etching solvent can be, for example, potassium hydroxide). Or isopropanol), the surface of the semiconductor substrate is anisotropically etched to structure the surface of the semiconductor substrate.

It should be noted that, in this embodiment, the mechanical surface treatment of step S23 is performed after the structuring step, that is, the mechanical surface treatment method described herein may be directed to the first surface of the semiconductor substrate and At least one of the second surfaces, in particular for the structured surface (possibly the first surface or the second surface or the first and second surfaces), wherein the method of mechanical surface treatment may be sand blasting, grinding (eg wheel grinding, drilling, precision grinding, etc.) or other non-chemical roughening methods.

In this embodiment, after step S23, similar to the step after step S12 in the first embodiment, a chemical solvent such as hydrofluoric acid is used to clean the semiconductor substrate to clean the surface of the semiconductor substrate, thereby ensuring the next step. Process yield.

Similar to step S14 in the first embodiment, step S24 performs a diffusion process on the surface of the semiconductor substrate (including the first surface and/or the second surface) to enable the semiconductor substrate to be diffused by the diffusion process. A P-type semiconductor layer, an N-type semiconductor layer and a PN junction are formed, so that when light enters the semiconductor substrate subjected to the diffusion process, since there are negative and positive charges in the P-type and N-type semiconductor layers, respectively, In order to form a built-in electric field, electrons generated in the semiconductor can flow in the battery, and an electron current (or current) is generated. In addition, while the surface of the semiconductor substrate is diffused, an oxide layer containing phosphorus ruthenium oxide remains on the surface of the semiconductor substrate, but since the oxide has a high resistance value, it is rather unfavorable to the electrical surface of the solar cell. After the surface is diffused and simultaneously forms an oxide layer, the oxide layer is removed with a dilute hydrofluoric acid solvent to prevent the overall conductivity from being affected.

Step S25 is similar to step S15 of the first embodiment, and coating an anti-reflective layer of a tantalum nitride material on the surface of the semiconductor substrate (including the first surface and/or the second surface) to reduce reflection of incident light. And there is also the role of passivation, which in turn improves overall performance. Alternatively, other materials which can passivate the surface of the crucible may be coated on the semiconductor substrate to form an anti-reflection layer.

In the present embodiment, the formation of the electrode layer is similar to that of the first embodiment, and thus will not be described herein.

Third embodiment

Please refer to FIG. 3, which is a flow chart of a process for manufacturing a semiconductor substrate according to a third embodiment of the present invention. The manufacturing method thereof includes steps S31 to S35. The process method of the present embodiment is different from the process method of the second embodiment in that the step of mechanically surface-treating at least one of the two surfaces of the semiconductor substrate is performed on the step of spreading the surface of the semiconductor substrate and coating An anti-reflective layer is disposed between the steps of the surface of the semiconductor substrate.

Step S31 provides a semiconductor substrate which is a germanium substrate. In addition, the semiconductor substrate has two surfaces, which are respectively a first surface and a second surface. Similar to the first embodiment, the first surface described herein is incident on the light incident surface of the semiconductor substrate. The two surfaces are backlight surfaces disposed corresponding to the first surface.

In this embodiment, after step S31, the semiconductor substrate can be cleaned by ultrapure water and a chemical solvent to remove various fine particles on the surface of the wafer, and the cleaning process can be repeated until the semiconductor substrate is completely cleaned.

Step S32 may be performed by a chemical acid etching process (the etching solvent may be, for example, hydrofluoric acid or nitric acid) or a chemical alkaline etching process (the etching solvent may be, for example, potassium hydroxide or isopropyl alcohol) to the surface of the semiconductor substrate ( The first surface and/or the second surface are included for anisotropic etching and structuring the surface.

Step S33: performing a diffusion process on the surface of the semiconductor substrate (including the first surface and/or the second surface), so that the semiconductor substrate can be formed by a diffusion process to form a P-type semiconductor layer, an N-type semiconductor layer, and a PN connection. Surface, similar to the above, the semiconductor substrate after the diffusion process has the effect of photoelectric conversion. In addition, while the surface of the semiconductor substrate is diffused, an oxide layer containing phosphorus ruthenium oxide remains on the surface of the semiconductor substrate, but since the oxide has a high resistance value, it is rather unfavorable for the electrical performance of the solar cell. After the surface is diffused and simultaneously forms an oxide layer, the oxide layer is removed with a dilute hydrofluoric acid solvent to prevent the overall conductivity from being affected.

It should be noted that, in this embodiment, after the oxide layer is formed on the surface of the substrate while the diffusion is formed and the oxide layer is removed, step S34 is performed, that is, the surface of the semiconductor substrate is processed by a mechanical surface treatment method ( Including the first surface and/or the second surface, in other words, the surface of the semiconductor substrate to be subjected to the mechanical surface treatment is not limited to the surface after the diffusion process has been performed, when the oxidation reaction is performed only on one surface of the semiconductor substrate (for example) : the first surface), the other surface (for example: the second surface) may also be mechanically treated at this time, and the mechanical surface treatment method may be sand blasting, grinding (for example: wheel grinding, drilling) Grinding, precision grinding, etc.) or other non-chemical roughening methods.

In the present embodiment, after the step S34, the semiconductor substrate is further cleaned with a chemical solvent such as hydrofluoric acid to clean the surface of the semiconductor substrate, thereby ensuring the process yield of the next step.

Step S35 is coating an anti-reflective layer of a tantalum nitride material on the surface of the semiconductor substrate (including the first surface and/or the second surface) to reduce reflection of incident light, and further has a function of passivation, thereby improving the overall efficacy. Alternatively, other materials which can passivate the surface of the crucible may be coated on the semiconductor substrate to form an anti-reflection layer.

In the present embodiment, the formation of the electrode layer is similar to that of the first embodiment, and thus will not be described herein.

According to the above, the present invention is mainly directed to the step of performing at least one of the two surfaces of the mechanical surface-treated semiconductor substrate, and performing the following steps of providing a semiconductor substrate and structuring at least one surface of the semiconductor substrate. And step of: applying a step of diffusing the surface of the semiconductor substrate to the surface of the semiconductor substrate by applying an anti-reflection layer to the surface of the semiconductor substrate, and mechanically treating the surface of the semiconductor substrate between two consecutive steps, The surface of the semiconductor substrate after mechanical surface treatment can be roughened, and at the same time, the defect originally existing in the semiconductor substrate is concentrated on the surface during the process, and then the surface is passivated by a subsequent process. Defects improve wafer quality. In addition, since the microstructure is formed on the surface after the mechanical surface treatment, the present invention can also increase the absorption rate of the semiconductor substrate with respect to sunlight, thereby improving the photoelectric conversion efficiency of the entire semiconductor substrate. It is worth mentioning that after the mechanical surface treatment of the semiconductor substrate has been experimentally verified, its photoelectric conversion efficiency can be significantly increased by more than 0.3%.

In summary, the manufacturing method of the semiconductor substrate of the present invention is mainly a process of adding a mechanical surface treatment to the surface of the semiconductor substrate in the process steps of the conventional semiconductor substrate, and the surface system for performing the mechanical surface treatment may be a semiconductor substrate. At least one surface. Compared with the prior art, the semiconductor substrate after mechanical surface treatment can actually increase the photoelectric conversion efficiency by 0.3% or more.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

S11～S15, S21～S25, S31～S35. . . step

1 is a flow chart showing a process of a semiconductor substrate according to a first embodiment of the present invention;

2 is a flow chart showing a process of a semiconductor substrate according to a second embodiment of the present invention;

3 is a flow chart showing a process of a semiconductor substrate according to a third embodiment of the present invention.

S21～S25. . . step

Claims (15)

A method for manufacturing a semiconductor substrate, which is applied to a photoelectric conversion module, the process method comprising the steps of: providing a semiconductor substrate having two surfaces; structuring at least one surface of the semiconductor substrate; Dispersing the surface; performing at least one of the surfaces of the semiconductor substrate by mechanical surface treatment; and coating an anti-reflective layer on the surface of the semiconductor substrate. The process of claim 1, wherein the step of diffusing the surface of the semiconductor substrate is performed, and an oxide layer is formed on the surface of the semiconductor substrate. The process of claim 2, wherein after the oxide layer is formed on the surface of the semiconductor substrate, the oxide layer of the surface is removed. The process of claim 1, wherein the semiconductor substrate is a germanium substrate. The process according to claim 4, wherein the germanium substrate is a single crystal germanium substrate, a polycrystalline germanium substrate or an amorphous germanium substrate. The process method according to claim 1, wherein the step of providing the semiconductor substrate further cleans the semiconductor substrate. The process of claim 1, wherein the semiconductor substrate is an N-type semiconductor substrate or a P-type semiconductor substrate. Such as the process method described in claim 7 of the patent, when the semiconductor When the substrate is an N-type semiconductor substrate, the step of diffusing the semiconductor substrate is to diffuse the P-type semiconductor material onto the semiconductor substrate. The process according to claim 7, wherein when the semiconductor substrate is a P-type semiconductor substrate, the step of diffusing the semiconductor substrate is to diffuse an N-type semiconductor material onto the semiconductor substrate. The process of claim 1, wherein the anti-reflective layer is made of tantalum nitride or other anti-reflective layer that can passivate the surface of the crucible. The process of claim 1, wherein the step of coating the anti-reflective layer on the surface of the semiconductor substrate further comprises forming at least one electrode layer on the surface of the semiconductor substrate. The process of claim 11, wherein the electrode layer has a plurality of bus electrodes and a plurality of finger electrodes. The process method of claim 1, wherein the mechanical surface treatment method is sandblasting, grinding or other roughening. The process of claim 1, wherein the step of mechanically treating at least one of the surfaces of the semiconductor substrate further cleans the semiconductor substrate. The process according to claim 14, wherein the cleaning of the semiconductor substrate utilizes hydrofluoric acid to clean the semiconductor substrate.