KR100416739B1 - Method for fabricating silicon solar cell - Google Patents

Abstract

PURPOSE: A method for fabricating a silicon solar cell is provided to reduce fabricating cost by decreasing the consumption of a material, and to increase adaptability by maintaining the efficiency of the solar cell. CONSTITUTION: An oxide layer(23) is formed on a p-type silicon substrate(21). A photoresist pattern is formed on the oxide layer formed on the silicon substrate. The oxide layer is etched by using the photoresist pattern. The photoresist pattern is removed and a texturing process is performed. The oxide layer on the silicon substrate is etched. Phosphorous ions are diffused to the front and rear surfaces of the silicon substrate to form an n¬+ semiconductor layer(22). An oxide layer is formed on the n¬+ semiconductor layer on the silicon substrate. Aluminum is deposited on the rear surface of the silicon substrate and is sintered to form a p¬+ semiconductor layer. A photolithography process is performed to form a conductive metal layer in a predetermined region of the front surface of the silicon substrate. A lift-off process is performed. A conductive metal layer is deposited on the rear surface of the silicon substrate to form a rear surface electrode(24). Silver is electroplated on the conductive metal layer on the front surface of the silicon substrate.

Description

Method of manufacturing silicon solar cell

The present invention relates to a method for manufacturing a silicon solar cell, and more particularly, to a method for manufacturing a silicon solar cell which can obtain a high efficiency solar cell at a low manufacturing cost.

As a representative example of solar cells known to date, Passive Emitter Rear Locally diffused (PERL) solar cells developed by UNSW University in Australia, LBSF (Locally Back Surface Field) solar cells similar to the PERL, and point electrodes developed by Stanford University in the United States contact) solar cells.

However, these solar cells can be manufactured by repeating the semiconductor manufacturing process used in the manufacture of semiconductor integrated circuits (IC), but because the manufacturing cost is expensive, the price is not limited, such as space solar cells are limited only to special applications that require high efficiency. Is being used. Therefore, in order to obtain a commercially available solar cell, it is essential to design a simplified manufacturing process so that manufacturing cost can be reduced while maintaining high efficiency.

1 is a view showing the structure of a conventional LBSF solar cell. Referring to this, looking at the manufacturing method of the LBSF solar cell is as follows.

First, an oxide film is formed on the back surface of the p-type silicon substrate 11.

After the photoresist is applied on the upper surface of the silicon substrate 11 on which the oxide film is formed, only a predetermined portion is exposed using a shadow mask, and then the non-exposed portion is washed and developed. When the oxide film is etched using the photoresist pattern formed through this process as a mask and the photoresist is removed, a partial diffusion window is formed in the etched oxide film portion. The boron is diffused by predeposition by maintaining the surface where the boron is to be diffused at a high temperature. In this process, the partially diffused p ⁺ semiconductor layer 15 is formed.

Then, the oxide film which is a mask layer is etched.

After the oxide film is formed on the entire surface of the silicon substrate 11, a photoresist is applied on the oxide film, and then only a predetermined portion is exposed using a shadow mask, and then the non-exposed portion is washed and developed. The oxide film is etched using the photoresist pattern formed through this process as a mask, the photoresist is removed, and texturing is performed to form an inverse pyramid structure on the entire surface of the silicon substrate. Then, the oxide film which is a mask layer is etched.

Subsequently, an oxide film is formed over the entire silicon substrate 11 having the inverse pyramid structure, and a predetermined region of the oxide film is etched using a photoresist pattern as a mask using a lithography process.

The photoresist pattern is removed and n-type impurities are deeply diffused to form an n ⁺⁺ semiconductor layer 13. Electrons or holes are formed in the emitter region thus formed. At this time, the electrons reach the silicon substrate surface, the holes pass through the bulk region, and reach the rear surface of the silicon substrate so that current flows to the external terminals.

Next, the oxide film which is a mask layer is etched. Thereafter, the oxide film is formed again, and then n-type impurities are diffused thinly using the lithography process as described above to form the n ⁺ semiconductor layer 12. Next, the oxide film which is a mask layer is etched.

An oxide film 14 is then formed on the resultant, which can act as an antireflection layer.

Thereafter, a conductive metal layer is deposited on the back side of the silicon substrate using the photoresist pattern obtained by repeating the above-described lithography process to form the back electrode 16.

Subsequently, a conductive metal layer is formed by depositing a conductive metal on the entire surface of the silicon substrate using the photoresist pattern obtained by repeating the lithography process.

After performing the lift off process of removing the photoresist pattern and the unnecessary conductive metal layer, electroplating and annealing the conductive metal layer, the front electrode 17 is formed to form the solar cell illustrated in FIG. 1. Is completed.

As can be seen from the above, LBSF-type battery is subjected to various high-temperature processes because it undergoes several stages of oxidation process, photolithography process, and boron and phosphorous diffusion process in manufacturing. The process is very complicated. In addition, it is required to go through a cleaning process in order to prevent contamination of the silicon substrate and shorten the carry life between the processes. Therefore, it takes about two to three weeks of time and labor to manufacture the battery, and expensive diffusion equipment is necessary for the diffusion of boron.

Due to the above-mentioned reasons, the manufacturing price of the battery is increased, and there is a problem that the market formation is extremely limited compared to other general-purpose power generation systems, that is, thermal power or nuclear power generation, that is, solar power generation, which is clean energy generation.

The technical problem to be achieved by the present invention is to solve the above problems to provide a method of manufacturing a solar cell with high efficiency and low manufacturing cost.

1 is a view showing the structure of a typical LBSF solar cell,

2 and 3 is a view showing the structure of a solar cell manufactured according to the present invention.

<Explanation of symbols for the main parts of the drawings>

11, 21, 31 ... p-type silicon substrate

12, 22, 32 ... n ⁺ semiconductor layer

13 ... n ⁺⁺ semiconductor layer

14, 14 ', 23, 33, 33' ... oxide

15, 35 ... p ⁺ semiconductor layer

16, 24, 36 ... back electrode

17, 25, 37.Front electrode

An object of the present invention is to form an oxide film on a p-type silicon substrate; (b) forming a photoresist pattern on the oxide film on the entire silicon substrate and etching the oxide film using the photoresist pattern; (c) removing the photoresist pattern and performing texturing; (d) etching the oxide film on the entire surface of the silicon substrate; (e) diffusing phosphorus (P) on the front and rear surfaces of the silicon substrate to form an n ^{+ `</sup> semiconductor layer, and then forming an oxide film on the n <sup>+`} semiconductor layer on the front of the silicon substrate; (f) depositing aluminum (Al) on the entire back surface of the silicon substrate and then sintering to form a p ⁺ semiconductor layer; (g) forming a conductive metal layer on a predetermined region of the front surface of the silicon substrate using a lithography process; (i) performing a lift off process; (j) depositing a conductive metal on the back surface of the silicon substrate to form a back electrode; And (k) electroplating silver on the conductive metal layer on the front surface of the silicon substrate.

The object of the present invention is also (a) forming an oxide film on a p-type silicon substrate; (b) forming a photoresist pattern on the oxide film over the entire silicon substrate and etching the oxide film using the photoresist pattern; (c) removing the photoresist pattern and performing texturing; (d) etching the oxide film over the silicon substrate; (e) forming n ^{+ `} semiconductor layers by diffusing phosphorus (P) over the entire surface of the silicon substrate and the predetermined region behind the silicon substrate, and then forming an oxide film on the entire region of the silicon substrate and the predetermined region behind the silicon substrate. ; (f) diffusing aluminum (Al) in a predetermined region on the back surface of the silicon substrate and sintering to form a partial p ⁺ semiconductor layer; (g) forming a conductive metal layer on a predetermined region of the front surface of the silicon substrate using a lithography process; (i) performing a lift off process; (j) depositing a conductive metal on the back surface of the silicon substrate to form a back electrode; And (k) electroplating silver on top of the conductive metal layer on the front surface of the silicon substrate.

The conductive metal is at least one selected from the group consisting of nickel, copper, silver, aluminum, tin, zinc, indium, titanium, palladium and oxides thereof.

Hereinafter, a method of manufacturing a silicon solar cell according to an embodiment of the present invention will be described in detail with reference to FIG. 2.

Referring to this, oxide films are formed on the front and rear surfaces of the silicon substrate 21. Then, a photoresist pattern is formed over the entire silicon substrate on which the oxide film is formed, and the oxide film is etched using the photoresist pattern.

The photoresist pattern is removed and texturized to form inverted pyramids on the entire surface of the silicon substrate.

After etching the oxide film formed on the front surface of the silicon substrate 21, phosphorus (P) is diffused over the entire surface and the back surface of the silicon substrate to form an n ⁺ semiconductor layer (here, the n ⁺ semiconductor formed on the back surface of the silicon substrate). Layer is neutralized with p ⁺ semiconductor layer 24 which is formed later, resulting in disappearance). At this time, as the doping material of phosphorus doped POCl ₃ or P ₂ O ₅ at 800 to 900 ℃ to diffuse the doping concentration to 100 to 200Ω / ?. Here, it is preferable that the junction thickness of n ⁺ semiconductor layer is 0.5-1 micrometer.

As described above, the front surface of the silicon substrate has an inverted pyramid structure to absorb light well, and the pn junction surface is efficiently increased to increase the current density.

Next, an oxide film 23 is formed on the entire surface of the silicon substrate.

Aluminum is diffused and sintered over the entire back surface of the silicon substrate 21 to form a p ⁺ semiconductor layer (not shown). The p ⁺ semiconductor layer serves as a back surface field (BSF) to improve the collection of current.

A conductive metal layer is formed on the entire surface of the silicon substrate using a lithography process. Subsequently, the resist pattern on the front surface of the silicon substrate and the conductive metal layer formed in unnecessary areas are removed (lift off process).

Then, a conductive metal is deposited on the back surface of the silicon substrate to form the back electrode 24, and silver (Ag) is electroplated on the conductive metal layer on the front surface of the silicon substrate to form the front electrode 25.

Referring to Figure 3, it will be described a method of manufacturing a silicon solar cell according to another embodiment of the present invention.

Referring to this, oxide films are formed on the front and rear surfaces of the silicon substrate 31. Then, a photoresist pattern is formed over the entire silicon substrate 31 on which the oxide film is formed, and the oxide film is etched using the photoresist pattern.

The photoresist pattern is removed and texturized to form inverted pyramids on the entire surface of the silicon substrate.

After etching the oxide film formed on the entire surface of the silicon substrate 31, phosphorus (P) is diffused over a predetermined region on the front surface and the rear surface of the silicon substrate to form n ⁺ semiconductor layers 32 and 34, respectively. Then, an oxide film 33 is formed over the entire surface of the silicon substrate 31, and an oxide film 33 ′ is formed in a predetermined region behind the silicon substrate 31.

Subsequently, aluminum is partially deposited on the back surface of the silicon substrate 21 on which the n ⁺ semiconductor layer 34 and the oxide film 33 ′ are formed using a metal mask. When the resultant product is sintered to form a partial p ⁺ semiconductor layer 35, a passage through which a current flows from the front side to the back side of the silicon substrate is created.

The n ⁺ semiconductor layers 32 and 34 are in contact with a p-type silicon substrate to form a pn junction, which is a floating junction that is isolated from external terminals and does not affect the flow of current. . However, when the solar cell operates under sunlight, the junction accumulates electrons and pushes electrons toward the front of the solar cell, reducing the recombination of the silicon surface. In addition, the recombination of the silicon surface is reduced and the efficiency is increased by improving the open circuit voltage (V _oc ), which is an important constant for solar cell characteristics.

By using the lithography process, a conductive metal layer is formed on the entire surface of the silicon substrate. Subsequently, the resist pattern on the front surface of the silicon substrate and the conductive metal layer formed in unnecessary areas are removed (lift off process).

Then, a conductive metal is deposited on the back surface of the silicon substrate to form the back electrode 36, and silver (Ag) is electroplated on the conductive metal layer on the front surface of the silicon substrate to form the front electrode 37.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited only to the following Examples.

<Example>

An SiO ₂ film having a thickness of about 1300 μs was formed on the front and rear surfaces of the p-type silicon substrate. Then, a positive photoresist was applied to the upper portion of the oxide film on the entire surface of the silicon substrate in a thickness of about 1 μm, and only a predetermined portion was exposed using a shadow mask, and then the non-exposed portion was washed and developed.

The photoresist pattern formed through this process was used as a mask, and the SiO ₂ film was etched for 2 minutes and 30 seconds using a 7: 1 BHF solution, and then the photoresist was removed.

Thereafter, texturing was performed at 70 ° C. for 8 minutes using about 8% potassium hydroxide (KOH) solution. The SiO ₂ film on the entire silicon substrate was then etched for 2 minutes 30 seconds using a 7: 1 BHF solution.

POCl ₃ was diffused on the front and back of the silicon substrate for about 20 minutes at about 840 ° C. to about 150 to 240Ω /? After forming an n ^{+ `} semiconductor layer having a sheet resistance of a degree, a SiO ₂ film was formed over the n ⁺ semiconductor layer on the entire silicon substrate.

Aluminum was deposited on the entire back surface of the silicon substrate and sintered at 900 to 980 ° C. for 1 to 2 hours to form a p ⁺ semiconductor layer having a thickness of about 2 μm.

Using a lithography process, Td, about 600 mm thick Pd and Ag about 600 mm thick were sequentially deposited in the grooves on the front surface of the silicon substrate.

Thereafter, a lift off process was performed to remove the resist and unnecessary Td, Pd and Ag layers. Subsequently, aluminum was deposited on the back of the silicon substrate to form a back electrode, and Ag was electroplated to form a front electrode.

According to the above-described manufacturing method, it took about 8 hours for texturing, about 4 hours for phosphorus doping and oxidation process, about 4 hours for aluminum deposition and heat treatment, and about 4 hours for front electrode formation. Therefore, the manufacturing time is greatly reduced compared to the two to three weeks in the manufacture of a conventional solar cell significantly reduced the battery manufacturing price.

In addition, the battery manufactured according to the above embodiment was simpler to manufacture than the conventional case, was easy to manufacture and consumes less material, and the battery efficiency was very excellent.

The silicon solar cell manufactured according to the present invention is easy to manufacture and low consumption of materials can lower the manufacturing price. Thus, a battery manufactured at a lower manufacturing price than the prior art has a wide range of utilization because of its excellent efficiency.

The silicon solar cell manufactured according to the present invention is a semiconductor device that converts incident light into electrical energy, and is widely applicable to all fields requiring electrical energy. In other words, large-scale power generation using solar power from small household electrical appliances can be used for the construction of several MW-class power plants such as thermal power plants and nuclear power plants. In addition, energy sources of spacecraft or communication satellites can supply power over the life of satellites.

Claims (4)

(a) forming an oxide film on the p-type silicon substrate; (b) forming a photoresist pattern on the oxide film on the entire silicon substrate and etching the oxide film using the photoresist pattern; (c) removing the photoresist pattern and performing texturing; (d) etching the oxide film on the entire surface of the silicon substrate; (e) diffusing phosphorus (P) on the front and rear surfaces of the silicon substrate to form an n ^{+ `</sup> semiconductor layer, and then forming an oxide film on the n <sup>+`} semiconductor layer on the front of the silicon substrate; (f) depositing aluminum (Al) on the entire back surface of the silicon substrate and then sintering to form a p ⁺ semiconductor layer; (g) forming a conductive metal layer on a predetermined region of the front surface of the silicon substrate using a lithography process; (i) performing a lift off process; (j) depositing a conductive metal on the back surface of the silicon substrate to form a back electrode; And (k) electroplating silver on the conductive metal layer on the front surface of the silicon substrate. The method of claim 1, wherein the conductive metal is at least one selected from the group consisting of nickel, copper, silver, aluminum, tin, zinc, indium, titanium, palladium, and oxides thereof. (a) forming an oxide film on the p-type silicon substrate; (b) forming a photoresist pattern on the oxide film over the entire silicon substrate and etching the oxide film using the photoresist pattern; (c) removing the photoresist pattern and performing texturing; (d) etching the oxide film over the silicon substrate; (e) forming n ^{+ `} semiconductor layers by diffusing phosphorus (P) over the entire surface of the silicon substrate and the predetermined region behind the silicon substrate, and then forming an oxide film on the entire region of the silicon substrate and the predetermined region behind the silicon substrate. ; (f) diffusing aluminum (Al) in a predetermined region on the back surface of the silicon substrate and sintering to form a partial p ⁺ semiconductor layer; (g) forming a conductive metal layer on a predetermined region of the front surface of the silicon substrate using a lithography process; (i) performing a lift off process; (j) depositing a conductive metal on the back surface of the silicon substrate to form a back electrode; And (k) a method of manufacturing a silicon solar cell, comprising electroplating silver on top of the conductive metal layer on the front surface of the silicon substrate. The method of claim 3, wherein the conductive metal is at least one selected from the group consisting of nickel, copper, silver, aluminum, tin, zinc, indium, titanium, palladium, and oxides thereof.

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