CN106684174A - Surface texturing method of polycrystalline silicon chips - Google Patents

Abstract

The invention discloses a method for making texture on the surface of a polycrystalline silicon wafer. The first corrosion and the second corrosion are carried out on the cleaned polycrystalline silicon wafer in sequence to complete the texture production. During the first corrosion, the cleaned diamond wire is cut into polycrystalline silicon. The slice is immersed in the first etching solution for etching, and during the second etching, the polycrystalline silicon wafer after the first etching is placed in the mist formed by the atomization of the second etching solution for etching. The method of the present invention is simple, low in cost, does not need to use any precious metals, does not need to use expensive large-scale equipment, and the texturing method can make texturing on the surface of diamond wire-cut polycrystalline silicon wafers, and the surface reflectance of diamond-wire-cut polycrystalline silicon solar cells can be minimized. drop below 10%. Moreover, the texturing method is simple, low in cost, does not need to use any precious metals, does not need to use expensive large-scale equipment, and has strong commercial application prospects.

Description

A kind of surface texturing method of polycrystalline silicon chip

technical field

The invention belongs to the technical field of solar cell manufacturing, and in particular relates to a method for making texture on the surface of a polycrystalline silicon wafer.

Background technique

At present, crystalline silicon is the most important solar cell material, occupying more than 90% of the market share. Crystalline silicon is mainly divided into monocrystalline silicon and polycrystalline silicon. Due to the lower cost of polysilicon, its market share has been surpassing that of monocrystalline silicon to dominate the photovoltaic market. For polycrystalline silicon solar cells, how to improve cell efficiency while reducing cost is a current research hotspot.

Fabricating textured surfaces on silicon wafers can effectively reduce light reflectance and increase light absorption, thereby improving the efficiency of solar cells. Diamond wire cutting polysilicon wafers has the advantages of fast cutting speed, high precision, and low loss of raw materials, but the preparation of its suede surface is a difficult problem for many researchers. Different from the polysilicon wafer cut by mortar wire, it is difficult to prepare a better texture for diamond wire cut polysilicon wafer using the traditional acid texturing process. Although dry etching methods such as reactive ion etching (RIE) and laser grooving can be used to prepare a relatively uniform and low-reflectance suede surface, these methods are costly and expensive, and the surface of the silicon wafer will also form More severe mechanical damage. The cost of preparing suede by metal-assisted catalytic corrosion is relatively high. At the same time, the treatment of waste liquid containing precious metals is also a problem that needs attention, and industrial production is relatively difficult.

Therefore, how to prepare the textured surface of diamond wire-cut polysilicon wafers with better anti-reflection effect at low cost is a current difficulty.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a method for making texture on the surface of a polysilicon wafer, which is suitable for preparing a textured surface on the surface of a diamond wire cut polysilicon, which can effectively reduce the reflectivity of the silicon wafer and improve the efficiency of solar cells, and Compared with the existing diamond wire-cut polysilicon surface texturing method, the method has lower cost.

A method for making texture on the surface of a polycrystalline silicon chip of the present invention, the polycrystalline silicon chip after cleaning is corroded for the first time and corroded for the second time to complete the texture making, and during the first corrosion, the diamond wire after cleaning is cut into the polycrystalline silicon chip Submerged in the first etching solution for etching, and during the second etching, the polysilicon wafer after the first etching is placed in the mist formed by the atomization of the second etching solution for etching.

In practical application, in the texturing method of the present invention, deionized water needs to be used for cleaning every time corrosion is performed in the texturing process, and after the second corrosion is completed, it needs to be washed with deionized water and then dried.

When making texture, the polysilicon wafers are first cleaned, and the cleaning method is as follows: sequentially ultrasonically clean the diamond-wire-cut polysilicon wafers in ethanol and DI, and then put the cleaned silicon wafers into RCA solution for further cleaning at 80°C to remove Organic matter and metal ions on silicon wafer surface.

The texturing method of the present invention has universal applicability and can be used for texturing on various polycrystalline silicon wafers. Preferably, the polycrystalline silicon wafers described in the present invention are diamond wire cut polycrystalline silicon wafers.

In the texturing method of the present invention, be used to remove the surface damage layer of the silicon wafer of diamond wire cut by corrosion for the first time on the one hand, on the other hand also form micron-scale etch pit (being worm-like etch pit morphology) on the surface of polysilicon by corrosion for the first time, Initially reduces reflectivity. Through the second etching, small holes are evenly etched on the micron-scale etching pits formed by the first etching to further reduce the reflectivity.

In the present invention, during the second etching, the polysilicon wafer that has been etched for the first time is placed in the mist formed by the atomization of the second etching solution for etching, so that the second etching solution formed after atomization becomes small droplets and condenses It is etched on the surface of the polysilicon wafer, so that dense and uniform nano-scale small holes are formed on the surface of the polysilicon.

When carrying out second time corrosion among the present invention, polycrystalline silicon chip can be placed in container (this container material requirement can not be corroded by the second corrosion solution, preferably polytetrafluoroethylene container among the present invention) through the first time corrosion, The second corrosion solution is generated by air compression atomization method, ultrasonic atomization method, etc. to generate mist, and then passed into the container with the silicon wafer for the second corrosion.

The first etching solution and the second etching solution, as well as the reaction time and reaction temperature during etching are directly related to the quality of the prepared textured surface, and further affect the reflectivity of the silicon wafer.

There is no special requirement for the first etching solution and the second etching solution, as long as they can corrode silicon wafers, they can be conventional etching solutions used in texturing silicon wafers.

Preferably, the first etching solution is a mixed solution of HF, HNO ₃ and deionized water. And the volume ratio of each component in the first corrosion solution is: HF:HNO ₃ :DI=1:(0.5～6):(1.5～7), wherein, HF represents hydrofluoric acid with a concentration of 49%, HNO ₃ means nitric acid with a concentration of 65%, and DI means deionized water. The reaction temperature during the first corrosion is 30-70°C, and the reaction time is 30-240s.

Preferably, the etching solution is a mixed solution of HF, HNO ₃ and deionized water. The volume ratio of each component in the second etching solution is HF:HNO ₃ :DI=(1～9):(1～9):1, wherein HF represents hydrofluoric acid with a concentration of 49%, and HNO ₃ represents Concentration is 65% nitric acid, DI means deionized water. The reaction temperature during the second corrosion is 30-60° C., and the reaction time is 1-20 minutes.

Further preferably, the polysilicon wafer is heated to the reaction temperature during the second etching.

By choosing the corrosion solution reasonably and setting the corrosion parameters, the final texture can achieve the best effect, so as to improve the efficiency of the solar cell.

Unless otherwise specified, the volume ratios of the components in the first etching solution and the second etching solution in the present invention refer to the volume ratios of the corresponding raw materials.

The texturing method of the present invention does not use any precious metals, the cost is low, and the waste liquid treatment is relatively simple; there is no need to use large-scale dry etching equipment, and the method is simple and easy; the prepared suede surface is relatively uniform, and the effective minority carrier life is relatively high , the reflectivity is low, and it is beneficial to improve the efficiency of the battery when applied to the solar cell. Moreover, the texturing method is universal and applicable to all polycrystalline silicon wafers, including diamond wire cut polycrystalline silicon wafers. It is worth mentioning that the texturing method of the present invention can effectively solve the problem of diamond wire-cut polysilicon wafer texturing. Life expectancy, has a strong market prospect.

Description of drawings

Fig. 1 is the SEM plan view of the suede surface of the diamond wire cut polysilicon wafer surface of embodiment 1;

FIG. 2 is a SEM cross-sectional view of the textured surface of the diamond wire-cut polysilicon wafer in Example 1. FIG.

detailed description

In order to better understand the present invention, the solutions of the present invention will be further described below in conjunction with specific embodiments and accompanying drawings, but the content of the present invention is not limited to the following embodiments.

Example 1

The surface texturing method of the polycrystalline silicon chip of the present embodiment, comprises the steps:

(1) Put a diamond-wire-cut polysilicon wafer with a thickness of 180±5 μm and a size of 30 mm×30 mm into ethanol and DI for ultrasonic cleaning, and then immerse it in RCA solution at 80 ° C to remove organic matter and metal on the surface of the silicon wafer ion;

(2) Put the cleaned silicon wafer into the etching solution 1 for the first etching. Sealed, the reaction temperature is 50°C, the reaction time is 90s, the corrosion solution 1 is a mixed solution of HF, HNO ₃ and DI, HF:HNO ₃ :DI=1:5:6, where HF means hydrogen with a concentration of 49% Hydrofluoric acid, HNO ₃ means nitric acid with a concentration of 65%, DI means deionized water;

(3) Clean the silicon chip obtained in step 2 with DI, put it in a polytetrafluoroethylene container, put the corrosion solution 2 into an ultrasonic atomizer, and pass the generated corrosion acid mist into the container with the silicon chip In the second corrosion. The reaction time is 5 minutes, the corrosion solution 2 is a mixed solution of HF, HNO ₃ and DI, HF:HNO ₃ :DI=2.25:0.75:1, where HF represents hydrofluoric acid with a concentration of 49%, and HNO ₃ represents a concentration of 65% % nitric acid, DI means deionized water, and the temperature is 60°C;

(4) Rinse the silicon wafer obtained in step 3 several times with DI, and dry to complete the texturing.

The volume ratios of the components in the first etching solution and the second etching solution in this embodiment all refer to the volume ratios of the corresponding raw materials.

Fig. 1 and Fig. 2 are respectively the plane view and the cross-sectional view of using the texturing method of this embodiment to texture the surface of polysilicon, and it can be seen that the texturing method of this embodiment can form dense and uniform textures on diamond wire cut polysilicon wafers surface, and the suede structure is a composite structure of micron and nanometer. The average reflectance of the suede surface prepared in this embodiment is about 6.8%.

Example 2

The surface texturing method of the polycrystalline silicon chip of the present embodiment, comprises the steps:

(1) Put a diamond-wire-cut polysilicon wafer with a thickness of 180±5 μm and a size of 30 mm×30 mm into ethanol and DI for ultrasonic cleaning, and then immerse it in RCA solution at 80 ° C to remove organic matter and metal on the surface of the silicon wafer ion;

(2) Put the cleaned silicon wafer into the etching solution 1 for the first etching. Sealed, the reaction temperature is 50°C, the reaction time is 90s, the corrosion solution 1 is a mixed solution of HF, HNO ₃ and DI, and HF:HNO ₃ :DI=1:5:6 where HF represents hydrogen with a concentration of 49% Hydrofluoric acid, HNO ₃ means nitric acid with a concentration of 65%, DI means deionized water;

(3) Clean the silicon chip obtained in step 2 with DI, put it in a polytetrafluoroethylene container, put the corrosion solution 2 into an ultrasonic atomizer, and pass the generated corrosion acid mist into the container with the silicon chip In the second corrosion. The reaction time is 10 minutes, the etching solution 2 is a mixed solution of HF, HNO ₃ and DI, and HF:HNO ₃ :DI=1.125:0.375:1, wherein, HF represents hydrofluoric acid with a concentration of 49%, and HNO ₃ represents a concentration of 65% nitric acid, DI means deionized water, the temperature is 50°C;

(4) Rinse the silicon wafer obtained in step 3 several times with DI, and dry it for later use.

The volume ratios of the components in the first etching solution and the second etching solution in this embodiment all refer to the volume ratios of the corresponding raw materials. The reflectance of the suede surface prepared in this embodiment is about 8.9%.

Example 3

The surface texturing method of the polycrystalline silicon chip of the present embodiment, comprises the steps:

(1) Put a diamond-wire-cut polysilicon wafer with a thickness of 180±5 μm and a size of 30 mm×30 mm into ethanol and DI for ultrasonic cleaning, and then immerse it in RCA solution at 80 ° C to remove organic matter and metal on the surface of the silicon wafer ion;

(2) Put the cleaned silicon wafer into the etching solution 1 for the first etching. Sealed, the reaction temperature is 50°C, the reaction time is 90s, the corrosion solution 1 is a mixed solution of HF, HNO ₃ and DI, and HF:HNO ₃ :DI=1:5:6, where HF means the concentration is 49%. Hydrofluoric acid, HNO ₃ means nitric acid with a concentration of 65%, DI means deionized water;

(3) Clean the silicon wafer obtained in step 2 with DI, put it in a polytetrafluoroethylene container, pass the corrosion solution 2 through a high-pressure gas nozzle to form a corrosion acid mist, and pass it into the container with the silicon wafer for the second corrosion . The reaction time is 1min, the corrosion solution 2 is a mixed solution of HF, HNO ₃ and DI, and HF:HNO ₃ :DI=4.5:1.5:1, wherein, HF represents hydrofluoric acid with a concentration of 49%, and HNO ₃ represents a concentration of 65% nitric acid, DI means deionized water, the temperature is 35°C;

(4) Rinse the silicon wafer obtained in step 3 several times with DI, and dry it for later use.

The volume ratios of the components in the first etching solution and the second etching solution in this embodiment all refer to the volume ratios of the corresponding raw materials. The reflectance of the suede surface prepared in this embodiment is about 9.5%.

Example 4

The surface texturing method of the polycrystalline silicon chip of the present embodiment, comprises the steps:

(1) Put the mortar wire-cut polysilicon wafer with a thickness of 180±5μm and a size of 30mm×30mm into ethanol and DI for ultrasonic cleaning, and then immerse it in RCA solution at 80°C to remove organic matter and metal on the surface of the silicon wafer ion;

(2) Put the cleaned silicon wafer into the etching solution 1 for the first etching. Sealed, the reaction temperature is 50°C, the reaction time is 90s, the corrosion solution 1 is a mixed solution of HF, HNO ₃ and DI, and HF:HNO ₃ :DI=1:5:6, where HF means the concentration is 49%. Hydrofluoric acid, HNO ₃ means nitric acid with a concentration of 65%, DI means deionized water;

(3) The silicon chip obtained in step 2 is cleaned with DI, and then placed in a polytetrafluoroethylene container, and the corrosion solution 2 is passed through a high-speed centrifugal spray nozzle to form a corrosion acid mist and passed into the container where the silicon chip is placed for the second time. corrosion. The reaction time is 2 minutes, the etching solution 2 is a mixed solution of HF, HNO ₃ and DI, and HF:HNO ₃ :DI=4.5:1.5:1, wherein, HF represents hydrofluoric acid with a concentration of 49%, and HNO ₃ represents a concentration of 65% nitric acid, DI means deionized water, the temperature is 35°C;

(4) Rinse the silicon wafer obtained in step 3 several times with DI, and dry it for later use.

The volume ratios of the components in the first etching solution and the second etching solution in this embodiment all refer to the volume ratios of the corresponding raw materials. The reflectance of the suede surface prepared in this embodiment is about 12.5%.

The above disclosures are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can carry out various changes and modifications to the present invention without departing from the spirit and scope of the present invention, All should be covered within the protection scope of the present invention.

Claims (9)

1. a kind of surface wool manufacturing method of polysilicon chip, it is characterised in that carried out to the polysilicon chip after cleaning successively for the first time Corrosion and second corrosion complete making herbs into wool, when corroding for the first time, the Buddha's warrior attendant wire cutting polysilicon chip after cleaning are immersed in into the Corrode in one etchant solution, during second corrosion, the polysilicon chip after first time corrodes is placed in by the second etchant solution Atomization formed mist in corroded.

2. the surface wool manufacturing method of polysilicon chip as claimed in claim 1, it is characterised in that the polysilicon chip is diamond wire The polysilicon chip of cutting.

3. the surface wool manufacturing method of polysilicon chip as claimed in claim 1 or 2, it is characterised in that the first etchant solution is HF, HNO₃With the mixed solution of deionized water.

4. the surface wool manufacturing method of polysilicon chip as claimed in claim 3, it is characterised in that each in first etchant solution Volume components ratio is：HF:HNO₃:DI=1:(0.5~6):(1.5~7), wherein, HF represents the hydrofluoric acid that concentration is 49%, HNO₃Represent that the nitric acid DI that concentration is 65% represents deionized water.

5. the surface wool manufacturing method of polysilicon chip as claimed in claim 4, it is characterised in that reaction temperature when corroding for the first time It is 30~70 DEG C to spend, and the reaction time is 30~240s.

6. the surface wool manufacturing method of polysilicon chip as claimed in claim 1 or 2, it is characterised in that the second etchant solution is HF, HNO₃With the mixed solution of deionized water.

7. the surface wool manufacturing method of polysilicon chip as claimed in claim 6, it is characterised in that each in second etchant solution Volume components ratio is HF:HNO₃:DI=(1~9):(1~9):1, wherein, HF represents the hydrofluoric acid that concentration is 49%, HNO₃Represent Concentration is 65% nitric acid, and DI represents deionized water.

8. the surface wool manufacturing method of polysilicon chip as claimed in claim 7, it is characterised in that reaction temperature when corroding for second It is 30~60 DEG C to spend, and the reaction time is 1~20min.

9. the surface wool manufacturing method of polysilicon chip as claimed in claim 8, it is characterised in that to described many when corroding for second Crystal silicon chip is heated to described reaction temperature.