CN101570897A - Corrosive liquid used for monocrystal line silicon matte preparation and monocrystal line silicon matte preparation method - Google Patents

Abstract

The invention relates to a corrosive liquid used for monocrystal line silicon matte preparation and a use method thereof. The components of the corrosive liquid are 1-5% (mass ratio) of NaOH or KOH aqueous solution, 1-50mg/L sodium dodecyl sulfate and 0-6% (mass ratio) of sodium silicate. Monocrystal line silicon slice is immerged in the corrosive liquid when preparing the matte and corroded for 10-60 minutes at the temperature of 70-95 DEG C, and the matte is obtained. The method of the invention is simple, inexpensive and stable and is applicable to mass industrialization.

Description

A kind of etching solution for the preparation of monocrystalline silicon textured surface and the preparation method of monocrystalline silicon textured surface

technical field

The invention relates to an etching solution for preparing monocrystalline silicon textured surfaces and a preparation method for monocrystalline silicon textured surfaces.

Background technique

Under the background of the energy crisis, renewable energy such as solar cells has been paid more and more attention by people. Solar energy is inexhaustible, and it is a clean energy with great development potential. From the appearance of solar cells in laboratories in the 1970s to the widespread use of solar cells in space and on the ground, solar cells have made great progress. Especially the monocrystalline silicon cell, because of its relatively low price, high efficiency, and its relatively simple and reliable process, has been widely valued by people in recent years.

In the preparation process of monocrystalline silicon cells, the first step is surface texturing. Texturing the surface can effectively reduce the reflectivity of the battery surface and improve the absorption of incident light by the battery. For example, the average reflectance of a polished monocrystalline silicon surface is about 35%, while that of a textured monocrystalline silicon surface can be reduced to about 10%. The preparation methods of monocrystalline silicon textured surface include chemical etching method, plasma etching method, mechanical groove method and so on. Because the chemical etching method is cheap and suitable for industrialization, it is widely used in the current production of single crystal silicon. The commonly used etching solution for chemical etching is 1-5% (mass ratio) NaOH or KOH solution, mixed with 3-8% (volume ratio) isopropanol or ethanol and 0.5-3% sodium silicate, at 75 Etch the silicon wafer for about 30 minutes at -90°C. Because NaOH is cheaper than KOH, and isopropanol is more stable than ethanol, most companies in the industry use a mixture of NaOH, isopropanol and sodium silicate as the corrosion solution.

In this corrosive solution, isopropanol has a good effect of reducing surface tension and eliminating _H2 bubbles of the reaction product. If the H ₂ bubbles cannot be well desorbed from the surface of the reacting silicon wafer, the attached H ₂ bubbles will prevent the further progress of the reaction, thereby causing uneven reaction. However, the boiling point of isopropanol is 82.5° C., so it volatilizes very badly during the reaction, resulting in instability of the solution ratio and poor repeatability in large-scale industrial production, which affects production.

In addition, in terms of the quality of the suede itself, the small and dense pyramid is more conducive to industrial production. Although from the perspective of reflectivity, there is no obvious difference between the small pyramid and the big pyramid, but in the industry, the small pyramid is more conducive to the subsequent silk screen printing process, which can make the metal of the silk screen and the pyramid more closely contact, and it is not easy to cause large series resistance. Or leakage and other issues. Moreover, the small pyramids are more conducive to maintaining the stability of the proportion of the etching solution because less silicon is etched each time, reducing the change of liquid caused by changes in the proportion of the etching solution in the industry, and improving production efficiency.

In order to improve the quality of suede and improve the stability of the process, many useful explorations have been made. For example, Chinese patents 200810122243.7, 200510111453.2 and 200810163097.2 respectively proposed the method of adding active agent on the basis of the currently used corrosion solution (NaOH or KOH solution mixed with ethanol or isopropanol and sodium silicate), and they respectively proposed adding 0.02‰～0.1‰ of Pb(NO ₃ ) ₂ or Pb, glucose and metaaluminate, although the addition of active agents can improve the quality of suede, but because it also depends on alcohol-based additives (ethanol or isopropanol) to Reduce surface tension and defoaming, so there is no solution to the instability of the corrosive solution. And China's patent application 200810163098.7 proposes to add ultrasound on the basis of NaOH aqueous solution, and achieve the effect of eliminating air bubbles through ultrasonic vibration. This method has a significant effect in eliminating air bubbles, but it cannot reduce the surface tension of the solution, because the uniformity of the suede surface is still insufficient. Room for improvement. Chinese patent 200510029562.X, adopts SiC sand blasting method and acid corrosion solution corrosion method to prepare suede surface, which has high cost and is not suitable for industrial production. In addition, Chinese patent 200810020206.5 uses 1.5% to 10% of sodium hydroxide or potassium hydroxide, 1 to 200 ppm of surfactant, 0.5% to 5% of sodium silicate, and 85.0% to 98.0% of deionized water to be used as a corrosion solution , It also avoids the addition of isopropanol or ethanol, but the preparation method is complicated, and it needs to be stirred in a dispersion pot for 10 to 30 minutes to completely dissolve the surfactant, then filter and discharge.

Figure 1 shows the morphology of a typical monocrystalline silicon textured surface prepared by the existing industrial technology. The preparation method is: 2% NaOH aqueous solution, 5% isopropanol and 2% sodium silicate are added, and the etching solution is prepared. Finish. The etching solution was kept at a constant temperature of 85° C., and mixed evenly by bubbling, and the monocrystalline silicon wafer was etched in the etching solution for 30 minutes to obtain pyramids with an average size of about 10 μm.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art, and propose an etching solution and a method for preparing a textured surface of monocrystalline silicon. The method uses industrially common sodium lauryl sulfate instead of isopropanol or ethanol as a reactive agent to reduce the surface tension of the solution and eliminate _H2 bubbles in the reaction product. Because sodium lauryl sulfate has better stability than isopropanol or ethanol, it realizes the repeatability of the texturing process very well, which is very beneficial to improve the stability and repeatability of the process in production. In addition, sodium lauryl sulfate is cheaper than isopropanol or ethanol, and the amount used is in the range of several to tens of milligrams per liter, which is very small, so it is more expensive than adding isopropanol or ethanol. Low.

The components of the etching solution involved in the present invention are as follows: 1% to 5% (mass ratio) of NaOH or KOH solution, 1mg/L-50mg/L of sodium lauryl sulfate, 0-6% (mass ratio) of silicon Sodium acid.

Utilize etching solution of the present invention to prepare the method for monocrystalline silicon textured surface as follows:

Prepare 1%-5% (mass ratio) NaOH or KOH aqueous solution, add 1mg/L-50mg/L sodium lauryl sulfate and 0-6% (mass ratio) sodium silicate to prepare corrosion solution. Put the etching solution at a temperature of 70-95° C., mix it uniformly by bubbling, and place the monocrystalline silicon wafer in the etching solution for 10-60 minutes to etch.

This method replaces the alcohol additives, ethanol or isopropanol in the conventional corrosion solution with very cheap sodium lauryl sulfate, which is common in the industry, and effectively overcomes the instability of the common corrosion solution, and can prepare uniform size, Pyramids covering the entire surface of the silicon wafer, and the size of the pyramids is distributed between 2-6 μm, which is smaller than the conventional pyramids.

The method is simple, high in stability and repeatability, and low in price, and is very suitable for industrial production.

Description of drawings

Fig. 1 is the topography of a typical monocrystalline silicon textured surface prepared by existing industrial technology;

Fig. 2 is the monocrystalline silicon textured topography figure that adopts the technology of the present invention to prepare;

Detailed ways

The corrosion solution components of the monocrystalline silicon suede surface of the present invention are: 1%～5% (mass ratio) NaOH or KOH solution, 1mg/L-50mg/L sodium lauryl sulfate, 0-6% (mass ratio) than) sodium silicate.

The content of the present invention will be described in detail below in conjunction with the embodiments.

Example 1: Prepare a 1% NaOH aqueous solution, add 1 mg/L sodium lauryl sulfate and 6% sodium silicate, and the corrosion solution is prepared. After the etching solution was mixed uniformly by bubbling at a constant temperature of 95° C., the monocrystalline silicon wafer was etched in the etching solution for 30 minutes to obtain pyramids with an average size of about 5 μm.

Example 2: Prepare 5% KOH aqueous solution, add 100 mg/L sodium lauryl sulfate and 0% sodium silicate, and the corrosion solution is prepared. The etching solution was kept at a constant temperature of 90° C., and mixed evenly by bubbling, and the monocrystalline silicon wafer was etched in the etching solution for 25 minutes to obtain pyramids with an average size of about 6 μm.

Example 3: Prepare 2% NaOH aqueous solution, add 10 mg/L sodium lauryl sulfate and 0.5% sodium silicate, and the corrosion solution is prepared. The etching solution was kept at a constant temperature of 85°C. After bubbling and mixing evenly, the monocrystalline silicon wafer was etched in the etching solution for 15 minutes to obtain a pyramid with an average size of about 5 μm. As shown in Figure 2, the pyramid It covers the surface of the silicon wafer and is uniform in size.

Example 4: Prepare 2% NaOH aqueous solution, add 20 mg/L sodium lauryl sulfate and 2% sodium silicate, and the corrosion solution is prepared. The etching solution was kept at a constant temperature of 70° C., and mixed uniformly by bubbling, and the monocrystalline silicon wafer was etched in the etching solution for 60 minutes to obtain pyramids with an average size of about 3 μm.

As shown in Figure 2, in the absence of isopropanol or ethanol as an additive, ideal pyramids with uniform size and covering the entire surface of the silicon chip were prepared by using the etching solution and the preparation method of the present invention. Moreover, the size of the pyramid prepared by the present invention is smaller than that prepared by conventional isopropanol as an additive (see Figure 1), so the present invention is more conducive to the preparation of batteries and the stability of industrial production.

Claims (2)

1, a kind of corrosive fluid that is used for the monocrystalline silicon suede preparation is characterized in that described corrosive fluid component is: the NaOH of 1～5% (mass ratio) or KOH solution, the sodium lauryl sulphate of 1-50mg/L, the water glass of 0-6% (mass ratio).

2, adopt the described corrosive fluid of claim 1 to prepare the method for monocrystalline silicon suede, it is characterized in that according to described corrosive fluid component configuration corrosive fluid, then described corrosive fluid is placed under the 70-95 ℃ of temperature, after mixing, monocrystalline silicon piece is placed in the described corrosive fluid corrosion 10-60 minute.

Images