CN102969397A

CN102969397A - Flocking method for reducing flocking dark fringes of polycrystalline silicon

Info

Publication number: CN102969397A
Application number: CN2012104535798A
Authority: CN
Inventors: 王敬蕊; 蔡晓晨; 陈锐
Original assignee: Guodian Technology & Environment Co Ltd
Current assignee: Guodian Technology & Environment Co Ltd
Priority date: 2012-11-13
Filing date: 2012-11-13
Publication date: 2013-03-13

Abstract

The invention discloses a flocking method for reducing flocking dark fringes of polycrystalline silicon. The method includes that polycrystalline silicon is placed in a flocking tank containing corrosive liquids for flocking, the corrosive liquid comprise HNO3, HF and alleviators, the alleviators are 0.02-0.03wt% of NH4F deionized water solutions, and the volume ratio of the HNO3, the HF and the alleviators is 5:1:(0.02-0.03). Compared with prior flocking technologies, the technological operation is simple, and the good applicability of industrial general flocking technologies is provided; surface flocking dark fringes can be apparently reduced, and the reflectivity of diffusing surfaces after silicon flocking is reduced by 0.3% to 1.5%; and the thickness reduction is reduced by 0.03g/piece to 0.04g/piece, and the battery conversion efficiency is improved by 0.13% to 0.15%.

Description

A kind of etching method that reduces the dark line of polysilicon making herbs into wool

Technical field

The present invention relates to a kind of etching method of polysilicon solar cell, particularly relate to a kind of etching method that reduces the dark line of polysilicon making herbs into wool.

Background technology

In solar battery process, the silicon chip surface matte can effectively reduce the surface reflectivity of solar cell, and it is one of key factor that affects the solar cell transformation efficiency.Compare with monocrystalline silicon, polysilicon is because grain-oriented diversity, adopt the anisotropy rot etching technique of aqueous slkali can't obtain uniform matte, can not effectively reduce the reflectivity of polysilicon, thereby the acid corrosion of isotropic is the method that generally adopts in the present polysilicon solar cell industrial production.Pattern after the making herbs into wool of polycrystalline silicic acid is relevant with the prescription of reflectivity and process for etching and sour liquid.At present industrial quarters employing process for etching is to use HF-HNO in the etching groove ₃Solution carries out acid corrosion to silicon chip and prepares matte.Etching mechanism is HNO ₃As strong oxidizer, in reaction, provide reaction needed hole, form one deck SiO at silicon chip surface ₂, this layer SiO then ₂Generate complex compound with HF acid and be removed.Yet after the making herbs into wool of polycrystalline silicic acid, silicon chip surface all can have quantity and distribute random " dark line ", and naked eyes look to be exactly the black filament of mixed and disorderly bulk, are also referred to as " staple ".These significantly reductions of dark line district minority carrier life time, EL and QE respond variation, directly have influence on the electricity conversion of polycrystal silicon cell.Studies show that dark line district is formed by the corrosion of the low angle boundary in the polysilicon chip, the quality of silicon chip directly affects what and distribution of dark line.Yet the prescription of corrosive liquid and corrosion rate are also for the quantity of dark line be distributed with impact.Reduce HF-HNO ₃The content of HF in the solution can effectively reduce the quantity of dark line.This be because, dark line is connected together by corrosion Wei Keng hole and forms, reduce the content of HF in the corrosive liquid and can control etch pit to the development of the inner depth direction of silicon chip, thereby can effectively reduce because reacting the too fast hole, microcorrosion hole that produces, reach the purpose that reduces dark line.But with the HF content, the chemical polishing effect of HNO3 strengthens, and suede corrosion hole size is more shallow, and the size change is large, and the matte reflectivity increases, thereby the polycrystal silicon cell electrical property descends.

Summary of the invention

The purpose of this invention is to provide a kind of etching method that reduces the dark line of polysilicon making herbs into wool, reduce the dark line quantity of polysilicon making herbs into wool matte, improve the electrical property of battery.

Technical scheme of the present invention is such: a kind of etching method that reduces the dark line of polysilicon making herbs into wool, comprise that polysilicon chip is put into the texturing slot that contains corrosive liquid carries out making herbs into wool, and it is characterized in that: described corrosive liquid comprises component HNO ₃, HF and moderator, described moderator is the NH4F deionized water solution of 0.02～0.03wt%, described HNO ₃, HF and NH ₄The F liquor capacity is than being 5:1:(0.02～0.03).

Preferably, described moderator is the NH of 0.03wt% ₄The F deionized water solution, described HNO ₃, HF and NH4F liquor capacity be than being 5:1:0.02.

The advantage of technical scheme provided by the present invention is, by at HF-HNO ₃Add NH in the corrosive liquid ₄F under the prerequisite that does not change the making herbs into wool pattern, can effectively reduce corrosion rate as the buffer of HF, reduces the formation in corrosion Wei Keng hole, thereby reduces the dark line of making herbs into wool, improves the electrical property of battery.The present invention compares with existing process for etching, and technological operation is simple, and has good applicability with the industrial general process for etching; Can significantly reduce the dark line of surface wool manufacturing, the diffusingsurface reflectivity reduces by 0.3～1.5% behind the silicon wafer wool making; The attenuate amount reduces by 0.03～0.04g/ sheet, and cell conversion efficiency improves 0.13～0.15%.

Description of drawings

Fig. 1 is the cell piece EL typical figure that process for etching of the present invention makes;

Fig. 2 is the cell piece EL typical figure that the prior art process for etching makes;

Embodiment

The invention will be further described below in conjunction with embodiment, but not as a limitation of the invention.

The process for etching that cell piece 1～5 adopts: use chain type polysilicon etching device to carry out polysilicon making herbs into wool, the texturing slot that polysilicon chip is contained corrosive liquid kept 100 seconds, then in succession enter in the KOH groove and residual acid, and removal porous silicon, enter the HCl groove and remove the metallic contaminants from surface ion, enter the HF groove and obtain hydrophobic surface, enter at last the drying tank oven dry.Wherein cell piece 1,2 corrosive liquids that adopt comprise component HNO ₃, HF and 0.02wt% NH ₄The F deionized water solution, HNO ₃, HF and NH ₄The F liquor capacity is than being 5:1:0.02.Cell piece 3,4 corrosive liquids that adopt comprise component HNO ₃, HF and 0.025wt% NH ₄The F deionized water solution, HNO ₃, HF and NH ₄The F liquor capacity is than being 5:1:0.025.The corrosive liquid that cell piece 5 adopts comprises component HNO ₃, HF and 0.03wt% NH ₄The F deionized water solution, HNO ₃, HF and NH ₄The F liquor capacity is than being 5:1:0.03.

The existing process for etching that cell piece 6～10 adopts, namely step is with the process for etching of cell piece 1～5, and wherein corrosive liquid only comprises component HNO ₃And HF, dose volume is than being 5:1.

The process for etching of comparison sheet 1, table 2 adding moderator and matte reflectivity and the making herbs into wool attenuate amount without the moderator process for etching: after adding moderator, diffusingsurface emissivity reflectivity reduces by 0.5%, non-diffusingsurface reflectivity reduces by 0.8%, the attenuate amount is reduced to the 0.43g/ sheet from the 0.47g/ sheet, has reduced the 0.04g/ sheet.After can finding out the adding moderator, when the reflectivity of silicon chip reduced, the attenuate amount also reduced, thereby had reduced the consumption of acid in the corrosive liquid, had reduced the making herbs into wool cost.

?	Diffusingsurface reflectivity (%)	Non-diffusingsurface reflectivity (%)	Attenuate amount (g)
				Cell piece 1	26.6	29.5	0.40
Cell piece 2	26.8	28.3	0.41
				Cell piece 3	26.5	27.8	0.40
Cell piece 4	26.4	28.2	0.41

Cell piece 5	26.8	28.1	0.41
				5 mean values	27.9	27.8	0.43

Table 1. cell piece 1～5 making herbs into wool back reflection rate and attenuate amount

?	Diffusingsurface reflectivity (%)	Non-diffusingsurface reflectivity (%)	Attenuate amount (g)
				Cell piece 6	29.1	28.5	0.49
Cell piece 7	29.0	28.7	0.48
				Cell piece 8	29.0	28.2	0.47
Cell piece 9	28.9	28.7	0.47
				Cell piece 10	29.0	28.8	0.48
5 mean values	28.4	28.6	0.47

Table 2. cell piece 6～10 making herbs into wool back reflection rates and attenuate amount

Cell piece 1～10 prepares solar battery sheet according to industrial polycrystal silicon cell technological process.Test EL collection of illustrative plates, and test unit for electrical property parameters can find out that from Fig. 1 and Fig. 2 the dark line quantity of cell piece that adopts the inventive method to make significantly reduces.Can find out that from the unit for electrical property parameters table of table 3 and table 4 battery efficiency on average improves 0.13%.

Table 3. cell piece 1～5 electrical performance data

Table 4. cell piece 6～10 electrical performance data

Claims

1. an etching method that reduces the dark line of polysilicon making herbs into wool comprises that polysilicon chip is put into the texturing slot that contains corrosive liquid carries out making herbs into wool, and it is characterized in that: described corrosive liquid comprises component HNO ₃, HF and moderator, described moderator is the NH of 0.02～0.03wt% ₄The F deionized water solution, described HNO ₃, HF and NH ₄The F liquor capacity is than being 5:1:(0.02～0.03).

2. the etching method of the dark line of minimizing polysilicon making herbs into wool according to claim 1, it is characterized in that: described moderator is the NH of 0.03wt% ₄The F deionized water solution, described HNO ₃, HF and NH ₄The F liquor capacity is than being 5:1:0.02.