阅读说明：本技术 一种金刚线切割多晶硅片的表面处理方法 (Surface treatment method for diamond wire cutting polycrystalline silicon wafer ) 是由 柯文杰 顾夏斌 杨世豪 于 2019-04-29 设计创作，主要内容包括：本发明公开了一种金刚线切割多晶硅片的表面处理方法。该方法为：利用喷砂工艺,先对硅片表面进行喷砂处理,再将其放入含有氢氟酸、硝酸和添加剂的混合溶液中进行制绒；所述喷砂工艺为湿法喷砂,所述湿法喷砂是指将水与磨料所混合的喷砂液利用泵加压经由喷嘴射出,均匀地对硅片表面进行冲击,使硅片表面产生凹凸不平的制绒表面。本发明喷砂方式成本低、工艺简单、不用使用化学品,亦不需要改变现有太阳能电池制绒工艺；通过本发明处理的硅片所生成的电池片,可达到良好的均匀绒面效果,并且消除硅片因金刚线切割所造成的线痕与色差。(The invention discloses a surface treatment method for a diamond wire-electrode cutting polycrystalline silicon wafer. The method comprises the following steps: carrying out sand blasting treatment on the surface of the silicon wafer by using a sand blasting process, and then putting the silicon wafer into a mixed solution containing hydrofluoric acid, nitric acid and an additive for texturing; the sand blasting process is wet sand blasting, wherein the wet sand blasting refers to that sand blasting liquid mixed by water and abrasive is pressurized by a pump and is ejected out through a nozzle to uniformly impact the surface of the silicon wafer, so that the surface of the silicon wafer is provided with an uneven texturing surface. The sand blasting method has low cost and simple process, does not use chemicals, and does not need to change the existing solar cell texturing process; the battery piece generated by the silicon piece processed by the invention can achieve good uniform suede effect and eliminate the line mark and color difference of the silicon piece caused by diamond wire cutting.)

1. A surface treatment method for diamond wire cutting polycrystalline silicon chips is characterized by comprising the following steps: carrying out sand blasting treatment on the surface of the silicon wafer by using a sand blasting process, and then putting the silicon wafer into a mixed solution containing hydrofluoric acid, nitric acid and an additive for texturing;

the sand blasting process is wet sand blasting, wherein the wet sand blasting refers to that sand blasting liquid mixed by water and abrasive is pressurized by a pump and is ejected out through a nozzle to uniformly impact the surface of the silicon wafer, so that the surface of the silicon wafer is provided with an uneven texturing surface.

2. The surface treatment method of a diamond wire-cut polycrystalline silicon wafer according to claim 1, characterized in that: the silicon wafer is a polycrystalline silicon wafer manufactured in a diamond wire cutting mode.

3. The surface treatment method of a diamond wire-cut polycrystalline silicon wafer according to claim 1, characterized in that: the abrasive in the wet sand blasting process is 150-1000 meshes of silicon carbide or aluminum oxide.

4. The surface treatment method of a diamond wire-cut polycrystalline silicon wafer according to claim 1, 2 or 3, characterized in that: the sand blasting liquid consists of water and abrasive, wherein the weight of the abrasive accounts for 10-40% of that of the sand blasting liquid.

5. The surface treatment method of a diamond wire-cut polycrystalline silicon wafer according to claim 4, characterized in that: the nozzle pressure is 0.05-0.3 MPa, and the impact time of the sand blasting liquid on the surface of the silicon wafer is 1-15 min.

6. The surface treatment method of a diamond wire-cut polycrystalline silicon wafer according to claim 5, characterized in that: the texturing solution is a mixed solution containing hydrofluoric acid, nitric acid and an additive, and the additive contains a surfactant.

7. The surface treatment method of a diamond wire-cut polycrystalline silicon wafer according to claim 5, characterized in that: the silicon wafer size is (156.75-157) mm, and the weight loss of the silicon wafer after sand blasting treatment is 1-10 mg.

8. The surface treatment method of a diamond wire-cut polycrystalline silicon wafer according to claim 5, characterized in that: the size of the silicon wafer is (156.75-157) mm, and the etching weight of the polycrystalline silicon wafer cut by diamond wires in the texturing process is 0.25-0.35 g.

Technical Field

The invention relates to the technical field of solar cells, in particular to a surface treatment method for diamond wire-electrode cutting polycrystalline silicon chips.

Background

At present, in the photovoltaic market, the traditional mortar cutting mode is gradually replaced by a diamond wire cutting mode which is low in cost, high in slicing speed and low in pollution in the polysilicon silicon wafer cutting technology. However, in the re-cutting process of diamond wire-cut polycrystalline silicon wafers, poor appearance problems such as wire marks and color differences occur due to changes in cutting efficiency caused by abrasion and breakage of diamond wires, unexpected shutdown of diamond wire cutting equipment, accumulation of a large amount of silicon powder in cutting gaps during cutting, and the like. At present, diamond wire-electrode cutting polycrystalline silicon wafers with poor appearances in the market account for about 1-8% of the production capacity of the whole diamond wire-electrode cutting polycrystalline silicon wafers, and the polycrystalline silicon wafers are degraded into B-grade wafers due to poor appearances, so that the selling price of the polycrystalline silicon wafers is influenced. If the prior conventional acid texturing mode of the additive is used for texturing the diamond wire polycrystalline silicon wafer with poor appearance, the texturing effects of low reflectivity and uniform appearance are difficult to achieve simultaneously, and the phenomena of line marks and color difference are more obvious after the anti-reflection layer is plated.

At present, in order to solve the problem of poor appearance of diamond wire cut polycrystalline silicon wafers, the main method for texturing the diamond wire polycrystalline silicon wafers comprises the following steps: direct additive methods, Reactive Ion Etching (RIE), Metal Catalyzed Chemical Etching (MCCE), sand blasting, and the like. For example, chinese patent CN107623053A provides a metal-catalyzed texturing method for reducing reflectivity of diamond wire-cut polysilicon wafer, which can eliminate diamond wire cutting traces. However, the metal catalytic texturing method is complicated in process, and requires the use of metal elements such as silver or copper, and the use of an ammonia solution for removing the metal elements, which causes environmental pollution. Chinese patent CN102468371A provides a reactive ion etching texturing method. However, the reactive ion etching equipment has high cost and low productivity, and is not suitable for industrial application. Chinese patents CN103339738B, CN105932078B and CN101814550A all disclose a method of sand blasting diamond wire-cut polycrystalline silicon wafer. However, the appearance state of the diamond wire-cut polycrystalline silicon wafer after sandblasting, which has poor appearance such as wire marks or color difference, has not been studied. In summary, the existing surface treatment method for diamond wire cutting polycrystalline silicon wafers generally has the problems of complex process, high cost, environmental pollution and the like.

Disclosure of Invention

The invention aims to provide a surface treatment method for diamond wire cutting polycrystalline silicon wafers, which is low in cost, simple in process and environment-friendly.

The technical solution for realizing the purpose of the invention is as follows: a surface treatment method for diamond wire cutting polycrystalline silicon wafer utilizes a sand blasting process, firstly carries out sand blasting treatment on the surface of the silicon wafer, and then puts the silicon wafer into a mixed solution containing hydrofluoric acid, nitric acid and additives for texturing;

the sand blasting process is wet sand blasting, wherein the wet sand blasting refers to that sand blasting liquid mixed by water and abrasive is pressurized by a pump and is ejected out through a nozzle to uniformly impact the surface of the silicon wafer, so that the surface of the silicon wafer is provided with an uneven texturing surface.

Further, the silicon wafer is a polycrystalline silicon wafer manufactured by a diamond wire cutting method.

Furthermore, in the wet sand blasting process, the abrasive is 150-1000 meshes of silicon carbide or aluminum oxide.

Furthermore, the sand blasting liquid consists of water and abrasive, wherein the weight of the abrasive accounts for 10-40% of that of the sand blasting liquid.

Further, the pressure of the nozzle is 0.05-0.3 MPa, and the impact time of the sand blasting liquid on the surface of the silicon wafer is 1-15 min.

Further, the texturing solution is a mixed solution comprising hydrofluoric acid, nitric acid and an additive, and the additive comprises a surfactant.

Further, the silicon wafer size is (156.75-157) mm, and the weight loss of the silicon wafer after sand blasting is 1 mg-10 mg.

Furthermore, the size of the silicon wafer is (156.75-157) mm, and the etching weight of the diamond wire cutting polycrystalline silicon wafer in the texturing process is 0.25-0.35 g.

Compared with the prior art, the invention has the following remarkable advantages: (1) the method has the advantages of low cost, stable process, difficult silicon chip breakage, no need of using metal and ammonia water harmful to the environment, no need of changing the existing solar cell manufacturing process, and upgrading the B-grade silicon chip with the original appearance defect into an A-grade silicon chip so as to improve the product output value; (2) in the sand blasting process, chemical additives and acid solutions are not required to be added, a high-hardness grinding material is used for carrying out a physical destructive processing mode on the polycrystalline silicon wafer, and the surface of the silicon wafer after being impacted is sunken due to the impact of particles to form a random concave surface and a damage layer, so that not only can a uniform appearance texture be achieved, but also the reflectivity of the surface of the silicon wafer can be obviously reduced, and further the photoelectric conversion efficiency of the solar cell is improved.

Drawings

FIG. 1 is a flow chart of a surface treatment method of a diamond wire-cut polycrystalline silicon wafer according to the present invention.

FIG. 2 is an external view of a diamond wire-cut polycrystalline silicon wafer having wire marks according to an example after sand blasting and acid texturing.

Fig. 3 is an external view of a diamond wire-cut polycrystalline silicon wafer having a wire mark in a comparative example after texturing only with an acid.

Detailed Description

The invention provides a surface treatment method of a diamond wire-cutting polycrystalline silicon wafer, which improves the diamond wire-cutting polycrystalline silicon wafer with poor appearance, such as a wire mark sheet and a color difference sheet generated by the diamond wire-cutting failure, by using a sand blasting method. With reference to fig. 1, the specific steps are as follows:

carrying out sand blasting treatment on the surface of the silicon wafer by using a sand blasting process, and then putting the silicon wafer into a mixed solution containing hydrofluoric acid, nitric acid and an additive for texturing;

the sand blasting process is wet sand blasting, wherein the wet sand blasting refers to that sand blasting liquid mixed by water and abrasive is pressurized by a pump and is ejected out through a nozzle to uniformly impact the surface of the silicon wafer, so that the surface of the silicon wafer is provided with an uneven texturing surface.

Specifically, the silicon wafer is a polycrystalline silicon wafer manufactured by a diamond wire cutting method.

Specifically, the abrasive in the wet sand blasting process is 150-1000 meshes of silicon carbide or aluminum oxide.

Specifically, the sandblasting liquid consists of water and an abrasive, wherein the weight of the abrasive accounts for 10-40% of the weight of the sandblasting liquid.

Specifically, the nozzle pressure is 0.05-0.3 MPa, and the impact time of the sand blasting liquid on the surface of the silicon wafer is 1-15 min.

Specifically, the texturing solution is a mixed solution containing hydrofluoric acid, nitric acid and an additive, and the additive contains one or more than one surfactant.

Specifically, the silicon wafer size is (156.75-157) mm, and the weight loss of the silicon wafer after sand blasting is 1 mg-10 mg. The corrosion weight of the diamond wire-electrode cutting polycrystalline silicon wafer in the texturing process is 0.25-0.35 g.

The battery piece generated by the silicon piece processed by the method has lower reflectivity than the battery piece processed by the conventional direct additive, and eliminates the line mark and color difference of the silicon piece caused by diamond wire cutting, thereby achieving the effect of qualified uniform texture. According to the mode for improving the diamond wire-cutting polycrystalline silicon wafer with poor appearance by using the sand blasting treatment, the corrosion weight of the diamond wire-cutting polycrystalline silicon wafer subjected to the sand blasting treatment is 0.02 g-0.08 g higher than that of the diamond wire-cutting polycrystalline silicon wafer not subjected to the sand blasting treatment under the same acid texturing condition due to the fact that the surface area of the silicon wafer subjected to the sand blasting treatment is larger in the acid texturing process of the silicon wafer.

The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.