TW201510179A - An etching additive for silicon wafer - Google Patents

Abstract

The present invention relates to a composition of an alkaline etching additive, which comprises (a) at least one selected from the group consisting of ethylene glycol ethers, (b) at least one selected from the group consisting of the bases, and (c) water. And to provide a simple method for preparing an alkaline etching additive, which just mixed (a) to (c), without heating or standing for phase separation that can be directly used as an additive. And further achieve the expected effect of etching the semiconductor silicon wafer. After etching treatment, the wafer evenly formed pyramid-shaped projections on the silicon wafer with its surface.

Description

Silicon wafer etching additive

The present invention relates to a composition of an alkaline etching additive added by etching a tantalum wafer for solar energy and a simple preparation method thereof.

The mechanism of action of solar cells is to use the photoelectric effect of the material to directly convert the energy of sunlight into electrical energy. In the process of solar cell materials, semiconductor germanium wafers are generally used as substrates, and the sources may be single crystal germanium wafers, polycrystalline germanium wafers, and amorphous germanium wafers; however, amorphous germanium wafers are less efficient and have a shorter lifetime, so less use. Polycrystalline germanium wafers are easy to break and have low conversion efficiency, but they are used in lower power systems because of their lower cost. At present, single crystal germanium wafers are more common, and their conversion efficiency is higher.

Solar energy can radiate electromagnetic waves of different frequencies and illuminate the semiconductor germanium wafer. Photons interact with free electrons in the semiconductor to generate current. However, the photoelectric effect depends on the frequency of the light rather than the intensity of the light, and the current is generated only when the frequency exceeds a critical value that produces a photoelectric effect. Therefore, in order to improve the efficiency of photoelectric conversion of solar cells, an etchant is usually used to process the germanium wafer, in order to increase the roughness of the surface and the low reflectance, so that When the sun shines on the germanium wafer, it reduces reflections and reduces energy loss.

While this patent is directed to the etching of single crystal germanium wafers, the etchant is usually alkaline. The previous example is isopropyl alcohol plus an aqueous solution of potassium hydroxide, which destroys the surface structure of the germanium wafer and is anisotropically etched, plus An additive further forms a pyramid-like relief structure on the surface of the tantalum wafer. The composition of this additive is the key to shape and surface uniformity.

WO 2007/129555 proposes a method for producing a semiconductor tantalum substrate and an etchant comprising a basic etchant selected from the group consisting of a carboxylic acid having at least one carboxyl group, a carbon number of 1 or more and 12 or less, or a salt thereof. The semiconductor substrate is etched to form an uneven structure on the surface, and the effect of reducing the reflectance of the surface of the ruthenium substrate is achieved.

TW 2013/22326 proposes a method for treating tantalum wafers by using a treatment liquid containing a cellulose ether to wet the surface of the tantalum wafer, texturing the surface, increasing the surface roughness, and also coupling the sun. The purpose of light.

WO 2010/052545 describes a texturing etching technique for a solar tantalum wafer in which an etching additive is used by using a polyethylene glycol and adding a base, and the solution is divided into two phases by heating or standing, and the lower is taken. One phase of the concentration is used as an additive, and the surface of the treated tantalum wafer exhibits a pyramid-like uneven structure. The lack of it is that the preparation process is complicated, and it is necessary to spend more time waiting for phase separation, and the etching quality may be unstable due to the long-term placement of the liquid.

This patent discloses a composition of an alkaline etching additive applied to semiconductor germanium wafer etching, which can eliminate the need to wait for the phase separation time or the energy consumption caused by heating during the preparation process. The raw material needs to be uniformly mixed with pure water to be prepared.

In the additive of the present invention, at least one component is selected from the group consisting of glycol ethers, and the other component is selected from the group consisting of alkalis, wherein the glycol ethers are selected from the group consisting of ethylene glycol monomethyl ether and ethylene glycol. Ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol monomethyl ether , diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene One or more of a group of dibutyl ethers. The base is preferably sodium hydroxide or potassium hydroxide.

In this additive, the weight composition ratio of the glycol ethers is 10 to 70%, and the optimum ratio is 15 to 50%; the weight composition ratio of the alkalis is 1 to 40%, and the optimum ratio is 3 to 20%. The rest is pure water.

However, although this patent can easily prepare the alkaline etching additive, the quality of the etching effect is not lowered, and the semiconductor germanium substrate is immersed in the etching liquid containing the above additive, characterized by the treated germanium. The wafer, which has a uniformly arranged pyramid-like projection on its surface, is an ideal etched pattern.

Adding at least one or two in the etching solution of this patent The above glycol ethers are intended to be added to the etching solution as an additive after being mixed with a base, so that a pyramid-shaped projection of an appropriate size can be formed on the surface of the crucible wafer, as shown in the first and second figures. . In order to make the structure of the protrusion more complete and uniform, a little low foaming surfactant can be added as a blending.

The first figure is the result of taking a magnification of 100 times using an OLYMPUS-BXFM optical microscope.

The second figure is the result of the second embodiment using an OLYMPUS-BXFM optical microscope at a magnification of 100 times.

The following two examples are selected to describe the operation method of this patent: the etching solution of the first embodiment is 30% by weight of isopropyl alcohol, 25% KOH, 44% water, 1% additive; wherein the additive component is 30% Ethylene glycol monomethyl ether, 10% KOH, 60% water. The silicon wafer is cut to an appropriate size, immersed in an etching solution and heated to 75-85 ° C for about 20 minutes, and then the silicon wafer is washed with pure water and dried, and then the surface of the processed wafer is observed by an optical microscope, and the result of the microscope is taken. As shown in Figure 1, the magnification is 100 times.

The etchant composition of the second embodiment is 30% by weight of isopropyl alcohol, 25% KOH, 43.5% water, 1.5% additive; wherein the additive component It is 25% ethylene glycol diethyl ether, 15% KOH, 60% water. The silicon wafer is cut to an appropriate size, immersed in an etching solution and heated to 75-85 ° C for about 20 minutes, and then the silicon wafer is washed with pure water and dried, and then the surface of the processed wafer is observed by an optical microscope, and the result of the microscope is taken. As shown in Figure 2, the magnification is 100 times.

Claims (8)

An alkaline etching additive comprising at least one component selected from the group consisting of glycol ethers and another component selected from the group consisting of alkalis, which are used in semiconductor semiconductor wafer etching for solar energy to form uniformly arranged pyramid-like protrusions on the surface of the wafer. . The alkaline etching additive according to claim 1, wherein the glycol ether is selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monobutyl Ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl One or more of a group of ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, and diethylene glycol dibutyl ether. According to claim 1, the base is preferably sodium hydroxide or potassium hydroxide. Any one of the preceding claims, wherein the etching additive accounts for 0.5 to 10% of the treatment liquid, and the optimum ratio is 1 to 5%. According to items 1 to 3 of the scope of patent application, the weight composition ratio of glycol ethers is 10 to 70%, and the optimum ratio is 15 to 50%; the weight composition ratio of alkalis is 1 to 40%, which is the best. The ratio is 3~20%. According to Item 5 of the patent application, the remaining proportion of the additive composition is pure water. According to item 5 of the scope of the patent application, the additive is characterized by the glycol ether After mixing with the alkali, it can be used directly without heating or standing still for phase separation. According to the seventh application of the patent application, the semiconductor germanium wafer is immersed in an etching solution containing the above additive, the processing temperature is between 65 and 90 ° C, and the optimum temperature is 75 to 85 ° C. It is characterized in that the treated tantalum wafer has a uniformly arranged pyramid-like projection on the surface.