Method for etching silicon wafer

Abstract

The invention relates to a method for machining a silicon wafer, in particular to a method for etching a silicon wafer, comprising the steps of: preparing 15-18mol / ml of corrosive liquid ammonium bifluoride water solution; immersing the silicon wafer with the corrosive liquid; etching the silicon wafer for 300-600 seconds; taking off the silicon wafer and sequentially putting into purified water with 70-80 DEG C, 55-65 DEG C and 45-55 DEG C to cleaning for 3-5 minutes at every time; putting the cleaned silicon wafer into sulfuric acid and potassium dichromate solution and boiling; washing with jot water for 2-3 minutes; putting into the purified water and boiling for 2 minutes; immersing the silicon wafer into absolute ethyl alcohol and oscillating with ultrasonic wave for 3-7 minutes; and baking with an oven till to be dried and finished. The method replaces two-step cleaning liquid NH4OH / H2O2 / H2O and cleaning liquid HC1 / H2O2 / H2O with the ammonium bifluoride water solution, adopts the ammonium bifluoride water solution, effectively prevents the surface of the silicon wafer from roughing, and improving the activity of the silicon wafer.

Description

1. Technical field: [0001] The invention relates to a method for processing a silicon wafer, in particular to a method for etching a silicon wafer. 2. Background technology [0002] Since Kern and Puotein invented the RCA standard cleaning process in 1970, this process has gradually become the main cleaning process in the manufacturing process of silicon wafers for integrated circuits. It includes two-step cleaning SC21 (No. 1 cleaning NH 4 OH / H 2 O2 / H 2 O) and SC22 (No. 2 cleaning solution HCl / H 2 o 2 / H 2 O). In the alkaline N H4OH solution, the surface potential of the silicon wafer and the surface of the particles are both negative, which is very conducive to the removal of the particles. But basic NH 4 The strong anisotropic etching of silicon single crystal by OH solution increases the micro-roughness of the silicon wafer surface. As the gate oxide layer continues to thin, the surface micro-roughness will lead to uneven thickness of the oxide layer, which will a...

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Problems solved by technology

But basic NH 4 The strong anisotropic etching of silicon single crystal by OH solution increases the micro-roughness of the silicon wafer surface. As the gate oxide layer is continuously thinned, the surface micro-roughness will lead to uneven thickness of the oxide layer, which will affect the gate oxidation. layer integrity

In order to reduce the influence of alkaline cleaning solution on the surface micro-roughness, in recent years, many researchers have adopted the method of reducing NH in the cleaning process of SC21. 4 The method of OH concentration, the concentration is reduced from 15% to 0.105% or even lower. The corrosion rate of the diluted cleaning solution on the surface is greatly reduced, which can reduce the degree of surface roughness NH 4 When the OH concentration is reduced to a very low level, the corrosion rate of the silicon wafer surface can be reduced, but the alkaline solution still performs anisotropic corrosion on the surface to varying degrees, and the roughening of the silicon wafer surface cannot be completely avoided.