Method of processing silicon wafer
The inventive method for processing a silicon wafer is a method comprising step 11 in which a single crystal ingot is sliced into thin disc-like wafers; step 13 in which the surface of each wafer is lapped to be planar; step 14 in which the wafer is subjected to alkaline cleaning to be removed of contaminants resulting from preceding machining; and step 16 in which the wafer is alternately transferred between two groups of etching tanks one of which contain acidic etching solutions and the other alkaline etching solutions, wherein an additional step 12 is introduced between step 11 and step 13 in which a wafer is immersed in an acidic solution containing hydrofluoric acid (HF) and nitric acid (HNO 3 ) at a volume ratio of ⅛ to ½ (HF/HNO 3 ) so that degraded superficial layers occurring on the front and rear surfaces of the wafer as a result of machining can be removed and the edge surface of the wafer can be beveled. The inventive method simplifies the steps involved in the processing of a wafer, and reduces the intervention of alkaline cleaning accompanied with mechanical beveling, thereby reducing the risk of contamination due to metal impurities which may result from alkaline cleaning.
1. A method for processing a silicon wafer comprising:
a slicing step ( 11 ) in which a single crystal ingot is sliced into thin disc-like wafers;
a lapping step ( 13 ) in which the surface of each wafer is lapped to be planar;
an alkaline cleaning step ( 14 ) in which the wafer is subjected to alkaline cleaning to be removed of contaminants resulting from preceding machining; and
an etching step ( 16 ) in which the wafer is alternately transferred between two groups of etching tanks one of which contain acidic etching solutions and the other alkaline etching solutions, wherein:
a beveling step ( 12 ) is introduced between the slicing step ( 11 ) and the lapping step ( 13 ), in which the wafer is immersed in an acidic solution containing hydrofluoric acid (HF) and nitric acid (HNO 3 ) at a volume ratio of ⅛ to ½ (HN/HNO 3 ) so that degraded superficial layers occurring on the front and rear surfaces of the wafer as a result of machining can be removed and the edge surface of the wafer can be beveled.
2. A method of claim 1 wherein the etching using an acidic solution containing hydrofluoric acid and nitric acid is adjusted such that the total etching rate summed for both surfaces of a wafer is in the range of 0.1 to 1.0 μm/sec.
3. A method of claim 1 wherein the etching step ( 16 ) includes acidic etching ( 16 a ) followed by alkaline etching ( 16 b ), the alkaline etching solution has a concentration of 8 mol/l or higher, and the total etching rate summed for both surfaces of a wafer during acidic etching is adjusted to be 0.2 μm/sec or higher.