Patent ID: 8466071

Claim:
A method for etching a single wafer, wherein a single thin disk-like silicon wafer sliced from a silicon single crystal ingot is spun to etch a front surface of the wafer with etching solutions supplied thereto, comprising the steps of: disposing a plurality of etching solution supply nozzles above and opposite to the front surface of the wafer at different portions in the radial direction of the wafer; and changing supply flow rates of etching solutions from the plurality of etching solution supply nozzles, wherein the plurality of etching solution supply nozzles includes a first supply nozzle that supplies a first etching solution to the center of the front surface of the wafer and a second supply nozzle that supplies a second etching solution to the periphery of the front surface of the wafer, wherein the supply flow rate of the first etching solution supplied from the first supply nozzle to the center of the front surface of the wafer is higher than the supply flow rate of the second etching solution supplied from the second supply nozzle to the periphery of the front surface of the wafer, wherein the first etching solution has a weight ratio (% by weight) of fluorinated acid (HF):nitric acid (HNO 3 ):phosphoric acid (H 3 PO 4 ):water (H 2 O)=(5 to 20):(5 to 40):(30 to 40):remainder after mixing with an aqueous acid solution, and the second etching solution has a weight ratio (% by weight) of fluorinated acid (HF):nitric acid (HNO 3 ):phosphoric acid (H 3 PO 4 ):water (H 2 O)=(0.5 to 10):(20 to 50):(30 to 40):remainder after mixing with an aqueous acid solution, and wherein the first etching solution has an etching rate of 0.2 to 3 μm/sec at 30° C., and the second etching solution has an etching rate smaller than the etching rate of the first etching solution, and is 0.01 to 1 μm /sec, at 30° C.