Patent ID: 8906193

Claim:
A supply gas supplying method using an etching gas supply unit for supplying at least first etching gases and a second etching gas to a processing chamber of a plasma etching apparatus, the plasma etching apparatus including a shower head disposed at an upper portion of the processing chamber and a susceptor disposed below the shower head to face the shower head in parallel, the shower head including a plurality of buffer spaces, the etching gas supply unit includes, a mixing line to mix the first etching gases to make a gaseous mixture, a multiplicity of branch lines to branch the gaseous mixture and supply the branched gaseous mixtures to the buffer spaces, a pressure control unit provided at each of the branch lines to adjust gas flow rates of the branched gaseous mixtures in the branch lines, and a second etching gas supply line to supply the second etching gas to at least one of the branch lines to which the second etching gas supply line is connected, a pressure ratio controller that controls a pressure ratio of gaseous mixtures in the multiplicity of the branch lines, the method comprising the following sequential steps of: supplying the gaseous mixture of the first etching gases to the branch lines via the mixing line; controlling the pressure ratio of the branched gaseous mixtures to be a specified pressure ratio by adjusting the pressure control units provided at the branch lines such that opening degrees of respective valves in the pressure control units are fixed under a condition in which the second etching gas is not supplied to branch line and, then fixing the opening degrees of the valves; supplying the second etching gas at a specified flow rate to said at least one of the branch lines to which the second etching gas supply line is connected thereby changing the pressure ratio between the pressures in the branch lines, while the opening degrees of the valves remained fixed; and injecting the first etching gases and the second etching gas through the buffer spaces toward the susceptor downwardly.