Patent ID: 8703002

Claim:
A plasma etching method for performing an etching process on a target object by generating a plasma of a processing gas in a processing space of a plasma etching apparatus that includes an evacuable processing chamber, a first electrode for mounting thereon the target object in the processing chamber, a second electrode facing the first electrode in parallel in the processing chamber and having a ground potential, a processing gas supply unit for supplying processing gas, including O 2 gas, to the processing space between the first electrode and the second electrode, and a RF power supply unit for applying to the first electrode RF power having a frequency greater than or equal to 30 MHz, the method comprising: etching a target object that includes a polysilicon film formed on a gate oxide film by repeating a cycle that alternates between a first phase and a second phase, wherein, during the first phase, RF power is applied to the first electrode with a first amplitude that generates a plasma from the processing gas and, during the second phase, the RF power is applied to the first electrode with a second amplitude that generates substantially no plasma, wherein the length of the first phase is about 2 to 50 μsec and the length of the second phase is greater than or equal to about 2 μsec, and wherein the length of the cycle is about 4 to 200 μsec.