Plasma etching system

A plasma etching system, comprising:

• a process chamber enclosing a plasma;
• means for evacuating said process chamber;
• a chuck electrode for supporting a substrate;
• a shower electrode for forming a plasma discharge circuit between said chuck electrode and said shower electrode;
• a power source for applying a plasma voltage between the chuck electrode and said shower electrode;
• and
• gas supply means for supplying a plasma-forming gas into the process chamber;
• wherein the shower electrode includes:
• a cathode plate facing a substrate on the chuck electrode;
• a cooling plate laminated on said cathode plate to cool the cathode plate;
• a number of gas inlet holes formed in said cooling plate for introducing said gas from said gas supply means;
• a number of small holes formed in the cathode plate to communicate with said gas inlet holes, each of said small holes having an open end facing the chuck electrode being smaller in diameter than the gas inlet holes, and having a stepped portion in a region where said small hole communicates with the gas inlet hole;
• and
• control means for controlling the gas supply means such that said gas flows through the stepped portion between the small hole and the gas inlet hole at a mass flow rate of at least 620 kg/m.sup.2 /hour, thereby preventing a component of said gas from being deposited on the stepped portion.