Patent ID: 7680563

Claim:
A pressure control device for a plasma processing apparatus comprising: gas supply means which supplies processing gas to a low pressure processing chamber; plasma generating means which supplies electromagnetic energy to the processing gas supplied to the low pressure processing chamber, and which generates plasma; exhaust means which exhausts gas in the low pressure processing chamber; pressure measuring means which measures gas pressure in the low pressure processing chamber; exhaust speed adjusting means which adjusts an exhaust speed of gas to be exhausted by said exhaust means; and an arithmetic and control unit which performs a Proportional-Integral-Derivative (PID) control calculation to calculate an operation amount of an exhaust speed of gas so as to make the gas pressure measured by said pressure measuring means equal to a target pressure, and which controls said exhaust speed adjusting means to adjust an opening of an exhaust valve so as to make a change of the exhaust speed equal to said operation amount of the exhaust speed, wherein said PID control calculation is made for each control cycle based on the exhaust speed of gas and the target pressure, and an integral gain in said PID control calculation is a function which has a positive correlation with the exhaust speed of gas and a negative correlation with the target pressure.