Plasma processing apparatus
Provided is a plasma processing apparatus including a processing chamber which is disposed in a vacuum vessel and able to be decompressed, a sample stage on a top surface of which a wafer to be processed is mounted, an opening which is configured to supply a heat-transfer gas to a gap between the wafer and the top surface of the sample stage, a regulator which regulates a flow rate of the heat-transfer gas, and a controller which regulates an operation of the regulator based on a pressure of the gap detected using an amount of the heat-transfer gas leaking from the regulator to the processing chamber through the gap while the wafer is mounted on the sample stage and an amount of the heat-transfer gas supplied from the opening to the processing chamber while the wafer is not mounted on the sample stage.
1. A plasma processing method comprising steps of:
locating and holding a wafer to be processed on a top surface of a sample stage disposed in a processing chamber an inside of which is decompressed;
supplying a heat-transfer gas into a gap between the wafer and the top surface of the sample stage; and
generating a plasma in a space above the sample stage inside the processing chamber and starting processing of the wafer,
wherein the heat-transfer gas which is supplied from a gas source flows through a supply path disposed inside the sample stage into the gap via an opening which is arranged on the top surface of the sample stage, and
wherein a supply amount of the heat-transfer gas is adjusted to maintain a pressure of the heat-transfer gas in the gap in an allowable range based upon a pressure value of the heat-transfer gas which is detected at a certain position on the supply path and a value of a pressure drop of the heat-transfer gas between the certain position of the supply path and the gap between the wafer and the top surface of the sample stage via the supply path.
2. The plasma processing method according to claim 1 , wherein the pressure drop of the heat-transfer gas via the supply path is determined using a value of a pressure change of the heat-transfer gas in the supply path which is detected in advance when an amount of the heat-transfer gas is supplied through the supply path into the processing chamber via the opening on the top surface of the sample stage while the wafer is not located on the top surface of the sample stage.
3. The plasma processing method according claim 1 , wherein the pressure drop of the heat-transfer gas via the supply path is determined using a value of a pressure change of the heat-transfer gas in the supply path which is detected in advance when an amount of the heat-transfer gas is supplied through the supply path into the processing chamber via the opening on the top surface of the sample stage while the processing chamber is decompressed in high vacuum exhaust and the wafer is not located on the top surface of the sample stage.
4. The plasma processing method according to claim 2 , wherein the value of the pressure change of the heat-transfer gas in the supply path is detected after a prescribed number of wafers is processed.
5. The plasma processing method according to claim 3 , the value of the pressure change of the heat-transfer gas in the supply path is detected after a prescribed number of wafers is processed.