Cleaning method

1. A method for cleaning a microwave plasma processing apparatus which has a processing container and a microwave radiation part, and which has a window part provided at a position where the microwave radiation part is disposed in the processing container, the method comprising:

a cleaning step of adjusting an internal pressure of the processing container, based on a correlation between the internal pressure and a plasma diffusion distance of plasma generated by the microwave radiation part, to a pressure corresponding to the plasma diffusion distance for a plasma region to reach a cleaning target part, among parts within the processing container including a wall surface of the processing container, the microwave radiation part, and the window part, while supplying a cleaning gas, and performing a cleaning process using plasma of the cleaning gas,

wherein the cleaning step comprises:

a first step of adjusting the internal pressure to a first pressure, which corresponds to a first plasma diffusion distance for the plasma region to reach a first cleaning target part, and performing the cleaning process; and

a second step of adjusting the internal pressure to a second pressure, which corresponds to a second plasma diffusion distance for the plasma region to reach a second cleaning target part having a different size than the first cleaning target part, and is different from the first pressure, and performing the cleaning process.

2. The method of claim 1 , wherein the cleaning process is performed by performing the first step and the second step in this order, and

the second pressure is lower than the first pressure.

3. The method of claim 2 , wherein a cleaning time of the first step is longer than a cleaning time of the second step.

4. The method of claim 1 , wherein the first step and the second step are repeated a predetermined number of times.

5. The method of claim 1 , wherein the cleaning step further comprises:

a third step of adjusting the internal pressure to a third pressure, which corresponds to a third plasma diffusion distance for the plasma region to reach a third cleaning target part that is different from the first cleaning target part and the second cleaning target part, and is different from the first pressure and the second pressure, and performing the cleaning process.

6. The method of claim 5 , wherein the cleaning process is performed by performing the first step, the second step, and the third step in this order, and

the third pressure is lower than the second pressure, and the second pressure is lower than the first pressure.

7. The method of claim 5 , wherein a cleaning time of the third step is longer than the cleaning time of the first step, and

the cleaning time of the first step is longer than the cleaning time of the second step.

8. The method of claim 5 , wherein the first step, the second step, and the third step are repeated a predetermined number of times.

9. The method of claim 1 , wherein the pressure corresponding to the plasma diffusion distance for the plasma region to reach the cleaning target part is adjusted to another pressure corresponding to a diameter of the plasma region that corresponds to a size of the cleaning target part.

10. The method of claim 1 , wherein the pressure corresponding to the cleaning target part is in a range of 10 Pa to 100 Pa.

11. The method of claim 1 , wherein a pre-coating film is formed after the cleaning step.

12. The method of claim 1 , wherein the parts within the processing container include a plurality of gas holes arranged in an annular shape within the window part and outside the microwave radiation part.