Plasma etching apparatus, plasma etching method and storage medium

1. A plasma etching method for forming a hole in an etching target film by using a plasma processing apparatus, which includes a vacuum evacuable processing chamber accommodating an object to be processed, a lower electrode disposed in the processing chamber and serving as a mounting table on which the object is mounted, an upper electrode disposed in the processing chamber to face the lower electrode, a processing gas supply unit for supplying a processing gas into the processing chamber, an RF power supply for applying an RF power for plasma generation to at least one of the upper electrode or the lower electrode, and a DC power supply for applying a minus DC voltage to the upper electrode, the method comprising:

alternately repeating a first process and a second process, wherein in the first process a plasma is generated in the processing chamber by turning on the RF power supply and the minus DC voltage is applied to the upper electrode from the DC power supply, and in the second process the RF power supply is turned off and the minus DC voltage is applied to the upper electrode from the DC power supply,

wherein, during the second process, a plasma sheath remains formed on the lower electrode by plasma generated in the first process, and wherein the method further includes reducing a thickness of the plasma sheath during the second process, and

wherein an etching process is performed by positive ions in the plasma during the first process and negative ions are produced and supplied into the hole by the DC voltage to neutralize positive ions in the hole during the second process, thereby suppressing bending of travel direction of the positive ions in the hole during the etching process.

2. The plasma etching method of claim 1 , wherein the plasma etching apparatus further includes a biasing RF power supply for applying additional RF power for bias application to the lower electrode, and

wherein an output of the biasing RF power supply is changed in synchronization with the on/off operation of the RF power supply, and the biasing RF power supply is turned off or the output of the biasing RF power supply is reduced for a specific period during the second process.

3. The plasma etching method of claim 2 , wherein the biasing RF power supply is turned off or the output is reduced for a specific period while the plasma is generated by turning on the RF power supply.

4. The plasma etching method of claim 3 , wherein the minus DC voltage is applied continuously to the upper electrode from the DC power supply while the first process and the second process are alternately repeated.

5. The plasma etching method of claim 2 , wherein the biasing RF power supply is turned off or the output of the biasing RF power supply is reduced for the specific period during the first process.

6. The plasma etching method of claim 5 , wherein the minus DC voltage is applied continuously to the upper electrode from the DC power supply while the first process and the second process are alternately repeated.

7. The plasma etching method of claim 2 , wherein the minus DC voltage is applied continuously to the upper electrode from the DC power supply while the first process and the second process are alternately repeated.

8. The plasma etching method of claim 1 , wherein a duration of a cycle of the second process ranges from 10 μsec to 50 μsec.

9. The plasma etching method of claim 1 , wherein the first process and the second process are repeated in a pulse shape.

10. The plasma etching method of claim 1 , wherein the etching target film of the object is an insulating film.

11. The plasma etching method of claim 1 , wherein the minus DC voltage is applied continuously to the upper electrode from the DC power supply while the first process and the second process are alternately repeated.

12. A plasma etching method for forming a hole in an etching target film by using a plasma processing apparatus, which includes a vacuum evacuable processing chamber accommodating an object to be processed, a lower electrode disposed in the processing chamber and serving as a mounting table on which the object is mounted, an upper electrode disposed in the processing chamber to face the lower electrode, a processing gas supply unit for supplying a processing gas into the processing chamber, an RF power supply for applying an RF power for plasma generation to at least one of the upper electrode or the lower electrode, and a DC power supply for applying a minus DC voltage to the upper electrode, the method comprising:

a first step of continuously supplying the RF power from the RF power supply to generate a plasma in the processing chamber and applying the minus DC voltage to the upper electrode from the DC power supply;

a second step of alternately repeating a first process and a second process, wherein in the first process a plasma is generated in the processing chamber by turning on the RF power supply and the minus DC voltage is applied to the upper electrode from the DC power supply, and in the second process the RF power supply is turned off and the minus DC voltage is applied to the upper electrode from the DC power supply,

wherein, during the second process, a plasma sheath remains formed on the lower electrode by plasma generated in the first process, and wherein the method further includes reducing a thickness of the plasma sheath during the second process, and

wherein, in the second step, an etching process is performed by positive ions in the plasma during the first process and negative ions are produced and supplied into the hole by the DC voltage to neutralize positive ions in the hole during the second process, thereby suppressing bending of travel direction of the positive ions in the hole during the etching process.

13. The plasma etching method of claim 12 , wherein the plasma etching apparatus further includes a biasing RF power supply for applying additional RF power for bias application to the lower electrode,

wherein in the first step, a bias is continuously applied at a first output from the biasing RF power supply, and

wherein, in the second step, an output of the biasing RF power supply is changed in synchronization with the on/off operation of the RF power supply, and the biasing RF power supply is turned off or has a second output lower than the first output for a specific period during the second process.

14. The plasma etching method of claim 13 , wherein in the second step, the biasing RF power supply is turned off or has the second output lower than the first output for the specific period while the plasma is generated by turning on the RF power supply.

15. The plasma etching method of claim 14 , wherein the minus DC voltage is applied continuously to the upper electrode from the DC power supply while the first process and the second process are alternately repeated.

16. The plasma etching method of claim 13 , wherein the biasing RF power supply is turned off or the second output of the biasing RF power supply is reduced for the specific period during the first process.

17. The plasma etching method of claim 16 , wherein the minus DC voltage is applied continuously to the upper electrode from the DC power supply while the first process and the second process are alternately repeated.

18. The plasma etching method of claim 13 , wherein the minus DC voltage is applied continuously to the upper electrode from the DC power supply while the first process and the second process are alternately repeated.

19. The plasma etching method of claim 12 , wherein the minus DC voltage is applied continuously to the upper electrode from the DC power supply while the first process and the second process are alternately repeated.