Etching method and plasma processing apparatus

1. An etching method comprising,

(a) preparing a substrate including a silicon-containing film that includes a silicon oxide film and placed on a substrate support provided in a chamber;

(b) supplying a processing gas containing tungsten hexafluoride gas, a gas containing carbon and fluorine, and an oxygen-containing gas into the chamber; and

(c) generating plasma from the processing gas to etch the silicon-containing film, which includes:

applying a first negative DC voltage to the substrate support when a second negative DC voltage is not applied to an upper electrode provided above the substrate support; and applying the second negative DC voltage to the upper electrode provided above the substrate support when the first negative DC voltage is not applied to the substrate support.

2. The etching method according to claim 1 , wherein a pressure in the chamber in (c) is set to less than 1.333 Pa.

3. The etching method according to claim 1 , wherein a ratio of a flow rate of the tungsten hexafluoride gas in the processing gas to a flow rate of the processing gas is 5% by volume or less.

4. The etching method according to claim 1 , wherein the processing gas further contains nitrogen trifluoride gas.

5. The etching method according to claim 4 , wherein a ratio of a flow rate of the nitrogen trifluoride gas in the processing gas to a flow rate of the processing gas is larger than a ratio of a flow rate of the tungsten hexafluoride gas in the processing gas to the flow rate of the processing gas.

6. The etching method according to claim 1 , wherein the processing gas contains a fluorocarbon gas as the gas containing carbon and fluorine.

7. The etching method according to claim 6 , wherein the silicon-containing film further includes a silicon nitride film.

8. The etching method according to claim 7 , wherein, in (c), a tungsten-containing film is formed on a side wall formed on the silicon nitride film by the etching.

9. The etching method according to claim 6 , wherein the silicon-containing film further includes a polycrystalline silicon film.

10. The etching method according to claim 1 , wherein the silicon-containing film further includes a silicon nitride film, and

the processing gas contains a hydrofluorocarbon gas as the gas containing carbon and fluorine.

11. The etching method according to claim 1 , wherein the silicon-containing film includes a stacked film including the silicon oxide film and the silicon nitride film, and

step (c) includes:

etching the silicon nitride film in a state where the bias frequency is set to a first frequency the bias frequency being a reciprocal of a time interval in which the negative DC voltage is applied to the substrate support, and

etching the silicon oxide film in a state where the bias frequency is set to a second frequency larger than the first frequency.

12. The etching method according to claim 1 , wherein, in step (c), a temperature of the substrate support is set to 0° C. or higher and 120° C. or lower.

13. The etching method according to claim 1 , wherein, in step (c), an absolute value of the negative DC voltage applied to the substrate support is 1 kV or more and 20 kV or less.

14. The etching method according to claim 1 , wherein the substrate further includes an underlying region or an etching stop layer, and

the etching method further includes

(d) stopping the supply of the tungsten hexafluoride gas in the processing gas during a period including a time when the underlying region or the etching stop layer is exposed, and

(e) etching the silicon-containing film with plasma generated from a gas other than the tungsten hexafluoride gas contained in the processing gas.

15. An etching method comprising:

(a) preparing a substrate including a silicon-containing film including a silicon oxide film and placed on a substrate support provided in a chamber;

(b) supplying a processing gas containing tungsten hexafluoride gas, a gas containing carbon and fluorine, and an oxygen-containing gas into the chamber; and

(c) generating plasma from the processing gas to etch the silicon-containing film,

wherein step (c) includes

substituting a part of silicon atoms in the silicon-containing film with tungsten atoms on a bottom surface of a recess formed in the silicon-containing film by the etching, and

electrically biasing the substrate to remove the silicon-containing film in which a part of silicon atoms are substituted with tungsten atoms,

wherein, in the electrically biasing the substrate, a negative DC voltage having a duty ratio of 5% or more and 40% or less, is periodically applied to the substrate support in a state where a bias frequency, which is a reciprocal of a time interval in which the negative DC voltage is applied to the substrate support, is set to 100 kHz or more and 1 MHz or less.

16. The etching method according to claim 15 , wherein a pressure in the chamber in (c) is set to less than 1.333 Pa.

17. The etching method according to claim 15 , wherein a ratio of a flow rate of the tungsten hexafluoride gas in the processing gas to a flow rate of the processing gas is 5% by volume or less.

18. The etching method according to claim 15 , wherein the processing gas further contains nitrogen trifluoride gas.

19. The etching method according to claim 18 , wherein a ratio of a flow rate of the nitrogen trifluoride gas in the processing gas to a flow rate of the processing gas is larger than a ratio of a flow rate of the tungsten hexafluoride gas in the processing gas to the flow rate of the processing gas.

20. The etching method according to claim 15 , wherein the processing gas contains a fluorocarbon gas as the gas containing carbon and fluorine.

21. The etching method according to claim 20 , wherein the silicon-containing film further includes a silicon nitride film.

22. The etching method according to claim 20 , wherein the silicon-containing film further includes a polycrystalline silicon film.

23. The etching method according to claim 15 , wherein the silicon-containing film further includes a silicon nitride film, and

the processing gas contains a hydrofluorocarbon gas as the gas containing carbon and fluorine.

24. The etching method according to claim 23 , wherein, in (c), a tungsten-containing film is formed on a side wall formed on the silicon nitride film by the etching.

25. The etching method according to claim 15 , wherein the silicon-containing film includes a stacked film including the silicon oxide film and the silicon nitride film, and

step (c) includes:

etching the silicon nitride film in a state where the bias frequency is set to a first frequency the bias frequency being a reciprocal of a time interval in which the negative DC voltage is applied to the substrate support, and

etching the silicon oxide film in a state where the bias frequency is set to a second frequency larger than the first frequency.

26. The etching method according to claim 15 , wherein, in step (c), a temperature of the substrate support is set to 0° C. or higher and 120° C. or lower.

27. The etching method according to claim 15 , wherein, in step (c), an absolute value of the negative DC voltage applied to the substrate support is 1 kV or more and 20 kV or less.

28. The etching method according to claim 15 , wherein the substrate further includes an underlying region or an etching stop layer, and

the etching method further includes

(d) stopping the supply of the tungsten hexafluoride gas in the processing gas during a period including a time when the underlying region or the etching stop layer is exposed, and

(e) etching the silicon-containing film with plasma generated from a gas other than the tungsten hexafluoride gas contained in the processing gas.