Etching method and plasma processing apparatus

1 . An etching method comprising:

preparing a substrate including a first region containing silicon and nitrogen, and a second region containing silicon and oxygen; and

etching the second region while forming a tungsten-containing protective layer on the first region, by exposing the first and second regions to a plasma generated from a processing gas containing carbon, fluorine, and tungsten, wherein

the first region has a recess, and

the second region is embedded in the recess.

2 . The etching method according to claim 1 , wherein in the etching, the tungsten-containing protective layer remains on the first region after the second region is removed.

3 . The etching method according to claim 1 , wherein the processing gas includes a gas containing carbon and fluorine, and a tungsten-containing gas.

4 . The etching method according to claim 3 , wherein the tungsten-containing gas includes tungsten hexafluoride gas.

5 . The etching method according to claim 3 , wherein the gas containing carbon and fluorine includes fluorocarbon gas.

6 . The etching method according to claim 1 , wherein the processing gas contains oxygen.

7 . The etching method according to claim 1 , wherein the etching is performed in a self-aligned contact process.

8 . The etching method according to claim 1 , wherein in the etching, a radio-frequency power and a bias power are supplied to a plasma processing apparatus in order to generate the plasma, and

the etching includes:

(a) depositing a tungsten-containing deposit on the first region by setting the radio-frequency power to a first power and setting the bias power to a second power;

(b) performing a transition of setting the radio-frequency power to a third power lower than the first power and setting the bias power to the second power; and

(c) etching the second region by setting the radio-frequency power to the third power and setting the bias power to a fourth power higher than the second power.

9 . The etching method according to claim 8 , wherein a cycle including (a) to (c) is repeated two or more times.

10 . An etching method comprising:

preparing a substrate including silicon nitride having an exposed upper surface and silicon oxide having an exposed upper surface;

exposing the silicon oxide and the silicon nitride to a plasma generated from a processing gas including tungsten hexafluoride gas, thereby forming a protective layer containing tungsten nitride on the silicon nitride; and

exposing the silicon oxide and the silicon nitride to the plasma generated from the processing gas including tungsten hexafluoride gas, thereby etching the silicon oxide to the silicon nitride, wherein

the silicon nitride has a recess, and

the silicon oxide is embedded in the recess.

11 . The etching method according to claim 10 , wherein the processing gas includes fluorocarbon gas.

12 . A plasma processing apparatus comprising:

a chamber;

a substrate support configured to support a substrate in a chamber;

a gas supply configured to supply a processing gas containing carbon, fluorine, and tungsten into the chamber;

a plasma generator configured to generate a plasma from the processing gas in the chamber; and

a controller, wherein

the controller is configured to control the gas supply and the plasma generator to perform a series of processes including:

preparing a substrate including a first region containing silicon and nitrogen, and a second region containing silicon and oxygen; and

etching the second region while forming a tungsten-containing protective layer on the first region, by exposing the first and second regions to a plasma generated from a processing gas containing carbon, fluorine, and tungsten,

the first region has a recess, and

the second region is embedded in the recess.

13 . The etching method according to claim 1 , wherein the tungsten-containing protective layer forms on an exposed upper surface of the first region.

14 . The etching method according to claim 1 , wherein the second region is not covered by the tungsten-containing protective layer.

15 . The etching method according to claim 10 , wherein the protective layer containing tungsten nitride is formed on the exposed upper surface of the silicon nitride.

16 . The etching method according to claim 10 , wherein the silicon oxide is not covered by the protective layer containing tungsten nitride.

17 . The plasma processing apparatus according to claim 12 , wherein the tungsten-containing protective layer forms on an exposed upper surface of the first region.

18 . The plasma processing apparatus according to claim 12 , wherein the second region is not covered by the tungsten-containing protective layer.