Method for etching oxide semiconductor film and plasma processing apparatus

1. A method for etching an oxide semiconductor film, the method comprising:

providing a substrate including an oxide semiconductor film disposed below a patterned silicon oxide mask, the oxide semiconductor film containing indium (In), gallium (Ga), and zinc (Zn);

supplying a processing gas containing a bromine (Br)-containing gas or an iodine (I)-containing gas;

break-through etching an altered layer on the oxide semiconductor film by plasma generated from a break-through gas using microwaves before or after supplying the processing gas; and

etching the oxide semiconductor film by plasma generated from the processing gas using microwaves after break-through etching the altered layer,

wherein a first microwave power for generating the microwaves in the break-through etching the altered laver is lower than a second microwave power for generating the microwaves in the etching the oxide semiconductor film.

2. The method according to claim 1 , wherein the processing gas contains neither a chlorine-containing gas nor a fluorine-containing gas.

3. The method according to claim 2 , further comprising:

controlling a temperature of the substrate within a range of 60° C. to 200° C.

4. The method according to claim 2 , further comprising:

controlling a temperature of the substrate within a range of 80° C. to 200° C.

5. The method according to claim 4 , wherein an oxygen-containing gas is added to the processing gas.

6. The method according to claim 5 , wherein the oxygen-containing gas is at least one selected from the group consisting of CO gas, CO 2 gas, O 2 gas, O 3 gas), COS gas, and H 2 O gas.

7. The method according to claim 6 , further comprising:

treating the oxide semiconductor film with plasma generated from an oxygen gas after the etching; and

cleaning the oxide semiconductor film with pure water after the treating.

8. The method according to claim 1 , further comprising:

controlling a temperature of the substrate within a range of 60° C. to 200° C.

9. The method according to claim 8 , wherein, in the controlling the temperature of the substrate, the temperature is controlled within a range of 80° C. to 200° C.

10. The method according to claim 1 , wherein an oxygen-containing gas is added to the processing gas.

11. The method according to claim 10 , wherein the oxygen-containing gas is at least one selected from the group consisting of CO gas, CO 2 gas, O 2 gas, O 3 gas), COS gas, and H 2 O gas.

12. The method according to claim 1 , further comprising:

after the etching, treating the oxide semiconductor film with oxygen gas plasma; and

after the treating, cleaning the oxide semiconductor film with pure water.