Plasma etching method and plasma etching apparatus

1. A plasma etching method for plasma-etching an object including an etching target film and a patterned mask including a first opening, the plasma etching method comprising:

a first step of plasma-etching the etching target film using the mask to form a second opening in the etching target film; and

a second step of depositing a silicon-containing film using plasma of a silicon-containing gas on at least a part of a side wall of the etching target film etched by the first step, wherein

as a result of the first step, a width of at least a part of the second opening of the etching target film becomes greater than a width of the first opening of the mask; and

in the second step, the silicon-containing film is deposited on at least the part of the side wall such that the width of the entire second opening of the etching target film becomes closer to the width of the first opening of the mask.

2. The plasma etching method as claimed in claim 1 , wherein the silicon-containing gas includes

one of silicon tetrachloride and silicon tetrafluoride, and

a reducing gas.

3. The plasma etching method as claimed in claim 1 , wherein

the object includes an amorphous carbon layer film and a patterned inorganic film stacked on the amorphous carbon layer film; and

the first step includes etching the amorphous carbon layer film with plasma of a process gas including an oxygen gas and a carbonyl sulfide gas by using the mask including the inorganic film.

4. The plasma etching method as claimed in claim 3 , wherein

the object also includes an oxide film formed on an opposite side of the amorphous carbon layer film from the inorganic film; and

the first step and the second step are repeated to expose the oxide film.

5. The plasma etching method as claimed in claim 4 , further comprising:

a third step of plasma-etching the oxide film using a mask including the amorphous carbon layer film; and

a fourth step of depositing a silicon-containing film using plasma of a silicon-containing gas on at least a part of a side wall of the oxide film etched by the third step.

6. The plasma etching method as claimed in claim 5 , wherein in the third step, the oxide film is plasma-etched using plasma of a process gas including a fluorocarbon gas.

7. The plasma etching method as claimed in claim 5 , wherein the third step and the fourth step are repeated.

8. The plasma etching method as claimed in claim 3 ,

wherein the object further includes an antireflection film and a patterned resist film that are stacked on an opposite side of the inorganic film from the amorphous carbon layer film; and

wherein the method further comprises etching, before the first step, the antireflection film and the inorganic film with plasma of a process gas including a fluorocarbon gas by using the resist film as a mask.