Hole pattern forming method and semiconductor device manufacturing method

1. A hole pattern forming method that forms a fine hole pattern in a work target layer that is formed on a semiconductor substrate, comprising:

forming a three-layer structure by laminating a carbon film layer, an intermediate mask layer, and a photoresist layer in that order on the work target layer;

after patterning a hole pattern in the photoresist layer, patterning the hole pattern in the intermediate mask layer with the patterned photoresist layer serving as a mask;

forming a sidewall oxide film on exposed portions of the photoresist layer, the intermediate mask layer, and the carbon film layer;

forming a sidewall portion that includes the sidewall oxide film on inner wall surfaces of the hole pattern by etching back the sidewall oxide film; and

after patterning a fine hole pattern in the carbon film layer with the sidewall portion and the intermediate mask layer serving as a mask, patterning the fine hole pattern in the work target layer with the patterned carbon film layer serving as a mask.

2. The hole pattern forming method according to claim 1 , wherein the sidewall oxide film is formed in an atmosphere below a softening temperature of the photoresist layer.

3. The hole pattern forming method according to claim 1 , wherein the sidewall oxide film is formed using an ALD method.

4. The hole pattern forming method according to claim 1 , wherein the carbon film layer includes amorphous carbon.

5. The hole pattern forming method according to claim 1 , wherein the sidewall oxide film is an oxide film that includes a cross-linked silica.

6. A semiconductor device manufacturing method comprising manufacturing a semiconductor device using the hole pattern forming method according to claim 1 .