Patent ID: 7943285

Claim:
A pattern formation method, comprising the steps of: (a) forming an underlayer film on a film to be etched; (b) forming an intermediate layer film on the underlayer film; (c) forming a first resist film on the intermediate layer film and performing exposure and development of the first resist film via a first photomask having a first pattern to form a first resist pattern; (d) etching the intermediate layer film using the first resist pattern as a mask to transfer the first resist pattern into the intermediate layer so as to form a first intermediate layer pattern which has the first pattern; (e) removing the first resist pattern; (f) after step (e), forming a second resist film on the underlayer film and the first intermediate layer pattern and performing exposure and development of the second resist film via a second photomask having a second pattern to form a second resist pattern; (g) etching the first intermediate layer pattern using the second resist pattern as a mask to transfer the second resist pattern into the first intermediate layer pattern so as to form a second intermediate layer pattern which has a composite pattern of the first and the second pattern; (h) removing the second resist pattern; and (i) after step (h), etching the underlayer film using the second intermediate layer pattern as a mask to form an underlayer pattern which has the composite pattern, wherein the first resist film and the second resist film are chemically amplified resist films, at least one of an additive which improves sensitivity of the resist and an additive which improves alkaline solubility of exposed part of the resist is contained in a greater amount in the second resist film than in the first resist film, the underlayer pattern is used as a mask for dry etching the film to be etched, and in the step (f), the second resist film is formed on a surface portion of the underlayer film which is opposite to a surface in contact with the film to be etched and on a surface portion of the first intermediate layer pattern which is opposite to a surface in contact with the underlayer film.