To provide a method for forming an optical multilayer film, which prevents the warping of a substrate even when the optical multilayer film is formed on only one surface of a thin substrate, imparts a longly stable optical property to the optical multilayer film, and reduces a production cost.
The method for forming the optical multilayer film by alternately layering a layer with a low refractive index and a layer with high refractive index layer which have different refractive indexes on the substrate 2 mounted on a substrate-holding member 14 which is arranged in a vacuum chamber 11 comprises the steps of: when forming at least the layer with high refractive index, introducing a process gas into the vacuum chamber 11 while controlling an amount of an introduced process gas so that the amount of vacuum for forming the film in the vacuum chamber 11 is 0.06 Pa or more but less than 0.15 Pa; and generating plasma from a plasma gun 21 installed so as to face the substrate 2.
Masatake Shiga
Masakazu Aoyama
Suzuki Mitsuyoshi
Tadao Takashiba
Hiroshi Masui
Kiyoshi Kato