Nikon Corporation

Tsuyoshi Murata

Hitoshi Ishizawa

Issei Tanaka

Shunsuke Niisaka

An MgFoptical thin film is formed on an optical surface of a base material. The MgFoptical thin film includes MgFparticles and an amorphous silicon oxide-based binder which exists on the surfaces of the MgFparticles and between the MgFparticles. Owing to this amorphous silicon oxide-based binder, the optical thin film can have high mechanical strength and high adhesion to the base material, while having excellent environment resistance and a lower refractive index.

Optical system having optical thin film including amorphous silicon oxide-based binder

An anti-reflection coating is formed on an optical surface of an optical member for reducing the amount of light rays reflected from the optical surface. For light rays in a wavelength range from 400 nm to 700 nm, the anti-reflection coating has a reflectance of 0.5% or less if the light rays are incident on the optical surface at angles within a range from 0 to 25 degrees, and it has a reflectance of 3.5% or less if the light rays are incident at angles within a range from above 25 degrees to 60 degrees.

Anti-reflection coating, and optical element and optical system with anti-reflection coating

A method for forming an optical thin film on a substrate comprises the steps of preparing a sol solution containing minute particles for an optical element dispersed in a dispersion medium, putting the prepared sol solution in a tightly closable vessel to heat and pressurize the sol solution, and then applying the heated and pressurized sol solution onto an optical substrate. The obtained thin film has a refractive index of 1.16 with respect to a light beam having a wavelength of 193 nm, in which the transmission loss is not more than 0.5%. An optical lens including the optical thin film formed on the surface, and an exposure apparatus including the lens provided for a projection optical system or an illumination system are provided.

Method for forming optical thin film and optical element provided with optical thin film

An optical element ( ) of the present invention is provided with an optical substrate ( ) and a multilayered optical thin film ( ) formed on the optical substrate ( ). An MgF layer ( ) of the multilayered optical thin film has a refractive index of 1.10 to 1.35, especially 1.15 to 1.25 with respect to a vacuum ultraviolet light beam having a wavelength of not more than 250 nm. Therefore, when the optical element ( ) is used together with an excimer laser light beam having a wavelength of, for example, 248 nm (KrF), 193 nm (ArF), or 157 nm (F ), excellent optical characteristics are exhibited concerning, for example, the reflectance (anti-reflection), the polarization characteristics, and the dependency on the angle of incidence. The MgF layer ( ) can be produced in accordance with the sol-gel method. The optical element is preferably used for a projection lens of an exposure apparatus which uses the excimer laser light beam as a light source.

Growing community of inventors

Kamakura, Japan

Tsuyoshi Murata