| 摘要 |
PURPOSE:To eliminate positioning errors in focusing, by projecting a plurality of light beams having different wave lengths at specified angles from the side of the surface of a sample, detecting the respective positions, and performing computation. CONSTITUTION:A light path L10, which is inputted at an incident angle theta1 is divided into a light path L11, which is reflected by the surface of a resist film, and a light path, which is transmitted through a resist film 11 and reflected by the surface of an SiO2 film of a semiconductor wafer 4 (the bottom surface of the resist film). Refractive indexes are different in the resist film in response to the wavelengths of light. Therefore, the light having the wavelength of lambda is refracted at a refractive index theta, passes through a light path L12, and is reflected. The light having the wavelength lambda' is refracted at a refractive index theta', passes through a light path L13, and is reflected. The positions of the reflected light beams, which are actually detected, are based on the combined light paths of the light paths L11, L12 and L13. In this way, the position of the light path L11 from the surface of the resist film, which is not affected by the reflection intensity can be accurately corrected and obtained. |
