Alignment device

Abstract

Abstract PURPOSE:To isolate an unnecessary diffracted light, to improve S/N ratio of a detection signal and to accurately align a reference grating by selectively passing a diffracted light from the lattice by an illumination optical system, and irradiating it from a specific direction specified by the numerical aperture of the optical system to the reference lattice to be aligned. CONSTITUTION:Laser lights of two wavelengths perpendicularly crossing each other are incident from a Zeeman laser 11 to a reference grating 12, and +1,-2 and 0-th diffracted lights from reference diffraction gratings are irradiated to a both-side telecentric lens 14. The lights are radiated through the lens 14, a diffraction grating 15 on a mask and a photomask 16 to a wafer 18. A specific diffracted light from the grating 12 is selected by the lens 14, and interference fringes are generated on second and third gratings 15 on the mask 16 and wafer 18. The lights from the second and third gratings are combined, and relative positions between the fringes and the second, third gratings are detected by photodetectors 35, 36 as light beat signals.

Inventors

• 👤 Kazuhiro Yamashita
• 👤 Noboru Nomura
• 👤 Keisuke Koga
• 👤 Shinichiro Aoki
• 👤 Takeo Sato
• 👤 Katsumasa Yamaguchi

Bibliographic Details