Patent ID: 6968038
Filing Date: 2005-11-22
Classification: G01N,G02F,H01S,H05G

Abstract:
1. A point-diffraction interferometer for testing quality of an EUV (Extreme Ultraviolet) optical system like EUV lithography by use of a high-order harmonic X-ray, comprising: a high power femtosecond laser; a laser intensity controller for adjusting laser intensity and beam size of a femtosecond laser pulse generated by the high power femtosecond laser in order to reduce intensity of short wavelength harmonics with orders greater than a predetermined order; a gas-filled hollow tube target for focusing the femtosecond laser beam in order to generate a high-order harmonic X-ray beam; a gas pressure controller for adjusting the pressure of the target gas in order to reduce intensity of long wavelength harmonics with orders less than a predetermined order; an interferometer plate implemented by a thin film having a pinhole and arranged to be perpendicular to an incident path of a high-order harmonic X-ray beam to generate a diffracted beam forming a reference and a transmitted beam; and an X-ray detector disposed on the path of the reference and transmitted beams to detect an interference pattern generated through the interference of the reference and transmitted beams.