Patent ID: 7482102
Filing Date: 2009-01-27
Classification: B64D,G03F

Abstract:
1. A photomask having a monitoring pattern configured to obtain information required for adjusting an optical system of a projection lithography tool, the monitoring pattern comprising: a mask substrate; and a first asymmetrical diffraction grating delineated on the mask substrate, configured to generate a positive first order diffracted light and a negative first order diffracted light in different diffraction efficiencies, the first asymmetrical diffraction grating including: wherein a phase difference between the light transmitting through the first probing-phase shifters and the light not transmitting through the first probing-phase shifters is an integer multiple of a value larger than zero degrees and lower than 180 degrees, and a width of the first exit face measured perpendicular to the longitudinal direction is 1/R times an interval between the first probing-phase shifters, where R is an attenuation constant of the light leaving from the first exit face, after the light propagates through each of the first probing-phase shifters.