Patent ID: 9495740
Filing Date: 2016-11-15
CPC Classification: G06T,H04N

Claim Text:
1. A mask inspection apparatus comprising: a stage control circuit configured to drive a stage holding an inspection target mask, in which a pattern is formed, or a calibration mask different from the inspection target mask; a light irradiation device configured to irradiate light on the inspection target mask or the calibration mask; an image sensor configured to detect a light quantity signal of transmitted light or reflected light of the inspection target mask or the calibration mask at a plurality of pixels; a sensor amplifier configured to amplify an output of each of the pixels of the image sensor according to a gain and an offset for each pixel of the image sensor, wherein the sensor amplifier sets the gain and the offset based on the light quantity signal of transmitted light or reflected light of the calibration mask; a gain resetting circuit configured to reset the gain according to a difference between a first apparatus state when the image sensor detects the light quantity signal of transmitted light or reflected light of the calibration mask, and a second apparatus state when the image sensor detects the light quantity signal of transmitted light or reflected light of the inspection target mask; the sensor amplifier is further configured to generate an optical image of the inspection target mask based on the reset gain and the offset; a reference image generation circuit configured to generate a reference image serving as a standard image for the optical image; and a comparison circuit configured to inspect a defect of the pattern of the inspection target mask by comparing the optical image with the reference image.