Abstract
A method includes applying a first voltage to a source of a first transistor of a detector unit of a semiconductor detector in a test wafer and applying a second voltage to a gate of the first transistor and a drain of a second transistor of the detector unit. The first transistor is coupled to the second transistor in series, and the first voltage is higher than the second voltage. A pre-exposure reading operation is performed to the detector unit. Light of an exposure apparatus is illuminated to a gate of the second transistor after applying the first and second voltages. A post-exposure reading operation is performed to the detector unit. Data of the pre-exposure reading operation is compared with the post-exposure reading operation. An intensity of the light is adjusted based on the compared data of the pre-exposure reading operation and the post-exposure reading operation.