The mask containing the pattern to be transferred to the wafer is now placed in the mask holder. This mask resembles a classroom viewgraph. Where it is transparent, light will reach the photoresist on the wafer below. Where it has a black pattern, light will be blocked.
The mask holder is lowered into position. The wafer holder is now gently raised so that the wafer just contacts the bottom of the mask.
Finally, the microscope is rotated around above the mask and wafer. A window-in-window view port shows what you would see through the microscope.
