Improving exposure system´s compatibility by changing the lamp calibration method

In semiconductor manufacturing, it is essential that the energy used to expose photoresist match as closely as possible from machine to machine to produce the same critical dimension in the resist. It is shown that the exposure energy difference from machine to machine for high-resolution exposures is reduced by calibrating all the machines with a high-resolution aperture instead of the usual low-resolution aperture. This setup procedure also minimizes the uniformity of the exposure across the wafer. Exposure energy deviations from machine to machine and uniformity across the wafer will degrade on low-resolution apertures; however, this does not cause problems on the manufacturing line because larger geometries processed on low-resolution apertures are more tolerant of energy variations. An improvement to process capability is also shown, along with a 50% reduction in exposure-related rejected at the postdevelop inspection