Wavelength control system for pulse-by-pulse wavelength target tracking in DUV light sources

摘要

Wafer positioning errors in stepper scanners contribute to imaging defects. By changing the wavelength of the light generated by the light source, a wafer position error in the Z direction can be compensated. The real-time z-position of the wafer is determined, and changes in wavelength targets to offset this error are communicated to the light source. The light source, in addition to receiving the newly specified laser wavelength target for the subsequent laser pulse burst, pulse-by-pulse for the subsequent pulse in the current pulse burst, in feed-forward operation, and with the existing feedback operation. In the combined embodiment, this change in wavelength target is used. [Selection diagram] Fig. 4