An aberration control of projection optics for multi-patterning lithography

In order to realize further improvement of productivity of semiconductor manufacturing, higher throughput and better imaging performance are required for the exposure tool. Therefore, aberration control of the projection lens is becoming more and more important not only for cool status performance but also heating status. In this paper, we show the improvements of cool status lens aberration, including scalar wavefront performance and polarization aberration performance. We also discuss various techniques for controlling thermal aberrations including reduction of heat in the lens, simulation, compensating knob, and adjusting method with actual imaging performance data during heating and cooling.