Thermal control in wafer scanners using high complexity models

The performance of ASML’s wafer scanners is mainly measured in terms of speed and resolution. The company is therefore aiming at reducing feature sizes on chips, while at the same time increasing machine throughput. As a result error margins become smaller, while both the power and bandwidth of signals increase.

Thermally induced deformations of various components are a significant source of errors in wafer scanners. In practice, low complexity models are used for real time control purposes, because high complexity models are generally not fast enough. These low complexity models have a limited accuracy, which therefore limits the system performance. For this reason the use of high resolution, multiphysics models for control purposes is proposed.