Dither-free adaptive robust dose control method for photolithography

摘要

A method and apparatus for controlling the dose of radiation produced by a laser light source is disclosed. In one embodiment, the dose controller receives a measure of the expected output energy or the deviation of the output energy from the "energy sigma", and a standard deviation of the error of the dose accepted by the article being processed from the desired dose. The ratio of the energy sigma to the standard deviation of the dose error is calculated, and the laser controller is based on the ratio calculated to adjust the voltage determined by the controller and consequently to adjust the output energy for the article and thus the dose. Adjust the controller gain. This is an improvement over the prior art where the controller gain is adjusted based on sending a voltage dither to the laser and associating it with the response of the energy of only one frequency.