Dither-free Adaptive Robust Dose Control Method for Photolithography

摘要

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