Run-to-run critical dimension and sidewall angle lithography control using the PROLITH simulator

We derive and investigate three different run-to-run (R2R) feedback controllers for the purpose of trying to minimize the detrimental effects of lithography process disturbances on critical resist profiles. Our controllers manipulate the dose and focus inputs and include Kalman filtering schemes that estimate the disturbances. The first controller adjusts the critical dimension (CD) and sidewall angle (SWA) of the resist profile. The second controller compensates for the print bias between isolated and dense lines. The third controller finds the best tradeoff between CD, SWA, and print bias. We tested the performance of the controllers using the lithography simulator PROLITH (v.7.0). The results showed a reduction of the effect of the disturbances on the CD, SWA, and print bias. Moreover, the results quantify the benefit of using focus, in addition to dose, as a control input for the purpose of controlling the resist profile.