Resist parameter sensitivity analysis based on calibrated simulation for understanding resist limitations in next generation lithography

Abstract

Simulations for predicting resist effects in the sub 50 nm resolution regime are strongly requested today, as well as for improvement of present resolution and CD control. Therefore this letter reports about a simulative resist parameter sensitivity analysis with help of calibrated resist models, based on Sigma-C’s SOLID software. Target of the study was to learn about the impact of resist parameters on practical resolution limits and to derive specific process and material change proposals. After resist model calibration for 90 nm design rules, process window, mask error enhancement factor, linearity, line end shortening etc. were investigated. The main influencing resist parameters were determined with two independent methodologies: Single-and multiparameter variation, which showed good agreement. Further, the sensitivity analysis was expanded to feature sizes down to 20 nm halfpitch. To decouple all optical influences from the resist, ideal rectangular aerial images were generated and used for simulation. The simulation reveals that an ArF resist might be capable of 40 nm resolution with sufficient exposure dose latitude, comparable to today’s 90 nm design rule. On the other hand even optimized exposure tools can’t provide such ideal rectangular aerial images and there is no commercial resist known today that shows a process window at 40 nm resolution today. Therefore, the main key resist parameters, which are responsible for resolution enhancement, were identified out of this simulation study and proposals for improved processes are given.