Full 3D Monte Carlo simulation of pit-type defect evolution during extreme ultraviolet lithography multilayer deposition

Abstract

To model key aspects of surface morphology evolution and to overcome one of the main barriers to the implementation of extreme ultraviolet lithography in semiconductor processing, the 3D Monte Carlo simulation of ion-beam deposition on pit-type defects was performed. Typical pit defects have depths in the 5–20nm range and are about 10 times that wide. The aspect ratio of a defect cross section defined as depth divided by the full width at half maximum was used to measure the defect profile (decoration) as a function of film thickness. Previous attempts to model this system used 2D level set methods; 3D calculations using these methods were found to be too computationally intensive. In an effort to model the system in 3D the simulation of this study used the Solid-on-Solid aggregation model to deposit particles onto initial substrate defects. Surface diffusion was then simulated to relax the defect. Aspect ratio decay data was collected from the simulated defects and analyzed. The model was validated for defect evolution by comparing simulations to the experimental scanning transmission electron microscopy data. The statistics of effective activation energy were considered to show that observed defects have important geometric differences which define a unique aspect ratio decay path. Close fitting to the observed case was utilized to validate Monte Carlo physical models of thin film growth for use in predicting the multilayer profile of pit-type defects.