VSim benchmarking and improvements for high-aspect-ratio etch modeling

High-aspect-ratio (HAR) plasma etching processes can be optimized for uniformity and regularity through the use of kinetic (particle-in-cell) modeling tools, which capture the motion of charged particles and their deposition on the substrate on length scales comparable to the desired critical dimensions. Such kinetic models are able to resolve detailed physics processes that cannot be resolved with fluid codes, e.g. the response of incident ions to charge accumulation on trench walls. Ongoing developments in VSim [1] (a finite-difference time-domain/PIC-MCC-DSMC code) that focus on such modeling are presented. VSim’s previously-shown ability to rigorously pass low-temperature modeling benchmarks posed by Turner et al. [2] has recently been augmented. As well, new user examples demonstrating the use of the code for geometrically complex HAR etching applications have been developed, and novel boundary conditions that mimic the behavior of bulk plasma far from the substrate have been formulated. In these boundary conditions, the disparity between electron and ion mobilities is exploited to balance and smooth incident particle fluxes in the presheath region.

[1] www.txcorp.com/vsim

[2] M. M. Turner et al., Phys. Plasmas 20, 013507 (2013).