Simulation of Dilute Hydrofluoric Acid Etching of Silicon Dioxide Films in Constrained Spaces

By: Ryan O’CONNELL, Srini RAGHAVAN*

11 April 2019


Figure 4 Equilibrium concentration profile of HF2- with -20 mV at the silicon/solution interface

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Author(*) Information:  Professor,Department of Materials Science and Engineering,University of Arizona, Tucson

Control of lateral etching of films that are constrained by non-etching films is an area of great interest in the manufacturing of semiconductor devices such as 3-D NAND memory. In this paper, lateral etching of very thin silicon dioxide films sand-wiched between silicon films in dilute hydrofluoric acid has been simulated using COMSOL Multiphysics modeling soft-ware. Specifically, using literature equations for the etch rate of ‘standalone’ oxide films, a time-dependent moving-boundary simulation that takes into account the electrical charging of wetted surfaces has been used to determine the effect of thickness of constrained oxide films on their etch rate. The results have been compared with experimentally mea-sured etch rates for very thin oxide films reported in the literature.

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