Estimation of Ion/Radical Flux from Mask Selectivity and Etching Rate Calibrated by Topography Simulation

Abstract

A simple method for the estimation of ion/radical fluxes in an ion-assisted etching process was developed for SF 6 /O 2 /Si etching utilizing the difference in etching mechanism between SiO 2 mask and the silicon substrate. It was derived that F coverage of a silicon surface is approximately a linear function of the selectivity of the two materials, from which the incident ion flux and F flux are calculated. The selectivity-to-coverage proportional constant was determined using a topography simulator so that the general trend of etching profiles matched those of the experiment. The obtained fluxes showed reasonable qualitative trends in terms of reactor operational conditions and reactor parameters. The feature profiles simulated by the topography simulator using these flux values were in good agreement with those of scanning electron microscopy (SEM) experimental data over a wide range of operating conditions and machine configurations. #

Progress and perspectives in dry processes for nanoscale feature fabrication: fine pattern transfer and high-aspect-ratio feature formation

“…The topography simulations were then carried out using Sentaurus Topography with the above model, where the etching yield curve was modified, using the computed flux as input. 106) As can be seen in Fig. 24(a), the effective ion flux has a strong correlation with power and weak declining trend with pressure, while the F flux has a primary dependence on pressure, which agrees qualitatively with the plasma simulation results.…”

“…A topography simulation method to estimate the ion/ radical fluxes generated during Si etching using SF 6 /O 2 plasma has been reported. 106,107) The method utilizes the difference in etching mechanism between an SiO 2 mask where ions play an important role, and Si, where the F radical contribution is relatively large. The etching selectivity between SiO 2 and Si and the etching rates for both materials depend on molecular density, spontaneous reaction rate constant, flux of species, etching yield, and coverage of F radicals on the Si surface.…”

“…(a) Ion flux trend with pressure (P) and input power (W). (b) Comparison of (upper) simulated etching profiles against (lower) experimental SEM 106). The profiles were simulated by a topography simulator using the flux values calculated from the selectivity and etching rates.…”

Development of SF<inf>6</inf>/O<inf>2</inf>/Si plasma etching topography simulation model using new flux estimation method

“…Equations were derived based on the literature, correlating the ion and fluorine (F) flux with the etching rate and mask selectivity, which can be readily obtained through basic experiments using a production etching machine [2].…”