Modeling of fluorine-based high-density plasma etching of anisotropic silicon trenches with oxygen sidewall passivation

Abstract

Level set approach to simulation of feature profile evolution in a high-density plasma-etching systemThe kinetics of high aspect ratio, anisotropic silicon etching in a SF 6 -O 2 plasma is investigated with a combination of Monte Carlo simulations and inductively coupled plasma etching experiments. The spontaneous reaction of atomic fluorine is dominant at room temperature and Knudsen transport of the radicals is the only limitation in narrow structures. At low temperatures ͑typically between Ϫ125 and Ϫ95°C͒ oxygen passivation becomes effective and anisotropic profiles are obtained because the oxygen passivation can only be removed by the directional ion bombardment. The input parameter settings for the Monte Carlo model are based on measurements with plasma diagnostics. Simulations show that anisotropy is controlled by the oxygen sidewall passivation which depends on the oxygen flux, the oxygen adsorption coefficient, and the aspect ratio. The simulated trench profiles and the aspect ratio dependent etch rate are consistent with the experimental results. Experimentally the etch rate behavior can be tuned from aspect ratio dependent to aspect ratio independent by decreasing the ion flux. This effect can be described well by the recently developed chemically enhanced ion-neutral synergy model. It turns out that aspect ratio independent etching is obtained if the downwards depletion of fluorine radicals due to Knudsen transport is compensated by an increase of the available reaction sites.

Properties of deep etched trenches in silicon: Role of the angular dependence of the sputtering yield and the etched species redeposition

“…Under these conditions, the etching rates are very low. The comparison between these results and experiments performed in DIMES laboratory in the Netherlands [17] has shown that the best correlation is obtained with the trench T1. In this case, topography and the etching rates are very similar.…”

“…For the trench T1, an excellent mask transfer is obtained: the sidewalls are almost vertical without roughness. The vertical etching rate is about 3.5 mm/min which is closed to the experiments [17]. On the contrary, the properties of trench T2 are very modified and affected by the strong redeposition phenomenon.…”

“…The objective of this section is to try to characterize the level of the redeposition mechanism by comparison with experimental results [17]. Only two extreme cases are presented here: an etching process without redeposition (simulation T1) and another with a high level of redeposition (simulation T2).…”

Concurrent effects of wafer temperature and oxygen fraction on cryogenic silicon etching with SF6/O2 plasmas

“…[6] There are some computational studies of SF 6 /O 2 plasmas but they do not explicitly refer to cryoetching. Blauw et al [15] investigated the kinetics of SF 6 Ryan and Plumb previously developed a model to describe the SF 6 /O 2 plasma chemistry and the etching of Si with these plasmas, [20] [ 21] In recent years, not only low-k dielectric cryoetching but also silicon cryoetching has gained increasing interest. The primary difficulty with SF 6 /O 2 cryogenic DRIE is the high sensitivity to the oxygen content and the substrate temperature.…”

Atomic scale study of InP etching by Cl2-Ar ICP plasma discharge

“…Indeed, it is now possible with plasma etching process using high density plasma reactors such as Inductive Coupled Plasma (ICP) to transfer nanometer scale patterns from the mask to the substrate [1][2][3][4][5]. The success of the high aspect ratio pattern transfer without geometrical defects [6][7][8][9] (bowing, undercut, trenching,..) is tributary of a good understanding of the physical and chemical mechanisms of the plasma discharge and the surface kinetic processes. Some attempts of Si and III-V pattern transfer development like photonic crystals, deep trenches or mesa structures are achieved by plasma etching [10][11][12][13][14][15][16].…”