We report the experimentally obtained response surfaces of silicon etching rate, aspect ratio dependent etching (ARDE), photoresist etching rate, and anisotropy parameter in a time multiplexed inductively coupled plasma etcher. The data were collected while varying eight etching variables. The relevance of electrode power, pressure, and gas flow rates is presented and has been found to agree with observations reported in the literature. The observed behavior presented in this report serves as a tool to locate and optimize operating conditions to etch high aspect ratio structures. The performance of this deep reactive ion etcher allows the tailoring of silicon etching rates in excess of 4 m/min with anisotropic profiles, nonuniformities of less than 4% across the wafer, and ARDE control with a depth variation of less than 1 m for trenches of dissimilar width. Furthermore it is possible to prescribe the slope of etched trenches from positive to reentrant.

Ion bombardment energy and angle distributions have been measured in an argon plasma. The measured ion angle distribution at 10 mTorr shows that 30% of the ions have incident angles greater than 10° from the surface normal. However, ions with large incident angles have much lower energies than those incident perpendicular to the surface. At 500 mTorr a very large fraction of the ions have large incident angles, and the average energies of these ions are relatively independent of incident angle. Monte Carlo simulations of the sheath kinetics predict the trends shown in the experimental data for ion energy and angle distributions. Fine structure in the ion energy distribution was observed below 50 mTorr and is shown to be caused by charge-exchange collisions in the sheath. The average ion energy in a symmetric parallel plate system is linearly related to the voltage applied across the electrodes for measured plasma pressures up to 500 mTorr.

The localized charging of a rectangular trench during the plasma etching of a perfectly insulating surface was modeled assuming an isotropic electron flux and monodirectional ion bombardment. The field set up by the localized charging acts to deflect arriving ions, modifying the ion flux densities within the feature, and thus, etching rates. Preliminary simulations indicate that this may be important in the shaping of etching profiles.

A self-consistent continuum (fluid) model for a radio-frequency discharge is presented. The model is one dimensional, incorporates an electron energy balance, and is valid for both electropositive and electronegative discharges. A connection of the fluid model with the underlying physics is presented: issues such as the derivation of the fluid equations from moments of the Boltzmann equation, the closure of the set of moments, and the fundamental assumptions behind the fluid equations are discussed. A detailed set of results for an electropositive and an electronegative discharge is presented, and contrasted. The sustaining mechanisms and the electrical characteristics of the two discharges are also discussed. Comparison with experimental data of spatially and temporally resolved plasma induced emission is successfully done.

A multiple beam apparatus has been constructed to facilitate the study of ion-enhanced fluorine chemistry on undoped polysilicon and silicon dioxide surfaces by allowing the fluxes of fluorine (F) atoms and argon (Ar+) ions to be independently varied over several orders of magnitude. The chemical nature of the etching surfaces has been investigated following the vacuum transfer of the sample dies to an adjoining x-ray photoelectron spectroscopy facility. The etching ‘‘enhancement’’ effect of normally incident Ar+ ions has been quantified over a wide range of ion energy through the use of Kaufman and electron cyclotron resonance-type ion sources. The increase in per ion etching yield of fluorine saturated silicon and silicon dioxide surfaces with increasing ion energy (Eion) was found to scale as (Eion1/2−Eth1/2), where Eth is the etching threshold energy for the process. Simple near-surface site occupation models have been proposed for the quantification of the ion-enhanced etching kinetics in these systems. Acceptable agreement has been found in comparison of these Ar+/F etching model predictions with similar Ar+/XeF2 studies reported in the literature, as well as with etching rate measurements made in F-based plasmas of gases such as SF6 and NF3.