AVS 51st International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS2-MoM

Paper PS2-MoM2
Etching High Aspect Ratio Structures in Si using SF@sub 6@/O@sub 2@ Plasma: Experiments and Feature Scale Modeling

Monday, November 15, 2004, 8:40 am, Room 213B

Session: Silicon Etching
Presenter: R.J. Belen, University of California Santa Barbara
Authors: R.J. Belen, University of California Santa Barbara
S. Gomez, University of California Santa Barbara
M. Kiehlbauch, Lam Research Corporation
D. Cooperberg, Lam Research Corporation
E.S. Aydil, University of California Santa Barbara
Correspondent: Click to Email
Plasma etching of high aspect ratio structures in Si is an important step in the manufacture of memory devices and MEMS components. The goal is to etch deep features anisotropically with high etch rates, high selectivity to the mask and good uniformity. We have studied the etching of deep sub-micron diameter holes in Si using SF@sub 6@/O@sub 2@ plasma. Our approach is to combine experiments and plasma diagnostics with feature scale modeling to gain a fundamental understanding of the etching kinetics necessary to develop and scale-up processes. Etching experiments are conducted in a low pressure, high density, inductively coupled plasma etching reactor. Visualization of the profiles with SEM is used together with plasma diagnostics such as optical emission and mass spectroscopies to study the effect of pressure, rf-bias voltage and SF@sub 6@-to-O@sub 2@ gas ratio on the etch rate, selectivity and feature profile shape. Simultaneous with experiments, we have developed a feature scale model of the etching process. Information from plasma diagnostics and previously published data are used to reduce the degrees of freedom in the model by estimating F, O, and ion fluxes and ion energy and angle distributions. We have designed experiments to directly measure parameters such as the chemical etch rate constant and the etch yield dependence on the ion angle. Experimentally inaccessible parameters such as sticking coefficients and etch yields are determined by matching simulated profiles with those experimentally observed under various etching conditions. The F-to-ion flux ratio and F-to-O flux ratio are found to be the important plasma parameters that determine the etch rate and anisotropy. Plasma diagnostics provide quantitative information about the location of the ion and neutral-limited regimes in the operating parameter space. The SF@sub 6@-to-O@sub 2@ gas ratio determines the balance between etching and sidewall passivation, which controls the feature profile shape.