AVS 47th International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS-MoM

Paper PS-MoM5
Silicon Etch Yields and Etching Chemistry in F@sub 2@, Cl@sub 2@, Br@sub 2@, and HBr High Density Plasmas

Monday, October 2, 2000, 9:40 am, Room 311

Session: Plasma-Surface Interactions I
Presenter: S.A. Vitale, Massachusetts Institute of Technology
Authors: S.A. Vitale, Massachusetts Institute of Technology
H.H. Sawin, Massachusetts Institute of Technology
Correspondent: Click to Email
Etch yields of silicon in F@sub 2@, Cl@sub 2@, Br@sub 2@, and HBr high density plasmas have been measured as a function of ion bombardment energy, ion bombardment angle, and plasma composition. This information forms a database of experimental values needed for feature profile evolution modeling. For all plasma chemistries, the etch yield increases with the square root of ion energy. Pure Cl@sub 2@ and pure HBr plasmas have very similar etch yields. Silicon etch rates are lower in HBr plasmas than in Cl@sub 2@ plasmas due to lower ion fluxes, not lower etch yields. The dependence of the etch yield on ion bombardment angle is significantly different for Cl@sub 2@ and HBr plasmas. The etch yield in Cl@sub 2@ plasmas decreases rapidly for ion angles above 60° (measured form the surface normal), which results in significant ion scattering from the sidewalls, causing the sidewall bowing and microtrenching seen when patterning polysilicon with Cl@sub 2@ plasmas. The etch yield in HBr plasmas decreases more gradually with ion angle, resulting in less ion reflection from feature sidewalls and could explain the lack of sidewall bowing and microtrenching seen when patterning polysilicon with HBr plasmas. HBr plasmas have higher etch yields than Br@sub 2@ plasmas due to: 1) the higher volatility of SiH@sub x@Br@sub y@ products compared to SiBr@sub 4@, and 2) extra Si surface coverage by small H atoms. As the temperature of the silicon increases, the etch yield in HBr plasmas decreases, due to reduced surface coverage by adsorbed Br and H atoms.