IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Monday Sessions
       Session PS2-MoM

Invited Paper PS2-MoM4
Diagnostic of Silicon Etch Plasmas by Optical and Mass Spectrometry, Correlation with XPS Surface Diagnostics

Monday, October 29, 2001, 10:40 am, Room 104

Session: Diagnostics I
Presenter: O. Joubert, CNRS, France
Authors: N. Sadeghi, University Joseph Fourier-Grenoble and CNRS, France
G. Cunge, LTM/CNRS (CEA-LETI), France
R.L. Inglebert, LTM/CNRS (CEA-LETI), France
L. Vallier, LTM/CNRS (CEA-LETI), France
O. Joubert, CNRS, France
Correspondent: Click to Email
As device dimensions are continuously decreasing, the precise critical dimension control during the etch processes becomes a key issue in device fabrication. A better understanding of both plasma composition and plasma-surface interaction during the process are required to obtain a deeper insight on etch mechanisms involved in plasma etching. This work is centered on polysilicon gate etch processes using HBr/Cl@sub 2@/O@sub 2@ and HBr/Cl@sub 2@/O@sub 2@/CF@sub 4@ chemistries in an inductively coupled DPS-5200 Applied Materials reactor. The chemical composition of the layers deposited on the trench sidewalls is analyzed by quasi-insitu XPS and is correlated to the relative densities of the different neutral species present in the gas phase and to the composition of the ions impinging on the wafer surface and on the reactor walls. The following conclusions can be drawn: - Contrary to the expectations, halogen ions are not the dominant ionic species impacting on the wafer surface. Mass spectrometry measurements show that in standard etch conditions, Si@super +@ and other silicon containing ions can account by more than 50% of the total ion flux. - In HBr/Cl@sub 2@/O@sub 2@ gas mixtures, the passivation layer is formed by redeposition of silicon etch products fragmented in the plasma and then redeposited on the feature sidewalls where they get oxidized by the oxygen present in the gas phase. When CF@sub 4@ is added into the gas mixture, the passivation layer is formed by condensation of CF@sub x@ species on the feature sidewalls. - Mass spectra experiments also give some interesting information on the influence of CF@sub 4@ addition in keeping the chamber walls clean. Consequences on real processes are discussed.