AVS 50th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS-TuM

Paper PS-TuM5
Absolute SiCl@sub X@ Densities in Silicon Gate Etching Plasmas Determined by Broad Band UV Absorption

Tuesday, November 4, 2003, 9:40 am, Room 314

Session: Plasma Diagnostics: Processing
Presenter: M. Kogelschatz, CNRS/LSP, France
Authors: M. Kogelschatz, CNRS/LSP, France
G. Cunge, CNRS/LTM, France
N. Sadeghi, CNRS/LSP, France
O. Joubert, CNRS/LTM, France
L. Vallier, CNRS/LTM, France
Correspondent: Click to Email
Broad band UV absorption spectroscopy has been used to measure the absolute gas phase concentration of SiCl@sub X@ and SiF@sub X@ etch products (X = 0-2) during silicon gate etching in high density HBr/Cl@sub 2@/O@sub 2@ plasmas and their mixture with fluorocarbon gases. The silicon atom concentration in the ground and metastable states has also been measured. To convert the absorption rates to the Si atom density, the instrumental width of the monochromator had to be taken into account. Typical concentrations of etch products are about 10@super 11@cm@super -3@, and their behavior with the plasma conditions (RF power, O@sub 2@ gas flow) will be discussed. Vibrationnally resolved absorption spectra of SiCl@sub 2@ and SiBr, observed for the first time in etching plasmas, will also be presented. However, due to the lack of absorption cross sections, the absolute concentration of SiBr can not be deduced. A particular emphasize will be given on correlation between these etch products and the composition of the films deposited on the plasma chamber walls. This composition was determined from the analysis by OES and mass spectrometry of products introduced in the gas phase of a weak Ar-SF6 plasma from the chamber walls. The deposit of the silicon oxychloride layers on the walls is at the origin of process drifts as it changes the chemical composition of the surfaces exposed to the plasma. A large change of the recombination rate of Cl atoms as a function of the reactor walls composition has been observed by measuring the variation of the Cl/Cl@sub 2@ concentration ratio in the gas phase, as well as the absolute Cl@sub 2@ concentration by UV absorption.