AVS 49th International Symposium
    Plasma Science Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA1
Plasma-Wall Interaction Studies during Gate Etch Processes

Tuesday, November 5, 2002, 2:00 pm, Room C-105

Session: Plasma Surface Interactions I
Presenter: G. Cunge, CNRS/LTM, France
Authors: G. Cunge, CNRS/LTM, France
M. Kogelschatz, CNRS/LSP, France
N. Sadeghi, CNRS/LSP, France
L. Vallier, CNRS/LTM, France
O. Joubert, CNRS/LTM, France
Correspondent: Click to Email
During a CMOS gate etch process, requirements in terms of Critical Dimension Control are more and more severe and the process reproducibility from wafer to wafer is becoming a serious issue. Process drift are commonly observed in high density plasma sources operating in HBr/Cl@sub2@/O@sub2@ and HBr/Cl@sub2@/O@sub2@/CF@sub4@, and originate from the deposits of SiOX and SiO-CFX layers on the reactor walls. In the present paper, mass spectrometry and optical emission have been used to investigate the influence of the reactor walls’ chemical nature on the recombination rate of halogen atoms, and on the surface loss rate of silicon etch by products. To begin with, the chemical nature of the layers deposited in various chemistry has been characterized by time-resolved actinometry: after a gate etch process, the layer deposited on the reactor walls is sputtered by a pure argon plasma and the emission from etch product and halogen atoms monitored as a function of time. The results gives insight on the chemical nature of the layer as a function of its thickness. Complementary experiment where the layer is sputtered in an Ar-O@sub2@ plasma also provides information on the layer deposition mechanism, which proceeds through re-deposition and oxidation of halogenated silicon etch products. As a result, we will show that when a carbon source is provided to the gas phase of an HBr/Cl@sub2@/O@sub2@ plasma (either through CF@sub4@ addition, or in the presence of photo-resist) the layer composition change from SiOCl to a mixture of SiOCl-C(F) species. Mass spectrometric measurement demonstrates that the presence of carbon in the layers is accompanied by a drastic increase of the Br and Cl atoms recombination coefficient, whose concentration in the gas phase consequently drops.