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Chemical Topography of Si Etching in a Cl2 Plasma, Studied by X-RAY Photoelectron Spectroscopy and Laser-Induced Thermal Desorption

Published online by Cambridge University Press:  22 February 2011

V. M. Donnelly ,
K. V. Guinn ,
C. C. Cheng  and
I. P. Herman
V. M. Donnelly
Affiliation:
AT&T Bell Laboratories, 600 Mountain Ave., Murray Hill NJ, 07974
K. V. Guinn
Affiliation:
AT&T Bell Laboratories, 600 Mountain Ave., Murray Hill NJ, 07974
C. C. Cheng
Affiliation:
AT&T Bell Laboratories, 600 Mountain Ave., Murray Hill NJ, 07974
I. P. Herman
Affiliation:
Also with the Department of Applied Physics and the Columbia Radiation Laboratory, Columbia University, New York, NY, 10027
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Abstract

This paper describes x-ray photoelectron spectroscopy (XPS) studies of etching of Si in high-density Cl2 plasmas. Polycrystalline Si films, masked with photoresist stripes, are etched and then transferred in vacuum to the XPS analysis chamber. Shadowing of photoelectrons by adjacent stripes and differential charging of the photoresist and poly-Si were used to separate contributions from the top of the mask, the side of the mask, the etched poly-Si sidewall, and the bottom of the etched trench. In pure Cl2 plasmas, surfaces are covered with about one monolayer of Cl. If oxygen is introduced into the plasma, either by addition of O2 or by erosion of the glass discharge tube, then a thin Si-oxide layer forms on the sides of both the poly-Si and the photoresist. Laser-induced thermal desorption (LITD) was used to study etching in real time. LITD of SiCI was detected by laser-induced fluorescence. These studies show that the Si-chloride layer formed during plasma etching is stable after the plasma is extinguished, so the XPS measurements are representative of the surface during etching. LITD measurements as a function of pressure and discharge power show that the etching rate is limited by the positive ion flux to the surface, and not by the supply of Cl2, at pressures above 0.5 mTorr and for ion fluxes of σ4× 1016cm−2 s−1.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 334: Symposium W – Gas-Phase and Surface Chemistry in Electronic Materials Processing , 1993 , 425
Copyright
Copyright © Materials Research Society 1994

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