Correlation and Interaction between Sidewall Passivation and Chamber Walls Deposition During Silicon Gate Etching

• Published in: Contributions to plasma physics (1985) 2004-09, Vol.44 (5-6), p.413-425
• Main Authors: Kogelschatz, M., Cunge, G., Joubert, O., Vallier, L., Sadeghi, N.
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; passivation layer; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma applications; plasma composition; Plasma reactor; silicon etching
• ISSN: 0863-1042; 1521-3986
• DOI: 10.1002/ctpp.200410082

The aim of the present paper is to review our work on plasma‐surface interactions during the etching of silicon gates in low pressure high density HBr/Cl2/O2 based plasmas. In integrated circuit manufacturing, the transfer of patterns onto the polysilicon layer relies on the formation of a passivation layer on sidewalls of the etched features, which protects the silicon gate sidewall fromisotropic etching. At the same time, a layer with an almost identical chemical composition is also deposited on the reactor walls and can modify the process parameters by changing the radicals' surface loss probability. In this work we use a new “plasma etching‐sputtering” diagnostic technique, involving a subsequent “mild etching” of the layer deposited on the chamber walls by a few % SF6‐containing Ar plasma. Thus we investigate the chemical composition of this layer. This chemical composition is deduced from the time variation of the gas phase concentration of different atoms and radicals, the etch products of the wall deposited layer, monitored during the “mild etching” of the layer by time‐resolved optical emission spectroscopy and mass spectrometry. Optical absorption spectroscopy and mass spectrometry have been employed to characterize the HBr/Cl2/O2 plasma, currently used for the gate etching, and to estimate the absolute flux of neutral and ionic deposition precursors reaching the reactor walls. It comes out that the silicon wafer etch byproducts, SiClx radicals (x < 2) and SiOyCl+x ions, are the main depositing agents. Finally, the chemical topography analysis method, based on the X‐ray photoelectron spectroscopy, has been used to determine the chemical composition of the layer formed on the sidewalls of the silicon etched features. We show that the layers deposited on the sidewalls and on the chamber walls are both silicon oxyhalogenides (SiOyClx) compounds, formed by the subsequent oxidation of the deposited silicon chloride etching by‐products. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)