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Proceedings Paper

Diode laser sensor to monitor HCL in a plasma etch reactor
Author(s): Suhong Kim; Pete Klimecky; Shang-I Chou; Jay B. Jeffries; Fred Lewis Terry; Ronald K. Hanson
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Paper Abstract

Absorption measurements of HCl during plasma etching of poly-silicon are made using the P(4) transition in the first vibrational overtone band near 1.79 μm. Single path absorption provides a real-time HCl monitor during etching of six-inch wafers in a commercial Lam Research 9400SE reactor at the University of Michigan. Wavelength modulation at 10.7 MHz is used to distinguish the absorption signal from the strong plasma emission. The laser center frequency is ramp-tuned at 500 Hz providing an HCl measurement every 2ms. Direct absorption measurements without the plasma are used to calibrate the wavelength modulation signal. The minimum detectable absorbance was 5x(10)-6 with 50 ms averaging, leading to an HCl detection limit of ~(10)12cm-3. For a given ratio of the feedstock HBr/Cl2, the measured HCl concentration tracks the average etch rate. These measurements demonstrate the feasibility of a real-time diode laser-based etch rate sensor.

Paper Details

Date Published: 23 September 2002
PDF: 8 pages
Proc. SPIE 4817, Diode Lasers and Applications in Atmospheric Sensing, (23 September 2002); doi: 10.1117/12.452073
Show Author Affiliations
Suhong Kim, Stanford Univ. (United States)
Pete Klimecky, Univ. of Michigan (United States)
Shang-I Chou, Stanford Univ. (United States)
Jay B. Jeffries, Stanford Univ. (United States)
Fred Lewis Terry, Univ. of Michigan (United States)
Ronald K. Hanson, Stanford Univ. (United States)


Published in SPIE Proceedings Vol. 4817:
Diode Lasers and Applications in Atmospheric Sensing
Alan Fried, Editor(s)

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