Journal article
A scattering ratio method for sizing particulates in a plasma
Plasma sources science & technology, Vol.5(1), pp.84-92
1996
DOI: 10.1088/0963-0252/5/1/011
Abstract
Particulates suspended in plasma can be sized in situ using the scattering ratio method, which involves measuring the ratio of the parallel and perpendicular polarizations of light scattered at 90°. This method of plasma monitoring is of interest for controlling contamination of silicon wafers and other thin film products during plasma etching and deposition procedures. For parameters typical of plasma processing, we report Mie scattering computations to test the method's sensitivity to the optical design and to uncertainties in the particle parameters. A ±20% error in the size determination can result either from an uncertainty of ±1 either in the real or in the imaginary part of the refractive index or from a particle shape that deviates significantly from a sphere. A ±5% error results from a 0.1° error in aligning the scattering angle. To measure particulate diameters as small as 0.05 μm, the detector solid angle should be < 10-5 Sr and the extinction ratio of the polarizer must be < 10-4. A calculation of the signal-to-noise ratio reveals that it is untenably weak for particle diameters smaller than about 0.04 μm. The scattering ratio method is usually inapplicable for polydisperse particulates, but it will still work in many cases for many plasma applications, in which particles stratify in different layers according to their size.
Details
- Title: Subtitle
- A scattering ratio method for sizing particulates in a plasma
- Creators
- G Praburam - University of IowaJ Goree - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Plasma sources science & technology, Vol.5(1), pp.84-92
- Publisher
- Institute of Physics
- DOI
- 10.1088/0963-0252/5/1/011
- ISSN
- 0963-0252
- eISSN
- 1361-6595
- Language
- English
- Date published
- 1996
- Academic Unit
- Physics and Astronomy; Mechanical Engineering
- Record Identifier
- 9984200042602771
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