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J. Vac. Sci. Technol. A 7, 2758 (1989); http://dx.doi.org/10.1116/1.576175 (8 pages)

In situ laser diagnostic studies of plasma‐generated particulate contamination

G. S. Selwyn1, J. Singh2, and R. S. Bennett2

1IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598
2IBM East Fishkill Facility, Route 52, Hopewell Junction, New York 12533

Laser light scattering measurements show that certain silicon etching plasmas produce a significant amount of in situ, particulate contamination. The particles are suspended at the sheath boundaries. Simultaneous measurement of plasma negative ions by the use of two‐photon laser‐induced fluorescence technique suggests that the particles are negatively charged and so are electrostatically trapped at the sheath boundaries. The parametric conditions for particle formation and growth in the plasma are identified. A mechanism for nucleation and growth is suggested involving formation of plasma negative ions from etch products, ion clustering with plasma species, and cluster growth into particles with electrostatic suspension and trapping. The particles drop onto the wafer when the rf is turned off. Implications for dry process technology are discussed.

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0734-2101 (print)  

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