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A two-step donor anneal procedure applicable to control resis- tivities in as-grown Czochralski crystals or wafers is disclosed.
English (United States)
This text was extracted from a PDF file.
This is the abbreviated version, containing approximately
64% of the total text.
Page 1 of 1
Low Temperature Donor Annealing of Silicon Crystals and/or Wafers
A two-step donor anneal procedure applicable to control resis- tivities in as-
grown Czochralski crystals or wafers is disclosed.
A common silicon wafer manufacturing practice involves the use of an
extended (1/4-3 hours) heat treatment (~650OEC) on as- grown Czochralski
crystals or wafers. Its purpose is to annihilate unwanted oxygen donors created
in the crystal growth process, whose presence has a deleterious effect on the
apparent electrical resistivity of the wafers at screening. The source of such
oxygen donors has been determined to be silicon-oxygen complexes, whose rate
of formation is a function of the oxygen concentration in the material, with
maximum rates occurring ~450OEC[*]. Donor anneal therefore features a rapid
cooling-down through the 350OE - 500OEC range to avoid regeneration of the
complexes destroyed at 650OEC. Numerous past efforts to optimize
time/temperature conditions of anneal, e.g., improved cooling rates, extended
650OEC anneal times, higher anneal temperatures, etc., have not significantly
reduced crystal/wafer resistivity losses, e.g., anamolous values falling outside of
desired specification limits, suffered under the cooling-down step (450Å75OEC).
By utilizing the following two-step donor anneal procedure, however, this problem
has been eliminated during subsequent wafer screenings.
The first anneal operation step is conducted, as normal, with a heating to
550OE - 6...