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EMULSITONE COMPANY
19 Leslie Court
Whippany, New Jersey 07981
TEL. (973)386-0053
FAX (973)503-0256
GOLDSILICAFILM
Goldsilicafilm forms a film of SiO2 with gold in colloidal dispersion. It is
applied to silicon wafers by spinning or spraying. When heated to temperatures in excess
of 900oC, gold atoms will diffuse from the SiO2 layer into the
silicon. The gold atoms dissolved in the silicon will act as recombination centers and
limit the lifetime of excess minority carriers in the silicon lattice. Goldsilicafilm,
unlike Goldfilm, is designed for application to the polished surface of the wafer. Gold
diffusion is obtained without surface pitting. In this way, a most efficient gold doping
process may be carried out by introducing the gold from the active surface.
Application of Goldsilicafilm:
Goldsilicafilm is applied to the wafer surface, through windows in the masking oxide. Spin
speeds of 3000 to 6000 rpm are adequate. A glassy film with gold dispersed in it will form
after 5 to 10 seconds of spinning. The wafers may then be diffused, or if it is desired to
store the wafers prior to diffusion, they should be heated at 200-250oC for 10
to 15 minutes to harden the film.
Diffusion:
No particular dependence of gold doping concentration on ambient atmosphere has been
observed. The gold saturation concentration introduced into the silicon will be
temperature dependent, and will follow the same temperature concentration curve usually
observed for gold in silicon. Goldsilicafilm will provide sufficient gold to saturate a 10
mil silicon wafer at 1200oC.
Film Removal:
After diffusion, Goldsilicafilm is removed by soaking the wafers in 10% HF or buffered HF
solution for two to three (2-3) minutes.
GOLDSILICAFILM With Phosphorous - GOLDSILICAFILM With Boron
These doped Goldsilicafilm formulations are supplied as two solution formulations labelled
"A" and "B". While both the "A" and "B" components
have extended shelf lives, the mixtures exhibit stability on storage of 1 to 2 weeks. For
use, the "A" and "B" components are mixed in equal volume about 1 hour
prior to use. They are then applied in the same manner as is Goldsilicafilm. The doped
Goldsilicafilm will then yield N+ and P+ layers with deeper diffused
gold region immediately ahead of the N+ or P+ region. In this way,
emitter diffusion and lifetime control are carried out in a single step. The Phosphorous
or Boron surface concentration will be 1x1020 atoms/cm3, and normal
emitter diffusion processes may be employed.
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