19 Leslie Court
Whippany, New Jersey 07981
Borosilicafilm I is designed to produce boron doped layers in silicon and other
semiconductors. The material is applied by spinning on the wafer or by spraying. A film
forms consisting of silica with boron dissolved in it. The solvent in Borosilicafilm is
ethyl alcohol. If it is desired to dilute the material, in addition to ethyl alcohol,
methanol or isopropyl may be used as diluents.
Borosilicafilm is hygroscopic. The bottle should be securely sealed to prevent access of water vapor when not in use.
One or two drops of Borosilicafilm is sufficient to cover a 1 1/2" wafer. Ten to
fifteen seconds of spinning are sufficient. Spin speed should be selected which minimizes
the lip which is observed at the edge of the wafer. After spinning, the wafer may be
heated at 50oC to 80oC to harden the film.
Borosilicafilm is especially useful where very low sheet resistance is desired. Since
the film consists of SiO2 doped with boron, nitrogen atmosphere may be employed
during the diffusion at high temperatures. No erosion or attack of the silicon surface
will occur since the oxide serves to protect the surface. Lower sheet resistance will be
observed in N2 for 1 hour, a sheet resistance less than 1 ohm per square can be
obtained. Lower sheet resistance may be obtained by providing a thicker film which is not
readily depleted thereby allowing the sheet resistance to decrease with the square root of
the time for longer periods than with thinner films. For rectifier production where a
single diffusion is carried out to achieve n+ and p doping on opposing surfaces,
Borosilicafilm will yield the desired results with no cross doping due to volatilization.
Lower surface concentrations may be obtained in one-step diffusions with specially formulated Borosilicafilm. Sheet resistances from one ohm per square to over 10,000 ohms/sq. may be obtained.
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