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Platinumfilm is a liquid solutions for the deposition of pure
platinum films on Silicon. This solution have been designed for
use as diffusion sources to provide platinum atoms to control
minority carrier lifetime. In addition, Platinumfilm yields
metallic platinum which is conductive and may be used to replace
evaporated platinum in various applications where such films are
Platinumfilm can be applied by spinning. At a spin speed of 2000 rpm, Platinumfilm after decomposition will yield about 10 angstroms of platinum.
Heat treatment is not necessary prior to diffusion. For large furnace charges with Platinumfilm, heating the wafer in the entrance of the furnace tube will prevent smoking. Should it be desired to produce metallic films of platinum, heat treatment of the spun-on film at 300oC for 15 minutes in air will yield a pure metallic film.
Studies in the literature indicate that platinum introduces two deep impurity levels into silicon and that platinum is an amphoteric dopant in the same manner as is gold. An estimate of electrically active platinum introduced into silicon was obtained by coating "N" type silicon wafers with different donor concentrations. These were then diffused at the temperature of interest until saturation occurred. When a wafer with a specific concentration exhibited a concentration decrease of two (2) orders of magnitude, the platinum concentration was then estimated as approximating the original donor concentration. Diffusion coefficients were estimated from the time required to saturate N type wafers with the same donor concentration with the reverse surfaces masked with SiO2. With these approximate methods the following data was obtained:
|Temperature (oC)||Pt. Solubility||D cm2/sec.|
To estimate the effectiveness of platinum as a recombination center, P+N diodes were platinum doped at the temperature indicated below and the diode recovery time was measured, using a forward and reverse current of 5 ma. The table lists the recovery time observed when the diodes were saturated with platinum at the temperatures listed:
|Saturation Temperature (0C)||tr nanoseconds|