Channel doping profile of silicon-on-sapphire transistors

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Abstract
Dopant profiles of low-dose channel implant in silicon-on-sapphire (SOS) field-effect transistors are investigated by comparing results from various techniques, including theoretical calculation by the Stanford University integrated-circuit process simulation program (suprem) and experimental measurements by secondary ion mass spectrometry (SIMS), capacitance-voltage (C-V), spreading resistance and metal-oxide-semiconductor Hall effect. It is shown that, for both phosphorus- and boron-implanted SOS films having constant doping profile at a level close to 1×1016 cm−3, as predicted by suprem and measured by SIMS, the charge density measured by C-V technique and free carrier concentration obtained from spreading resistance technique decrease with increasing distance from the Si surface. For SOS films implanted to a level greater than 1× 1017 cm−3 boron, the dopant profile obtained by SIMS analysis coincides with the charge density profile, measured by C-V technique, and the free carrier concentration profile, deduced from spreading resistance, and the actual mobility in SOS films.