Bipolar transistors in silicon-on-sapphire (SOS): effects of nanosecond thermal processing

Nanosecond thermal processing (NTP) using a XeCl excimer laser was employed in the fabrication of npn bipolar transistors in silicon-on-sapphire (SOS). Functional devices, with current gain approach 100, were obtained. The deleterious effects of diffusion pipes in SOS material were minimized using rapid laser activation of ion implanted dopant. Devices were fabricated using n-type epitaxially deposited silicon on double-solid-phase-epitaxy (DSPE) improved SOS. The total thickness of the first and second silicon epi-layers was nominally 2.0 mu m. Devices were fabricated using three different laser fluences for the emitter anneal. This corresponds to a variation in melt duration and corresponding metallurgical junction depth.<>