A. Nouailhat

Analysis and minimization of small-geometry effects on the current gain of self-aligned 'etched-polysilicon' emitter bipolar transistors

The authors report on a detailed analysis of small-geometry effects on the current gain of advanced self-aligned etched-polysilicon emitter bipolar transistors. By studying the dependence of collector and base currents on device geometry and process parameters, they have been able to identify the critical fabrication steps and physical mechanisms involved. The narrow emitter effect is caused by the butting of the emitter-base junction to the field oxide, and is mainly controlled by the gate oxide removal step prior to polysilicon deposition. Short emitter effects are associated with phenomena taking place in the spacer region of the device perimeter during polysilicon patterning, spacer pedestal thermal oxidation, link base implantation, and final rapid thermal anneal. Proper adjustment of all process parameters is shown to allow good control of the narrow-emitter effect and complete compensation of short-emitter effects, showing promise for the future of this CMOS-compatible bipolar transistor structure. >

Base profile tail effects on the low temperature operation of silicon bipolar transistors

This paper reports new results on bandgap narrowing in self aligned polysilicon emitter bipolar transistors. Using temperature dependent current gain measurements, we show that the tail region of the implanted base plays a dominant role in the effective bandgap narrowing of the base. This result will be very important for the development of pseudo-heterojunctions and low temperature-operation bipolar transistors.

Impact ionization effects in silicon vertical JFET's

This paper reports the observation and analysis of excess gate and substrate currents in advanced self-aligned vertical Si junction field-effect transistors (JFETs). These currents are proposed to result from impact ionization effects, causing generation of minority holes in the channel and photo-generation of minority electrons in the substrate.