Teruaki Aoki

Semi-Insulating Polycrystalline-Silicon (SIPOS) Passivation Technology

Semi-insulating polycrystalline-silicon (SIPOS) films have been used as a replacement of a silicon dioxide passivation layer of planar devices. The SIPOS films are chemically vapordeposited polycrystalline-silicon doped with oxygen or nitrogen atoms. The passivation properties of oxygen-doped SIPOS films have been examined as a function of oxygen concentration. The npn and pnp transistors rated at 800 V and 2500 V have been produced by the SIPOS process in planar-like structures with field-limiting rings. The leakage currents of 800 V pnp transistors did not increase even after the chips were exposed to water vapor at 100°C and to sodium contamination at 200°C. Thus, the SIPOS transistors can be packaged in low-cost molded epoxy as well as metal cans. Furthermore, 10 kV SIPOS transistors with multiple rings have been fabricated and their operation has been found to be stable.

Semi-Insulating Polycrystalline-Silicon (SIPOS) Films Applied to MOS Integrated Circuits

A semi-insulating polycrystalline-silicon (SIPOS) film doped with oxygen atoms is deposited on the surface of silicon substrates by a chemical vapor reaction of silane and nitrous oxide in nitrogen ambient, and has been studied for the surface passivation of MOS-ICs, in particular, C/MOS-ICs of channel-stopperless structure. SIPOS films are semi-insulating and intrinsically neutral. A double-layer system consisting of 3000 A SIPOS and 6000 A SiO2 films is employed as a replacement of a thick silicon dioxide layer in C/MOS-ICs of channel-stopperless structure and exhibits excellent field-passivating properties, namely, a small drain-source leakage current, a high drain breakdown voltage, and a high parasitic threshold voltage. Furthermore, the silicon surface passivated by SIPOS films shows high stability under a severe bias-temperature stress. It is concluded that C/MOS-ICs passivated by SIPOS films are not required to have a channelstopper diffusion region and can be operated at high applied voltages, which leads to higher integrating density and higher reliability.