High-voltage CMOS SIMOX technology and its application to a BSH-LSI

This paper describes high-voltage CMOS separation by implanted oxygen (SIMOX) technology and its application to a BSH-LSI that provides the basic functions of battery feed, supervision, and hybrid for subscriber line interface cuircuits. This technology is characterized by the existence of an electric-field-shielding (EFS) layer formed between the buried SiO2and the surface Si layer by oxygen implantation. The density of localized states at the Fermi level of the EFS layer has been estimated to be about 1 × 1019cm-3. eV-1using the Cohen-Fritzsche-Ovshinsky model. The EFS layer reduces substrate voltage dependence of the threshold voltage and increases the drain-to-source breakdown voltage for MOSFET's. Specifically, the drain-to-source breakdown voltage has been raised to 180 V. The BSH-LSI, which is composed of high-voltage CMOS of more than 60 V and low-voltage CMOS of 15 V, has been successfully fabricated containing resistors and capacitors. Compared with a conventional bipolar BSH-LSI, the chip size and the dissipation power of the LSI have been reduced to approximately one-third and one-half, respectively.