METHOD OF REDUCING SILICON OXYNITRIDE GATE INSULATOR THICKNESS IN SOME TRANSISTORS OF A HYBRID INTEGRATED CIRCUIT TO OBTAIN INCREASED DIFFERENTIAL IN GATE INSULATOR THICKNESS WITH OTHER TRANSISTORS OF THE HYBRID CIRCUIT

摘要

A relatively thin gate insulator of a digital switching transistor is formed from a layer of silicon oxynitride which was initially formed by implanting nitrogen atoms in a silicon substrate and oxidizing the nitrogen and silicon. It has been discovered that an outer layer of silicon dioxide is formed as a part of the silicon oxynitride layer. Removing this outer layer of silicon dioxide from the silicon oxynitride layer leaves a thin remaining layer of substantially-only silicon oxynitride as the gate insulator. Thinner gate insulators of approximately 15-21 angstroms, for example, can be formed from a grown thickness of 60 angstroms, for example. Gate insulators for digital and analog transistors may be formed simultaneously with a greater differential in thickness been possible by using conventional nitrogen implantation techniques.