Floating gates and methods of formation

摘要

The present invention generally relates to a floating gate structure and method of forming the same. The floating gate structure has an upper portion which is wider than a middle portion of the floating gate structure. The upper portion may have a flared, rounded or bulbous shape instead of being pointed or having sharp corners. The reduction in pointed or sharp features of the upper portion reduces the electric field intensity near the upper portion, which decreases current leakage through the interpoly dielectric. The method includes forming a nitride cap on the upper surface of the floating gate structure to assist in shaping the floating gate. The floating gate is then formed using multiple selective oxidation and etching processes.

主权项

1. A method of forming a floating gate structure, comprising:
exposing an upper surface of a floating gate to nitrogen radicals to form a first silicon nitride region thereon; exposing the upper surface of the floating gate to the nitrogen radicals at a temperature of about 800° C. or higher to form a second silicon nitride region thereon, wherein the second silicon nitride region encompasses the first silicon nitride region; after forming the first and second silicon nitride regions, removing one or more field oxides positioned adjacent to the floating gate; oxidizing a portion of the floating gate to form silicon dioxide; further removing a portion of the one or more field oxides and the silicon dioxide of the floating gate; and entirely removing the first and second silicon nitride regions from the upper surface of the floating gate.