MOS Gate Stack Rie Process With Self-Passivating Sidewalls
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
The gate stack in current MOS devices is defined by first etching through the stack, then overcoating with conformal Si3N4, and then etching off the Si3N4 (Fig. 1). This leaves Si3N4 covering the edges of the stack to passivate them. This publication describes a new method (Fig. 2) of forming a stack with passivated sidewalls which simplifies the process, improves process control tolerances, and reduces etch-induced damage. The key feature of the process is the use of a halosilicon gas in place of the more usual halocarbon gas, in combination with O2 . In a typical example, a CF4 + O2 process, the O2 leads to increased F production by reacting with the carbon to form CO2, which is pumped away.