CHARGE ISSUES IN HIGH OXYGEN GAS RATIO TETRAETHYLORTHOSILICATE PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION FILMS

The effect of multilayered silicon dioxide films on reflective charge, N-ss, and flatband voltage, V-fb, was investigated using plasma enhan ced chemical vapor deposition. Parameters investigated included the th ickness and type of oxide him layers, as well as dopant type. Depositi on of a high oxygen gas ratio film [4:1, oxygen:tetraethylorthosilicat e (TEOS)] as the first layer of a multilayer film resulted in a statis tically lower N-ss and a smaller shift in flatband voltage, V-fb, than films deposited with lower oxygen gas ratios (1:1, oxygen:TEOS). Mult ilayer films were deposited to a thickness of 18 k Angstrom using a hi gh oxygen gas ratio as the initial layer. These films exhibited N-ss a nd V-fb values of 1.28x10(11) cm(-2) and -11.5 V, respectively. In con trast, those films with a lower oxygen gas ratio initial layer exhibit ed statistically higher N-ss and V-fb values of 1.70x10(11) cm(-2) and -15.4 V, respectively. Film compositional changes in subsequent layer s did not display any statistically significant change in either N-ss or V-fb. The deposition of 4:1 gas ratio films occurs at a slower rate than the 1:1 gas ratio films. The use of 4:1 gas ratio films as the i nitial layer of a multilayer him allows for lower N-ss and smaller shi fts in V-fb without significantly affecting throughput. (C) 1996 Ameri can Vacuum Society.