Effect of Thermal Oxide Dislocation Enhancement on Silicon and a Proposed Mode of Propagation

Pase work on surfaces has shown the probability that active dislocation centers are involved in the Si-SiO2 interface and that such dislocations have a deleterious effect on voltages breakdown and leakage. In our development work, we have studied the effect of thermal oxidation and its role in propagation of dislocations, and have observed that type of dislocation and propagated depth can be correlated with the oxide thickness. A series of oxide experiments were run with Czochralski (100) oriented n-type Si of 5 to 6 ohm-cm resistivity using 85 C O2 at 1120 C. All wafers were poslish etched to remove ~4 to 5 mils of Si, and, immediately prior to oxidation, were boiled in hot HNO3 for 5 minutes, rinsed in dionized water, and held under water until intorduced into the oxidation furance. Silicon dioxide was thermally grown between 100 A and 5200 A. After oxidation, the oxides were removed with HF and the wafers etched in Saylor´s etch to observe dislocation enhancement due to oxide growth. Initial experiments were run with one half of each wafer oxidized and the other half held as a control for original dislocation background count. In all cases, original dislocation content was < 200/cm2. In another experiment, both sides of wafers were polish etched and the oxide-induced-dislocation enchancement evaluated against that observed where only one surface was polish etched.