Reactive ion etching induced damage with gas mixtures CHF3/O2 and SF6/O2

Abstract

In this work, reaction ion etching (RIE) induced damage and its impact on device performance have been characterized and evaluated using a variety of characterization techniques for two technologically important gas mixtures: CHF3/O2 for selective oxide etching, and SF6/O2 for selective poly Si or crystalline Si etching. Current–voltage characteristics of Al/Si Schottky diodes fabricated on the RIE exposed Si surface reveal significant barrier height shifts for the CHF3/O2 process while showing little change for the SF6/O2 processes. Carrier generation lifetime is degraded by at least one order of magnitude, with the degradation due to CHF3/O2 processes being more severe. Scanning electron microscopy and Auger electron spectroscopy support the idea that the defects that give rise to the altered electrical behavior are most likely Si lattice damage instead of metal contamination and/or morphologic modification. Rapid thermal annealing of the CHF3/O2 etched samples has a negative effect on I–V recovery precluding simple application of RTA for removing RIE damage. In the RIE exposed oxide, the two distinctively different gas mixtures induce very similar C–V and Si/SiO2 interface property changes, suggesting that the high energy photons present in the plasma glow are the most probable source of damage in the oxide.