Effects of Post Annealing and Oxidation Processes on the Removal of Damage Generated during the Shallow Trench Etch Process

In this study, 0.3–0.5 µm deep silicon trenches were etched using Cl2/10%N2 and Cl2/50%HBr inductively coupled plasmas, and the defects remaining on the etched silicon trench surfaces and the effects of various annealing and oxidation on the removal of the defects were studied. High resolution transmission electron microscopy was used to investigate the degree of remaining defects and X-ray photoelectron spectroscopy was also used to investigate surface contamination of the etched silicon wafers. Defects were found on the silicon trench surfaces etched using both Cl2/10%N2 and Cl2/50%HBr. A thermal oxidation of 200 Å at the temperature up to 1,100°C did not remove the remaining defects completely and more defects were remained on the silicon trench etched using Cl2/10%N2. More defects remaining on the oxidized silicon trench for Cl2/10%N2 appear to be related to the formation of silicon oxynitride on the silicon trench etched in Cl2/10%N2, therefore, forming less thermal oxide during the oxidation process. The annealing of the etched silicon trenches from 900°C to 1,000°C for 30 min in N2 also decreased the number of defects, however, to remove the defects formed in our experiments, the annealings at the temperature higher than 1,000°C in N2 for 30 min appears to be required. A combination process of annealing at 1,000°C and oxidation at 900°C was also effective in removing the defects completely.