Stress Gradients in SIO2 Thin Films Prepared by Thermal Oxidation and Subjected to Rapid Thermal Annealing

Abstract

ABSTRACTWe have studied stress gradients in thermally grown SiO2 thin films and relaxation of the stress by rapid thermal annealing. These properties were examined by incrementally etching back the SiO2 films and performing infrared spectroscopy and beam-bending measurements at each thickness. The thickness-averaged values measured were then deconvoluted to obtain stress values for thin layers of the SiO2 films. We observed steep stress gradients close to the Si/SiO2 interface for wet oxides which were similar to those previously studied in dry oxides. The stress gradients were steeper for films grown or annealed at high temperatures. In addition, we have been able to show that thin films (= 200 Å) relax more freely than thicker films (= 1000 Å), in which oxide close to the interface is prevented from relaxing by the oxide on top of it.