An Investigation of Two‐Step Oxidation in Dry Oxygen and the Effect of Oxide Thermal History on Its Growth Properties

Abstract

Gate oxide growth in ultralarge scale complementary metal oxide semiconductor technologies involves exposure to various oxidizing conditions during temperature ramp‐up and stabilization steps. These conditions are significantly different from that of the main oxidation interval. Previous studies dealing with thick oxides haying different preoxidation treatments have indicated that thermal history has a significant impact on subsequent oxide growth rate of the initial oxide. However, these trends are unclear for ultrathin oxides. In this paper, we report the results of our study on two‐step oxidation in the thin (accelerated) regime. We have used initial oxides of different thicknesses, grown under various processing conditions prior to growing the second oxide film. The results indicate that, in contrast to the case of thick oxides, the thermal history from the first step oxidation (i.e., during temperature ramp‐up and stabilization or initial oxidation) has no impact on subsequent oxide growth rate. Furthermore, we have extended the accelerated growth model by Massoud to account for two‐step oxidations.