Improved Electrical Characteristics of MOS Devices with Ultrathin Gate Oxide Grown by Chemical Oxidation

In recent years, there is a lot of interest in developing alternative techniques for growing ultrathin SiO2 for MOS applications. Chemical oxidation of silicon in nitric acid is a promising technique as the resulting oxide has low interface state density and is free from pinholes. In this paper we demonstrate that the time and temperature of chemical oxidation play a significant role in determining the quality of the oxide. Also, the quality of the oxide improves significantly if the chemical oxidation is followed by an electrochemical (anodic) process resulting in lower gate leakage and improved reliability for the MOS devices. MOSFETs with gate oxide grown by this new technique have improved channel mobility and subthreshold slope.