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Unformatted text preview: IEEE ELECTRON DEVICE LETTERS, VOL. 18, NO. 5, MAY 1997 175 Nitridation of Silicon-Dioxide Films Grown on 6H Silicon Carbide Sima Dimitrijev, Member, IEEE , Hui-feng Li, Student Member, IEEE , H. Barry Harrison, and Denis Sweatman Abstract— This letter addresses the question of why it is possible to grow high-quality oxide films on N-type but not on P-type SiC. It provides results which indicate that the oxide/SiC interface would be inferior to the oxide/Si interface for both, N-type and P-type SiC, if it were not for the beneficial effects of nitrogen incorporation. The letter presents, for the first time, results on nitridation of thermally grown oxides in NO and N P O. The results demonstrate that the oxides grown on P-type can be improved by NO annealing, but not by N P O annealing. I. INTRODUCTION S UCCESSFUL growth of silicon-dioxide films on silicon- carbide substrates may mark the beginning of a new era in semiconductor electronics. Metal-oxide-semiconductor (MOS) devices based on a wide band-gap material such as silicon carbide have the potential to revolutionize power electronics, microwave systems, high temperature, and many other applications. At present, it is not understood why it is possible to grow high-quality oxide films on N-type but not on P-type SiC –. Initially, it was speculated that the aluminum (used as the P-type dopant in SiC) was causing this problem –. Later, it has been shown that boron-doped P-type SiC does not improve the quality of the oxide , and that aluminum is also present in high-quality oxides grown on N-type SiC . In this letter, we present results which shift the focus from the potential problems with the P-type SiC to the beneficial role of nitrogen, used as a dopant in the N-type SiC. We report, for the first time, results on nitridation of O-grown oxides in NO and N O. The results suggest that the oxides grown on P-type SiC can be improved by NO annealing, which is a significant step toward a successful fabrication of enhancement type N-channel MOSFET’s on SiC. II. EXPERIMENTAL DETAILS Si-faced 6H SiC wafers, manufactured by CREE Research, were used in this experiment. The concentration of the nitrogen doped N-type wafer was cm , while the concen- tration of the aluminum doped P-type wafer was cm . The wafers were cut into approximately cm pieces, and cleaned by both an H SO :H O solution and RCA cleaning process. Immediately before the oxidation, the samples were dipped in 1% HF for 60 s. The SiC carbide Manuscript received November 29, 1996. This work was supported by a Large Australian Research Council (ARC) Grant. The authors are with School of Microelectronic Engineering, Griffith University, Nathan, Brisbane, Queensland 4111, Australia....
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This note was uploaded on 12/10/2009 for the course IF PFIS1200 taught by Professor Antonio during the Spring '09 term at Universidade Federal do Rio de Janeiro.
- Spring '09