Influence of vacuum annealing on interface properties of SiC (0001) MOS structures

TL;DR

This study examines how vacuum annealing affects the interface properties of SiC MOS structures, revealing that it can significantly increase interface state density and decrease mobility in certain cases, with mechanisms discussed based on SIMS analysis.

Contribution

It provides new insights into the effects of vacuum annealing on SiC MOS interfaces, especially regarding different pre-treatments and their impact on interface state density and device performance.

Findings

Vacuum annealing does not increase interface state density in as-oxidized and NO-annealed samples.

In POCl3-annealed samples, vacuum annealing greatly increases interface state density near the conduction band edge.

Vacuum annealing reduces the channel mobility in MOSFETs from 109 to 44 cm²/Vs in POCl3-annealed samples.

Abstract

We investigated the influence of vacuum annealing on interface properties of silicon carbide (SiC) metal-oxide-semiconductor (MOS) structures. For as-oxidized and nitric oxide (NO)-annealed samples, the interface state density ($D_{\rm it}$) near the conduction band edge ($E_{\rm C}$) of SiC did not increase by subsequent vacuum annealing. For phosphoryl chloride (POCl$_3$)-annealed samples, in contrast, $D_{\rm it}$ at $E_{\rm C}-0.2$ eV increased from $1.3\times10^{10}$ to $2.2\times10^{12}$ cm$^{-2}$eV$^{-1}$ by the vacuum annealing, and the channel mobility of MOS field effect transistors (MOSFETs) decreased from 109 to 44 cm$^2$V$^{-1}$s$^{-1}$. Mechanism of the observed increase in $D_{\rm it}$ was discussed based on the results of secondary ion mass spectrometry measurement.