phys. stat. sol. (a)
, 305 (1997)
Subject classification: 73.40.Qv; S6
Advances in SiC MOS Technology
J. A. C
School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN,
(Received January 31, 1997)
Silicon carbide (SiC) is the only compound semiconductor whose native oxide is SiO
. This places
SiC in a unique position to compete with silicon in applications involving high power, high voltages,
or high temperatures. SiC MOS technology has made substantial progress in recent years. This
article aims to summarize the present status of this field, including MOS analysis techniques, oxida-
tion procedures, experimental results, reliability considerations, alternative insulators, and remain-
ing questions. In addition, we hope to convince the reader of the following: 1. Great care must be
exercized in interpreting MOS data on wide bandgap semiconductors. This is due to the extremely
long response times for interface states deep in the bandgap. 2. Recent results do not support the
argument that interface quality on p-type SiC is inferior to that of n-type.
Silicon has become the predominant commercial semiconductor material for two reasons.
First, silicon melts at a moderate temperature (1410
C), so that growth of large boules
of single-crystal material from the melt is feasible and relatively cheap. Second, silicon
can be thermally oxidized to form SiO
, an excellent insulator suitable for fabricating
oxide semiconductor (MOS) devices.
Silicon carbide (SiC) exhibits much greater physical and thermal stability than silicon.
This is both a blessing and a curse
a blessing because it makes SiC suitable for ex-
treme applications such as high-temperature and high-power devices; a curse because it
makes it impractical to grow SiC from the melt. This latter fact results in substrates
which are very small and very expensive compared to silicon, a dilemma which is the
subject of other articles in this volume.
On the positive side, SiC is the only compound semiconductor whose native oxide is
. This places SiC in a unique position in the family of semiconductor materials and
makes it possible to fabricate all of the standard silicon MOS device structures. Thermal
oxidation of SiC is similar to silicon and utilizes the same equipment, although at
slightly higher temperatures. The MOS properties of thermally oxidized SiC are not yet
as good as silicon, but steady improvements are being mande. These improvements and
the technology behind them are the subject of this article.
2. MOS Measurement Techniques for Wide Bandgap
The most important figures-of-merit for MOS interfaces are: 1 the density of interface
), 2. the density of fixed positive charges at the inter-
), 3. the density of border traps in the insulator adjacent to the
J. A. C
.: Advances in SiC MOS Technology
20 physica (a) 162/1