| | | Document Type | : | Latin Dissertation | | Language of Document | : | English | | Record Number | : | 53057 | | Doc. No | : | TL23011 | | Call number | : | 3161661 | | Main Entry | : | Feroz A. Mohammad | | Title & Author | : | Study of morphology, mechanisms, and interlayers in ohmic contacts to silicon carbideFeroz A. Mohammad | | College | : | Carnegie Mellon University | | Date | : | 2005 | | Degree | : | Ph.D. | | student score | : | 2005 | | Page No | : | 158 | | Abstract | : | Silicon is the most commonly used semiconductor material in the electronics industry today. Silicon carbide (SiC), however, has superior properties such as wide band gap, high breakdown field, and high thermal conductivity which make it suitable for high power, high frequency and high temperature devices. Silicon carbide's ability to function under such extreme conditions is useless without contacts and interconnects that are also capable of functioning under the same conditions. Presently, the problems with ohmic contacts to SiC entail the lack of reliable and reproducible contacts with consistent electrical properties and the lack of understanding of the mechanism. Conventional ohmic contacts to SiC require annealing at ∼1000°C. This thesis points out that the problem of inconsistency of electrical properties can be associated with the inhomogeneous morphology resulting from this high temperature annealing step. We show that this problem can be solved by developing ohmic contacts with uniform morphology or by eliminating the annealing step altogether. In this regard, we have developed PtSi single-phase contacts to p-type SiC with uniform morphology. The PtSi contacts had a smaller variation in the specific contact resistance (SCR) values and a smoother surface and interface morphology compared with the Pt and the Ti-Al contacts; this result is attributed to the uniform morphology and flat interface in the PtSi contacts. Ohmic contacts to n-type 4H- and 6H-SiC without annealing were achieved using an interlayer of epitaxial InN beneath a layer of Ti. The InN film, which was grown by do magnetron sputtering, was epitaxial to SiC with the following orientation relationship: (0001)InN || (0001)6H-SiC and [112 ̄0]InN || [112 ̄0]6H-SiC. We also report on the mechanism of ohmic contact formation in the Pt and the PtSi contacts to 4H-SiC. The Pt and PtSi contacts become ohmic after annealing at 1100°C and 1000°C, respectively. The ohmic nature of the contacts was preserved after removal of the contact layers in both the Pt and the PtSi contacts indicating that the ohmic behavior of the contacts is associated with creation or migration of defects in the SiC underneath the metal during the annealing. | | Subject | : | Applied sciences; Interlayers; Ohmic contacts; Silicon carbide; Single-phase contacts; Operations research; 0796:Operations research | | Added Entry | : | L. M. Porter | | Added Entry | : | Carnegie Mellon University |
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