SiC materials are currently metamorphosing from research and development into a market driven manufacturing product. SiC substrates are currently used as the base for a large fraction of the world production of green, blue, and ultraviolet light-emitting diodes (LEDs). Emerging markets for SiC homoepitaxy include high-power switching devices and microwave devices for S and X band. Applications for heteroepitaxial GaN-based structures on SiC substrates include LEDs and microwave devices. In this paper we review the properties of SiC, assess the current status of substrate and epitaxial growth, and outline our expectations for SiC in the future.

SiC materials-progress, status, and potential roadblocks

Silicon carbide (SiC) as both the most important non-oxide ceramic and promising semiconductor material grows stoichiometric SiO 2 as its native oxide. During passive oxidation, a surface transformation of SiC into silica takes place causing bulk volume and bulk mass increase. This review summarizes state-of-the-art information about the structural aspects of silicon carbide, silica, and SiC–SiO 2 interfaces and discusses physicochemical properties and kinetics of the processes involved. A special section describes the electronic properties of carbide–oxide interfaces, which are inferior compared to Si–SiO 2 interfaces, limiting the use of SiC-based electronics. In the oxidation of SiC there is a variety of parameters (e.g., porosity, presence of sintering aids, impurities, crystallographic orientation, surface treatment, and atmospheric composition) influencing the process. Therefore, the kinetics can be complex and will be discussed in detail. Nonetheless, a general linear-parabolic time-law can be foun...

Silica on Silicon Carbide

Direct observation of dislocations propagated from 4H–SiC substrate to epitaxial layer by X-ray topography

A model is presented for a possible mechanism of screw dislocation (including micropipe) nucleation in silicon carbide. The model is based on the observation of micropipe nucleation at the sites of foreign material inclusions using synchrotron white beam x-ray topography and transmission optical microscopy. It is shown that incorporation of the inclusion into the growing crystal can lead to deformation of the protruding ledge which constitutes the overgrowing layer. Accommodation of this deformation into the crystal lattice leads to the production of pairs of opposite sign screw dislocations which then propagate with the growing crystal. Evidence for the existence of such pairs of dislocations is presented.

The mechanism of micropipe nucleation at inclusions in silicon carbide

We discuss continuing materials technology improvements that have transformed silicon carbide from an intriguing laboratory material into a premier manufacturable semiconductor technology. This advancement is demonstrated by reduced micropipe densities as low as 0.22 cm−2 on 3-in.-diameter conductive wafers and 16 cm−2 on 100-mm-diameter conductive wafers. For high-purity semi-insulating materials, we confirm that the carbon vacancy is the dominant deep-level trapping state, and we report very consistent cross-wafer activation energies derived from temperature-dependent resistivity.Warm-wall and hot-wall SiC epitaxy platforms are discussed in terms of capability and applications. Specific procedures that essentially eliminate forward-voltage drift in bipolar SiC devices are presented in detail.

Bulk crystal growth, epitaxy, and defect reduction in silicon carbide materials for microwave and power devices

A kinematic (geometrical) diffraction simulation model has been developed to provide understanding of direct dislocation images on synchrotron white-beam X-ray topographs, and has been successfully applied to illustrate the contrast formation mechanisms involved in images of micropipe-related superscrew dislocations in silicon carbide crystals. The coincidence of the simulations with the contrast features of the superscrew dislocation images, recorded using a series of synchrotron topography techniques, shows that this model is capable of revealing the detailed diffraction behavior of the highly distorted region around the dislocation core and determining the quantitative characteristics of the dislocations. The simulation technique is thus demonstrated to be a simple but efficient method for interpretation of synchrotron topographs, and may be applied to explain the topographic contrast characters of general crystal defects.

W. Huang

Papers

Superscrew dislocation contrast on synchrotron white-beam topographs: an accurate description of the direct dislocation image