Defects in sublimation-grown SiC bulk crystals

Abstract

In view of its excellent thermal, mechanical and electronic properties, silicon carbide is the reference semiconductor material for high-temperature, highfrequency and high-power devices.Ingots of monocrystalline SiC which are currently grown by the seeded sublimation growth technique have opened the path to the production of largearea SiC wafers. Despite constant progress in crystal growth, the development of industrial applications has been up to now severely limited by the insufficient quality and size of the substrates. This situation results mainly from the fact that the growing process is quite complex. As a consequence, it is quite difficult to control the growth of a given polytype and the doping level while decreasing the number of defects such as misoriented domains, inclusions, macrodefects and micropipes.This paper is mainly devoted to a review of our work on the influence of the seed characteristics and the growth process parameters, such as the thermal field and the pressure, on the occurrence of defects in the as grown ingot and on the enlargement process. Polytype identification and morphology, structural perfection and defect analyses have been carried out using mainly polarized light microscopy and x-ray white-beam synchrotron topography.

Topographic study of dislocation structure in hexagonal SiC single crystals with low dislocation density

“…The etch pit density of these samples is assumed to be in the range 500-3000 cm À2 by molten KOH etching of different substrates cut from same ingots. This value is lower by 1-2 orders of magnitude than that used in previous works [6][7][8][9][10][11][12].…”

Role of micropipes in the formation of pores at foreign polytype boundaries in SiC crystals

“…For SiC crystals grown by the modified Lely technique, 1 the polytype occurrence and stability depend on the growth conditions and orientation of the substrate, [2][3][4][5][6] as well as on the probability of formation of singular faces during growth. 7 Even though the conditions for stable growth of a single polytype were developed, [2][3][4][5][6]8 uncontrolled formation of inclusions of other polytypes might occur. At the boundaries of foreign polytype inclusions, lattice defects are generated and lattice tilts are produced.…”

“…This statement was supported by the results of optical and electron beam induced current investigations. 15 Recently, white beam topography, 6 Raman spectroscopy combined with optical microscopy, 16 transmission electron microscopy, 17 and scanning electron and optical microscopies with the aid of etching by molten KOH ͑Refs. 18 and 19͒ provided evidences for MP agglomeration at the boundaries of foreign polytype inclusions.…”

Polytype inclusions and polytype stability in silicon-carbide crystals

“…The main technological method for attaining the stable growth of ingots without polytype breakdown is the use of the (0001) ingot's faces of different polarity for growth, i.e., (000 )C and (0001)Si for the polytypes 4H and 6H [12], respectively; partial or complete conversion of the ingot's polytype takes place as a result of a change in the ingot's polarity [13]. For example, in the case of growth of a 4H ingot on the Si face of the seed, complete transformation of polytype 4H to polytype 6H occurs, whereas the growth of a 6H ingot on the C face is accompanied by numerous 15R inclusions [13].…”

“…For example, in the case of growth of a 4H ingot on the Si face of the seed, complete transformation of polytype 4H to polytype 6H occurs, whereas the growth of a 6H ingot on the C face is accompanied by numerous 15R inclusions [13]. Comparison of the optimal conditions for growing commercial SiC polytypes was performed by Tupitsyn et al [14].…”