Defect Status in SiC Manufacturing

Abstract

Availability of high-quality, large diameter SiC wafers in quantity has bolstered the commercial application of and interest in both SiC- and nitride-based device technologies. Successful development of SiC devices requires low defect densities, which have been achieved only through significant advances in substrate and epitaxial layer quality. Cree has established viable materials technologies to attain these qualities on production wafers and further developments are imminent. Zero micropipe (ZMP) 100 mm 4HN-SiC substrates are commercially available and 1c dislocations densities were reduced to values as low as 175 cm-2. On these low defect substrates we have achieved repeatable production of thick epitaxial layers with defect densities of less than 1 cm-2 and as low as 0.2 cm-2. These accomplishments rely on precise monitoring of both material and manufacturing induced defects. Selective etch techniques and an optical surface analyzer is used to inspect these defects on our wafers. Results were verified by optical microscopy and x-ray topography.

Point Defects in Silicon Carbide

“…The SiC wafers consist typically of a bulk substrate with so-called physical vapor transport as the prevailing (but not exclusive) principle growth method (Tairov and Tsvetkov, 1978) and then a highpurity epitaxial layer commonly realized via variants of chemical vapor deposition (CVD), such as hot-wall CVD (Kordina et al, 1994). Historically, the wafer quality has been hampered by micropipes and inclusions of different polytypes as major obstacles (Berkman et al, 2009;Gupta et al, 2012) but because of a gradual and persistent improvement of growth reactor design, source material morphology, temperature control, pressure and gas flow control, etc., 150-mm diameter 4H-SiC epitaxial wafers which are essentially free of micropipes and polytype inclusions can now be purchased, albeit at high cost. With the advancement in materials growth and increasing level of sophistication, point defects, dopants, impurities, as well as extended structural defects have evolved as crucial issues within the SiC community.…”

Chloride-Based SiC Epitaxial Growth toward Low Temperature Bulk Growth

“…Though the commercially available wafers have low micropipe densities, they still have a high density of dislocations (below 10 4 cm -2 ). 2 Most commercially available wafers come from SiC crystals that are grown by seeded physical vapor transport (PVT), 3 and others are produced by the high temperature CVD (HTCVD) technique. 4 Promising experimental results have been obtained by halide CVD (HCVD) growth, 5 which is a chlorinated gas-based technique in many ways similar to the HTCVD technique.…”

“…However, SiC power devices have not yet had their commercial breakthrough in part attributed to the still very high cost of the bulk material (calculated to be 50% of the final cost of a SiC Schottky barrier diode) and to the quality of the material. Though the commercially available wafers have low micropipe densities, they still have a high density of dislocations (below 10 4 cm −2 ) . Most commercially available wafers come from SiC crystals that are grown by seeded physical vapor transport (PVT), and others are produced by the high temperature CVD (HTCVD) technique .…”

Evolution and structure of low-angle grain boundaries in 6H–SiC single crystals grown by sublimation method

“…Sublimation method (modified Lely method) [4,5] is a successful method for growing large diameter SiC bulk single crystals. Recently, the diameter and quality of SiC substrate have made tremendous progress [6]. However, SiC wafers still have high densities of structural defects, such as dislocations and LAGBs.…”