Dislocation evolution in 4H-SiC epitaxial layers

Abstract

4H-SiC commercial wafers and sublimation grown epitaxial layers with a thickness of 100 μm have been studied concerning crystalline structure. The substrates and the epitaxial layers have been separately investigated by high-resolution x-ray diffraction and synchrotron white beam x-ray topography. The results show that the structural quality was improved in the epitaxial layers in the [112̄0] and [1̄100] directions, concerning domain distribution, lattice plane misorientation, mosaicity, and strain, compared with the substrates. Misoriented domains have merged together to form larger domains while the tilt between the domains was reduced, which resulted in nonsplitting in diffraction curves. If the misorientation in the substrate is large, we can only see a slight decrease in the misorientation in the epilayer. At some positions on the substrates block structures (mosaicity) were observed. ω-rocking curves showed smaller full width at half maximum values and more uniform and narrow peaks, while the curvature was almost the same in grown epilayers compared with the corresponding substrates. We show that threading edge dislocations along the c axis in silicon carbide grown crystals transform to deflected dislocations in the epilayer. A formation mechanism for deflected dislocations and supporting facts are presented. We further show that these deflected dislocations are one possible source for the creation of stacking faults that recently has been reported to cause degradation in processed SiC bipolar diodes.

Formation of extended defects in 4H‐SiC epitaxial growth and development of a fast growth technique

“…Since the BPDs propagate roughly parallel to the [1120] direction, the BPDs in the epilayer have a predominantly screw character. All these results are consistent with the earlier study by Jacobson et al [39] and can represent a common trend in using 〈11 20〉 off-cut {0001} substrates. In addition, BPDs in the epilayers grown on the substrate off-cut towards 〈1 1 00〉 also roughly propagate parallel to the step flow [40].…”

Effect of initial substrate conditions on growth of cubic silicon carbide

“…5a) one can notice several peaks indicating that the crystal consists of several domains, slightly (50-400 arcsec) tilted to each other [18]. Similar observations have been done on 6H and 4H-SiC epilayers [19][20][21]. The misoriented domains on 3C-SiC can appear because of two-dimensional nucleation.…”

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

“…Synchrotron radiation X-rays, due to the coherence and power of their beams, are ideal for topography observation. In the case of 4H-and 6H-SiC, backscattering topography with synchrotron radiation white X-ray beams has been performed and has revealed hollow-core screw dislocations, closedcore screw dislocations and basal plane dislocations [1,3,[5][6][7][8].…”