Selective Growth of 4H-SiC on 4H-SiC Substrates using a High Temperature Mask

Abstract

Selective growth of SiC on SiC substrate was demonstrated in a chemical vapor deposition (CVD) reactor using a new high temperature mask. Bulk 4H-SiC with 8 o miscut (0001) Si-face wafers were coated with the high temperature mask and patterned using standard photolithography. The pattern consisted of window stripes as spokes of a wheel. Epitaxial growth of SiC was carried out in a conventional, horizontal, rf-heated cold wall reactor at temperatures in the range 1450-1550 o C. When the window stripes are oriented along <1120> miscut direction, the growth on the exposed area followed the substrate orientation, and the top surface was smooth and specular. However, when the window stripes are aligned along <1100> direction (perpendicular to the miscut direction), the growth on the window stripes developed (0001) facets on the surface. Epitaxial lateral overgrowth over the mask was also studied by cross sectional scanning electron microscopy (SEM). It was found that the extent of lateral growth varied with the stripe orientation. Effects of growth temperature as well as silane flows on the selective growth were also studied. Higher temperature or lower silane flow results in the etching of exposed SiC instead of growth. The etched surfaces developed orientation dependent facets similar to the growth. Importantly, the mask could be easily removed after the growth.

Fabrication and characterization of 4H-SiC P-N junction diodes by selective-epitaxial growth using TaC as the mask

“…10), as described elsewhere. 12 The refilled window perpendicular to Ͻ11-20Ͼ is preferred to maintain planarity of the wafer surface, although both types of devices did not show degrading J-V performance in our study.…”

“…The Ta film was converted to TaC by exposing the wafer to 150-ppm propane in hydrogen ambient at 1,300°C for 15 min. 12 The RIE-etched trenches were refilled by nitrogen-doped, n-type epitaxial films grown by selective epitaxy. After the growth, the TaC mask was removed by etching in a 1:1:1 ϭ HNO 3 :HF:H 2 O wet etchant.…”

“…Recently, we have reported selective growth of SiC using TaC as the mask. 12 In this paper, we demonstrate the local planar-doped regions in a SiC substrate by epitaxial growth using TaC as the mask. Trench-refilled 4H-SiC p-n junction diodes have also been fabricated using the selective-epitaxial growth technique.…”

Growth by a vapour–liquid–solid mechanism: a new approach for silicon carbide epitaxy

“…More recently, promising results were obtained with TaC. 8 However, this cannot solve the other difficulty of achieving high Al doping levels by CVD. 37 It is thus interesting to develop SEG with liquid-based techniques in order to reach the high doping level targeted for devices.…”

“…7 Note that promising results have been recently obtained with TaC. 8 Growing good quality SiC epitaxial layers at low temperatures is a challenging problem that could help in reducing the costs, increasing the safety of the process or give new perspectives for SEG. Toward this aim, growth from the melt is an interesting approach due to the low supersaturation conditions promoted at the liquid-solid interface and the absence of dangerous gases like those involved in CVD.…”