Self-Formation of Specific Pyramidal Planes in 4H-SiC Formed by Chlorine Based Ambience

Abstract

. Crystallographically specific pyramidal planes in 4H-SiC could be naturally formed at mesa sidewalls by a thermal etching at 900oC in a chlorine (Cl2) based ambience. The mesa structures have been fabricated on the 4H-SiC C-face with 0-45o off-angle toward [11-20]. The etched surface was rather smooth, and bunched step structures on the specific pyramidal planes were not observed with atomic force and scanning electron microscopes. The formation mechanisms of the specific pyramidal planes at mesa sidewalls are discussed on the basis of these experimental results.

Shape Control of Trenched 4H-SiC C-Face by Thermal Chlorine Etching

“…6(b). In the case of the SiC-Cl 2 -O 2 system, the etching rate of the on-axis (0001) Si-face is the lowest in the commercially available (11 20) a-face and basal-plane wafers: 14,[17][18][19][20] this implies that the etching rate of the silicon-terminated surface is low. It is considered that the surface of the V-shaped trench formed by thermal Cl 2 etching in the {11 2 a} sidewall trench will be terminated by silicon atoms.…”

“…Thermal Cl 2 etching was carried out in a horizontal resistive furnace at 101 kPa. 19,20) The reactor tube and susceptor were made of quartz, which is chemically stable at high temperatures in Cl 2 ambience. The tube diameter and length were 35 and 500 mm, respectively.…”

“…The third step was the removal of carbon in the ambience containing O 2 at 700 C for another 10 min. 20,21) The flow rates of Cl 2 and O 2 were 90 and 100 sccm in N 2 carrier gas (1 slm), respectively. Cross-sectional images of the trench structures were obtained by a scanning electron microscopy (SEM).…”

“…14,19) In the absence of O 2 , the thickness of the carbon layer proportionally increases to Cl 2 exposure time: chlorine and silicon chlorides can be moved through the carbon layer. 19,20) The plausible species produced in the SiC-Cl 2 -O 2 system are proposed to be silicon chlorides and carbon oxides, which are vaporized at high temperatures. [14][15][16]19) In this paper, thermal Cl 2 etching is applied to the shape control of SiC trenches fabricated by a plasma process.…”