Clearance of 4H-SiC Sub-Trench in Hot Chlorine Treatment

Abstract

The sub-trenches in 4H-SiC Si- and C-faces could be disappeared by the thermal treatment in chlorine ambience at 900-1000oC. The surface morphologies of the thermally treated trench-sidewalls were unchanged. It is considered that the sub-trench is selectively removed because thermally Cl2 etching rate of the (0001) Si- and (000-1) C-face are different to the (11-20) and (1-100).

Systematic Characterization of Plasma-Etched Trenches on 4H-SiC Wafers

“…These conditions are the best in terms of morphology, chemical structure, absence of microtrenches, and reproducibility of the final SiC trench formation. 37 In fact, while it has been reported that the microtrench phenomenon in SiC etching can be eliminated by subsequent thermal chlorine etching above 900 °C, 18,19 by the addition of HBr to SF 6 /O 2 , 20 or cyclically switching between anisotropic dry etching with SF 6 /O 2 and polymer passivation with C 4 F 8 that generates CF 2 neutral radicals in the plasma atmosphere to coat the surface and serve as a protective barrier to avoid these microtrenches, 37 within our above reported experimental conditions (O 2 concentration in the reaction gas mixture only 1.5%), 17 we did not observe any microtrench. As a general indication, within the above conditions and setup, the minimum value of the critical dimension (CD) of the SiC trench was 0.25 μm, while the maximum value of the depth trench was 10 μm.…”

“…Among the other characteristics frequently investigated during these processes, the etch rate, etching anisotropy (through the line edge profile), and taper angle (supplementary angle to the angle between the sidewalls and the bottom surface plane of the given trench) are important issues. Concerning the taper angle, the trench shape has to be conic (angles in the 86–87° range) to facilitate the filling of the trench with gate oxide, during the successive synthesis of the MOSFET. − …”

Demonstration and analysis of channel mobility, trapped electron density and Hall effect at SiO2/SiC (0$\bar{3}$3$\bar{8}$) interfaces

“…10) Furthermore, the 4H-SiC (0338) face has another feature in that the surface is automatically exposed by thermo-chemical Cl 2 gas etching. [11][12][13][14][15][16] It means that the surface is chemically the most stable crystal face. According to the theoretical approaches by Refs.…”