Papers by Keyword: Cross-Sectional TEM

Abstract: The carbonized layer for a buffer layer strongly influences the crystalline quality of the 3C-SiC epitaxial films on the Si substrates. The growth mechanism of the carbonized layer strongly depended on the process conditions. The surface of silicon substrate was carbonized under the pressure of 7.8 × 10^-3 Pa or 7.8 × 10^-2 Pa in this research. Under the relatively low pressure of 7.8 × 10^-3 Pa, the carbonized layer was grown by the epitaxial mechanism. The crystal axis of the carbonized layer grown under this pressure was confirmed to coincide with the crystal axis of the Si substrate from the results of the selected area electron diffraction (SAED) analysis. Under the relatively high pressure condition of 7.8 × 10^-2 Pa, the carbonized layer was grown by the diffusion mechanism. The result of the SAED pattern and the XTEM image indicated that this layer consisted of small grainy crystals and their crystal axes inclined against the growth direction. It was confirmed that the crystalline quality of the SiC film deposited on the carbonized layer grown by the epitaxial mechanism is better than that deposited on the layer grown by the diffusion mechanism.

Abstract: 4H-SiC is difficult to be polishing due to its high hardness and chemical inertness. We proposed a novel polishing technique named plasma assisted polishing (PAP), in which oxidation by water plasma and polishing soft abrasive were combined. In order to increase the material removal rate of PAP and clarify the atomic-scale flattening mechanism, experimental studies on water vapor plasma oxidation and thermal oxidation of 4H-SiC (0001) were conducted. Experimental results indicated that the initial oxidation rate of water vapor plasma oxidation (185 nm/h) was much higher than that of thermal oxidation (29nm/h). In the case of water vapor plasma oxidation, the oxide/SiC interface was rough when the oxide layer was thin and it became flatter along with the increase of the thickness of the oxide layer. In contrast, the oxide/SiC interface was atomically flat regardless of the thickness of the oxide layer in the case of thermal oxidation. CeO₂ abrasive polishing was conducted on the oxidized SiC surfaces, well-ordered step/terrace structures were obtained in both cases. The step height was about 0.25 nm, which corresponds to a one-bilayer structure of 4H-SiC.

Abstract: Plasma-assisted polishing (PAP) was proposed for finishing difficult-to-machine materials, such as single-crystal SiC, reaction-sintered SiC, diamond, and sapphire. In the case of PAP application to the finishing of the 4H-SiC surface, an atomically smooth surface without any scratches was obtained. In this study, we observed 4H-SiC (0001) surfaces processed by water vapor plasma oxidation and PAP using ceria abrasives through cross-sectional transmission electron microscopy (XTEM). Water vapor plasma oxidation was conducted for 1 min, 5 min and 60 min. An intermediate layer located between SiO2 and SiC, which corresponds to silicon oxycarbide, was clearly observed in the case of a short oxidation. As oxidation time increased from 1 min to 60 min, average oxidation rate decreased from 2.7 nm/min to 0.6 nm/min. An atomically smooth 4H-SiC (0001) surface was obtained after PAP for 60 min using ceria abrasives.