Modification of 4H-SiC and 6H-SiC(0001)Si surfaces through the interaction with atomic hydrogen and nitrogen

Abstract

The interaction of 4H-SiC(0001) Si and 6H-SiC(0001) Si surfaces with atomic hydrogen and atomic nitrogen produced by remote radio-frequency plasmas is investigated. The kinetics of the surface modifications is monitored in real time using ellipsometry, while chemical modifications of the surface are characterized using x-ray photoelectron spectroscopy (XPS). Film morphological properties are assessed with atomic force microscopy (AFM). A two-stage substrate preparation procedure is described that effectively removes oxygen from the SiC surface at low (200°C) temperature. In the first step, the SiC surface is etched with an HCl/HF acid solution as an alternative to the conventional HF(1%)-H 2 O solution. The HCl/HF etch provides effective hydrogen passivation of the SiC surface. In the second step, the SiC surface is exposed to atomic hydrogen that selectively interacts with residual oxygen. In addition, the temperature dependence of the nitridation of SiC surfaces has also been investigated. It is found that interaction of SiC surfaces with atomic hydrogen at 200°C provides clean, smooth, and terraced surfaces suitable for epitaxial growth. In contrast, SiC surface exposure at high temperature (750°C) to atomic hydrogen and nitrogen results in very rough and disordered Si-rich surfaces. Finally, we find that the 4H-SiC surface is more reactive than the 6H-SiC surface to both species studied, independent of temperature. Surface geometry and electronic factors responsible for the observed reactivities are discussed.

Covalent Attachment of Organic Monolayers to Silicon Carbide Surfaces

“…The disappearance of the electrically insulating SiO 2 layer also becomes apparent from the significant increase in the XPS signal, which manifests as a significant improvement in the signal/noise ratio (compare parts b and c with e and f of Figure , respectively). The high-resolution C 1s region (Figures c and f) also shows intermediary oxidation states of carbon via the wide shoulder at 283.8 eV: the relatively large width at half-maximum of this peak (1.5 eV, instead of 0.9 eV) indicates that it consists of partially overlapping peaks, likely due to C−C, Si−C−O, C−O and CO species. , This etching method was reported to leave silicon carbide surfaces terminated with a thin silicon oxycarbide layer with terminal −OH groups. ,− Removal of the hydroxylic groups would require exposure to pure hydrogen under UHV conditions, , treatment with HCl/HF followed by hydrogen plasma treatment at elevated temperatures, or heating to temperatures exceeding 1000 °C. , This −OH termination was confirmed by measurement of the water contact angle (θ), which was still close to 0° after the HF etching.

1 XPS data measured on plasma-oxidized SiC (a−c) and HF-etched SiC (d−f), respectively showing wide scan and Si 2p and C 1s regions.

2 IRRA spectrum of 1-hexadecene-modified poly-SiC.

…”

Effects of remote hydrogen plasma on chemical bonding features and electronic states of 4H-SiC(0001) surface

“…To realize a high-quality SiC surface, the removal of damaged layers by chemical mechanical polishing and SiC surface cleaning by wet chemical treatment, UV-O 3 irradiation, high-temperature annealing at ∼1000 °C in hydrogen ambience, and hydrogen plasma treatment have so far been reported. [4][5][6][7][8][9][10][11] By exposing the SiC surface to atmospheric pressure hydrogen plasma and electron cyclotron resonance (ECR) hydrogen plasma, the crystallinity of the surface was improved in addition to the effect of the surface being cleaned. 12,13) On the other hand, hydrogen plasma exposure also induced the generation of surface defects, which were detected by deep-level transient spectroscopy (DLTS) and photoluminescence spectroscopy (PL).…”

Surface Cleaning of 4H-SiC Using Hydrogen Plasma

“…The traditional wet cleaning is relatively mature and simple.it can effectively remove the metal particles and organic matter impurity particles on the SiC surface. But because the polar bond on the SiC surface, The SiC surface cleaning by the traditional wet cleaning is easily adsorbed the OH-,F-,and has low flatness [3] .It is not fit to make the high performance device. Although The high temperature hydrogen treatment has a good effect at cleaning the impurity particle and hydrogen passivation, It needs a high temperature above 1000°C [4] [5] .…”