(45f) SiC Substrate Cleaning for Epitaxy Using a Thermally Generated Atomic Hydrogen Beam

Wide bandgap semiconductors are becoming the new platform of choice for devices with greater power density and energy efficiency than silicon. In particular, Silicon carbide (SiC) is ideal for high power and high temperature (>150ºC) electronic applications because of its high critical electric field voltage (2500 kV/cm) and good thermal conductivity (4.9 W/cmK) [1]. However, heteroepitaxial film growth of functional oxides on SiC, is a challenging and yet critical goal to achieve in order to fully utilize SiC in next-generation electronics.

Formation of an abrupt and effective interface is one of the basic requirements for integration of functional oxides on semiconductors. A reliable and effective cleaning procedure must be developed in order to produce consistent and well-characterized starting surfaces. Several SiC surface cleaning studies, including traditional wet cleaning, high-temperature hydrogen etching and hydrogen plasma treatment have been reported in order to remove contaminations and scratches made during polishing [2].

In our previous work, 6H-SiC (0001) substrates were cleaned in an ex-situ hydrogen furnace. Tantalum foil strip is used as heating element during furnace operation where the 6H-SiC sample is placed on it. The resulting 6H-SiC surfaces are smooth with a uniformly stepped surface and a â??3Ã?â??3R30º surface reconstruction with a silicate adlayer, verified by reflection high energy electron diffraction (RHEED) and x-ray photoelectron spectroscopy (XPS) [3]. This is consistent with that reported by Starke and coworkers [4]. However, the high treatment temperature (~1600 ºC) and sensitivity to small thermal gradients makes it impractical for a low-cost and high-throughput production.

In this study we demonstrate the effects of atomic hydrogen produced by a hydrogen atom beam source (HABS). The HABS is a thermal gas-cracking cell consisting of a tungsten filament set in high purity tungsten tube. It has been found that the atomic hydrogen irradiation is productive for removal of carbon and oxygen on Si surfaces at relatively low temperature without any ion damage to the substrates [5]. We compare the treatment of 6H-SiC surfaces with hydrogen atomic beam source and the hydrogen flow furnace, in order to understand the fundamental H-atom interactions with the surface and then use that knowledge to develop an optimized surface cleaning process.

1. H. Lingqin, Zhu Qiaozhi, Gao Mingchao, Qin Fuwen, and W. Dejun, Cleaning of SiC surfaces by low temperature ECR microwave hydrogen plasma. Applied Surface Science, 2011. 257(23): p. 10172-10176.

2. King, S.W., S. Tanaka, R.F. Davis, and R.J. Nemanich, Hydrogen desorption from hydrogen fluoride and remote hydrogen plasma cleaned silicon carbide (0001) surfaces. Journal of Vacuum Science & Technology A, 2015. 33(5): p. 05E105.

3. Goodrich, T., J. Parisi, J. Leong, and K.S. Ziemer. SiC surface preparation by hydrogen cleaning for high-temperature, high-power device integration. in Proceedings of the AiChE Annual Meeting. 2005.

4. Starke, U., J. Schardt, J. Bernhardt, and K. Heinz, Reconstructed oxide structures stable in air: Silicate monolayers on hexagonal SiC surfaces. Journal of Vacuum Science & Technology A, 1999. 17(4): p. 1688-1692.

5. Chun, Y.J., T. Sugaya, Y. Okada, and M. Kawabe, Low temperature surface cleaning of InP by irradiation of atomic hydrogen. Japanese Journal of Applied Physics, 1993. 32(2B): p. L287.