Growth of cubic silicon carbide on oxide using polysilicon as a seed layer for micro-electro-mechanical machine applications

The growth of highly oriented 3C-SiC directly on an oxide release layer, composed of a 20-nm-thick poly-Si seed layer and a 550-nm-thick thermally deposited oxide on a (111)Si substrate, was investigated as an alternative to using silicon-on-insulator (SOI) substrates for freestanding SiC films for MEMS applications. The resulting SiC film was characterized by X-ray diffraction (XRD) with the X-ray rocking curve of the (111) diffraction peak displaying a FWHM of 0.115 degrees (414 ''), which was better than that for 3C-SiC films grown directly on (111)Si during the same deposition process. However, the XRD peak amplitude for the 3C-SiC film on the poly-Si seed layer was much less than for the (111)Si control substrate, due to slight in-plane misorientations in the film. Surprisingly, the film was solely composed of (111) 3C-SiC grains and possessed no 3C-SiC grains oriented along the < 311 > and < 110 > directions which were the original directions of the poly-Si seed layer. With this new process, MEMS structures such as cantilevers and membranes can be easily released leaving behind high-quality 3C-SiC structures. (C) 2009 Elsevier B.V. All rights reserved.