Nucleation Epitaxial Growth And Characterization Of Beta Sic Thin Films On Si By Rapid Thermal Chemical Vapor Deposition

ABSTRACT: Cubic silicon carbide is a promising material for applications in high-power, high-frequency, high-temperature, and high-speed electronic devices. Fourier Transform Infrared Spectroscopy (FTIR), Secondary Ion Mass Spectrometry (SIMS), X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM) evaluations performed on thin films grown heteroepitaxially on porous (i.e. anodized) silicon using a new chemical vapor deposition (CVD) method employing trimethylsilane confirmed that the thin films were stoichiometric, cubic silicon carbide (3C-SiC). Conclusions were drawn on the basis of comparisons with published standards as well as with results generated on reference materials. SIMS profiles revealed the growth rates at approximately 1150̊C to vary from 2.1 to 4.0 Å/min. depending upon the slight variations in the CVD process trimethylsilane gas pressure. AFM evaluations revealed that the deposition mode at short deposition times was homo-oriented island nucleation and growth but that the 3C-SiC thin films evolved into continuous terraced layers at longer deposition times. Heterojunction (pn) junction diodes, fabricated from CVD and chemical vapor converted (CVC) porous silicon specimens, displayed world record breakdown voltages as high as 140 volts and 150 volts respectively. Historically, heterojunction (pn) junction diodes fabricated from 3C-SiC thin film specimens deposited on non-anodized displayed breakdown voltages below 10 to 20 volts.

Thin films of beta silicon carbide were prepared on alpha silicon carbide substrates by the chemical vapor deposition (CVD) technique involving the hydrogen reduction of silane and propane. The films were prepared under a variety of conditions and subsequently subjected to thermal annealing cycles between 1600 degrees C and 2000 degrees C. It is shown that the single crystallinity of the beta films improved with continued annealing. The beta polytype was found to be stable over the entire range of temperatures studied.

The project involves the development of low pressure chemical vapor deposition and r-f sputtering techniques for the synthesis of single crystal thin films of beta-SiC. The CVD apparatus is being produced in-house and a detailed description of the design is provided herein. Theoretical CVD phase diagrams of the Si-C-H system are also being produced as a function of Si/Si+C and total pressure. Both reactive sputtering of Si in CH4 and normal sputtering of a SiC target are being readied. (Author).