In Situ N[sub 2]-Doping of SiC Films Grown on Si(111) by Chemical Vapor Deposition from Organosilanes

Abstract

SiC has many superior properties for high power and high frequency electronic devices, such as wide bandgap, high breakdown field, high saturation velocity, and high thermal conductivity. In addition, its high Young's modulus and its toughness, chemical inertness, and radiation resistance make it an excellent material for the fabrication of microelectromechanical systems sensors and controllers operating in extreme environments such as those in turbine engines and nuclear reactors.Among more than 170 SiC polytypes, 6H-, 4H-, and 3C-SiC are the three most commonly used polytypes in the microfabrication of devices. 6H-and 4H-SiC are the best polytypes for power electronic devices due to the rapid improvement in both size and quality of the substrates. 3C-SiC has its own unique features, such as highest electron mobility, isotropy in both mechanical and electrical properties, and no micropipe defects. The major hurdle of 3C-SiC development is the lack of sizable substrate. However, 3C-SiC can be heteroepitaxially grown on Si substrates, which provides a low cost alternative method for obtaining SiC. Currently, chemical vapor deposition (CVD) is widely employed to grow epitaxial SiC on Si. SiC CVD growth normally takes place at relatively high temperatures (ϳ1350ЊC) with an SiH 4 /C 3 H 8 /H 2 gas system. The hazardous nature of these gases requires special handling. We have been pursuing the use of the novel organosilane precursors silacyclobutane (SCB-SiC 3 H 8 ) and trimethylsilane (3MS-SiC 3 H 9 ) as alternative Si and C sources for the growth of 3C-SiC. 1-5 SCB has a strained fourmember ring and 3MS has a sterically hindered structure. These features make them easier to pyrolyze, with a high growth rate. Furthermore, these precursors are nonpyrophoric and noncorrosive, making them safer to handle than silane. Films grown by CVD using SCB or 3MS 3,5 show that crystalline SiC can be obtained on Si(111) at growth temperatures below 1200ЊC. Our previous results show that the chemical and structural properties of SiC films using 3MS or SCB are similar to those grown at higher temperatures using the SiH 4 /C 3 H 8 /H 2 gas system.In this work, the electrical transport properties of in situ N 2 -doped 3C-SiC films grown on Si(111) using SCB or 3MS are investigated by Hall effect measurements and reflection-mode Fourier transform infrared spectroscopy (FTIRS). The electron carrier density and mobility are measured as a function of N 2 flow rate. Reflection-mode FTIRS and secondary-ion mass spectroscopy (SIMS) also were utilized to support Hall effect measurements. The relationship between the Hall mobility and the carrier concentration at 300 K also is presented and compared to previously published data. ExperimentalThe SiC films were grown on 3 in. Si(111) substrates (p-type, 150-300 ⍀-cm, off-axis) using SCB or 3MS at 1200ЊC and 4 Torr. Prior to CVD growth, a thin buffer layer was formed using propane at 1300ЊC and 1 atm to reduce the effects of large lattice mismatch and thermal expansion coefficient difference betwe...

Electrical Characterization of n-Type Polycrystalline 3C-Silicon Carbide Thin Films Deposited by 1,3-Disilabutane

“…͑The carrier concentration and mobility of undoped poly-SiC were not measurable with our setup due to its high resistivity.͒ From 1-5% doped samples, the carrier concentration increased from 9.2 ϫ 10 15 to 6.8 ϫ 10 17 cm −3 , and mobility decreased from 2063 to 400 cm 2 /V s. Compared to single-crystalline n-type 3C-SiC epitaxial films with similar carrier concentrations, the mobility values for more heavily doped samples ͑NH 3 /DSB ϭ 0.03, 0.04, 0.05͒ were comparable to those of single-crystalline 3C-SiC, while the mobilities for lightly doped samples ͑NH 3 /DSB ϭ 0.01, 0.02͒ were much larger. 18,19 It has been recognized that in inhomogeneous polycrystalline films, both the grains and the space-charge regions surrounding the grain boundaries contribute to the Hall voltage, which makes the measured mobility fundamentally different from the microscopic mobility determined by carrier-scattering mechanisms, the latter being the case for the single crystalline semiconductors. In the case of poly-Si, the measured carrier concentration is always less than the carrier concentration in the grains, and this discrepancy decreases with a decrease in the energy barrier at the grain boundary.…”

Growth and doping of SiC-thin films on low-stress, amorphous Si3N4/Si substrates for robust microelectromechanical systems applications

“…The details of the system can be found in Ref. 6. The base pressure in the chamber is 3 ϫ 10 Ϫ3 torr, and the operating pressure is 13-14 torr.…”

“…We have previously reported 5 that the single, organosilaneprecursor trimethylsilane [(CH 3 ) 3 SiH or 3MS] produces excellent 3C-SiC films while being nonpyrophoric, noncorrosive, and easier to handle than the conventional SiH 4 /C 3 H 8 /H 2 gas system used for SiC growth. Our previous results with 3MS show that SiC films grown on Si substrates 6 can be in situ doped with N 2 and that undoped films can be grown successfully on Si 3 N 4 layers 3 on Si substrates. In this paper, the electrical properties of in situ N 2 -doped 3C-SiC films grown on low-stress, amorphous Si 3 N 4 /Si (100) substrates using 3MS are investigated by Hall-effect measurements, while structural characterization of these films has also been investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM).…”

In Situ Doping of Nitrogen in <110>-Oriented Bulk 3C-SiC by Halide Laser Chemical Vapour Deposition

“…In recent decades, a great deal of work has been focused on the preparation of N-doped SiC by adding NH 3 [5,10] or N 2 [11,12] during CVD, achieving σ values from 0.1 to 10 3 S/m. However, the deposition rates (R dep ) were limited to values between 0.1 and 10 µm/h [10][11][12][13][14]. Due to the low deposition rate, conventional CVD is usually effective for preparing SiC films but not bulk crystals, which greatly limits the applications of doped SiC.…”