SiC CVD Research Articles

Dopant Incorporation Efficiency in CVD Silicon Carbide Epilayers

ABSTRACTIn order to ensure reproducible and reliable SiC semiconductor device characteristics, controlled dopant incorporation must be accomplished. Some of the many factors which greatly influence dopant incorporation are the site-competition effect, SiC(0001) substrate polarity, substrate temperature, and the dopant-source reactor concentration. In this paper, dopant incorporation is considered and compared for various dopants in the context of dopant incorporation efficiency. By using secondary ion mass spectrometry (SIMS), the relative dopant incorporation efficiencies were calculated by dividing the SIMS determined dopant concentration in the resulting epitaxial layer by the intentional gas phase dopant concentration used during the SiC CVD. Specifically, the relative magnitudes of dopant incorporation efficiencies for nitrogen, phosphorus, and boron in 6H-SiC (0001) Si-face epitaxial layers are compared as a function of the site-competition effect and the dopant-source reactor concentrations. This serves as a first approximation for comparison of the relative “doping potencies” of some common dopants used in SiC CVD epitaxial growth.

Reactants in SiC chemical vapor deposition using CH3SiH3 as a source gas

The growth mechanism of SiC CVD using CH3SiH3 (1% CH3SiH3 diluted by 99%H2) as a source gas is studied by the experiment with macro/microcavity method. It is found that there are two types of the important reactants: one is the slightly active source gas CH3SiH3 itself, which reacts directly with the SiC surface. The other is the CH3SiH, which is produced by the thermal decomposition of CH3SiH3 in the gas phase, it is radical and its sticking coefficient is almost 1. Under the kinetic control conditions, the reaction of CH3SiH3 with SiC surface and the decomposition of CH3SiH3 in the gas phase determine the growth rate.

Chemical Vapor Deposition of SiC from Silacyclobutane and Methylsilane

ABSTRACTThe kinetics of SiC deposition has been studied over the temperature range 650–1050 ° C using the single-source reagents silacyclobutane (SCB) and methylsi-lane (MeSiH3 ) whose decomposition supplies the isomeric film-forming precursors H2Si = CH2 and HSiCH3, respectively. Thermal decomposition has been monitored by mass spectrometry and the SiC thin films characterized by scattering spec-trometry (RBS & ERD), FTIR spectroscopy and X-ray diffraction. Deposition rates from the two are comparable, with activation energies of 41 kcal/mole and 53 kcal/mole for SCB and MeSiH3 decomposition, respectively. Silacyclobutane deposits C-rich material lower temperatures, while SiC deposited from MeSiH3 is Si-rich at all temperatures. A mechanism for SiC CVD is proposed that is consistent with the observed kinetics and products.

CVD of SiC and AlN Using Cyclic Organometallic Precursors

AbstractThe use of cyclic organometallic molecules as single-source MOCVD precursors is illustrated by means of examples taken from our recent work on SiC and AlN deposition, with particular focus on SiC. Molecules containing (SiC)2 and (AlN)3 rings as the “core structure” were employed as the source materials for these studies. The organoaluminum amide, [Me2AlNH2]3, was used as the AlN source and has been studied in a molecular beam sampling apparatus in order to determine the gas phase species present in a hot-wall CVD reactor environment. In the case of SiC CVD, a series of disilacyclobutanes, [Si(XX′)CH2]2 (with X and X′ - H, CH3 , and CH2 SiH2CH3), were examined in a cold-wall, hot-stage CVD reactor in order to compare their relative reactivities and prospective utility as single-source CVD precursors. The parent compound, disilacyclobutane, [SiH2 CH2]2, was found to exhibit the lowest deposition temperature (ca. 670 °C) and to yield the highest purity SiC films. This precursor gave a highly textured, polycrystalline film on the Si(100) substrates (70% with a SiC<lll> orientation).

Design and synthesis of CVD precursors to thin film ceramic materials

The application of cyclic organometallic compounds as single source precursors for the chemical vapor deposition of materials such as AIN and SiC is discussed and new results relating to the decomposition of a novel SiC CVD precursor are presented. The decomposition of the cyclic carbosilane [μ-(CH 2) 2Si(CH 3)(H)Si(CH 3)(CH 2SiH 2CH 3)], ( I) on a heated glassy carbon subst rate in an ultra-high vacuum molecular beam system has been studied by pulsing the precursor molecule onto the surface and following the mass spectrum as a function of the substrate surface temperature. The evolution of CH 3SiH 2, C 2H 5 and CH 3 was evidenced, suggesting loss of excess carbon as C 1 and C 2 species.

Modeling of the SiC chemical vapor deposition process and comparison with experimental results

A model of the NASA Lewis SiC-chemical vapor deposition (CVD) process is described and the results presented. A key feature of the model is the direct coupling of gas phase chemical kinetics with diffusion. A deposition chemistry model using reactive sticking coefficients for each gas phase species provides the diffusion boundary conditions. Chemical characteristics of the SiC CVD process are discussed and a comparison between predicted and experimentally observed deposition rates is made. SiC deposition rates predicted by the model agree reasonably well with the observed rates. Qualitative agreement for deposition rate dependence on velocity is obtained, although lack of agreement on details of the behavior indicate that improvements in the fluid dynamic model are needed.

Gas-Surface Reaction Studies Relevant to SiC Chemical Vapor Deposition

ABSTRACTReactions of C2H4, C3H8, and CH4 on Si(111) and C2H4 on Si(100) have been investigated for surface temperatures in the range of 1062 K to 1495 K. These studies used x-ray photoelectron spectroscopy to identify the reaction products, characterize the solid state transport process, determine the nucleation mechanism and growth kinetics, and assess orienta-tion effects. The results are used to provide insight into the mechanisms of SiC CVD processes.