Chemical Vapor Deposition of SiC from Silacyclobutane and Methylsilane
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CHEMICAL VAPOR DEPOSITION OF SiC FROM SILACYCLOBUTANE AND METHYLSILANE
A. D. JOHNSON*, J. PERRIN", J. A. MUCHA*, and D. E. IBBOTSON* * AT&T Bell Laboratories, Murray Hill, NJ 07974 ** CNRS Palaiseau, France
ABSTRACT The kinetics of SiC deposition has been studied over the temperature range using the single-source reagents silacyclobutane (SCB) and methylsi-
650-1050 'C
lane (MeSiH 3 ) whose decomposition supplies the isomeric film-forming precursors H 2 Si = CH 2 and HSiCH 3 , respectively. Thermal decomposition has been monitored by mass spectrometry and the SiC thin films characterized by scattering spectrometry (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 MeSiH 3 decomposition, respectively. Silacyclobutane deposits C-rich material lower temperatures, while SiC deposited from MeSiH 3 is Si-rich at all temperatures. A mechanism for SiC CVD is proposed that is consistent with the observed kinetics and products.
INTRODUCTION The mechanical and electronic properties of silicon carbide are presently being exploited in thin film applications ranging from X-ray lithography to diodes and transistors that operate in high temperature and hostile environment. Recently, efforts have been directed at designing precursors specifically for SiC CVD 11,21. An ideal source material is one that decomposes at low temperatures to form a film having the desired film properties. Here, we describe the kinetics of low pressure CVD of SiC from two source gases, silacyclobutane (SCB) and methylsilane (MeSiH 3 ), and the material deposited from them has been characterized with respect to their composition and structure.
EXPERIMENTAL, SCB (Dow Corning Corp., 99 %) and MeSiH
3
(Huls America Inc., 97 %) were
pyrolyzed in a cold wall, low pressure CVD reactor equipped with a resistively heated susceptor that allowed heating an z-4 cm by 4 cm section of a Si(100) wafer. Wafer heating was primarily radiative at the deposition pressure of 50 mTorr, so the Mat. Res. Soc. Symp. Proc. Vol. 282. @1993 Materials Research Society
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highest achievable substrate temperature was 1050 * C as was measured by an optical pyrometer. Deposition was monitored by timed deposition experiments and/or interferometrically with a 633 nm HeNe laser. Film thicknesses were measured following deposition with a Nanometrics nanospec. Decomposition products were detected with a quadrupole mass spectrometer (QMS).
Compositions of films were determined by Rutherford backscattering (RBS) analysis and total hydrogen content was measured by elastic recoil detection (ERD). Transmission infrared spectra were collected with a FTIR spectrometer. RESULTS SiC deposition rates on Si(100) as a function of substrate temperature are shown in Figure 1. The deposition rate from 50 mTorr SCB is 1 A/s at 700 °C, increasing to 60 A/s at 1050 * C. Under the same conditions, SCB and MeSiH
3
exhi-
bit similar deposition rates; however, activation energies f
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