CVD of SiC and AlN Using Cyclic Organometallic Precursors
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CVD OF SiC AND AlN USING CYCLIC ORGANOMETALLIC PRECURSORS
L.
V. Interrante,
D. J.
Department of Chemistry, 12180-3590 National Aeronautics Cleveland, Ohio 44135
Larkin,
and
Rensselaer
and
Space
C.Amato Polytechnic
Institute,
Administration,
Lewis
Troy,
Research
New York Center,
ABSTRACT The 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
used as the AlN source and has been studied apparatus in order to determine the gas phase CVD reactor environment. In the case disilacyclobutanes, [Si(XX')CH2 ] 2 (with X and
amide,
[Me 2 AlNH 2 ] 3 ,
was
in a molecular beam sampling species present in a hot-wall of SiC CVD, a series of X' - H, CH3 , and CH2 SiH 2CH3),
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 orientation). INTRODUCTION The use of single-source precursors for MOCVD of refractory materials such as AIN and SiC affords potential advantages in terms of controlling the composition, deposition temperature and microstructure of the deposited product. The need to control these factors may be particularly critical in a CVI reactor environment, where the thermal/chemical stability of the fiber reinforcement, or of the fiber-matrix interface, may set limits on the processing temperature or where the use of mixed precursor sources may lead to local variations in composition and/or microstructure [1]. The choice of organometallic molecules for use as single-source precursors has been largely an empirical process, with few guidelines available relating to the relationship between molecular structure and such factors as decomposition temperature, resulting film composition, and microstructure. In the case of SiC CVD, precursors such as methyltrichlorosilane (MTS) and the methylsilanes have been employed for many years; however, temperatures well in excess of 1000 C along with added H2 are usually needed to obtain SiC free of elemental C or Si and significant variations in composition are often experienced as the deposition conditions are varied [1,2]. Moreover, the HCI produced as a byproduct of the decomposition of chlorosilanes can be corrosive to fiber reinforcements or Si substrates [1]. The Use of Cyclic Organometallics as Precursors to AlN and SiC A key objective of our research efforts has been to develop precursors and procedures that will be effective in depositing refractory materials such as AlN and SiC in high purity at relativ
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