Chemical Vapor Deposition of SiO 2 from Ozone-Organosilane Mixtures near Atmospheric Pressure
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CHEMICAL VAPOR DEPOSITION OF SiO
2
FROM OZONE-
ORGANOSILANE MIXTURES NEAR ATMOSPHERIC PRESSURE
K. V. GUINN and J. A. MUCHA AT&T Bell Laboratories, Murray Hill, N.J. 07974
ABSTRACT The kinetics of deposition of SiO
2
by the reaction of tetramethylsilane (TMS)
with ozone (03) has been studied over the temperature range 180 - 380° C and compared with available data for the same process using tetraethoxysilane (TEOS). Both processes exhibit the same activation energy (17 kcal/mole) below 300" C which falls-off at higher temperatures due to transport limitations. Transition from first- to zero-order kinetics occurs with increasing concentrations of TMS and 03, which gives an overall 0 3 /TMS consumption ratio of 10 at 258* C and 5 at 325* C. TEOS is estimated to be 5 times more reactive than TMS above 300 * C and over 10 times more reactive in the kinetically-limited regime below 300" C. Results suggest that 0
3 -induced
SiO 2 deposition proceeds via surface reactions and is limited by
heterogeneous decomposition of ozone.
INTRODUCTION As silicon technology evolves to ever higher circuit densities and increasing numbers of interconnection levels, the deposition of high-quality, void-free interlevel dielectric layers at low process temperatures (< 400 * C) is becoming increasingly important. Deposition near atmospheric pressure may be suitable for filling high aspect-ratio topography
since mean-free-paths are less than 0.1 pm.
However,
unlike low-pressure plasmas where reactive species can be generated at low temperatures, high pressure processes require either high temperatures (> 700 * C) or reactants with considerable reactivity.
This latter strategy has been exploited recently
using ozone-induced chemistry to form Si0 report the kinetics of Si0
2
2
from alkoxysilanes
film deposition from TMS/0
3
f1,2].
Here, we
and compare the results
to published data for TEOS/O3 chemistry.
EXPERIMENTAL The reactor is a modified Plasma Technology, Ltd. parallel-plate unit with a showerhead
in the upper electrode to mix and disperse gases.
TMS (Aldrich,
90.9+%) was metered under its own vapor pressure from a cylinder containing Mat. Res. Soc. Symp. Proc. Vol. 282. 01993 Materials Research Society
576
Linde 4A molecular sieves using a mass flow controller and mixed with helium to minimize residence time in the delivery system.
The TMS-He mixture was blended
with an 03/02 mixture near the entrance to the showerhead. Variable concentrations of ozone in 02 were generated with a PCI Ozone ozonizer and typical reactor feed consisted of about 70% 02 and 26% He, with variable concentrations of TMS (0.1-2.1 vol%) and 03 (0.59-3.4 vol%). For comparison, one film was deposited with 0 3 -TEOS chemistry at 330 * C using a 0.036 v% TEOS, 1.5 v% 03 mixture at the same total flow (1440 sccm) and system pressure (520 Torr). Deposition rates were determined by timed experiments, measuring the thickness of the deposited SiO film with a Nanospec microarea gauge.
2
RESULTS and DISCUSSION Figure 1 shows the temperature
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