| Summary: | 博士 === 國立中央大學 === 機械工程學系 === 84 === Chemical vapor deposition (CVD) and spin coating are two
important processes in the fabrication of semiconductor devices
and integered circuits.This study, recognization that a better
of these aspects of fabrication in very large scale integration
( VLSI) facilities and ultra large scale integration( ULSI )
facilities, addressed this issue. Chemical vapor deposition and
spincoating processes are discussed in this study. The
effects of wall cooling on the flow pattern and the uniformity
ofdeposition in a rotating CVD reactor are examined. In the
rotation-induced-flowregime, the wall cooling effect can reduce
the size of vortex. The plug flow regime would exist at higher
disk rotation rate for a cooled reactor wallthan that for an
adiabatic reactor wall. When increasing the rotating rate ofthe
disk, the effect of the walls'' cooling is significant. An
underatanding of the flow characteristics of the recirculation
zoneis critical in the designing a horizontal CVD reactor and in
controlling thedeposition process. Therefore, the length of the
recirculation zone of a central jet flowing into an enlarged
chamber is studied. A correlation equationis found to predict
the length of the recirculation zone when the expansion ratio is
larger than 2. The correlation equation has been confirmed by
theexperimental data with an expansion ratio 15.3, and agrees
with the existingdata for an expansion ratio 2.6. This
correlation equation may be used for the proper design of a CVD
reactor with a high expansion ratio. Spin coating is
utilized extensively in the microelectronics to forma thin
uniform film of photoresist or polyimide on silicon wafers.
During thisprocess, a small amount of liquid, typically in a
form of solution with a volatilesolvent, is dispensed by a
nozzle onto a high speed rotating disk, thereby convering the
wafer''s entire surface. This disk is then accelerated to a
higherspeed to sweep off the liquid. The solvent continues to
evaporate and the film eventually dries. Reducing the amount of
liquid dispensed is essential to costreduction since the
photoresist and polyimide are quite expensive. It is foundthat
after the spreading film covers the entire disk, the more liquid
dispensedonto the wafer is useless. Restated, the amount of
liquid dispensed can be reduced by controlling the dispensation
time and/or increasing the dispensation rate. To our
knowledge, no numerical study of wind shear effect on two-
dimensional film thicknessdistribution over doughnut disks has
been performed. Wind shear effect is moresignificant when the
device feature shrink to submicron level. We developeda
numerical method to predict the successiveliquid surface
cintours on the rotating doughnut disks. Also, the results are
compared with the experimental data. There are discrepancies
between the experimental data and the present numerical results.
We found that the airshear flow can not be approximated by
Cochran''s solution, and it is causedmainly by the presence of a
hub.
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