Silicon material activities are described. Topics discussed include: fluidized bed technology, model predictions (reaction kinetics and grid design parameters), seed-particle cleaning procedure, runaway nucleation, thermal analysis of dendritic ribbons, and residual stress in dendritic ribbons

Lutwack, R.

English

NASA Technical Reports Server

!N86- 29364
SILICON MATERIAL AND JPL WEB TEAM
Ralph Lutwack, Chairman =.
This session consisted of four presentations on silicon material
' activities and two presentations describing the efforts of the JPL Web Team.
Union Carbide Corp. described progress in the program to develop
fluidized-bed technology for the silane system. Quartz liners used in I
:. experimental runs continue to fail on cool-down. A modified reactor has been
designed to permit the use of com_ercially available quartz tubes and to !
improve the liner seals. Experiments with the new reactor will be done during
the contract extension (ending December 31, 1985). Improvements in the
cleaning procedure for the seed material were indicated by the purity
measurements. In a ll0-h run at a silane concentration in the range of 20 to
30_ in H2, several kilograms of product were obtained. A layered structure
of the particles was found using scanning electron microscope (SEM) analyses. ,:
.. Washington University at St. Louis reported on the development of a
model of the silane fluidized-bed system. The sensitivity of the model
f
predictions to the reaction kinetics and to the grid design parameters were
examined. Both factors have significant influence on the model predictions, i
It is evident that the reaction kinetics and the distributor plate must be
subjects of experimental studies to supply the information needed for refining
the model.
JPL reported progress in the in-house program for the study of the
silane fluidized-bed system. A seed-particle cleaning procedure was developed
,: to obtain material purity near the level required to produce a semiconductor-
I
grade product. The liner-seal design has been consistently proven to
withstand heating-cooling cycles in all of the JPL experimental runs. A i
"_ _ry of the JPL silane fluidized-bed program is being written.i
,°
: The California Institute of Technology (Caltech) presented a more
complete analysis of the phenomenon of runaway nucleation in a silane-free
space reactor system which occurred in its program to describe, theoretically,
; the growth of silicon particles and to develop, experimentally, the conditions
for particle growth. The experimental conditions with a silane concentration
increment leading to the condition and the theoretical treatment of the
phenomenon were described.
JPL presented a thermal analysis model to describe the dendritic ribbon
process. The model uses a melt-dendrite interface which projects out of the
bulk melt as the basic interpretation of the ribbon production process. This
is a marked departure from the interpretations of the interface phenomena
which have been used previously. The model was extensively illustrated with
i diagrams and pictures of ribbon samples. This model would have great impact
on the analyses of experimental data as well as on future design modiflc_tions
_I' of ribbon-pulling equipment.
JPL also presented simplified models of the residual stress in dendritic
ribbons and of the associated ribbon properties.
PRECEDINGPAGE_L_,_NKNOT FIL_EC 1247
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1986019875-252
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Silicon material and JPL Web Team

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