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A successful production
of semiconductor devices requires that the silicon wafers,
boats, paddles, tubes, etc. be carefully cleaned of all
contaminates before they are used. Usually these materials
are cleaned with one of the procedures that have become
somewhat standard in the semiconductor industry. However,
if the procedure is found to have a deleterious effect on
the performance of the material, some alternate cleaning
procedure must be used.
This is the case for the
PhosPlus sources. This bulletin gives recommended procedures
on how to clean the PhosPlus sources. It also gives cautions
on alternate cleaning solutions and procedures that may
harm the sources.
The PhosPlus sources are
cleaned of processing contaminates before shipping. If additional
cleaning is desired, however, the following procedure will
etch away any foreign matter and will expose a pristine
15 seconds dilute acid
at room temperature in:
This procedure is only
recommended for initial cleaning of the PhosPlus sources.
After they have been used, a significant amount of the aluminum
metaphosphate in the TP470 source has been converted to
aluminum orthophosphate and the lanthanum pentaphosphate
in the TP250 source has been converted to lanthanum metaphosphate.
Since these products of the decomposition reactions are
very soluble in acids, the acids could rapidly attack the
sources and quickly disintegrate them. The higher the use
temperature and the longer the source has been used, the
more severe will be the attack on the source by the acid.
After the cleaning process
is complete, the sources should be inserted into the diffusion
furnace to begin the aging cycle using the procedures outlined
in Product Bulletin 511. The aging cycle insures that the
PhosPlus sources are evolving P2O5 at a uniform rate, that
all moisture is vaporized and that any residual cutting
and cleaning solutions are oxidized.
The PhosPlus sources must
be cleaned of processing contaminates if optimum results
are to be obtained. However, unless the proper cleaning
solutions are used, the sources could be destroyed or their
doping characteristics may be severely affected. The cleaning
procedures outlined in this bulletin will provide the process
engineer with the proper techniques for the PhosPlus sources.