Ensure that the PhosPlus sources are
loose in their slots. Tight slots can result in breakage of
Slot dimensions and carrier fabrication dimensions can be
found in Product Bulletin PhosPlus
Cleaning. The BoronPlus™ and PhosPlus sources have
the same dimensions, permitting the same boat design to be
used for both types of sources.
As part of the routine cleaning process,
PhosPlus sources are acid etched to remove any foreign matter
and to expose a pristine surface. As a result, no additional
cleaning is necessary before putting the sources into the
diffusion furnace. If your facility requires in-plant cleaning,
the following procedures are the only ones recommended for
- 15 seconds in dilute acid at
- TP-250 4:1 HNO3
- TP-470 10:1 HF
- 2 minute rinse in fresh DI water
- 1 minute rinse in fresh DI water
- Hold in clean hood until dry
- Store in nitrogen
These procedures are only recommended
for initial cleaning. If the sources become contaminated after
aging, contact your area technical representative for assistance.
Before using PhosPlus sources in production
for the first time, an initialization or aging period is required.
This ensures that all moisture has been vaporized, and it
enables the sources to achieve a constant rate of phosphorus
evolution. Aging should take place at the predeposition temperature
in nitrogen with 25 - 50% oxygen and may last from a few hours
for high temperature processes to as long as 24 hours for
low temperature processes.
Remember that PhosPlus sources are not sensitive to oxygen.
You may, therefore, tailor the oxygen concentration in your
carrier gas to produce the best results for your devices.
Any time PhosPlus sources are exposed to temperatures above
600oC, silicon wafers should be placed between each pair of
sources and at each end of the load.
Appropriate storage procedures should
be followed to protect PhosPlus sources from unnecessary exposure
to moisture. Proper storage will contribute to increased uniformity
and long life of the sources and will improve the electrical
properties of your devices.
For dedicated diffusion tubes, we recommend
that PhosPlus sources be stored in the hot zone of the tube
near 600°C. Sufficient dry nitrogen should flow through
the tube so that no backstreaming will reach the sources.
In those cases where the diffusion furnace is used for other
processing steps, or is somehow not suitable for storing PhosPlus
PhosPlus sources should be stored in an
oven at a temperature above about 200°C. The oven must
be continuously purged with dry nitrogen flowing at a rate
sufficient to prevent room air from entering the storage chamber.
When the sources are stored in room air or accidentally left
in room air for a considerable period of time, sufficient
moisture might be absorbed to affect their performance during
the following run. Their performance can be easily restored,
however, by inserting the sources into the diffusion tube
at the insertion temperature for about 15 minutes. When they
are withdrawn from the tube, the boat is ready for loading
with production silicon.
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