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We have an Oxford Opal ALD system we use primarily for Al2O3
deposition using TMA. It is a thermal system, no plasma. It is
pumped by a rotary vane pump with a synthetic di-ester oil (A155),
same as originally supplied by Oxford. There is no trap between the
pump and chamber. We are having problems getting consistent good
film quality. We often see films with poor quality, micron-sized
pin holes etc... We think the problem may be related to
contamination of the chamber with back-streaming pump oil as we
often find considerable quantities of oil in the chamber.<br>
Some questions:<br>
1) The A155 oil has a fairly high vapor pressure, is there a lower
vapor pressure oil you can suggest that would stand up to the
process gas that would work with our present pump? (switching to a
dry pump is cost prohibitive at this time, switching to Fomblin may
be possible but would also presumably be expensive as it may require
a pump rebuild or exchange)<br>
2) Can a molecular sieve trap be added in the fore-line without
creating any further problems? If so, can a standard one be used or
must it have some special features (high conductance...)? Are there
other types of traps that would work in this application?<br>
3) With a trap in the line what safety measures are needed, for
instance when venting to air?<br>
4) Are there other issues that could be causing poor film quality?<br>
<br>
Thanks for your help on this, <br>
David<span class="HOEnZb"><font color="#888888"><br>
</font></span>
<pre class="moz-signature" cols="72">--
David J. Frankel - Senior Research Scientist
LASST - University of Maine
5708 Barrows Hall
Orono, ME 04469-5708
207-581-2256
<a class="moz-txt-link-abbreviated" href="mailto:frankel@maine.edu">frankel@maine.edu</a> </pre>
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