LTO gas source

John Shott shott at stanford.edu
Wed Nov 21 14:06:13 PST 2007


Bei:

I believe that the tylanbpsg tube uses 100% silane as the silicon source 
and a mixture of 15% PH3 in a balance of silane as the source of 
phosphorus for the doping.  You may think that it's a bit strange to use 
silane as a "carrier gas".  The thinking behind this is that, because 
phosphine is so toxic, you are actually better off mixing it with silane 
(which is pyrophoric and burns immediately in contact with air) because 
a small leak of the PH3/SiH4 mixture will tend to burn and convert the 
PH3 into less toxic P2O5.  Plus, either by virtue of seeing the powder 
build-up that results from the reaction of PH3/SiH4 with air, that you 
are more likely to visually spot a small leak.

Let me know if you have any other questions,

John




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