Cl2 Flow Problem

[Jim McVittie]

PQusers,

Over the weekend, several users reported that they could not get the Cl2
flow to go below 2.5 sccm. This is a problem since the standard GaAs etch
process runs with a Cl2 flow of 1.5 sccm. I traced the problem to the Cl2
pressure regular, which was at 25 psi rather than the standard 10 psi. The
pressure was reduced to 10 psi but it creeped back to 25+ psi after a
short time. This is a typical problem from for a contaminated Cl2 line. I
suspect insufficent purging was done at some point when the Cl2 cylinder
was changed. The solution is to replace the regulator and to increase the
number purges during cylinder changes.

Ted Berg said that a new regulator could take 3 wks to come in. It is
possible that the Cl2 line may have to be shut down until the new
regulator is installed.

     Jim 

--------------------------------------------------------------
Jim McVittie, Ph.D.    			Senior Research Scientist 
Allen Center for Integrated Systems     Electrical Engineering
Stanford University             	jmcvittie at stanford.edu
Rm. 336, 330 Serra Mall			Fax: (650) 723-4659
Stanford, CA 94305-4075			Tel: (650) 725-3640