Yun, I do not know the vapor pressure of CCl4 but I assume it is low. If you do not have enough head pressure in your cylinder the gas will not flow. One way to overcome this problem is to heat your cylinder. The only problem with this method is the gas lines also have to be heated and to a temperature higher than the cylinder or the gas will condense back into a liquid. If you can flow the CCl4 without the CF4 you may try to turn down the CF4 flow and or pressure. If the CF4 and the CCl4 are on the same low-pressure manifold the CF4 can starve off the CCl4 Best regards, Glenn Silveira -----Original Message----- From: Yun Xi [mailto:xi@ENGR.UARK.EDU] Sent: Wednesday, June 30, 2004 7:31 PM To: mems-talk@memsnet.org Subject: [mems-talk] Trouble on CCL4 Hello, We used mixture of CCL4 and CF4 to do gold dry etch, but recently it doesn't work. It seems CCL4 run out. We contacted Scott Specialty Gases to order CCL4. The company told us their cylinder will not have a diptube or pressure pad and we have to invert the cylinder to reomve the product. We know that means CCL4 is liquid phase in cylinder. When we took our old CCL4 cylinder out from system, we found there is stiil liquid inside. We let the cylinder upside down and connectd to system again, liquid CCL4 come out and MFC out of control. We would like to know how to deal with this situation to have gas phase CCL4? We are appreciated your help. Yun