If I understand you then you have one gas for CF4 and one for O2. You can order your gas already mixed in the bottle with CF4+6% Oxygen, then you can run He in the other. Gas flow should be 40-60 sccm CF4/O2 and 100 sccm He. The helium helps to keep the photoresist from burning and helps to make the plasma uniform over the whole wafer surface. I hope this helps. Bob Henderson ----- Original Message ----- From: "alim polat"To: "General MEMS discussion" Sent: Thursday, February 07, 2008 7:09 AM Subject: Re: [mems-talk] Dry etch to get patterned SiO2 hard mask > It looks like only the PECVD machine has the gas pipe that He runs > through. I haven't checked if I can run this pipe through RIE. What > would be the recipe if I can run He through RIE machine. On RIE CF4 > looks like doesn't come with O2, but there is O2 gas pipe running > through RIE. So I don't quite get CF4+O2 at 6% means. Does that mean I > can run CF4 and O2 gases run in the chamber together? > Alim Polat > Linkoping University > Sweden