[labnetwork] CMOS Clean in a MEMS Fab Facility

[Martin,Michael David]

Hi,
   I'm trying to track down potential sources of contamination for a CMOS process we are trying to run through our predominantly MEMS fab here at U of Louisville.  Really the only pieces of equipment that are dedicated for CMOS type processes is our RCA bench, an older Technics sputterer, and our oxidation furnace (sort of, see below). So I have a few questions for those of you who have experience with this:
1) For HF etch/dips is there a particular polymer type or brand we should use for our containers that are known to be free of trace metals? Can I avoid PTFE as this is super expensive?
2) When you do litho do you have separate labware for developing? We currently use a Pyrex pan develop which I know is a No-No due to Na and other ions. What sort of container does your lab use (assuming pan develop)?
  2 a) Do you have a dedicated spinner for CMOS?
  2 b) Is there any danger that we are picking up contamination from the amber bottles we are temporarily storing our resists in? What about the polypropylene droppers we are dispensing resists with?
   2 c) What about resist stripping after etching? We typically use a big warm vat of NMP that is shared by all users.  We can also do a plasma etch but I worry about carry over from other folks as none of our plasma etchers are dedicated CMOS.
3) I presume quartz glassware works for my metal (usually aluminum) etching? Do you do regular aqua regia cleans on quartz-ware to scavenge other metals and potential contaminants?
4) We gravitate to peek tipped metal tweezers.  Are they okay? Do you regularly run the tips through a RCA clean?
5) Oxidation furnace: Before trying to transition to CMOS like devices the tube was used with non-RCA cleaned wafers and a pyrex bubbler. After moving to a quartz bubbler with DI water we cleaned the 4" tube with HF.  This is the one I'm really concerned about because I'm guessing that ionic contamination that might have been removed from the surface will readily diffuse back at 1000C.  So should we just bite the bullet and buy a new tube? Any vendor suggestions for a 4" Blue-M?
6) Any other suggestions other than buying a dedicated CMOS tool set?

I did find a very nice document from Stanford that has a lot of practical suggestions found here https://web.stanford.edu/class/ee410/cleaning.pdf )
Krishna Saraswa - Stanford University<https://web.stanford.edu/class/ee410/cleaning.pdf>
6 tanford University araswat 11! Cleaning - Surface Issues Contaminant • Organics – Skin oils – Resist – Polymers • Metals
web.stanford.edu


Thank you in advance,
   Michael

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