Yes,
       From an old timer who used Piranha in England in the 60's to =
clean photo resist. It works like crazy, is an exothermal reaction and =
the fumes usdto eat my wooden etch benches.  When plastic etch benches =
arrived we felt better but ignired what the fumes may be doing to =
operators.  It is a 50/50 mixture of H2SO4 and H2O2.  It is exothermal =
boils like crazy and eats any organics.  it needs safe handling and is =
expensive to keep buying chemicals and also it is expensive to get rid =
of chemicals.
       Oxygen plasma is contained in a vacuum chamber but it serves the =
same purpose it wil eat any organic, usually in just about the same time =
frame as Piranha.  Down side it is a line of sight process and the =
plasma energy depletes as the sqaure of the distance from the elecrtrode =
or microwave diode producing the energy.  The shape of the plasma =
generator and the chamber shape is important.  The frequency does not =
matter it is a question of selecting the right frequency for the =
chamber.  For microwave plasma usually 2.45 Gh/z, beamed high energy =
into a small chamberfor resist stripping.  For Inductive plasma usually =
13.45 or 13.56 Mh/z and a round chamber with the inductive coil wraper =
arround the chamber. The energy is obvously radial and the centre of the =
chamber gets cleaned about 2 times longer than the outside edges.  =
Capacitive typically 40 to 50 Kh/z and flat electrodes producing plasma =
and flat shelves for the parts.
      Benefits of plasma systems are no dangerous fumes to worry about =
and very low chemical costs.  Typical unit will run on one cylinder of =
gas about $250.00 for 3 months.  Also a plasma unit can use other gas =
plasmas for selective etching of specific components.  Down side is the =
expense of the initial purchase.
      Ozone plasma is an attempt to produce an organic eater without the =
expense of a plasma unit.  It works but is very slow as the available =
energy is low.  A direct example I can quote is a 1KW microwave resist =
stripper with the wafer at 150 degrees C takes 35 seconds to strip a =
10,000 Anstrom layer of resist.  A 1 KW deep UV ozone generator takes =
nearly 4 minutes with the wafer at 350 degrees C.  As the resist =
stripping action follows the laws of physice and the reaction is faster =
at higher temperature it is obvious the ozone generato has less energy.  =
It can also only produce ozone and can not do selective chemical etching =
with other activated gasses.
       For more informaon contact me directly, I can bore you for hours =
with lots of technical details.  Bill Moffat

________________________________

From: [email protected] on behalf of Jauniskis, Linas
Sent: Fri 5/12/2006 2:49 PM
To: [email protected]
Subject: [mems-talk] relative virtues of organics cleaning processes



Hello all,

Could anyone comment on the relative virtues of organic cleaning
processes like piranha etch, oxygen plasma and uv/ozone?

Do they all accomplish the same thing at the end of the day and your
choice is then driven by materials and process compatibility issues; or
is one more effective than the others; or is each most effective on
different types of organic contaminants?

Thanks in advance for your insights.

Linas.