Thanks to all who replied for their help. Please find below the most
relevant replies (some editing to prevent respondants getting unwanted
mail),
Best regards,
Karen Smith
MST consultant
Coventry, UK
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Roger Shile:
Olin makes something called 777 Etch, which contains acetic acid, ammonium
fluoride, ethylyne glycol, and water. It is intended for use in etching
SiO2 to open up bond pads. It supposidly doesn't attack the aluminum as HF
based etches do.
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BobHendu:
Contact xxxxx and ask him about formulations for Passivation etchants. I
believe they call it pad etch is that you uncover the bonding pads on IC's
with this etchant. I am not sure but I think we at one time used a
formulation of ammonium fluoride+di water+acetic acid. This particular
formulation prevented the grounding pads from overetching or staining the
aluminum underneath the passivation oxide.
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Andy Chen:
Are you still looking for some information of pad etching. Pad etching
is a special BOE with low etching rate to aluminum. Let me know if you
still want.
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Mac McReynolds:
In the forgotten past of circuit fabrication on si, "Pad" Etch was used to
remove the passivation layer (typically P or B doped Low Temp Oxide-also
known as PLTO) from the aluminum bonding pads. Typically it contained NH4F
and Acetic acid, with or without surfactants. HF solutions damaged the Al
surface. Many lifetimes ago I bought it from KTI chemicals. I think ATMI
on the East Coast still offers it.
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Ken Kwon:
Try looking under http://www.ashchem.com/home/index.asp it's
better to call in and ask for the MSDS then sending emails. Regarding the
Pad Etch, I think it's better to use buffered oxide etch than for the pad
etch. Is there a reason why you cannot use BOE?
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Original Question:
I have seen several references to "Pad etch" in micromachining literature -
specifically relating to removal of a sacrificial oxide layer.
I have asked several chemical suppliers and checked in several references to
no avail (I believe it is a specialisat formulation (HF?) by Ashland, but
can find no reference to it on their MSDS?).
Can anyone help me with what it actually is & who supplies it?
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