I have some water-soluble crystalbond that is attached to silicon and, because of some overheating (to about 150 Celcius) during a final processing step, the crystalbond seems to have charred (white/grayish colour, see photo at the bottom) and is no longer dissolvable in water. Since this silicon is important and cannot be replaced, I really need to find a way to chemically remove this overheated crystalbond residue without using abrasives that could scratch of the thin SiO$_2$ coating on silicon.
Looking at the MSDS (see here), crystalbond is composed of the following
- 97% Nonylphenol Polyethylene Glycol Ether(127087-87-0) EC-No. 500-315-8
- 3% Polyethylene Glycol(25322-68-3)EC-No. 500-038-2
My question is: does anyone have any ideas for what crystalbond decomposes into around 150 C and how one could remove this overheated crystalbond residue?
Things I have tried (unsuccessfully)
- Hot DI water (in a cup, and in a ultrasonic bath)
- "Piranha" etch (asked a lab friend to do this, too scary for me!!)
- Photoresist remover (lab friend also tried this)
- Dunking in LN2
- Putting on a hot plate at 225C for about 24 hours
- Burning under a 1100C torch for about 30 seconds
Any bright ideas, especially from organic chemists? All I can say is: damn this stuff doesn't want to come off.
Some examples of the residue below.