Lab and Coral NameTRL / photo-wet-Au
ModelSemifab WPS-800
SpecialistDavid Terry    (Paul Tierney)
Physical Location4F Main-North
Process CategoryWet
Material KeywordsPolyimide, Other Polymers, Photoresist, EBL Resist, Developer, Solvents
Sample Size8" Wafers, 6" Wafers, 4" Wafers, 7" Photo Plates, 5" Photo Plates, Pieces
Keywordssingle wafer, manual load, multiple pieces, both sides of sample, isotropic etch, manual operation
The photo-wet-Au is a fume hood for solvent work. It has a sash that is fixed height (though adjustable), and contains a sonicator that can be used to heat solvents as well as provide ultrasonic agitation. The sonicator is mostly used un-heated, to solvent clean samples and accellerate liftoff processes. The most common solvent cleaning is a sequence of Acetone, Methanol, Isopropyl followed by a nitrogen blow-dry. For standard liftoff, the sonicator will often pulverize the metal that was lifted off, and small metal particles can re-deposit on the sample. These can be removed by sonicating in a fresh and clean acetone bath. Sonicating can also help to clean up the plastic dishes used in the photo area.

Best forSolvent cleaning of samples, sonicating.
LimitationsWorksurface can be limiting both in size and ease of access.
Caution withDo NOT pour solvents into the sink. Make sure sonicator water fill level is sufficient. Solvent waste can be disposed of in the collection bottle located in the neighboring SU8 hood. Never leave the area when heating solvents in the sonicator, and know the temperature limits for the solvent in use.
Machine Charges (academic rate)no charge

Wet ProcessingRules and guidelines for wet processing

Etch rates part 2Berkeley etch rate paper
Process Matrix Details

Been in the ALDSamples that have been in any of the ALD systems
Pyrex SubstratesPyrex substrates can be a concern due to high sodium content, which contaminates CMOS frontend tools
III-V SubstratesAny III-V substrates, e.g. GaAs, GaN, InP, and so on. Note though that many common III-V substrates will also carry the Au flag, but there are some GREEN III-V substrates.
Germanium on surfaceSamples with germanium on the surface (typically grown films)
Germanium buriedSamples with germanium buried below a different film
PiecesWafer pieces may not be handled by the equipment, and are harder to thoroughly clean - preventing them from running in certain tools.
Gold or RED color codeRED color code substrates. These are gold-contaminated or have been processed in gold contaminated tools. Gold and other metals can contaminate silicon devices (GREEN color code) and have to be separated.
Any exposure to CMOS metalIf the sample had ever seen a CMOS metal (or a tool that accepts CMOS metal), then some frontend tools could be contaminated by this.
CMOS metal on surfaceCMOS compatible metals exposed on the surface. These are Al,Ni,Pt,Ti,TiN. Other metals such as Au are *NOT* part of this.
CMOS metal buriedCMOS compatible metals covered entirely by a different material. These are Al,Ni,Pt,Ti,TiN. Other metals such as Au are *NOT* part of this.
Been in the STS DRIEThe DRIE etch leaves behind polymer residues on the sidewall ripples, which can be a contamination concern for some tools.
Been in the SEMA sample viewed in the SEM must have used the appropriate chuck to avoid cross-contamination
Been in the Concept1The Concep1 deposits dielectrics on GREEN wafers, however it also accepts metal and there can be cross-contamination for diffusion area
Has PhotoresistSamples with photoresist cannot be exposed to high temperatures, which is typical in deposition tools. Outgassing can be a concern.
Has PolyimidePolyimide is a very chemically resistant polymer, and can tolerate higher temperatures but cannot be exposed to typical PECVD deposition temperatures or diffusion furnaces. Outgassing can be a concern.
Has Cured SU8Not fully cured SU8 residues can heavily contaminated plasma chambers or destroy other user's samples, but fully cured SU8 is permitted in certain tools.
Coming from KOHAfter a KOH etch, the samples must receive a special clean because the K ions are highly contaminating to CMOS frontend tools
Coming from CMPAfter a CMP, the samples must receive a special clean, because the slurry residues otherwise introduce contamination and particles.

Not Allowed
Ever been in EMLSamples from EML are never permitted to return to ICL or TRL

For more details or help, please consult PTC matrix, email, or ask the research specialist (David Terry)