Specific Process Knowledge/Etch/Etching of Gold

Etching of Gold

Wet Gold Etch: Done in the fumehood positioned in cleanroom 2

Etching of Gold is done wet at Danchip making your own set up in a beaker in the fumehood. We have two different solutions:

1. Iodine etch: KI:I$_{2}$:H$_{2}$O - 100g:25g:500ml - standard at Danchip. Can be used with AZ resist as mask.
2. Aqua Regia (Kongevand): HNO$_{3}$:HCl - 1:3 - A very strong acid witch will etch most metals and are therefore used when you wish to remove all the gold from your wafer. you have to be very carefull when you work with Aqua Regia (Kongevand) It can generate nitrous gases witch are very toxic!!

Comparing the two solutions

	Iodine based gold etch	Aqua Regia (Kongevand)
General description	Etch of pure Gold with or without photoresist mask.	Etch of pure Gold (as stripper).
Chemical solution	KJ:J$_{2}$:H$_{2}$O (100g:25g:500ml)	HCl:HNO$_{3}$ (3:1)
Process temperature	20 oC	20 oC
Possible masking materials	Photoresist (1.5 µm AZ5214E)	Unmasked - used as a stripper
Etch rate	~100 nm/min	~(??) nm/min - fast etch
Batch size	1-5 4" wafers at a time	1-5 4" wafer at a time
Size of substrate	2-6" wafers	2-6" wafers