Specific Process Knowledge/Etch/Wet Gold Etch

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Ething of Gold can be done either wet or dry. For wet etching please see below on this page. Dry etching can be done with IBE by sputtering with Ar ions.

Etching of Gold

Wet etching of gold is done making your own set up using a beaker in a fumehood. You can see the APV here.

We have two different solutions:

Iodine etch: KI:I₂:H₂O - 100g:25g:500ml - standard at Danchip. Can be used with AZ resist as mask.
Aqua Regia (Kongevand): HNO₃:HCl - 1:3 - A very strong acid which will etch most metals and are therefore used when you wish to remove all the gold from your wafer. You must be very careful when working with Aqua Regia (Kongevand). It can generate nitrous oxide gases which 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).
Link to safety APV	see APV here.	see APV here
Chemical solution	KI:I₂:H₂O (100g:25g:500ml)	HCl:HNO₃ (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	Any size and number that can go inside the beaker in use	Any size and number that can go inside the beaker in use
Allowed materials	No restrictions when used in beaker. Make a note on the beaker of which materials have been processed.	No restrictions when used in beaker. Make a note on the beaker of which materials have been processed.