Specific Process Knowledge/Etch/Etching of Chromium

Etching of Chromium

Fume hood: positioned in cleanroom 2.
Wet Etch of Chromium can take place in a beaker in this fume hood

Etching of chromium is done wet at Danchip making your own set up in a beaker in a fume hood - preferably in cleanroom 2 or 4. We have two solution for this:

1. HNO${}_3$:H${}_2$O:cerisulphate - 90ml:1200ml:15g - standard at Danchip
2. Commercial chromium etch

Etch rate are depending on the level of oxidation of the metal.

How to mix the Chromium etch 1:

1. Take a beaker and add 15g of cerium sulphate.
2. Add a little water while stirring - make sure all lumps are gone.
3. Add water until 600 ml - keep stirring (use magnetic stirring)
4. Add 90 ml HNO${}_3$
5. When the cerium sulphate is completely dissolved (Clear liquid) you can add the other 600 ml of wafer.

Overview of the data for the chromium etches

	Chromium etch 1	Chromium etch 2
General description	Etch of chromium	Etch of chromium
Chemical solution	HNO${}_3$:H${}_2$O:cerisulphate - 90ml:1200ml:15g	.
Process temperature	Room temperature	.
Possible masking materials	Photoresist (1.5 µm AZ5214E)	.
Etch rate	~40-100 nm/min	.
Batch size	1-25 wafers at a time	.
Size of substrate	4" wafers	.
Allowed materials	No restrictions. Make a note on the bottle of which materials have been processed.	.