Specific Process Knowledge/Etch/Wet Aluminium Etch

Wet Aluminium Etch

Wet etching of aluminium is done with two different solutions:

H $_{2}$ O:H $_{3}$ PO $_{4}$ 1:2 at 50 ^oC
Pre-mixed etch solution: PES 77-19-04 at 20 ^oC

Both solutions are used in the Aluminium etch bath shown to the right. It must be written on which one is in. Solution no. 1 is the most used solution for etching aluminium. Solution no. 2 is primarily for etching aluminium mixed with a small percentage of silicon.

Comparing the two solutions

	Aluminium Etch 1	Aluminium Etch 2
General description	Etch of pure aluminium	Etch of aluminium + 1.5% Si
Chemical solution	H $_{2}$ O:H $_{3}$ PO $_{4}$ 1:2	PES 77-19-04
Process temperature	50 ^oC	20 ^oC
Possible masking materials	Photoresist (1.5 µm AZ5214E)	Photoresist (1.5 µm AZ5214E)
Etch rate	~100 nm/min (Pure Al)	~60 nm/min
Batch size	1-25 wafers at a time	1-25 wafer at a time
Size of substrate	4" wafers	4" wafers
Allowed materials	Aluminium Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist E-beam resist	Aluminium Silicon Silicon Oxide Silicon Nitride Silicon Oxynitride Photoresist E-beam resist