Specific Process Knowledge/Etch/Wet Aluminium Etch

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Ething of Aluminium can be done either wet or dry. For wet etching please see below on this page. Dry etching can be done either with the ICP Metal Etch using Chlorine chemistry or with IBE by sputtering with Ar ions.

Wet Aluminium Etch

File:BHF-PolySi-Al-etch.jpg

Wet Aluminium Etch: Positioned in cleanroom 4 to the right in the bench

Wet etching of aluminium is done with two different solutions:

1. H₂O:H₃PO₄ 1:2 at 50 ^oC
2. 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
Link to KBA	see KBA here	see KBA here
Chemical solution	H2O:H3PO4 1:2	PES 77-19-04 77 vol% H3PO4 85% 19 vol% CH3COOH 100% 4 vol% HNO3 70%
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

Dry Aluminium Etch

Our ICP Metal Etch tool allows you to dry etch aluminium.