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Wet ething of aluminium can be done using many different acids and bases. Using dilute phosphoric acid gives reasonably good control and compatibility with photoresists. Etching with dilute phosphoric acid is suitable for etching pure aluminium. If the aluminium is alloyed with other metals, other etchants may be better suited. Previously, aluminium with 1,5% silicon was used at DTU Danchip. This alloy is no longer in use at DTU Danchip but a suitable etchant (PES 77-19-04) for this alloy is included below.

Wet Aluminium Etch

Aluminium Etch bath located in left side of Wet bench 05 in cleanroom D-3

Wet etching of aluminium is done with two different solutions:

H₂O : H₃PO₄ (1:2) at 50^oC
Pre-mixed etch solution: PES 77-19-04 at 20^oC

The first solution is always available ready made in the Aluminium Etch bath. The second solution can be mixed manually or bought pre-mixed and ready for use. Please contact DTU Danchip if you need to use the PES 77-19-04 etch mixture. Since it is used only very rarely it may have to be ordered when needed. The table below summarizes possibilities and parameter for the two etch mixtures.

Comparing the two solutions

	Aluminium Etch	Etch with PES 77-19-4
General description	Etch of pure aluminium	Etch of aluminium with 1.5% Si
Location	Aluminium Etch bath inside Wet Bench 05 in D-3	Beaker in Fumehood 01 or 02 in D-3
Link to SDS	SDS in Kemibrug	SDS: Not available
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 6" wafers	Any size that fits in beaker
Allowed materials	See the Cross Contamination Sheet for Aluminium Etch bath	Any material allowed in cleanroom

@@ Line 13: / Line 13: @@
 Wet etching of aluminium is done with two different solutions:
-# H<sub>2</sub>O:H<sub>3</sub>PO<sub>4</sub>  1:2 at 50 <sup>o</sup>C
+# H<sub>2</sub>O : H<sub>3</sub>PO<sub>4</sub>  (1:2) at 50<sup>o</sup>C
-# Pre-mixed etch solution: PES 77-19-04 at 20 <sup>o</sup>C
+# Pre-mixed etch solution: PES 77-19-04 at 20<sup>o</sup>C
-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.
+<br>
+The first solution is always available ready made in the Aluminium Etch bath. The second solution can be mixed manually or bought pre-mixed and ready for use. Please contact DTU Danchip if you need to use the PES 77-19-04 etch mixture. Since it is used only very rarely it may have to be ordered when needed. The table below summarizes possibilities and parameter for the two etch mixtures.
-'''The user manual and contact information can be found in LabManager:'''
-<!-- remember to remove the type of documents that are not present -->
-[http://labmanager.dtu.dk/function.php?module=Machine&view=view&mach=381 Al-etch info page in LabManager]
 ==Comparing the two solutions==
@@ Line 36: / Line 33: @@
 !General description
 |Etch of pure aluminium
-|Etch of aluminium + 1.5% Si
+|Etch of aluminium with 1.5% Si
 |-