Aluminum Dry Etching
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Created:
Revision #:
Revision date:
Matthieu Nannini
Vito Logiudice
September 19, 2006
1
Summary:
This document describes the recipe used for aluminum etching using the Applied Materials P5000 reactive ion
etcher. A soft mask made of resist is used to prevent the aluminum from being etched away. This soft mask is
obtained using the 1.4µm photolithography process (refer to reference document). The recipe given in this
document is a starting point for anyone who would like to use it in a process. This means that the recipe is not
perfect yet and needs to be further optimized.
The recipe name in the AM 5k is Nanotools Alu Etch and the parameters are the followings:
Time [s]
Pressure [mTorrs]
Power [W]
B-Field [Gauss]
N2 [sccm]
Cl2 [sccm]
1.Stable
30
10
0
0.0
50
0
Parameter
Aluminum etch rate
Uniformity (6”)
Oxide selectivity
Resist selectivity
2.OX Etch
45
10
600
0.0
50
0
3.Stable
15
17
0
0.0
25
35
4.Main Etch
120
17
200
0.0
25
35
5.Sec.Etch
60
17
200
70.0
25
35
6.R-Down
60
OPEN
25
0.0
25
0
Value
~1000 Å/min
Check the graphics in section 5.1
Not measured but should be ~10:1
~ 1:1
*The etch rate can vary due to the loading effect: the etch rate will vary as a function of the ratio of the
surface area being etched vs. the area that is protected by the photoresist.
** For extensive information about this recipe, check Martin Aguilar report on Aluminum coating and etching.
1/4
116105251
© McGill University
Nanotools Micromachining Facility
No reproduction permitted
Table of content
1
2
3
4
5
Associated Documents & References
Equipment Used
Verifications Prior to Processing
Recipe description
Measurements & Statistical Process Control
5.1
Measurements
6 Record of Revisions
2
2
2
2
3
3
4
1 Associated Documents & References



MSDS for Cl2, N2.
Applied Material 5k user manual
Rules and procedures of cleanroom
2 Equipment Used

Applied Material 5k
This equipment must be reserved through the online software: Resource Scheduler.
If you need to be assisted by technicians, check their availability before reserving the equipment. Users have to
go through regular training before using this equipment alone.
3 Verifications Prior to Processing


Verify that the recipe in the tool is identical (step by step) to the one described here.
It is always a good practice to descum your wafer(s)/sample(s) in the TePla O 2 Plasma to remove resist
residues in the valleys of your pattern. Refer to the TePla user manual for more details on the descum
recipe.
4 Recipe description
When etching aluminum films, the native oxide (Al 2O3) formed at the film surface has to be etched first to
expose aluminum itself to the plasma. In this recipe, the native oxide is removed using N2 physical sputtering:
indeed, the oxide is bombarded by N21-3+ ions at high power. The following step uses Chlorine (Cl 2) to remove
the aluminum.
Time [s]
Pressure [mTorrs]
Power [W]
B-Field [Gauss]
N2 [sccm]
Cl2 [sccm]
Step1:
Step2:
Step3:
Step4:
Step5:
Step6:
1.Stable
30
10
0
0.0
50
0
2.OX Etch
45
10
600
0.0
50
0
3.Stable
15
17
0
0.0
25
35
4.Main Etch
120
17
200
0.0
25
35
5.Sec.Etch
60
17
200
70.0
25
35
6.R-Down
60
OPEN
25
0.0
25
0
stabilization of the gas flow(s) for the native oxide removal
native oxide removal using N21-3+ ions bombardement
stabilization of the gas flow(s) for the aluminum etching step
Aluminum etching step
second aluminum etching step to improve uniformity across the 6” wafer
RF rampdown to allow particle in the plasma to be pump away before shutting it off.
2/4
116105251
© McGill University
Nanotools Micromachining Facility
No reproduction permitted
Since the recipe uses chlorine, it is not selective on silicon thus we recommend to have a thin oxide layer
underneath your aluminum film to allow a precise control of the etch stop.
It has been observed also that depending on the time elapsed between the coating and the etching, results can
be different due to the continual growth of the native oxide. Not data have been gathered yet.
5 Measurements & Statistical Process Control
5.1 Measurements
To qualify the recipe, resist and aluminum etching measurement have been taken using the Tencor P1
profilometer. The data (etch rates) are represented as a function of distance-from-center because we did not
manage to get a very good uniformity across the wafer.
Etch rate as a function of power
Resist selectivity as a function of power
Resist selectivity as a function of Cl2 flow
3/4
116105251
© McGill University
Nanotools Micromachining Facility
No reproduction permitted
6 Record of Revisions
Rev. 1
September 19, 2006
First Edition
4/4
116105251
© McGill University
Nanotools Micromachining Facility
No reproduction permitted