Slide 1

Report
Development and Characterization of an
Integrated Thick Resist Film Processing Tool
D.
1
Goustouridis ,
1
Raptis ,
2
Valamontes ,
I.
E.
I.
1
1,4
N. Tsikrikas , M. Chatzichrisitidi
3
Karanikas ,
1Institute
4
of Microelectronics, NCSR ‘Demokritos’, Athens, 15310 Greece
2 Department of Electronics, TEI of Athens, 12210 Aegaleo, Greece
3 Datec Electronics S.A. Dorieon 28, Athens 11852, Greece
Chemistry Department, University of Athens, Zografou 15771, Greece
E-mail: [email protected]
Introduction:
In micromachining – microsystems applications the patterning of resist films with thickness of several tens of microns is
common. The processing conditions of such thick resist films are quite different from the ones used in mainstream microelectronics. For example
in the case of SU-8 the Post Apply Bake (PAB) should be done in two different temperatures. In this direction several processing tools have been
developed, e.g. [1]. In addition, for the preparation of thick films, more than one spin coating steps are required.
In the present work a thick resist film processing tool capable to resist application, PAB and PEB is presented and applied in case of the
UV-patterning of thick epoxy based resist films.
Spreader set-up
Results
Wafer Uniformity
Spreader
Computer
software
24.5μm 24.9μm
99.7μm
100.6μm 99.3μm 100.1μm
102.3μm 101.8μm 102.8μm
24.6 μm
Photo of the spreader set-up
a)
Casting Solvent Evaporation
Int. Signal (a.u)
1200
Two epoxy based CARs capable to form high viscosity solutions were
investigated.
A) TADEP resist [2,3] with Propylene Glycol Methyl Ether Acetate
(PGMEA) as casting solvent and
B) SU-8 2015 with Gamma Butyrolactone (GBL).
TADEP was used for 25μm thick films and SU-8 for 100 μm thick
films (this SU-8 formulation is used for max. 40μm thick films with
spin coating).
Processing Conditions
Micrometers
Adjustment
Exposure (365nm)
PEB
Development
Final Thickness
TADEP
60°C/30min +
100°C/60min
SU-8
65°C/5min +
95°C/20min
100 μm
200 μm
1100 mJ/cm2
95°C/8min
250 mJ/cm2
65°C/2min +
95°C/10min
PGMEA/12min
99.4 μm
TMAH/10min
25.6 μm
140
1000
800
120
600
400
40
60
80
100
Time (s)
1000
Experimental procedure
PAB
1200
80
60
800
SU-8 2015
1200
1000
90
800
600
60
1300
100
400
1200
40
20
600
0
1000
2000
3000
4000
5000
0
6000
120
Temperature (oC)
TADEP
1400
160
1400
200
80
1100
60
1000
300
0
450
Temperature (oC)
Blade
Inside the spreader
c)
Wafer uniformity for a) TADEP resist b, c) SU-8 resist. The wafer
uniformity maximum deviation is 1.4% and the spreader repeatability
is 1.9%
Interferometer
module
Wafer holder
and hot plate
101.9 μm
b)
Temperature (oC)
Leveling
mechanism
100.6 μm
Int. Signal (a.u)
Computer
communication
port
24.6μm
97.9μm
Int. Signal (a.u.)
Temperature
controller
24.3μm
Int. Signal (a.u.)
Leveling
mechanism
30
600
Time (sec)
0
200
400
Time (s)
600
800 1000 1200 1400 1600 1800 2000
Time (sec)
TADEP resist has PGMEA (b.p. 146°C) as casting solvent whereas SU-8
has GBL (b.p. 205°C). TADEP shows a high evaporation in the first 5min
(~100nm/sec), then the evaporation rate decreases and when the
temperature reaches 100°C the rate initially increases and then is very
low. SU-8 has a slower evaporation rate in the beginning (~30nm/sec) at
65°C that decreases with time (~12nm/sec) and then it increases again
with temperature elevation (~35nm/sec) and after 3min at 95°C it is
very low.
Lithographic Results
TADEP resist. Top-down optical
micrograph. Line-width is 5 μm
and the resist thickness is 25 μm.
SU-8 resist. Top-down optical
micrograph. 10 μm squares and
circle diameter. The resist
thickness is 100 μm.
Conclusions: In the present work, a thick resist film processing tool capable of resist application and PAB was presented and applied in case
of the UV-patterning of thick resist films. This particular tool could be equipped with UV-exposure capability in the future allowing the complete
processing of the thick resist films except the development-drying steps that allowing the penetration of micromachining technology in research
labs without easy access in conventional lithography equipment.
References
1. G. Bleidiessel, G. Gruetzner, F. Reuther, S. Fehlberg, B. Loechel, A. Maciossek Microelectron. Eng. 41-42 433(1998)
2. M. Chatzichristidi, I. Raptis, P. Argitis J. Everett, J. Vac. Sci. Technol. B 20, 2968 (2002)
3. M. Chatzichristidi, E. Valamontes, P. Argitis, I. Raptis, J.A. van Kan, F. Zhang, F. Watt Microelectron. Eng. 85 945 (2008)
Acknowledgments:
This work was partially
financially supported by Greek Secretariat for
Research & Technology through the 05-NONEU467 (Greece-Singapore project).

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