Projects»
micro resist technology GmbH
Projekt Number
16SV871/2
funded by the Bundesministerium für Bildung und Forschung
(BMBF – German Ministry for Education and Research)
Projectduration
1st April 1998 – 30th June 2001
Project objectives
Building on process developments for UV lithography patterning
of thick photoresists and electroforming of the patterns generated
begun in approx. 1995 (technologies also called “rapid
prototyping”, “3D microforming” and “UV-LIGA”),
this collaborative project was to test the feasibility of these
processes for the efficient production of application-led microcomponents.
The work of the consortium concentrated on the production of
microcoils which were to be used as magnetic actuators in the
printing heads of high-performance ink-jet printers.
The contributions of the micro resist technology GmbH subproject
ranged from developing the process for thick photoresists for UV
lithography (layer thicknesses from ~10 µm to the >1 mm
range) to demonstrating their fitness for the production of microparts.
Project benefit
The “Mikrostruk” project created the principles for lithographic
work with highly viscous positive photoresists based on DNQ/Novolak
(currently: ma-P 1275, ma-P 1275 HV), for epoxy resin-based resists
(EpoCore/EpoClad, MCC SU-8 resists) as well as for the current ranges
of production services for thick resists which still apply today.
Outstanding results from micro resist technology GmbH in
the “Mikrostruk” project included the process developments
for UV contact lithography for DNQ/Novolak positive resists for patterning
layer thicknesses up to approx. 50 µm with aspect ratios (meaning
the ratio of the height to the width of a structure) of up to six
and for SU-8 epoxy resists at a layer thickness of 40 µm and
200 µm with aspect ratios of up to ten. The technical practicality
of the lithography processes developed was proved by the production
of magnetic copper actuator coils by the project consortium in the
course of this collaboration (see Figures 1 and 2), with approx.
20 µm thick resist layers being successfully patterned with
an aspect ratio of up to approx. five. To provide evidence of lithography
performance with 200 µm-thick SU-8, we independently developed
and patterned a capacitative acceleration sensor to demonstrate the
technology (see Figures 3 and 4). Experimenting with the application
of SU-8 as an electrical insulating layer under the coil windings,
we furthermore created the principles for subsequent continued development
of epoxy resists for use as functional materials in microsystems
(e.g. wafer-level packaging (WLP) solutions).
Outlook
Thick photoresists are now a permanent and growing component of
the micro resist
technology GmbH. product portfolio. They are used
in a wide variety of microtechnologies in the transitional area
between microelectronics and precision engineering where structures
with maximum precision and dimensions between a few microns (microelectronics)
and a few millimetres (precision engineering) are required: e.g.
for the electroforming of metal microcomponents in LIGA processes
such as those developed directly in the “Mikrostruk” project,
for special lift-off applications, for plasma etching processes
in which very high etch depths and aspect ratios are to be achieved
and, in the case of SU-8, for applications in which the lithographical
resist patterns in microsystem technology have a function of
their own (e.g. for microfluidic and lab-on-chip applications,
for packaging solutions or when the resist patterns are used
as dies for imprint processes).
Important publications
Mischke H., Gruetzner G., Shaw M., Plasma Etching of Polymers like SU-8 and BCB, Proceedings of SPIE, Volume 4979, Micromachining and Microfabrication Process Technology VIII, editors John A. Yasaitis, Mary Ann Perez-Maher, Jean Michel Karam, January 2003, pp. 372-381
Engelke, R., Engelmann G., Gruetzner G., Heinrich M., Kubenz M., Mischke H., Complete 3D UV microfabrication technology on strongly sloping topography substrates using epoxy photoresist SU-8, Proceedings of the 29th International Conference on Micro and Nano Engineering (MNE 2003), editor J. R. A. Cleaver, Microelectronic Engineering, vol. 73-74 (une 2004), pp. 456-462
Engelke, R., Engelmann G., Gruetzner G., Heinrich M., Kubenz M., Mischke H., Complete 3D UV microfabrication technology on strong sloping topography substrates using SU-8, 29th International Conderence on Micro and nano Engineering MNE 2003, 22.-25. September 2003, Cambridge, U.K. (Poster)
Engelmann, G., Engelke, R., Heinrich M., Gruetzner G., Wolf J., Reichel H., Fabrication of high aspect ratio microstructures on strong sloping topography substrates, Micro System Technologies 2003, 7.-8. Oktober 2003, München (Vortrag)
Figure 1: Copper coil (~13 µm high; conductive track widths and spaces between conductive tracks both 4.5 µm) on a layered stack consisting of 10 µm-thick NiFe baseplate (visible as a pale substrate) and 2 µm-thick insulating layer made of patterned SU-8 resist (dark substrate). UV contact lithography was performed with a 20 µm-thick DNQ/Novolak positive resist.
Figure 2: Copper coil (~15 µm high; conductive track widths and spaces between conductive tracks both 4.5 µm) on a layered stack consisting of 10 µm-thick NiFe baseplate (visible as a bump under the coil, exposed in the centre of the coil) and 2 µm thick insulating layer made of patterned BCB polymer. UV contact lithography was performed with ~22 µm-thick SU-8 epoxy resist.
Figure 3: Development stages in the capacitative acceleration sensor to demonstrate thick layer-building technology (top left: draft drawing; top right: 200 µm-thick SU-8 photoresists patterned with 3D UV lithography; bottom: formed nickel structure following removal of resist by plasma chemistry)
Figure 4: ~200 µm deep SU-8 resist mould patterned by UV lithography (left: overview, right: detail). An aspect ratio of ten/10 was achieved with 20 µm-wide openings in the resist (see arrow in right-hand image).
