LIGA Technology
By: Phillip Ahn and Andrew Schnirel
What is LIGA?
z LIGA is a process in IC fabrication which involves
lithography, electroplating, and molding on a given
substrate.
z LIGA allows structures to have heights of over 100 µm
with respect to the lateral size. LIGA fabricates High
Aspect Ratio Structures (HARMST).
z The ratio between the height and the lateral size is the
aspect ratio. (e.g. 100:1)
Characteristics of LIGA
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Any lateral shape is possible.
Structural height is above 1mm.
Smallest lateral size is 0.2 µm.
Aspect ratios can range up to 500.
Surface roughness is typically small ~ 30nm.
Materials other than Si can be used.
Processes of LIGA
z A sacrificial layer pattern is deposited on the substrate.
Ti, Al, Cu, or Cr is usually used.
Processes of LIGA
z The structure is covered with a thin layer of plating. Ni or
sputtered Ti/Ni is commonly used.
Processes of LIGA
z A thick layer of photoresist called PMMA is added to the
surface.
Processes of LIGA
z A mask is aligned and X-ray or UV light from a
synchrotron radiation source is exposed to the
photoresist.
Processes of LIGA
z The area exposed by X-ray or UV light is filled with
electroplated metal. Ni is commonly used.
Processes of LIGA
z The remaining photoresist is removed.
Processes of LIGA
z The plating base is removed.
Advantages and Disadvantages of LIGA
z Advantages
{Allows material other than Si to be used.
{Better precision and low surface roughness.
{Can fabricate arbitrary cross sections.
{Mass production of parts is possible.
{Can use polymers and ceramics.
z Disadvantages
{Synchrotron radiation source is not widely available.
{Results may vary depending on the deposition method
used. (e.g. thermal evaporation vs. plasma sputtering)
Applications of LIGA
z Fabrication of actuators and mechanisms
{Large structural heights allow actuators to generate
more torque.
{Precision of LIGA allow shafts, contacting parts,
bearings, and gears to have with minimal friction. Also
produces micro-sized sensors.
{Surface area dependent structures such as mass
spectrometers and switches have better sensitivity.
{Height of coils and springs allows greater stiffness and
rigidity.
Applications of LIGA
z Fabrication of spinnerets
{Spinnerets have smooth surfaces and fixed geometries
to produce textile fiber efficiently.
{High aspect ratio allows micro-sized spinneret
capillaries to function properly.
Applications of LIGA
z Fabrication of optical components
{Selectivity of material allows mass production at a low
cost.
{Components such as micro lenses, mirrors, and filters
benefit from low surface roughness to reduce scattering.
{Precision and height allow applications in wave guiding
structures
Devices with LIGA components
z Mechanical gear systems
{Capacitive Accelerometer
{Microgyroscope
{Micromotors
{Fluid Control Valves
Devices with LIGA components
zOptical
components
{Microspectrometer
{Distance Sensor
{Polarization Sensor
Devices with LIGA components continued
z Bio-Medical Engineering
{Drug delivery Systems
{Cancer Biomarking
References
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C.K. Malek, V. Saile,
“Applications of LIGA technology to precision manufacturing of high-aspect-ratio micro-components and –systems:
a review,”
Microelectronics Journal, vol.35, pp. 131-143, 2004
X. Jing, D. Chen, D. Fang, C. Huang, J. Liu, X. Chen,
“Multi-layer microstructure fabrication by combining bulk silicon micromachining and UV-LIGA technology,”
Microelectronics Journal, vol. 38, pp. 120-124, 2007
Y. Cheng, B. Shew, M.K. Chyu, P.H. Chen,
“Ultra-deep LIGA process and its applications,”
Nuclear Instruments and Methods in Physics Resarch, part A 467-468, pp. 1192-1197, 2001
R.K. Kupka, F. Bouamrane, C. Cremers, S. Megtert,
“Microfabrication: LIGA-X and applications,”
Applied Surface Science, vol. 164, pp. 97-110, 2000
http://www.fzk.de/fzk/idcplg?IdcService=FZK&node=0893&lang=en
S.A. Campbell,
The Science and Engineering of Microelectronic Fabrication, 2nd ed., pp.551-553, 2001