TRANSMISSION
LASER BONDING FOR MEMS PACKAGING
MILLING OF 3D NANOSCALE
MOLDS FOR NANOIMPRINTING AND MICROFORMING USING FOCUSED ION BEAMS
ELECTRON-BEAM
LITHOGRAPHY OF NANOBOWTIE ARRAY FOR OPTICAL INSPECTION OF NANODEFECTS
NONLINEAR DYNAMICS STUDY AND
DEVELOPMENT OF HIGH PERFORMANCE MEMS GYROSCOPES
FABRICATION OF MICRO- AND
NANO-SCALE CHANNELS FOR MICROSYSTEMS
INTEGRATED SOLID FREEFORMING OF
METAL PARTS
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TRANSMISSION LASER BONDING FOR MEMS PACKAGING
The objective of this research is to advance a
wafer-bonding technique, called transmission laser bonding, to be reliable and applicable
for packaging microelectromechanical (MEMS) devices. The approach is to use
both experimental and numerical schemes to study the physical and chemical
phenomena in the bonding region during and after bonding at micro- and
nano-scale levels. Using characteristics of laser and the associated optical
properties, the technique can efficiently bond a transparent wafer, such as
glass, to an opaque substrate, such as silicon, by laser melting of a thin
layer near the interface. The success of the proposed research will lead to
significant cost savings and quality enhancement in microdevice packaging.
Since packaging costs represent more than fifty percent of the total device
cost, the proposed research should be extremely important to the associated industry.
Currently, the applications of these microdevice products have been extended
from the traditional automotive and aerospace sectors to many emerging markets,
including consumer electronics, biomedical, and information systems. These products will have a major impact
either directly or indirectly, on people's daily lives.
The micromechanical testing results disclose
that the TLB bonded strength depends on not only the
contact
pressure applied, but also on the surface roughness and the thickness of the intermediate oxide layer. However, the bonding strength
reaches a stable value of 10.5 MPa with the contact pressure higher than 0.5
MPa, oxide layer thinner than 100-nm, and surface roughness less than 1-nm. The
strength of 10.5 MPa is equivalent to, if not better than those obtained by
other major bonding processes, including anodic and fusion bonding, which are
currently used by MEMS packaging. The
results also reveal that the wafer roughness and flatness required by TLB can
be less stringent than those specified in the current industrial standards, so
that the typical wafers used by industry can be directly adopted for the
present TLB. Indeed, TLB can provide high quality bonds that are as good as the
other major wafer bonding techniques but without the long processing time, high
processing temperature, and externally high electrical potentials, normally
required by the other major techniques, including anodic and fusion
bonding. The TLB technique can also be
performed at room temperature without the need of an intermediate layer and
clean room environment.
Collaborators: Dr.
Sponsors: US National Science Foundation (DMI-0423457), Pacific Technology, and Freescale
Semiconductor
Selected Publication:
1. Park,
J-S. and Tseng, A. A. (2004), “Transmission laser
bonding of glass with silicon wafer,” in Proceedings of 2004 Japan-USA Symposium on Flexible
Automation, Paper No. UL-073, ASME.
2. Park, J-S. and Tseng, A. A (2005), “Development and characterization of transmission laser
bonding technique” in Proceedings of
IMAPS Int. Conf. Exhibition Device Packaging, Paper No. TA15, Int. Microelectronics and Packaging Society.
3. Park, J-S. and Tseng, A. A. (2006), “Line bonding using
transmission laser bonding for microsystem packaging,” in ITherm 2006 Proceedings, IEEE.
4. Park, J-S. (2006), “Characterization of transmission laser bonding technique for microsystem packaging,” presentation.
MILLING OF 3D NANOSCALE MOLDS FOR NANOIMPRINTING AND
MICROFORMING USING FOCUSED ION BEAMS
A focused ion beam (FIB) milling technology will be
developed for the fabrication of three-dimensional (3D) nanoscale molds for the
mass production of micro- and nano-structures using nanoimprinting and
microforming. Nanoimprinting is a major candidate for next generation
lithography (NGL) in the semiconductor industry, as well as being a critical
tool for nano/micro-electromechanical systems (N/MEMS). Microforming is the
emerging technology for the large-scale production of MEMS and other miniature
parts with various applications. The success and proliferation of
nanoimprinting and microforming technologies are highly dependent on the
ability to make the molds and tools required for these technologies.
The main challenges
in making 3D nanomolds are controlling the milling rates at sub-nanometer
scales and making nonlinear curved mold surfaces from the normal milling
abilities, which include simple wedge or rectangular geometries. The proposed
approaches involve both traditional manufacturing automation tasks and the
study of nontraditional fabrication phenomena at atomic levels, especially the
interaction between energetic ion particles and target materials at quantum
scales. The tasks for automation include
modeling development to enhance the ability of existing computer-aided
manufacturing (
Collaborators:
Dr.
Sponsors: Nanotron, Pacific Technology, Walsin Lihwa, and Oldcastle Glass
Selected Publication:
1. Tseng,
A. A., Leeladharan, B., Li, B., Insua, I. A. and Chen, C. D. (2003), “Fabrication and
modeling of microchannel milling using focused ion beam,” Int. J. Nanoscience, Vol.
2, Nos. 4 & 5, pp. 375-379.
2. Tseng, A. A., Insua, I. A., Park, J. S.,
and Chen, C. D. (2005), "Submicron milling of
two-layer substrates using focused ion beam," J. Micromech.
Microeng, Vol. 15, No. 1, pp. 20-28.
3. Tseng, A. A. (2004), “Recent developments in
micromilling using focused ion beam technology,” J. Micromech.
Microeng., Vol. 14, No. 4, pp. R15-R34.
4. Tseng, A. A. (2005), “Recent developments in
nanofabrication using focused ion beams,” Small, Vol. 1, No. 10, pp. 924-939.
ELECTRON-BEAM LITHOGRAPHY OF NANOBOWTIE ARRAY FOR OPTICAL INSPECTION OF NANODEFECTS
Defects in the micrometer or
nanometer scales are the leading cause of failure in components and end
products in widely diverse industries.
The on-line inspection tools needed to identify such defects are also
required to meet or exceed current inspection rates of thirty wafers per
hour. Optical probes are the fastest
inspection tools currently on the market.
However, as the defects or objects approach the order of the wavelength
of the optical probe, it becomes difficult to image them. After reaching the
diffraction limit, the signal to noise ratio eventually becomes prohibitively
low to support fast, reliable on-line inspection. In the standard optical scattering approach,
the smallest objects that can be reliably examined are on the order of 200
nm. Therefore, a new method that can
quickly and reliably detect defects significantly smaller than the diffraction
limit is needed.
Near-field optics, which enable
optical imaging with spatial resolution that is significantly better than the
diffraction limit, has recently found application in microwave ranges. In this
light, the goal of the present research is to examine the extension of the
near-field concept from the microwave to the optical wave ranges. A bowtie array proposed by the investigators
that implements the newly-invented concept of the Wave Interrogated Near-Field
Array (WINFA) is designed and fabricated so that the new optical probe can
overcome the diffraction limit by combining the sensitivity of near-field
detection with the speed of optical scanning.
In
the present research, a scaled-down nanobowtie array will be built to
demonstrate that the WINFA concept can be extended to a much shorter wavelength
for nanoscale inspection. The
fabrication process featuring electron-beam lithography of nanoscale
structures, especially the considerations specific to fabricating a nanobowtie
array, will be studied. Different substrate materials and different
lithographic conditions will be considered for pattern variation evaluations. A
prototype WINFA system including the nanobowtie array, scanning stage,
holographic filters, and pattern recognition software will be assembled and
tested to optimize the system's efficiency.
Collaborators: Dr. Chii D. Chen, Dr. Rudy
E. Diaz, Dr. T. P. Chen, Dr. A. Notargiacomo, and Mr.
Sponsors: US National Science
Foundation, and ASU Consortium for Metrology
of Semiconductor Nanodefects
Selected
Publication:
1. Tseng,
A. A., Chen, C. D., Wu, C. S., Diaz, R. E., and Watts, M. E. (2002), “Electron-beam
lithography of microbowtie structures for next generation optical probe,” J. Microlithography, Microfabrication, and
Microsystems, Vol. 1, No. 2, pp. 123-135 (cover
article).
2. Tseng, A. A., Chen, K., Chen, C. D., and
Ma, K. J. (2003), “Electron beam lithography in nanoscale fabrication: recent
development," IEEE Trans. Electronics Packaging Manufacturing, Vol.
26, No. 2, pp. 141-149.
3. Tseng, A. A., Notargiacomo, A., and Chen, T. P.
(2005), “Nanofabrication by scanning probe microscope lithography: a review,” J.
Vac. Sci. Technol. B, Vol. 23, No. 3, pp. 877-894
4. Liu, Y., Chen, T.
P., Ng, C. Y., Ding, L., Tse,
M. S., Fung, S. and Tseng, A. A. (2006), “Influence of Si-nanocrystal distribution in the
oxide on the charging behavior of metal-oxide-semiconductor structures,” IEEE
Trans. Electron Devices, Vol. 53, No. 4, pp. 914-917.
NONLINEAR DYNAMICS STUDY AND DEVELOPMENT
OF HIGH PERFORMANCE MEMS GYROSCOPES
Even though microelectromechanical gyroscopes, also known as MEMS gyros or
microgyros, are about to be commercialized, the low technical performance of
these microgyros limits their use in less demanding automotive applications. As
such, high performance MEMS gyroscopes are in demand; a specific example of
this is the navigation of vehicles and micro-spacecraft. It is believed that understanding the
nonlinear dynamics of MEMS gyroscopes is essential to achieving improved gyro
performance. The major task required to achieve this objective is to understand
the instability reported by other investigators. The onset of instability in
MEMS gyroscopes prevents the microgyros from operating at optimum
conditions. Specifically, the mismatch
between the resonance frequencies in the microgyro structure has not been
minimized by existing designs. Since the microgyros have very low damping,
operating at imperfect resonance greatly limits the performance of the gyro. To
overcome this limitation, nonlinearity in the system must be considered since
the system dynamics near resonance are well known to be greatly affected by
nonlinear effects, even though these nonlinear effects are otherwise small.
The goal of the present effort is to develop better
fabrication techniques for the thick structures of the microgyros. This is
motivated by the simple fact that microgyros are inertia sensors and thicker
structures will accentuate the Coriolis force, making the signal detection more
immune to the noise associated with signal amplification. Despite the tremendous amount of research and
development on MEMS inertia sensors, the crucial research results are not
available in the literature. Much of the know-how on microgyro designs remains
proprietary. Through the proposed research, it is our hope to provide the
research community with findings on the design considerations and innovative
fabrication techniques for microgyros.
Collaborators: Dr. Zaichun Feng, Dr. Gary
X. Li, Mr.
Sponsors: National Science Foundation,
Selected
Publication:
1. Tseng, A. A.,
Tang, W.C., Lee, Y.-C., and Allen, J. (2000), “NSF 2000 workshop on manufacturing of micro-electro-mechanical
systems,” J. Mat. Processing
& Manufacturing Science, Vol. 8, No. 4, pp. 292-305.
2. Li, G. X. and Tseng, A. A. (2000), “ Transient
and impact dynamics of a micro-accelerometer,” J. Mat. Processing & Manufacturing
Science, Vol. 9, No. 2, pp. 143-155.
3. Li, G. X. and Tseng A. A., “Low Stress Packaging of A
Micro-Machined Accelerometer,”IEEE Trans. Electronics Packaging
Manufacturing, Vol. 24, No. 1, pp. 16-25, 2001.
4. Tseng, A. A., Chen, Y. T., and Ma, K. J.
(2004), “ Fabrication of high-aspect-ratio microstructures using excimer
lasers,” Optics & Lasers Eng., Vol. 41, No. 6, pp. 827-847,
FABRICATION OF MICRO- AND NANO-SCALE CHANNELS
FOR MICROSYSTEMS
It is understood
that the majority of processes for MEMS fabrication, driven by the
semiconductor industry, are mask-based, parallel in nature, and
CMOS-compatible. As an alternative, the
present research focuses on the development of direct-write technologies for
MEMS fabrication. In principle, the direct-write technologies, including laser
micromachining, are serial in nature and feature shorter lead-time, lower
material removal rates, and lower speeds when compared to parallel
processes. However, the emergence of
MEMS has provided an impetus to direct-write laser-micromachining, turning some
of the intrinsic disadvantages of the process when applied on the macroscale
into advantages when it comes to the meso- and micro-scale. As a result, the
purpose of the present research is to establish an agile direct-write
laser-based fabrication system for MEMS and the processing of magnetically hard
and soft materials.
Our laser-based
research has identified two processes for engineering magnetic MEMS by
laser-micromachining. The first technique is a derivative of the laser
thermo-magnetic recording process in which the magnetic material is thermally-
and magnetically-processed, but is not structurally changed or ablated. The
second process includes mesoscopic material removal (ablation). Although most
of the energy of the laser light beam is contributed by the electric field,
with the magnetic field component being negligible (at least six orders of
magnitude smaller), laser micromachining of magnetic materials remains a
coupled electromagnetic and thermo-hydrodynamical problem when in comes to
analyzing the melt pool in the case of ablating material through fusion.
Several CAD geometries have been successfully constructed on 10 µm thick films
and 100 µm thick sheets of a representative magnetic material, such as
permalloy (Ni80Fe20), an integral part of magneto-thermo-fluidic
(MTF) MEMS. Optical and atomic
microscopes and statistical analysis have been used to quantify the dimensional
accuracy of these patterned CAD geometries. A typical MTF MEMS device with
applications in microscale fluid mixing and separating has been designed and
analyzed and a fabrication schedule for realizing the device has been reported.
Collaborators: Dr. George Vakanas, Dr. J. Gu, Dr. F. Zenhausern and
Mr.
Sponsors: Intel Corp.,
Walsin Lihwa, ROC National Science Council, ASU Seed Funding
Selected Publication:
1. Vakanas,
G. P, Tseng, A.A., and Winer, P. (2002), “Laser-assisted chemical etching for embedded
microchannels and overhanging microstructures on Si/SiO2
substrates,” J. Laser Applications, Vol. 14, No. 3, pp. 185-190.
2. Tseng, A. A., Insua, I. A., Park, J. S.,
Li, B., and Vakanas, G. P. (2004), "Milling of submicron channels on gold
layer using double charged arsenic ion beam," J. Vac. Sci. Technol. B,
Vol. 22, No.1, pp. 82-89.
3. Chen, Y. T., Ma, K. J., Tseng, A. A., and
Chen, P. H. (2005), "Projection ablation of glass-based single and arrayed
microstructures using excimer laser," Optics & Laser Tech., Vol. 37, No. 4, pp. 271-280..
4. Gupta, R. K., (2005), “Fabrication of integrated nanofluidic
systems,” MS Thesis, Mechanical Engineering, ASU (Advisor: A. A. Tseng).
INTEGRATED SOLID FREEFORMING OF METAL PARTS
Technological advancements in rapid freeforming have
dramatically reduced the lead-time in parts manufacturing, resulting in an
increase in overall process efficiency.
However, due to the nature of layer manufacturing, dimensional accuracy
and surface texture are still a major limitation of freeform product
fabrication. Post-product finishing is estimated as adding significantly to the
cost of the production of freeformed parts. This problem will persist despite
the continuous evolution of freeforming technology; thus, a new conception of
rapid freeforming techniques incorporating the need for increased dimensional
accuracy and improved surface texture is presented.
The aim of this research is to develop an innovative
solid freeforming technique that allows freeforming parts to be interactively
fabricated by the layer deposition process and material removal process.
Depending on the part geometry, several layers of the material will be
deposited initially, and then the surface contour of the incomplete part will
be processed to achieve the desired dimension and surface finish. Then,
additional layers of the material will be deposited onto the still-incomplete
part to build another segment of the envisioned product. These interactive
processes will be reiterated until the part has been completed as designed. A post
processor based on the concept of parallel kinematic structures with the
capability of 5-axis motion will be built and integrated with an existing
freeforming machine to form an integrated rapid fabrication cell. The post
processor will be equipped with multiple tools to remove the excess material,
which will effectively depend on feature size, dimension tolerance, and surface
texture. The present research is
motivated by the need to develop innovative and robust methods to advance the
technology of freeform fabrication and parallel kinematic machines for agile
and precision manufacturing. As such, if successful, this research will
significantly impact the rapid precision manufacturing of freeform parts, which
is an extremely important global niche for American industry.
Collaborators: Dr. J. H. Chun, Dr. Jong
I. Mou, Dr. Munhee Lee, Dr. B. S. Zhao, Dr. J. G. Zhou, and Mr. Masahito Tanaka
Sponsors: US Department of Energy,
Selected
Publication:
1. Tseng, A.A., Lee, M. H., and Zhao, B. (2001), “Design
and operation of a droplet deposition system for freeform fabrication of metal
parts,” ASME J.
2. Tseng, A. A., and Tanaka, M. (2001), “Advanced deposition
techniques for freeforming metal and ceramic parts,” Rapid Prototyping J.,
Vol. 7, No. 1, pp. 6-17 (Received 2002 High Commended Award).
3. Zhou, J. G., Kokkengada, M., He, Z., Kim, Y. S., and Tseng, A.
A. (2004), "Low temperature polymer infiltration for rapid tooling,"Materials
and Design, Vol. 25, No. 2, pp. 145-154.
4. Tseng, A. A. (2000), “Adaptable filament deposition system and
method for freeform fabrication of three-dimensional objects,” US Patent No.
6,030,199; US Patent No. 6,113,696; US Patent No. 6,149,072; US Patent No.
6,216,765; US Patent No. 6,251,340B1; US Patent No. 6,309,711; and US Patent
No. 6, 372,178 B1; US Patent No. 6,851,587).