polymer could improve semiconductor manufacturing, packaging.
Researchers from Rensselaer Polytechnic Institute’s
Department of Physics and Center for Integrated Electronics have developed an
inexpensive, quick-drying polymer that could lead to dramatic cost savings and
efficiency gains in semiconductor manufacturing and computer-chip packaging. In
this scanning electron microscope image of the new PES polymer in a
photolithography application, the straight side walls indicate the material’s
good photodefinition characteristics.
A scanning electron microscope image showing the imprints of
trenches and dual-damascene structures realized using PES in the newly
developed molecular-transfer lithography process, indicating the potential of
PES for microchip applications.
Researchers at Rensselaer Polytechnic Institute, Troy, NY, and Polyset
Co., Mechanicville, NY, have developed an inexpensive,
quick-drying polymer that could lead to dramatic cost savings and efficiency
gains in semiconductor manufacturing and computer chip packaging.
Along with allowing enhanced performance and cost savings for conventional
photolithography processes, the new material, called polyset epoxy siloxane
(PES), should also enable a new generation of lower-cost, on-chip
nanoimprinting lithography technology, according to the researchers.
“With this new material, chip manufacturers will be able to trim several steps
from their production and packaging processes, and in turn realize a cost
savings,” said Toh-Ming Lu, the R.P. Baker Distinguished Professor of Physics
at Rensselaer, who oversaw the study. “PES is cheaper and more reliable.”
Lu’s research was published in the Journal of Vacuum Science and
The widely adopted technique of photolithography involves using a mix of light
and chemicals to generate intricate micro- and nano-scale patterns on tiny
areas of silicon. As part of the process, a thin polymer film called a
redistribution layer, which is crucial to the effectiveness of the device, is
deposited onto the silicon wafer in order to ease the signal propagation delay
and to protect the chip from different environmental and mechanical factors.
The new PES material developed by Lu’s group and Polyset Co. is one such thin
polymer film, and it offers several advantages over the incumbent materials
typically used in semiconductor manufacturing. In addition, the new PES
material can also be used as a thin polymer film for ultraviolet on-chip
nanoimprinting lithography technology, which is still in the early phases of
development. The consistency of using PES in conventional technology, and then
continuing to use PES while academia and industry test and gradually migrate to
the next generation of devices, should help ease the transition, Lu said.
“Having the ability to use one material - our new PES - for both
photolithography and imprint will be very attractive to manufacturers,” Lu
said. “At its core, our project is basic research, but it also has important
industry implications. It’s very exciting.”
Manufacturers today typically use benzocyclobutene and polyimide as polymers
for redistribution layers, because of their low water absorption, thermal
stability, low curing temperature, low thermal expansion, low dielectric
constant, and low leakage current. Lu said PES offers significant advantages to
these materials, particularly in the areas of cure temperature and water
A series of scanning electron microscope images of the new
PES polymer in a UV-imprint lithography application. The well-defined pattern indicates
the material’s potential for use in next-generation chipmaking techniques.
Along with allowing enhanced performance and cost savings for conventional
photolithography processes, PES should also enable a new generation of
lower-cost, on-chip nanoimprinting lithography technology.
PES cures - or dries and hardens - at 165°C, about 35%
cooler than the other two materials. The need for less heat should translate
directly into lower overhead costs for manufacturers, Lu said. Another
advantage of PES is its low water uptake rate of less than 0.2%, less than the
other materials. In addition, PES adheres well to copper and can easily be made
less brittle, if needed. All of these attributes make PES a promising candidate
for redistribution layer application and UV imprint lithography.
“The results demonstrate that PES is feasible to be used as UV-curable resist
for both the redistribution application for electronic packaging and micro/nano
imprint lithography,” said Rensselaer Research Associate Pei-I Wang, co-author
of the paper.
Along with photolithography and on-chip nanoimprinting lithography, PES holds
the potential for applications in other optical devices, flat-panel display,
biotechnology devices, and microelectromechanical systems, Wang said.
In addition to Lu and Wang, co-authors on the paper include Rensselaer
materials science and engineering professor Omkaram Nalamasu, who is also chief
technical officer of Applied Materials Inc. in Santa Clara, CA; Rajat Ghoshal
and Ram Ghoshal of Polyset Co. Inc. in Mechanicville, NY; Charles Schaper of
Transfer Devices Inc. in Santa Clara, CA; and Andrew Li of Applied Materials.
The project was funded through the New York State Foundation for Science,
Technology and Innovation.
Lu’s research was conducted as part of Rensselaer’s
Center for Integrated Electronics. The center’s multidisciplinary team of more
than 50 faculty researchers and 100 graduate students aims to advance the role
of electronic devices in our everyday lives by accelerating the production of
the next generation of micro- and nanoelectronic devices and systems. The
Center’s mission is to build integrated top-down and bottom-up nanostructures,
devices, and systems for information, biological, and broadband communication
applications. Major activities include pioneering research into gigascale
interconnects, 3-D interconnect structures, materials properties and process
modeling, wideband gap semiconductors and devices, terahertz devices and
imaging systems, power electronic devices and systems, and biochips.
Polytechnic Institute, founded in 1824, is the nation’s oldest technological university.
The university offers bachelor’s, master’s and doctoral degrees in engineering,
the sciences, information technology, architecture, management, and humanities
and social sciences. Institute programs serve undergraduates, graduate students
and working professionals around the world. Rensselaer faculty are known for
pre-eminence in research conducted in a range of fields, with particular
emphasis in biotechnology, nanotechnology, information technology, and the
media arts and technology. The Institute is well known for its success in the
transfer of technology from the laboratory to the marketplace so that new
discoveries and inventions benefit human life, protect the environment and
strengthen economic development.
Co. is a technology-driven materials company with a philosophy of designing
resin systems around needs. It is a market leader within product areas of
focus, and has been a leader in urethane adhesive systems and
corrosion-resistant primers for many years. Much of its new product development
is based on new proprietary advanced materials, catalysts and associated
formulations that deliver functionality. In these endeavors, it focuses on
wafer-level manufacturing and interconnect assembly, incorporating both
electronic and optical packaging material. In addition, the company has
developed novel 100%-solid coating formulations for the coil-coating industry
that allows for the elimination of solvent-based coating. Polyset provides
contract manufacturing services for resins, prepolymers, adhesives and related
components for diverse companies, including Fortune 50 corporations.
For more information on Lu’s research and Rensselaer’s
Center for Integrated Electronics, visit www.rpi.edu/~lut/ and www.rpi.edu/dept/cie .
For more information on the new PES materials, visit www.polyset.com.