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Portland State University Portland State University
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Student Research Symposium Student Research Symposium 2015
May 12th, 11:00 AM - 1:00 PM
Design, Construction, and Utilization of Physical Design, Construction, and Utilization of Physical
Vapor Deposition Systems for Medical Sensor Vapor Deposition Systems for Medical Sensor
Fabrication Fabrication
Nicholas Sayre Portland State University
Erik J. Sánchez Portland State University
Joe Kowalski Portland State University
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Sayre, Nicholas; Sánchez, Erik J.; and Kowalski, Joe, "Design, Construction, and Utilization of Physical Vapor Deposition Systems for Medical Sensor Fabrication" (2015). Student Research Symposium. 11. https://pdxscholar.library.pdx.edu/studentsymposium/2015/Posters/11
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Photoresist
Metal foil on
polyimide
Glass slide
Sensor Fabrication
Nicholas Sayre nsayre@pdx.edu
A novel blood glucose sensor is realized by using semiconductor
manufacturing processes in the PNNA cleanroom on Portland State
University campus. The substrate consists of a titanium foil laminated
onto a flexible polyimide film which is then adhered to a glass slide to
aid in processing. A photolithographic process is used to define regions
on the substrate surface so that structures may be formed through
successive coating and etching processes. Photolithography begins with
covering the substrate surface in a light sensitive material called
photoresist.
Photoresist is a mixture of compounds which is formulated to change
its solubility when exposed to ultraviolet light. This allows exposed
regions to be dissolved simply by rinsing in a developing solution. By
exposing the photoresist to ultraviolet light in a pattern defined by a
light blocking stencil called a mask, pattern defining features may be
formed in the photoresist.
Once the photoresist has been developed, the pattern that is left allows
selective addition or subtraction with deposition or etching processes.
Successive deposition or etch steps, interleaved with a pattern defining
photolithography process, allow the formation of complex 3-
dimensional patterns on the surface of the substrate.
Starting substrate spin coated with photoresist
Completed blood glucose sensor
Du et al,. 2015
Vacuum System
Gas Manifold
Control System
Plasma Sputtering
Plasma sputtering system in operation
Sputtering is a versatile coating method that is commonly used in
modern electronic device fabrication. Sputtering is realized through the
ionization of a gas via strong electric or magnetic fields. Positively
ionized gas atoms are attracted towards a negatively biased “target”
which is a disc of the desired coating material. Gas ions bombard the
target and dislodge atoms which then make their way to the substrate.
The diagram below illustrates the basic construction of a sputtering
head. For this system we learned from the design of the desktop
sputtering system shown above to generate our own sputtering head.
The control system for this system is based on a simple switch
activated control panel interface. Connectors have been built into the
back of the control panel so that the whole panel may be easily
removed in order to perform system maintenance. LEDs show switch
status on a front panel which displays the vacuum system and gas
manifold diagrams. Switch position translates to valve actuation via
two sets of solenoid banks wired into the control panel. Emergency
off protection and vacuum safety interlocks have been included in the
control system to prevent equipment damage and ensure safety.
Having more than one sputtering head in a system provides a few
unique advantages. Multiple sputtering heads allow creating films with
complex compositions as well as forming multilayer films without
breaking vacuum. Larger coating area and improved uniformity are also
possible.
The gas manifold on this system is
unique because it allows closely
controlled mass flow (0-200 sccm) of two
different gas species. Both Oxygen and
Argon gases may be applied in user
controlled quantities to each head on an
individual basis. This allows optimization
of sputtering parameters by adjusting gas
flow and type based on sputter head
target material. The manifold is
connected to the vacuum system to allow
evacuation of residual gas to reduce
contamination.
System Photo
Future Work Once the system is finished it will increase sensor manufacturing
productivity and provide a valuable resource to the PNNA cleanroom,
giving PSU students and professors access to a simple and high quality
coating system to help promote industry collaboration and research.
Abstract Deposition systems are essential components in thin film
manufacturing processes, however these systems are typically
expensive and thus difficult to acquire. The development of a novel
blood glucose sensor is realized through construction of a homemade
plasma coating system and utilization of semiconductor manufacturing
processes in a small scale cleanroom environment. Photolithography,
plasma sputtering, chemical etching and thin film measurement
technologies are used in the medical sensor fabrication process. We
have established a fabrication process and achieved successful
patterning of successive layers as we finish construction of the coating
system. General process flow will be discussed, and system design and
the plasma sputtering process will be presented as it is achieved by the
system currently under development.
Constructing a Triple Head Sputtering Deposition System for Novel Blood Glucose Sensor Fabrication Nicholas Sayre1, Abdul Almetairi2, Alex Chally3, Joe Kowalski4, Erik Sánchez1,2
1Department of Electrical and Computer Engineering, 2 Department of Physics, 3Science Support Shop, Portland State University. PO box 751, Portland, OR 97207, USA. 4Pacific Diabetes Technologies 2828 SW
Corbett Ave. Ste 211-A Portland, OR 97201, USA.
Photoresist being exposed to UV light through a mask (left) and the
pattern resulting from subsequent developing and etching steps (right).
Front of control panel
Back of control panel
Image of the sputtering system under development
Vacuum system diagram
Gas manifold
Sputter head construction and operation
Power supply and control rack
The diagram above shows the basic outline of the vacuum
subsystem. Vacuum chambers are necessary for the sputtering
process for multiple reasons. The sputtering process requires
subatmospheric pressure (1-100 mTorr) in order to initiate a plasma,
and to reduce molecular collisions to the point that coating material
can travel from the sputtering head to the substrate. Furthermore,
yet lower pressure values into the high vacuum regime give the
benefit of eliminating adsorbed water and residual atmospheric
gases, which help provide good adhesion and consistent, quality
coatings.
References: Du et al,
“Fabrication of a Flexible
Amperometric Glucose
Sensor Using Additive
Processes” ECS Journal
of Solid State Science and
Technology, 4 (4) P3069-
P3074 (2015)
Acknowledgments Surplus Gizmos for the generous donation of gas manifold components,
Alex Chally for sputter head machining, Abdul Almetairi for gas
manifold construction, Joe Kowalski for sensor fabrication, Leroy Laush
for his electronics repair expertise, and the members of the Sanchez lab.