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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.