Integrated Magnetic Sensors and Actuators

1
Integrated Magnetic Sensors and Actuators
Mark Tondra, Tony Popple, Albrecht Jander, Bob
Schneider, NVE Corp., Eden Prairie, MN John Fox,
Lightools Nikola Pekas, Rachel Millen, Marc
Porter, Iowa State Univ. KickOff July 10, 2003
San Diego, CA

• About NVE
• BioMagnetICs Tool Factory
• Present Experiments
• Planned Improvements and Developments
• Conclusions

2
NVE Corporation

• Founded in 1989 as Nonvolatile Electronics
• Now traded on NASDAQ as NVEC
• About 60 employees
• 6000 ft2 clean room (class 100)
• Specialize in integrated magnetoresistive devices
• FY 03 revenues 9M
• Magnetic Sensors biomedical, industrial
• Digital signal couplers
• Contract and Govt. Research and Development

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NVE Highlights

• Licensed by Honeywell in 1989 to produce
  Magnetoresistive Random Access Memory (MRAM)
• Introduced worlds first GMR product in 1996
• Signal isolator product introduced in 1999
• Research Development Thrusts
• Biosensors
• MRAM
• Low-Field Magnetometers
• Non-destructive Evaluation
• Electronics and systems

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NVE Fabrication Facility
PE 2400
Comptech
5

• About NVE
• BioMagnetICs Tool Factory
• Present Experiments
• Planned Improvements and Developments
• Conclusions

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Magnetoresistive Material Structures
AF Pinning Layer
SpinValve
Magnetic (Co,Fe, Ni alloys)
Non-magnetic (Cu alloys, Al2O3)
Multilayer
10 nm
2 mm
20 mm
Sandwich
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Idealized Spin Valve Transfer Curve
Resistance ? R0 sinq
Voltage / Resistance
-2 -1 0 1 2
Field (Oe)
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Low Hysteresis Spin Valve
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Magnefluidics Process Cross Section
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PDMS flow channel mold from SU-8
Up to 860 mm thick Ultra-high aspect ratio Wafer
level processing Rapid prototyping Adding
Multi-level, pick place
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Reticle Layout 100180

• Design Basics
• 12 mm x 12 mm total
• 16 dice
• 1.5 mm x 6 mm each
• 24 pads on each die
• Common pad pattern
• Devices
• Sense Pad
• 20 sensor array
• Flow Detector
• Cell Detector
• Sorter
• Pump
• Process test devices

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Reticle Layout 100172

• Design Basics
• 12 mm x 12 mm total
• 16 dice
• 1.5 mm x 6 mm each
• 24 pads on each die
• Common pad pattern
• Devices
• Sense Pads, several orientations
• Flow Detector
• Sorter
• Pump
• Process test devices

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Stray Fields in-plane excitation
Need a sensor with bipolar output The detected
in-plane stray fields are in one
r
GMR
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Wheatstone Bridge Design
I
Reference resistors for field and temperature
compensation 2 Sense resistors that experience
the sample or field being measured Reference
resistors do not experience sample Vout Out -
Out-. If there is nothing to make the sense
resistors behave differently than the refs, Vout
0 Volts
Rsense1
RRef2
Out-
Out
Rsense2
RRef1
GND
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Layout Define Sensing Region
100 mm x 100 mm sense region
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Layout Place Sense Resistors
Place Rsense1
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Layout Place Sense Resistors
Rsense1
Add identical Rsense2
I
Rsense2
The two sense resistors are interwoven to allow
them to sense the same region and experience the
same excitation field.
Rsense1
RRef2
Out-
Out
RRef1
Rsense2
GND
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Layout Place Reference Resistors
Add two identical Rref
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Layout Add Al Interconnect
Out-
I
GND
Out
Add interconnection metal (Aluminum)
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Layout Add sense region
Out-
I
GND
Out
Define sensing region by selective etching and
surface chemistry
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Die-Holding Printed Circuit Board
Diving Board
Design Basics 24 pin surface mount edge
connector Narrow die area for fitting between in
the excitation magnet gap
Wire bonds are potted such that sense pad is
still exposed
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BioMagnetICs Device Workflow
Work Step Calendar months Conceptual
Design 0.5 Device Design and Layout 0.5 Wafer-l
evel fabrication 2-3 Dicing, wire bonding,
potting, 1 Testing 0.5 Total
5 mo.
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Proposed BioMagnetICs System Design
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Magnetic Excitation Module
New version (6-layer coil) will generate 1Oe /
mA
Ferromagnetic core
Sensor
Coil
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BioMagnetICs Handheld Reader

• Pocketsized
• Connects to Laptop AD card
• Accepts 24 pin diving board
• On-Board field 100 Oe _at_ 250 mA
• Still a lot of room for miniaturization

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BioMagnetIC System

• A to D card in laptop
• Pocket-sized excitation module
• Disposable sensor cartridges
• Adaptable device development platform
• R vs. H plots
• Vout vs. time

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Nanowire detection Ferrofluid Plug
Detection Surface chemistry on chip Ferrofluid
label detection Process Development Single Cell
DNA

• About NVE
• BioMagnetICs Tool Factory
• Present Experiments
• Planned Improvements and Developments
• Conclusions

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Output of SV sensor vs. bead concentration
Courtesy R. Millen, M. Porter, Iowa State Univ.
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BioMagnetICs Detection Design
Courtesy R. Millen, M. Porter, Iowa State Univ.
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Present Experiments Surface Chem on Chip
Rachel Millen, Toshi Kawaguchi,Marc Porter Dept.
of Chemistry Iowa State Univ. SEE POSTER

• With S/N 3, the detection limit is 0.1 MP/µm2
• Using 60 nm MP, 0.1 MP/µm2 corresponds to a
  detectable MP surface coverage of 0.1

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Present Experiments Ferrofluid Plug
Nikola Pekas, ISU Detecting ferrofluid plugs
flowing over GMR sensors SEE POSTER
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GMR sensor data,10-point moving average
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Present Experiments NRL
Shawn Mulvaney et. al. Doing surface chemistry
under TSWG Cy Tamanaha is making a Cell DNA
detector under an NIH grant
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Present Experiments Ferrofluid DNA Label
John Fox, Lightools SEE Poster
Sensor Voltage (Volts)
AD counts (0.1 secs. each)
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Present Experiments Nanowire Detection
Dan Reich, Sasha Anguelouch, et.al. Johns
Hopkins Univ. Making 150 nm diameter
ferromagnetic nanowires Detection with 100 micron
Sense Pad
2 Talks from now
Courtesy Sasha Anguelouch, Johns Hopkins U.
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Present Experiments Ultra-Thin Dielectric
Shan Wang, G. Li, J. Kemp Dept. of Mat. Science
and Eng. Electrical Eng. Stanford Univ. NEXT
TALK

• Trying to detect very small single Co particles
• Has special scheme for ultra-thin GMR passivation
• Trying to functionalize Co particles

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Surface Chemistry Ready Detection of flowing
Cells Magnetic Tunnel Junctions Wafer-Scale
Fluidic Chip Beginnings of IC Array

• About NVE
• BioMagnetICs Tool Factory
• Present Experiments
• Planned Improvements and Developments
• Conclusions

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Full Lithographic Microfluidic Fab Process

• Current microfluidic manufacturing has too much
  manual work
• Cost / size relationship demands smaller devices
• Need integrated circuitry for high sensor count

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• About NVE
• BioMagnetICs Tool Factory
• Present Experiments
• Planned Improvements and Developments
• Conclusions

40
Conclusions

• Multi-User BioMagnetICs Fabrication Process is
  Ready
• Magnetic Excitation Board and Software is
  Available
• Detection of single nano-wires, ferrofluids, and
  plugs has been demonstrated
• Flow experiments are beginning
• Related research projects pushing towards
  productization
• Room for further collaborations
• www.nve.com/markt/biomagnetics