Download Microshutters for particle velocity measurements: Modelling and

Microshutters for particle velocity measurements:
Modelling and fabrication
Klas Brinkfeldt
Swedish Institute of Space Physics, Kiruna
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Microshutters for particle velocity measurements: Modelling and fabrication
Solar System Physics and Space Technology group at IRF:
• Conducts comparative research on the evolution and
dynamics of the solar system objects and their interaction
with the solar wind.
• Manufacture ion mass spectrometers, electron
spectrometers, energetic particle detectors, and energetic
neutral atom (ENA) imagers to study Mercury, Venus, Earth,
Mars, and comets.
The Swedish Institute of Space Physics (IRF)
Solid State Electronics group at MC2:
• Specializes on silicon and silicon
related materials and devices including:
- MOS (Metal-Oxide-Semiconductor) physics and
devices.
- Wafer bonding and SOI technology.
- Substrate Noise Coupling in Mixed-Signal System-onChip.
- Transistors.
Department of Microtechnology and Nanosciences, Chalmers University of Technology
- Micro- and Nanosystems.
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Microshutters for particle velocity measurements: Modelling and fabrication
Mass spectrometers for space particle measurements:
Time of flight (TOF) systems
Magnetic mass identification systems
• Particle pass through foil or graze surface.
• Particle energy is determined in an electrostatic analyzer (ESA).
• Electrons emitted in the interaction are collected to
produce a START signal.The original particle continues
across a defined distance to a second detector
generating a STOP signal.
• Particle mass can then be determined by measuring the particle
deflection in a known magnetic field.
• The time between START and STOP is measured and
the velocity can be calculated.
• Heavy permanent magnets.
• Particles lose part of its energy in the
foil/surface interaction.
• Generally requires large volume.
• Lower signal to noise ratios.
• Particles lose direction in the foil/surface
interaction.
• Cannot measure low energy neutrals.
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Microshutters for particle velocity measurements: Modelling and fabrication
Shutter based velocity measurements
• Mechanical velocity determination (rotating disc system) was attempted
on sounding rocket experiments in the 1970s [Moore Jr. et al. 1975].
• Large mass, high power consumption and high torque it would exert on
spacecraft made them impossible to use on satellites.
• With
micromechanics the idea can now work.
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Microshutters for particle velocity measurements: Modelling and fabrication
Shutter design
Main objectives:
1.
Develop and manufacture a MEMS shutter for applications in
space particle instruments and
2.
verify its performance in the miniature ion spectrometer
PRIMA.
The design requirements are a result of:
• Expected ion flux based on previous measurements.
• PRIMA parameters.
• Target resolution of the measurements.
Parameter
Value
Open time, Dt
Closed time, t
Driving frequency, f
Transparency, W
25 ns
1700 ns
300 kHz
> 10 -5
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Microshutters for particle velocity measurements: Modelling and fabrication
Shutter design
A dynamic model of an opening in
a oscillating layer moving over a
static layer is used to find the
required oscillation amplitude.
A stress and strain model is
used to find the force required
to actuate the plate structures.
Open
y
t
Static layer
vmax
f
Oscillating layer
d
v   y  sin 2ft 
dt
2s
Dt 
vmax
t
1
 Dt
2f
F
t
Model
Optimization
Design
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
 Fl 3
y
hb 3
384 E
12
AV 2
F  0
2d 2
Microshutters for particle velocity measurements: Modelling and fabrication
Shutter design
105 mm
10 mm
90 mm
60 mm
105 mm
5 mm
85 mm
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
20 mm
Microshutters for particle velocity measurements: Modelling and fabrication
Simulations
Simulations using COMSOL (v3.2) to find:
1.
Eigenfrequency of the desired oscillation mode including:
•
Effects of the opening slits in the plates.
•
Effects of the comb actuation fingers.
2.
Driving voltage to generate the displacement required.
3.
Stress generated in the beams.
4.
Required frame dimensions to minimize coupling between
different shutter elements.
f = 306 kHz
f = 306 kHz
f = 279 kHz
f = 285 kHz
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Microshutters for particle velocity measurements: Modelling and fabrication
Fabrication
From pattern to 3D-structure
3.) Remove exposed photoresist
1.) Wafer preparation
Photoresist
SiO2
Si substrate
2.) Photolithography
4.) Oxide etch
UV
5.) Silicon etch
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Microshutters for particle velocity measurements: Modelling and fabrication
Fabrication
• First batch of prototype microshutters currently
under fabrication.
• Wafer is divided in 55 chips (10 mm × 10 mm).
• Each chip contains an array of hundreds of
microshutters.
• The process requires 9 masking steps.
• Bonding of two SOI (Silicon on Insulator) wafers
together at the device layers.
A
Static Handle (SH)
Silicon
Oxide
Static Device (SD)
Dynamic Device (DD)
Al
Resist
Dynamic Handle (DH)
Bondpads
B
1 micron slits
Electrostatic drivers
Moving plates
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Via connection
Microshutters for particle velocity measurements: Modelling and fabrication
Summary
• Shutter based mass spectrometry.
• Possibility to measure low energy neutral particles (for example, particles sputtered from
the surfaces of Mercury or the Moon).
• Immunity to contamination from UV photons.
• More compact systems (less volume and mass).
• Improved resolution (no particle interaction to generate a START signal).
• MEMS technology shutters are under development.
• An optimized prototype design from theory.
• Simulations have been used to verify the model.
• Fabrication is in progress.
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Swedish National Graduate School of Space Technology Workshop, ESTEC, Sept 13-15 2006
Microshutters for particle velocity measurements: Modelling and fabrication
Advantages of shutter based velocity measurements
• Dramatically improved resolution (no particle interaction to
generate a START signal).
• Possibility to measure low energy neutral particles (for example,
particles sputtered from the surfaces of Mercury or the Moon).
• Immunity to contamination from UV photons.
• More compact systems (less volume and mass).
”Flipping pixel” system by Flixel
TMOS optical from University of Washington
James Webb Space Telescope by the
NASA Goddard Space Flight Center.
Microshutters for particle velocity measurements: Modelling and fabrication
The LEIA (Low Energy Ion Analyzer) project
Main objectives:
1. Develop and manufacture the first ever MEMS
shutter for applications in space particle
instruments and
2. verify its performance in the LEIA instrument to fly
onboard the Swedish technological satellite
PRISMA and/or other flight opportunities.
Microshutters for particle velocity measurements: Modelling and fabrication
Flight opportunities
• PRISMA Satellite
- Technology mission to verify autonomous formation flying (Guidance,
Navigation, and Control, GNC) for future European space missions.
- Consists of two spacecraft, MAIN and TARGET, that will demonstrate
rendezvous and coarse formation flight. Swedish Space Corporation
(SSC) main contractor along with German and French space agencies.
- Launch with Russian ”Dnepr” rocket into a polar Earth orbit in the
second half of 2008.
• Sounding rocket from ESRANGE
- ESRANGE launches several rockets year of different sizes. To place
LEIA on board we need formal approval of the main experiment on
board (buyer of the launch).
- Sounding rockets do not enter Earth orbit. Flight time 10 ~ 15
minutes.
- Low altitude 100 ~ 800 km, which may cause saturation problems in
LEIA (too many particles).
• Fregat (final stage on a Russian Soyuz rocket)
-Soyuz final stage Fregat completes several orbits after the launched satellite is
separated.
- Orbit depends on satellite orbit.
LEIA
Microshutters for particle velocity measurements: Modelling and fabrication
LEIA (Low Energy Ion Analyzer)
LEIA will be based on an existing miniaturized ion mass spectrometer design SWIM
(Solar Wind Monitor) developed for the Indian Chandrayaan-1 mission to the Moon
(launch 2008).
SWIM characteristics:
• Energy range ~10 eV – 15 keV
• Field-of-view 180° × 9 °
• Mass ~400 g
• Power ~1.5 W
Microshutters for particle velocity measurements: Modelling and fabrication
LEIA (Low Energy Ion Analyzer)
LEIA will be based on SWIM but with:
• the START CEM replaced by a MEMS shutter,
• newly developed high voltage optocouplers, and
• partly based on “commercial-off-the-shelf” (COTS)
components.
MEMS
shutter
Microshutters for particle velocity measurements: Modelling and fabrication
MEMS shutter design
Based on resonant vibrations of a grated moving
layer in between two static layers.
Static
Static
Parameter
Sensor specifications
Energy resolution, DE/E, %
Mass resolution, DM/M, %
Mass (min), amu
Mass (max), amu
Energy (min), eV
Energy (max), eV
TOF distance, cm
TOF specifications
TOF (min), ns
TOF (max), ns
Shutter characteristics
Frequency (min), KHz
Open time (max), ns
Transperancy (max)
Duty cycle
Efficiency
Value
7
20
1
32
50
10000
3.8
28
2204
227
2.62
1.85E-03
1.19E-03
2.20E-06
Microshutters for particle velocity measurements: Modelling and fabrication
MEMS shutter design
5mm opening
}
1mm opening
Bonded wafer
}
SOI wafer
Moving layer
Complicates
process
1mm opening
Passivly closed
(not aligned with
device layer)
Fixed electrode
Opening slits dimensions of SOI wafer
SOI device layer thickness = 10 mm
80 mm
30 mm
1 mm
Attached to fixed frame
Released
plate
Microshutters for particle velocity measurements: Modelling and fabrication
105 mm
10 mm
90 mm
60 mm
105 mm
5 mm
85 mm
20 mm
Microshutters for particle velocity measurements: Modelling and fabrication
Pin out (TBC):
•
•
•
•
•
HV MEMS area A (~200 V)
Position sense MEMS area A (<pF)
HV MEMS area B (~200 V)
Position sense MEMS area B (<pF)
Ground
•
•
•
Reference C plate 1
Reference C plate 2
TC1A (Thermocouple mounted on
MEMS housing or close to)
TC1B
•
Microshutters for particle velocity measurements: Modelling and fabrication
Microshutters for particle velocity measurements: Modelling and fabrication
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