mems devices – design, packaging and production slide 1 mems devices – examples of design,...

MEMS Devices – Design, Packaging and Production Slide 1

MEMS Devices – Examples of Design, Packaging and Production

Per Ohlckers

SINTEF Microsystems and University of Oslo

Picture shows a silicon microphone in

development by the start-up company 54.7


Outline of talk

• Mainly a presentation of Norwegian MEMS activities

• Main challenges of the Microsystem/MEMS industry

• Examples of MEMS devices

• Future and Conclusions: A strong market pull will stimulate the needed maturing of the Microsystem/MEMS industry and its technologies

Picture shows details of the SP13 tyre pressure sensor from SensoNor


Applications for Applications for MEMS/MEMS/Microsystems:Microsystems:• The biomedical market

– Blood pressure sensors• The space, defence and avionics markets

– Accelerometers for rocket navigation – Micro gravity sensor– Gyroscopes for navigation

• The agriculture electronics market – Automotive sensors used in tractors, harvesters etc.

• The off-shore oil exploitation market – High pressure measurement in oil wells – Sea wave sensor

• The automotive market– Acceleration microsystems for air bag systems– Tire pressure microsystems

• The data and peripheral market– Disk drive write and read heads

• The consumer market– Photo diodes in cameras– Level measurement in white goods appliances.


Market for Microsystems/MEMS Devices

Ref.: Nexus Market report


Norwegian Microsystems/MEMS activities

• Main players:– SensoNor– SINTEF Microsystems– Startups

• NORCHIP• Presens• Photonyx • Lifecare• 54.7

– Universities• NTNUI, Trondheim• University of Oslo

• New initiative: NMC, Norwegian Microtechnology Centre– Picture shows the future Microtechnology Research Laboratory in Oslo,

construction started this autumn


Example: SP80 Pressure Sensor

• Vintage from the early eigthies – but still in production • Developed at SINTEF (earlier Center for Industrial Research),

Norway and manufactured by Capto, subsidiary of SensoNor (earlier ame), Horten, Norway.

• This sensor visualises the main features and limitations of micromechanical sensors, and points out pressure sensing as a main application for these kinds of sensors.


The SP80 Silicon Chip Set - Drawing

• Consists of diaphragm chip sealed to a support chip which is mounted on top of a glass tubing acting as a mounting stand as well as a pressure port


The SP80 Silicon Chip Set - Picture

• Consists of diaphragm chip sealed to a support chip which is mounted on top of a glass tubing acting as a mounting stand as well as a pressure port


SP80 Package, continued

• Cross-sectioned view of the SP80 Pressure Sensor packaged in a transistor header with a top chip containing a vacuum reference chamber

Pressure Connection Tubing

Pressure

Silicon Chip Set Gold WirebondsCap

Transistor Header

Connecting Pins


SP80 Schematic

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• The SP80 schematic consists of 4 ion implanted piezoresistors in a full Wheatstone bridge configuration as the electronic sensing element. In addition, a temperature measuring resistor and a heating resistor are implanted on the same chip, to compensate or thermostat the chip to minimise thermal drifts


Picture of SP80 in Transistor Package

• Comment: The Norwegian coin is approximately the size of Ø10 mm


Top10 Success FactorsTop10 Success Factors• 1. 1. Batch organised processing technologyBatch organised processing technology

• 2. 2. Microelectronics manufacturing Microelectronics manufacturing infrastructureinfrastructure

• 3.3. Research results from solid state technology Research results from solid state technology and other and other

related fields of microelectronics related fields of microelectronics

• 4.4. MicromachiningMicromachining

• 5. 5. Wafer and chip bondingWafer and chip bonding

• 6. 6. Mechanical material characteristicsMechanical material characteristics

• 7.7. Sensor effectsSensor effects

• 8.8. Actuator functionsActuator functions

• 9.9. Integrated electronicsIntegrated electronics

• 10.10. Combination of featuresCombination of features


Bottom10 Limiting FactorsBottom10 Limiting Factors•1.1. Slow market acceptanceSlow market acceptance•2. 2. Low production volumesLow production volumes•3.3. Immature industrial infrastructureImmature industrial infrastructure• 4.4. Poor reliabilityPoor reliability• 5. 5. Complex designs and processes Complex designs and processes • 6. 6. Immature processing technologyImmature processing technology• 7.7. Immature packaging and Immature packaging and

interconnectioninterconnection technologiestechnologies

• 8.8. Limited research resourcesLimited research resources• 9.9. Limited human resourcesLimited human resources• 10.10. High costsHigh costs


Manufacturers of Microsystem/MEMS Devices

• The industry structure is highly diversified both in size, technological basis and organisation type.

– Traditional sensor manufacturers have seen micromechanical sensors as a natural expansion of their technological basis, and have taken up research and production of these sensors as a part of their activity.

– Semiconductor companies have entered this market as an expansion of their integrated circuit activity, since they already have most of the needed equipment and the appropriate marketing channels.

– System companies or original equipment manufacturers which see micromechanical devices as a way to boost their systems.

– "Start ups", companies having micromechanical devices as their main business idea.

• There are of course companies that does not fit into any of these types and some are someplace in between these types.


Example: The 54.7 Photoacoustic Gas Sensing Silicon

Microsystem


Motivation:

• Microsystem technology can give cost effective photoacoustic gas sensors with high performance

– Batch organised manufacture for low cost– Silicon micromachining for high performance and small size– Piezoresistive microphone for high-sensitivity sensing of the

photoacoustic signal– Multistack wafer anodic bonding to produce the hermetic target

gas chambers– etc

• The start-up microsystem company 54.7 started its operation on September 1, 1999, with its first venture to commercialise this patented scheme for photoacoustic gas sensing modules using microsystem technology


Technology of 54.7• The 54.7 Photoacoustic Gas Sensing Technology

– Using a silicon micromachined acoustic pressure sensor with an enclosed cavity with the gas species to be measured as a selective filter. This intellectual property is protected with 3 patents.


Technology of 54.7, continued

• Absorbed modulated IR radiation is converted into acoustic signal in a sealed gas chamber

The photoacoustic principle

Window

Microphone ~ Pressure sensor

Gas

ModulatedIR source


Conventional Photoacoustic Gas Sensor

• Well known with high performance at high cost

IR-filterMicrophone

IR-window

Mirror

Microphone

Display Lock-inamplifierOscillatorPower

supply

PulsedIR source

Valve

Valve

Pump

•


Photoacoustic Technology of 54.7

• Increased amount of target gas present in the absorption path gives a correspondingly decreasing photoacoustic response in the sealed target gas chamber due to the transmission loss

• Explain better! Include absorption lines etc!!!

Pressure sensor (microphone)

Optical window

Sealed target gas chamber

Read out electronics Absorption path

Modulated IR emitter


Photoacoustic Response

• Decreasing PA signal with increasing gas concentration in absorption path. Here shown at 8 HZ modulation.

-20 0 20 40 60 80 100 120 140 160 180

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ut v

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PA-signal

Emitter voltage

Emitterradiation

Response without gas in absorption path


The Diamond-like Thin Film/Silicon Micromachined IR Emitter

• Manufactured by Patinor Coatings– Based upon Diamond-Like Carbon (DLC) thin film heating resistor on

silicon micromachined diaphragm structure:1: Bonding pads 2&3: SiO2 4: Si3N4 5: DLC film

– Using a CVD process to deposit the DLC thin film– Pulse modulated high speed broad band grey body IR emission– Working temperaure about 700-800 C– High reliability


CVD Process for the IR Emitter

• Silicon-organic liquid (C2H5)3SiO[CH3C6H5SiO]3Si(CH3)3 (PPMS) is

used as a plasma-forming substance of the open plasmatron

• Doping by molybdenum is done during plasma deposition process wafer by magnetron sputtering of a MoSi2 target in argon atmosphere

• Pressure is about 510-2 Pa, the magnetron current is about 2 A, the plasmatron arc discharge current is about 6 A

• By changing those deposition parameters it is possible to modify the resistance of the IR emitters


Principle of a Microsystem based Photoacoustic Gas Sensing Cell (Early Prototype)

• The photoacoustic sensing microsystem is enabled by packaging a silicon micromachined acoustic pressure sensor chip in a transistor package

10.0 mm

TO-header

IR radiation

4.0 mm

Silicon micromachinedacoustic pressure

sensor chip

Target gas

WindowAbsorptionchamber

Transistor cap


Silicon Microphone Prototype

• Designed by SINTEF and 54.7

• Piezoresistive with centre boss structure

• Manufactured by SensoNor with their Europractice/NORMIC multiproject wafer foundry services


Silicon Microphone Prototype: Design and Process

• Piezoresistive with centre boss structure– Chip size is 6 mm x 6 mm. Diaphragm diameter is 2 mm

• SensoNor/NORMIC process: Process E/ MPW : Combined Diaphragm- and Mass-Spring-based Piezoresistive Sensor Process

– 3 micrometer epitaxial layer– 2-level etch stop using anisotropic TMAH process with electrochemical etch stop at 3 and 23 micrometers– Buried piezoresistors with 480 Ohm/square sheet resistance– Anodic bonded triple stack glass-silicon-glass structure

Glass top chip

Si diaphragm chip

Glass bottom chip


The 54.7 photoacoustic gas sensing cell design

• Cell with silicon or electret microphone– Electret microphones model 9723 from Microtronic used in present prototypes

IR-emitter Microphone

Perforated aluminum tube

IR window or filter

Thermopile or pyroelectric IR reference sensor

90 mm

Target gas

6mm IR radiation Absorption path


Sensor Module Design

• Sensor module with the gas sensing cell mounted on a surface mount printed circuit board with analog and digital electronics for monitoring, control and interface

• Size approximately 70mm x 20mm x 10mm


Preliminary Test of Silicon Microphone versus Electret Microphone

• Comparable signal-to-noise performance

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Electretmicrophone

Siliconmicrophone


Test of the DLC IR Emitters

• Power efficiency about 0.1


IR Emitters: Radiation Spectrum

Useful IR spectrum from around 1 to around 10 micrometers


Main characteristics of the IR Emitters• Resistance value: Nominal 55, from 35 to 125 Ohms• Supply voltage: From 5 up to 12 V• Power consumption: 0.5 – 1.0 W• Maximum frequency modulation of the emitted

energy: 200 Hz (~100% modulation at 10 Hz)• Working temperature of film resistor: 500-800 oC,

with header temperature not exceeding 70 oC• Warm-up time: < 30 s• The emissivity factor of the emitting surface: ~0.8• Emitting efficiency (=3-14 micrometers): ~10%• Life time: Mean Time Between Failure (MTBF) of

more than 25 000 hours (more than 3 years)


Preliminary experimental results of CO2 module prototype

Graph of 15 hours measurement (one sample per minute) Lab test: Increased CO2 at start and at inspection. Resolution around 0.3 ppm. Accuracy around ±10ppm?

0 200 400 600 8000.986

0.988

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Temp

Vref

Vref-temp-c

Vg

Vg-temp-c

Vg-temp-ref-c

0.002 approximately:25 ppm CO2

1 oC


Status of this gas sensor development

• The concept is promising for commercialisation• Low cost, high selectivity, and high sensitivity can be achieved

– Example: CO2 measured with around 10 ppm accuracy and 0.3 ppm resolution

• Potential show stoppers• Long term drift and thermal effects

– Example: Some thermal effects are yet to be understood and minimised

• Further work• Long term stability need to be verified further

• Thermal effects will need to be investigated, reduced and compensated

• Low cost microsystem production technology need to be further developed


Example: Digital Micromirror Device (DMD) from Texas Instruments

• The device is using very advanced surface micromachining of thin Al alloys on Si substrates containing CMOS drive electronics


Picture of the packaged DMDs

• The DMDs are pixel devices• Here are the VGA (640x480), the SVGA (800x600) and the XGA (1024x768) devices shown


Principle of Operation for the DMD

• The hinge system of each pixel structure enables electronic control mirror position.


Picture of Digital Micromirror Device

• The device is packaged in an elastomer connect package with a glass window. Here shown mounted on a PCB with back end drive electronics


The Davis DPX 16 Projector using the TI Digital Micromirror Device

• XGA resolution (1024 x 768 pixels)• 2.3 kg weight• 1000 Lumens brightness


Example: The SP13 Tyre Pressure Sensor from SensoNor

• Fully integrated temperature and pressure sensor • Internal State Machine • Patented sensor design • Pressure sensor:

Range: 50 – 637.5 kPaResolution: 2.5 kPaAccuracy: +/- 10 kPa


Example: Microgyro from SensoNor

• Challenging signal-to-noise ratio• High vacuum sealing to obtain high Q factor


PreSens: High Pressure Sensors

Sensor conceptSilicon piezoresistive sensor elementHigh output signalHigh overload capabilityDynamic range > 130 dB

Pressure sensingFull scale range 0 - 50 bar to 0 - 2000 barPressure accuracy 0.05 %FS

Temperature rangeStandard T: -40 °C to 130 °CHigh T: -40 °C to 200 °CTemperature sensing by Rbridge(T)Temperature accuracy 0.3 °C

Signal conditioning circuitryCustomized steel housing

With or without diaphragm to isolate from aggressive mediaSmall dimensions (from 2 cm3)


• Main application: Imaging systems like projectors

• Optical modulators

Photonyx


NORCHIPmicroTAS (Total Analysis System) for biotech applications


Future and Conclusions:

• A strong market pull will stimulate the needed maturing of the Microsystem/MEMS industry and its technologies

• The Microsystems/MEMS industry is maturing into a separate industry

• A lot of innovations taking place these days – some examples have been presented

• The Norwegian Microsystem/MEMS activities are promising growing

mems devices – design, packaging and production slide 1 mems devices – examples of design,...

Documents

production slide

mems devices design

sensonor slide

autumn slide

pressure port slide

microsystemsmems devices

sp80 pressure sensor

vacuum reference chamber