MEMS and Industry-University CollaborationMasayoshi Esashi

Department of Nanomechanics, Tohoku University, Sendai, Japan

1. Introduction 2. Gyroscope3. Wafer level packaging and electrical feedthrough4. Multi probe data storage and monolithic stage5. Multi-column electron beam lithography system6. Micro-Nano mold press 7. MEMS for power supply 8. Small volume supply of MEMS

ＩＳＦＥＴ(Ion Sensitive FET)（T.Matsuo, M.Esashi, K.Iinuma, Tohoku region meeting of Electrical Eng. (1971)）

ISFET (Ion Sensitive Field Effect Transistor)(M.Esashi, Supplement to the J.J.AP.,44 (1975),339-343)

Catheter tip pH、PCO2 sensor(K.Shimada et.al., Med.& Biol.Eng. & Comput.,18 (1980))

pH、PCO2 monitor catheter using ISFET

Integrated blood analysis system(S.Shoji et.al., Sensors and Actuators, 14 (1988) pp.101-107)

Antibody H.pyloripH change by ammonia (reaction product) is measured using the ISFET

Urea

H.pylori detector using ISFET (H.pylori causes stomach ulcer)

Portable pHmeter

MEMS process facility for 20 mm wafer (users : 25 laboratories)

Dr.Ono (Nanomachining) Dr.Tanaka (Power MEMS) Dr.Totsu (Catheter sensor)

Staff 4 and Pos-doc 2

Students Dr.13, Mr.10 and Undergraduate students 5

Dispatched researchers from industry Full time 10 and Part time 17

(Foreign people 21： Korea 7, China 5, Taiwan 3, Germany 3, USA 2, Canada 1)

2. Gyroscope

Resonating gyroscope

Electrostatically levitated rotational gyroscope

Vibrating gyroscope (yaw rate sensor) for vehicle stability control

1992-1997Two researchers from Toyota stayed in Tohoku University for collaborative development of vibrating gyroscope

Resonating gyroscope fabricated using Si deep RIESi deep RIE system

(M.Takinami, 11th Sensor Symposium, (1992) p.15)

Semiconductor Capacitance Type Accelerometer with Electrostatic Servo Controller(S.Suzuki, S.Tuchitani, K.Sato, Y.Yokota, M.Sato and M.Esashi

Sensors and Actuators,A21-23,(1990))

Electrostatic servo capacitive 3-axis accelerometer(Johno et.al., MEMS’94 )

Principle of electrostatic levitation

Electrostatically levitated spherical 3-axis accelerometer

(R.Toda (Ball Semiconductor Inc.) et.al., MEMS’02)

Example of 3-axis acceleration measurement using ball accelerometer

-1.0

-0.5

0.0

0.5

1.0ca

libra

ted

outp

ut [G

]

-180 -90 0 90 180rotation angle about y-axis [deg]

x y z

Projection exposure system using DMD

Maskless exposure sytemElectrode pattern made on a 1mm diameter Si ball

Electrostatically levitating micromotor for rotational gyroscope (disk rotor type) (T.Murakoshi (Tokimec Inc.) et.al., Transducers’99)

Electrostatically levitating rotational gyroscope(disk rotor type) (T.Murakoshi (Tokimec Inc.) et.al., Transducers’99)

10mm

20,000 rpm

Rotor position is capacitivelydetected and voltage is applied to electrode(T.Matsubara et.al., Transducers’93, 50-53)

Rotor

Control Electrodes for z and θ (or φ) axis

Control Electrodes for x (or y) axis

Pad

Rotation Electrodes

Common Electrodes

Island (Feedthrough)

Structure of electrostatically levitaed rotational gyroscope(T.Murakoshi et.al. : Jpn. J. Appli. Phys., 42, Part1 No.4B (2003) pp.2468-2472)

1.5 mm

Rotational gyroscope levitated electrostatically using high speed digital signal control

MESAG-1 (Micro Electrostatically Suspended Accelerometer Gyro)(Simultaneous measurement of 2 axes rotation and 3 axes acceleration)

(Tokimec Corp., T.Murakoshi)

Rotor diameter1.5mm 74,000rpm4.3×4.3×1mm

14×14×3mm

Fabrication process of the electrostatically levitaed rotational gyroscope

Performance of of electrostatically levitaed rotational gyroscope

GyroscopeRange: ±150 deg/s

Sensitivity(1LSB): 0.01 deg/s

Noise：0.002 deg/s/√Hz

Offset in temp.range: ±1 deg/s

AccelerometerRange: ±5 G

Sensitivity(1LSB): 0.2 mG

Noise：50 μG/√Hz

Offset in temp.range: ±10 mG

Temp. range: -40－85 ℃

3. Wafer level packaging and electrical feedthrough

Wafer level packaging

MEMS relay

Contactor for wafer probing

Electrical interconnection through Si wafer

Integrated capacitive pressure sensorCircuit integration

(T.Kudoh et.al., Sensors and Actuators A,29 (1991) p.185-193)

Capacitance detection circuit (JTEKT 2006~)

MEMS is value added but small volume

→ Hard to commercialize because of the high cost.

(70% of MEMS cost : packaging, test)

Wafer level packaging→ low cost (minimization of assembly

investment and loss in test)→ small size (chip size encapsulation) → high yield (protection of MEMS

structures during dicing) → reliability (hermetic sealing)→ small loss in test after packaging

Silicon diaphragm capacitive vacuum sensor(K.Hatanaka et.al., 13th Sensor Symposium, 1995)

Vacuum packaging