Summary of Introduction • MEMS (U.S.) Sometimes Microsystems in Europe. • MEMS=MicroElectroMechanical Systems • Very broad definition in practice: Mechanical, Electrical, Optical, Thermal, Fluidic, Chemical, Magnetic. • Generally systems created using microfabrication that are not integrated circuits. Many (but not all) of the microfabrication techniques were borrowed from the IC industry. • Market is smaller than IC market, but more diverse and growing faster.
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Summary of Introduction MEMS (U.S.) Sometimes Microsystems in Europe. MEMS=MicroElectroMechanical Systems Very broad definition in practice: Mechanical,
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Summary of Introduction• MEMS (U.S.) Sometimes Microsystems in Europe.
• MEMS=MicroElectroMechanical Systems
• Very broad definition in practice: Mechanical, Electrical, Optical, Thermal, Fluidic, Chemical, Magnetic.
• Generally systems created using microfabrication that are not integrated circuits. Many (but not all) of the microfabrication techniques were borrowed from the IC industry.
• Market is smaller than IC market, but more diverse and growing faster.
Some Examples• Accelerometer
– Electrical/Mechanical
• TAS or Micro Total Analysis System– Purifies, amplifies, and detects DNA, for example.
– Fluids/Biochemistry/Optical/Electrical
• TI DLP– Optical/Mechanical/Electrical/Surface Science
– A special type of surface micromachining, not much used in its original form.
– Now sometimes refers to using very thick photoresist to make thick electroplated structures.
Packaging• Ideally, part of fabrication process, then just use a cheap plastic
package.
• Often, a surface micromachined device is bonded to a bulk micromachined package (the cavity to contain the device is etched from the wafer using bulk micromachining).
• Sometimes the package is the most expensive part of the device (pressure sensors, microfluidics). Especially true when the device interacts with the outside environment.
References: Text (brief), Campbell or other IC fabrication text (generally good, but incomplete for MEMS), Madou (specific to MEMS).
Silicon wafer fabrication• Taken from www.egg.or.jp/MSIL/english/index-e.html
Silicon wafer fabrication – slicing and polishing
• Taken from www.egg.or.jp/MSIL/english/index-e.html
Wee
k 1
Wee
k 2
N -type Si wafer <100>
Pre-diffusion cleanPad oxidation
Deposit LPCVD nitride
Spin photoresist
PR
Si N3 4
SiO 2
O 2
SiH ClNH
2 2
3
ECE 1233 PMOS Fabrication Sequence
We
ek 2
Wee
k 3
Expose PR with active area maskand develop
Reactive ion etch nitride layerStrip PR
Pre-diffusion cleanField oxidation
Strip nitride and pad oxideSacrific ial oxidation
OH O
2
2
O 2
CHFO
3
2
Wee
k 3
Wee
k 4
Strip sac ox
Gate oxidation
Deposit LPCVD polysilicon
Poly
PR/etch gate m askStrip PR
O 2
SiH 4
SFO
6
2
LPCVD SystemsTaken from http://www-bsac.EECS.Berkeley.EDU/~pister/245/
Wee
k 5
Wee
k 6
Ion im plant BF 2
+
Pre-diffusion cleanDrive-in/oxidation
PR/etch contact m askStrip PR
CleanSputter deposit A l/1% Si
Al/Si
P doped areas
OH O
2
2
Ar
Wee
k 6
PR /etch metal m askStrip PRAnneal
Source
DrainGate (contact not shown)
Wee
k 1
Wee
k 2
N -type Si wafer <100>
Pre-diffusion cleanPad oxidation
Deposit LPCVD nitride
Spin photoresist
PR
Si N3 4
SiO 2
O 2
SiH ClNH
2 2
3
ECE 1233 PMOS Fabrication Sequence
Wee
k 1
Wee
k 2
N -type Si wafer <100>
Pre-diffusion cleanPad oxidation
Deposit LPCVD nitride
Spin photoresist
PR
Si N3 4
SiO 2
O 2
SiH ClNH
2 2
3
ECE 1233 PMOS Fabrication Sequence
We
ek 2
Wee
k 3
Expose PR with active area maskand develop
Reactive ion etch nitride layerStrip PR
Pre-diffusion cleanField oxidation
Strip nitride and pad oxideSacrific ial oxidation
OH O
2
2
O 2
CHFO
3
2
Wee
k 3
Wee
k 4
Strip sac ox
Gate oxidation
Deposit LPCVD polysilicon
Poly
PR/etch gate m askStrip PR
O 2
SiH 4
SFO
6
2
Wee
k 5
Wee
k 6
Ion im plant BF 2
+
Pre-diffusion cleanDrive-in/oxidation
PR/etch contact m askStrip PR
CleanSputter deposit A l/1% Si
Al/Si
P doped areas
OH O
2
2
Ar
Wee
k 5
Wee
k 6
Ion im plant BF 2
+
Pre-diffusion cleanDrive-in/oxidation
PR/etch contact m askStrip PR
CleanSputter deposit A l/1% Si
Al/Si
P doped areas
OH O
2
2
Ar
Wee
k 6
PR /etch metal m askStrip PRAnneal
Source
DrainGate (contact not shown)
Electrodeposition/Electroplating
SEM of NEU microswitch
Drain Source
Gate
Beam
Drain Gate Source
Beam
Drain
Gate
Source
Surface MicromachinedPost-Process Integration with CMOS20-100 V Electrostatic Actuation~100 Micron Size
IBM 7-Level Cu Metallization (Electroplated)
Packaging• Ideally, part of fabrication process, then just use a cheap plastic
package.
• Often, a surface micromachined device is bonded to a bulk micromachined package (the cavity to contain the device is etched from the wafer using bulk micromachining).
• Sometimes the package is the most expensive part of the device (pressure sensors, microfluidics). Especially true when the device interacts with the outside environment.
Micromachining Ink Jet Nozzles
Microtechnology group, TU Berlin
Bulk micromachined cavities
• Anisotropic KOH etch (Upperleft)
• Isotropic plasma etch (upper right)
• Isotropic BrF3 etch with compressive oxide still showing (lower right)
Taken from http://www-bsac.EECS.Berkeley.EDU/~pister/245/
Taken from: http://www.imm-mainz.de/english/sk_a_tec/basic_te/liga.html
Simple Carbon Nanotube Switch
Diameter: 1.2 nmElastic Modulus: 1 TPaElectrostatic Gap: 2 nmBinding Energy to Substrate: 8.7x10-20 J/nm
Length at which adhesion = restoring force: 16 nmActuation Voltage at 16 nm = 2 VResonant frequency at 16 nm = 25 GHzElectric Field = 109 V/m or 107 V/cm + Geom.
(F-N tunneling at > 107 V/cm)
Stored Mechanical Energy (1/2 k x2 ) = 4 x 10-19 J = 2.5 eV