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Monolithic Instruments(New opportunities for wafer fabs)
November 12, 2003
Jeremy TheilAgilent Technologies(jeremy_theil@agilent.com, tel: 408 553-4495)
Monolithic Instruments- Jeremy TheilPage 2sA
Outline
Trend in Manufacturing and InstrumentationDefinition of Monolithic InstrumentsExamples
Elevated Photodiode ArraysOLED MicrodisplaysDigital Micromirrors
Manufacturing/Integration ChallengesFuture Opportunities
Monolithic Instruments- Jeremy TheilPage 3sA
Product Trends
InstrumentationReduced system size.Increased computational power.Increased operational speed.Improved levels of process control.Improved reliability of manufacturing systems.Reduced system cost.
Largely Enabled by Integrated Circuits!
Integrated CircuitsReduced system size.Increased computational power.Increased operational speed.Reduced transducer size.Novel solid-state transducers/actuators.Reduced system cost.
Monolithic Instruments- Jeremy TheilPage 4sA
Semiconductor Manufacturing
Current Manufacturing TolerancesWafer flatness: < 100nm across a 300 mm wafer.Metal impurity concentration: < 1 x 1010 cm-3.Stacking fault density: < 1/cm2.Layer-to-layer alignment tolerance: < 25 nm.Linewidth control: 3 nm 3σ.Minimum feature half-pitch: 100 nm.Film thickness control: < 4% 3σ over 300 mm.
Current typical high-volume CMOS device specs.Transistor Density: ~9 x 107 transistors/cm2.Operating Frequency: ~1.7 GHz.Manufacturing Cost: ~ $32/cm2.
$3.6x10-7/FET
Monolithic Instruments- Jeremy TheilPage 5sA
Value of a Semiconductor Mfg. Platform
~$2 x 10-1
/switch
~ 10 µm
100 µm
Machining Mfg
200,000:1
40,000:1
400:1
Mach./Semi.
$1 x 10-6/FETManufacturing Cost
< 25 nmAlignment Tolerance
0.25 µmMinimum Feature Size
Semiconductor Mfg
For the number of devices made, a semiconductor fab is the most precise and least expensive manufacturing environment.
Monolithic Instruments- Jeremy TheilPage 6sA
Definition of Monolithic Instruments
Monolithic instruments are miniaturized systems, combining conventional integrated circuits with novel solid-state components, that interact with their physical environment.
� Concept- Incorporate several instrumentation system functions onto a single die.
�Transducer/actuator�Driver (analog function)�Analog/Digital interface�Signal processing�Data analysis�I/O
Monolithic Instruments- Jeremy TheilPage 7sA
Classes of Monolithic Instruments
Pre-integrated circuit.During integrated circuit fabrication.Post-integrated circuit fabrication.
Adapted from: H. Balthes, and O. Brand, Proceedings of 14th Eurosensors XIV, p1 (2000).
Monolithic Instruments- Jeremy TheilPage 8sA
Monolithic Instrument Examples
Some types of monolithic instruments that have been fabricated include:
a-Si:H photodiode arrays.Organic LED micro-arrays.Digital Micromirror Devices.Liquid-crystal microdisplays.Bio-assay array systems.Inter-cellular communications.
Components proposed for future monolithic instruments include:
Thin-film bulk acoustic resonators.Photonic crystals.Planar light-guide systemsGroup IV-based LEDs.SQUID magnetometers
Monolithic Instruments- Jeremy TheilPage 9sA
Fabricated Monolithic InstrumentsInkjet heads (Hewlett-Packard, Loveland and Corvallis).Digital micromirror displays (Texas Instruments).DNA microarray detectors (Infineon).Direct neuron communicators (Infineon).a-Si:H photodiode arrays (Agilent).Organic LED microdisplays (Agilent, e-magin).
Texas Instrument’s DLP© TI 2003 Neuron Communications
© Infineon 2003
a-Si:H PhotodiodeContact
Interconnect
Si Substrate
a-Si:H Photodiode array(Agilent Technologies)
SXGA OLED microdisplay. Agilent Technologies
Monolithic Instruments- Jeremy TheilPage 10sA
Advantages of Monolithic Instruments
Better performance.Improved signal integrity.Access to novel transducer technology.
Smaller.Cheaper.
What we have come to expect from improvements in integrated circuit technology can be applied to instrumentation systems.
Monolithic Instruments- Jeremy TheilPage 11sA
Monolithic Instrument Technologies
Elevated Photodiode Arrays.OLED Microdisplays.Digital Micromirror Arrays.
Monolithic Instruments- Jeremy TheilPage 12sA
a-Si:H Elevated Photodiodes
Hydrogenated amorphous silicon is a deposited semiconductor.Bandgap ~1.8 eV.
AdvantagesHigher QE.Tunable spectral response.Lower thermal effects.Higher fill factor.Cheaper imager.
DisadvantageSubject to metastabilities that can affect performance (Staebler_Wronski Effect).
Monolithic Instruments- Jeremy TheilPage 13sA
Dielectric Isolation Interconnect
InsulatorTransparent Conductor
Top contact conductor
p-type
n-type
i-type
Bottom Contact
Two extra masking levels.Requires a dry etch with high selectivity between two conductivematerials.
Monolithic Instruments- Jeremy TheilPage 14sA
TFT-Based Monolithic Interconnections
R. A. Street (ed.), Technology and Applications of Amorphous Silicon. Springer, p 162 (2000).
Monolithic Instruments- Jeremy TheilPage 15sA
Local-via Monolithic Interconnect Structure
Transparent Conductor
p a-Si:H
i a-Si:H
n a-Si:H
Bottom Contact
IC Passivation
Top Conductor Contact
US Patent 6018187
Monolithic Instruments- Jeremy TheilPage 16sA
Elevated a-Si:H Photodiodes- Pixel Size Reduction
a)
c-Si 3T Pixel a-Si:H 3T Pixel
Monolithic Instruments- Jeremy TheilPage 17sA
Integrated a-Si:H Photodiode/CMOS Stack
0.35 µµµµm 4LM CMOS process. 5.9 µµµµm square pixel, on a 7 µµµµm pitch.Interpixel isolation created by etching of the n-layer a-Si:H.Planarized passivation layer.
Photodiode Array
Si substrate
Interconnect
Pixel contact viaPassivation
Monolithic Instruments- Jeremy TheilPage 18sA
a-Si:H Material Properties
0 100
1 1016
2 1016
3 1016
4 1016
5 1016
0.70 0.80 0.90 1.00
g(E)
(cm
-3 eV
-1)
Ec - E (eV)
J. Theil, D. Lefforge, G. Kooi, M. Cao, G. Ray, 18th ICAMS Proc., J. Non-crystalline Solids, in press, 2000.
Integrated DOS ~2.5 - 4 x 1015
cm-3.Mid-gap peak ~ 0.88 eV from the conduction band edge.
A second peak at ~ 0.83 eV.1.85 eV band-gap.Ea ~ 0.9 eV.EU ~ 56 meV.
Deposition Rate > 30Å/s.
Monolithic Instruments- Jeremy TheilPage 19sA
Effect of p-layer thickness on quantum efficiency
0
0.2
0.4
0.6
0.8
1
400 450 500 550 600 650 700
200A p-Layer
100A p-Layer
Wavelength (nm)
Qua
ntum
Effi
cien
cy (e
l/ph)
Monolithic Instruments- Jeremy TheilPage 20sA
Effect of layer doping on quantum efficiency
0
0.2
0.4
0.6
0.8
1
400 450 500 550 600 650 700
AA008 Spectral Response(Effect of B Doping)
LD p Layer (08)Control (09)LDp LDn (12)No n-layer (20)
Wavelength (nm)
Qua
ntum
Effi
cien
cy (e
l/ph)
Monolithic Instruments- Jeremy TheilPage 21sA
Dark Current Components
Two components of dark current:
Junction leakage.Array edge leakage.
Guard ring prevents edge current from reaching the array.
Sweep guard ring and area diode together.
Assume: Ix = 0.IE = IA Aring/Aarea diode.
IE IxIAIB
ιctrιito ιring
Monolithic Instruments- Jeremy TheilPage 22sA
Dark Current Density vs Electric Field
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
0.0E+00 5.0E+04 1.0E+05 1.5E+05 2.0E+05 2.5E+05Electric Field (V/cm)
Cur
rent
Den
sity
(A/c
m2)
9000A7500A5500A4000A3000A
Monolithic Instruments- Jeremy TheilPage 23sA
Structures and Junction Parameters
n-layer thickness: 500Å. ([P] 2 x 1020 cm-3)i-layer thickness: 3000 to 9000Å. (5500Å default value)p-layer thickness: 200Å. ([B] 7 x 1019 cm-3)
Guard ringArea Diode
Edge Intensive Diode
Monolithic Instruments- Jeremy TheilPage 24sA
Effect of Pixel Edge Length on Reverse Bias Current (3000Å I-layer)
1.E-12
1.E-11
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E-05
0 2 4 6 8 10Voltage (V)
Cur
rent
Den
sity
(A/c
m2)
1.23E+06 microns5.77E+05 microns1.94E+05 microns5.95E+04 microns2.11E+04 microns3.84E+03 microns
Monolithic Instruments- Jeremy TheilPage 25sA
Stacked Elevated Photodiode Concept
Monolithic Instruments- Jeremy TheilPage 26sA
Optical Response of Stacked Diode Elements
0
0.2
0.4
0.6
0.8
1
400 450 500 550 600 650 700
800A i2000A i9000A i 2000A i Filter9000A i
Qua
ntum
Effi
cien
cy (e
-/ph)
Wavelength (nm)
Monolithic Instruments- Jeremy TheilPage 27sA
a-Si:H Color Sensor Image (640x480 4.9 x 4.9 µµµµm pixel, 1900 lux)
Monolithic Instruments- Jeremy TheilPage 28sA
OLED MicrodisplaysOrganic Light-Emitting Devices (OLEDs)
Charge transport mechanism: localized state-based hopping.Use for large area emissive displays, fabricated using evaporation or printing.Just gaining acceptance.Has lifetime issues.
ApplicationsEyepiece imagers (digital cameras).Eyeglass displays.
ComputersInstrumentation
Advantages over LCD microdisplaysSmallerBrighter (more power efficient).Less expensive (fewer components required).
Thanks to Howard Abraham for driving the Ft.Collins Development
Monolithic Instruments- Jeremy TheilPage 29sA
Microdisplay Systems
LEP
CMOS SiliconAPIX
Value Proposition:S impler, Cheaper, Brighter
M icrod isplay Based onLight Em itting Polym ers
LCD/LED-based Microdisplays
Monolithic Instruments- Jeremy TheilPage 30sA
Organic LED Materials
Organic LED’s: Materials and Devices
Alq3 (ETL, EML)NPD (HTL) R-PPV (EML)
Polymers (spin cast)
HTL: conducing polymers (PDOT, PANI)ETL, EML: polyphenylenevinylenes, fluorenes
CDT, Philips, Uniax, Dow Chemical, DuPont
Small Molecules (vacuum evaporated)HTL: metal-phthalocyanines, arylamines (CuPc, NPD)ETL, EML: metal chelates, distyrylbenzenes
Eastman Kodak, Pioneer, Idemitsu Kosan, Sanyo, FED Corp., TDK
NO
NO
Al O
N
N N
R1R1
n
Polyfluorene (EML)
R1
R1n
OLEDs rely on organic materials(polymers and small molecules)that give off light when tweakedwith an electrical current
Low work function cathode (Ca, Mg, Li/Al)
High workfunction anode(ITO, Au, Pt)
V
Glass
HoleTransport
Layer
ElectronTransportEmission
Layer
Light
Operating voltage ~10V Operating voltage ~5V
Monolithic Instruments- Jeremy TheilPage 31sA
Organic Electroluminescence
CDT: http://www.cdtltd.co.uk
Organic electroluminescence by charge injection
� Hole injection from high work function transparentanode (ITO) and transport through HTL
� Electron injection from low work function cathode(Ca, Mg, LiF/Al, CsF/Al) and transport through ETL
� Since IP < EA electrons are blocked by HTL andholes tunnel to ETL
� Formation of excitons and light emission from ETL
� Diode-like I-V (no light on reverse bias)
� Low turn-on voltage ( ~ 2 V)� Operating voltage >> turn-on voltage
Charge Injection limitationsCharge Transport limitations
� Efficiency1-5% ph/el1-22 lm/W
LUMO
HOM O
Cathode (Ca, Mg)(~ 2.9 - 3.7 eV)
HTL ETL, EML
++ +++
+
Anode (ITO)(~ 4.8- 5.1 eV)
+
HOMO
DIP
LUMO
DEA
Polymer OLED
400 500 600 7000.0
0.2
0.4
0.6
0.8
1.0 EL PL
125 nm
Lum
ines
cenc
e in
tens
ity (
arb.
uni
ts)
Wavelength (nm)
NPD/Alq3
-
Monolithic Instruments- Jeremy TheilPage 32sA
OLED Diode Construction
Process Overview for APIX/LEP Microdisplay
Emitted Light
APIX Active MatrixCircuit on Silicon
Light Emitting Polymer(Diode)
Cathode (Semitransparent)
S eal Layer (Transparent)
Device Layout:
ANODE ANODE ANODE
Light Emitting Polymer (Diode) Electrica l Schematic
Monolithic Instruments- Jeremy TheilPage 33sA
OLED Challenges
Environmental sensitivity.Device lifetime.
Monolithic Instruments- Jeremy TheilPage 34sA
OLED Diode Structure
Process Overview for APIX/LEP Microdisplay
Specific Fabrica tion Steps (sequence is bottom up):
• Functional te s t, Mount chips to daughter board, Wirebond pads to board, Final te s t
• Encapsula te ca thode with seal process s teps . N2atmosphere .
• Thermally evaporate semitransparent ca thode us ing die-s ized shadow mask. N2 a tmosphere .
• S pin Electron Transport Layer (a lso the Emiss ion Layer)light emitting polymer. N2 a tmosphere .
• Bake P EDOT (180ºC, 1 hr).• S pin Hole Transport Layer (PEDOT).• S urface clean (IP A/O2 Plasma).• Final meta lliza tion optimized for anode and bonding
pads . Anodes form re flective pixels . Functional te s t.
P rocess APIX on 6” or 8” s ilicon wafers .APIX Active MatrixCircuit on Silicon
P EDOT Layer (HTL)
P olymer Layer (ETL, EML)
Semitransparent Cathode Layer 2
Semitransparent Cathode Layer 1
Transparent Passivation Layer 1
Transparent Passivation Layer 2
Device Layout:
ANODE ANODE ANODE
Monolithic Instruments- Jeremy TheilPage 35sA
OLED Microdisplay Driver Circuits
Pulse-width modulation pixel driver circuit.
Monolithic Instruments- Jeremy TheilPage 36sA
OLED Microdisplay Operation
© MGM
© MGM
Monolithic Instruments- Jeremy TheilPage 37sA
Digital Micromirrors
Invented at Texas Instruments in 1987 (by Larry Hornbeck).Build hinged mirrors from BEOL metallization over SRAM pixels. Operates by electrostatic attraction between mirror and pixel electrodes.
Monolithic Instruments- Jeremy TheilPage 38sA
Digital Micromirror- Construction
© Texas Instruments
Monolithic Instruments- Jeremy TheilPage 39sA
Digital Micromirror- Schematic
© Texas Instruments
Monolithic Instruments- Jeremy TheilPage 40sA
Digital Micromirror- Mechanics
© Texas Instruments
Monolithic Instruments- Jeremy TheilPage 41sA
Digital Micromirror- Applications
Projections DisplaysDigital Movie ProjectorsDigital Printing and Photofinishing3D Non-holographic displaysMaskless photolithography
DNA sequencingBroadband switchingHolographic storage… Anywhere LCD can be used, with higher contrast.
http://www.dlp.com/dlp_technology/images/dynamic/white_papers/152_NewApps_paper_copyright.pdf
Monolithic Instruments- Jeremy TheilPage 42sA
Integration ChallengesKnown Issues
Material compatibility with the “nominal” process flow.Adverse effects of the standard structures.Adverse effects of the new structures.
Manufacturability of new unit modules.Materials optimization.
Material performance considerations.Integration compatibility considerations.
Unknown IssuesThere will be plenty of them.We encountered 8 major issues in one project.
Example: The 9 causes of adhesion failure.
Expect the unknown!
Monolithic Instruments- Jeremy TheilPage 43sA
The Future
Integrated circuit manufacturing platforms can be extended to make monolithic instruments.Many classes of monolithic instruments can be created.The attributes of monolithic instruments enable hundreds of new applications.
Low costSmall size
There are plenty of opportunities out there.Who is going to take advantage of them?
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