Outline
Flat-Panel Imaging Arrays • Market and clinical challenges for digital radiography for Digital Radiography • Passive pixel amorphous silicon imaging arrays • Active pixel amorphous silicon imaging arrays Timothy Tredwell, Jeff Chang, Jackson Lai, Greg Heiler, Mark Shafer, John Yorkston Carestream Health, Inc., Rochester, NY 14615, USA • Active pixel LTPS imaging arrays
Jin Jang, Jae Won Choi, Jae Ik Kim, Seung Hyun Park, Jun Hyuk Cheon, Sauabh Saxena, Won Kyu Lee • Silicon-on-glass circuits for future active pixel imaging Advanced Display Research Center, Kyung Hee University, Seoul, Korea arrays
Arokia Nathan London Center for Nanotechnology, University College, London
Eric Mozdy, Carlo Kosik Williams, Jeffery Cites, Chuan Che Wang Corning Incorporated, Sullivan Park, Corning, NY 14831, USA
2
DR: “Digital” Radiography
DR: 1 step acquisition with electrical “scanning”
“Flat panel” and CCD based technology (introduced ~1995)
(Courtesy Imaging Dynamics Corp.)
3 4
Two-Dimensional Projection Radiography The Market Outlook for DR: Rapid Growth
World’s Population is Aging • Still most common exam • >1.5 x 10 9 exams per year • Chest imaging most common
1999 2050 Procedural Volume Trends • An aging population: 2,500 • By 2050, over 25% of the population in North America, Europe, China 2,000 Nuc Med and Australia will be over 60 ULtrasound • For every 1 time a 20-year-old visits a doctor … 1,500 MR …a 60-year-old visits a doctor 26 times 1,000 CT Digital X-ray • Rising incomes in Asia and Latin America will accelerate demand
Procedures (Ms) Procedures 500 Analog x-ray • Emerging economies could go direct to digital - • Cost must be low – significant market opportunity 2001 2002 2003 2004 2005 2006 2007 2008 5 Source: WHO, World Bank 6 Anatomical Noise Anatomical Noise in Projection Radiography
3-Dim 2-Dim &KHVW5DGLRJUDSK 0DPPRJUDSK\
• 3 dim. structure projected into 2 dim. • Overlapping structures obscure clinical details • Anatomical structure noise > x10 detector noise
7 8
Tissue Discrimination: Dual-Energy Imaging Tissue Discrimination: Dual-Energy Imaging
High-Energy Image High-Energy Image 120-150 kVp Bone Image 120-150 kVp Soft-Tissue Image IH IH
w w Low-Energy Image b Low-Energy Image s 60 -90 kVp 60 -90 kVp
Bone Soft IL I IL I Bone H L Soft H L ln I !$ #ln I !" wb ln I ! ln I !$ ln I !# ws ln I ! 9 10
Dual-Energy Increases Conspicuity of Subtle lesions Spatial Discrimination: Tomosynthesis
Utilizes parallax relative motions between shots
(Courtesy: JM Sabol, GE Healthcare and RC Gilkeson, Dept. Radiology Case Western Univ.) 11 12 Chest Tomosynthesis Clinical Example 15 mm hilar nodule not visible in projection image Flat-panel “Cone Beam” CT
16-degree tube angle, 61 projection images, 5 mm slice spacing 5 !"#$%"!&!%'()!*+,'%C%.#"',#$%/�'%'()!*+,'%1*2,''3%4/$&5 4 6
3 7
2 8
1 1
8 2
7 3
6 4 15 mm nodule 5 Detector (Courtesy: James Dobbins, PhD, Duke University Medical Center) 13 14
CBCT Spatial Discrimination CBCT Image Guidance
• Isotropic resolution • Patient dose << CT Pre-Op. • Some soft tissue vis.
Intra-Post Op. Evaluation Needle
PMMA
( D. A. Jaffray and J. H. Siewerdsen, Princess Margaret Hospital , University of Toronto ) 15 16
Advanced Imaging Modality Requirements Key Vectors for Radiographic Detector Development
Dual Energy Tomo-Synthesis Cone-beam CT • 2-D Projection Radiography
5 o Cost (on-glass electronics, digital lithography & fab-less design) 4 6
3 7 o Robustness & weight (robust plastic/metal substrates)
2 8 • Advanced Applications (Dual energy and 3D modalities) 1 1 o Improved sensitivity (SNR) at low exposure (“smart” pixels)
8 2 o Improved spatial resolution (improved x-ray converters) 7 3 o High frame-rate readout (on-glass electronics) 6 4 5 Flexible Substrate Detector Active Pixel Design
Number of 2 Number of ~20 -100 Number of 100’s On-glass Shift Register images images images Total dose 1X Total dose 1X-5X Total dose 1X - 10X+ Dose per image 50% Dose per image 10% Dose per image 1 % – 5 % Frame rate ~5 fps Frame rate ~5-30fps Frame rate ~30 fps 1 mm
17 (Courtesy Dr. T.Jackson PennState)18 Outline DR X-ray Detection
• Market and clinical challenges for digital radiography Indirect Systems Direct System Powdered Phosphor Structured Phosphor • Passive pixel amorphous silicon imaging arrays X-ray X-ray X-ray • Active pixel amorphous silicon imaging arrays +- - -+ + -+ - α-Se • Active pixel LTPS imaging arrays + Photoconductor • Silicon-on-glass circuits for future active pixel imaging arrays
19 20
Signal and Noise vs. Exposure Photosensors for Indirect Radiographic Detectors Projection Radiography: Chest α-Si:H PIN Photodiodes
1.E+08 Al bias line nitride 1.E+07 Signal ITO (electrons) 30 nm P+ α-Si s elec)s 1.E+06 500 nm i α-Si - +
1.E+05 50 nm N+ α-Si Quantum Noise Mo electrode 1.E+04
Electronic Noise Advantages Maximum ignal (elec)&Noise(rms ele ignal 1.E+03 Typ. Entrance • High quantum efficiency Quantum Efficiency Signal Signal Heart Lungs Exposure Exposure 0.12 mR 0.29 mR 7.2 mR 30 mR • Low dark current • 85% quantum efficiency in green • Operated steady-state (no transient) 1.E+02 Disadvantages • QE drops in blue due to absorption in P+ 0.001 0.01 0.1 1 10 100 • P+ not widely available – requires • QE in red decreases due to band edge special process capability Exposure (mR) 21 22
Photodiode characteristics Amorphous silicon TFT characteristics 10 µm to 1 mm photodiode dimensions
10 9 on-off ratio
• Critical for radiographic imaging due to wide exposure range in radiograpic images
• Low on-resistance required for rapid charge transfer from diode
• Leakage current < 1 fA at V DS = 3V required for low smear and low charge loss
However ,
• Low leakage TFT’s are not a standard process at display fabrication lines
• Requires special TFT development and process 23 24 Cross-section of Vertically Integrated DR Array α-Si:H PIN Photodiode in DR Array Spectral Quantum Efficiency
Primary Array Spectral Quantum Efficiency 0.8
M5 : Bias electrode
0.7
316 nm nd 2 passi : SiN x 0.6 125 nm M4 : Top electrode (IZO)
395 nm p-i-n 0.5
130 nm M3 : Mushroom electrode (MoW)
0.4 st 487 nm 1 passivation Quantum EfficiencyQuantum 158 nm M2 : Data electrode (MoW) 130 nm 0.3 Active : a-Si:H
388 nm Gate insulator : SiN x 0.2
145 nm M1 : Gate electrode (MoW)
Glass 0.1
0 350 400 450 500 550 600 650 700 Wavelength (nm)
07/10/2008 Carestream Health Restricted Information 25 07/10/2008 Carestream Health Restricted Information 26 25 26
α-Si:H Imaging Array Noise in α-Si:H Passive -Pixel Array Dark Current Density vs. Bias and Temperature Dataline Thermal Noise Dominates • High M2 dataline resistance Average Array Dark Current Dark Current Histogram at 40 C • High M1-M2 overlap capacitance vs. Bias and Temperature (500 nm nitride) 4 Total Noise 3 x 10 10 8 )
2 40 C -2.5 V bias Data Line Thermal 28 C nces 40C 2 6 10 PD Shot Dataline thermal 4 noise at 9,000 el dominates 1 TFT Shot 10 ~ C*R 1/2 2 TFT Transient Dark Current (pA/cm Current Dark Da 0 Number of Occurrences Number Num • Dataline is in Metal 2, gateline in 10 0 0 -1 -2 -3 -4 -5 0 25 50 75 100 125 metal 1 with 500 nm inter-layer Reset Photodiode Bias (Volts) 2 Dark Current (pA/cm ) dielectric 1/2 • Dataline thermal noise ~ C*R 0 2000 4000 6000 8000 10000 is the largest contributor with e-rms 9,000 electrons noise 27 28
Experimental a-Si Passive Pixel Experimental a-Si Passive Pixel Reduced dataline thermal noise 3X Noise Reduction in Passive a-Si Arrays
Dataline in low- resistance Metal 3X overall noise reduction 0.6 µm PIN diode Total Noise
4X DL noise reduction Dielectric Data Line Thermal 2 µm BCB between TFT & photosensor PD Shot New Design 2 um BCB
New Design TFT Shot 500 nm Si02
Baseline TFT Reset
• 2 µm thick BCB layer or thick nitride dielectric between TFT plane and photosensor 0 2000 4000 6000 8000 10000 plane e- r ms • Planarization of topography • ~40% Reduction in C • Reduced overlap capacitance DL • ~90% Reduction in R • Dataline in metal 5 DL • 4X reduction in data line thermal noise • 500 nm Al for low resistance • 2,000 nm BCB + 400 nm nitride dielectric for reduced overlap capacitance 29 30 Outline Operation of 3T a–Si:H Active Pixel Sensor
• Market and clinical challenges for digital radiography 1. Integration Mode • Photogenerated carriers are • Passive pixel amorphous silicon imaging arrays stored by the internal capacitance of the sensor ( C ). • Active pixel amorphous silicon imaging arrays PIX 2. Readout Mode • Active pixel LTPS imaging arrays • Gain current via AMP TFT is • Silicon-on-glass circuits for future active pixel imaging passed through READ TFT to arrays external charge amplifier.
3. Reset Mode
• Signal charge stored in CPIX is released with the onset of the RESET TFT.
31 June 18, 2009 © Carestream Health Inc. — Confidential 32 32
Advanced α-Si:H arrays α-Si:H Shift Register for Active-Pixel Array 3T Active-Pixel Design with 139 µm Pixel 120 µm pitch α-Si:H Shift Register
30 1st output nd Input 2 output rd th 25 3 output 13 output
20 4th output
15
10
5 • Advantages o Noise Reduction : Dataline thermal noise reduced by charge gain of pixel amplifier (>5 X) OutputOutp Voltage (V) o Speed Increase: Reduction in dataline setting time due to active amplifier 0 • Disadvantages o Yield: 9 X increase in transistor area and ~ 3 additional bias and clock lines -5 o Linearity: Smaller linear range of output vs. exposure 0.0 0.5 1.0 1.5 2.0 o Stability: TFT threshold voltage shift with aging – TFT is amplifier, not a switch Time (ms) 33 34
Noise in Active-Pixel α-Si:H Arrays Limitations of a-Si APS 3-Transistor Active-Pixel Architecture More complex process – lower yield 1T PPS 3T APS
APS backplane requires larger area due to: Requires vertical • Higher transistor count integration using high • Dataline thermal noise reduced 5 X by charge gain of pixel amplifier • Increased number of routing lines • External amplifier noise reduced 5 X by charge gain of pixel amplifier • Larger amplifier TFT for higher gain mask-count process • Largest remaining noise source is reset noise of the photodiode APS backplane has higher transistor density • Lower yield Requires high • Threshold voltage instability in amplifier TFT a serious issue APS backplane uses a-Si TFT as analog circuit yield, stable • Still requires external read-out IC with charge integrating analog front-end element, not as a switch backplane process • High current from active pixel requires large capacitance on AFE – large die area 35 June •18, 2009Sensitive to parameter variation and© Carestream shift Health Inc. — Confidential 36 36 Limitations of a-Si APS Limitations of a-Si APS Impact of TFT Leakage Stability of APS
Charge gain is a function of gm, which is in turn influenced by the threshold voltage of
AMP TFT ( VTH,AMP ). • Prolonged DC gate bias to AMP causes
VTH,AMP to shift, resulting in degredation of the TFT transconductance • Pixel gain self compensation helps mitigate the stress – voltage drop across READ TFT provides a feedback loop for
degradation in IAMP due to VT,AMP b b b – VTH,AMP IDS,AMP VDS,READ b VDS,AMP IDS,AMP (compensates the current drop) – as a result, the pixel transconductance
(GM) degradation is dampened K. Karim et al., Mat. Res. Soc. Symp. Proc. , vol. 715, p. A4.2.4, 2002 . June 18, 2009 © Carestream Health Inc. — Confidential 37 37 June 18, 2009 © Carestream Health Inc. — Confidential 38 38
Outline LTPS Imaging Array with Peripheral Circuits PMOS 3T Active-Pixel with PMOS Peripheral Circuits
• Market and clinical challenges for digital radiography • Passive pixel amorphous silicon imaging arrays • Active pixel amorphous silicon imaging arrays • Active pixel LTPS imaging arrays • Silicon-on-glass circuits for future active pixel imaging arrays
39 40
LTPS Flat-Panel Imager with Peripheral Circuits Pixel of LTPS Imaging Array with α-Si:H PIN Photodiode PMOS Shift Register 45-micron Pixel with 3-micron Design Rules
α-Si:H PIN Photodiode
Thick dielectric isolation
LTPS TFT Backplane 41 42 Key Challenges for LTPS Imaging Arrays Sources of Leakage in LTPS Transistors Reset TFT Leakage Current Siphons Off Photo-charge TFT Channel Leakage Gate Oxide Leakage at At Grain Boundaries Grain Boundaries
Photocurrent
TFT Leakage Current
IDS (V DS , T) • Generation current at grain Net • Surface topography at grain boundary V boundaries results in TFT leakage DS Charge edges causes gate oxide leakage • Gate-to-drain field enhances leakage • Variable from TFT to TFT current, resulting in exponential increase in leakage with gate voltage, even band-band tunneling • Variable from TFT to TFT 43 44
Key Challenges for LTPS Imaging Arrays Pattern Noise due to non-uniformity 61K electrons pattern noise; matches Monte Carlo simulation of ∆V pattern noise Threshold Voltage Variability T Pixel Amplifier TFT Uncorrected Image Corrected Image
Noise sources in Exposed Frame: Row-to-row " FPN due to VT in V-SR + noise Column-to-column FPN due to "VT in V-SR + noise b b Col-mirror VT variation FPN Pixel-to-pixel FPN Pixel-to-pixel PRNU Pixel + readout electronic noise + kTC + shot + photon shot noise
Pattern + electronic noise: Electronic noise 69,000 rms electron noise 486 rms electron noise " Simulated pattern noise due to VT Simulated electronic noise based on using Monte Carlo method: measured imager gain Current Mirror Column ~ 61,340 rms electron noise ~ 441 rms electron noise Amplifier TFT 45 46
Noise in LTPS Imaging Arrays Outline 350 rms electrons after gain and offset correction
• Without offset and gain correction, fixed pattern noise • Market and clinical challenges for digital radiography caused by TFT threshold and mobility variation is dominant (> • Passive pixel amorphous silicon imaging arrays 60,000 rms electrons) • After offset and gain correction, • Active pixel amorphous silicon imaging arrays fixed pattern noise is reduced below temporal noise • Active pixel LTPS imaging arrays • Temporal noise is dominated by kTC noise of the a-Si PIN • Silicon-on-glass circuits for future active pixel imaging photodiode arrays • Total noise is 300 rms electrons : 10 X lower than comparable a- Si:H passive-pixel imaging arrays for DR • However, any small temperature or operating voltage shift between the dark reference frames and the image can result in significant fixed pattern noise in the difference image 47 48 Comparison of Active-Pixel Backplane Technologies Silicon-on-Glass: Bonding Process
Voltage Si Substrate Si-H Si + H SiOGSiOG 2 p-Si (ELA) p-Si (MICC) Si Substrate LTPS Electron mobility: 50-200 cm 2 / V·s H Uniformity: poor (random grains) p-Si Anodic Bonding Step (SPC) Oxide Electron Mobility Electron Ion Implantation Heat
)c-Si a-Si Clean and Pre-Bond to Glass Separate Si Substrate
TFT performance Thin and Clean Uniformity
Early glass Mature SiOG Stage SiOG Electron mobility: ~500 cm 2 / V·s Uniformity: excellent (single crystal) 49 50
Silicon-on-Glass has Built-In Benefits Fabrication Procedure of SiOG Backplane SiOG
Single Crystal Silicon Glass substrate SiOG island patterning Ion-Free Barrier Layer Ion Accumulation Zone Gate
Corning EAGLE XG ™ Glass Substrate SiO 2 Deposition of Gate metal / SiO 2 Glass substrate SiO 2 layer
B+ B+ Gate
SiO 2
Gate pattern and ion doping Glass substrate
• High mobility, sharp sub-threshold slope and low leakage Source Drain • NMOS: > 450 cm2 / (V·s) Gate • PMOS: > 200 cm2 / (V·s) SiO After Passivation layer (SiN /SiO ) 2 • Uniformity: Excellent (single crystal) for uniform transistor performance X 2 Contact Hole Glass substrate • Built-in barrier layer protects backplane during processing with an ultra- S/D Formation strong bond 51 52
Characteristics of SiOG and LTPS Transistors Comparison of PMOS TFT’s PMOS and NMOS LTPS and SiOG
PMOS NMOS
PMOS ELA SiOG NMOS ELA SiOG V 0.9 V 0.92 V VT -2.2 V -0.7 V T S 0.53 V/dec 0.15 V/dec S 0.42 V/dec 0.27 V/dec
2 2 2 2 )EFF 58.7 cm /Vs 186.4 cm /Vs )EFF 162.4 cm /Vs 264.1 cm /Vs 53 54 Comparison of PMOS TFT’s TFT Characteristics Comparison – Double gate TFT W/L = 4/5+5 LTPS and SiOG Used for row-select and for reset transistor in active pixel arrays
LTPS ELA SiOG 50nm active
55 56
TFT Leakage: Dopuble-gate LTPS and SiOG transistors Comparison of NMOS TFT’s SiOG reset transistor has 100X lower leakage than LTPS LTPS and SiOG
V ~ 5V b SiOG TFT GS SiOG TFTs ELA poly-Si TFTs has 2 orders of magnitude lower leakage
µ S S fe V (V) I (A) µ (cm 2/Vs) V (V) I (A) LTPS (cm 2/Vs) th (mV/dec.) off fe th (mV/dec.) off L = 5 µm+5 µm W = 4 µm 3.4 x 1.2 x Average 205 -0.84 130 64 -2.27 400 10 -14 10 -13
Standard 3.86 0.06 5.6 – 4.38 0.19 80 – deviation
SiOG
57 58
Comparison of SiOG and LTPS Circuits Comparison of SiOG and LTPS Circuits Ring Oscillators 4-Phase PMOS Shift Registers
Start (n-1) CLK 1 CLK 3 23 stage ring oscillator 1 Next " Input 12 fosc 4 / 4+4 um 4/ 4 +4 um 4
T6 T8 Output Silicon-on-Glass: 5 ns delay T2 4 / 4 um 8 ELA Polysilicon: 29.6 ns delay T4 4 / 4 um (n) 10 10 Because of parallel 4 / 4 +4 um < VDD = 10 V > < VDD = 10 V > connected R LOAD fosc = 1.47 MHz f = 8.62 MHz 4 / 4 +4 um 6 osc ELA SiOG VHIGH = 8.61 V VHIGH = 8.56 V V = 6.83 V VDD VHIGH 9.55 V 9.8 V 9 V = 7.38 V 9 LOW LOW 4 V 0.25 V 0.3 V VDD LOW
tRISE 11 )s 2.8 us (V) (V) 8 8 2 tFALL 6 us 1.4 us Output Voltage (V) Output OUT OUT V V 0 Input signal SiOG shift register 7 1 7 t t " " 04.5 ns ELA poly-Si shift register PHL PLH 23 48.62 10 6 Hz 1 -2 t t " " 29 6. ns PHL PLH 23 41.47 10 6 Hz 0.0 0.1 0.2 0.3 0.4 0.5 0.6 CLK3 6 6 CLK1 Time (ms) 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 Time ( s) Time ( s) The response time of SiOG shift register is ~ 4 X faster than ELA poly-Si shift register. The propagation delay of SiOG inverter is ~ 5 X shorter than of ELA poly-Si inverter.59 60 Summary Directions for Radiographic Detector Development • 2-D Projection Radiography
• Robustness, weight Arrays on metal foil or plastic • Cost Fabless model
• Advanced Applications (Dual energy and Volumetric Imaging) Thank You!
• Improved sensitivity Improved passive pixel designs Active-pixel α-Si:H Active-pixel LTPS or SiOG
• Improved resolution Structured phosphors or direct detection Active-pixel LTPS or SiOG
• High frame rate Active-pixel α-Si:H Active-pixel LTPS or SiOG 61
References References (cont)
Amorphous Silicon PIN Photodiodes
Radiographic Systems: • M. Watanabe et. al., Proc. SPIE, 4320, 103 (2001)
• John A. Rowlands and John Yorkston, “Flat Panel Detectors for Digital • Y. Vygranenko, P. Louro, M. Vieira, J. H. Chang, A. Nathan, Low leakage current a-Si:H/a- Radiography”, in Handbook of Medical Imaging, J. Beutel, H. Kundel and R. SiC:H n -i-p photodiode with Cr/a -SiNx front contact, J. Non Cryst. Solids, vol. 352, pp. 1837 - VanMetter (editors), Published by SPIE Press, 2000, ISBN 0819436216, 1840, 2006. 9780819436214 • Y. Vygranenko, R. Kerr, K. Kim, J. H. Chang, D. Striakhilev, A. Nathan, G. Heiler, T. Direct Detection Tredwell, Segmented Amorphous Silicon n-i-p Photodiodes on Stainless-Steel Foils for Flexible Imaging Arrays , MRS Symp. Proc. Vol. 989, 2007 • W. Zhao and J. A. Rowlands, “X-ray imaging using amorphous selenium: Feasibility of a flat panel self-scanned detector for digital radiology,” Med. Phys., vol. 22, no. • K. Kim, Y.Vygranenko, M. Bedzyk, J. H. Chang, T. Chuang, D. Striakhilev, A. Nathan, G. 10, pp. 1595-1604, 1995. Heiler, T. Tredwell, High Performance Hydrogenated Amorphous Silicon n-i-p Photo-diodes on Glass and Plastic Substrates by Low -Temperature Fabrication Process , MRS Symp. • R. A. Street et. al. High Resolution Direct Detection X-Ray Image Sensors, Proc. Proc. Vol. 989, 2007 SPIE, 2000: Real Time Radiography • J. H. Chang, T. Chuang, Y. Vygranenko, D. Striakhilev, K. Kim, A. Nathan, G. Heiler, T. Tredwell, Temperature Dependence of Leakage Current in Segmented a-Si:H n-i-p Photodiodes , MRS Symp. Proc. Vol. 989, 2007
• J. H. Chang, T. Tredwell, G. Heiler, Y. Vygranenko, D. Striakhilev, K. H. Kim, A. Nathan, Physically Based Compact Model for Segmented a-Si:H n-i-p Photodiodes , MRS Symp. Proc. Vol. 1066, 2008 63 64
References (cont) References (cont)
Amorphous Silicon PIN Photodiodes (cont) Passive pixel amorphous silicon image sensors
• K. H. Kim, Y. Vygranenko, D. Striakhilev, M. Bedzyk, J. H. Chang, A. Nathan, T. C. Chuang, • R. A. Street et. al. High Resolution Direct Detection X-Ray Image Sensors, Proc. SPIE, 2000: G. Heiler, T. Tredwell, Performance of a-Si:H n-i-p photodiodes on plastic substrate, J. Non Real Time Radiography Cryst. Solids, vol. 354, pp. 19-25, 2008. • Larry E. Antonuk , John M. Boudry , Youcef El -Mohri , Weidong Huang , Jeffrey H. Siewerdsen , • Y. Vygranenko, E. Fathi, A. Sazonov, M. Vieira, G. Heiler, T. Tredwell, Optimization of p-type and John Yorkston , Large-area flat-panel amorphous silicon imagers, Proc. SPIE, Vol. 2432, Nanocrystalline Silicon Thin Films for Solar Cells and Photodiodes, MRS Symp. Proc. Vol. 216 (1995); 10153, 2009 • R. A. Street, X. D. Wu, R. Weisfield, S. Ready, R. Apte, M. Nguyen, and P. Nylen, “Two Amorphous silicon MIS Photosensors dimensional amorphous silicon image sensor arrays,” in MRS Symp. Proc., vol. 377, 1995, pp. 757-766. • C. Mochizuki, Patent US 6682960B1, Jan 27, 2004 • Weisfield, R.L. , “Amorphous silicon TFT X-ray image sensors”, Technical Digest, International • N. Safavian, Y. Vygranenko, J. H. Chang, K. Kim, J. Lai, D. Striakhilev, A. Nathan, G. Heiler, Electron Devices Meeting, 1998, Page(s):21 - 24 T. Tredwell, M. Fernandes , Modeling and Characterization of the Hydrogenated Amorphous Silicon Metal Insulator Semiconductor Photosensors for Digital Radiography , MRS Symp. • R. Weisfield et. al., “Performance Analysis of a 127-micron pixel large-area TFT/Photodiode Proc. Vol. 989, 2007 Array with Boosted Fill Factor”, Phys of Med Imaging, Proc SPIE, 2004
• M. Fernandes, Y. Vygranenko, M. Vieira, G. Heiler, T. Tredwell, A. Nathan, Transient Current • K. S. Karim, P. Servati, N. Mohan, A. Nathan, and J. A. Rowlands, “VHDL-AMS modeling and in a-Si:H-based MIS Photosensors, MRS Symp. Proc. Vol. 1066, 2008 simulation of a passive pixel sensor in a-Si:H technology for medical imaging,” in Proc. IEEE Int. Symp. Circuits and Systems 2001 Sydney, Australia, vol. 5, May 6\–9, 2001, pp. 479-482. Continuous Photosensors
• M.D. Wright, Patent Application Publication US 2006/0001120 A1, Jan 5, 2006 65 66 References (cont) References (cont)
Passive pixel amorphous silicon image sensors (cont) Passive pixel amorphous silicon image sensors (cont) • R. B. Apte, R. A. Street, S. E. Ready, D. A. Jared, A. M. Moore, R. L. Weisfield, T. A. Rodericks, and T. A. Granberg, “Large area, low-noise amorphous silicon imaging • Y. Vygranenko, J. H. Chang, A. Nathan, “Two-dimensional a-Si:H/a-SiC:H n-i-p sensor system,” Proc. SPIE, vol. 3301, pp. 2 -8, 1998. array with ITO/a -Si:Nx antireflection coating”, MRS Symp. Proc. vol. 862, 2005.
• M. Maolinbay, Y. El-Mohri, L. E. Antonuk, K.-W. Jee, S. Nassif, X. Rong, and Q. Zhao, • Y. Vygranenko, J. H. Chang, A. Nathan, “Two-dimensional a-Si:H n-i-p photodiode array “Additive noise properties of active matrix flat-panel imagers,” Med. Phys., vol. 27, no. for low-level light detection”, IEEE J. Quantum Electron., vol. 41, pp. 697-703, 2005. 8, pp. 1841-1854, Aug. 2000. • J. Lai, Y. Vygranenko, G. Heiler, N. Safavian, D. Striakhilev, A. Nathan, T. Tredwell, • R. Jayakumar, K. S. Karim, S. Sivoththaman, and A. Nathan, “Integration issues for Noise Performance of High Fill Factor Pixel Architectures for Robust Large-Area Image polymeric dielectrics in large area electronics,” in Proc. 23rd Int. Conf. Microelectronics Sensors using Amorphous Silicon Technology , MRS Symp. Proc. Vol. 989, 2007 (MIEL 2002), May 2002, pp. 543-546. • Y. Vygranenko, A. Sazonov, D. Striakhilev, J. H. Chang, G. Heiler, J. Lai, T. Tredwell, A. • J. H. Chang, Y. Vygranenko, A. Nathan, “Two -dimensional a -Si:H based n -i-p sensor Nathan, High Fill Factor a -Si:H Sensor Arrays with Reduced Pixel Crosstalk, MRS Symp. array”, J. Vac. Sci. Technol. A Vac. Surf. Films, vol. 22, pp. 971-974, 2004. Proc. Vol. 1066, 2008
• J. H. Chang, Y. Vygranenko, and A. Nathan, “Two-dimensional sensor array for low- level light detection” Proc. SPIE, vol. 5578, pp. 420-427, 2004.
67 68
References (cont) References (cont)
Active Pixel Amorphous Silicon Image Sensors Active Pixel Amorphous Silicon Image Sensors • K. S. Karim and A. Nathan, “Readout circuit in active pixel sensors in amorphous silicon technology,” IEEE Electron Device Lett., vol. 22, pp. 469-471, Oct. 2001 • K. S. Karim and A. Nathan, “Readout circuit in active pixel sensors in amorphous silicon technology,” IEEE Electron Device Lett., vol. 22, pp. 469-471, Oct. 2001 • H. Tian, B. Fowler, and A. El Gamal, “Analysis of temporal noise in CMOS photodiode active pixel sensor,” IEEE J. Solid-State Circuits, vol. 36, pp. 92-101, Jan. 2001. • H. Tian, B. Fowler, and A. El Gamal, “Analysis of temporal noise in CMOS photodiode active pixel sensor,” IEEE J. Solid-State Circuits, vol. 36, pp. 92-101, Jan. 2001. • Z. Huang and T. Ando, “A novel amplified image sensor with a-Si:H photoconductor and MOS transistors,” IEEE Trans. Electron Devices, vol. 37, pp. 1432-1438, June 1990. • Z. Huang and T. Ando, “A novel amplified image sensor with a-Si:H photoconductor and MOS transistors,” IEEE Trans. Electron Devices, vol. 37, pp. 1432-1438, June 1990. • K. S. Karim, A. Nathan, and J. A. Rowlands, “Active pixel sensor architectures in a-Si:H for medical imaging,” J. Vac. Sci. Technol. A, vol. 20, no. 3, pp. 1095-1099, May 2002. • K. S. Karim, A. Nathan, and J. A. Rowlands, “Active pixel sensor architectures in a-Si:H for • K. S. Karim, A. Nathan, J. A. Rowlands, “Amorphous silicon active pixel sensor readout medical imaging,” J. Vac. Sci. Technol. A, vol. 20, no. 3, pp. 1095-1099, May 2002. circuit architectures for medical imaging”, MRS Symp. Proc., vol 715, pp. 661-666, 2002. • K. S. Karim, A. Nathan, J. A. Rowlands, “Amorphous silicon active pixel sensor readout • K. S. Karim, A. Nathan, and J. A. Rowlands, “Feasibility of current mediated amorphous circuit architectures for medical imaging”, MRS Symp. Proc., vol 715, pp. 661-666, 2002. silicon active pixel sensor readout circuits for large area diagnostic medical imaging,” in Proc. Opto-Canada: SPIE Regional Meeting on Optoelectronics, Photonics and Imaging, vol. • K. S. Karim, A. Nathan, and J. A. Rowlands, “Feasibility of current mediated amorphous TD01, May 2002, pp. 358-360. silicon active pixel sensor readout circuits for large area diagnostic medical imaging,” in Proc. Opto-Canada: SPIE Regional Meeting on Optoelectronics, Photonics and Imaging, vol. • G. Chaji, A. Nathan, Q.A. Pankhurst, “Merged phototransistor pixel with enhanced near infra- TD01, May 2002, pp. 358-360. red response and flicker noise reduction for bio-molecular imaging,” Appl. Phys. Lett., vol. 93 (2008) 203504-1-3 69 70
References (cont) References (cont)
Active Pixel Amorphous Silicon Image Sensors Silicon-on-Glass
• K. S. Karim, A. Nathan, J. A. Rowlands, Amorphous silicon active pixel sensor readout circuit for digital K. P. Gadkaree, K. Soni, S.-C. Cheng, and C. A. Kosik Williams, “Single Crystal Silicon Films on imaging, IEEE Trans. Electron Devices, vol. 50, pp. 200-208, 2003. Glass,” J. Mater. Res., 22 , pp. 2363-2367, 2007. • C. Huang, T. Teng, J. Tsai, and H. Cheng, “The instability mechanisms of hydrogenated amorphous silicon thin film transistors under AC Bias stress,” Jpn. J. Appl. Phys., vol. 39(1), no. 7A, pp. 3867-3871, 2000. J. B. Choi, Y. J. Chang, S. H. Shim, C. W. Kim, and S. E. Ahn, “AMOLED based on Silicon-on- Glass (SiOG) Thin-film Transistors,” SID 07 Technical Digest, pp. 1378-1381, 2007. • N. Mohan, K. S. Karim, and A. Nathan, “Stability issues in digital circuits in amorphous silicon technology,” in Proc. IEEE Canadian Conf. Electrical and Computer Engineering 2001 Toronto, ON, Canada, vol. 1, May C. Kosik Williams, et al , “Demonstration of High Performance TFTs on Silicon-on-Glass (SiOG) 13\–16, 2001, pp. 583-588. Substrate” SID 07 Technical Digest , 38 , pp 287-289, 2007. • X-Ray Detection Using a Two-Transistor Active Pixel Sensor Array Coupled to an a-Se X-Ray Photoconductor, Taghibakhsh, F.; Karim, K.S.; Belev, G.; Kasap, S.O.. Sensors Journal, IEEE D. F. Dawson-Elli, C. A. Kosik Williams, J. G. Couillard, J. S. Cites, R. G. Manley, G. L. Fenger, and K. D. Hirschman “Development of High Performance TFTs on Silicon-on-Glass (SiOG) • Ya-Hsiang Tai,Shih-Che Huang, Ko-Ching Su and Chen-Yeh Tseng, Variation and mismatch effects of the Substrate,” ECS Transactions , 8, pp. 223-228, 2007. low -temperature poly -Si TFTs on the circuit for the X -ray active matrix sensor, Solid State Electronics, 2008 R. G. Manley, G. L. Fenger, P. M. Meller, K. D. Hirschman C. A. Kosik Williams, D. F. Dawson- • F. Taghibakhsh, K. S. Karim, Two-transistor active pixel sensor readout circuits in amorphous silicon Elli, J. G. Couillard, and J. S. Cites, “Development of integrated electronics on silicon-on-glass technology for high-resolution digital imaging applications, IEEE Trans. Electron Devices, vol. 55, pp. 2121- 2128, 2008. (SiOG) substrate,” ECS Transactions , 16 , pp. 371-380, 2008.
• L.E. Antonuk, Y. El-Mohri, M. Koniczek, Q. Zhao, “Active Pixel and Photon Counting Imagers Based on C. Kosik Williams, J. G. Couillard, C. Wang, J. S. Cites, J. H. Cheon, S. H. Park, J. W. Choi, and Poly-Si TFTs”, Proceedings, 2009 SPIE Symposium on Medical Imaging J. Jang, “Plasma Processing in the Fabrication of Silicon-on-Glass (SiOG) Thin-film Transistors,” IDW 08 Proceedings , pp. 1595-1598, 2008.
71 72 References (cont) References (cont)
Silicon-on-Glass (cont)
• J. H. Hyuk, S. H. Park, M. H. Kang, J. Jang, S. E. Ahn, J. S. Cites, C. A. Kosik Williams Silicon-on-Glass (cont) and C. Wang, “Ultrathin Si Thin-film Transistor on Glass,” IEEE Elect. Dev. Lett , 30 , pp. 145-147, 2009. • Y. M. Ha, SID ’00 Digest, 1116 (2000)
• J. W. Choi, J. I. Kim, S. H. Park, J. H. Cheon, S. Saxena, W. K. L, J. Jang, J. Lai, J. H. • S. H. Jung, H. S. Shin, J. H. Lee, and M. K. Han, SID ’05 Digest, 300 (2005) Chang, G. Heiler, T. J. Tredwell, E. J. Mozdy, S. E. Ahn, C. A. Kosik Williams, J. S. Cites, • R G. Manley, G. Fenger, K. D. Hirschman, J. G. Couillard C. Kosik Williams, D. Dawson- and C. Wang, “Low Voltage TFT Circuits Based on SiOG”, 2009 International Thin-Film Elli, and J. Cites, SID’08 Digest, pp. 287 (2008) Transistor Conference, Digest of Technical Papers. • T. Sameshima and S. Usui, “XeCl EXCIMER LASER ANNEALING USED TO FABRICATE • F. Plais, O. Huet, P. Legagneux, D. Pribat, A. J. Auberton-Herve, and T. Barge, “Single POLY-SI TFTS”, Mater. Res. Soc. Symp. Proc. 71, 453 (1986) crystalline silicon thin film transistors fabricated on corning 7059”, Proc. IEEE Int. SOI Conf. 170 (1995). • Robert S. Sposili and James S. lm, Appl. Phys. Lett. 69, 2864 (1996)
• J. Sullivan, H. R. Kirk, A. J. Lamm, S. Kang, P. I. Ong, and F. J. Henley, SID ’06 Digest, • J. G. Couillard, K. P. Gadkaree, and J. F. Mach, US Patent 7176528B2 280 (2006). • M. Okabe, AMLCD’96, pp. 5 (1996) • X. Shi, K. Henttinen, T. Suni, I. Suni, S. S. Lau, and M. Wong, “Characterization of low- temperature processed single-crystalline silicon thin-film transistor on glass”, IEEE Electron Device Lett. 24, 574, (2003).
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