CMOS photodetectors - ChipScope · CMOS Sensors Funded by the European Union - GA 737089 Kick-Off...
Transcript of CMOS photodetectors - ChipScope · CMOS Sensors Funded by the European Union - GA 737089 Kick-Off...
-
Kick-Off Interdisciplinary Workshop
CMOS photodetectors
Angel Dieguez, [email protected], University of Barcelona
Funded by the European Union - GA 737089 1Kick-Off Meeting, Barcelona, Jan 17-18, 2017
mailto:[email protected]
-
Outline
Funded by the European Union - GA 737089 2Kick-Off Meeting, Barcelona, Jan 17-18, 2017
1-IntroductionPhotodetectionRequirements on photodetectorsCMOS sensors
2-The photodiodeCMOS processThe pn juntion as photodiodeHigh efficiency light detectors
3-Avalanche photodiodesAvalanche photodiodesImplementation avalanche photodiodes in CMOSMain figures of merit: PDE, dark count noise, afterpulsing noiseReadout circuits
4-ApplicationsLifetime fluorescence measurementsChipscope
-
Photodetection
Funded by the European Union - GA 737089 3Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Purpose:
Convert light into detectable electronic signal
Principle:
Use photoelectric effect to ‘convert’ photons (γ) to photoelectrons (pe)
A. Einstein. Annalen der Physik 17 (1905) 132–148.
Absorbed γ’s impart energy to electrons (e-) in the material; If Eγ =hν> Eg, electrons are lifted to conductance band. In a Si-photodiode, these electrons can create a photocurrent.
Eγ =hν=hc/λ
-
Photodetection
Funded by the European Union - GA 737089 4Kick-Off Meeting, Barcelona, Jan 17-18, 2017
100 250 400 550 700 850 λ [nm]
12.3 4.9 3.1 2.24 1.76 1.45 E [eV]
VisibleUltra Violet (UV)
Infra Red(IR)
Remember : E[eV] ≅ 1239/λ[nm]
NaF
, MgF
2, Li
F, Ca
F 2
Silicon(1100 nm)
norm
al
win
dow
gla
ss
boro
silic
ate
glas
s
quar
tz
Cut-off limits of window materials
-
Photodetection
Funded by the European Union - GA 737089 5Kick-Off Meeting, Barcelona, Jan 17-18, 2017
(http://pdg.ge.infn.it/~) deg/ccd.html
α=103cm-1, means an 1/e optical power absorption length of 1/α=10-3cm=10μm
-
Requirements on photodetectors
Funded by the European Union - GA 737089 6Kick-Off Meeting, Barcelona, Jan 17-18, 2017
High sensitivity, usually expressed asquantum efficiency
or radiant sensitivity or responsivity S (mA/W)
Good linearity: Output signal ∼ light intensity, over a large dynamic range
Fast time response: most photodiodes have a collection time of µs
( )γN
NQE pe=%
( ) ( ))(
/124%nm
WmASQEλ
⋅≈
Low intrinsic noise. A noise-free detector doesn’t exist. Thermally created photoelectrons represent the lower limit for the noise rate ∼ AoT2exp(-eWph/kT). + many more (size, fill factor, radiation hardness, cost, tolerance/immunity to B-fields…)
-
CMOS Sensors
Funded by the European Union - GA 737089 7Kick-Off Meeting, Barcelona, Jan 17-18, 2017
The 1st generation of image sensors used charge coupled device (CCD) technology.
CCD inventors were granted the 2009 Nobel Prize in Physics.
CCDs dominated the market for 3 decades thanks to:
high resolution; low noise.
Willard Boyle and George Smith invented CCDs in 1969.
Photo: Alcatel-Lucent/Bell Labs, 1974.
-
CMOS Sensors
Funded by the European Union - GA 737089 8Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Eric Fossum invented the CMOS APS in 1994.
Photo: Amy Etra/BusinessWeek, 2011.
2nd generation image sensors used CMOS active pixel sensor (APS) technology.
It was developed at NASA’s Jet Propulsion Laboratory.
Dominated low-power imaging thanks to: On-chip integration with CMOS
devices; Simple supply system.
-
CMOS Sensors
Funded by the European Union - GA 737089 9Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Humans on earth: 7.500M
-
Funded by the European Union - GA 737089 10Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Photodetection basics
-
Funded by the European Union - GA 737089 11Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Photodetection basics
-
Photodetection basics
Funded by the European Union - GA 737089 12Kick-Off Meeting, Barcelona, Jan 17-18, 2017
- PN junction in reverse bias
- Generated carriers are removed by built-in field in depletion region.
- Very small current (reverse current)
- Photo-generated carriers drift into P (holes) and N (electrons) regions creating currents.
- One photon creates one electron and hole
-
High-efficiency detectors
Funded by the European Union - GA 737089 13Kick-Off Meeting, Barcelona, Jan 17-18, 2017
PIN photodiode
Avalanche photodiode
-
Avalanche photodiodes
Funded by the European Union - GA 737089 14Kick-Off Meeting, Barcelona, Jan 17-18, 2017
• Drifting electrons generated within the near intrinsic region drift diffuse into the p-region.
• The large E fields provide enough kinetic energy to impact-ionize some of the Si covalent bonds and release more EHPs.
• Secondary e-h are accelerated by the same high fields, ionize and generate even more EHPs
• This effect leads to an avalanche of impact ionization processes and the photodiode can be said to possess and internal gain mechanism
-
Avalanche photodiodes
Funded by the European Union - GA 737089 15Kick-Off Meeting, Barcelona, Jan 17-18, 2017
A. Arbat, PhD, Towards a forward tracker detector based on Geiger mode avalanche photodiodesfor future linear colliders, 2010.
-
Implementation of avalanche photodiodes
Funded by the European Union - GA 737089 16Kick-Off Meeting, Barcelona, Jan 17-18, 2017
R.Haitz, J.Appl.Phys. 35, 1370 (1964), J.Appl.Phys. 36, 3123 (1965)
-
Implementation of avalanche photodiodes
Funded by the European Union - GA 737089 17Kick-Off Meeting, Barcelona, Jan 17-18, 2017
-
Main figure of merit. PDE
Funded by the European Union - GA 737089 18Kick-Off Meeting, Barcelona, Jan 17-18, 2017
• PDE depends of overvoltageOV↑, PDE ↑
• PDE depends on the technological processDeeper junction, more infraredShallower junction, more ultraviolet
-
Main figure of merit. PDE
Funded by the European Union - GA 737089 19Kick-Off Meeting, Barcelona, Jan 17-18, 2017
-
Main figures of merit. Noise
Funded by the European Union - GA 737089 20Kick-Off Meeting, Barcelona, Jan 17-18, 2017
1. Dark counts (uncorrelated noise)
(a) Thermal generation (SRH)(b) Trap assisted thermal/SRH generation(c) Band-to-band tunneling(d) Trap assisted tunneling- Measured as dark counts/s (Dark Count Rate)- Dependent on - fabrication process (traps)
- sensor surface (area)- reverse bias overvoltage (VOV)- working T
- Reduced by - area ↓, VOV ↓, T ↓
2. Afterpulses (correlated noise)
(e) e– (left) and h+ (hole) afterpulses- Dependent on - trapping centers
- number of charge carriers- Reduced by - CP (parasitic capacitance) ↓
- active quenching- dead time ↑
Primary carriertriggers avalanche
(due to absorbedradiation or other
phenomena →noise)
Sources of noise counts in GAPDs:
1.12 eV
e–
h+trap
3. Crosstalk (correlated noise)
(f) Electrical crosstalk- Dependent on - pixel separation- Suppressed by - using different wells
(g) Optical crosstalk- Dependent on - pixel separation- Reduced by - limiting Geiger current
- using trenches
(f)
(g)
primaryavalanche
n-well
drift
diffusion
new avalanche
𝐄𝐄 ↑
recombinationphotons emitted due
to electroluminiscence
new avalanche
-
Funded by the European Union - GA 737089 21Kick-Off Meeting, Barcelona, Jan 17-18, 2017
• DC are due to thermally generated carriers
• Moderate DCR without STI 1 Hz/µm2 < DCR < 102 Hz/µm2
• High DCR with STIDCR ≈ 1 MHz
• Depends on process and overvoltage and area
Eva Vilella, Feasibility of Geiger-mode avalanche photodiodes in CMOS standard technologies for tracker detectors, PhD 2013.
Main figures of merit. Noise
-
Gating of avalanche photodiodes
Funded by the European Union - GA 737089 22Kick-Off Meeting, Barcelona, Jan 17-18, 2017
E. Vilella et al., A low-noise time-gated single-photon detector in a HV-CMOS technology for triggered imaging , Sensors &Actuators A 201, 2013.
• Valid for those applications where the signal time arrival can be known in advance (time-gated FLIM)• The sensor is periodically activated and deactivated under the command of a trigger signal
-
Noise, Advantages of time-gated operation (2)
tOFF = 80ns
tOFF = 300ns
E. Vilella et al., DTIP 2013
•Afterpulses are caused by carriers trapped during the avalanche discharging and then released triggering a new avalanche
• Afterpulses depend on the process
• Can be eliminated with non-active periods (tOFF)
The image is for a 0.35um process
23/35
-
Funded by the European Union - GA 737089 24Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Passive quenching and recharge
- Quenching → lower Vbias=VBD after an avalanche- Resistive element in series with the sensor- Resistor with 102 kΩ (area ↑) or MOS
transistor with proper (W/L) and bias- τQ=(CD+CP)·RD
Readout circuit:- CMOS inverter- Voltage comparator- Source follower
Readout circuits
- Recharge → increase Vbias>VBD after quenching- Quenching element is used for recharge too- τR=(CD+CP)·RQ- Poor control over quenching and recharge times- RQ ↑, τQ ↓, τR ↑ (and vice versa)
-
Funded by the European Union - GA 737089 25Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Random access,full camera readout
C. Niclass et al. 2005 “A single photon detector array with 64x64 resolution and millimetric depth accuracy for 3D imaging”
Event driven readout,few pixels read
C. Niclass et al. 2007 “A CMOS 64x48 single photon avalanche diode array with event-driven readout”
Pipelined readout
M. Sergio et al. 2007 “A 128x2 CMOS single photon streak camera with timing-preserving latchless pipeline readout”
In-pixel storing, full camera readout
F. Guerrieri et al. 2008 “Fast single-photon imager acquires 1024 pixels at 100 kframe/s”
Parallel readout, full camera readout
C. Niclass et al. 2008 “A 128x128 single-photon imager with on-chip column-level 10b time-to-digital converter array capable of 97ps resolution”
M. Gersbach et al. 2009 “A parallel 32x32 time-to-digital converter array fabricated in a 130nm imaging CMOS technology”
-
Application. Fluorescence lifetime.
Funded by the European Union - GA 737089 26Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Channel edge
-
CMOS photodetectors in ChipScope
Funded by the European Union - GA 737089 27Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Lateral resolution:
Axial resolution:
-
CMOS photodetectors in ChipScope
Funded by the European Union - GA 737089 28Kick-Off Meeting, Barcelona, Jan 17-18, 2017
ChipScope concept
The technology is based on a disruptive approach that consist in obtaining the high resolution using spatially resolved
illuminator. It is a long term vision to create an inexpensive technology.
Expertise from different scientific areas: physics, material science, computer science, biology.
Near-Field Scanning Optical Microscopy (NSOM, SNOM)
Photo-Activated Localization Microscopy (PALM)
Stochastic Optical Reconstruction Microscopy (STORM)
STimulated Emission Depletion (STED)
Scanning Electron Microscopy (SEM)
Transmission Electron Microscopy (TEM)
Scanning Probe Microscopy (SPM)
• LEDs of nanometric size are turn on and off• Photodetector measures light
- Single photon detection- Sub-ns time response
• Pulses of light are counted for each LED• Images are formed by considering all LEDs
-
Thank you for your attention!
Funded by the European Union - GA 737089 29Kick-Off Meeting, Barcelona, Jan 17-18, 2017
Número de diapositiva 1OutlinePhotodetectionPhotodetectionPhotodetectionRequirements on photodetectorsCMOS SensorsCMOS SensorsCMOS SensorsPhotodetection basicsPhotodetection basicsPhotodetection basicsHigh-efficiency detectorsAvalanche photodiodesAvalanche photodiodesImplementation of avalanche photodiodesImplementation of avalanche photodiodesMain figure of merit. PDEMain figure of merit. PDEMain figures of merit. NoiseMain figures of merit. NoiseGating of avalanche photodiodesNúmero de diapositiva 23Readout circuitsNúmero de diapositiva 25Application. Fluorescence lifetime.CMOS photodetectors in ChipScopeCMOS photodetectors in ChipScopeNúmero de diapositiva 29