sipm r&d and mems telescope
DESCRIPTION
SiPM R&D and MEMS Telescope. Shinwoo Nam Ewha W. University. SiPM MEMS Telescope Our R&D of SiPM for MEMS Telescope. SiPM. Silicon Photomultiplier (G-APD, MPPC). 42 µm. 1 mm. SiPM. 20 µm. 1 mm. 500 ~ 1000 pixels. Pixels of the SiPM. Each pixel : Independent binary device - PowerPoint PPT PresentationTRANSCRIPT
SiPM R&D and MEMS Telescope
Shinwoo Nam
Ewha W. University
• SiPM
• MEMS Telescope
• Our R&D of SiPM for MEMS Telescope
SiPM
Silicon Photomultiplier (G-APD, MPPC)
Pixels of the SiPM
42 µm20 µm
1 mm
1 mm
500 ~ 1000 pixels
A SiPM output :
Sum of all pixels
Photon counting
Each pixel :
Independent binary device
working in Geiger Mode
with gain of ~ 10^6
SiPM
Single Photon Counting Sensors
Hamamatsu SiPM
Visible LightPhoton CounterOperates at a few Kelvin
Hybrid PhotodiodeOperates with high bias voltage
SiPM Micropixel Structure
• Breakdown Mode Operation of Micro Cells (PN-junction biased in the reverse direction over the breakdown)
• Avalanche region: 0.7~0.8um between p+ and n+ layer with high electric field (3~5)105 V/cm
• Drift region: few micron epitaxy layer on low resistive p substrate.
• Gain ~106 @ ~50 V working bias• Dark rate(~2 MHz) is originated from ther
mally produced charge carriers.• Electrical decoupling of the pixels by resi
stive strips.• Common Al strips for readout.
Uniformity of the electric field
Silicon Photomultiplier
• Detection efficiency ~25%-60%• Single photon performance (Intrinsic Gain ~106),• Proportional mode for the photon flux
(Dynamic range depends on the number of micropixels 500 ~ 3000),• Fast Time response (rising time ~30 ps), • Operation conditions:
– Low Operational Voltage ~50-60 V,– Room Temperature,– Non Sensitive to Magnetic Field,– Minimum Required Electronics,
• Miniature size and possibility to combine in matrix.• Low cost ( in mass production conditions)
Detection Efficiency
• Quantum Efficiency of Micropixel– wavelength and optical absorption func
tion dependent– UV region of Light is limited by present
technology topology (dead layer on the top),
– IR region of Light is limited by thickness of sensitive layer
• Geometry Efficiency – the technology topology gives the limit
ation of the sensitive area • Breakdown Mode is statistical process
– probability that a photoelectron triggers an avalanche process in Si
The Depletion Area is ~5 m: Low Resistive Si, Low Biase Voltage
SiPM signal
• Signal of Silicon Photomultiplier with preamplifier (Gain 20)
Signal of Silicon Photomultiplier can be readout without Frontend Electronics
LED Signal
Dark rate signal
LED Signal
From V. Saveliev
Silicon Photomultiplier in Magnetic Field
• Silicon Photomultiplier in Strong Magnetic Field
Test of SiPM in Strong Magnetic Field up to 4 Tesla (Amplitude of SiPM signal in magnetic field with different orientations) (V. Saveliev, CALICE Meeting, DESY, 30.01.2004)
Silicon Photomultiplier Noise
• Dark Count Rate – Probability that bulk thermal electrons trigger an avalanche process
(Voltage Dependent) - characterized by frequency– Bias Voltage, Temperature
• The noise signal amplitude – is amplitude of single photoelectron– For the measurement of Photons Flux on the level more than ~ 4-5
photoelectrons this dark current factor can be ignored.
Hamamatsu
Silicon Photomultiplier Crosstalk
• Optic Crosstalk– During avalanche breakdown t
he micropixel emits photons. These photons should not reach nearby cells because this would initiate breakdowns there. – Optical Crosstalk.
Spectrum of Photons emitted during
the Avalanche process in Si
Hamamatsu ->
Silicon Photomultiplier Applications : HEP
• DESY International LInear Collider Group, in particularly Scintillator Tile Hadron Calorimeter Activity
Silicon photomultiplier readout of Scintillator Tile with WLS
Silicon Photomultiplier Applications : Medical Instrument
• Positron Emission Tomography
Silicon Photomultiplier is most promising Photodetector for the Modern Scintillator Material and Medical Imaging Systems
Spectrums of 22Na (511 keV) with LSO
Silicon Photomultiplier Applications : Space
• SiPM in space
Silicon Photomultiplier is most promising Photodetector for the space applicatioin
MEMS Telescope
Cosmic Ray Flux
4
그림지구에서 관측된고에너지입자의에너지에따른분포그림의축에 을곱한결과이다
Extensive Air Shower (EAS)
• Initiated by Hadronic int. of Primary with Air Molecules 1. collimated hadronic core (charged pions source of muons)2. EM subshowers along the axis from pi^0 decays (90% of shower) • ~1010 particles at Ground from 1019 eV primary CR
• Shower Detection - Fluorescence UV photons - Particles (muon,e+,e-,photon) - Cerenkov Radiation
Pierre Auger 1930s
Principle of EUSO :Use whole atmosphere as a detector
TPC-likenaturalchamber1020 eV
Image of Air-shower on Focal Surface
50 events of 1020eV proton showers are superimposed on the EUSO focal surface with 192 k pixels.
x-t view y-t view
4
simulation
X
Y
time(sec)
phot
oele
ctro
ns
Proton E=1020eV, =60º GTU = 2.5 sec
The Focal Surface : PMT -> SiPM
(164PDMs = 0.2M pixels)
2.26 m max
MAPMT(6x6 pixels)
26.2
mm
5900 PMTs on the focal surface!A pixel side = 0.77 km on ground
Idea of MEMS Tracking Mirror Telescope
•Archimedes Mirror : Mirror segments by soldiers•Proposed Mirror : Mirrormirror segments by VLSI
Aberration free focusing, Wide FOV,Fast Tracking capability
VLSI 칩 마이크로미러
광검출기
이동체Air Shower
MicromirrorsControl Circuit
Photodetector
What is MEMS Mirror ?• MEMS (MicroElectroMechanical Systems)
• Recent technological advance in silicon industry
• Originally developed for optical communication & display industry
• Cost effectiveness due to standard silicon fab available
• 100x100 m2 in size or less • Each cell controlled independently
• Types• DMD : Digital, electrostatic actuator, TI• Others (Piezoelectric, thermal, membrane,
…)
Earth
UHECR(1020 eV) fluorescence
Cerenkov
Trigger Detector (poor resolution, wide FOV, PMTs)
Zoom-in Detector (high resolution, narrow FOV, MAPMTs)
MEMS Tracking Mirror Telescope
Concept of MEMSTEL (MEMS Space Telescope)
•MEMS compound mirror reflector•Perfect focusing & Tracking
capability•Small number of
detector/electronics channels
~ 1m x 1m Mirror Array
Size of mirror array: 3 mm x 3 mm
Tilted comb actuator(mirror plate removed)
Torsion spring
Mirror plate
Addressing line (back side view)
Mirror plate and actuator bonding
Mirror plate
8 x 8 mirror mask layout
Fabricated 2-axis Silicon Analog Micromirror (Ewha)
지상으로 치는 일반 번개
Ewha University, Seoul National University, Moscow State University
전리층 (ionosphere)
성층권 (stratosphere)
극한 대기현상의 메가번개
탑재체 : MTEL (MEMS Telescope for Extreme Lightning), 3x3 mm2 aperture
MTEL (Pathfinder)Russian Microsatellite Tatyana-2 (2008.7 발사 )
Extremely Large Transient Sparks
주탑재체
Concept of Zoom & Tracking of KAMTELConcept of Zoom & Tracking of KAMTEL
Detector image
Detector
MEMS mirrorArray
Electronics
Hole
Trigger Zoom
Trigger Mirror : 1-axis on/offZoom Mirror : 2-axis analog tilting
Trigger mirror
Zoom mirror
IR camera
Detector
Spectrophotometer Zoom mirrorTrigger mirror
Electronics box(Analog, Digital, MEMS driver)
Detector (MAPMT)
IR camera
aperture
한국우주인임무를 위한 극소형 MEMS 우주망원경
Design, Simulation of SiPMfor MEMS Telescope
Conduct: Al Resistor: Poly-Si(1MΩ)
P+
N+
SiO2
Epitaxy layer: boron dopingTrench:fill Polyimide
Contact: Al
• Each micropixel is isolated by trench • Resister is formed by Poly silicon.• P+ region of pn junction is a small size than n+ region to reduce le
akage current.
Design for SiPM - Cross section
Design of a Micropixel and the connection
<Trench><Trench><N+ implant><N+ implant>
<Resistor><Resistor> <Contact><Contact> <metal><metal>
<P+ implant><P+ implant>
<Polyimide><Polyimide>
Design for SiPM - Mask(7 layers)
32×32
16×16
8×
82×
2
4×
4
Design area
4" wafer4" wafer
Design for SiPM- maskDesign for SiPM- mask
Design for SiPM - Geometrical EfficiencyDesign for SiPM - Geometrical Efficiency
• Cell area : 32ⅹ35=1120um
• Sensitive area : 632um
–Metal : 8*8+32*3 = 160–Resistor : 3*21+5.5*3+26*3-2*6.5 =
144.5–Trench : 32*3+29*3 = 183–Total non-sensitive area : 487.5
•Geometrical efficiency(%)
= 632.5/1120 *100
= 56.5%
29
32
23
26
3
3
21
3
8
8
4
Unit : um
Vertical Profile for SIPM
Depletion Depth
Simulation StudySimulation Study
Electric Field
Simulation of OperationSimulation of Operation
Photon Detection EfficiencyIV Characteristics
Our first attempt of SiPM fabricationOur first attempt of SiPM fabrication
SiPM wafer in the final process
Photo Mask
Fabrication 55 Steps
Wafer condition
1. Si Substrate * Type/Dopant: P(bor) * Thickness: ~550um * Resistivity: 5ohm.cm 2. Epitaxy * Type/Dopant: P(bor) * Thickness: 5um ± 5% * Resistivity: 1~ 5ohm.cm