Backside Illuminated Drift Backside Illuminated Drift Silicon - - PowerPoint PPT Presentation

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Backside Illuminated Drift Backside Illuminated Drift Silicon - - PowerPoint PPT Presentation

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Backside Illuminated Drift Backside Illuminated Drift Silicon Photomultiplier Silicon Photomultiplier BID- -SiPM SiPM BID Jelena Ninkovic Ninkovic Jelena on behalf of the BID SiPM group* group* on behalf of the BID- -SiPM *MPI for

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SLIDE 1

Backside Illuminated Drift Backside Illuminated Drift Silicon Photomultiplier Silicon Photomultiplier BID BID-

  • SiPM

SiPM

Jelena Jelena Ninkovic Ninkovic

  • n behalf of the
  • n behalf of the BID

BID-

  • SiPM

SiPM group* group*

*MPI for Physics: J. Ninković, C. Merck, R. Mirzoyan, R. Richter, H.G. Moser, A. Otte, M. Teshima, G. Valceanu *PNSensor: R. Eckhart, G. Lutz, R. Hartmann, P. Holl, C. Koitsch and H. Soltau.

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SLIDE 2

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 2 2

Outline Outline

  • Motivation

Motivation

  • Concept of the BID

Concept of the BID-

  • SiPM

SiPM

  • First measurements of the test structures

First measurements of the test structures

  • Future plans

Future plans

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SLIDE 3

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 3 3

Gamma Ray Astronomy Gamma Ray Astronomy

Gamma Ray induces electromagnetic cascade relativistic particle shower in atmosphere Cherenkov light fast light flash (nanoseconds) 100 photons per m² (1 TeV Gamma Ray) MAGIC: world largest air Cherenkov telescope

http://wwwmagic.mppmu.mpg.de/

30° 400 km

≈ ≈ ≈

Čerenkov Fluorescence EECR 230 km Earth Atmosphere

M .C .M . ‘02

30° 400 km

≈ ≈ ≈

Čerenkov Fluorescence EECR 230 km Earth Atmosphere

M .C .M . ‘02

Fluorescence in the atmosphere

JEM - EUSO

High QE photo sensors!!!

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SLIDE 4

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 4 4

SiPM SiPM

Si Conventional SiPM - an array of avalanche photo diodes operated in Geiger mode photon avalanche regions

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SLIDE 5

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 5 5

Si

BID BID-

  • SiPM

SiPM

Conventional SiPM - an array of avalanche photo diodes operated in Geiger mode photon avalanche regions Si photon depleted bulk avalanche regions path of the photo electron

  • utput

50µm … 450µm

BID SiPM – combined principle of avalanche photodiode and drift diode

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SLIDE 6

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 6 6

BID BID-

  • SiPM

SiPM

drift rings p+ shallow p+ avalanche region photon drift path of the photo electron

µm 100

µm µm 450 ... 50

quenching resistor

  • utput line

deep n

n type depleted bulk n+

deep p+

Zoom to a single cell

Modulated avalanche region

  • G. Lutz et al., IEEE Trans.Nuc. Sci., 52, (2005) 1156-1159.
  • G. Lutz et al., Proc.Int. Con. New Dev. Photodet., Beaune 2005, to be published in NIM A.
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SLIDE 7

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 7 7

Pro & Con Pro & Con

Advantages: Advantages:

  • Unstructured thin entrance window

Unstructured thin entrance window

  • 100% fill factor

100% fill factor

  • High conversion efficiency (especially at short wavelength)

High conversion efficiency (especially at short wavelength)

  • Lateral drift field focuses electrons into high field region

Lateral drift field focuses electrons into high field region

  • High Geiger efficiency (always electrons trigger breakdown)

High Geiger efficiency (always electrons trigger breakdown)

  • Small diode capacitance (short recovery, reduced x

Small diode capacitance (short recovery, reduced x-

  • talk)

talk)

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SLIDE 8

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 8 8

BID BID-

  • SiPM radiation entrance window

SiPM radiation entrance window

Non-structured backside allows engineering of the radiation entrance window

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SLIDE 9

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 9 9

Geiger Efficiency of electrons and holes Geiger Efficiency of electrons and holes

Avalanche Efficiency (1 μm high field region) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 250000 350000 450000 550000 650000 750000 Field (V/cm) Efficiency Electrons Holes

Electrons have a higher probability to trigger an avalanche breakdown then holes Efficiency depends on depth of photon conversion and hence

  • n the wavelength

Solutions:

  • Increase overvoltage

Or:

  • Ensure that only electrons trigger an

avalanche

holes p-substrate p- epi p+ n+ el. n-substrate n- epi n+ p+ el. holes

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SLIDE 10

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 10 10

Sensitivity at different wavelengths Sensitivity at different wavelengths

light absorption in Silicon 0.001 0.01 0.1 1 10 100 1000 10000 250 450 650 850 1050 Wavelength (nm) Absorption length (μm)

Thin entrance window needed

holes electrons

Holes trigger avalanche Electrons trigger avalanche

p-substrate: photons < 450 nm: only holes contribute photons > 700 nm: lost in insensitive bulk n-substrate:

  • k for short wavelengths,

hole efficiency dominates for λ > 500 nm Back illumination: whole thick (> 50 μm) bulk absorbs photons design for electron collection

Example: p-substrate

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SLIDE 11

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 11 11

Pro & Con Pro & Con

Advantages: Advantages:

  • Unstructured thin entrance window

Unstructured thin entrance window

  • 100% fill factor

100% fill factor

  • High conversion efficiency (especially at short wavelength)

High conversion efficiency (especially at short wavelength)

  • Lateral drift field focuses electrons into high field region

Lateral drift field focuses electrons into high field region

  • High Geiger efficiency (always electrons trigger breakdown)

High Geiger efficiency (always electrons trigger breakdown)

  • Small diode capacitance (short recovery, reduced x

Small diode capacitance (short recovery, reduced x-

  • talk)

talk)

Disadvantages: Disadvantages:

  • Large volume for thermal generated currents (

Large volume for thermal generated currents ( increased dark rate) increased dark rate)

  • M

Maintain low leakage currents aintain low leakage currents

  • Cooling

Cooling

  • Thinning ( < 50

Thinning ( < 50 μ μm instead of 450 m instead of 450 μ μm) m)

  • Large volume for internal photon conversion (

Large volume for internal photon conversion ( increases x increases x-

  • talk)

talk)

  • Lower gain (small diode capacitance helps)

Lower gain (small diode capacitance helps)

  • Thinning ( < 50

Thinning ( < 50 μ μm instead of 450 m instead of 450 μ μm) m)

Possible show stopper! Possible show stopper!

  • Electron drift increases time jitter

Electron drift increases time jitter

  • Small pixels,

Small pixels,

  • Increased mobility at low temperature <2 ns possible

Increased mobility at low temperature <2 ns possible

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SLIDE 12

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 12 12

Design of Devices Design of Devices

Hexagonal Cells 100-200 μm diameter 3 drift rings Central HF region with 8 μm diameter Capacitance ~ 12 fF Gain: O(105) ~ 1 μm depth 95% Geiger efficiency @ 8V overvoltage (electrons) Drift field extends into bulk

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SLIDE 13

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 13 13

Test structure production in 2005/06 Test structure production in 2005/06

  • > fix parameters of avalanche cell (radius, depth, resistor values…)
  • > no backside illumination yet

Single pixel structures Small arrays Large arrays (20 x 25 pixel 180 μm pitch) HF diameter: 5-25 μm Successfully tested

18,850 18,855 18,860 18,865 18,870 18,875 18,880 18,885 18,890 18,895 18,900 18,905 1000 2000 3000 4000 5000 6000 1,885 1,890 1,895 1,900 1,905 1,910 1,915 1,920 1,925 1,930 1,935 1,940 Y Axis [μm] Y Axis [m m ] Coincidence X Axis [mm] 460,0 1135 1810 2485 3160 3835 4510 5185 5860
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SLIDE 14

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 14 14

Test structures Test structures

Breakdown voltage were expected from simulations

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SLIDE 15

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 15 15

Test structures Test structures

  • Homogeneity

Homogeneity

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SLIDE 16

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 16 16

Test structures Test structures

  • Stress conditioning

Stress conditioning

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SLIDE 17

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 17 17

Constant area: 1mm² Different circumferences: 4mm (6x) 5mm (3x) 8.5mm (3x) 16.25mm (2x) Ibulk = 0.69 pA / mm2@RT

Separation of centre and edge currents Separation of centre and edge currents

Test structures Test structures

Measurement of many diodes with same area but different circumference allows separation of the bulk leakage current I@0mm Ibulk

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SLIDE 18

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 18 18

Results: Test Structures Results: Test Structures

Low Medium High

Results with light pulses from a laser (< 1 ns): Photoelectron peaks clearly resolved up to large n(photon) RMS of single photoelectron signal ~ 5%

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SLIDE 19

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 19 19

Results: Test Structures Results: Test Structures

T = 0oC T = 10oC T = 20oC

Gain proportional to overvoltage Breakdown voltage in good agreement with device simulations

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SLIDE 20

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 20 20

Test Structures Test Structures

Dark rate mainly from highly doped HF region: For a 5 x 5 mm2 matrix with 500 pixels: ~0.2 MHz @ 20oC (8V)

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SLIDE 21

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 21 21

Leakage Currents and Dark Rates Leakage Currents and Dark Rates

Back side illuminated: bulk leakage current dominates: For devices thinned to 50 μm: ~10MHz @ 20oC Cooling needed: ~ 1 MHz @ 0oC

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SLIDE 22

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 22 22

Cross Talk Studies Cross Talk Studies

Dark spectrum of 25 μm arrays x-talk heavily suppressed due to small HF region and large pitch Background due to pile up (suppressed by cooling to -20 C) 2pe signal clearly visible: Probability for x-talk ~ 10-4 (@*V ΔU) For backside illumination: Bulk is sensitive to cross-talk photons Use MC to extrapolated to full structure 1 pe ~ 2x106 2 pe < 200

V entries

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SLIDE 23

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 23 23

Results Results

Cross talk measured with test structures implies: ~54 photons (E>1.14 eV) per avalanche (@*V ΔU) For a backside illuminated device with 100 μm pitch: cross-talk probability: 99.99% Due to large capacitance (47 fF of HF region + coupling capacitances), the gain is very high: ~4 x 106 Scaling to the expected gain of 105: Cross talk 20-30 % Still high but could be manageable Extrapolation has large systematic error!

Total capacitance

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SLIDE 24

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 24 24 Top Wafer

a) oxidation and back side implant of top wafer b) wafer bonding and grinding/polishing of top wafer c) process passivation

  • pen backside passivation

d) deep etching opens "windows" in handle wafer

Processing of thin detectors (50 Processing of thin detectors (50 μ μm) m)

Successfully tested with MOS diodes (keep low leakage current ~ 100 pA/cm2)

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SLIDE 25

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 25 25

Next steps Next steps … …

production of fully functional backside illuminated drift SiPMs:

  • > including drift rings
  • > double sided processing,

deplete bulk Finished: End 2007 Various test structures (single pixels, small arrays) Arrays: 30 x 31 pixel Diameter HF region: < 8 μm Pitch: 100, 120, 150, 200 μm Area: 3x3 mm2 – 6x6 mm2 In addition: some front illuminated arrays

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SLIDE 26

Jelena Jelena Ninkovic Ninkovic Light 07, Light 07, Ringberg Ringberg Castle Castle, Tegernsee, 23 , Tegernsee, 23-

  • 27 September 2007

27 September 2007 26 26

Thanks Thanks