Transcript Diapositive 1

3D micro-structuring of diamond for radiation
detector applications
B.Caylar, M.Pomorski, P.Bergonzo
Diamond Sensors Laboratory CEA-LIST, Gif-Sur-Yvette, France
José Alvarez
Laboratoire de génie électrique de Paris (LGEP), Gif-sur-Yvette, France
Alexander Oh
University of Manchester, School of Physics and Astronomy, Manchester, United Kingdom
Thorsten Wengler
CERN, Geneva, Switzerland
Diamond Sensors Laboratory
Context – Why using 3D electrodes?
Ionizing particle
2D
3D
Electrodes
 Advantages1:
 Higher electric field for a given applied bias voltage
 Shorter drift path thus drift time
 Lower probability of trapping
[1] J.Morse, C.J. Kenney, E.M. Westbrook et al. / Nuclear Instruments and Methods in Physics Research Section A,
524 (2004) 236.
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Context – Why using 3D electrodes?

1.5x10
Planar
 3D
-5
1.5x10
-5
1.2x10
-5
9.0x10
-6
6.0x10
-6
3.0x10
-6
 = 250ns
 = 2ns
Perfect Cristal
Current (A)
Current (A)
Perfect cristal
0.0
1.2x10
-5
9.0x10
-6
6.0x10
-6
3.0x10
-6
 = 250ns
 = 2ns
0.0
0
2
4
Time (ns)
6
8
0
2
4
6
8
Time (ns)
 Analytically calculated currents generated by a MIP
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Context – Why using 3D electrodes?
NIEL induces bulk defects

Normalized counts
[2] Michal Pomorski – PhD debate, Frankfurt University 07/08/2008
Signal decrease
before irradiation
after 1.2 x 1014 20MeV n.cm-2
after 1.97 x 1014 20MeV n.cm-2
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 When flux increases :
0
0
5
10
15
20
Collected charge [ke]
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 Defects number increases
 Carrier lifetime reduction
 CCE decreases
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Context – Why using 3D electrodes?
 3D
Collected charge (fC)
3.0
99.6%
2.5
2.0
1.5
47%
1.0
Perfect cristal
 = 250ns
 = 2ns
0.5
0.0
0
2
4
Time (ns)
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Collected charge (fC)
 Planar
3.0
99.99%
2.5
95%
2.0
1.5
1.0
Perfect cristal
0.5
 = 250ns
 = 2ns
0.0
8
0
2
4
6
8
Time (ns)
 3D geometry is faster : 8ns vs 208ps.
 3D geometry makes the detector more radiation hard
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Outline
•
Burried electrodes
 Laser setup & Fabrication
 Structural characterization
 Electrical characterization
•
pc-CVD Detector (e6 detector grade)
 Electrical characterization
 Characterization under alpha particles
•
sc-CVD Detector (e6 electronic grade)
 Optical characterization
 Electrical characterization
 Transient current measurements
•
Conclusion
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BURRIED ELECTRODES
LASER SETUP & FRABRICATION
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Burried electrodes – Laser setup
20x Lens
Sample holder
Nitrogen laser
λ = 337nm
τ = 3ns
Webcam
XYZ
Motorized stage
 Tunable parameters
 Scan velocity 1-1000 µm/s
 Laser power
0-160µJ/pulse
 Repetition rate 1-30 Hz
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Burried electrodes – Fabrication
Translation
0.00026
Graphitization
XYZ
Motorized stage
Amplitude (V)
0.00025
0.00024
0.00023
0.00022
0.00021
0.00020
997000
997500
998000
998500
999000
Time (ms)

Photoluminescence during
laser processing
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BURRIED ELECTRODES
STRUCTURAL CHARACTERIZATION
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Structural characterization – Optical microscopy

Optical grade sc-CVD sample
10µm diameter
 Clean surface (Where graphitization starts)
150 µm
20-100 µm diameter
 Cracked Surface (Where graphitization ends)
700µm depth
 Tilted sample
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Structural characterization – 2D Raman mapping

2D Raman depth mapping obtained by integrating diamond peak
1000 CCD cts
1000 CCD cts
Depth
0 CCD cts
10µm

No micro-channel
10µm

0 CCD cts
Micro-channel
with cracks
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Structural characterization – SEM imaging
H2
Plasma

Channel’s clean side after laser
processing

Channel’s clean side after H2 plasma
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BURRIED ELECTRODES
ELECTRICAL CHARACTERIZATION
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Electrical characterization – I(V) measurements
Graphite’s channel resitivity
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5
A
Current (mA)

4
3
ρ(average) = 5.7x10-1 Ω.cm
2
R(500µm) ~ 2kΩ
1
0
-1
-2
0
2
4
6
8
10
Voltage (V)
Match with nanocrystalline graphite given in literature3
[3] T.Ohana, T.Nakamura, A.Goto et al. / Diamond and Related Materials, 12 (2003) 2011
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PC-CVD DETECTOR
ELECTRICAL CHARACTERIZATION
E6 detector grade
10 x 10 x 0.7 mm3
Sample courtesy Alexander Oh
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Electrical characterization – Device leakage current
Comparison between planar and 3D geometry
1E-11
A
Current (A)
(A)
Current

1E-12
1E-13
Planar
3D
 3D
Planar
1E-14
0
200
400
600
Voltage (V)
Voltage
(V)
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PC-CVD DETECTOR
CHARACTERIZATION UNDER
ALPHA PARTICLES
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Characterization under alpha particles – Experimental setup
Fast Charge Sensitive Amplifier
M.Ciobanu, GSI, Germany
Al back
contact
Signal
FCSA
Scope
Al front
contact
Collimator
R
α
Vbias = ±500V
Am-241 Source
5.486MeV
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Characterization under alpha particles - Results

Polarization study – Holes drift (pc-CVD sample)
 Planar
 3D
100
100
Single hit
Trend
80
Single hit
Trend
90
80
60
CCE (%)
CCE (%)
70
40
20
60
50
40
30
20
10
0
0
200
400
600
Hit number
800
1000
0
0
200
400
600
800
1000
Hit number
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Characterization under alpha particles - Results

Polarization study – Electrons drift (pc-CVD sample)
 Planar
100
100
Single hit
Trend
90
80
80
70
70
60
60
50
40
30
20
10
0
Single hit
Trend
90
CCE (%)
CCE (%)
 3D
50
40
30
20
10
0
500
1000
Hit number
1500
2000
0
0
500
1000
1500
2000
Hit number
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Characterization under alpha particles - Results

Holes drift (pc-CVD sample)
α
α
Planar
3D
Planar
3D
100
Counts
Counts
100
10
1
10
1
0
20
40
60
CCE (%)
80
100
0
20
40
60
80
100
CCE (%)
Amplitude has been normalized with the signal of a sc-CVD
« e6 electronic grade » diamond
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Diamond Sensors Laboratory
Characterization under alpha particles - Results

Electrons drift (pc-CVD sample)
α
α
Planar
3D
Planar
3D
100
Counts
Counts
100
10
10
1
1
0
20
40
60
CEE (%)
80
100
0
20
40
60
80
100
CCE (%)
Amplitude has been normalized with the signal of a sc-CVD
« e6 electronic grade » diamond
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Characterization under alpha particles - Analysis

Electric field simulation  3D Geometry but pseudo–3D detector
α
HV
+500V
V/µm
5
4.5
4
3.5
3
High
Low
CCE
700µm
2.5
2
1.5
1
200µm
α
0.5
0
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SC-CVD DETECTOR
E6 electronic grade - <100> oriented
3 x 3 x 0.3 mm3
Sample courtesy Eleni Berdermann
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SC-CVD DETECTOR
OPTICAL CHARACTERIZATION
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Detector’s optical characterization – Optical microscopy

Bulk strain mapping after graphitization
Detector area
Test areas

Micro structured sc-CVD diamond observed with
crossed polarizers
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Detector’s optical characterization – Optical microscopy

Detector after metallization
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SC-CVD DETECTOR
ELECTRICAL CHARACTERIZATION
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Electrical characterization – Device leakage current

sc-CVD sample after plasma O2 etching
1E-5
Current (A)
1E-5
Current (A)
Increasing Voltage
Decreasing Voltage
1E-4
Increasing Voltage
Decreasing Voltage
1E-4
1E-6
1E-7
1E-8
1E-9
1E-6
1E-7
1E-8
1E-9
1E-10
1E-10
1E-11
-200
1E-11
-200
-100
0
100
200
-100
HV on clean surface
100
200
Voltage (V)
Voltage (V)

0

HV on cracked surface
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SC-CVD DETECTOR
TRANSIENT CURRENT
MEASUREMENTS
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Electrical characterization – Setup and methods

Transient current measurements
HV +100V
2D Zone
2D Zone
300µm
Signal
Ampli
Scope
Ultra-Fast 40 dB, 2 GHz Broadband Amplifier
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Transient current measurements - Results

Without collimator
1 ns
Mixed e/h drift
Signal 3D
~500mV
Electrons
drift Signal 2D
Holes drift
~80mV
Signal
2D
~100mV
  Alphas’
side
Alphas’injection
injectionon
oncracked
clean side
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Transient current measurements - Results

With collimator
Mixed e/h drift
1 ns

Alphas’ injection on cracked side
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Transient current measurements - Analysis

Electric field simulation
Planar+3D signal
+100 V
α
V/µm
3
2.5
2
300µm
1.5
1
0.5
0
Planar signal only
α
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Transient current measurements - Results
Experimental results
Signal amplitude (V)

0.6
Planar
3D
0.5
0.4
0.3
Amplitude ratio = 6
0.2
0.1
0.0
-2
0
2
4
6
8
10
Time (ns)
 Selection of relevant events
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Transient current measurements - Results
Analytically calulated signals (A)
2,5x10
-4
2,0x10
-4
1,5x10
-4
Planar
3D
Amplitude ratio = 22
1,0x10
-4
5,0x10
-5
0,0
-2
0
2
4
6
8
Time (ns)
 Theoritical response
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Analytically calulated signals (A)
Analytically calculated signals

2,5x10
-4
2,0x10
-4
1,5x10
-4
Planar
3D
Amplitude ratio = 23.8
1,0x10
-4
5,0x10
-5
0,0
-2
0
2
4
6
8
10
Time (ns)
 2GHz low pass filter
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Transient current measurements - Results
Analytically calulated signals (A)

Analytically calculated signals
2,5x10
-4
2,0x10
-4
1,5x10
-4
1,0x10
-4
5,0x10
-5
Planar
3D
 Ampli + device bandwith
~350MHz
Amplitude’s ratio = 6.2
 Rdevice ~ 520Ω
0,0
-2
0
2
4
6
Time (ns)
8
10
 12 channels connected
 Rchannel ~ 6 kΩ
 350 MHz low pass filter
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Conclusion
• Conductive graphitic structures has been achieved on both pcand sc-CVD sample
• These structures are suitable for detectors applications
• Two dectetors using 3D-geometry electrodes has been produced
• A real improvement between planar and 3D geometry has ben
observed
 Higher signal
 Faster response
 « Polarization effect » decrease on pc-CVD detector
But real 3D detector hasn’t been achieved yet…
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Thanks for your attention !
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