Recent results from the development of 3D detectors in Trento

1
Recent results from the development of 3D
detectors in Trento
Andrea Zoboli1, Maurizio Boscardin2, Luciano
Bosisio3, Gian-Franco Dalla Betta1, Simon
Eckert4, Susanne Kühn4, Ulrich Parzefall4,
Claudio Piemonte2, Marco Povoli1, Sabina
Ronchin2, Nicola Zorzi2
1 INFN Trento and University of Trento,Italy 2
FBK ,Trento, Italy 3 INFN Trieste and University
of Trieste, Italy 4University of Freiburg, Germany
2
Standard 3D detectors, state of the art

• ADVANTAGES
• Electrode distance and active substrate
  thickness decoupled
• - Low depletion voltage
• - Short Collection distance
• - Smaller trapping probability after
  irradiation
• ?higher radiation hardness

Goal SLHC upgrade
First proposed by S. Parker et. Al. in 1997
NIMA395, 328

• DISADVANTAGES
• Not uniform response due to
• electrode configuration
• Complicated technology (DRIE, CMP)
• Higher capacitance with respect to planar

3
Double-Type-Column 3D detector
From G.-F. Dalla Betta et. al., NSS07 talk if
distance d is kept small, performance comparable
to Standard 3D are expected
4
First batch p-on-n detectors

• 1cm x 1cm Area
• 102 strips
• 80µm inter/intra
• column pitch

Readout module
ABCD3T binary chip 20ns shaping time
Re-bondable fan-in
Detectors
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Laser results before irradiation

• Setup
• - 980nm infrared pulsed laser
• x-y motorized stage
• 5µm resolution (first row)
• 2µm resolution (second row)

Position dependent charge collection measurements
Investigation on the CC uniformity
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Charge collection before irradiation
Setup - Sr90 beta source, MIP like charge
deposition within the active area - Events
triggered by two scintillators in coincidence
Maximum collected charge 2.45fC, (15000
electrons) lower than 22000 electrons, due to not
optimized columns
ballistic deficit
From ISE-TCAD simulation total collection time
30ns
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Irradiation study
All the samples irradiated with 24MeV protons in
Karlsruhe at different fluences F1 5 x
1014 cm-2 F2 1 x 1015 cm-2 F3 2 x 1015
cm-2
Charge collection measurements (at -11C) after
irradiation have been performed before and after
annealing Standard annealing step 60C for 80
minutes
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Laser results after irradiation
Before irradiation
Type inversion observed, main junction on the
back column The signal is now growing both from
the back and from the front column
Double junction effect
10V
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Charge collection after irradiation (1)
Fluence 5 x 1014 cm-2 Acceptor rate for FZ
n-type gc0.02 cm-1 from Kramberger et. al.
3rd Workshop on Advanced Silicon
Radiation Detectors (3D and P-type
Technologies) Expected lateral depletion 28V
(good agreement with results)
unirradiated
irradiated
Charge trapping is the responsible for the loss
of charge after irradiation
Collected charge fC
Bias voltage V
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Charge collection after irradiation (2)
Fluence 1 x 1015 cm-2 -Lateral depletion at 40V
-Beneficial annealing reduces the effective
substrate doping leading to higher charge
collection
Fluence 2 x 1015 cm-2

• -Lateral depletion at 80V, lower than
• the expected value from gc 0.02 cm-1
• a similar reduction has been also observed
• for n-type FZ by Kramberger

Kramberger et. al. 3rd Workshop on Advanced
Silicon Radiation Detectors (3D and P-type
Technologies)
SNR increases up to 200V, than drops due to high
induced noise from leakage current
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Second batch n-on-p detectors

• P-type batch already fabricated and electrically
  tested with good results. Electron readout would
  give faster signal and higher radiation hardness.
• Pixel structures connected successfully to FE-I3
  ATLAS chip and currently under test.

see Alessandro La Rosa talks for preliminary data

3D diodes (stcdtc 80100µm)
13 microstrip detectors (stc dtc) 1 strip
CAP test
6 ATLAS pixel detectors
6 CMS pixel detectors
16 ATLAS pixel detectors
CMS small pixel detectors (8)
3D diodes (stcdtc 80100µm)
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C-V on 3D diodes (1)
1
2
1
As in Single Type Column depletion proceeds first
sideways, parallel to surface.
Lateral depletion 3V
2
After lateral depletion an extra voltage is
required to deplete the volume below the column
Full depletion 12V
Cback at FD 14 pF Cback at FD 35 fF/col
Cback at FD 4.4pF/cm in strip-like
configuration
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C-V on 3D- diodes (2)
From the cilindrical capacitor model its
possible to estimate the overlap between columns
h 115µm. Ohmic column as deep as the
substrate
SEM picture after first DRIE
Geometrical data deduced by measurements have
been used in ISETCAD tool in order to reproduce
the real structure. Simulation of a diode
structure is in good agreement with measurements
220µm
120µm
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I-V on Microstrip detectors
Low defectivity Only one strip shows a high
leakage current at 70V. Full depletion voltage
12V
I(70V) 0.2nA / cm
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Expected performances
Simulation of a MIP particle at 40V
bias Collection time N-type batch DDTC, 300µm
thick 35ns P-type batch DDTC, 220µm thick
10ns
N-type DDTC Transient simulation
10 ps
100 ps
1 ns
5 ns
10 ns
electron density
hole density
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Single channel beta setup
plastic scintillator
3D
Sr90
SiPM

Pb shield
-
Vthreshold
Trigger
To PC
Signal IN
Charge amplifier
AMPTEK A250
AMPTEK DP4000
-Events are triggered by a scintillator, glued on
a SiPM (fabricated at FBK) -SiPM gives signal
higher than 100mV, and can be directly connected
to a comparator -The threshold can be set to
select only high energy electrons (MIP)
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Single channel beta setup, first test
The calibration of the readout has been made
taking the 59.5keV line from Am241
Landau from a p-on-n 3D diodes at 5V bias
Mean charge 3.6 fC 22500 el.
No triggering on high energy electrons

• Still some problem with the trigger
• Amptek readout chip has shaping time adjustable
  from 800 ns to 56us,
• so we have to move to faster shaping time
  readout, comparable with ATLAS readout

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DTC with passing through columns
ATLAS pixel detectors
CMS pixel detectors
Strip and diode detectors

• New double-sided technology
• defined by FBK
• No need for support wafer
• Also suitable for dual-readout pixel/strips
• (recently proposed by C. Da Via et al., NIMA 594,
  7-12, 2008)

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ATLAS and CMS Pixel
p column
n column
ATLAS 2E
ATLAS 3E
ATLAS 4E
CMS SC1
CMS SC2
CMS SC3
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Planar active edge simulated structures
P-on-N planar diode with N active
edge. Simulation of the breakdown voltage at
several d1 distances 10µm-30µm, with 5µm
step. Oxide charge concentration
1,3,5x1011cm-2
115 µm
Oxide
Active edge
diode electrode
200µm
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Planar active edge Field Plate
Field plate
Field plate of 3.6µm
Efield value at 0.01µm below surface
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Planar active edge Floating region
Floating region
The floating region is placed mid-way between the
electrode and the active edge
- Field Plate seems to be more efficient than the
floating electrode - higher bias voltages can be
applied before reaching breakdown
Efield value at 0.01µm below surface
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Conclusions

• N-type DDTC fabricated they exhibit very low
  leakage current
• and full depletion voltage lower than 5V.
• Net improvement respect to STC.
• Detector are working up to fluences of 2x1015
  cm-2, comparable results
• with respect to planar despite not optimized
  columns depth.
• Carrier multiplication at high voltages has to
  be understood with the aid
• of TCAD simulations.
• New P-type DDTC fabricated and currently under
  test. Fabrication of
• full-3D detectors is also just started.
• New single channel beta setup will allow for
  functional characterization
• with MIP particle (in house) on 3D pad
  detectors.
• Simulations of breakdown properties of active
  edges planar structures
• are being performed to aid the layout design