material developments for the hl-lhc upgrade of the cms tracker
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Material developments for the HL-LHC upgrade of the CMS tracker . 19 January 2012 Joachim Erfle University of Hamburg. Overview. The tracker and its challenges at HL-LHC Some layout possibilities for a new tracker and sensor modules The basic working principle of silicon sensors - PowerPoint PPT PresentationTRANSCRIPT
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
19 January 2012
Joachim ErfleUniversity of Hamburg
Material developments for the HL-LHC upgrade of the CMS tracker 19/01/12
page 1
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Overview
• The tracker and its challenges at HL-LHC• Some layout possibilities for a new tracker and sensor modules• The basic working principle of silicon sensors• A campaign to find the next tracker‘s sensor material• First results of this campaign
19/01/12page 2
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
The current tracker
19/01/12page 3
• Over 200m2 active silicon• About 26000 sensors• 9.6 million strip channels +
66 million pixel channels
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Challenges for the tracker at HL-LHC
19/01/12page 4
Required features for HL-LHC:• Higher radiation tolerance• More (smaller) channels for a
lower occupancy at high pile-up• Trigger information for level 1
New tracker needed
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Two possible new sensor module layouts
19/01/12page 5
courtesy of S. Mersi, CERN
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Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Possible new tracker layout
19/01/12page 6
courtesy of S. Mersi, CERN
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Strip sensors
19/01/12page 7
Basic layout of a strip sensor
Basically two different types:• N doped bulk:
• Holes readout slower
• Easier to produce• Tends to undergo type inversion
• P doped bulk:• Electron readout
faster, less trapping• Harder to produce
Depletion of a n-bulk sensor
Depletion of a p-bulk sensor
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Radiation damage in silicon
19/01/12page 8
Two types of radiation damage: • Surface damage• Bulk damage main problem for hadronic irradiation
• Subdivided in three damage types:
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Changes effective doping concentration full depletion voltage
Reduces charge collection
Increases leakage current
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Goals of the HKP-campaign
The main challenges for the tracker at the HL-LHC will be:• Higher radiation dose (up to a fluence of Φeq = 1016 cm-2)
• Higher occupancy
The current tracker would not withstand the radiation and also develop occupancy problems→ Find best best suitable silicon material and layout for a future tracking detector
To achieve that we investigate a large variety of materials:• Different oxygen, carbon,… content
• Different bulk doping (n and p)
Test sensor geometries and layoutsIrradiations with neutrons or/and protons to simulate HL-LHC radiation dose
19/01/12page 9
Joachim [email protected]
structure to study
pad diodes material
baby strip sensor reference design / material
baby strip sensor with integrated pitch adapter
design
pixel sensor reference Design / material
multigeometry pixel layout parameters
multigeometry strips layout parameters
baby strixel design
test-structures process parameters
Wafer overview: HPK-campaign
Material developments for the HL-LHC upgrade of the CMS tracker 19/01/12
page 10
Joachim [email protected]
Silicon material
Material developments for the HL-LHC upgrade of the CMS tracker 19/01/12
material thinning method active thickness physical thickness
FZ deep diffusion 120,200,300 μm 320 μm
FZ --- 200 μm 200 μm
FZ handling wafer 120 μm 320 μm
MCz --- 200 μm 200 μm
Epi handling wafer 50,100 μm 320 μm
page 11
Of each material there are 3 different types:- n-type (N)Two different strip isolation technologies for p-bulk:- p-type with p-stop (P)- p-type with p-spray (Y)
Joachim [email protected]
Wafer-Processing (deep diffusion)
page 12
• Standard method for thinning: wafer bonding of Si to Si-substrate (low ohmic)
• Well known process
• Relatively expensive
• New method: deep diffusion
• Active volume of a 320μm wafer reduced by diffusing high doping from the back.
• At high irradiation thick sensors not fully depletable
• Mean free path of charge carriers severely reduced due to trapping for highly irradiated sensors
→ In thin sensors less charge is trapped and
voltage needed for full depletion is lower.
Material developments for the HL-LHC upgrade of the CMS tracker 19/01/12
pn-junctionactive thickness
active volume inactive volume
physical thickness
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Sequence of Measurements and irradiations
19/01/12page 13
1. Pre qualification2. First irradiation3. Single irradiation qualification4. Second irradiation5. Measurements and time development
of defect (annealing) studies
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courtesy of S. Müller, KIT
HL-LHC: Lint=3000 fb-1
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Irradations
Neutrons: 1 MeV (TRIGA Reactor Ljubljana)Protons: 23 MeV (Karlsruhe cyclotron)
19/01/12page 14
radius protons Φeq [cm-2] neutrons Φeq [cm-2] total Φeq [cm-2] active thickness40 cm 3 10∙ 14 4 10∙ 14 7 10∙ 14 ≥ 200 μm
20 cm 1 10∙ 15 5 10∙ 14 1.5 10∙ 15 ≥ 200 μm
15 cm 1.5 10∙ 15 6 10∙ 14 2.1 10∙ 15 ≥ 200 μm
10 cm 3 10∙ 15 7 10∙ 14 3.7 10∙ 15 ≤ 200 μm
5 cm 1.3 10∙ 16 1 10∙ 15 1.4 10∙ 16 < 200 μm
courtesy of S. Müller, KIT
HL-LHC: Lint=3000 fb-1
Joachim [email protected]
Volume current versus fluence
Material developments for the HL-LHC upgrade of the CMS tracker 19/01/12
Currents match expected value from literature (M. Moll‘s thesis) within the uncertainties. -> dose measurements are ok.
page 15
currents are measured after annealing of 10 min@ 60°C at 0°C and scaled to 20°C
Δ 𝐼𝑉 =𝛼Φ𝑒𝑞
J. Erfle, UHH
neutrons
neutrons
protons
protons
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Type-inversion and the effective doping
19/01/12page 17
Effective thickness reduced,but fully functional
Partly depleted sensor, type inverted
Readout channels are somewhat „isolated“ from collected charge
Partly depleted sensor, not type inverted
Defects close to the bandgap perform like dopants, so they change the effective doping by providing a free electron or hole
Influence on:• Full depletion voltage• Type of bulk doping
Possible problems:• full depletion voltage can rise above the
value that can be applied• If that happens in the type inverted case,
the charge measurement is disturbed
Joachim [email protected]
Neff for different materials / irradiations
Material developments for the HL-LHC upgrade of the CMS tracker 19/01/12
page 18
protons
neutrons
All measured n-type materials (FZ and MCz) are type-inverted after neutron or proton irradiation.
n-type
capacitances are measured at 0°C, 1kHz after annealing of 10min@60°C
J. Erfle, UHH
J. Erfle, UHH
Joachim [email protected]
Neff for different materials / irradiations
Material developments for the HL-LHC upgrade of the CMS tracker 19/01/12
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n-type p-type
protons
neutrons
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0°
C, 1
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J. E
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UH
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J. Erfle, UHH
J. Erfle, UHH
All n-type materials undergo type inversionNo p-type material undergoes type inversionAll p-type materials show a steep increase in Neff and therefore depletion voltage
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Time resolved charge collection measurement with TCT shows type inversion
19/01/12page 20
FZ320P FZ320N
not type inverted type inverted
unirradiated
p@3E14
courtesy of T. Pöhlsen, UHH courtesy of T. Pöhlsen, UHH
- holes - electrons
U=300VU=600V
courtesy of J. Lange
Laser: 672 nm, red3µm penetration depth
type inversion of FZ and MCz n-type materials is confirmed by TCT.
Signals are measured at 0°C, after annealing of 10min@60°C
E
depth
RearFront
red
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
CCE of diodes, after p@3E14
19/01/12page 21
p-type:holecollection
n-type:electroncollection
infrared laserred laser, front injection
p-typen-type
measurements are performed at 0°C and 600V, with 20ns integration time
unirradiated
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courtesy of J. Lange
infrared laser: CCE is about 90%
Electrons only: CCE ~ 85%, holes collection only: CCE ~ 67%Electron readout performs better
infrared
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Signal of FZ320P baby sensor, after p@3E14
19/01/12page 22
Signal induced by a 90Sr source, readout by ALiBaVa
Vdepl
courtesy of K. Hoffman, KIT
CCE of FZ320 p-type is about 87% at p@3E14, compared to non-irradiated
measurements are performed at -20°C
Joachim [email protected]
Some experimental structures
Material developments for the HL-LHC upgrade of the CMS tracker 19/01/12
Seite 23
• Idea to reduce occupancy and increase resolution
• To be able to read out from the sides, inner strips are routed out in the first metal layer
Strip-sensor with integrated Pitchadapter in the first metal layer
Strixel-sensor
• Pitchadapter needed for readout-chip connection
• Is it possible to integrate it on the sensor without loosing active area?
courtesy of A. Kornmayer, KIT
Joachim [email protected]
First results for integrated pitch adapter
19/01/12page 24
Electron from a Sr90-sourceat different positions
Flat S/N in standard region of about 17
Reduced S/N in PA-region, noise stays constant
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Material developments for the HL-LHC upgrade of the CMS tracker
Joachim [email protected]
First results for strixel sensors
19/01/12page 25
Seed strip (far)
1. far neighbour
1. near neighbour
Seed strip (near)
1. near neighbour1. far neighbour
Electron from a Sr90-source at near area Electron from a Sr90-source at far area
Seed strip (far)1. far neighbour
1. near neighbour
Signal in the far area only measured on strips in the far area.Signals in near area appear also on far strips
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Material developments for the HL-LHC upgrade of the CMS tracker
Joachim [email protected]
HL-LHC: CMS needs completely new tracking detectors:• Higher granularity• More radiation toleranceHPK-campaign to identify Si-material, polarity, sensor-layout
First results:• Diode currents increase as a function of fluence as expected• Neff shows:
• - type inversion for all n-type materials• - no type inversion for p-type, with steep increase• Not expected:
• CCE with baby sensors and diodes reduced to ~90% after 3E14 proton irradiation
Conclusions
Material developments for the HL-LHC upgrade of the CMS tracker 19/01/12
page 26
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Outlook
19/01/12page 27
• More irradiations to come: Higher fluences!• Trying to understand material properties in detail• Full annealing studies to be done Define the material and layout to be used in the Phase II upgrade of the tracker
Thank You !
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
Backup
19/01/12page 28
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
CCE of FZ320 after proton irradiation
19/01/12page 29
measurements are performed at 0°C
courtesy of T. Pöhlsen
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
TCT pulses – p-type
19/01/12page 30
FZ200P FZ320P MCZ200P
not type inverted
courtesy of T. Pöhlsencourtesy of T. Pöhlsencourtesy of T. Pöhlsen
300V 600V 250V
measurements are performed at 0°C, using a red laser
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
TCT pulses – n-type
19/01/12page 31
FZ200N FZ320N MCZ200N
type invertedmeasurements are performed at 0°C, using a red laser
courtesy of T. Pöhlsencourtesy of T. Pöhlsencourtesy of T. Pöhlsen
200V300V300V
Joachim [email protected]
Material developments for the HL-LHC upgrade of the CMS tracker
oxygen content
19/01/12page 32
material bulk resistivity oxide concentration
FZ320P 3-8 3,50E+016
FZ200P 3-8 3,00E+017
FZ120P 3-8 5,00E+017
FZ320N 1.2-2.4 1,80E+016
FZ200P 1.2-2.4 3,00E+017
FZ120P 1.2-2.4 5,00E+017
MCZ200P >2 3,75E+017
MCZ200N >0.5 3,00E+017