the atlas hybrid silicon pixel detector · the atlas pixel detektor. cbm, gsi darmstadt 14.5.2002,...
TRANSCRIPT
![Page 1: The ATLAS Hybrid Silicon Pixel Detector · The ATLAS Pixel Detektor. CBM, GSI Darmstadt 14.5.2002, P. Fischer 32 Results of single chip & module prototypes Cable to power & DAQ LVDS](https://reader030.vdocument.in/reader030/viewer/2022040717/5e2282ad67b9306a2106e375/html5/thumbnails/1.jpg)
The ATLAS
Hybrid Silicon Pixel Detector
Peter Fischer
Universität Bonn
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2CBM, GSI Darmstadt 14.5.2002, P. Fischer
Why pixels - Introduction
The pixel detector
§ Modules, mechanics etc.
§ The silicon sensor
§ The front end electronics
Some results
Status of the project
The ATLAS Pixel Detektor
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3CBM, GSI Darmstadt 14.5.2002, P. Fischer
Why Pixels ?
§ Avoid ambiguities (‚ghost hits‘) at high multiplicities ⇒ need true 2D detector !
§ Survive high radiation level ⇒ need very low noise
§ Note: Strip detectors have better resolution & shorter radiation length!
???
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4CBM, GSI Darmstadt 14.5.2002, P. Fischer
Bump pitch: 50µmdiameter: 20µm(IZM, Berlin)
Hybrid Pixel detectors
§ Every pixel is connected to a separate amplifier on the readout chip
§ Low input C ⇒ low noise ⇒ low threshold ⇒ can operate with thin detectors and small signals after irradiation ⇒ intrinsic radiation hardness
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5CBM, GSI Darmstadt 14.5.2002, P. Fischer
Requirements for the ATLAS pixel detector
§ Pixel Size 50 x 400 µm2 (as small as possible, limit is power)
§ Typical Signal 1fC = 6000 electrons (mip in 300µm silicon in pixel corner)§ Threshold 2000 electrons (quite a bit smaller than signal)§ Noise 200 electrons (quite a bit smaller than the threshold)§ Threshold dispersion 200 electrons (not larger than the noise)§ Leakage current tolerance 100nA / pixel (probably more than we need)
§ Speed 25ns timing precision (bunch crossing of LHC, 'time walk')§ Data storage up to 160 clock cycles (level 1 latency)
§ Radiation Tolerance 50 Mrad, 1015 n/cm2 (10 years operation)
§ Power 50µW / pixel (including periphery, ~ 10W / Module)§ Material ~ 1% X0 per layer
§ Track efficiency ≥ 99 % (including gaps between sensors)
§ Many channels 108 (must have zero suppression)
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6CBM, GSI Darmstadt 14.5.2002, P. Fischer
Why pixels - Introduction
The pixel detector
§ Modules, mechanics etc.
§ The sensor
§ The front end electronics
Some results
Status of the project
The ATLAS Pixel Detektor
![Page 7: The ATLAS Hybrid Silicon Pixel Detector · The ATLAS Pixel Detektor. CBM, GSI Darmstadt 14.5.2002, P. Fischer 32 Results of single chip & module prototypes Cable to power & DAQ LVDS](https://reader030.vdocument.in/reader030/viewer/2022040717/5e2282ad67b9306a2106e375/html5/thumbnails/7.jpg)
7CBM, GSI Darmstadt 14.5.2002, P. Fischer
The ‚flex‘ Module
Flex capton solution:
§ Connections between FE-Chips,
module control chip, other components
and cable through a thin capton PCB
§ Size = 16.4 × 60.8 mm2
§ 16 chips with ~ 50000 pixels total§ ~ 2000 modules needed
§ Material:- silicon sensor 0.22 %- chips thinned to 200 µm 0.14 %- bumps, bonds, glue,... 0.10 %- support, cooling, caps,... 0.90 %
Total: 1.4 – 1.8 %
FE-Chip FE-Chip
sensorMCC
2 layer capton PCB control chip
Wire bonds
Larger pixels between chips
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8CBM, GSI Darmstadt 14.5.2002, P. Fischer
1st generation: ‚bare‘ module on rigid support
sensor
FE Chip FE Chip
ALL wire bondsmust be good!
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9CBM, GSI Darmstadt 14.5.2002, P. Fischer
2nd generation: flex module in mounting frame
frame
flex
MCC
FE chipsStand over
viewed from chip side
viewed from flex side
FE chips
FE-Chip FE-Chip
sensorMCC
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10CBM, GSI Darmstadt 14.5.2002, P. Fischer
Overall layout
~ 1m
§ Global support is a flat panel structure§ Made from carbon composite material
(IVW, Kaiserslautern)§ Total weight is 4.4kg§ 3 pieces, center part consists of two
half-shells to open
modules modules
3 barrels
2 x 3 disks
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11CBM, GSI Darmstadt 14.5.2002, P. Fischer
Cooling
§ Is very important
- Contributes significantly to material budget
- Limits the power / performance of electronics
- Detectors must stay below –6oC to limit damage from irradiation (see later)
§ ATLAS uses evaporative cooling:
- Cooling by evaporation of fluorinert liquid (C4F10 or C3F8) @ -20oC. Needs pumping.
- Low mass (gas!)
- small diameter tubes (only small pressure drops)
- Very large cooling capacity
- Aluminum tubes must withstand 6 atm if pumping stops and coolant develops its full vapor pressure.
§ All components must cope with thermal cycling 25oC ⇔ -20oC
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12CBM, GSI Darmstadt 14.5.2002, P. Fischer
Barrels and staves
§ Barrels are made from parallel staves§ One stave contains 13 modules which are shingled for overlap in z
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13CBM, GSI Darmstadt 14.5.2002, P. Fischer
Barrels and staves
§ Stave is a carbon structure with an Al tube for cooling§ Staves are tilted for overlap in phi (+change sharing)§ Production mainly in Germany, Italy, France
Al tube forcoolant
Carbon support
Shingled(dummy) modules
Pictures are from a mechanical test stave
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14CBM, GSI Darmstadt 14.5.2002, P. Fischer
Disks and Sectors
§ Disks are divided into sectors§ Coolant flows in tube between two C-C facings§ Modules are arranged on both sides for overlap§ Production in USA
cooling test of full disk(@ LBNL)Sector with 3
‚modules‘
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15CBM, GSI Darmstadt 14.5.2002, P. Fischer
The MCMD module concept
f
connection vias
MCMD module:
§ Capton is replaced by multi-layer structure
deposited onto the sensor
§ Very compact module, no wire bonds,
all pixels can have same size!
§ Slightly more material (‚balcony‘)
§ First working module had excellent
performance
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16CBM, GSI Darmstadt 14.5.2002, P. Fischer
MCMD technology
§ Production at Frauenhofer Institut IZM (Berlin), still yield problems
§ Bumping with lead-tin bumps at IZM
§ Very interesting concept for many future applications!
50 µm
20 µm
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17CBM, GSI Darmstadt 14.5.2002, P. Fischer
Why pixels - Introduction
The pixel detector
§ Modules, mechanics etc.
§ The sensor
§ The front end electronics
Some results
Status of the project
The ATLAS Pixel Detektor
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18CBM, GSI Darmstadt 14.5.2002, P. Fischer
Radiation damage of silicon sensors
§ Irradiation of silicon leads to bulk damage and oxide charges at the surface§ Bulk damage:
- increased ileak → increased noise
- ‚reverse annealing‘ → keep sensor cold (- 60C)
- Type inversion → n-side readout
- Change in doping → increased depletion voltage (guard rings!) , partial depletion
§ Oxide charges:- increased field strength → special designs
1011 1012 1013 1014 1015
Φeq [cm-2]10-6
10-5
10-4
10-3
10-2
10-1
∆I /
V
[A/c
m3 ]
n-type FZ - 7 to 25 KΩcmn-type FZ - 7 to 25 KΩcmn-type FZ - 7 KΩcmn-type FZ - 7 KΩcmn-type FZ - 4 KΩcmn-type FZ - 4 KΩcmn-type FZ - 3 KΩcmn-type FZ - 3 KΩcm
n-type FZ - 780 Ωcmn-type FZ - 780 Ωcmn-type FZ - 410 Ωcmn-type FZ - 410 Ωcmn-type FZ - 130 Ωcmn-type FZ - 130 Ωcmn-type FZ - 110 Ωcmn-type FZ - 110 Ωcmn-type CZ - 140 Ωcmn-type CZ - 140 Ωcm
p-type EPI - 2 and 4 KΩcmp-type EPI - 2 and 4 KΩcm
p-type EPI - 380 Ωcmp-type EPI - 380 Ωcm
0 0.5 1 1.5 2 2.5 3 3.5Φeq [1014cm-2]
1
2
3
4
5
6
7
|Nef
f| [1
012 c
m-3
]100
200
300
400
Vde
p [V
] (3
00µm
)
neutronsneutrons
neutronsneutronspionspionsprotonsprotons
pionspionsprotonsprotons
oxygen rich FZ
standard FZstandard FZ
ileak
Neff
n p
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19CBM, GSI Darmstadt 14.5.2002, P. Fischer
Problem of type inversion
p+ pixels on n- material n+ pixels on n- material
Bulk is n- beforeirradiation
p- afterirradiation
Need fulldepletion!
Voltage drop onReadout side
Can be operated partially depletedL
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20CBM, GSI Darmstadt 14.5.2002, P. Fischer
ATLAS pixel sensor production has started
§ n+ pixels in n- sensor§ Multi guard ring structures hold up to 1000V§ Isolation of pixels with moderate dose p-spray
has highest field strength BEFORE irradiation§ Punch through dot and bias grid for testing
before bumping§ Use of oxygenated silicon
Bias grid
Punch through dot
Bump contact
P-sprayP-spray
Production sensor
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21CBM, GSI Darmstadt 14.5.2002, P. Fischer
Performance of irradiated sensor
§ Sensors are irradiated to fullATLAS fluence (1015 neq/cm2)§ They are then bump bonded to
rad-soft ATLAS Prototype FE-Chips§ Measurements are performed in
test beam with a Si-Strip telescopeas reference detector§ Pixel Chips give some information
about collected charge.
§ Vbias > 600V possible§ Homogenous charge collection
also in pixel corners§ 98.4% track efficiency§ These sensors will survive 10 years
of ATLAS operation
measured with threshold = 2000 e
RESULTS
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22CBM, GSI Darmstadt 14.5.2002, P. Fischer
Why pixels - Introduction
The pixel detector
§ Modules, mechanics etc.
§ The sensor
§ The front end electronics
Some results
Status of the project
The ATLAS Pixel Detektor
![Page 23: The ATLAS Hybrid Silicon Pixel Detector · The ATLAS Pixel Detektor. CBM, GSI Darmstadt 14.5.2002, P. Fischer 32 Results of single chip & module prototypes Cable to power & DAQ LVDS](https://reader030.vdocument.in/reader030/viewer/2022040717/5e2282ad67b9306a2106e375/html5/thumbnails/23.jpg)
23CBM, GSI Darmstadt 14.5.2002, P. Fischer
Electronic Components of the Pixel System
1 Sensor16 front end chips (FE)1 module controller chip (MCC)2 VCSEL driver chips (VDC)1 PIN diode receiver (DORIC)
module control room
Optical receiversReadout Drivers (ROD)Readout Buffers (ROB)Timing Control (TIM)Slow Control, Supplies
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24CBM, GSI Darmstadt 14.5.2002, P. Fischer
The Front End Chip
§ Chip size: 7.4mm x 11mm§ Pixels: 18 x 160 = 2880§ Pixel size: 50µm x 400µm
§ Technologies: 0.8µm CMOS (FEA,FEB)0.8µm BiCMOS (FED)0.25µm CMOS (FEI)
§ Operates at 40 MHz§ Zero suppression in every pixel§ Data is buffered until trigger arrives§ Serial control and readout, LVDS IO
§ Analog part with- 40 µW power dissipation / Pixel- ~200 e noise - Amplitude measured via pulse width
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25CBM, GSI Darmstadt 14.5.2002, P. Fischer
Pixel Analog Part
feedback uses constant current- high stability for fast shaping- tolerates > 100 nA leakage- linear decay
Analog information- measure width of hit- works nicely due to
linear discharge
Individual adjustment of- Threshold (5 bit in FEI)- feedback current (FEI, 5 bit)- ranges are adjustable
Sensor isconnected
here
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26CBM, GSI Darmstadt 14.5.2002, P. Fischer
FED: Preamplifier Pulse Shapes
(Measured on FED test chip with internal chopper, no sensor)
Very linear discharge⇒ good ToT
Very smallshaping loss
Different injected charges Different feedback currents
200 mV/div, 200ns/div 200 mV/div, 200ns/div
1 mip
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27CBM, GSI Darmstadt 14.5.2002, P. Fischer
Data Readout
§ If a trigger arrives, the time of the hit (leading edge data) is compared to the time for hits associated to this trigger. Valid hits are flagged, older hits are deleted. § The trigger is queued in a FIFO
§ A time stamp (7bit Gray Code) is distributed to all pixels§ When a pixel is hit, the time of rising and
trailing edges are stored in the pixel
§ The hit is flagged to the periphery with a fast asynchronous scan
§ Time information and pixel number are written into a buffer pool (common to a column pair)
§ The hit in the pixel is cleared
§ All valid hits of a trigger are sent out serially. All triggers in the FIFO are processed.
4 simultaneous tasks are running permanently:
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29CBM, GSI Darmstadt 14.5.2002, P. Fischer
FEI design: from 0.8µm DMILL to rad hard 0.25µm
Example: 8 bit DAC+Regsfull custom layout:gain x 6 in area !
0.25µm80x200 µm2
DMILL500x200 µm2
0 1 2 30
50
100
150
200
250
300
DAC64 DAC128 DAC192 DAC255
Cur
rent
[µA
]
DAC Supply voltage VDDA [V]
0 32 64 96 128 160 192 224 256-0,5
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
INL
[LS
B] (
offs
et b
y 1
per
curv
e)
DAC setting
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31CBM, GSI Darmstadt 14.5.2002, P. Fischer
Why pixels - Introduction
The pixel detector
§ Modules, mechanics etc.
§ The sensor
§ The front end electronics
Some results
Status of the project
The ATLAS Pixel Detektor
![Page 30: The ATLAS Hybrid Silicon Pixel Detector · The ATLAS Pixel Detektor. CBM, GSI Darmstadt 14.5.2002, P. Fischer 32 Results of single chip & module prototypes Cable to power & DAQ LVDS](https://reader030.vdocument.in/reader030/viewer/2022040717/5e2282ad67b9306a2106e375/html5/thumbnails/30.jpg)
32CBM, GSI Darmstadt 14.5.2002, P. Fischer
Results of single chip & module prototypes
Cable topower & DAQ
LVDS IO
Single chipwith sensor
HV(sensor bias)
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33CBM, GSI Darmstadt 14.5.2002, P. Fischer
Threshold adjustment on a single chip
0 320 640 960 1280 1600 19202000
2500
3000
3500
4000
4500
5000
FEA mit Detector IZM4, tuned
Sch
wel
le [e
- ]
Pixel
0 320 640 960 1280 1600 19202000
2500
3000
3500
4000
4500
5000
FEA mit Detector IZM4, untuned
Sch
wel
le [e
- ]
Pixel
§ Trim range can be selected to find best compromise betweendynamic range and resolution§ Situation is much better in FEI with 5 trim bits !
Threshold trimColumn structure, edge pixels! Still some bad thresholds !
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34CBM, GSI Darmstadt 14.5.2002, P. Fischer
Module thresholds & noise
§ Module with 16 chips, here FEB
§ Threshold and Noise arecomparable to single chips.
§ Performance of several modules:
Module type
Front-end
Bump Threshold [e]
Noise [e]
Bare FEB IZM 2000 140 Flex FEB IZM 2000 180 Bare FEC IZM 2500 140 Flex FEB IZM 3000 160 Flex FEB Alenia 3600 180
b
Threshold=3000 eSigma=170 e
Noise=160 e
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35CBM, GSI Darmstadt 14.5.2002, P. Fischer
Source measurement with 55Fe
§ 55Fe-source (6keV γ) deposits
only 1700 e-h-pairs
§ FE-C chip with thresholds tuned
to ~1200 e-
§ Some bump problems at edge(one of the first assemblies)
§ The chip can be operated at very low threshold
0 2 4 6 8 10 1 2 14 160
2 0
4 0
6 0
8 0
1 0 0
1 2 0
1 4 0
Column
Row
Edge sensors are longer (600 µm)⇒ higher count rate
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36CBM, GSI Darmstadt 14.5.2002, P. Fischer
Source measurement on a module with 241Am
§ Spot of 241Am-source on two neighboring chips of a module§ Module without MCC: chips were illuminated one after the other
5 10 15 20 25 30 35
20
40
60
80
100
120
140
160
chip #4 chip #5
column
row
Higher count rate in600 µm long edge pixels
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37CBM, GSI Darmstadt 14.5.2002, P. Fischer
spatial resolution in test beam§ Consider short pixel dimension:
§ σ1hit = 22µm, σ2hit=5µm
§ σall = 13µmafter irradiation: 14.5µm = 50µm/√12§ Less 2 hit clusters after irradiation§ No improvement with analog info!
1 hit analog
1 hit digital
2 hit digital
2 hitanalog
Single hitsbad resolution
double hitsgood resolution
50µm
error
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38CBM, GSI Darmstadt 14.5.2002, P. Fischer
Time Walk
§ Detector is a capacitive load
⇒ preamplifier has slow rise time (limited by power!)
⇒ hits only slightly above threshold fire discriminator later
⇒ hit is lost if delay > 25ns
§ This is one of our biggest problems. Must still check performance of FEI.
§ Possible improvements: digital correction (FEI), zero crossing
t
Need ~1000 e- more thanthreshold for in-time hit
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39CBM, GSI Darmstadt 14.5.2002, P. Fischer
Track Efficiency
§ Despite marginal time walk, efficiency is ok after irradiation !
§ Here: Sensor is moderate p-spray with bias grid. Chip threshold is 3000 e-
Non-irradiatedefficiency = 99.1%
(ns) (ns)
Irradiated (1015 neqcm-2)efficiency = 98.4%
Delay between particlearrival and 40 MHz clock.
We can choose best timing!
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40CBM, GSI Darmstadt 14.5.2002, P. Fischer
Depletion Depth after irradiation
not depleted
depleted
track entrance point from beam telescope
Track depth
depth (mm)0
1000
2000
0 0.1 0.2 0.3
depletion 0.2868
-30*
depth (mm)0
1000
2000
0 0.1 0.2 0.3
depletion 0.1879
-30*
-600 V 1x1015
depth (mm)0
1000
2000
0 0.1 0.2 0.3
depletion 0.1047
-30*
-300 V 1x1015
non irradiated, full depletion
1x1015, 600 V, 190µm
1x1015 , 300 V, 105µm
Particle track
Depletion depth is 190 µm @ 600 Vafter 1015 cm-2 (full ATLAS dose!)
No chargeseen here
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41CBM, GSI Darmstadt 14.5.2002, P. Fischer
ATLAS pixel: Status
We are (nearly) ready to build the detector- sensors are very mature & are ordered
- FEI radiation hard electronics (0.25µm):performance is good, radiation hardness has been confirmed
- bump bonding: process matured over 4 years
- all module production steps are established
- staves, disks and global support are being produced
Further development is needed for- cables for power & signals
- connections at module, patch panels etc.
- signal transmission ICs