Production of a large number of silicon pixel sensors and the application in

comic ray experiment and imaging calorimeter

Shinwoo Nam, Il H. Park, Jae H. Park, Nahee Park (Ewha Univ., Seoul)

15*13 mm2

2

Two Applications

• Cosmic Ray nuclei charge measurement by dE/dx– For CREAM Experiment

• Silicon Tungsten Calorimeter – For future ILC ECAL and P

henix NCC

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Cosmic Rays

Taken from Simon Swordy

http://hep.uchicago.edu/~swordy/crspec.html

All particle spectrum from direct and indirect cosmic ray observations

Direct Measurement, Balloon, Satellite(< 1015 eV)

Indirect Measurement, Air Shower(> 1015 eV)

~ E-2.7

~ E-3.0

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• Galactic component : Stochastic collision with moving magnetic clouds produced from Supernova Remnants accelerates comic rays.

• Acceleration limit increases for high-Z nuclei.

5

∝

Energy loss of a charged particle in the matter by Bethe-Bloch formula

dE/dx : logarithmic dependence on particle energy

Radiative energy loss is small for proton and heavy nuclei

Charge Measurement of high energy particles (1012 - 1015 eV)

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Silicon sensor for charge measurement

P+ (0.6um)

N+ (1.0um)

currentHigh Energy

Particle

Insulator : (1,1,1) 5 kΩ N-typebias

voltage

Al

SiO2

•PIN diode operating at full depletion condition•Produced from wafers of 380 um, 5”, double polished

Ni

82MeV

Maximum signal (for 300 um thickness Si) 82 MeV / 3.62 eV ~ 2107 holes ~> 3.20 pC

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• CREAM is balloon borne experiment to measure cosmic composition in 1012 -1015 eV (highest possible energy range for a direct measurement)

• Sensors are installed on top of the calorimeter and target

• Back-scattered particles are produced in the high energy shower

• Pixel size is to be optimized for the performance : 15*14 mm2 for CREAM

Pixel Size of Sensors

• Area to cover ~ 79 × 79 cm3

• Number of channel ~ 3000 for a layer -> 180 sensors

Charge detector

Calorimeter

Charge Detector

Trigger Detector

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Wire (wedge) bonding for connection ofKapton cable to sensor pixel

Wedge bonding Al wire with diameter 50 um

Glob Topfor protection and preservation of bond wire

Coating SJC Polychemicals, DCE, DP100

Fabricated sensor Wafer size : 5 inch thickness: 380 umPixel size : 1.55 × 1.37 cm2

Array : 4 × 4 matrix

Sawing / attach Kapton tape for connection to readout

Kapton tape Cu wire with width 50 um

Fabricated by SENS Technology (www.senstechnology.co.kr)

Sensor Fabrication

Clean wafer

Oxidation

Cover with photoresist

Expose through maskDevelop

Etch, Stip

N+Diffusion

P+ ImplantationAnnealMetallization

Fabrication process

PIN diode structure

CV

0.00E+00

2.00E+17

4.00E+17

6.00E+17

8.00E+17

1.00E+18

1.20E+18

10 20 30 40 50 60 70 80 90 100

110

120

130

140

150

160

Reverse bias voltage (V)

Capa

citan

ce(F

)

ED3_10_all

ED3_11_all

ED3_12_all

ED3_13_all

ED3_14_all

ED3_17_all

ED3_19_all

ED3_2_all

ED3_20_all

IV

1.00E- 10

1.00E- 09

1.00E- 08

1.00E- 07

10 20 30 40 50 60 70 80 90 100

110

120

130

140

150

160

Reverse bias voltage(V)Le

akag

e cu

rrent

(A)

ED2_4_1

ED2_4_2

ED2_4_3

ED2_4_4

ED2_4_5

ED2_4_6

ED2_4_7

ED2_4_8

ED2_4_9

ED2_4_10

ED2_4_11

ED2_4_12

ED2_4_13

ED2_4_14

ED2_4_15

ED2_4_16

full depletion at ~ 80V Operation bias at 100V (over depletion) to make sure all sensors are fully depleted.

• For most sensors leakage current below 10 nA/cm2 at full depletion voltage

1/C2

Capacitance Measurement

Sensor Performance

ILeakage Measurement

~300 sensors for CREAM-1 (2003)~400 sensors for CREAM-2 (2005)

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Quality of Sensors

Sensors are biased at 100V (Over-depletion Voltage) to make sure that all sensors are fully depleted with the variation in the thickness and resistivity

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Frontend readout chip : CR1.4

CR1.4 ASIC–Custom VLSI (Very Large Scale Integrated circuit) chip –Developed for large arrays of silicon detectors in the Pamela experiment–16 channels of charge inputs (integrating the charge pulses -> DC levels)–Multiplexed to common output line –Dynamic range : a few fC to about 9 pC with 1 mV/fC Gain, 1200 MIP–Power consumption : ≤ 6 mW/channel, ≤ 100 mW/chip–Noise ~ 5000 e-

MUX

V to C

CSA

Cf

AdjustableReset

AdjustableMOS Resister

Cfs

Cc Ct/ h

SelfTrigger

Gain

OutputBuffer

CalibrationMUX

SAT/ H

VCOR

F53

OUT33

IN611

VB1

63

CLKS

ROU

T28

DATA

SRI

N18

VB2

60

IN116

NC32

RESVC245

IN314

IN134

RBSR

IN21

CSSR

IN19

IBC

SA62

REFG240

GNDA

55IN15

2

IN89

THIN

226

IBSELF47

VSS5

757

REFG1038

IN107

OUTT

H16

50

IBOUT35

GNDD

24

RBSR

OUT

27

OUTC

SA16

52

GSEL37

IN125

IN512

CSSR

OUT

29

Q16S

ROU

T31

NC39

VBFR

ES64

IN710

CAL

17

IBTH

54

IN215

IBTE

ST

49

NC34

IBS

HAP

59

IBCOMP44

VDDD

22

OUTSELF46

VBFC

61

IN143

CLKS

RIN

20

PDC42

OUTTRIG41

VDDA

56IN16

1VS

S23

23

IN98

NC58

THIN

125

NC48

REFCOMP43

OUTS

HAP

1651

RDCON36

IN116

IN413

DSRO

UT30

16 pixels

ADC

CR1.4

1 analog board = 7 CR1.4 * 16 channels = 112 channels

Analog Electronics (Frontend Readout)

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– Total 4864 channels, 304 sensors– Sensitive area 779*795 cm2, No dead area between sensors– Consume power of 136W, Total 56kg, total height 100mm

Silicon charge detector used in the second flight

(2006.01, 28 days, Antarctica)

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SCD Assembly

Mounting the assembled ladder Assembled SCD (1 layer)

SCD mechanical structure SCD cover

No damaged sensor was found after 28 days flight and parachute landing

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Thermal solution

SCD radiator (sun-side) SCD radiator (anti sun-side)

sensors

Analog board

Thermal strap (aluminum 2mm)

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Flight Monitoring

Temperature was maintained below 37’C

Pedestal runs were taken every 5 min. for offline correction

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Channel Performance

95% of channels performed very well to see MIP.Rest 3.5% are good for high z events analysis.

(Proton signal is ~20 Counts above pedestal)

ADC counts Pixels in x axisPix

els

in

y a

xis

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Calibration Data and Channel Uniformity

• Helium events were taken with special trigger for calibration• Each sensor signal is well fit to Landau curveDistribution of Peak value of fit curve.

RMS ~ 0.023 * Z

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Charge Spectrum in the Flight Data

Clean signals up to FeCorrelation between signals from top and bottom layers(Data are not corrected for detector acceptance)

p

He

C

O

Ne

Mg Si

Very Preliminary

Very Preliminary

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Dean Karlen, LCWS 2002

2confusion

2neut.had.

2photons

2charged

2jet

had. neut.photonschargedjet

EEEE

EEEE

For ILC Jets, about 26 GeV of photons have ECAL showers closer than 2.5 cm fr

om a charged track

Segmentation in Silicon sensors ~ 10 mm

Silicon-W imaging calorimeter for ILC

Tungsten : small Moliere radiusThin active layer with silicon

Sharp single particle shower

Single particle showers from photons, neutral hadrons have to be well separated in a jet.

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thickness : 3.5 mm (= 1 X0)Size 65.5 mm X 57.5 mm ( ~ sensor size)

Test module Assembly

Tungsten

Aluminum Support of a Layer

Frontend boardMount holes

Test Module : 20 layers stacked

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Thickness of an Assembled Layer

Connector 2.7 mm Capacitor 1.4 mmPcb 1.7 mm Resistor 0.65 mmDiode 1.15 mm CR 1.4 chip 2.45 mmShielding board 1mm

Tungsten 3.5 mm

Aluminum 1.5 mmSensor and Readout 10 mm

15 mm

1mm inactive gap between sensors

131mm X 115mm Frontend Board

Silicon Sensor 32 pixels

in a layer

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Beam Direction

Layers of Si sensorsand Tungstens

Frontend readout boards

Digitaland ControlBoards

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Test Module Setup

Geometry• Total 20 layers = 20X with uniform layer thickness• Shower sampling at 19 layers with 2 sensors each layer.• 1mm gap between sensors• Aligned beam center to the center of

a sensor

Effective RM :~ 45mm

from volume ration of material

131mm X 115mm -> insufficient transverse shower containment

1mm inactive gap

RM

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Channel Scan for MIP calibration

an example of a sensor with all good pixels

Scanned over all 640 channels with 100 GeV hadron Beam

(no tungsten)

Pedestal :Gaussian FitMean : 5206.9Sigma : 7.2

Signal :Landau FitPeak : 5243

ADC Counts

S/N = 5.2

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50 GeV Electron

50 GeV pion

150 GeV Muon

Total ADC of an event / 640

First Analysis : sum ADC counts of all channels

No rejection of dead, noisy channels, No gain calibration applied

Detector Response to Different Particles

Online Shower Profile Monitor Pedestal subtracted

Random Trigger events (total pedestal)

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Detector Response to Different e- Energy Shower

Total ADC of an event / 640

150 GeV

100 GeV

80 GeV

50 GeV

30 GeV

20 GeV

10 GeV

Readout Pedestals from Random Trigger

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Energy Resolution

Electron Energy in GeV

dE /

E (%

)

Preliminary

Fit curve of 29%/√E

Geant4 simulation of this setup taking into account only shower leakage gives 18%/√E.

The effect of bad channels, gain calibration, and beam spread are not included here.

Working on further analysis

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Silicon thickness : 525 micronSize : Matrix of 6x6 pads, each pad have ~1cm2

Nominal Bias 200V, leakage @ 200 V < 300 nA for the full matrixWafers passivation for electrical contact with the glue EPOTEK E4-110 polytec (conductive glue with silver)

New Silicon Sensors for ILC Si-W calorimeter (CALICE)

5” wafer

6*6 pixels

pad~1x1cm2

62mm

62mm

CALICE main pattern

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Summary

• Design and production of a large number of silicon pixel sensors (more than 800) has been done.

• The sensor is 4*4 PIN diode array surrounded by 3 guard rings with each pixel size of 15*13 mm2, fabricated from 380 um high resistivity wafer.

• Most pixels have a low and stable level of leakage current (Id <10nA/cm2) at the operational bias of 100V.

• Sensors showed excellent performance in charge measurement of high-energy cosmic rays in balloon-borne experiment.

• The same sensors were successfully tested in high energy beam test for Si-W imaging calorimeter R&D.