W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 1

Fully Depleted Fully Depleted Monolithic Active Pixel Monolithic Active Pixel

Sensor in SOI Sensor in SOI Technology Technology

Fully Depleted Fully Depleted Monolithic Active Pixel Monolithic Active Pixel

Sensor in SOI Sensor in SOI Technology Technology

PresentedPresented by byWojciech KucewiczWojciech Kucewiczaa

on behalf of on behalf of A.BulgheroniA.Bulgheronibb, M. Caccia, M. Cacciabb, K. Domanski, K. Domanskicc, P. Grabiec, P. Grabieccc, M. Grodner, M. Grodnercc, ,

B. JaroszewiczB. Jaroszewiczcc, M. Jastrzab, M. Jastrzabaa, A. Kociubinski, A. Kociubinskicc,, M. Kozioł, M. Kozioł, K. Kucharski K. Kucharskicc, , S.KutaS.Kutaaa, J. Marczewski, J. Marczewskicc, H. Niemiec, H. Niemiecaa, M. Sapor, M. Saporaa, D. Tomaszewski, D. Tomaszewskicc

a AGH-Univ. of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow, Poland

b Università dell’Insubria, via Valleggio 11, 22100 Como, Italyc Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw, Poland

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 2

OutlineOutlineOutlineOutline

Principle of the SOI sensorPrinciple of the SOI sensor

Preliminary test of the small area SOI Preliminary test of the small area SOI sensors on the high resistive substratessensors on the high resistive substrates

Design of the full size SOI sensor – Design of the full size SOI sensor – layout and readout schemelayout and readout scheme

The SOI project is partially supported The SOI project is partially supported bby y the G1RD-CT-2001-000561the G1RD-CT-2001-000561

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 3

Principle of SOI monolithic Principle of SOI monolithic detectordetector

Principle of SOI monolithic Principle of SOI monolithic detectordetector

The The wafer bondingwafer bonding technics was technics was choosen for SOI technologychoosen for SOI technologyLow resistivity

High resistivity

SI O2

SI O2

High resistivity

SI O2

Low resistivity

SI O2

High resistivity

SI O2

SI O2Thin low resistivity layer –Thin low resistivity layer – readout readout electronicselectronics circuit circuit

High resistivity support – sensitive areaHigh resistivity support – sensitive area

Termochemical bonding

1-1,5 1-1,5 mm

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 4

Principle of SOI monolithic Principle of SOI monolithic detector detector

Principle of SOI monolithic Principle of SOI monolithic detector detector

The idea:The idea: Integration of the pixel detector and readout electronics in the wafer-bonded SOI substrate

Electronics Electronics Device layer Low resistive

(9-13 cm, CZ) 1.5 m thick Standard CMOS technology

Detector Detector Support layer High resistive

(> 4 kcm,FZ) 300 m thick Conventional p+-n DC-coupled

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 5

MotivationMotivationMotivationMotivation

As a monolithic device eliminates bump-bonding process and allows As a monolithic device eliminates bump-bonding process and allows reduction of total sensor thickness reduction of total sensor thickness reduction of multiple reduction of multiple scatteringscattering

Allows using high resistive detector substrates and operation in fully Allows using high resistive detector substrates and operation in fully depleted region depleted region good detection efficiency, enables detection of good detection efficiency, enables detection of particles with limited range in the silicon without backthinning particles with limited range in the silicon without backthinning processprocess

Gives possibility to use both type of transistors in readout channels Gives possibility to use both type of transistors in readout channels increased flexibility of the design, design optimisation for different increased flexibility of the design, design optimisation for different applicationapplication

Advantages of Advantages of the the SOI detectors:SOI detectors:

The SOI sensor may merge the advantages of the The SOI sensor may merge the advantages of the monolithic and hybrid detectorsmonolithic and hybrid detectors

Advantages of Advantages of the the SOI detectors:SOI detectors:

The SOI sensor may merge the advantages of the The SOI sensor may merge the advantages of the monolithic and hybrid detectorsmonolithic and hybrid detectors

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 6

Test structures of the SOI Test structures of the SOI detectordetector

Test structures of the SOI Test structures of the SOI detectordetector

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 7

Test structures of the SOI Test structures of the SOI detectordetector

Test structures of the SOI Test structures of the SOI detectordetector

Small readout matrices (8x8) with associated detector diodes or input pads for external signal sources were fabricated on the SOI wafers at the IET, Warsaw

Two readout channel configurations – with NMOS transistor switch (cell dimensions 140x122 m2) and with transmission gate (140x140 m2)

Contact to the detector placed in the V-shape cavity.

Row selection signals led by two parallel lines with opposite polarization, body of the structure densely grounded reduction of the cross-talk between the electronics and detector

VDET

VSS

VDD

IN

RES

N_ROW_SEL

ROW_SEL

COL

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 8

DDetector etector RReadouteadoutDDetector etector RReadouteadout

Operation in un-triggered mode (for imaging applications) Analogue serial readout organisation Readout sequence similar to rolling-shutter but double sampling performed for every pixel External subtraction of samples for CDS Well defined integration time and short dead time Exercised and validated on the prototype chip designed in commercial AMS 0.8 technology

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Readout pixel

Ro

w_

sel s

hift

reg

iste

r an

d r

ese

t lo

gic

Analog Output

Column_sel shift register

Dummy pixel

Control block CLK RST

READ

Cu

rre

nt r

efe

ren

ce

Row_sel<0>

Column_sel<0>

Column_sel<1>

Column_sel<31>

Reset_rowl<0>

Row_sel<1>

Row_sel<31>

Reset_rowl<1>

Reset_rowl<31>

Sample I-after reset

Sample II-after integration time

Charge integration

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 9

SUCIMA Imager DAQ for the SOI SUCIMA Imager DAQ for the SOI DetectorDetector

SUCIMA Imager DAQ for the SOI SUCIMA Imager DAQ for the SOI DetectorDetector

The DAQ is equipped with 4 independent analogue 4 independent analogue inputinput channels channels with 12 bit ADCs, 1MB fast static RAM, the FPGA Virtex II XC2V1000 chip for advanced algorithms and the high speed USB 2.0 USB 2.0 portport for a fast data transfer to and from a PC computer.

GUI – developed in LabVIEW environment, allows setting: the matrix size to be readout, readout frequency;

It provides: the CDS or last frame readout mode, masking noisy pixels, subtracting pedestals, suppressing signals bellow threshold and writing data to the file.

VIRTEX IIXC2V1000

4FG456CES(324 I/O)

VIRTEX IIXC2V1000

4FG456CES(324 I/O)

40 MHz

BANK_7S

EN

SO

R

SUCIMA_IMAGER

BANK_2 BANK_3

BA

NK

_5B

AN

K_4

BANK_6

BA

NK

_0B

AN

K_1

SR

AM

2x2

56K

x16

B

SR

AM

2x2

56K

x16

B

US

B &

28

GP

IO p

ins

D32A18

D24

D16

.

JTA

G

A18

A18CLK

CTRL

328 USER’s I/O PADS

SE

NS

OR

’S R

EP

EA

TE

R

SR

AM

2x2

56K

x16

B

SR

AM

2x2

56K

x16

B XV18V04

EEPROM

DedicatedDedicated DAQ system called DAQ system called „SUCIMA imager”„SUCIMA imager” was was

developeddeveloped for the SUCIMA for the SUCIMA projectproject by INF in Cracow by INF in Cracow..

14 cm14 cm

9.5

cm

9.5

cm

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 10

Stand Alone DetectorStand Alone Detector Diodes and Diodes and Electronics withElectronics with Input PadsInput Pads

Stand Alone DetectorStand Alone Detector Diodes and Diodes and Electronics withElectronics with Input PadsInput Pads

Transfer characteristics were measured with external voltage pulse signal

with NMOS transistor switch Measured DC output dynamic range up

to 1.0 V with transmission gate

Measured DC output dynamic range up to 1.8 V non-linearity at the middle range was reduced in the latest designs

Readout ElectronicsReadout Electronics

1.0E-12

1.0E-11

1.0E-10

1.0E-09

0 10 20 30 40 50 60Detector bias [V]

Le

ak

ag

e c

urr

en

t [

A/m

m2 ]

e7 g8

1.0E-12

1.0E-11

1.0E-10

1.0E-09

0 10 20 30 40 50 60Detector bias [V]

Le

ak

ag

e c

urr

en

t [

A/m

m2 ]

e7 g8

Pixel leakage current: From 200 nA down to 10 nA per

cm2 depending on the process

Detector full depletion voltage: 60 V down to 50 V for different

iterations

Detector DiodesDetector Diodes

Comparison of transfer characteristics of readout matrices on SOI wafers

0.0E+00

5.0E+02

1.0E+03

1.5E+03

2.0E+03

0 20 40 60 80 100 120 140 160 180MIP

Vou

t [m

V]

one-transitor switch

switch in the form oftransmision gate

0 0.4 0.8 1.2 1.6 Vin 0 0.4 0.8 1.2 1.6 Vin [V][V]

Vout Vout

[V][V]

2.02.0

1.51.5

1.01.0

0.50.5

0.00.0

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 11

Tests Tests wwith the Laser Lightith the Laser LightTests Tests wwith the Laser Lightith the Laser Light

Laser light not focused, shining from the backplane (biased by a metal mash)

Wavelength = 850 nm 4 s wide light pulses – simulate

particles passing through detector active volume (each corresponding to 3.4 MIP)

Integration time = 1 ms Detector polarization=60V 10 000 events recorded and averaged Input signal scaled assuming the

sensor gain of 11mV/MIP

GGood detector sensitivity for the ionising radiation and ood detector sensitivity for the ionising radiation and linear response as a function of the generated charge was linear response as a function of the generated charge was

observedobserved..

Linearity of Sensor ResponseLinearity of Sensor Response

12

Tests with theTests with the 90 90 Sr Beta SourceSr Beta SourceTests with theTests with the 90 90 Sr Beta SourceSr Beta Source Sensor sensitivity tested with 90Sr beta

source Measurements conditions: complete

depletion (Vdet= 70 V), integration time: Tint = 720 s, source placed at the top of the sensor.

Detector output signal amplified (k2.5) before digitalisations

On-line CDS processing, off-line pedestal subtraction, common mode suppression and cluster search

Recorded EventRecorded EventRecorded EventRecorded Event Cluster SizeCluster SizeCluster SizeCluster Size

Gaussian distribution of the noise

Landau distribution of the measured

signals

The most probably value of signal per MIP: 27 ADC 27 ADC

Noise for the seed pixels: 1.5 to 2 ADC1.5 to 2 ADC

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 13

Tests with theTests with the Alpha Particles Alpha ParticlesTests with theTests with the Alpha Particles Alpha Particles

Alpha source placed at the distance of 1 cm from the detector backplane Initial energy of particles = 5.5 MeV Detector fully depleted (VD=70V), integration time 720 s On-line CDS processing, off-line pedestal subtraction, common mode suppression and

cluster search

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 14

Typical measured cluster pulse height cluster pulse height 200 ADC 200 ADC – corresponding to about half of the alpha particles initial energy.

Pedestal width – about 1.5 ADC1.5 ADC, S/N for cluster pulse height 130. Broad spectrum due to energy straggling in air.

Noise SpectrumNoise Spectrum Alpha SpectrumAlpha SpectrumCluster SizeCluster Size

Tests with theTests with the Alpha Particles Alpha ParticlesTests with theTests with the Alpha Particles Alpha Particles

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 15

Design of a full size detector Design of a full size detector layoutlayout

Design of a full size detector Design of a full size detector layoutlayout

Dimensions: 24x24 mm2

128 x 128 = 16 384 channels 4 sub-segments with independent parallel analogue outputs Cell dimensions: 150x150m2

Possibility to extend to ladders with dimensions up to 72x24 mm2 and small dead areas

Row

_sel

C o l _ s e l

A D C

1 0 . 2 4 m m 1 2 m m

< 0 - 6 3 >

<0-

63

> 1

0.2

4m

m

12

mm

A D C

A D CA D C

A D C A D C

A D CA D C

A D C

2 4 m m

24m

m

7 2 m m

24m

m

a ) b )

c)

Detector Detector cavitycavity

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 16

FFull size detectorull size detectorFFull size detectorull size detector

ADC

ADCADC

ADC ADC

ADCADC

ADC

24 mm

24m

m

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 17

„„Baby Detector” Baby Detector” – backup solution of the SOI – backup solution of the SOI

sensorsensor

„„Baby Detector” Baby Detector” – backup solution of the SOI – backup solution of the SOI

sensorsensor

Smaller number of the transistors, simpler functionality: Smaller number of the transistors, simpler functionality: 48 x 48 readout channels, area 1.2 cm x 1.2 cm, no digital control blocks

Reset and Column/Row selection signal must be generated externallyReset and Column/Row selection signal must be generated externally ( (NRow NRow and NColumn signals are generated internallyand NColumn signals are generated internally))

Configuration of the analogue blockConfiguration of the analogue block is is the same as on the main detector the same as on the main detector.. Two versions – with dashed guardring (like on the main chip) and continuous Two versions – with dashed guardring (like on the main chip) and continuous

guardring – reliability and effectiveness of both solutions will be compared.guardring – reliability and effectiveness of both solutions will be compared.

Dashed guardringDashed guardring Continuous guardringContinuous guardring

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 18

NewNew Test Structure Test StructureNewNew Test Structure Test Structure

Several units of the old test structure for the crosscheck of the parameters between different wafers

Several units with different transistor layouts for matching, noise and radiation hardness studies

Test structure for direct IV and CV characteristics measurements of the detector diodes

Small matrix of the sensor with modified readout configuration

New Test Structure exploits the experience gained with the old test

structure. It consists of:

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 19

NewNew Test Structure Test StructureNewNew Test Structure Test Structure Matrix of 16x16 readout channels with

reduced capacitance at the input node – higher signal per MIP

Readout electronics configuration the same like on the main sensor

Input (charge integrating) capacitance reduced by disconnecting the polySi plate covering pixel cavity from the input and connection to the VSS (in case of the short between input and polySi layer no negative influence of the faulty pixel on the neighbours performance).

Estimated pixel contact capacitance: Cpixcon 27 fF, estimated total input capacitance: Ctot 190 fF signal per MIP: S 14 15 mV

This circuit was also placed separately (outside Test Structure chip) at several localization on the wafer – another backup solution in case of the problems with the big detectors.

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 20

NewNew Test Structure Test StructureNewNew Test Structure Test Structure Matrix of Matrix of 8x168x16 readout channels with readout channels with the the

conventional conventional CSA CSA configurationconfiguration

8x8 channels with the standard contact and 8x8 with the reduced input capacitance

Charge integration mode – controlled by RES signal Global reset and sampling&hold Signal: 140 mV/MIP, lower noise. Weak DC feedback loop – stabilize the operation

point of the input transistor – no protection diode required

Partial leakage current compensation is possible by adjustment of the PBF – may operate for leakage current of the order of 10nA/cm2 up to 100 nA/cm2

Auto-polarization of the feedback transistor Single cell dimensions: 329 m x 357 m Much more sensitive for the device characteristics

changes than the 3T cell

VX VX

IN

VDD VDD

PB2

PB1

VSS

RES

VDD

OUT

PB2

PBF

VSS

W.Kucewicz 2004 Nuclear Science Symposium, Rome, October 16-22, 2004 21

SummarySummarySummarySummary An alternative solution of a monolithic active pixel detector, which allows An alternative solution of a monolithic active pixel detector, which allows

efficient detection in high resistive substrate, has been proposed.efficient detection in high resistive substrate, has been proposed. First small area SOI pixel sensors have been fabricated.First small area SOI pixel sensors have been fabricated. The tests The tests results proveresults prove::

sensitivity of the test matrices for the MIP signals (measurements with 90Sr),

wide dynamic range (measurements with laser spot and alpha particles),

detector suitability for the detection of particles with limited range in silicon (measurements with alpha particles),

effectiveness of the charge integration mechanism implemented in the readout circuit.

Following the positive results of the tests of the small area SOI sensors a Following the positive results of the tests of the small area SOI sensors a larger and fully functional SOI sensor (128x128 readout channels, active larger and fully functional SOI sensor (128x128 readout channels, active area of 2 cm x 2 cm, optimised for medical imaging applications) have area of 2 cm x 2 cm, optimised for medical imaging applications) have been designed and produced. been designed and produced.