A MAPS-based readout for a Tera-Pixel electromagnetic ... MAPS-based readout for a Tera-Pixel electromagnetic calorimeter at the ILC Marcel Stanitzki STFC-Rutherford Appleton Laboratory

A MAPS-based readout for a A MAPS-based readout for a Tera-Pixel Tera-Pixel

electromagnetic calorimeter electromagnetic calorimeter at the ILC at the ILC

Marcel StanitzkiMarcel StanitzkiSTFC-Rutherford Appleton LaboratorySTFC-Rutherford Appleton Laboratory

Y. Mikami, O. Miller, V. Rajovic, N.K. Watson, J.A. WilsonUniversity of Birmingham

J.A. Ballin, P.D. Dauncey, A.-M. Magnan, M. NoyImperial College London

J.P. Crooks, B. Levin, M.Lynch M. Stanitzki, K.D. Stefanov, R. Turchetta, M. Tyndel, E.G. VillaniSTFC-Rutherford Appleton Laboratory

Marcel Stanitzki2

The ILC

ILC calorimetry focused on Particle Flow Approach (PFA)

− Requirement of highly granular calorimeters

− Goal : Jet Energy resolution ~ 30 % /√E

ILC environment is very different compared to LHC

− Bunch spacing of ~ 300 ns (baseline)

− 2625 bunches in 1ms

− 199 ms quiet time

Occupancy dominated by beam background & noise

2625

Marcel Stanitzki3

What are Particle Flow Algorithms (PFA)?

Calorimeter Clustering

Match Tracks with Calorimeter Clusters

Remove Photon Calorimeter Clusters

Track reconstruction

RemainingEM-only Calorimeter Clusters

RemainingCalorimeter Clusters

Remove associated Calorimeter Clusters

DONE

Charged particles

Neutral Hadrons

Photons

Marcel Stanitzki4

SiW EM Calorimetry The baseline for the SiD &

ILD detector concepts

Sampling Calorimeter

− Silicon sensors embedded in tungsten sheets

− 30 layers

− 1.3 - 1.7 meters radius

1300- 2000 m2 silicon area

Analog read out (4x4-5x5 mm pixels)

Compact, has to fit inside the coil

ECALMODULE

COIL

HCAL

Marcel Stanitzki5

Increasing the granularity

PFA based on

− track-shower matching

− clear shower separation

Granularity of 5x5 mm may not be sufficient for

− e.g. π0 identification from τ decays

− shower separation in dense jets

Digital Pixels with 50x50 microns

− basically a Particle Counter

− requires highly integrated sensor

− ideal for MAPS-> TPAC design

− but 1 TeraPixel system ...τ decay

Marcel Stanitzki6

TPAC Sensor requirements

Sensitive to MIP signal

Pixels determine “hit” status (binary readout)

Store bunch crossing number & location of “hits”

Target noise rate 10-6 per Bunch crossing

Design to buffer data for up to 8192 bunch crossings

Readout in quiet time

Masking & trimming individual pixels

Minimize “dead space”

Marcel Stanitzki7

The INMAPS process

• Additional module: Deep P-Well– Developed specifically for this

project– Added beneath all active circuits

in the pixel– Should reflect charge,

preventing unwanted loss in charge collection efficiency

• Device simulations using TCAD– confirm shielding effect

• Test chip processing variants– TPAC 1.0 manufactured

with/without deep p-well for comparison

• Standard 0.18 micron CMOSUsed in the TPAC 1.0 sensor• 6 metal layers• Analog & Digital @ 1.8 V & 3.3 V• 12 micron epitaxial layer

Marcel Stanitzki8

The TPAC 1.0 Sensor

• 8.2 million transistors• 28224 pixels (168 x 168) ; 50

microns; 4 variants• Main variants

– PreShaper and PreSampler• Minor variants

– Capacitor variants• Sensitive area 79.4 mm2

− of which 11.1% “dead” (logic)

• Four columns of logic + SRAM– Logic columns serve 42 pixels– Record hit locations &

timestamps– Local SRAM

• Data readout– Slow (<5Mhz)– 30 bit parallel data output

Pre

Sha

per

Pre

Sam

pler0

1

2

3

Marcel Stanitzki9

TPAC Architecture Details

Deep p-well

Circuit N-Wells

Diodes

The two main variants − PreSampler problematic

in array

− only the PreShaper worked well in the array

PreShaper− 4 diodes − 1 resistor (4 MΩ)− Configuration SRAM & Mask− Comparator trim (4 bits)

Two PreShaper variants − subtle changes to capacitors

Predicted Performance− Gain 94 μV/e− Noise 23 e-

− Power 8.9 μW

Marcel Stanitzki10

Sensor testing

quad0

quad1

Test pixels• preSample pixel variant• Analog output nodes• IR laser stimulus (1064 nm)• 55Fe stimulus

Single pixel in array● preShape (quad0/1)● Per pixel masks● IR Laser Stimulus (1064 nm)● 55Fe stimulus

Full pixel array• preShape (quad0/1)• Pedestals & trim adjustment• Gain uniformity• Crosstalk

Marcel Stanitzki11

Analog Test Pixel : Laser Using 1064 nm Laser

back-illuminate through substrate

2x2 μm spot, 2 μm steps

Take Profile through 2 diodes in test pixel

Marcel Stanitzki12

Analog Test Pixel: 55Fe

55Fe main decay

− 5.9 keV photon

All energy deposited in approx 1 μm3 silicon

− Generates 1640 e−

If a photon hits a diode

− no diffusion

Absolute Gain calibration

Marcel Stanitzki13

Array : Pixel Response to laser

Single active pixel with/without laser firing

Use same laser setup as for analog scans

Fire Laser at fixed point in pixel

Threshold Scan with and without Laser

Plateau due to memory saturation

Marcel Stanitzki14

Array : Single Pixel comparison

F

B

Pixel profiles

Amplitude results from Laser Scan

− With/without deep p-well

Compare

− Simulations “GDS”

− Measurements “Real”

Marcel Stanitzki15

Array: Single Pixel 55Fe response

use 55Fe source on Pixel Array

Do a threshold Scan

Need the derivative to reconstruct 55Fe peak

− Derivative approximated using bin subtraction

Single active pixel with/without source

Marcel Stanitzki16

Array: Pixel Noise Threshold scan required to see pedestal

and noise

Comparator fires on signal going high across threshold level

− No hits when far above or below threshold

− Width of distribution equivalent to noise

RMS ~ 5.5 Threshold Units (TU) ~ 44 e− ~ 170 eV on average

− Minimum is ~ 4 TU ~ 32 e− ~ 120 eV

− Target level was ~ 90 eV

− No correlation with position on sensor

− Spread not fully understood

− Quad1 ~ 20% larger than Quad0

Threshold

Marcel Stanitzki17

Array: Pedestal adjustments

Trimmed: Quad0; Quad1

Plot the distribution of pedestals

− Mean of Noise

Calculate necessary trim adjustment

− Per-pixel trim file

− uni-directional adjustment

Re-scan pixels with trims

− Re-plot the distribution of pedestals

Planned to have pedestal width ~ ½ Noise width

− have more trim bits

Trim=0: Quad0; Quad1

Mean (TU)

Mean (TU)

Marcel Stanitzki18

Array: Pixel Gain

Use laser to inject fixed-intensity signal into many pixels

Relative position should be equivalent for each pixel scanned

Adjust/trim for known pixel pedestals

Results

− Gain uniform to 12%

− Quad1 ~ 40% more gain than Quad0

− Quad1 ~ 20% better S/N than Quad0

GAIN Quad0; Quad1

Threshold

Marcel Stanitzki19

Array Pixel Cross-talk

Scan one pixel in the column, all others off.

scan entire pixel column

Effect of all pixels (other than the one being scanned) is to increase the general noise around zero.

Shared power mesh between comparator and and monostable prime culprit, will be fixed

Marcel Stanitzki20

Future Plans – TPAC 1.1

Have received TPAC1.1 a week ago

− Only one pixel variant (preShaper quad1)

− Upgrade trim adjustment from 4 bits to 6 bits

− Compatible format: size, pins, PCB/DAQ etc.

− Minor bugs fixed (e.g. cross-talk)

− Additional test pixels & devices for further process characterization

Marcel Stanitzki21

Conclusion

TPAC 1.0 has been a success

− See response to Laser, 55Fe

− Proved deep p-well approach for MAPS

− Only minor problems found

− Finishing characterization

TPAC 1.1

− will be evaluated in the upcoming months

We plan to make full-reticle size sensor after that

− 2.5 x 2.5 cm