A MAPS-based readout for a Tera-Pixel electromagnetic calorimeter at the ILC Marcel Stanitzki STFC-Rutherford Appleton Laboratory Y. Mikami, O. Miller, V. Rajovic, N.K. Watson, J.A. Wilson University of Birmingham J.A. Ballin, P.D. Dauncey, A.-M. Magnan, M. Noy Imperial College London J.P. Crooks, B. Levin, M.Lynch M. Stanitzki, K.D. Stefanov, R. Turchetta, M. Tyndel, E.G. Villani STFC-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 Remaining EM-only Calorimeter Clusters Remaining Calorimeter 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  meters radius m 2 silicon area Analog read out (4x4-5x5 mm pixels) ‏ Compact, has to fit inside the coil ECAL MODULE 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. π 0 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 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 CMOS Used in the TPAC 1.0 sensor 6 metal layers Analog & 1.8 V & 3.3 V 12 micron epitaxial layer

Marcel Stanitzki8 The TPAC 1.0 Sensor 8.2 million transistors pixels (168 x 168) ; 50 microns; 4 variants Main variants – PreShaper and PreSampler Minor variants – Capacitor variants Sensitive area 79.4 mm 2  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 PreShaper PreSampler

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) ‏ 55 Fe stimulus Single pixel in array preShape (quad0/1) ‏ Per pixel masks IR Laser Stimulus (1064 nm) ‏ 55 Fe 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: 55 Fe 55 Fe main decay  5.9 keV photon All energy deposited in approx 1 μm 3 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 55 Fe response use 55 Fe source on Pixel Array Do a threshold Scan Need the derivative to reconstruct 55 Fe 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)‏

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, 55 Fe  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