Monolithic and Vertically Integrated Pixel Detectors, CERN, 25 th November 2008 CMOS Monolithic Active Pixel Sensors R. Turchetta CMOS Sensor Design Group Rutherford Appleton Laboratory, Oxfordshire, UK

2  CMOS Image RAL  The INMAPS process and its silicon proof  Conclusions Outline

Overall view CMOS image sensor activity started in 1998 (aka Monolithic Active Pixel Sensor; MAPS) 1 st tape-out in 2000: test structures for the Star-Tracker in 0.5 and 0.7  m 1 st full-scale sensor submitted in May 2001: the Star-Tracker in 0.5  m Use of technologies down to 0.18  m Use of CIS (CMOS Image Sensors) technologies Patented, silicon-proofed INMAPS technology for high-end sensors Pixel size from 2  m upwards Large pixels IPs 4T pixel Ips Low noise pixel IPs Wafer-scale (200mm) sensor capability Over 40 years of cumulated design experience 3

The Large Area Sensor (LAS) Sensors of different sizes on the same 200mm wafer 0.35  m CMOS Basic unit 270x270 pixels X5  1350x1350 X2  540x540 X1  270x270 Wafer-scale possible 4

Region of Reset readout No ROR Image of a laser point ROR readout T int0 = 80, T int1 = 30, T int2 = 1 >140dB 5

6 NMOS P-Well N-Well P-Well N+ P-substrate (~100s  m thick) N+ N-Well P+ Diode NMOS PMOS 100 % efficiency  only NMOS in pixel  no complicated electronics Complicated electronics  NMOS and PMOS,i.e. CMOS  low efficiency How much CMOS in a CMOS sensor?

NMOS P-Well N-Well P-Well N+ P-substrate (~100s  m thick) N+ N-Well P+ Diode NMOS PMOS The INMAPS process Deep P-Well Standard CMOS with additional deep P-well implant. Quadruple well technology. 100% efficiency and CMOS electronics in the pixel. Optimise charge collection and readout electronics separately! Proved on 0.18  m 7 metal layers Analog & 1.8v & 3.3v Choice of epi layers (5 and 12  m tested so far) 7

8 INMAPS Proof of principle Alternative to CALICE Si/W analogue ECAL No specific detector concept “Swap-in” solution leaving mechanical design unchanged Tungsten 1.4 mm PCB ~0.8 mm Embedded VFE ASIC Silicon sensor 0.3mm Diode pad calorimeter MAPS calorimeter

preShape Gain 94uV/e Noise 23e- Power 8.9uW 150ns “hit” pulse wired to row logic Shaped pulses return to baseline Pixel Architectures preSample Gain 440uV/e Noise 22e- Power 9.7uW 150ns “hit” pulse wired to row logic Per-pixel self- reset logic 9 9

preShape Pixel 4 diodes 160 transistors 27 unit capacitors 1 resistor (4Mohm) Configuration SRAM –Mask –Comparator trim (4 bits) 2 variants: subtle changes to capacitors Pixel Layouts preSample Pixel 4 diodes 189 transistors 34 unit capacitors Configuration SRAM –Mask –Comparator trim (4 bits) 2 variants: subtle changes to capacitors 10 Deep p-well Circuit N-Wells Diodes 10

8.2 million transistors pixels; 50 microns; 4 variants Sensitive area 79.4mm2 –of which 11.1% “dead” (logic) Test Chip Architecture Four columns of logic + SRAM –Logic columns serve 42 pixels –Record hit locations & timestamps –Local SRAM Data readout –Slow (<5Mhz) –Current sense amplifiers –Column multiplex –30 bit parallel data output 11

Sensor Testing: Overview Test pixels preSample pixel variant Analog output nodes Fe55 stimulus IR laser stimulus Single pixel in array Per pixel masks Fe55 stimulus Laser Stimulus Full pixel array preShape (quad0/1) Pedestals & trim adjustment Gain uniformity Crosstalk Beam test quad0 quad1 12

Charge collection Amplitude results With/without deep pwell Compare Simulations “GDS” Measurements “Real” (pixels with full electronics) F B Pixel profiles 13

55 Fe Source 55 Fe gives 5.9keV photon Deposits all energy in “point” in silicon; 1640e − Sometimes will deposit maximum energy in a single diode and no charge will diffuse  absolute calibration! Binary readout from pixel array Need to differentiate distribution to get signal peak in threshold units (TU) Differential approximation 14

15 CMOS Active Pixel Sensors are mature for high-end applications Cost-effective solution for large-scale experiments Low noise (< 10 e- rms) Large area: up to 200mm wafer-scale INMAPS process allows complex in-pixel architectures without degrading the detection performance Evaluating possibility of offering access to the INMAPS process to the community Conclusions

Acknowledgements For the Large Area Sensor (work carried out under the MI-3 Multidimensional Integrated Intelligent Imaging Consortium) A.T. Clark, N. Guerrini, J.P. Crooks, T. Pickering (Rutherford Appleton Laboratory) N. Allinson (University of Sheffield) S.E. Bohndiek (University College London) For the CALICE-MAPS: J.P. Crooks, R. Coath, M. Stanitzki, K.D. Stefanov, M. Tyndel, E.G. Villani (Rutherford Appleton Laboratory) J.A. Ballin, P.D.Dauncey, A.-M. Magnan, M. Noy (Imperial College London) Y. Mikami, N.K. Watson, O. Miller, V. Rajovic, J.A. Wilson (University of Birmingham) 16