LCFI Status Report: Sensors for the ILC Konstantin Stefanov CCLRC Rutherford Appleton Laboratory

1. LCFI Status Report: Sensors for the ILC • Konstantin Stefanov • CCLRC Rutherford Appleton Laboratory • ILC Vertex Detector Workshop, Ringberg 2006 • Introduction • Sensor Development for the ILC • Column-Parallel CCDs • In-situ Storage Image Sensors • Summary and Plans

2. Introduction and Conceptual Design Beam bunch structure at ILC 337 ns 0.2 s 2820x 0.95 ms Multiple collisions 120 large sensors (e.g. CCDs) in 5 layers, 800 Mpixels (20 μm20 μm) Main vertex detector parameters: • Excellent point resolution (3.5 μm), pixel size =20 μm, close to IP • Low material budget ( ~ 0.1% X0 per layer), low power dissipation • Readout: • Avoids excessive event overlap, occupancy << 1% • Inner layer effectively read out at 50 μs intervals during the 1 ms pulse train (20 readouts) – information may leave the sensor or be stored in pixel • Outer layers read out at 250 μs intervals • Moderate radiation hardness: bulk damage from 61011 electrons/cm2/year and 109 neutrons/cm2/year, surface damage not expected to cause problems • Tolerates Electro-Magnetic Interference (EMI)

3. The Column Parallel CCD M M N N “Classic CCD” Readout time  NM/fout Column Parallel CCD Readout time = N/fout • Main detector work at LCFI • Every column has its own amplifier and ADC – requires readout chip • Readout time shortened by orders of magnitude • All of the image area clocked, complicated by the large gate capacitance • Optimised for low voltage clocks to reduce power dissipation

4. CPC1 Bump-bonded to CPR1 Hybrid assembly with Column-Parallel CCD (CPCCD) and CMOS ASIC • CPC1 : Two phase CCD, 400 (V)  750 (H) pixels, 20 μm square; • CMOS readout chip (CPR1) designed by the Microelectronics Group at RAL: • 0.25 μm process • Charge and voltage amplifiers matching the outputs of CPC1 • Correlated double sampling • 5-bit flash ADCs and 132-deep FIFO per column • Everything on 20 μm pitch • Size : 6 mm 6.5 mm • Manufactured by IBM • Bump-bonded by VTT (Finland) using solder bumps Bump-bonded CPC1/CPR1 in a test PCB

5. CPC1/CPR1 Performance 5.9 keV X-ray hits, 1 MHz column-parallel readout Voltage outputs, non-inverting (negative signals) Noise 60 e- Charge outputs, inverting (positive signals) Noise 100 e- • First time e2V CCDs have been bump-bonded • High quality bumps, but assembly yield only 30% : mechanical damage during compression suspected • Differential non-linearity in ADCs (100 mV full scale) : addressed in CPR2 Bump bonds on CPC1 under microscope

6. Next Generation CPCCD Readout Chip – CPR2 Voltage and charge amplifiers 125 channels each Analogue test I/O Digital test I/O 5-bit flash ADCs on 20 μm pitch Cluster finding logic (22 kernel) Sparse readout circuitry FIFO Bump bond pads CPR1 CPR2 • CPR2 designed for CPC2 • Results from CPR1 taken into account • Numerous test features • Size : 6 mm 9.5 mm • 0.25 μm CMOS process (IBM) • Manufactured and delivered February 2005 Wire/Bump bond pads Steve Thomas, RAL

7. CPR2 Test Results Sparsified output Test clusters in • Parallel cluster finder with 22 kernel • Global threshold • Upon exceeding the threshold, 49 pixels around the cluster are flagged for readout • Tests on the cluster finder: works! • Several minor problems, but chip is usable • Design occupancy is 1% • Cluster separation studies: • Errors as the distance between the clusters decreases • Reveal dead time • Many of the findings have already been input into the CPR2A design Tim Woolliscroft, Liverpool U Tim Woolliscroft, Liverpool U

8. Next Generation CPCCD : CPC2 No connections this side Clock bus Charge injection Extra pads for clock monitoring and drive every 6.5 mm Image area Four 2-stage SF in adjacent columns Standard Field-enhanced Standard Temperature diode on CCD Four 1-stage and 2-stage SF in adjacent columns Main clock wire bonds Main clock wire bonds CPR1 CPR2 • Three different chip sizes with common design: • CPC2-70 : 92 mm  15 mm image area • CPC2-40 : 53 mm long • CPC2-10 : 13 mm long • Compatible with CPR1 and CPR2 • Two charge transport sections • Choice of epitaxial layers for different depletion depth: 100 .cm (25 μm thick) and 1.5 k.cm (50 μm thick) • Baseline design allows few MHz operation for the largest size CPC2

9. CPC2 + ISIS1 Wafer ISIS1 • 5” wafers • One CPC2-70 : 105 mm  17 mm total chip size • Two CPC2-40 per wafer • 6 CPC2-10 per wafer • 14 In-situ Storage Image Sensors (ISIS1) • 3 wafers delivered CPC2-70 CPC2-40 CPC2-10

10. CPC2-40 in MB4.0 Transformer CPR1/CPR2 pads Clock monitor pads Johan Fopma, Oxford U • Transformer drive for CPC2 • “Busline-free” CCD: the whole image area serves as a distributed busline • 50 MHz achievable with suitable driver in CPC2-10 and CPC2-40 (L1 device) • First clocking tests have been done

11. Transformer Drive for CPC2 • Requirements: 2 Vpk-pk at 50 MHz over 40 nF (half CPC2-40); • Planar air core transformers on 10-layer PCB, 1 cm square • Operation from 1 MHz to > 70 MHz unloaded; • Parasitic inductance of bond wires is a major effect – fully simulated; • Work on the reduction of the CCD capacitance and clock voltage is continuing – range of test devices under development. Brian Hawes, Oxford U • Transformer is bulky; • IC driver could be a better solution; • Design of the first CPCCD driver chip (CPD1) has started, goes for manufacture end of June • CPD1: 2-phase CMOS driver chip for 20 Amp current load at 25 MHz (L2-L5 CCDs) • 0.35 μm process, size 38 mm2

12. First Data from CPC2 • CPC2-10 (low speed version) works fine, here at 1 MHz clock • 55Fe spectrum at -40 C and 500 ms integration time • Noise is a bit too high, external electronics is suspected • Devices with double level metal (busline-free for high speed) are being manufactured now

13. Radiation Damage Effects in CCDs: Simulations Simulation at 50 MHz Operating window Signal density of trapped electrons in 2D • Full 2D simulation based on ISE-TCAD developed • Trapped signal electrons can be counted • CPU-intensive and time consuming • Simpler analytical model also used, compares well with the full simulation • Window of low Charge Transfer Inefficiency (CTI) between -40 C and 0 C • This is very important for the viability of the CCD optionand should be verified experimentally L. Dehimi, K. Bekhouche (Biskra U); G. Davies, C. Bowdery, A.Sopczak (Lancaster U)

14. In-situ Storage Image Sensor (ISIS) • Beam-related RF pickup is a concern for all sensors converting charge into voltage during the bunch train; • The In-situ Storage Image Sensor (ISIS) eliminates this source of EMI: • Charge collected under a photogate; • Charge is transferred to 20-pixel storage CCD in situ, 20 times during the 1 ms-long train; • Conversion to voltage and readout in the 200 ms-long quiet period after the train, RF pickup is avoided; • 1 MHz column-parallel readout is sufficient;

15. In-situ Storage Image Sensor (ISIS) 5 μm Global Photogate and Transfer gate ROW 1: CCD clocks • Additional ISIS advantages: • ~100 times more radiation hard than CCDs – less charge transfers • Easier to drive because of the low clock frequency: 20 kHz during capture, 1 MHz during readout • ISIS combines CCDs, active pixel transistors and edge electronics in one device: specialised process • Development and design of ISIS is more ambitious goal than CPCCD • “Proof of principle” device (ISIS1) designed and manufactured by e2V Technologies ROW 2: CCD clocks On-chip switches On-chip logic ROW 3: CCD clocks ROW 1: RSEL Global RG, RD, OD RG RD OD RSEL Column transistor

16. The ISIS1 Cell • 1616 array of ISIS cells with 5-pixel buried channel CCD storage register each; • Cell pitch 40 μm  160 μm, no edge logic (pure CCD process) • Chip size  6.5 mm  6.5 mm Output and reset transistors OG RG OD RSEL Column transistor OUT Photogate aperture (8 μm square) CCD (56.75 μm pixels)

17. Tests of ISIS1 Tests with 55Fe source • The top row and 2 side columns are not protected and collect diffusing charge • The bottom row is protected by the output circuitry • ISIS1 without p-well tested first and works OK • ISIS1 with p-well has very large transistor thresholds, permanently off

18. Conclusion and Plans • CPCCD program well advanced: • Main work at LCFI • Hybrid assembly with CPCCD and CMOS chips works OK • Detector-sized chips CPC2 have arrived, first tests have been done • Started to develop the challenging CPCCD drive system • ISIS work will continue: • First ISIS prototype on CCD technology manufactured, first tests promising • Next-generation small pixel ISIS (CCD- or CMOS-based) will be actively pursued Immediate plans: • Evaluate CPC2 and CPC2/CPR2 bump-bonded • High speed external drive to CPC2-40 as demonstrator for the L1 vertex detector Visit us at http://hepwww.rl.ac.uk/lcfi/