DEPFET Pixel: A Pixel Device with Integrated Amplification Johannes - PowerPoint PPT Presentation

Pixel 2000 Conference Genova, 4.6.-8.6. 2000 DEPFET Pixel: A Pixel Device with Integrated Amplification Johannes Ulrici Bonn University FAUST Semiconductor Lab

Outline • The DEPFET-Principle • Measurements on DEPFET Single Pixel Devices • First Measurements with a DEPFET Pixel Array (64x64) (Applications: Autoradiography, High Energy Physics, X-Ray Astronomy) • Summary In cooperation with the MPI semiconductor Lab Munich, Bochum University, Dortmund University, funded by the DFG and by the NRW department of Science

DEPFET - principle idea Preamplifier Kemmer, Lutz (1987): p n+ (p-JFET) • integrate preamplifier into S G D n+ Sensor Si- Substrate Advantage: n Sensor p+ Diode Integration of JFET • Small input capacitance • no stray capacitance S G D n+ p n+ => Large Signal to Noise internal gate n Ratio DEPFET p+

DEPFET - charge collection Ionising particle source top gate drain bulk potential via axis top-gate / rear contact n+ p+ p+ n+ ~1 µ m p-channel - - - - n internal gate + - - + ~300 µ m potential minimum - for electrons totally depleted + + n - -substrate - p+ rear contact V • sidewards depletion • electrons collected in internal gate • channel current of JFET modulated by signal charges

DEPFET - Clear Mechanism • Internal gate filled by +15V signal charges and 0V 0V source top gate drain clear bulk thermally generated electrons n+ p+ p+ n+ n+ p - - n - - - - • „Reset“ needed symmetry axis internal gate • One possibility: pulsed clear! n - • Other clear mechanisms: cont. clear, gate clear, ... p+ rear contact pulsed clear: dead time less than 0,1% of measuring time

DEPFET - Measurements on Single Pixel Devices Spectrum of 55 Fe-Source: 350 55 Fe k α = 5,89 keV k α • At room temperature (300 K) 300 55 Fe k β = 6,49 keV • Shapingtime: 10µs 250 • Noise Peak σ = (6,1 +/- 0.1) e - FWHM = 138 eV 200 • K α -Gaussfit σ = 16,1 e - or counts @ 300 K 150 FWHM = 138 eV photo- 100 escape • low energy tail due to split k β peak 50 events (pixel size 50x50 µm) 0 2 3 4 5 6 7 Noise: ENC = 6.1e @ 300K Energy [keV]

Layout of DEPFET-Matrix • Source, Gate and Clear connected row- wise • Drain column-wise (zig-zag) • bond pads on end of columns/rows

DEPFET - Matrix Data Acquisition gate DEPFET-matrix clear off off signal charge in clear 64-bit-shift register on 64-bit-shift register int. Gate ~ off off signal-current - pedestal-current 64x64 pixel off off source I DRAIN V GATE, ON V CLEAR, ON V GATE, OFF V CLEAR, OFF drain ext. clear gate drain output • switch on one row through gate contacts, get pedestal current • after doing this for all rows, switch row on again, get signal current clear this row

DEPFET - Bioscope Developed ASICs: Gate-SWITCHER Clear-SWITCHER CARLOS: • low-noise 64-channel amplifier • track & hold • 10 MHz Serializer (64 to 1) SWITCHER: • 64 channels, 65MHz • AMS 25V HV-technology further components: • analog PBC with 12-bit ADC • digital PBC with XILINX for data acquisition 64 x 64 CARLOS DEPFET matrix 1 image (64x64 Pixel) per 1ms

DEPFET Pixel Bioscope System 8 SWITCHER 1MB (control chip) static RAM 2 3 40MHz XILINX OP XILINX CARLOS XILINX 64 x 64 Amp XC4010 (64 8 pulsed clear channel DEPJFET- AMP & matrix PCI - Card MUX) FiFo ADC (in PCI Slot) 64k x 18bit (12bit) 15 1 40MHz 2 SWITCHER 32 (control chip) ADC - DDC - Digital Hybrid Card DEPFET Card Power Supply Card 1 image (64x64 Pixel) per 1ms

The DEPFET Pixel Bioscope

X-Ray images: 64x64 Matrix, 50x50 µ m 2 Pixel Shadow image of toothed wheel of watch, 55 Fe- γ -Source (6keV) linear interpolation Pedestal Image 1,2 mm digital information

DEPFET - Charge collection efficiency 7000 6000 Signal [Elektronen] 5000 4000 3000 L M 2000 N O P 1000 R T Total 0 -1000 0 50 100 150 200 250 300 X Achse [ µ m] Laser Scan across matrix with bricked pixel layout (50x50 µ m 2 ) homogeneous charge collection efficiency! (no charge loss into clear contacts)

DEPFET - linearity and noise 600 241 Am All 4096 Pixels: 500 Tb 400 ADC-Wert Ba 109 Cd K β 300 109 Cd K 400 B α σ Gauss = (119 ± 8) e 350 Gauss Fit Mo 200 300 Rb 250 Häufigkeit Cu 200 100 55 Fe 150 100 50 0 0 -400 -200 0 200 400 Elektronen [e] 0 10 20 30 40 50 60 Energie [keV] very good linearity [6 - 60keV] low noise of single image: σ noise = 84 ±6 e

Tritium-Detection: 64x64 DEPFET-Matrix 3 H-Microscale (30 Bq per block) (18keV β -endpoint-energy) 24h measurement 3 H-radiograph Tritium-detection possible (8 σ threshold) !!!

Spatial Resolution with 55 Fe-Source 75 µ m thick tungsten sample, 55 Fe-6keV-source 6.67 LP/mm 5 LP/mm 10 LP/mm FAUST 200 (50 µ m ) (75 µ m ) (100 µ m ) c o u n t i n g r a t e 150 2 mm 20 LP/mm (25 µ m ) 100 100 um 75 um 50 um 25 um 50 3 mm 0 500 1000 1500 2000 2500 3000 p r o j e c t i o n a x i s [ µ m ] linear interpolation 28 LP/mm resolution! (1Pixel = Spatial Resolution 12.5 x 12.5 µ m 2 ) σ gauss = 9,0 ± 0,6 µ m digital (50x50 µm 2 )

DEPFET - Performance Summary: • very good SNR (> 80 @ 6keV) • 200 nm thin, homogeneous entrance window • non-destructive readout -> multiple readout possible • very fast readout, partial readout of matrix possible • small deadtime ( < 0,1 % of Data Acquisition time) -> high efficiency • small pixelsize (50 µm)

DEPFET - Applications: Biomedicine (Autoradiography): • Real time detection of 3 H at room temperature without vacuum • Good energy resolution -> different radioactive markers X-Ray Astronomy (sucessor of XMM: XEUS) • low energy γ ’s • high rates, nearly no dead time, no ghost hits Particle Physics (TESLA) • thin detectors (30µm) • small pixel size (30x30 µm 2 )

Biomedical Application: Autoradiography 3 H: β -decay, 6keV (mean) 14 C: β -decay, 50keV (mean) radioactively marked sample AgBr-Emulsion (d<10 µ m) Good spatial resolution, no time or energy information Digital Autoradiography: • time resolved -> real time observation of dynamic processes -> no development of film necessary (up to months) -> not sensitive to exposure time • energy resolution -> different radioactive markers • DEPFET -> detection of 3 H (room temperature, no vacuum!)

X-ray astronomy: XEUS (2010-2015) XMM-successor: „X-ray Evolving Universe Spectroscopy“ pn-CCDs too slow for „Wide Field Imager“ DEPFET-Advantages: • high rates • no „ghost hits“ • rad hard (no transfer of signal charges necessary) • fast partial readout of matrix areas • multiple readout possible • nearly no dead time

Summary • DEPFET- single pixel: – ENC = 6,1 e @ room temperature • DEPFET Pixel Bioscope with 64 x 64 DEPFET Matrix: – Readout time for 1 image: ~ 1ms ~ 9 µ m – spatial resolution with simple linear interpolation: – noise of single image > 10 e – Tritium detected! – homogeneous charge collection efficiency! • future: time resolved measurements, various applications

DEPFET: Information Recent papers: W. Neeser, M. Böcker, P. Buchholz, P. Fischer, P. Holl, J. Kemmer, P. Klein, H. Koch, M. Löcker, G. Lutz, H. Matthäy, L. Strüder, M. Trimpl, J. Ulrici, N. Wermes; "DEPFET - a pixel device with integrated amplification", submitted to NIM A W. Neeser, M. Böcker, P. Buchholz, P. Fischer, P. Holl, J. Kemmer, P. Klein, H. Koch, M. Löcker, G. Lutz, H. Matthäy, L. Strüder, M. Trimpl, J. Ulrici, N. Wermes; "The DEPFET Pixel Bioscope", submitted to IEEE Trans. on Nucl. Sci. P. Klein, T. Aurisch, P. Fischer, W. Neeser, L. Strüder, M. Trimpl, J. Ulrici, J. Vocht, N. Wermes; "A DEPFET Pixel Bioscope for the Use in Autoradiography", submitted to NIM A Homepage: depfet.physik.uni-bonn.de