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

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

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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

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SLIDE 1

DEPFET Pixel: A Pixel Device with Integrated Amplification

Johannes Ulrici Bonn University FAUST Semiconductor Lab

Pixel 2000 Conference Genova, 4.6.-8.6. 2000

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SLIDE 2

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

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SLIDE 3

p+ n p n+ S D G n+

internal gate

Integration of JFET DEPFET Advantage:

  • Small input capacitance
  • no stray capacitance

=> Large Signal to Noise Ratio

DEPFET - principle idea

p+

n

n+ p n+ S D G

Sensor Diode Preamplifier (p-JFET) Kemmer, Lutz (1987):

  • integrate preamplifier into

Sensor Si- Substrate

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SLIDE 4

DEPFET - charge collection

  • sidewards depletion
  • electrons collected in internal gate
  • channel current of JFET modulated by signal charges

Ionising particle

p+ p+ n+ n n+

totally depleted n--substrate internal gate rear contact source top gate drain bulk potential via axis top-gate / rear contact V potential minimum for electrons

p-channel p+

  • +

+ + +

  • -
  • ~1 µm

~300 µm

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SLIDE 5

DEPFET - Clear Mechanism

  • Internal gate filled by

signal charges and thermally generated electrons

  • „Reset“ needed
  • One possibility:

pulsed clear!

  • Other clear mechanisms:
  • cont. clear, gate clear, ...

p+ p+ n+

rear contact drain bulk source

p symmetry axis n+ n

internal gate top gate clear

n - n+ p+

0V +15V 0V

pulsed clear: dead time less than 0,1% of measuring time

  • -
  • -
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SLIDE 6

DEPFET - Measurements on Single Pixel Devices

Spectrum of 55Fe-Source:

  • At room temperature (300 K)
  • Shapingtime: 10µs
  • Noise Peak σ = (6,1 +/- 0.1) e-
  • Kα-Gaussfit σ = 16,1 e- or

FWHM = 138 eV

  • low energy tail due to split

events (pixel size 50x50 µm) Noise: ENC = 6.1e @ 300K

2 3 4 5 6 7 50 100 150 200 250 300 350

FWHM = 138 eV @ 300 K

kβ kα

photo- escape peak

55Fe kα = 5,89 keV 55Fe kβ = 6,49 keV

counts

Energy [keV]

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SLIDE 7

Layout of DEPFET-Matrix

  • Source, Gate and Clear connected row-

wise

  • Drain column-wise (zig-zag)
  • bond pads on end of columns/rows
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SLIDE 8

DEPFET - Matrix Data Acquisition

64x64 pixel IDRAIN

DEPFET-matrix

VGATE, OFF

  • ff
  • ff
  • n
  • ff

VGATE, ON 64-bit-shift register

gate drain

VCLEAR, OFF

  • ff
  • ff

clear

  • ff

VCLEAR, ON 64-bit-shift register

clear

  • utput
  • 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

ext. gate source drain clear

signal charge in

  • int. Gate ~

signal-current - pedestal-current

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SLIDE 9

Developed ASICs: CARLOS:

  • low-noise 64-channel amplifier
  • track & hold
  • 10 MHz Serializer (64 to 1)

SWITCHER:

  • 64 channels, 65MHz
  • AMS 25V HV-technology

DEPFET - Bioscope

64 x 64 DEPFET matrix CARLOS Gate-SWITCHER Clear-SWITCHER further components:

  • analog PBC with 12-bit ADC
  • digital PBC with XILINX for

data acquisition 1 image (64x64 Pixel) per 1ms

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SLIDE 10

DEPFET Pixel Bioscope System

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

8

OP Amp 40MHz XILINX XC4010 15 1 2

1 image (64x64 Pixel) per 1ms

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SLIDE 11

The DEPFET Pixel Bioscope

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SLIDE 12

X-Ray images: 64x64 Matrix, 50x50µm2 Pixel

Shadow image of toothed wheel of watch, 55Fe-γ-Source (6keV)

1,2 mm

Pedestal Image digital information linear interpolation

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SLIDE 13

50 100 150 200 250 300

  • 1000

1000 2000 3000 4000 5000 6000 7000

L M N O P R T Total

Signal [Elektronen]

X Achse [µm]

DEPFET - Charge collection efficiency

Laser Scan across matrix with bricked pixel layout (50x50µm2) homogeneous charge collection efficiency! (no charge loss into clear contacts)

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SLIDE 14

10 20 30 40 50 60 100 200 300 400 500 600

241Am

Ba Tb Cu

109Cd K α 109Cd K β

Mo Rb

55Fe

ADC-Wert

Energie [keV]

DEPFET - linearity and noise

All 4096 Pixels:

  • 400
  • 200
200 400 50 100 150 200 250 300 350 400

σ

Gauss = (119 ± 8) e

Häufigkeit

Elektronen [e]

B Gauss Fit

very good linearity [6 - 60keV] low noise of single image: σnoise = 84 ±6 e

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SLIDE 15

Tritium-Detection: 64x64 DEPFET-Matrix

Tritium-detection possible (8σ threshold) !!!

3H-radiograph

3H-Microscale (30 Bq per block)

(18keV β-endpoint-energy) 24h measurement

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SLIDE 16

Spatial Resolution with 55Fe-Source

75µm thick tungsten sample, 55Fe-6keV-source

500 1000 1500 2000 2500 3000 50 100 150 200 6.67 LP/mm (75 µ m ) 5 LP/mm (100 µ m ) 10 LP/mm (50 µm ) 20 LP/mm (25 µ m )

c o u n t i n g r a t e

p r o j e c t i o n a x i s [ µ m ]

digital (50x50 µm2)

FAUST

100 um 50 um 25 um 75 um

2 mm 3 mm linear interpolation (1Pixel = 12.5 x 12.5µm2)

28 LP/mm resolution! Spatial Resolution σgauss= 9,0 ± 0,6 µm

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SLIDE 17

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)
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SLIDE 18

DEPFET - Applications:

Biomedicine (Autoradiography):

  • Real time detection of 3H 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 µm2)
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SLIDE 19

Biomedical Application: Autoradiography

Good spatial resolution, no time or energy information radioactively marked sample

14C: β-decay, 50keV (mean) 3H: β-decay, 6keV (mean)

AgBr-Emulsion (d<10µm) 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 3H (room temperature, no vacuum!)
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SLIDE 20

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
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SLIDE 21

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 – spatial resolution with simple linear interpolation: ~ 9µm – noise of single image > 10 e – Tritium detected! – homogeneous charge collection efficiency!

  • future: time resolved

measurements, various applications

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SLIDE 22

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