Technology for High-Z Direct Converting Detectors

Transcription

1 Technology for High-Z Direct Converting Detectors Michael Fiederle Freiburger Materialforschungszentrum ANKA KIT

2 Outline Background high-z detector materials High-Z semiconductor production High-Z semiconductors technology The early bird gets the worm - I hate worms High-Z pixel detectors with Medipix3 Summary and Outlook HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 2

3 Radiation detectors with high-z materials Single detectors with high energy resolution for isotope identification Compact Systems Pixel detectors: combination with electronics Spatially resolving systems Tracking of charged particles HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 3

4 Potential applications of high-z pixel detectors X-ray Imaging (2D imaging): - Pixel detectors with µm resolution X-ray Diffraction: - Large areas detectors High flux X-ray CT applications: - Pixel detectors with 200 µm and higher spatial resolution - High photon fluxes: 10 9 mm 2 /s and higher - Medical CT: Protytypes by GE Health Siemens Philips HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 4

5 High Z direct converter X-ray detectors Direct converter => semiconductor material combination with Photon Counting Chip: Counting instead of integration Hybridisation of detector and electronic: Flip-chip bonding technology Semiconductor materials: - CdTe - CdZnTe - GaAs MRS M. Fiederle, GaAs Pixeldetectors 5

6 High-Z semiconductors X-ray detectors X-ray sensor = bulk device: active volume = sensor thickness Absorption (efficiency) correlated with thickness Efficiency of Silicon above 20 kev too low => Compound semiconductor Required material properties: High resistivity > 10 8 Ohmcm (intrinsic) High mobility-lifetime product Homogeneity of electronic properties (µm-range) HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 6

7 Potential candidates high-z semiconductors S. Del Sordo et al., 2009, Sensors 2009, 9, HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 7

8 Potential candidates high-z semiconductors Absorption Resistivity Charge Transport Quality Technology Si Ge cooling GaAs CdTe CdZnTe HgI 2 Most ++++ promising ++++ candidates: ++ CdTe, CdZnTe + and GaAs + TlBr Compromise of: - Efficiency Quality - Stability Efficiency - Available Noise planar Spectr. technology Size Pixel Performance detectors HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 8

9 High-Z detectors applications Strong need for high-z detectors but.. Most scientists do not like high-z materials Why? High-Z technolgy High-Z is Alchemy: Alchemy, Voodoo, Black Magic Crystal growth only at full moon Bonding around midnight HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 9

10 Facts high-z semiconductor materials Facts high resistivity >10 9 Ohmcm sensitive to temperature and force complex equillibrium of shallow and deep levels (impurites + defects) Constant improvement of material and technology (since 1960) Suitable planar technology available Myth unpredictable performance unstable materials undoped semiconductor promised performance but no improvement in recent years no technology available (different to Si-technology!) wafers with 3 diameter available HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 10

11 High-Z detector material Compensation of shallow levels: - Complex situation of several defects + impurities - Adjustment of doping within a few ppb HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 11

12 CdTe and CdZnTe crystal grower Merge of material supplier + technology + system suppliers: - Orbotech with GE - GammaMedica / IDEAS with GE - ev with Kromek, UK - AJAT with XCounter - Acrorad owned by Siemens HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 12

13 CdTe detector wafers CdTe crystals from Acrorad 3 (75 mm) diameter single crystals High resistivity: 5 x 10 9 Ohmcm Good homogeneity of electrical properties 3 wafers for planar technology processing 1 and 2 mm thickness Resistivity map HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 13

14 GaAs for X-ray sensors Long term history Different approaches: Bulk material LEC GaAs undoped LEC GaAs Cr doped (Thick) thin films: Vapor Phase epitaxy GaAs Liquid Phase Reminder: epitaxy GaAs - GaAs is commercial available material - GaAs wafers up to 8 inch diameter - Growth methods: Liquid Encapsulated Czochralski LEC and Vertical Gradient Freeze VGF - Semi-insulating (undoped using EL2 defect) HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 14

15 GaAs X-ray detectors A. Owen et al P. Kostamo et al R. Irsigler (ACREO) et al HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector L. Tlustos, C. Fröjdh (MSU) et al

16 GaAs X-ray detectors LEC GaAs: - dislocation network - instable performance - small depletion width Epi - GaAs: - small area - no flat surface - small thickness M. Fiederle et al M. Fiederle et al HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 16

17 Pixel detectors produced at FMF Processing 3 inch wafers: Metallization Passivation UBM deposition Backside preparation Backside contact (CdTe) Dicing Hybridization Module assembling Medipix2/3: - Mounting assembly - Wirebonding - Testing In-house processing FMF HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 17

18 Flip chip bonding CdTe / GaAs at FMF Bumps deposited on detector wafer Low temperature bumps using In-Sn alloy Low temperature and low stress polymer passivation Limitations: - Minimum size of bump: 15 µm diameter - Dead area between pixels and sensor edge: 200 µm - Maximum size of monolithic sensor limited by wafer diameter of 75 mm Maximum CdTe/ GaAs module: 28x43 mm pixels (Medipix) HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 18

19 Improvement of technology Medipix bump Detector Synchrotron Laminography of bump-bonds (GaAs flip-chip technique) Feng Xu, KIT HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 19

20 Medipix detectors Developed by Medipix2 / Medipix3 CERN Medipix detector: Electronics chip (ASIC) + sensor Medipix3 single 14x14 mm² Medipix2 Hexa 28x42 mm² HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 20

21 Technical data: MPX2 vs. MPX3 MPX2 MPX3 Technology: 0.25 µm CMOS 0.13 µm CMOS Pixels: 256x x256 Pixel dimens.: 55 µm 55 µm 110 µm Color Mode Pixel area: 14.08x14.08 mm² 14.08x14.08 mm² Active IC area: 87.1 % 88.4 % bottom WB 94.3 % TSV Counter: 1x 13.5 bit 2x 12 bit (11,810) (2x 4,096 / 16,777,216) 8x 12 bit Color Mode Thresholds: THL + THH 2x THL 8x THL Color Mode R. Ballabriga et al., Medipix3: A 64 k pixel detector readout chip working in single photon HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector counting mode with improved spectrometric performance, NIM A

22 MPX3 front-end operating modes Single Pixel Mode (SPM) every pixel works independently of its neighbours, behaving in a way similar to the working mode of traditional detectors Charge Summing Mode (CSM) The charge in every cluster of 4 pixels is added and assigned to the pixel with the largest charge deposition. Colour Mode The readout pixels are grouped in clusters of four and become a single detection unit. In this mode, the pixel pitch is 110 µm x 110 µm and only one readout pixel in four is bump bonded. Colour Mode can be programmed for Single Pixel operation and Charge Summing operation. R. Ballabriga et al., Medipix3: A 64 k pixel detector readout chip working in single photon HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 22 counting mode with improved spectrometric performance, NIM A 2011

23 Medipix3 sensors Si: µm µm CdTe: (ohmic c.) µm - 1 mm - 2 mm GaAs: µm CdTe GaAs Si µm µm HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 23

24 GaAs sensors Sensors by Tomsk S.U. Bonding by FMF GALAPAD Project: Coordinated by H. Graafsma: Partners: Tomsk SU, JNIR Dubna, DESY, KIT and FMF HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 24

25 Images with GaAs assemblies TPX assembly 25 kv 200 V TH0 20 kev HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 25

26 Images with GaAs assemblies TPX assembly 25 kv 200 V TH0 20 kev HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 26

27 Spatial resolution of GaAs assemblies MPX3 assembly 25 kv 200 V TH0 6 kev HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 27

28 High flux measurements synchrotron 10 8 photons / mm 2 s HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 28

29 High flux measurements synchrotron 10 8 photons / mm 2 s Limitation by Medipix3 electronics HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 29

30 Images with GaAs assemblies Bias: -200 V MPX3 GaAs SPM 24-Bit 8x6 tiles image by Simon Procz MPX3 assembly 25 kv 200 V TH0 6 kev HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 30

31 GaAs Medipix3 RX Bias: -200 V MPX3 GaAs SPM 24-Bit 8x6 tiles image by Simon Procz HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 31

32 Latest version Medipix3RX CdTe 3RX assemblies Charge Summing Mode 55 µm pixel 110 µm pixel HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 32

33 CdTe Medipix3 RX assemblies 55 µm pixels - Spectroscopy HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 33

34 CdTe Medipix3 RX 110 µm pixels 2 mm thickness - Spectroscopy HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 34

35 Energy selective, planar imaging MPX3 CdTe 1mm - Colour Mode 110µm Piezo Lighter Magnification: 1.3x Bias: -320V MPX3 CdTe 1mm Colour Mode 4x11 tiles RGB: 9-50 kev A: Logarithmic grayscale sum B: Coloured X-ray image 9-14 kev kev kev C: Linear grayscale sum HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 35

36 High resolution imaging MPX3 CdTe 1mm SPM 55µm CF card Width: 42.8 mm Mag. 1.74x Bias: -290 V MPX3 CdTe SPM 24-Bit 8x7 tiles Intensity image by Simon Procz HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 36

37 Our first CdTe reconstruction Monkey Skull CT reconstruction width ~40mm MPX3 CdTe 55µm SPM 24-Bit 5x4 tiles image by Simon Procz HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 37

38 CdTe Hexa Modul Timepix Large module: 28 x 43 mm 2 from 3 wafers Hexa module (3x2 Medipix) 55 µm and 165 µm pixels HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 38

39 Hexa-Modul with 55 µm pixels Selective pixel median filter algorithm only filters noisy pixels 512x768 pixels ~ pixels 28x43 mm² area HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 39

40 CdTe Hexa 55 µm CdTe Hexa 28x43 mm 2 with Medipix 3RX Assembling of HGF-Cube on LAMDA-boards from DESY First Medipix3 Hexa CdTe assembly

41 CdTe Hexa 28x43 mm 2 with Medipix 3RX: First image with Helmholtz Cube: Single Pixel Mode Measurements by D. Pennicard DESY)

42 CdTe Hexa 28x43 mm 2 with Medipix 3RX: First image with Helmholtz Cube: Charge Summing Mode Measurements by D. Pennicard DESY)

43 Summary & Outlook Summary: - Continous development of high-z pixel detectors: - Pixel detectors with GaAs and CdTe available - Improvement of performance and technology by intensive characterization - Manufacturing of pixel detector systems - High flux up to 10 8 photons/mm 2 /s Outlook: - CdTe and GaAs pixel detector systems with Hexa modules 42x28 mm 2 active area - Medipix3 systems for application at beamlines - Crystal growth of larger diameters HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector 43

44 Acknowledgement Teams FMF: Martin Pichotka, Leonhard Alaribe, Simon Procz, Andreas Zwerger, Alex Fauler (Processing and Bonding) KIT - ANKA: Angelica Cecilia, Elias Hamann, Thomas König, Tilo Baumbach Medipix2 and Medipix3 collaboration HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector

45 Acknowledgement Funding: BMBF: 05K10CKA Pixeldetektoren Synchrotron EDAS K10VFA GaAs Pixeldetectors GALAPAD 05K10VFC GaAs Pixeldetectors GALAPAD EU FP7: EU Project No LACX Large x-ray detectors for Colored X-ray Imaging Uni Freiburg Anschubfinanzierung BIRD KIT ANKA Finanzierung BIRD Thank you for your attention! HGF Heräus Seminar - M. Fiederle, Technology High-Z Detector