Patterning thick diffused junctions on CdTe

Juha Kalliopuska (Corresponding Author), Seppo Nenonen, Heikki Sipilä, Hans Andersson, Sami Vähänen, Simo Eränen, Lukas Tlustos

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)

Abstract

Dividing the detector crystal into discrete pixels enables making an imaging detector, in which the charge collected by each pixel can be read separately. Even if the detector is not meant for imaging, patterns on the crystal surface may be used as guard structures that control and limit the flow of charges in the crystal. This has been exceedingly hard for the detector crystals having thick diffused layers. The paper reports a patterning method of the thick diffused junctions on CdTe. The patterning method of In-diffused pn-junction on CdTe chip is demonstrated by using a diamond blade. The patterning is done by removing material from the pn-junction side of the chip, so that the trenches penetrate the diffused layer. As the trenches extend deeper into the bulk than the junction, the regions separated by the trench are electrically isolated. Electrical characterization results are reported for the strips separated by trenches with various depths. The strip isolation is clearly seen in both measured leakage currents and inter-strip resistances. The paper also represents the first images of the pixelated CdTe chips bump bonded to the Medipix2 readout chip. The images were taken with the Sr90 source. The CdTe chips had 110 μm×110 μm and 55 μm×55 μm pixel grid spacing. The images demonstrate the imaging capability of the pixelated chips and give an idea on the uniformity and quality of the pixelization method.

Original languageEnglish
Pages (from-to)98-102
JournalNuclear Instruments and Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume607
Issue number1
DOIs
Publication statusPublished - 2009
MoE publication typeA1 Journal article-refereed

Fingerprint

chips
Detectors
Crystals
Pixels
Imaging techniques
strip
pixels
detectors
Leakage currents
crystals
Diamonds
blades
crystal surfaces
readout
isolation
leakage
diamonds
grids
spacing

Keywords

  • CdTe
  • Imaging detector
  • Diamond blade
  • Patterning
  • Pixelization
  • Leakage current
  • Inter-strip resistance

Cite this

Kalliopuska, Juha ; Nenonen, Seppo ; Sipilä, Heikki ; Andersson, Hans ; Vähänen, Sami ; Eränen, Simo ; Tlustos, Lukas. / Patterning thick diffused junctions on CdTe. In: Nuclear Instruments and Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 2009 ; Vol. 607, No. 1. pp. 98-102.
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Patterning thick diffused junctions on CdTe. / Kalliopuska, Juha (Corresponding Author); Nenonen, Seppo; Sipilä, Heikki; Andersson, Hans; Vähänen, Sami; Eränen, Simo; Tlustos, Lukas.

In: Nuclear Instruments and Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 607, No. 1, 2009, p. 98-102.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Patterning thick diffused junctions on CdTe

AU - Kalliopuska, Juha

AU - Nenonen, Seppo

AU - Sipilä, Heikki

AU - Andersson, Hans

AU - Vähänen, Sami

AU - Eränen, Simo

AU - Tlustos, Lukas

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N2 - Dividing the detector crystal into discrete pixels enables making an imaging detector, in which the charge collected by each pixel can be read separately. Even if the detector is not meant for imaging, patterns on the crystal surface may be used as guard structures that control and limit the flow of charges in the crystal. This has been exceedingly hard for the detector crystals having thick diffused layers. The paper reports a patterning method of the thick diffused junctions on CdTe. The patterning method of In-diffused pn-junction on CdTe chip is demonstrated by using a diamond blade. The patterning is done by removing material from the pn-junction side of the chip, so that the trenches penetrate the diffused layer. As the trenches extend deeper into the bulk than the junction, the regions separated by the trench are electrically isolated. Electrical characterization results are reported for the strips separated by trenches with various depths. The strip isolation is clearly seen in both measured leakage currents and inter-strip resistances. The paper also represents the first images of the pixelated CdTe chips bump bonded to the Medipix2 readout chip. The images were taken with the Sr90 source. The CdTe chips had 110 μm×110 μm and 55 μm×55 μm pixel grid spacing. The images demonstrate the imaging capability of the pixelated chips and give an idea on the uniformity and quality of the pixelization method.

AB - Dividing the detector crystal into discrete pixels enables making an imaging detector, in which the charge collected by each pixel can be read separately. Even if the detector is not meant for imaging, patterns on the crystal surface may be used as guard structures that control and limit the flow of charges in the crystal. This has been exceedingly hard for the detector crystals having thick diffused layers. The paper reports a patterning method of the thick diffused junctions on CdTe. The patterning method of In-diffused pn-junction on CdTe chip is demonstrated by using a diamond blade. The patterning is done by removing material from the pn-junction side of the chip, so that the trenches penetrate the diffused layer. As the trenches extend deeper into the bulk than the junction, the regions separated by the trench are electrically isolated. Electrical characterization results are reported for the strips separated by trenches with various depths. The strip isolation is clearly seen in both measured leakage currents and inter-strip resistances. The paper also represents the first images of the pixelated CdTe chips bump bonded to the Medipix2 readout chip. The images were taken with the Sr90 source. The CdTe chips had 110 μm×110 μm and 55 μm×55 μm pixel grid spacing. The images demonstrate the imaging capability of the pixelated chips and give an idea on the uniformity and quality of the pixelization method.

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KW - Imaging detector

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KW - Patterning

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ER -