University of Kobe, Yota Kojima

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Surface Observation of mPIC with Scanning
Electron Microscope(SEM) ????????????mPIC?????

• University of Kobe, Yota Kojima
• 2007/01/26 at Saga University

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Characteristics of mPIC

• Micro Pixel Chamber(mPIC) being developed as 3D
  imaging radiation detector.
• Advantages
  Larger
  Detection area with 2D readout.
• Easy extension to 3D imaging.
  
• Fabricated with commercial PCB Technology.

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Purpose of this study

• For MIPS detector, stable higher gas gain (?104)
  is needed.
• Current mPIC suffered from frequent discharge in
  higher gain operation.
• Analysis of damaged Pixel is very important.
• What happens in the phenomena and what trace it
  left on µPIC ?
• SEM observation could give us fruitful
  information.

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mPIC
3 cm3 cm mPIC built on Polyimide base
An image of mPIC by a stereo microscope (100)
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Electrode Structure
Polyimide Dielectric Strength 500 V1000 V/100
mm
100 mm
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A Principle of Imaging with SEM
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A Principle of Imaging with SEM

• Detecting SE, BE, X-ray from surface of sample

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Analyze with SEM
Signal Source Secondary Electron(SE) Backscattered Electron(BE) Backscattered Electron(BE)
Intensity High Low Low
Sensitivity Topology Composition Topology depth
Notation SEI BEI COMPO BEI TOPO
Affected by charging up Yes No No
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Scanning Electron Microscope
Electron Gun

• Japan Electron Optics Laboratory
• (JEOL)
• JSM-6000FS

Specimen holder
Field Emission Gun Space Resolution 0.6 nm
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An Example of CD image
Magnification 25000

• Specimen Size(Max)20 mm6 mm3.5 mm
• Vacuum level of Specimen Chamber10-4 Pa

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Non Damaged Pixel (SEI)

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Non Damaged Pixel 2(SEI)
Bright image shows insulated region by electron
charging up
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Damaged Pixel(SEI)
No Charging up !
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Difference between Damaged and Non-Damaged Pixel
Non Damaged
Non Damaged

• Different contrast seen
• by charging up.
• Conductor(metal?) is covering on Polyimide ?

Damaged
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Image difference on analysis methods
Au Upper part Ni Lower part
BEI COMPO
BEI TOPO
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Image difference by BEI COMPO method
Non Damaged Pixel
Damaged Pixel
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Carbon on Polyimide ? (BEI COMPO method)
Non Damaged Pixel
Damaged Pixel
Carbon Tape

• Damaged area and Carbon Tape have similar
  contrast.

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Flatness on Polyimide area by BEI TOPO method
Non Damage
Damaged Pixel
Surface might be smoothed by carbon deposition?
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Summary

• We observed mPIC by SEM.
• The SEI analysis method shows that Polyimide area
  of the damaged pixel could be covered with
  conductive material.
• The most probable candidates of conductive
  material is carbon.
• EDS method(measurement of characteristic X-ray)
  could make above description clear.

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ChUP?????????(????)

• ???????(???)?????????????
• ?????????????????????????
• ???????????????????

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m-PIC
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Image difference on analysis methods
BEI TOPO
Au Upper part Ni lower part
BEI COMPO
SEI
Distinguishable the difference in case of Gold
and Nickel