Pixel silicon detector infrared laser tests

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Pixel silicon detector infrared laser tests proof
of concept
G. Chiodini, S. W. Kwan, M. Rovere, S. Sala, and
S. Cihangir
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Mechanical mounting
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Optical fiber
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Close up
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Total charge collected in the cluster

• Comments
• The charge decrease with B. charge loss in the
  pixel boundaries?
• Pspray Seiko sensor has charge loss.
• Vbias-50V is just about depletion. FE can
  behaves strangely.

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Charge center of gravity displacement of the
cluster
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Summary

• The setup is sensitive enough to see the effect
  of the magnetic field on the charge collection.
• Charge losses have to be taken into account when
  extracting the Lorentz angle.
• Geometry effects must be studied.

8
Sensor Irradiation

• 1st irradiation done in mid-August
• Test pixels from Wafer 1(oxygenated) and wafer
  23(non-oxygenated)
• Common and individual p-stop
• 2 different guard ring structures
• 2 devices to 8x1013, rest to 4x1014
• 2nd irradiation done last week
• Single chip FPIX1-sized sensors from the same 2
  wafers

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Prelim results (Low Dosage)
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High Dosage
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FPIX1 single chip sensor
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Bump Bonding Update

• Problem with MCNC solder bumps
• Metal on p-side got attacked during UBM formation
• Still working on a solution
• Proposals
• Deposit Cu to protect the wafer and remove it
  later
• Deposit nitride passivation and then etch away
• Change sensor design slightly(expose pad for
  probing and pad for biasing of detector protected
  by passivation which will be removed after UBM
  has been put on)
• Protect with photoresist