Armin Karcher, LBNL

1
Proton Radiation Damage in P-Channel CCDs
Fabricated on High-Resistivity Silicon.
Preferred Customer
Preferred Customer

• C. Bebek, D. Groom, S. Holland, A. Karcher, W.
  Kolbe, J. Lee, M. Levi, N. Palaio, B. Turko, M.
  Uslenghi, M. Wagner, G. Wang
• Lawrence Berkeley National Laboratory

2
Overview

• High-Resistivity CCDs
• Performance Parameters
• Irradiation
• Results
• Comparison to Conventional CCDs
• Conclusion

3
High-Resistivity CCDs
4
High-Resistivity CCDs
5
Performance Parameters

• Charge Transfer Efficiency (CTE)
• CTE becomes critical in large CCDs.
• Smaller CCDs would mean higher complexity in
  mosaic cameras.
• Radiation damage reduces CTE, making radiation
  tolerant CCDs essential for extended space
  missions.
• Dark Current
• Dark current can limit the usefulness of long
  exposures.
• It is a volume effect, stemming from thermal
  generation in the bulk silicon.
• High purity silicon and low operating
  temperatures along with a gettering process
  reduce dark current.

6
Irradiation

• 2 sets of 4 CCDs each were irradiated.
• One set incorporated an additional channel
  implant, reducing lateral charge movement to
  reduce CTE degradation.
• Applied doses of 5x109, 1x1010, 5x1010 and 1x1011
  protons/cm2 at 12 MeV.
• The highest dose corresponds to 300 years in a
  high earth orbit!
• Devices were irradiated at room temperature
  without power.

7
CTE Measurement
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CTE Results
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Improved Radiation Tolerance on notch implant
devices

10
CTE Dependence on Temperature
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Dark Current Degradation

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Dark Current vs Temperature
Dark Current vs Temperature
9
2
for CCD after 5x10
protons/cm
100000
208 K
10000
/h)
-
1000
100
Dark Current (e
10
158 K
e-0.609 eV/kT
1
0.1
50
60
70
80
90
100
1/kT (eV)
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Comparison to Conventional CCDs
1L.Cawley, C.Hanley, WFC3 Detector
Characterization Report 1 CCD44 Radiation Test
Results, Space Telescope Science Institute
Instrument Science Report WFC3 2000-05,
Oct.2000 2 T. Hardy, R. Murowinski, M.J. Deen,
Charge transfer efficiency in proton damaged
CCDs, IEEE Trans. Nucl. Sci., 45(2), pp.
154-163, April 1998
14
Conclusion

• P-channel high-resistivity CCDs show remarkable
  radiation tolerance against CTE degradation.
• Dark current remains low even after proton doses
  equivalent to decades in space.