Study of radiation damage in silicon detectors for high ... - F9
Study of radiation damage in silicon detectors for high ... - F9
Study of radiation damage in silicon detectors for high ... - F9
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92 6. Inuence <strong>of</strong> Bias VoltageSample producer V 0 FD [V] T [ C] eq [n/cm 2 s] eq [10 14 n/cm 2 ] V bias [V]S3A Micron 32. 15 + 1.910 9 0.45 200/0 S3B Micron 34. 15 + 1.910 9 0.45 0/200 D2A Micron 17. 15 1.810 10 0.42 300D2B Micron 17. 15 1.810 10 0.42 0UO6B S<strong>in</strong>tef 35. 20 1.810 11 1.7 1000/600 yUO6S S<strong>in</strong>tef 35. 20 1.810 11 1.7 0BA2B S<strong>in</strong>tef 44. 15 2.110 11 # 1.0 # 500BA2S S<strong>in</strong>tef 44. 15 2.110 11 # 1.0 # 0BA4B S<strong>in</strong>tef 40. 20 2.110 11 # 1.0 # 600BA4S S<strong>in</strong>tef 36. 20 2.110 11 # 1.0 # 0Table 6.2: List <strong>of</strong> diodes used to study the eect <strong>of</strong> bias voltage on defect development.Thickness <strong>of</strong> samples was 3005 m.+ ) Diodes S3 were kept at bout 27 C after transfer to the laboratory to accelerate anneal<strong>in</strong>g.When annealed, they were moved to 20 C to study anneal<strong>in</strong>g <strong>of</strong> the dierence <strong>in</strong> N eff . )DiodeS3Awas biased dur<strong>in</strong>g and unbiased after the ir<strong>radiation</strong>. ) Diode S3B was unbiased dur<strong>in</strong>g and biased after the ir<strong>radiation</strong>.y Diode UO6A was biased to 1000V at the reactor and to 600V at the laboratory. Bias voltagecould be reduced due to anneal<strong>in</strong>g <strong>of</strong> FDV.# ) Due to frequent changes <strong>in</strong> the reactor core at the time <strong>of</strong> ir<strong>radiation</strong>, the neutron spectrumwas not well known. This <strong>in</strong>duced an error on dosimetry, larger than the usual 15%.a consequence <strong>of</strong> slow anneal<strong>in</strong>g <strong>of</strong> bias dependent dierence. It could also be expla<strong>in</strong>edif reverse anneal<strong>in</strong>g was caused by reaction <strong>of</strong> charged defects and consequently sloweddown <strong>in</strong> electric eld. Available data however do not allow <strong>for</strong> unambiguous dist<strong>in</strong>ctionbetween these two possibilities. The dierence could not be expla<strong>in</strong>ed by partial bias,s<strong>in</strong>ce it develops already at an early stage <strong>of</strong> reverse anneal<strong>in</strong>g, when bias<strong>in</strong>g voltage <strong>of</strong>200 V was still above FDV <strong>of</strong> the biased samples. This dierence <strong>in</strong> reverse anneal<strong>in</strong>g <strong>of</strong>biased and unbiased samples also contributes to the error <strong>in</strong> determ<strong>in</strong>ation <strong>of</strong> the reverseanneal<strong>in</strong>g reaction constants <strong>of</strong> the partially biased samples as discussed <strong>in</strong> section 4.2.For further studies we wished to m<strong>in</strong>imise the <strong>in</strong>uence <strong>of</strong> any uncontrolled parametersand to avoid errors from uence measurements. Thus diodes were irradiated andmonitored <strong>in</strong> pairs, with a biased and unbiased diode <strong>in</strong> each pair. Both diodes were takenfrom the same wafer to m<strong>in</strong>imise the risk <strong>of</strong> dierence caused by material. Five pairs aslisted <strong>in</strong> table 6.2 were studied this way. Samples S3 and D2 were Micron oat-zone p + -n-n + diodes with 3 guard r<strong>in</strong>gs and an active area <strong>of</strong> 11 cm 2 . Samples UO6, BA2 andBA4 were p + -n-n + planar diodes processed by S<strong>in</strong>tef. They had a multiple guard-r<strong>in</strong>gstructure that was not connectable and thus oat<strong>in</strong>g. Samples marked with last letter