TY - JOUR
T1 - Development of n+-in-p planar pixel sensors for extremely high radiation environments, designed to retain high efficiency after irradiation
AU - Unno, Y.
AU - Kamada, S.
AU - Yamamura, K.
AU - Ikegami, Y.
AU - Nakamura, K.
AU - Takubo, Y.
AU - Takashima, R.
AU - Tojo, J.
AU - Kono, T.
AU - Hanagaki, K.
AU - Yajima, K.
AU - Yamauchi, Y.
AU - Hirose, M.
AU - Homma, Y.
AU - Jinnouchi, O.
AU - Kimura, K.
AU - Motohashi, K.
AU - Sato, S.
AU - Sawai, H.
AU - Todome, K.
AU - Yamaguchi, D.
AU - Hara, K.
AU - Sato, Kz
AU - Sato, Kj
AU - Hagihara, M.
AU - Iwabuchi, S.
N1 - Funding Information:
The irradiations were performed, with protons at Cyclotron and Radioisotope Center (CYRIC), Tohoku University, with Y. Sakemi, M. Ito, and T. Wakui, and with γ at Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency. The research was supported and financed in part by the Japan Society for Promoting Science KAKENHI-A Grant number 20244038 and KAKENHI-C Grant number 20540291 , the Ministry of Education, Culture, Sports, Science and Technology – Japan, KAKENHI for Research on Priority Area Grant number 20025007 and for Scientific Research on Innovative Areas Grant number 23104002 .
Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2016/9/21
Y1 - 2016/9/21
N2 - We have developed n+-in-p pixel sensors to obtain highly radiation tolerant sensors for extremely high radiation environments such as those found at the high-luminosity LHC. We have designed novel pixel structures to eliminate the sources of efficiency loss under the bias rails after irradiation by removing the bias rail out of the boundary region and routing the bias resistors inside the area of the pixel electrodes. After irradiation by protons with the fluence of approximately 3×1015neq/cm2, the pixel structure with the polysilicon bias resistor and the bias rails removed far away from the boundary shows an efficiency loss of <0.5% per pixel at the boundary region, which is as efficient as the pixel structure without a biasing structure. The pixel structure with the bias rails at the boundary and the widened p-stop's underneath the bias rail also exhibits an improved loss of approximately 1% per pixel at the boundary region. We have elucidated the physical mechanisms behind the efficiency loss under the bias rail with TCAD simulations. The efficiency loss is due to the interplay of the bias rail acting as a charge collecting electrode with the region of low electric field in the silicon near the surface at the boundary. The region acts as a “shield” for the electrode. After irradiation, the strong applied electric field nearly eliminates the region. The TCAD simulations have shown that wide p-stop and large Si–SiO2 interface charge (inversion layer, specifically) act to shield the weighting potential. The pixel sensor of the old design irradiated by γ-rays at 2.4 MGy is confirmed to exhibit only a slight efficiency loss at the boundary.
AB - We have developed n+-in-p pixel sensors to obtain highly radiation tolerant sensors for extremely high radiation environments such as those found at the high-luminosity LHC. We have designed novel pixel structures to eliminate the sources of efficiency loss under the bias rails after irradiation by removing the bias rail out of the boundary region and routing the bias resistors inside the area of the pixel electrodes. After irradiation by protons with the fluence of approximately 3×1015neq/cm2, the pixel structure with the polysilicon bias resistor and the bias rails removed far away from the boundary shows an efficiency loss of <0.5% per pixel at the boundary region, which is as efficient as the pixel structure without a biasing structure. The pixel structure with the bias rails at the boundary and the widened p-stop's underneath the bias rail also exhibits an improved loss of approximately 1% per pixel at the boundary region. We have elucidated the physical mechanisms behind the efficiency loss under the bias rail with TCAD simulations. The efficiency loss is due to the interplay of the bias rail acting as a charge collecting electrode with the region of low electric field in the silicon near the surface at the boundary. The region acts as a “shield” for the electrode. After irradiation, the strong applied electric field nearly eliminates the region. The TCAD simulations have shown that wide p-stop and large Si–SiO2 interface charge (inversion layer, specifically) act to shield the weighting potential. The pixel sensor of the old design irradiated by γ-rays at 2.4 MGy is confirmed to exhibit only a slight efficiency loss at the boundary.
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U2 - 10.1016/j.nima.2016.04.039
DO - 10.1016/j.nima.2016.04.039
M3 - Article
AN - SCOPUS:84966694865
VL - 831
SP - 122
EP - 132
JO - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
SN - 0168-9002
ER -