We have developed a novel and highly radiation-tolerant n-in-p silicon microstrip sensor for very high radiation environments such as in the Super Large Hadron Collider. The sensors are designed for a fluence of 1×1015 neq/cm2 and are fabricated from p-type, FZ, 6 in. (150 mm) wafers onto which we lay out a single 9.75 cm×9.75 cm large-area sensor and several 1 cm×1 cm miniature sensors with various n-strip isolation structures. By evaluating the sensors both pre- and post-irradiation by protons and neutrons, we find that the full depletion voltage evolves to approximately 800 V and that the n-strip isolation depends on the p+ concentration. In addition, we characterize the interstrip resistance, interstrip capacitance and the punch-through-protection (PTP) voltage. The first fabrication batch allowed us to identify the weak spots in the PTP and the stereo strip layouts. By understanding the source of the weakness, the mask was modified accordingly. After modification, the follow-up fabrication batches and the latest fabrication of about 30 main sensors and associated miniature sensors have shown good performance, with no sign of microdischarge up to 1000 V.

Development of n-on-p silicon sensors for very high radiation environments

We are developing n+-in-p, p-bulk and n-readout, microstrip sensors, fabricated by Hamamatsu Photonics, as a non-inverting radiation hard silicon detector for the ATLAS tracker upgrade at the super-LHC (sLHC) proposed facility. The bulk radiation damage after neutron and proton irradiations is characterized with the leakage current, charge collection and full depletion voltage. The detectors should provide acceptable signal, signal-to-noise ratio exceeding 15, after the integrated luminosity of 6000 fb−1, which is twice the sLHC integrated luminosity goal.

/pdf/testing-of-bulk-radiation-damage-of-n-in-p-silicon-sensors-15vcakysbt.pdf

Testing of bulk radiation damage of n-in-p silicon sensors for very high radiation environments

Silicon sensors in next generation hadron colliders will face a tremendously harsh radiation environment. Requirement to study rarest reaction channels with statistical constraints has resulted in a huge increment in radiation flux, resulting in both surface damage and bulk damage. For sensors which are used in a charged hadron environment, both of these degrading processes take place simultaneously. Recently it has been observed in proton irradiated n+-p Si strip sensors that n+ strips had a good inter-strip insulation with low values of p-spray and p-stop doping densities which is contrary to the expected behaviour from the current understanding of radiation damage. In this work a simulation model has been devised incorporating radiation damage to understand and provide a possible explanation to the observed behaviour of irradiated sensors.

https://iopscience.iop.org/article/10.1088/1748-0221/9/04/P04007/pdf

Combined effect of bulk and surface damage on strip insulation properties of proton irradiated n+-p silicon strip sensors

We are developing n+-in-p, p-bulk and n-readout, microstrip sensors as a non-inverting radiation hard silicon detector for the ATLAS Tracker Upgrade at the super LHC experiment. The surface radiation damages of the sensors fabricated by Hamamatsu Photonics are characterized on the interstrip capacitance, interstrip resistance and punch-through protection evolution. The detector should provide acceptable strip isolation, exceeding the input impedance of the signal readout chip ∼1 kΩ, after the integrated luminosity of 6 ab−1, which is twice the luminosity goal.

/pdf/testing-of-surface-properties-pre-rad-and-post-rad-of-n-in-p-36kukcarfd.pdf

Testing of surface properties pre-rad and post-rad of n-in-p silicon sensors for very high radiation environment

Bonded silicon-on-insulator (SOI) wafers have the capability of realizing monolithic pixel devices, where the silicon resistivity is optimized separately for the electronics and detector parts. Using UNIBOND wafers, we are developing monolithic pixel devices fabricated with OKI Semiconductor 0.20 μm FD-SOI technology. A set of PMOS and NMOS transistors were irradiated with protons in order to investigate the total ionization dose effect in transistor operation. We evaluated also the devices with a back-gate control electrode added underneath the buried oxide layer. Primary radiation effect appears in transistor threshold shifts, which can be explained by charge traps in the oxide layers and charge states created at the silicon–oxide boundaries. We discuss the possibility of TCAD simulation for evaluation of the charge densities.

/pdf/radiation-effects-in-silicon-on-insulator-transistors-with-3m9lsmvgp4.pdf

Radiation effects in silicon-on-insulator transistors with back-gate control method fabricated with OKI Semiconductor 0.20 μm FD-SOI technology

Anticipating the requirement for highly radiation-tolerant silicon microstrip sensors suitable for the SLHC application, we have fabricated n-in-p microstrip sensors in p-FZ and p-MCZ industrial wafers which we then irradiated with 70 MeV protons. Studies were made of the leakage current, onset of microdischarge, body capacitance, charge collection efficiency, and n-strip isolation at the fluences of nil, 0.7 10 14 , and 7 10 14 1-MeV neutrons equivalent (neq)/cm 2 . The bias and edge structure achieved holding the bias voltages up to 1000 V. The full depletion voltages were about 160, 250, and 600 V in the p-FZ and 1190, 500, and 840 V in the p-MCZ at nil, low, and high fluences, respectively. The radiation damage helped to reduce the density of electron accumulation layer. The strip isolation in the p-MCZ sensors was found to be much better than in the p-FZ sensors; even the no-isolation structure isolated the strips at nil fluence at bias voltage above 50 V. The lower density of electron accumulation layer in the p-MCZ could be attributed to an order less interface trap density in the / 10 0S surface than that of / 11 1S, the negative potential in the inter-strip region by the bias voltage, and the possible effect of high oxygen content in the MCZ bulk. r 2007 Elsevier B.V. All rights reserved. PACS: 29.40.W; 81.40.W

/pdf/p-bulk-silicon-microstrip-sensors-and-irradiation-20f0q612kg.pdf

p-Bulk silicon microstrip sensors and irradiation

Radiation tolerance up to 1015 1-MeV neq/cm2 is required for the silicon microstrip sensors to be operated at the Super LHC experiment. As a candidate for such sensors, we are investigating non-inverting n+-on-p sensors. We manufactured sample sensors of 1 times 1 cm in 4" and 6" processes with implementing different interstrip electrical isolation structures. Industrial high resistive p-type wafers from FZ and MCZ growth are tested. They are different in crystal orientations lang100rang and lang111rang with different wafer resistivities. The sensors were irradiated with 70-MeV protons and characterized in views of the leakage current increase, noise figures, electrical strip isolation, full depletion voltage evolution, and charge collection efficiency.

/pdf/development-of-radiation-hard-rm-n-on-p-silicon-microstrip-2hj0thm3dl.pdf

Development of Radiation Hard ${\rm N}^{+}$ -on-P Silicon Microstrip Sensors for Super LHC

The silicon microstrip detector type with n + readout fabricated on p bulk, n + -on- p , is a candidate to be operational in radiation environments much severer than in LHC We characterized n + -on- p detectors which were irradiated up to 11 × 10 14 protons / cm 2 10 years ago The noise level and charge collection were evaluated using the ATLAS SCT readout electronics system Radiation-induced increase in the noise and loss in the charge collection are not significant The charge collection is not degraded in any particular point in the inter-strip region when the detector is operated under partial depletion

/pdf/performance-of-irradiated-n-on-p-silicon-microstrip-sensors-2ybceys3om.pdf

Performance of irradiated n+-on-p silicon microstrip sensors

Based on the ATLAS SCT experience, hybrid and module designs of a short strip silicon detector for an upgraded ATLAS inner tracker for the super LHC have been pursued. At the super LHC, which provides 10 times more intense beam collisions than the LHC, the detectors envisage a very high rate operation in a much harsher radiation environment. Immediate concern is an increase of leakage current due to a radiation damage, which may induce a catastrophic break down of a thermal runaway. We have deduced a simple model for the thermal runaway, which can be conveniently utilized for the module designs. The thermal runaway model was verified by comparing with the corresponding FEM thermal analyses. The upgraded module is structurally similar to the present SCT barrel module. Two rectangular sensors, each of 12:5 � 6: 4c m 2 , are sandwiched along with a thermo-mechanical baseboard to provide two-dimensional space points. A one-piece wrap-around hybrid bridged over the sensors serves both the top and bottom sensors. Mounting and cooling schemes also follow the present barrel SCT designs with necessary modifications and improvements. r 2007 Elsevier B.V. All rights reserved. PACS: 29.40.Gx; 29.40.Wx; 61.80.� x; 61.82.Fk

http://hep-www.px.tsukuba.ac.jp/~hara/publication/NIM579_806.pdf

Hybrid and module designs for ATLAS silicon tracker upgrade for super LHC

Radiation tolerance up to 1015 1-MeV neq/cm2 is required for the silicon microstrip sensors to be operated at the Super LHC experiment. As a candidate for such sensors, we are investigating non-inverting n+-on-p sensors. We manufactured sample sensors of 1 times 1 cm in 4" and 6" processes with implementing different interstrip electrical isolation structures. Industrial high resistive p-type wafers from FZ (float zone) and MCZ (magnetic Czochralski) growth are tested. They are different in crystal orientations and with different wafer resistivities. The sensors were irradiated with 70-MeV protons and evaluated on the leakage current increase, noise figures, electrical strip isolation, full depletion voltage evolution, and charge collection efficiency.

/pdf/development-of-radiation-hard-n-on-p-silicon-microstrip-3aghwif9fy.pdf

K. Inoue

Papers

p-Bulk silicon microstrip sensors and irradiation

Development of Radiation Hard ${\rm N}^{+}$ -on-P Silicon Microstrip Sensors for Super LHC

Performance of irradiated n+-on-p silicon microstrip sensors

Hybrid and module designs for ATLAS silicon tracker upgrade for super LHC

Development of radiation hard N + -on-P silicon microstrip sensors for super LHC