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 have been developing a novel radiation-tolerant n+-in-p silicon microstrip sensor for very high radiation environments, aiming for application in the high luminosity large hadron collider. The sensors are fabricated in 6 in., p-type, float-zone wafers, where large-area strip sensor designs are laid out together with a number of miniature sensors. Radiation tolerance has been studied with ATLAS07 sensors and with independent structures. The ATLAS07 design was developed into new ATLAS12 designs. The ATLAS12A large-area sensor is made towards an axial strip sensor and the ATLAS12M towards a stereo strip sensor. New features to the ATLAS12 sensors are two dicing lines: standard edge space of 910 μm and slim edge space of 450 μm, a gated punch-through protection structure, and connection of orphan strips in a triangular corner of stereo strips. We report the design of the ATLAS12 layouts and initial measurements of the leakage current after dicing and the resistivity of the wafers.

/pdf/development-of-n-in-p-large-area-silicon-microstrip-sensors-2ud32s38az.pdf

Development of n + -in-p large-area silicon microstrip sensors for very high radiation environments - ATLAS12 design and initial results

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

The ATLAS collaboration R&D group “Development of n-in-p Silicon Sensors for very high radiation environment” has developed single-sided p-type 9.75 cm×9.75 cm sensors with an n-type readout strips having radiation tolerance against the 1015 1-MeV neutron equivalent (neq)/cm2 fluence expected in the Super Large Hadron Collider. The compiled results of an evaluation of the bulk and strip parameter characteristics of 19 new non-irradiated sensors manufactured by Hamamatsu Photonics are presented in this paper. It was verified in detail that the sensors comply with the technical specifications required before irradiation. The reverse bias voltage dependence of various parameters, frequency dependence of tested capacitances, and strip scans of more than 23,000 strips as a test of parameter uniformity and strip quality over the whole sensor area have been carried out at Stony Brook University, Cambridge University, University of Geneva, and Academy of Sciences of CR and Charles University in Prague. No openings, shorts, or pinholes were observed on all tested strips, confirming the high quality of sensors made by Hamamatsu Photonics.

Evaluation of the bulk and strip characteristics of large area n-in-p silicon sensors intended for a very high radiation environment

The ATLAS experiment is preparing for the planned luminosity upgrade of the LHC (the super-luminous LHC or sLHC) with a programme of development for tracking able to withstand an order of greater magnitude radiation fluence and much greater hit occupancy rates than the current detector. This has led to the concept of an all-silicon tracker with an enhanced performance pixel-based inner region and short-strips for much of the higher radii. Both sub-systems employ many common technologies, including the proposed “stave” concept for integrated cooling and support. For the short-strip region, use of this integrated stave concept requires single-sided modules mounted on either side of a thin central lightweight support. Each sensor is divided into four rows of 23.82 mm length strips; within each row, there are 1280 strips of 74.5μm pitch. Well over a hundred prototype sensors are being delivered by Hamamatsu Photonics (HPK) to Japan, Europe and the US. We present results of the first 20 chip ABCN25 ASIC hybrids for these sensors, results of the first prototype 5120 strip module built with 40 ABCN25 read-out ASICs, and the status of the hybrids and modules being developed for the ATLAS tracker upgrade stave programme.

Progress with the single-sided module prototypes for the ATLAS tracker upgrade stave

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

S.Martíi Garcia

Papers

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