Combined Bulk and Surface Radiation Damage Effects at Very High Fluences in Silicon Detectors: Measurements and TCAD Simulations

Abstract

Abstract-In this work we propose a new combined TCAD radiation damage modelling scheme, featuring both bulk and surface radiation damage effects, for the analysis of silicon detectors aimed at the High Luminosity LHC. In particular, a surface damage model has been developed by introducing the relevant parameters (NOX, NIT) extracted from experimental measurements carried out on p-type substrate test structures after gamma irradiations at doses in the range 10-500 Mrad(Si). An extended bulk model, by considering impact ionization and deep-level cross-sections variation, was included as well. The model has been validated through the comparison of the simulation findings with experimental measurements carried out at very high fluences (2×10 16 1 MeV equivalent n/cm 2 ) thus fostering the application of this TCAD approach for the design and optimization of the new generation of silicon detectors to be used in future HEP experiments.

Development of a silicon bulk radiation damage model for Sentaurus TCAD

“…The most recent Perugia model [3] aims to be valid up to fluences of 2 × 10 16 1 MeV n eq /cm 2 and is a natural basis for comparison. Both the model presented here and the Perugia model contain three bulk defect levels and are tuned for -type silicon.…”

“…Differences between the present model and other models with similar range of validity in terms of fluence, in particular the Perugia model [3], are discussed in Section 2.4.…”

“…The model is validated using measurements on irradiated -on-pixel sensors from Hamamatsu Photonics K.K. 3 These sensors have a thickness of 200 μm and a pixel cell size of 55 × 55 μm 2 , and feature -stop isolation between pixels.…”

“…Radiation damage models for Synopsys Sentaurus TCAD, of varying scope, have been developed in the past by different groups [2][3][4][5][6].…”

Small pitch 3D devices

“…As a main outcome of this work, it was predicted that a capacitance of ~50 fF per read-out column and a breakdown voltage higher than 150 V can be achieved before irradiation, good enough for the planned application. As far as the signal efficiency after irradiation is concerned, by implementing into the simulation the new "Perugia" radiation damage model [19], both the 50×50 µm 2 and 25×100 µm 2 (2E) pixel layouts were found to yield very high average values, in the range from 60 to 70% after the largest possible irradiation fluence of 2×10 16 n eq /cm 2 , thus anticipating the excellent radiation tolerance of such devices [17]. In parallel with the design/simulation activity, Si-Si DWB substrates of two different active thicknesses (100 and 130 µm) have been qualified by processing a batch of planar sensors [15,18].…”