Simulations of 3D detectors

Abstract

3D detectors, in which the n and p electrodes are columns etched through the silicon substrates, have proven high radiation tolerance and thus are one of the most suitable candidates for harsh radiation environments, such as vertex detectors. Being the process much more complicated than the planar one, over the years, several simplified 3D families have been studied and fabricated. In this context, TCAD simulations are an excellent tool to predict the behaviour and performance of new detector concepts. In this paper we give an overview of this simulation activity mainly focussing on the 3D FBK technology. We show that it is possible to reproduce also unexpected phenomena, such as the observed charge multiplication in highly irradiated devices.

Impact of the layout on the electrical characteristics of double-sided silicon 3D sensors fabricated at FBK

“…Because of the peculiar geometry of 3D detectors, these simulations must be performed in three dimensions because a bi-dimensional simulation would neglect some critical regions of the device [16]. In order to reduce the computational load, it is possible to exploit the symmetry of the devices by simulating only a quarter of the elementary cell and then scaling the results to the full detector size using the parameters reported in Table 1.…”

FE-I4 pixel readout chip and IBL module

“…The main challenges facing this technology is the higher capacitance and the loss of efficiency at normal incidence associated to the collecting pillar, as well as manufacturability concerns (limited number of vendor available, difficulty to reach high yield, higher costs). Also for this technology must the edges be kept at a minimum size, and this was shown to be possible with the use of so-called ohmic fences, with finally dead area that could be kept below the 200 μm level as well [11]. In the 3D silicon case, two sensor tiles correspond to one module.…”

3D irradiation results

“…Moreover, due to a charge multiplication effect, the signal efficiency is still 70% at 350 V after a fluence of 2×10 16 n eq cm -2 [13]. Note that charge multiplication effects have been observed in 3D-DDTC strip sensors also at lower voltages (in the order of 200 V) after lower radiation fluences (starting from 5×10 14 n eq cm -2 ) [13], [14], and are likely enhanced by the high electric field values at column tips, as suggested by TCAD simulations [15].…”