Intrinsic time resolution of 3D-trench silicon pixels for charged particle detection

Abstract

In the last years, high-resolution time tagging has emerged as a promising tool to tackle the problem of high-track density in the detectors of the next generation of experiments at particle colliders. Time resolutions below 50 ps and event average repetition rates of tens of MHz on sensor pixels having a pitch of 50 μm are typical minimum requirements. This poses an important scientific and technological challenge on the development of particle sensors and processing electronics. The TIMESPOT initiative (which stands for TIME and SPace real-time Operating Tracker) aims at the development of a full prototype detection system suitable for the particle trackers of the next-to-come particle physics experiments. This paper describes the results obtained on the first batch of TIMESPOT silicon sensors, based on a novel 3D MEMS (micro electro-mechanical systems) design. We demonstrate that following this approach, the performance of other ongoing silicon sensor developments can be matched and overcome. In addition, 3D technology has already been proved to be robust against radiation damage. A time resolution of the order of 20 ps has been measured at room temperature suggesting also possible improvements after further optimisations of the front-end electronics processing stage.

Advances in 3D Sensor Technology by Using Stepper Lithography

“…While for HL-LHC applications dedicated timing layers, e.g. based on LGAD sensors, will be added to the ATLAS and CMS detectors [13], for experiments at future colliders, e.g., LHCb and FCC, space and time measurements should be combined in a single device [6]. Small-pitch 3D pixels have been shown to offer good timing resolution, but their ultimate performance is limited by the spatial non-uniformity of the electric and weighting fields within a pixel, limiting the timing resolution [14].…”

“…Leveraging the experience on small-pitch 3D pixels and planar active-edge sensors [22,23], FBK has fabricated one batch of trenched 3D pixels in 2019 within the INFN TIMESPOT project [6]. The batch was made on 6-inch diameter wafers of the same type as those used for the previously mentioned batch 3, with 150μm active layer thickness.…”

“…Note that the depletion voltage is only a few Volts, and the breakdown voltage almost 200 V [17], thus leaving a wide operational margin to operate the pixels with carrier velocity saturation, as requested to enhance the timing performance. The first measurements performed in a beam test on these devices coupled to discrete readout circuits are in fact very promising, showing a timing resolution of about 20 ps [6].…”

“…In the earlier prototypes the columnar electrodes had ∼20 μm diameter and ∼100 μm distance [3]; these values roughly halved in 2010 in 3D sensors for the ATLAS Insertable B Layer (IBL) [4], and are now as small as ∼5 and ∼30 μm, respectively, for the most recent devices aimed at the ATLAS and CMS detector upgrades at the High Luminosity (HL) LHC [5]. In addition, modified 3D designs involving small pixel cells with trenched electrodes have been recently proposed to improve the electric field and weighting field distributions in the active volume, that are essential ingredients for the optimization of timing performance, as required for the future LHCb detector upgrade [6].…”

Fabrication and First Full Characterisation of Timing Properties of 3D Diamond Detectors

“…Firstly, compared to the classical planar geometry, the 3D configuration reduces by about an order of magnitude the charge carrier path towards the electrodes thus reducing the effect of lattice defects induced by radiation. Secondly, the charge collection time is also dramatically reduced down to about 100 ps allowing the realisation of tracking devices with time resolution at the level of 10 ps [3]. The introduction of a precise time information in track hits significantly simplifies the track reconstruction problem, drastically reducing the number of hits that can be associated to a candidate particle trajectory [4].…”