Radiation hardness of small-pitch 3D pixel sensors up to a fluence of 3×10¹⁶ n_eq/cm²

Abstract

A : Small-pitch 3D silicon pixel detectors have been investigated as radiation-hard candidates for the innermost layers of the HL-LHC pixel detector upgrades. Prototype 3D sensors with pixel sizes of 50×50 and 25×100 µm 2 connected to the existing ATLAS FE-I4 readout chip have been produced by CNM Barcelona. Irradiations up to particle fluences of 3 × 10 16 n eq /cm 2 , beyond the full expected HL-LHC fluences at the end of lifetime, have been carried out at Karlsruhe and CERN. The performance of the 50×50 µm 2 devices has been measured in the laboratory and beam tests at CERN SPS. A high charge collected and a high hit efficiency of 98% were found up to the highest fluence. The bias voltage to reach the target efficiency of 97% at perpendicular beam incidence was found to be about 100 V at 1.4 × 10 16 n eq /cm 2 and 150 V at 2.8 × 10 16 n eq /cm 2 , significantly lower than for the previous IBL 3D generation with larger inter-electrode distance and than for planar sensors. The power dissipation at -25 • C and 1.4 × 10 16 n eq /cm 2 was found to be 13 mW/cm 2 . Hence, 3D pixel detectors demonstrated superior radiation hardness and were chosen as the baseline for the inner layer of the ATLAS HL-LHC pixel detector upgrade. K: Particle tracking detectors, HL-LHC upgrade, 3D silicon pixel detectors, Radiationhard detectors A X P : 1805.10208

Study of small-cell 3D silicon pixel detectors for the high luminosity LHC

“…In a future characterization, we plan to irradiate these sensors with protons to assess their robustness to irradiation and therefore their adequacy for the high luminosity upgrades of the LHC vertex detectors. A recent study [11] of small pitch 3D pixels irradiated up to a fluence of 3 × 10 16 n eq /cm 2 shows that the 3D technology is suitable for the inner layers of HL-LHC vertex detectors.…”

Radiation-tolerant Silicon Detectors for the LHC Phase-II Upgrade and Beyond: Review of RD50 Activities

“…This connects the required drift distance for charge carriers to the pitch of the columns, instead of the bulk thickness in a planar device. Therefore the collection of a sufficiently large signal is less affected by trapping and recombination centers formed during irradiation of the device, ensuring very high efficiencies and resolution even at HL-LHC fluences ( Fig.1b) [16,17]. In addition, shorter drift distances, in combination with a high electric field between the electrodes, also lead to faster drift times, which enables timing resolution down to around 75 ps with unirradiated 3D sensors [18].…”

“…3D sensors have already seen use in the insertable barrel pixel layer in the ATLAS inner tracker, and are included in the inner layers of both CMS and ATLAS Phase-II upgrade designs [2,3]. Current research in 3D sensors is focusing on small-cell sensors to meet future requirements for finer granularity in vertexing detectors, and to improve the understanding signal formation and properties for different particle track angles especially in highly-irradiated sensors [17,18,19].…”

“…a) Left: Schematic cross-section of a small-cell 3D sensor[19], b) right: Hit efficiency as function of bias voltage for an irradiated 3D sensor[17].…”

Characterization of FBK small-pitch 3D diodes after neutron irradiation up to 3.5 × 1016 neq cm−2

“…In the former the basic 3D cell is 25×50 µm 2 with L~28 µm, in the latter L is much larger (~51 µm). Sensors were irradiated with neutrons at the TRIGA Mark II reactor at JSI (Ljubljana, Slovenia) to three different fluences: 1×10 16 , 2×10 16 , and 3.5×10 16 neq cm -2 . Devices were irradiated without bias (i.e., with floating terminals).…”