Design, Simulation, Fabrication, and Preliminary Tests of 3D CMS Pixel Detectors for the Super-LHC

Abstract

Abstract-The Super-LHC upgrade puts strong demands on the radiation hardness of the innermost tracking detectors of the CMS, which cannot be fulfilled with any conventional planar detector design. The so-called 3D detector architectures, which feature columnar electrodes passing through the substrate thickness, are under investigation as a potential solution for the closest operation points to the beams, where the radiation fluence is estimated to reach 10 16 n eq cm 2 . Two different 3D detector designs with CMS pixel readout electronics are being developed and evaluated for their advantages and drawbacks. The fabrication of full-3D active edge CMS pixel devices with p-type substrate has been successfully completed at SINTEF. In this paper, we study the expected post-irradiation behaviors of these devices with simulations and, after a brief description of their fabrication, we report the first leakage current measurement results as performed on wafer.Index Terms-3D silicon pixel detectors, CMS, radiation hardness, super-LHC.

Electrical Characterization and Preliminary Beam Test Results of 3D Silicon CMS Pixel Detectors

“…If this current is normalized to a single pixel, it falls into the range of ~100 pA to ~2.5 nA. The order of the measured leakage current is consistent with the results of TCAD simulations [6]. The experimental breakdown voltages are well above the depletion voltages, being ~100 V for 4E sensors and ~120 V for 2E sensors.…”

“…A quite small inefficiency should arise from the charge loss associated with ionizations through the bias columns and readout columns. Simulations have shown that about 60 % of the charge generated within the columns can be collected before irradiation [6]. Given that the electrodes constitute about 4 % of the total detector volume for the 2E configuration, the expected overall efficiency is ~ 98.5%.…”

“…After the trenches and holes are filled with polysilicon, they are doped to form the p-type active edge, p-type columns which are used for biasing, and ntype columns that are used for readout. Further information on sensor description and the fabrication process can be found in [6]- [7]. 4 shows the layout of the wafers processed at SINTEF.…”

3D silicon detectors

“…Full 3D pixel sensors compatible with the CMS pixel readout chip have been fabricated by Sintef. 17 The pixel unit cell is 150 µm x 100 µm in size. Two different device configurations have been investigated: four junction columns (4E) and two junction columns (2E) per pixel.…”

Guard Ring Simulations for n-on-p Silicon Particle Detectors

“…Although no experimental data to validate the simulation results of the guard ring structures exist yet, simulations with the same tools and models were able to predict the experimentally observed breakdown behavior of different devices, namely 3D CMS pixel detectors, with a satisfactory accuracy. 85 V and 110 V, respectively, the corresponding simulated breakdown voltages are 80 V and 95 V [18].…”