Abstract
In order to extend its discovery potential, the Large Hadron Collider (LHC) will have a major upgrade (Phase II Upgrade) scheduled for 2022. The LHC after the upgrade, called High-Luminosity LHC (HL-LHC), will operate at a nominal leveled instantaneous luminosity of 5× 1034 cm−2 s−1, more than twice the expected Phase I . The new Inner Tracker needs to cope with this extremely high luminosity. Therefore it requires higher granularity, reduced material budget and increased radiation hardness of all components. A new pixel detector based on High Voltage CMOS (HVCMOS) technology targeting the upgraded ATLAS pixel detector is under study. The main advantages of the HVCMOS technology are its potential for low material budget, use of possible cheaper interconnection technologies, reduced pixel size and lower cost with respect to traditional hybrid pixel detector. Several first prototypes were produced and characterized within ATLAS upgrade R&D effort, to explore the performance and radiation hardness of this technology. In this paper, an overview of the HVCMOS sensor concepts is given. Laboratory tests and irradiation tests of two technologies, HVCMOS AMS and HVCMOS GF, are also given.
Highlights
2.1 HV/high resistivity (HR) sensor concept The High Voltage CMOS (HVCMOS) pixel sensor operating concept is shown in figure 1
5 μm of depleted depth is expected for a 10 Ω·cm substrate resistivity, which corresponds to about 400 electron-hole pairs for a Minimum Ionizing Particles (MIPs)
2.2 HV2FEI4 prototype chip Several HVCMOS prototype sensors have already been produced in 350 nm and 180 nm HV Austria Microsystems technology (AMS) and GlobalFoundries (GF) 130 nm BCDlite technologies
Summary
For the HVCMOS AMS Version (V1), a MIP signal most probable value (MPV) of about 1500 to. (a) Non-irradiated spectra of the AMS V1. (b) Non-irradiated Sr90 MPV vs bias voltage. 1800 e has been measured, depending on sensor bias (30–70 V) and using a Sr-90 source, as shown in figure 3a and figure 3b. Signal to noise ratio of 20 was measured after the irradiation. The Sr-90 MPV signal corresponds to about 1180 e (calibrated by Fe55 source), as shown in figure 4. The observed MPV is larger than expected which indicates collection of non MIP-like beta particles, contribution of charge sharing and that charges collected by diffusion contribute to the signal. The amplifier spectra test results (measured by spectrometer) before irradiation are shown in figure 5. The irradiation study is ongoing and results will be presented elsewhere
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