Charge collection properties of irradiated depleted CMOS pixel test structures

Abstract

Edge-TCT and charge collection measurements with passive test structures made in LFoundry 150 nm CMOS process on p-type substrate with initial resistivity of over 3 k$\Omega$cm are presented. Measurements were made before and after irradiation with reactor neutrons up to 2$\cdot$10${}^{15}$ n${}_{\mathrm{eq}}$/cm${}^2$. Two sets of devices were investigated: unthinned (700 $\mu$m) with substrate biased through the implant on top and thinned (200 $\mu$m) with processed and metallised back plane. Depleted depth was estimated with Edge-TCT and collected charge was measured with ${}^{90}$Sr source using an external amplifier with 25 ns shaping time. Depleted depth at given bias voltage decreased with increasing neutron fluence but it was still larger than 70 $\mu$m at 250 V after the highest fluence. After irradiation much higher collected charge was measured with thinned detectors with processed back plane although the same depleted depth was observed with Edge-TCT. Most probable value of collected charge of over 5000 electrons was measured also after irradiation to 2$\cdot$10${}^{15}$ n${}_{\mathrm{eq}}$/cm${}^2$. This is sufficient to ensure successful operation of these detectors at the outer layer of the pixel detector in the ATLAS experiment at the upgraded HL-LHC.

References in corpus (8)

• Physics potential and experimental challenges of the LHC luminosity upgrade
• CMS Barrel Pixel Detector Overview
• A Monolithic active pixel sensor for ionizing radiation using a 180nm HV-SOI process
• Neutron irradiation test of depleted CMOS pixel detector prototypes
• Studies of irradiated AMS H35 CMOS detectors for the ATLAS tracker upgrade
• Radiation hard pixel sensors using high-resistive wafers in a 150 nm CMOS processing line
• Charge collection properties in an irradiated pixel sensor built in a thick-film HV-SOI process
• Prototype Active Silicon Sensor in 150 nm HR-CMOS Technology for ATLAS Inner Detector Upgrade

Cited by in corpus (7)

• Depleted Fully Monolithic Active CMOS Pixel Sensors (DMAPS) in High Resistivity 150~nm Technology for LHC
• The Monopix chips: Depleted monolithic active pixel sensors with a column-drain read-out architecture for the ATLAS Inner Tracker upgrade
• Pixel Detectors ... where do we stand?
• Charge collection characterisation with the Transient Current Technique of the ams H35DEMO CMOS detector after proton irradiation
• Characterisation of analogue front end and time walk in CMOS active pixel sensor
• Study of neutron irradiation effects in Depleted CMOS detector structures
• Overview of CMOS sensors for future tracking detectors