Depleted Fully Monolithic Active CMOS Pixel Sensors (DMAPS) in High Resistivity 150~nm Technology for LHC

Abstract

Depleted monolithic CMOS active pixel sensors (DMAPS) have been developed in order to demonstrate their suitability as pixel detectors in the outer layers of a toroidal LHC apparatus inner tracker (ATLAS ITk) pixel detector in the high-luminosity large hadron collider (HL-LHC). Two prototypes have been fabricated using 150 nm CMOS technology on high resistivity (> 2 k$\Omega$ $cm^2$) wafers. The chip size is equivalent to that of the current ATLAS pixel detector readout chip. One of the prototypes is used for detailed characterization of the sensor and the analog readout of the DMAPS. The other is a fully monolithic DMAPS including fast readout digital logic that handles the required hit rate. In order to yield a strong homogeneous electric field within the sensor volume, thinning of the wafer was tested. The prototypes were irradiated with X-ray up to a total ionization dose (TID) of 50 Mrad and with neutrons up to non-ionizing energy loss (NIEL) of $10^{15}$ $n_{eq}/cm^2$. The analog readout circuitry maintained its performance after TID irradiation, and the hit-efficiency at > $10^7$ noise occupancy was as high as 98.9 % after NIEL irradiation.