DMAPS: a fully depleted monolithic active pixel sensor - analog performance characterization

Abstract

Monolithic Active Pixel Sensors (MAPS) have been developed since the late 1990s based on silicon substrates with a thin epitaxial layer (thickness of 10-15 $\mu$m) in which charge is collected on an electrode, albeit by disordered and slow diffusion rather than by drift in a directed electric field. As a consequence, the signal is small ($\approx$ 1000 e$^-$) and the radiation tolerance is much below the LHC requirements by factors of 100 to 1000. In this paper we present the development of a fully Depleted Monolithic Active Pixel Sensors (DMAPS) based on a high resistivity substrate allowing the creation of a fully depleted detection volume. This concept overcomes the inherent limitations of charge collection by diffusion in the standard MAPS designs. We present results from a test chip EPCB01 designed in a commercial 150 nm CMOS technology. The technology provides a thin (50 $\mu$m) high resistivity n-type silicon substrate as well as an additional deep p-well which allows to integrate full CMOS circuitry inside the pixel. Different matrix types with several variants of collection electrodes have been implemented. Measurements of the analog performance of this first implementation of DMAPS pixels will be presented.