Development and testing of a radiation-hard large-electrode DMAPS design in a 150 nm CMOS process

Abstract

The LF-Monopix chips are depleted monolithic active pixel sensors that follow the large-electrode design approach and implement a fast synchronous read-out architecture. They are designed in a 150 nm CMOS process and make use of large voltages (>250V) and highly resistive substrates (>2kΩ⋅cm) to collect charge through drift and enhance their radiation hardness.Samples of the first prototype (“LF-Monopix1”) with a thickness of 100μm were irradiated to assess the tolerance of the chip’s substrate and front-end circuitry to the surface and bulk damage doses expected at modern collider experiments. The device remained fully operational, with only a very small gain degradation and an increase in noise by less than 25% after a total ionizing dose of 100Mrad. Efficiency measurements in a sample exposed to a neutron fluence of 1×1015neq/cm2 showed that at least 96% of all minimum ionizing particles going through a fully depleted detector are recorded in less than 25ns. In the latest design (“LF-Monopix2”) the column length was tripled and the pixel pitch reduced by 40% with respect to its predecessor. The chip was successfully thinned down while keeping its breakdown voltage above 400V and achieving a front-end threshold dispersion of ∼100e− after tuning.