Optimization of tracking performance of CMOS monolithic active pixel sensors

CMOS monolithic active pixel sensors (MAPS) provide an attractive solution for high precision tracking of minimum ionizing particles. A thin, moderately doped, undepleted silicon layer is used in these devices as a detector active volume with the readout electronics implemented on top of it. A new MAPS prototype has been fabricated using recently available AMS 0.35 μ OPTO process, featuring thick epitaxial layer. A systematic study of tracking performance of that prototype using high-energy particles beam is presented in this work. Noise performance, signal amplitude from minimum ionizing particles, detection efficiency, spurious hit suppression and spatial resolution are shown as a function of the readout pitch and the charge collecting diode size. A test array with a novel readout circuitry is included in the design. The circuit consists of a front-end voltage amplifier, capacitively coupled to the charge collecting diode and followed by two analog memory cells. This architecture implements an on-pixel correlated double sampling method, allowing for optimization of integration time independently of full frame readout and reducing pixel-to-pixel output signal dispersion. First measurements using this structure are presented.