Resolution limits achievable with CMOS front-end in X- and γ-ray analysis with semiconductor detectors

During the past 15 years, the CMOS technologies have provided the most widely followed approach to signal processing with microstrip detectors. In more recent times, CMOS front-end systems have been developed to acquire and process signals from pixel detectors. During the past few years, the favor toward CMOS processes in their applications in the broad area of detector signal processing has been enhanced by the technological advancement known as device scaling and by two aspects connected to it. One is the shrinking in channel length L into the deep submicron region. The second one is the related reduction in the gate-oxide thickness tox to a few nm. The reduction in tox has, as a consequence of primary importance, a decreased 1/f-noise contribution to the equivalent noise charge (ENC). The thinner gate-oxide and the shrinking in gate length, in some regions of operations, concur to increase the transconductance of the device, which results in a smaller ENC contribution from channel thermal noise. The goal of the present paper is to address the question of whether or not the most advanced CMOS processes may meet the requirements set by high resolution, high dynamic range applications like the energy-dispersive photon analysis with solid-state detectors of comparatively large capacitance.