A two-tier monolithically stacked CMOS Active Pixel Sensor to measure charged particle direction

In this work we present an innovative approach to particle tracking based on CMOS Active Pixel Sensors (APS) layers, monolithically integrated in an all-in-one chip featuring multiple, stacked, fully functional detector layers capable to provide momentum measurement (particle direction) within a single detector by using multiple layer impact point coordinates. The whole system will results in a very low material detector, since each layer can be thinned down to tens of micrometres, thus dramatically reducing multiple scattering issues. To build such a detector, we rely on the capabilities of the CMOS vertical scale integration (3D-IC) 130 nm Chartered/Tezzaron technology, used to integrate two fully-functional CMOS APS matrix detectors, including both sensing area and control/signal elaboration circuitry, stacked in a monolithic device by means of Through Silicon Via (TSV) connections. Such a detector would allow accurate estimation of the impact point of an ionizing particle and of its incidence angle. Two batches of the first chip prototype have been produced and characterized using particle beams (e.g. protons) demonstrating the suitability of particle direction measurement with a single, multiple layers, 3D vertically stacked APS CMOS detector.