Fully depleted monolithic active pixel sensors in SOI technology

Full text: Fast monolithic pixel detectors, integrating in the same silicon chip both the sensitive volume and the front-end circuitry, have been the dream of experimental physicists for years. Monolithic pixels are much easier than hybrid detectors in terms of assembly and simplicity, and production cost is lower. Another strong point of monolithic devices is the intrinsic low detector capacitance, as there is no parasitic capacitance introduced by the 'bump-bonding' connection, thus allowing for intrinsic lower power operations. However in traditional monolithic detectors the substrate is usually made by very low resistivity silicon, unsuitable for depletion; charge is hence collected by diffusion in the epitaxial layer, which means an intrinsic low signal (collection thickness is in the order of 10-20 μm), low collection speed, and low resistance to radiation damage, as charge carriers get easily trapped by the radiation induced lattice defects. In the framework of an international collaboration between LBNL, UCSC and INFN, we have developed the first fully depleted Monolithic Active Pixel Sensors (MAPS), using a high resistivity substrate and a commercial Silicon On Insulator technology. The detectors have been widely characterized with high momentum particles at CERN and with low energy X-rays at the Advanced Light Source at LBNL, showing promising performances in terms of noise, spatial resolution and efficiency. (author)