Recent developments on CMOS MAPS for the superB silicon vertex tracker

In the design of the Silicon Vertex Tracker for the high luminosity SuperB collider, very challenging requirements are set by physics and background conditions on its innermost Layer0: small radius (about 1.5 cm), resolution of 10215 mm in both coordinates, low material budget < 1% X0, and the ability to withstand a background hit rate of several tens of MHz/cm^2. Thanks to an intense R&D program the development of Deep NWell CMOS MAPS (with the ST Microelectronics 130 nm process) has reached a good level of maturity and allowed for the first time the implementation of thin CMOS sensors with similar functionalities as in hybrid pixels, such as pixel-level sparsification and fast time stamping. Further MAPS performance improvements are currently under investigation with two different approaches: the INMAPS CMOS process, featuring a quadruple well and a high resistivity substrate, and 3D CMOS MAPS, realized with vertical integration technology. In both cases specific features of the processes chosen can improve charge collection efficiency, with respect to a standard DNW MAPS design, and allow to implement a more complex in-pixel logic in order to develop a faster readout architecture. Prototypes of MAPS matrix, suitable for application in the SuperB Layer0, have been realized with the INMAPS 180 nm process and the 130 nm Chartered/Tezzaron 3D process and results of their characterization will be presented in this paper.