Status and perspectives of deep N-well 130nm CMOS MAPS

Deep N-Well (DNW) MAPS were developed in two different flavors to approach the specifications of vertex detectors in dissimilar experimental environments such as the Super B-Factory and the ILC. The first generation of MAPS with on-pixel data sparsification and time stamping capabilities is now available and was tested in a beam for the first time in September 2008. These devices are fabricated in a commercial 130 nm CMOS process, and the triple well structure available in such an ultra-deep submicron technology is exploited by using the deep N-well as the charge-collecting electrode. Because of the high integration density of such a technology, complex digital functions can be included in each pixel, implementing a sparsified readout architecture of the pixel matrix with time stamping. This paper reviews the features of the "ILC class" and "SuperB class" MAPS devices, discussing their different design in terms of pixel pitch, analog signal processing, and digital readout architecture. For SuperB, a data-driven, continuously operating readout scheme was adopted along with a macropixel matrix arrangement, whereas for the ILC the matrix is read out in the long inter-train period. In both versions, the address of hit pixels is transmitted off-chip along with the time stamp. The experimental performance of the chips provides an assessment of the Deep N-Well MAPS potential in view of future applications. The paper also discusses the way forward in the development of these devices, outlining the issues that have to be tackled to design full size Deep N-Well MAPS for actual experiments. These sensors could take advantage from technological advances in microelectronic industry, such as vertical integration. The impact of these new technologies on the design and performance of DNW pixel sensors could be large, with potential benefit for various device features, from the charge collection properties to the digital readout architecture.