High-resolution CMOS particle detectors: design and test issues

In this paper, we discuss some issues related to the design, implementation and test of a CMOS active pixel sensor chip (RAPS01), developed in the framework of RAPS (Radiation Active Pixel Sensors) INFN project. Two different basic pixel schemes have been proposed The first one is based on a standard Active Pixel Sensor (APS) architecture, while a second architecture, named Weak Inversion Pixel Sensor (WIPS) exploits a different circuitry which allows for "sparse" access mode and thus for speeding-up the read-out phase. Device simulation has been extensively used to estimate the photodiode response for different technologies (thus addressing selection of the silicon foundry). Chip fabrication has been completed and a preliminary test phase has been performed. A suitable test environment has been devised and test strategies have been planned Future work is also outlined, aimed at the fabrication of a second version of the chip, more effectively integrating smart circuitry.