RD50-MPW: a series of monolithic High Voltage CMOS pixel chips with high granularity and towards high radiation tolerance

A series of monolithic High Voltage CMOS (HV-CMOS) pixel sensor prototypes have been developed by the CERN-RD50 CMOS working group for potential use in future high luminosity experiments. The aim is to further improve the performance of HV-CMOS sensors, especially in terms of pixel granularity, timing resolution and radiation tolerance. The evaluation of one of this series, RD50-MPW3, is presented in this contribution, including laboratory and test beam measurements. The design of the latest prototype, RD50-MPW4, which resolves issues found in RD50-MPW3 and implements further improvements, is described.