MuPix8 - A large-area HV-MAPS chip

Abstract

The architecture of the first large area $2\times 1\, \text{cm}^2$ MuPix8 prototype, produced in an AMS $180\, \text{nm}$ HV-CMOS process, is presented. The MuPix8 chip is a High Voltage Monolithic Active Pixel Sensor (HV-MAPS) being developed for the Mu3e experiment which will search for the lepton flavour violating decay $\mu^{+} \rightarrow e^{+}e^{-}e^{+}$ with an unprecedented sensitivity of one in $10^{16}$ decays. To reach this sensitivity goal an ultralight-pixel tracker with $10^{-3}$ radiation lenghts per tracking layer and high rate capability is being built. The Mu3e pixel tracker will be based on MuPix chips with a thickness of $50\, \text{\textmu m}$ and a pixel size of $80\times80\,\mu\text{m}^2$. The hits are readout by on-chip state machines and the data are streamed out via four $1.25\, \text{Gbit/s}$ data links. The MuPix8 is the first prototype which fulfills all above requirements and features the full column length of the final chip. In addition, it implements circuitry providing pulse height information, thus allowing for timewalk suppression aiming at a time resolution of $10\, \text{ns}$ or better.