Processing of ultra-thin silicon sensors for future e+e- linear collider experiments

The e⁺e^- linear collider physics program sets highly demanding requirements on the accurate determination of charged particle trajectories close to the interaction point. A new generation of depleted field effect transistor active pixel sensors with 25 μm pixel size is currently being developed to meet the requirements in the point measurement resolution and multiple track separation. To minimize the influence of the multiple scattering on the impact parameter resolution, the sensors have to be made as thin as possible. This paper presents a technology based on direct wafer bonding and deep anisotropic etching for the production of ultra-thin fully depleted sensors with electrically active back side. PiN diodes with 50 μm thickness have been produced in this way and the results show the feasibility of this approach. The technology is useful for the production of any kind of thin sensors with active back side (strip detectors, pad detectors, etc.). An integrated support frame outside the sensitive area allows for safe handling and mounting of the thin devices.