Detector Seminar

Fast charge collection in small collection electrode monolithic CMOS sensors

by Magdalena Munker (CERN)




Monolithic CMOS pixel sensors allow for reduced production effort, cost and material budget. Minimising the size of the collection electrode in such designs combines these benefits with a femto-Farad detector capacitance, resulting in a low detection threshold, reduced analogue power consumption and large ratio of signal/noise. The possibility of merging all of these advantages in a single device makes this technology a promising candidate for tracking detectors of future HEP experiments. However, placing the circuitry inside the sensor in a well near the small collection electrode severely affects the charge collection. Motivated by this, a sensor optimisation based on 3D TCAD finite element simulations has been performed. Different concepts with special implant structures have been developed to speed up the charge collection in the monolithic small collection electrode CMOS design. The reduced charge collection time simultaneously results in an increased radiation tolerance, an improved time-stamping capability and a high efficiency for thin sensors, all being fundamental requirements for various future HEP tracking detectors. To assess in detail the improved sensor response for the different concepts, the ATTRACT FASTpix chip has been developed. The FASTpix chip comprises 32 mini-matrices with different hexagonal pixel designs, providing both a precise digital response of a small pixel array and the full analogue information of a few pixels. This seminar introduces the concepts and ideas to accelerate the charge collection in the small collection electrode CMOS sensors, based on 3D TCAD simulations. Further, the performance gain achieved by these concepts is discussed with measurements from different prototype chips and an outlook on future applications is presented.

Zoom connection details are given in the invitation email.

Organized by

Dominik Dannheim (EP-DT)