Process Quality Control for HGCAL at Florida State University

The HL-LHC project aims to increase the instantaneous luminosity of the LHC by a factor of 5, in order to extend the potential of the LHC for new discoveries. More proton-proton collisions will increase the number of additional interactions per bunch crossing, referred to as pile-up (PU), and will expose the detectors to a greatly increased amount of radiation damage. For CMS, this means the existing endcap calorimeters will need to be replaced, which has prompted the proposal of a new high-granularity sampling calorimeter, called HGCAL. The active elements of HGCAL are 8-inch hexagonal silicon sensors; the final calorimeter will contain ~ 30,000 such sensors. For proper performance of HGCAL, it is important that the characteristics of the sensors be well-understood, and consistent throughout production. Process Quality Control (PQC) takes advantage of the fact that the hexagonal sensors are cut from circular wafers, by implementing test structures on the unused material. These test structures can be used to measure properties of the material (i.e. oxide type, surface generation velocity, etc.) and are therefore very sensitive to differences between batches of sensors. Hence we will present the experimental setup for testing PQC at FSU, as well as preliminary results.