Characterization of 3-D-Mesa Silicon Single Strip Detectors for Use in Synchrotron Microbeam Radiation Therapy

The Centre for Medical Radiation Physics (CMRP) has designed and produced novel n-type silicon single strip detectors (SSDs) for use in dosimetry of synchrotron-based microbeam radiation therapy (MRT). In order to address the challenges of dosimetry and quality assurance of these beams, a detector is required with micron-scale spatial resolution, realtime read-out, large dynamic range, and significant radiation hardness. The CMRP first-generation 3-D-Mesa SSD is fabricated in n-SOI technology and involves plasma etching to produce a 10 × 36 × 250 μm
³
sensitive volume (SV) or a 10 × 22.5 × 250 μm
³
SV with all surrounding silicon above the insulating layer removed. The 3-D-Mesa has undergone full electrical characterization and a charge collection study, supported by TCAD simulations to model electric field in the device. The optimal operating bias was found to be -2 V, which produces a dark current of less than 1 nA and 100% charge collection efficiency within the SV. Charge collection is observed at greater biases from the silicon bridge under the Al bus that electrically connects the SV of the SSD to the readout pad. The reasons for this are discussed and will be addressed in the next generation of the 3-D-Mesa SSD.