Abstract
3D silicon sensors with active edges where the electrodes penetrate through the entire silicon substrate have been investigated in high energy physics applications in recent years. The key to 3D fabrication is the use of plasma micro-machining to etch narrow deep vertical openings that allow dopants to be diffused in and form electrodes of p-i-n junctions. The use of such micro-machining is an emerging technology in the fabrication of such radiation sensors. Several leading institutions in semiconductor fabrication, both in Europe and in the US, have collaborated in an attempt to bring the maturity of 3D sensors to a level suitable to satisfy the needs of high energy physics research. These efforts include increasing detector size, optimization of compatibility with readout electronics and improvement in overall fabrication yield. The results so far are promising and physicists are now encouraged to explore the use of 3D sensors in a wider field of nuclear related science and technologies outside high energy physics. Sensors with 3D electrodes provide a strong electric field in the p-i-n junction and reduce the charge trapping probability of generated charge carriers by incident radiation making them more radiation hard. Moreover, this structure can provide higher spatial resolution, low operating voltage, better irradiation stability, improved regular response and radiation hardness for both mini-dosimetry in conventional radiotherapy and micro-dosimetry for hadron therapy. The resulting 3-dimensional structures, derived from micro-machining, can further improve the current status of micro-dosimetry by providing well-defined sensitive volumes to better mimic biological cells. This presentation will give a summary of the development of 3D sensors in the past year and their suitability in dosimetry for both conventional and hadron therapy. An international collaboration of leading institutions is currently underway a research project strongly funded by the Norwegian Research Council, which will investigate the performance of 3D microdosimeters.
