Development of tileable silicon photodiodes for X-ray imaging

This thesis describes the research work carried out by the author in Detection Technology, Inc. in the field of large area silicon photodiodes targeted for medical Computed Tomography (CT) imaging. The author established and supervised a research and development team with an overall target of developing tileable detectors for computed tomography. Several different tileable and some semi tileable technologies were studied, developed, prototyped and tested. Most of those technologies have been introduced in this thesis, but the research is still ongoing and further publications are to be expected. Out of the technologies evaluated, the through waver interconnects, especially using the shape of inverted T, was shown to best integrate with photodiodes without sacrificing the good properties of the photodiode for tileability. Other technologies, cathode readout and back side illumination, were also shown to provide basis for manufacturing tileable detector products meeting the requirements of modern CT equipment. The selection of some or all of these technologies to commercial products needs to be based on issues like manufacturability, raw materials and processing costs, achievable yields, etc, ultimate question being, which one of the technologies gives tileability with certain required specifications at lowest total system cost. First commercial products based on this work were released by Detection Technology in 2009.