Radiation Detector Activity at VTT

VTT is a nonprofit research organization employing about 2700 persons. It is the largest R&D institution in Northern Europe and is part of the Finnish innovation system. VTT has a two decades experience, since 1989, on manufacturing and designing silicon radiation detector structures. The activities cover a range of industrial devices as well as the devices for the physics experiments. VTT is one of the forerun-ners for the 3D and edgeless detector technologies. Recently VTT has done processing development for the compound semiconductor materials, aspecially CdTe patterning and pixelization. An overview on the radiation detector activity at VTT is given and a Through-Wafer-Interconnect (TWI) technology is introduced. The state-of-the-art processing on 6” (150 mm) wafer relies on utiliza-tion of bonded support wafer in the final detector or during the fabrication of the detector, allowing fab-rication of very thin microstrip detectors, and trench etching through the wafer during the process of the 3D and edgeless detectors. The first thin detectors fabricated on Silicon-On-Insulator (SOI) wafers had a microstrip geometry and were designed for the Neutral Particle Analyser (NPA) setup for JET. This design overcomes the issues faced with the current a scintillator-photomultiplier combination that suffers from the background radiation and the particle identification is possible only for the energetic ions. The edgeless detector design offers some attractive properties for the high energy physics experiments and medical imaging studies. The processing is done on the bonded support wafer, which is removed at the end of the fabrication. We present here a new straight forward and fast way to fabricate these detec-tors that is realized using a side wall ion-implantation and non-planar lithography. The first results of the prototypes are presented. The TWI-technology has been developed for the large imaging matrices. The special application in the view is the computed tomography in the field of medical imaging. The TWI-technology has also been adopted for the industrial applications.