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Radiation detectors for imaging applications

There is currently a great interest in building large imaging panels from individual pixel detector tiles. The pixel matrix should be continuous over the tiles, with no dead (pixel free) areas. An absence of dead pixels results in more precise and reliable images. VTT provides key technologies that can ultimately be integrated together in order to assemble state-of-the-art detector panels.

VTT is a forerunner in edgeless sensor manufacturing technology for silicon based strip and pixel detectors. Thanks to our mature flip chip process and other complementary technologies, VTT is able to provide integrated 3D packaging solutions for pixel detectors.

Device integration 

The solder based flip chip process has been used to assemble hybrid pixel detectors made out of different materials (Silicon, Cadmium Telluride, Gallium Arsenide etc.). In order to minimize thermal stresses, thermally induced degradation of sensor material, and to increase the reliability of the solder joints, we developed a low temperature (150 degrees Celsius) indium-tin soldering technology. To date the flip chip process has been carried out at the die-level, but the future focus is wafer-level processes such as chip-to-wafer and wafer-to-wafer bonding. 

For further integration, VTT offers polysilicon and Cu Through Silicon Via (TSV) processes.

Ultra thin silicon strip and pad detectors

Patterned ultra thin detectors are used in light ion detection with increased signal-to-noiseratio. Patterned membrane detectors for back side illumination are also available. The advantages of these detectors are good signal-to-background separation, low voltage operation and low power consumption, low sensitivity to voltage variation, and good radiation tolerance. Some applications of the technology include, for example, high energy physics, medical imaging and dosimetry in radiation therapy.

Edgeless and 3D silicon detectors

Edgeless detectors, both large area pixel and strip types, have minimal inactive regions at the edges. 3D geometry can be used to increase detector radiation hardness.

There are several advantages to the 4-side tileable detector, including a straightforward process resulting in approximately one micrometer of inactivity along the edge. 3D detector geometry provides radiation hardness, can recharge quickly, fast charge collection and operation with a low voltage power consumption.

Some applications include high energy physics, medical imaging, crystallography and mammography.