VTT has developed a straightforward and fast process to fabricate edgeless (active edge) microstrip and pixel detectors on 6 in. (150 mm) wafers. The process avoids all slow process steps, such as polysilicon growth, planarization and additional ICP-etching. We have successfully fabricated 150 μm thick p-on-n and n-on-n prototypes of edgeless detectors having dead layers at the edge with a thickness below a micron. Fabrication was done on high resistivity n-type FZ-silicon wafers. The prototypes include 5×5 and 1×1 cm2 edgeless microstrip detectors with DC-, FOXFET- and PT-couplings. In addition 1.4×1.4 cm2 Medipix2 edgeless pixel detectors were also fabricated.
This paper presents leakage current, capacitance and breakdown voltage measurements of different DC-coupled microstrip designs and compares them with respect to the active edge distance and polarity of the detector. The active edge distances were 20, 50 and 100 μm from the strips. Electrical characterization of these detectors on the wafer level gave promising results. A good uniformity in the measured parameters was observed for the inner strips. The parameters of the adjacent strip to the edge showed a dramatic dependence on the active edge distance. Leakage current and capacitance of the inner microstrips were 50–70 nA/cm2 and 580–660 pF/cm2 at, respectively, 40 V reverse bias for the p-on-n. For the n-on-n design these parameters were 116–118 nA/cm2 and 930–960 pF/cm2. The breakdown voltages were above 150 V for p-on-n prototypes and increased as a function of active edge distance. To fully deplete the p-on-n detectors required twice as much reverse bias as was needed for the n-on-n detectors, i.e. 13–28 V.
|Journal||Nuclear Instruments and Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|
|Issue number||Suppl. 1|
|Publication status||Published - 2011|
|MoE publication type||A1 Journal article-refereed|
|Event||11th International Workshop on Radiation Imaging Detectors (IWORID) - Prague, Czech Republic|
Duration: 29 Jun 2009 → 3 Jul 2009
- solid-state detector
- silicon detector
- edgeless detector
- active edge detector
- ion- implantation