A new microstrip detector with double-sided readout

A silicon microstrip detector has been developed with 50-μm-pitch strips on both the p- and n-side, using the principle of capacitive coupling between p⁺ diode strips (respectively, n ⁺ strips) and the metallization strips which connect to the front-end preamplifiers. The detector is biased on both sides via polysilicon resistors connecting each p⁺ or n⁺ line to a common bias bus. To allow ohmic separation at the n-side, the accumulation layer of electrons has to be disrupted between the n⁺ strips. This has been achieved in three different ways: by separate polysilicon lines on thick oxide between two adjacent n⁺ lines to break the conducting accumulation layer by externally induced field depletion or by using the metal lines of the n⁺ strips on thick oxide or on thin oxide. Results on 20×20-mm² test devices are presented. A preliminary analysis of the spatial resolution gives σ=16 μm on both sides. These results demonstrate that double-sided readout Si strip detectors can be used for experiments where spatial resolution in the 10 μm range is needed