Study of the design optimization of AC-coupled single-sided silicon strip sensors

The high-intensity rare-isotope accelerator, RAON, will be constructed for nuclear physics research in Korea. AC-coupled single-sided silicon strip detectors (SSSDs) are being investigated for use in the Si-CsI detector of a large acceptance multi-purpose spectrometer to measure the energies of various isotopes. To determine the optimal design, four SSSD design parameters were examined in this study, namely the ratio of p⁺ implant width to strip pitch (I/P), the width of the metal layer, the presence of an n⁺-edge field shaper (FS), and the distance between the guard-ring and sensor edge (DGS). The designed detectors were fabricated on high resistivity n-type silicon wafers of 500 μm thickness. The SSSDs had the strip pitch of 730 μm and 32 readout strips in each, and the size of the sensors was 40.0 × 25.5 mm². In terms of the leakage current and production yield, the noise improved by up to 30%when the I/P ratio was 0.4, the metal layer was wider than the p⁺ implantation, and the DGS with n⁺-edge FS was twice the sensor thickness. The signal-to-noise ratio of the SSSD with the design parameters that provided the optimal leakage current and coupling capacitance was measured to be 29.1 using a ⁹⁰Sr radioactive source and commercial electronics.