Development of AC-LGAD detector with finer pitch electrodes for high energy physics experiments

Low-Gain Avalanche Diode (LGAD) sensor is one of candidate sensors for the tracker at future hadron collider experiments. To use this sensor as a tracking detector, AC-LGAD sensor is being developed which has both timing and spatial resolutions. In high luminosity environments, good timing resolution (typically 30 ps) together with $\mathcal{O}$(10) ${\mathrm{\mu}}$m spatial resolution helps to reduce pileup effect and reconstruct tracks correctly. By optimizing fabrication parameters, 80 ${\mathrm{\mu}}$m pitch strip and 100 ${\mathrm{\mu}}$m pitch pixel sensors are successfully produced. The signal height (MPV) was 39.26$\pm$0.08 mV and 128.9$\pm$3.3 mV, respectively, for penetrating $\beta$ particles. The observed 60% of signal reduction of the strip sensor is explained by a larger inter-electrode capacitance compared with the pixel sensor. In this paper, we present the performance of fine electrode pitch AC-LGAD sensors including the pulse height and cross-talk of pixel and strip type sensors evaluated using a $\beta$-ray source and the detection efficiency measured in an 800 MeV electron beam.