Development of monolithic SOI pixel sensors capable of fine measurements of space and time

Silicon-on-insulator (SOI) for fine measurement of space and time (SOFIST) is designed taking full advantage of advanced SOI monolithic pixel detector fabrication technology to record the charge and time information of hit pixels. The aim is to achieve 3 μm position resolution and ultimately identify the International Linear Collider beam bunches of 554 ns separation. SOFIST Ver. 3 includes full circuits to read out the charge and time for each pixel of size 30×30μm. Its performance is evaluated using a 120 GeV proton beam. The time resolution is evaluated to be 1.92 μs (including calibration error), with an intrinsic time resolution of 1.34–1.55 μs. Additionally, multi-memory readout functionality is successfully examined. With SOFIST Ver. 4, the same functionality is to be realized with a 20×20μm pixel size by 3D stacking. The first chip was successfully tested to image β rays. The connection yield of Au micro-bumps is greater than 99.9%.