Design and characterisation of the JadePix-3 CMOS pixel sensor

The JadePix-3 CMOS pixel sensors have been developed and studied with a design optimised for a high position resolution of 3μm, which is one of the key requirements for the physics programmes at the Circular Electron-Positron Collider (CEPC) experiments. The sensors are orientated to the vertex detector for the experiments at the proposed future CEPC. The sensors with high-resistance substrates were produced using Tower Semiconductor’s 180 nm CMOS Imaging Sensor (CIS) process, which feature small sensing diodes, low power analogue front-ends with an in-pixel discriminator, and a rolling shutter readout scheme to minimise the pixel pitch. In the sensors, the pixel matrix of 512 rows × 192 columns is divided into four sectors with varied pixel size (16μm × 26μm and 16μm ×23.11μm) and circuit design. Electrical pulse tests reveal that for various sectors, the minimum thresholds range from 90 to 140 e, with a noise hit rate below an upper limit of 1 × 10−10/frame/pixel. An infra-red laser beam and a radioactive source of 90Sr have been used to characterise the sensors. The tests show that with the equivalent threshold charge fixed to 220 e−, a position resolution between pitch/212 and pitch/12 can be achieved by tuning the laser power for a signal charge between 440 e− and 880 e−. The measured power consumption is 127 mW for the JadePix-3 sensor and 87 mW/cm 2 when extrapolated to a large sensor of 1 cm × 2.5 cm.