Fully Depleted Pinned Photodiode CMOS Image Sensor With Reverse Substrate Bias

摘要

A new pixel design using fully depleted pinned photodiode (PPD) in a 180-nm CMOS image sensor (CIS) process has been developed and the first experimental results from a test chip are presented. The sensor can be fully depleted by means of reverse bias applied to the substrate, and the principle of operation is applicable to very thick sensitive volumes. Additional n-type implants under the in-pixel p-wells have been added to the manufacturing process in order to eliminate the large parasitic substrate current that would otherwise be present in a normal device. The new design shows the same electro-optical performance as the PPD pixel it is based on, and can be fully depleted without significant leakage currents. This development has the potential to greatly increase the quantum efficiency of scientific PPD CIS at near-infrared and soft X-ray wavelengths.