Comparison of Pinning Voltage Estimation Methods in Pinned Photodiode CMOS Image Sensors

摘要

The pinning voltage is a key design parameter in Pinned Photodiode CMOS Image Sensors which significantly affects the device performances and which is often used by manufacturers to monitor production lines and for the optimization of technological processes. This work presents a comparative study of pinning voltage estimation methods, which are based both on electrical measurements performed on isolated test structures (or on test structures arrays) and on in-pixel measurements. It is shown, with the support of simulations and experimental measurements, that not all the estimation methods provide an absolute value of the pinning voltage. Moreover, this work demonstrates that the commonly accepted theoretical definition of the pinning voltage does not correspond to the physical parameter which is measured with the existing methods.