Pixel Level Characterization of Pinned Photodiode and Transfer Gate Physical Parameters in CMOS Image Sensors

A method to extract the pinned photodiode (PPD) physical parameters inside a CMOS image sensor pixel array is presented. The proposed technique is based on the Tan et al. pinning voltage characteristic. This pixel device characterization can be performed directly at the solid-state circuit output without the need of any external test structure. The presented study analyzes the different injection mechanisms involved in the different regimes of the characteristic. It is demonstrated that in addition to the pinning voltage, this fast measurement can be used to retrieve the PPD capacitance, the pixel equilibrium full well capacity, and both the transfer gate threshold voltage and its channel potential at a given gate voltage. An alternative approach is also proposed to extract an objective pinning voltage value from this measurement.

提出了一种提取CMOS图像传感器像素阵列内钉扎光电二极管（PPD）物理参数的方法。所提出的技术基于Tan等人的钉扎电压特性。这种像素器件的特性描述可以直接在固态电路输出端进行，无需任何外部测试结构。所呈现的研究分析了该特性不同区域所涉及的不同注入机制。结果表明，除了钉扎电压外，这种快速测量还可用于获取PPD电容、像素平衡满阱容量以及给定栅极电压下的传输栅阈值电压及其沟道电位。还提出了一种从该测量中提取客观钉扎电压值的替代方法。