基于自对准技术的4管像素寄生电容建模与分析

Modeling and Analysis of Parasitic Capacitance in 4-Transistor Pixels Based on Self-Alignment Technique

转换增益是微光CMOS图像传感器的重要参数,转换增益的提高有助于提升图像传感器的信噪比,进而提升灵敏度和成像质量。由于转换增益与像素的寄生电容成反比关系,为有效提升转换增益,提出了一种基于自对准技术的4管有源像素寄生电容的二维物理模型。该模型建立了像素寄生电容与注入条件之间的关系,其中包括注入剂量、注入能量和复位电压,该模型的计算结果与TCAD仿真结果具有较高的一致性,二者之间的方差小于0.0028 fF2,验证了该模型的准确性。该模型能应用于高性能图像传感器尤其是高灵敏度微光图像传感器的设计和优化中。

Conversion gain is an important parameter of low-light CMOS image sensors,and realizing improvements in conversion gain helps to enhance their signal-to-noise ratio,which in turn improves their sensitivity and imaging quality.Because the conversion gain is inversely related to the parasitic capacitance of a pixel,this paper proposes a twodimensional physical model of the parasitic capacitance of a 4-transistor active pixel based on the self-alignment technique to effectively improve the conversion gain.The proposed model establishes the relationship between pixel parasitic capacitance and injection conditions,which include injection dose,injection energy,and reset voltage.The calculated results of the model are in good agreement with the TCAD simulation results,and the variance between them is less than 0.0028 fF2,verifying its accuracy.The proposed model can be applied to the design and optimization of high-performance image sensors,especially high-sensitivity low-light image sensors.