亚微米级CMOS图像传感器的光学性能优化研究

Study on Optimization of Optical Performance for Sub-micron CMOS Image Sensor

图像传感器的量子效率和信号串扰问题是CMOS图像传感器小型化面临的最主要问题之一,当图像传感器尺寸进入亚微米阶段,由于可见光的波长尤其是红光波长非常接近于像素尺寸,会导致像素发生严重的衍射及串扰问题,从而严重影响像素的量子效率和色彩还原能力。为了使像素达到更好的光学性能,基于0.8μm像素结构,优化传统的像素光学隔离挡墙结构,采用金属钨和二氧化硅的叠层挡墙结构,通过仿真优化挡墙的结构比例,使像素的量子效率和串扰问题得到大幅优化。光学仿真和实际测试表明,当挡墙结构中金属钨的比例降低到50%~30%范围时,图像传感器芯片具有最佳的光学性能。

The problem of quantum efficiency and signal crosstalk of image sensor is one of the most important issues for the miniaturization of CMOS image sensor.when the pixel size enters submicron stage,the wavelength of visible light is very close to the pixel size.it will lead to serious diffraction and crosstalk problems,and seriously affect the quantum efficiency and color restoration performance.In order to improve the pixel optical performance,we optimize the traditional pixel optical isolation structure based on 0.8μm pixel.We use metal tungsten and SiO2 stacked structure,and optimize the W/SiO2 ratio through simulation,which greatly improve the pixel quantum efficiency and crosstalk problem.Optical simulation and optical test both show that,when the proportion of tungsten in the isolation structure reduced to 50%~30%,the image sensor has the best optical performance.