Investigation of Image Sensors for Ultra High Resolution Imaging Systems

(1)提出了一种新型光电二极管来提高固态图像传感器的电荷处理能力。这种光电二极管包括一个N^+侧壁，该侧壁包围了带有垂直溢流漏的传统光电二极管的电荷条带区。通过三维数值分析，分析了该二极管的工作特性和性能。我们发现，在电荷存储开始时，在沟道停止和N^+侧壁的边界附近产生的突然的电势增加产生了一个平坦的电势分布，该电势分布遍及整个存储区域。这种轮廓抑制了由于少量信号电子集中在存储区域中心而导致的电子溢出到衬底中。因此，N^+侧壁增加了可储存电荷。例如，通过增加N^+侧壁，传统的3.0微米直径光电二极管的电荷处理能力提高了四倍以上。用…检验分析的有效性一维分析的结果证实了这一点。这项技术对于小直径光电二极管是有用的。(2)众所周知，含有垂直溢流雨的光电二极管的CCD图像传感器的饱和信号电平随衬底杂质浓度的变化而剧烈变化。然而，饱和信号能级与衬底杂质浓度之间的关系还没有得到分析结果。用漂移扩散模型计算了它们与光电二极管结构和工作条件之间的关系。通过比较分析和实验结果，我们发现CZ、MCZ和外延片周边的杂质起伏分别为*11%、*16%和*6%。居中的分别为*7%、*9%和*6%。从而阐明了这些晶片的杂质起伏模式的特征。可以检测到的最小杂质波动水平几乎为0.1%。提出了一种适用于高感光度帧移位CCD图像传感器的移位寄存器，并对其性能进行了三维数值分析。(4)提出了一种适用于视频信号的数字降噪方法，并进行了测试。较少

(1) We proposed a new photodiode to increase the charge handling capability of solid state image sensors. This photo diode includes an N^+ sidewall that surrounds the charge strage region of a conventional photo diode with a vertical overflow drain. The operation and performance of the diode were analyzed using the three dimensional numerical analysis. We found that an abrupt potential increase, produced around the boundary of the channel stop and the N^+ sidewall creates a flat potential profile that spread all over the storage region, at the beginning of the charge storage. This profile suppresses electron over-flow into the substrate that occurs due to the small amount of signal electron concentrated around the center of the storage region. Therefore, the N^+ sidewall increases the storable charge. For example, the charge handling capability of a conventional 3.0-mum diameter photodiode was improved by more than a factor of four by adding N^+ sidewall. The validity of the analysis w … More as confirmed from the results of one dimensional analys. This technology is useful for small diameter photodiode.(2) It is well known that the saturation signal level of a CCD image sensor including photodiode with vertical overflow rain varies strongly with the substrate impurity concentration. However, the analyti-I results between the saturation signal level and substrate impurity concentration has not been ob-Tained yet. The relation between them was calculated using the drift-diffusion model as a function of photodiode structure and operation condition. By comparing analytical and experimental results obtained from CCD image sensor chips, we found that the impuriy fluctuation at the peripherals of CZ, MCZ, and epitaxial wafers *11%, *16% abd *6%, respectivery. Those at the center were *7%, *9% and *6%, respectively. The distnctive features of the impurity fluctuation pattern for these wafers were therefore clarified. The minimum imuruty fluctuation level that can can be detected is almost 0.1%. Moreover, a novel photodide strucre that suppresses the fluctuation was proposed.(3) CCD shift register suitable for highly photo sensitive frame transfer CCD image sensors was proposed and the performance of it was analized using three-dimensional numerical analysis.(4) A digital noise reduction method applicable to video signal was proposed and tested. Less