激光干扰和损伤CMOS图像传感器研究进展(特邀)

Research progress of laser dazzle and damage CMOS image sensor (invited)

  • 摘要: 高能激光是对抗光电成像系统的有效手段。随着互补金属氧化物半导体(Complementary Metal Oxide Semiconductor, CMOS)图像传感器性能和制作工艺的快速发展,其市场占有率已逐步赶超电荷耦合器件 (Charge Coupled Device, CCD),成为当前主流的图像传感器。CMOS图像传感器的激光干扰和损伤也随之成为国内外相关领域的研究热点。文中首先根据CMOS图像传感器的发展历程,对其结构和工作原理进行了介绍,并在此基础上简要分析了CMOS图像传感器在激光辐照过程中的薄弱环节,之后综述了CMOS在激光辐照下受到干扰及损伤现象的研究进展,并对干扰的评价方法和损伤阈值的主要测量方法进行了总结归纳,最后探讨了利用复合激光系统提升损伤CMOS图像传感器能力的发展现状和前景。

     

    Abstract:
      Significance  Complementary Metal Oxide Semiconductor (CMOS) image sensors are currently the most mainstream solid-state image sensors. They have the characteristics of low power consumption, high integration, and fast imaging. In the past decade, breakthroughs have been continuously made in their performance, surpassing Charge Coupled Device (CCD) image sensors in market share and product iteration speed. It is widely used in the fields such as digital cameras, security monitoring equipment, mobile phones, drones, medical detection, and autonomous driving. As the core component of an optoelectronic imaging system, image sensors strongly absorb laser energy within their working wavelength, making them more susceptible to laser damage compared to other components of the optoelectronic system. However, the new back side illumination CMOS and stacked CMOS have significant structural differences from traditional front side illumination CMOS image sensors, and their ability to resist laser interference and damage has been greatly improved. Therefore, the laser interference effect and damage mechanism of CMOS image detectors have received widespread attention from scholars at home and abroad.
      Progress  Firstly, the structure and working principle of CMOS image sensor according to its development history are introduced. The pixel structure of CMOS has evolved from passive pixels to active pixels, where each pixel can independently collect, amplify, and output signals. SiO2 deep trench isolation (DTI) structure (Fig.3(d)) is used between pixels for crosstalk suppression. The chip structure of CMOS has evolved from front illuminated to back illuminated and stacked, and the position of the metal wiring layer has buried deeper, making it more difficult to cause destructive damage. On this basis, the weaknesses of CMOS image sensor in the process of laser irradiation are briefly analyzed. CMOS uses a correlated double sampling (CDS) circuit to output signals, which uses the difference between two signals to output, and interfering with both signals causes pixel oversaturation; The use of the same column line to transmit the reference signal of a column of pixels provides the possibility of large-scale crosstalk. The damage at different stages is related to the depth of laser action. It can be concluded that the key to causing large-scale damage to CMOS image sensors is the severe damage to the internal circuit layer.  CMOS image sensor is used more and more widely. More attention has been paid to the experimental study of laser-induced dazzle and damage of CMOS. The evaluation methods of interference and the main measurement methods of damage threshold are summarized. The representative measurement results of interference and damage threshold are summarized (Tab.1-2). By comparing the results of interference, the conditions of oversaturation and crosstalk are summarized, and the conclusion is verified that the above-mentioned CDS circuit is susceptible to interference. Compared with CCD, CMOS has better anti-damage ability, especially the back-illuminated CMOS, which is difficult to cause large area damage. This is because the back-lit CMOS circuit layer is deeper, above a thicker layer of silicon-based material, forming a certain inherent protective layer. With the wide application of backlit and stack CMOS chips, how to improve the damage efficiency of laser-illuminated CMOS chips is an urgent problem to be solved in the next research.  Finally, the development status and prospects of using new laser systems to improve the damage ability of CMOS image sensors are discussed. The composite laser can be made up of two pulses with different parameters. The ablation and damage of the composite laser on the single material target has been well studied. If the laser parameters are matched properly, the absorption rate of laser energy can be improved effectively. It has been proved that the composite laser can improve the efficiency of damaged CMOS to some extent, but the effect is limited. To further improve the laser damage efficiency, we can consider to further increase the adjustable parameters of the laser, the combination of three or more pulses into the pulse string form.
      Conclusions and Prospects   CMOS image sensors are booming, which have become the most mainstream image sensors. As an important countermeasure, the research of laser jamming and damage CMOS image sensor needs to be further explored. The purpose of this paper is to provide some references for the future research of laser jamming and damage CMOS, and the idea of using the new laser system to improve the damage efficiency is proposed.

     

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