Proceedings Article | 29 March 2019
KEYWORDS: Charge-coupled devices, Sensors, Silicon, CCD image sensors, Pulsed laser operation, Laser irradiation, Continuous wave operation, Thermal modeling, Laser induced damage, Thermal effects
CCD is a charge-coupled device, which is a new type of solid-state imaging device. It is an analog integrated circuit chip developed on the basis of large-scale silicon integration process. In the process of photoelectric countermeasures, the CCD detector is the core device of optoelectronic equipment. Due to its sensitivity to light, and the focusing effect of the optical system, the CCD is easily damaged by the laser interference, causing the system to be paralyzed and huge losses. So studies on the damage mechanism of laser to CCD detector and characteristics of different laser damage to CCD become the key technology of CCD protection. The temperature rise of the CCD detector after laser irradiation leads to thermal saturation of the device, changes in internal microstructure, thermal strain and thermal stress, and thermal and mechanical effects are important causes of damage. The CCD detector mainly comprises a multi-layer material such as a Si substrate and a SiO2 oxide layer light-shielding film. When the laser irradiates the surface of the detector, since the SiO2 layer is thin, the laser energy is hardly absorbed, and the laser energy is completely absorbed by the Si substrate material. The laser irradiation on CCD detector can be simplified as the thermal action of the laser on the Si material. Using finite element analysis, combined with the structural characteristics and heat transfer theory of CCD detector, the theoretical model of laser irradiated CCD detector is established. The temperature and stress of the detector after laser irradiation are numerically analyzed, and the Si base of the detector is calculated. The temperature and thermal stress distribution at the interface between the bottom layer and the SiO2 oxide layer and the intersection of the two are discussed. The damage mechanism of the laser irradiation detector is discussed, and the continuous laser and the repetitive pulse laser pair detection are compared under the same average power density. The calculation results show that under the condition of constant average power density, detector irradiated by the repetitive pulsed laser has higher temperature and higher stress; the thermal stress of the SiO2 oxide layer is larger, and the opaque aluminum film layer and the SiO2 layer may separate, while the Si material mainly suffered compressive stress and the stress value is small, and the possibility of damage is small.
