Mechanisms for the millisecond laser-induced functional damage to silicon charge-coupled imaging sensors

Abstract

A three-dimensional model was established to simulate the process of a millisecond Nd:YAG laser irradiating the CCD, based on its array and multilayer structure. The transient temperature and thermal stress field of the CCD were calculated by using the finite element method. The temperature dependence of material parameters was taken into consideration in the calculation. The results indicated that coupling of the heat damage and thermal stress damage was the main reason for the millisecond laser damage CCD. Softening of the PMMA microlens or rupture of the silica microlens reduced the fill factor of the CCD. Plastic deformation of the silicon substrate increased a great deal of dark current. The leakage current was introduced due to the peeled Al shield. Most importantly, the melting through of the Al-shield layer and the fracture of the silica insulating layer are the two critical factors for functional damage to the CCD. Meanwhile, the influence of the material and fill factor of the microlens was also considered. The results showed that plastic damage of the silicon substrate was more dramatic than the PMMA microlens CCD. And the damage threshold decreased along with the increasing fill factor.