Research On The Damage Mechanisms Of Silicon And Silicon-based Photodetectors Irradiated By Millisecond Laser

The damage mechanism of millisecond laser interaction with silicon and silicon-based photoelectric device are investigated by numerical simulation and experiments.Thermal process of 1064nm millisecond pulsed Nd:YAG laser irradiated silicon was time-resolved temperature measured by an infrared radiation pyrometer, temperature evolutions of the spot center for wide range of laser energy densities were presented. The waveforms of temperature evolution curves contained much information about phase change, melting, solidification and vaporization. An axisymmetric numerical model was established for millisecond laser heating silicon. The transient temperature fields were obtained by using the finite element method. The numerical results of temperature evolutions of the spot center are in good agreement with the experimental results. Furthermore, the axial temperature distributions of the numerical results give a better understanding of the waveforms in the experimental results. The melting threshold, vaporizing threshold, melting duration and melting depth were better identified by analyzing two kinds of results.A three-dimensional crystal finite element model (CFEM) was established to investigate the thermal slips of monocrystalline (100) silicon induced by millisecond pulse Nd:YAG laser. The resolved shear stress fields of 12 slip systems have been attained. Meanwhile, the thermal plastic deformation depth, region and density have been calculated. The numerical results show that the thermal slips are introduced due to the anisotropic thermal shear stresses of slip systems surpassed the critical yield stress, and come out before the surface silicon melting. This is consistent with experimental result. Brittle cracks are introduced due to the initiation points offered by the thermal slips which reduced greatly the fracture strength.A multiphysical model was established for millisecond pulsed Nd:YAG laser heating of (110) silicon-based PIN Photodiode. The transient temperature fields, thermal stress fields and the dopant redistribution were obtained by using the finite element method. The photoelectric parameters degradation of Si-based PIN photodiodes irradiated by 1064 nm millisecond Nd:YAG laser has been measured. Surface damage morphology, dark current and sensitivity were investigated for the irradiated photodiodes. It has been shown that the dark current was the first and the most sensitive degradation parameter, and we believe that the dislocation induced by the activated thermal slips was the main reason. The sensitivity decrease until the dark current reach to μA magnitude and the surface have melted seriously, we believe the remove of the antireflection layer and the dopant redistribution at the melting stage are the reasons.A three-dimension model was established to simulate the process of 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 results indicated that the coupling of the heat damage and thermal stress damage was the main reason for the millisecond laser damage CCD.The softening of PMMA microlens or rupture of silica microlens reduced photosensibility. The 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 Al-shield layer and the fracture of silica insulting layer is the functional damage mechanism of the CCD.