In-situ monitoring of metal depositing in the fabrication of metallic grating

During the fabrication process of metallic gratings using electro-deposition, the thickness of deposited metal usually cannot be precisely controlled by the traditional timing method. In order to monitor the deposit thickness of grating bars and precisely stop depositing metal in a timely manner during the fabrication of metallic gratings, an in-situ monitoring system based on diffraction efficiency measurements was introduced. The change law of diffraction efficiency varying with Au deposition thickness was calculated using the rigorous coupled wave analysis(RCWA) method and the effect of the photoresistor grating's duty cycle and deposition current density on diffraction efficiency was discussed. The energy loss of monitoring lasers in the system was also calculated. The efficiency curve of the experiment coincides with simulation and the energy loss induced by the electro-deposition pool and solution was up to 94. 88%. The experimental results indicate that the in-situ monitoring system is effective in estimating the thickness of deposited metal during the fabrication of metallic gratings. The duty cycle of photoresistor gratings has less influence on in-situ monitoring than that of deposition current density and a higher current density was more beneficial for monitoring.