电铸金属光栅中金属沉积过程的在线监测

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

在使用电铸方法制作金属光栅时,采用传统的计时电铸方法常常不能保证金属栅条具有精确的沉积厚度。为了能够实时监测光栅栅条的沉积厚度,以实现电铸截止时刻的精确判断,建立了基于衍射效率判断金属沉积厚度的在线监测系统。采用严格耦合波理论计算了Au在光刻胶沟槽中进行沉积时,衍射效率随Au沉积厚度的变化规律,并讨论了光刻胶占宽比、电铸电流密度对衍射效率的影响;计算了电铸池、镀液对监测激光能量造成的损耗。实验得到的效率曲线与仿真结果相一致;电铸池、镀液对光能的损耗达94.88%。实验结果表明,采用在线监测方法实时判断金属沉积厚度是合理有效的;光刻胶占宽比对在线监测影响不大;电铸电流密度对在线监测有影响,且电流密度越高越有利于截止点的判断。

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.