摘要
介绍了一种实时监测全息光栅曝光过程的新方法。在曝光过程中 ,光刻胶折射率的空间分布发生微小变化 ,由此形成的潜像光栅同时对记录光束产生衍射 (自衍射 ) ,探测一个非零级次的衍射强度的变化就可对曝光过程实时监测。实验证明 ,这种技术能灵敏、客观地探测出样片之间由于个性差异所导致的最佳曝光量的漂移 ,制作者可以借此对曝光时间做实时补偿。发现自监测曲线之线性区的末端存在着一个明显的最佳曝光参考点 ,紧接其后是一个最佳曝光可选择区。采用了一个曝光模型 ,其模拟结果和实验中得到的自监测曲线能很好地吻合。理论分析证实 ,根据实时监测曲线的相对幅值来优化最佳曝光量的方法是很合理的 ,这种实时自监测是一种非常简单、能有效控制曝光量的技术。
A novel technique of monitoring the exposure process in fabrication of holographic gratings is presented. When exposed to the interference pattern of two coherent laser beams, the refractive index of the photoresist layer undergoes a time-dependent, spatially periodic change, leading to a latent-image grating that in turn diffracts the two incident recording beams. By detecting one of the self-diffracted orders, without introducing an additional monitoring laser beam, one can obtain a monitoring curve whose features convey valuable information about the exposure process. This technique, termed in-situ self-monitoring technique, can be used to sensitively and objectively detect the variations in the optimal exposure dose caused by random differences of properties from sample to sample, so that compensative measures can be taken by the operator as the exposure is still in progress. A complete monitoring curve is divided into four characteristic zones and the significance of each zone is discussed. It is found that it is the shape rather than the scale of the monitoring curve that determines when the exposure dose is optimal. Authors' simulated modeling curves resulted from adopting a phenomenological exposure model are found to be in good agreement with the experimental monitoring curves. This in-situ self-monitoring technique is a simple and efficient tool for selecting optimal exposures in fabrication of holographic gratings.
出处
《光学学报》
EI
CAS
CSCD
北大核心
2004年第6期851-858,共8页
Acta Optica Sinica
基金
国家 8 6 3计划资助课题
关键词
全息光栅
衍射光学元件
物理光学
实时潜像监测
光刻胶光栅
光栅制作
曝光模型
physical optics
diffractive optical component
in-situ monitoring of latent images
holographic grating
grating fabrication
exposure
exposure model
