全息光栅实时显影监测曲线的理论模拟

在特定的工艺条件下，光刻胶的非线性效应非常显著；合理地利用非线性效应，能够制作出近似矩形的全息光栅掩模。为了分析清楚非线性效应对光栅沟槽成形的作用机理，有必要建立一个显影理论模型。模拟得到的光栅轮廓和实验样片的扫描电子显微镜照片结果很吻合。根据这个模型，进而使用光栅严格理论，得到其主要特征与实时监测实验曲线一致的理论模拟监测曲线。理论分析和实验证实，该模型基本表征了工艺条件对光栅沟槽形状的影响，并揭示了光刻胶呈现显著非线性效应时，必然对应着明暗条纹中心位置之间的显影刻蚀速率相差很大。这个模型为全息光栅的工艺研究提供了一个有效的理论分析工具。

Modeling of In-Situ Monitoring Curves During Development of Holographic Gratings

Under specific processing conditions, the nonl inearity of photoresist is strong, which can be advantageously used to make rectangular holographic grating masks. In order to clarify the relationship between the fabrication conditions and the groove profile formation, a model for simulating the development of photoresist grating is presented. The theoretically simulated groove profiles are in good agreement with profiles obtained from SEM photographs of fabricated gratings. Based on this model, combined with using a rigorous code for modeling grating diffraction, the efficiency of the reflected -1st order of diffraction is simulated as a function of development time. The main features of the simulated curve are found to coincide with those of the experimental in-situ monitoring curve. It is verified that the remarkable nonlinear effe ct of photoresist must be accompanied with a vast difference of etch rate between the center of a bright fringe and the center of its neighboring dark fringe. The model has been demonstrated capable of characterizing the influence of fabrication conditions on holographic grating groove formation.