全息光栅制作中光栅掩模形状随曝光量及干涉场条纹对比度的变化规律

为了在光栅制作中对光栅掩模占宽比及槽深加以控制,结合光刻胶在显影过程中的非线性特性,建立了光栅掩模槽形演化的数学模型,由此分析和模拟曝光量、条纹对比度对光栅槽形的影响。结果表明:在显影条件确定时,光栅掩模占宽比随光刻胶曝光量的增大而减小,条纹对比度减小,则不仅使光栅占宽比减小,同时也是使光栅槽深减小的主要原因,这样做的前提是预先通过实验和计算确定出一个曝光量上限Ec。该方法能够反映光栅掩模形状的演化规律,为全息光栅参数预测和工艺控制提供依据。

Profile Evolution of Grating Masks According to Exposure Dose and Interference Fringe Contrast in the Fabrication of Holographic Grating

In order to improve the precision control of the duty cycle and the groove depth of a recorded profile in the photoresist, based on the nonlinearity of the photoresist in development processing, a binary resist mathematical model for simulating the profile evolution of the photoresist grating is presented, according to this model, the changing of the profile characteristics such as duty cycle and the groove depth which depend on the contrast and exposure dose can easily be understanded. It turns out that: under specific development condition and the exposure upper limit Ec recognized by calculating and experiment, the duty cycle of the grating masks decreases as the exposure dose increases, the decrease of fringe contrast not only results in the decrease of the duty cycle, but also results in the decrease of the groove depth. The model can show the profile evolution trend exactly, it provides a right analysis tool for forecasting and controlling the groove shape in the fabrication of the grating masks.