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随着超大规模集成电路 (VLSI)图形密度的增大 ,邻近效应已成为光学光刻的关键问题之一。通常在平整硅片上对 0 5 μm图形采用 0 5 4NA和传统的单层i线抗蚀工艺时 ,密集图形和孤立图形间的线宽差异大约为 0 0 8μm。然而 ,这一线宽差异已严重地影响了实际生产的工艺稳定性。阐述了邻近效应对图形尺寸、线条与间隙占空比、衬底膜种类、曝光过程的散焦效应、与抗蚀剂厚度变化有关的抗蚀工艺条件和显影时间的依赖性。同时 ,采用 2种不同抗蚀剂实验监测了不同潜像对比度引起的关键尺寸 (CD)偏差。为减小实际图形因抗蚀剂厚度变化引起的CD差异 ,获得最佳抗蚀剂厚度 ,进行了一种模拟研究。
With the increase of VLSI graphics density, the proximity effect has become one of the key issues in optical lithography. When 0 5 4NA is used for a 0 5 μm pattern and a conventional single-layer i-line resist process is used on a flat wafer, the difference in line width between dense and isolated patterns is about 0 μm. However, this difference in line width has seriously affected the process stability of the actual production. The dependency of adjacent effects on the size of the pattern, the duty cycle of the lines and spaces, the type of substrate film, the defocusing effect of the exposure process, the resist process conditions associated with the resist thickness variation, and the development time are described. At the same time, two different resist experiments were used to monitor the critical dimension (CD) deviation caused by the contrast of different latent images. In order to reduce the CD difference caused by the change of the resist thickness in the actual pattern and to obtain the optimum resist thickness, a simulation study was conducted.