投影光刻物镜倍率的公差分析与补偿

Magnification Tolerancing and Compensation for the Lithographic Projection Lens

为满足严格的套刻需求,双远心结构的投影光刻物镜需要选择恰当的元件移动来进行倍率的补偿和调节。提出了一种简单而实用的方法来进行倍率的公差分析。该方法利用商业优化设计软件和有限差分算法计算了多项公差对物镜倍率的敏感程度,同时结合公差对系统波像差的敏感度选择最佳的倍率补偿元件。利用以上方法,对一台双远心、工作波长193nm以及数值孔径0.75的投影光刻物镜进行了倍率的公差分析和补偿器优选。结果显示,系统较好地实现了±50×10-6的倍率调节功能,而系统波像差劣化程度均方根值小于1.5nm。

To meet the stringent overlay requirements, it is desirable to select appropriate elements to compensate and adjust the magnification of the projection lithographic lens with double telecentricity. A simple and practical method to tolerance the magnification is presented. This method uses the commercial optical design software and the finite difference algorithm to calculate the magnification sensitivity for some tolerances, and then selects the optimal magnification compensator with the consideration of the wave aberration sensitivity. By using this method, the magnification tolerance is analysed and the magnification compensator is selected for a projection lens with the working wavelength of 193 nm and numerical operture of 0.75. The results show that the lens achieves 50 X 10-6 magnification adjustment, and the root-mean-square degradation of lens wavefront aberration is less than 1.5 nm.