IC掩模的频谱分析及方向性空间滤波器

把IC掩模的图形看作由许多大小不等、但有相同取向的矩形单元组成,它们的频谱只分布在互相正交的两个特定方向上.如果掩模存在缺陷,因为缺陷的形状是任意的,其分布是随机的,所以,缺陷的频谱分布无特定的取向.根据掩模频谱分布的特点,可制成一个方向性空间滤波器,来阻挡掩模正常图形的频谱,而让缺陷的频谱通过,最后在检查系统的成象面上清楚地显示缺陷的位置及形状.

FREQUENCY ANALYSIS OF IC PHOTOMASK AND DIRECTIONAL SPATIAL FILTER

The graph of IC photomask is considered to consist of many retangular elements which are unequal in size, and have same directionalities. The spectra of retangular elements .distribute, only on two mutually perpendicular special directions. If the photomask has defects, the distribution of the defective spectra has no special direction, because the shapes and distributions of the defects are arbitary.Based on the characteristic of the spectrum distribution of the photomask, a directional spatial filter can be synthesized. Since the filter interrupts the spectrum of the normal graph of the photomask, and allows the defective spectra pass, the shapes and positions of the defects are displayed clearly on the imaging plane of the detective system.