用于光刻装置的多光栅标记对准系统

Alignment System with Multi-Grating Mark for Lithographic Apparatus

提出了一种用于光刻装置的Si片-工件台对准系统。该对准系统采用多光栅对准标记,标记的每个方向有序排列着四个子光栅。对准时,单波长对准光束照射在标记上,各级衍射光以不同的衍射角反射出。通过空间滤波器,零级和高级衍射光被滤除,而±1级衍射光被保留并相干涉成像在参考光栅的表面。两个较大周期子光栅的对准信号用于对准标记的捕获和粗对准,两个较小周期子光栅的对准信号用于获得粗对准基础上的精确对准。由于该对准系统无须采用楔板组,与ATHENA对准技术相比,降低了制造成本,提高了工程的可实现性。

A novel phase grating alignment system was proposed to align a wafer with respect to a wafer-stage for lithography. This system adopted a multi-grating mark comprising four arranged sub-gratings in each direction. During the process of alignment scanning, an illumination beam with a wavelength irradiated the mark, and the diffraction sub-beams at various levels were reflected by different angles. Zero-order and high-order diffraction sub-beams were prevented by the spatial filter, whereas the ± 1 order sub-beams were reserved to form interference patterns on the reference gratings. The alignment signals of two large-period sub-gratings were used for mark capture and coarse alignment. Based on the coarse alignment, the fine alignment was obtained using the alignment signals of the small-period sub-gratings. Compared with ATHENA, the proposed alignment system without wedges can reduce cost and increase realizability in engineering application.