基于粗对准与精对准信号分开探测的对准系统

Alignment System Based on Separate Detection of Coarse and Fine-Alignment Signals

提出了一种用于光刻装置的对准系统。该对准系统所用的标记包含多个相位子光栅。其中,标记±1级衍射光的光强信息用于产生粗对准信号。在粗对准信号上,通过峰值检测和信号拟合获得最大峰值点,该峰值点即为粗对准位置。同时,在另一光路中,精细子光栅的±1级衍射光的光强信息用于产生精对准信号。利用余弦或正弦曲线对该精对准信号进行拟合,得到一系列的波峰点。距离粗对准位置最近的波峰点即为精对准位置。当精细子光栅的周期足够小时,该对准系统可获得5 nm级的重复精度。

A novel alignment system is presented for lithographic apparatus. The phase sub-gratings are arranged to form an alignment mark. Intensity information generated from interference patterns of the first order diffraction sub-beams of the whole mark, is used to get a coarse-alignment signal. Using peak detection and signal fitting, coarse-alignment position, namely maximum peak, can be found. At the same time, intensity information from fine sub-grating in alignment mark is also detected in another optical path, and fine-alignment signal is acquired by a pbotoelectric sensor. The intensity and position samples of the final-alignment signal are fitted with a cosine or sine curve, and then the series of peak points are derived from the model parameters. Further, fine-align ment position, which is the peak nearest to coarse-alignment position, is obtained. When period of fine sut〉grating is small enough, reproducibility of the proposed alignment system may arrive to the level of 5 nm in theory.