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光刻对准中,一般将硅片和掩模对准标记制作成周期接近的光栅,通过光栅标记叠加形成的叠栅条纹的相位信息,探测掩模和硅片的相对位置关系。在实际的应用中,叠栅条纹的方向不仅与对准标记的几何位置有关,而且还与CCD的位置有关。为了将叠栅条纹的光刻对准方法推向实际应用,从矩形光栅到叠栅条纹,分析了一般光栅的相位分布规律。根据叠栅条纹相位特性分析了掩模、基片和CCD的几何位置对对准精度的影响;建立了实际对准偏差与理论值的数学关系模型。研究表明,没有角位移的情况下,当位移值小于0.4pixel时,理论上最大对准误差低于0.002pixel。
In the lithography alignment, the alignment marks of the silicon wafer and the mask are generally formed into periodic gratings, and the phase information of the moire formed by the grating marks is superposed to detect the relative positional relationship between the mask and the silicon wafer. In practical applications, the direction of the moire is not only related to the geometric position of the alignment mark but also to the position of the CCD. In order to push the method of photomask alignment of moire to practical application, from the rectangular grating to the moire pattern, the regular distribution of the grating is analyzed. According to the phase characteristics of moire, the influence of the geometrical position of mask, substrate and CCD on the alignment accuracy is analyzed. A mathematical relation model between the actual alignment deviation and the theoretical value is established. The research shows that in the absence of angular displacement, when the displacement value is less than 0.4pixel, the theoretical maximum alignment error is less than 0.002pixel.