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针对接近接触式光刻技术的特点,提出了一种实用的反射式光刻对准方案。方案采用差动叠栅条纹对准技术,以叠栅条纹相位作为对准信号的载体。在掩模和硅片上分别设计两组位置相反、周期接近的光栅对准标记。电荷耦合器件(CCD)成像系统接收叠栅条纹图像,采用傅里叶变换提取叠栅条纹相位,得到掩模与硅片的相对位置关系。设计的标记可同时探测横纵方向的对准偏差。给出了合理的光路设计方案,详细分析了整个系统对准的内在机制,建立了可行的数学模型。研究表明,当对准偏差小于1pixel时,最大误差低于0.002pixel。与透射式光路对比,该方案更具有实用性,满足实际对准的要求。
Aimed at the characteristics of proximity lithography, a practical reflective lithography alignment scheme is proposed. The scheme adopts the differential moire alignment technology, and uses the moire phase as the carrier of the alignment signal. On the mask and the wafer, two sets of grating alignment marks with opposite positions and periods are designed respectively. Charge-coupled device (CCD) imaging system receives the moire fringe pattern, Fourier transform is used to extract the moire phase, and the relative position of the mask and the wafer is obtained. The designed mark can simultaneously detect the alignment deviation in the horizontal and vertical directions. The reasonable design of optical path is given, the internal mechanism of the whole system alignment is analyzed in detail, and a feasible mathematical model is established. Research shows that when the alignment error is less than 1pixel, the maximum error is less than 0.002pixel. Compared with the transmissive optical path, the scheme is more practical and meets the requirements of actual alignment.