光刻工艺中硅片表面静电现象研究

Investigation of Wafer Surface Static Electricity in Lithography Process

  • 摘要: 光刻是集成电路制造中的关键工艺, 通过光化学反应原理把事先制备在掩膜版上的图形转印到衬底上。光刻工艺之后, 需要对光刻胶图形的关键尺寸进行检测。业界通常采用高分辨率的电子显微镜进行测量。本文从14nm工艺超厚金属连线层出现的晶圆中心量测图形位置偏移问题入手, 利用套刻精度、晶圆水平对准测量、光刻胶旋涂厚度、刻蚀后的检测等检测手段排除其它可能导致图形偏移的因素, 并最终结合硅片表面电势测量技术证明在光刻过程中出现硅片表面电荷积累。硅片表面静电场同SEM量测过程中入射电子束相互作用导致CD量测异常。进一步, 通过分步实验澄清硅片表面电荷的来源, 并阐释了其产生机理, 并最终通过优化显影程式对硅片表面静电现象进行改善。

     

    Abstract: Lithography is one of the most important processes in integrated circuit manufacturing, by which the prepared patterns from mask are transferred onto wafer via photochemical reaction.After lithography processes, the critical dimension (CD) of patterns are measured normally by secondary electron microscope (SEM).In the CD-SEM measurement process of ultra-thick metal layer of 14nm technology, the detected measurement target of wafer center is shifted from registered coordinates, while the other measurement area is normal.The inspection methods including overlay (OVL), wafer leveling, resist thickness, after etching inspection (AEI) and surface potential measurement are carried out to excluding other influence factor of shift.And combined with wafer surface potential measurement, the phenomenon of charge accumulation on wafer surface after lithography has been verified.The interaction between static electricity of wafer center and incidence electrons of SEM causes the measurement issue.Further, the origin and producing mechanism of charge on wafer are clarified by a series of experiments.Finally, this issue is improved by modifying development process of lithography.

     

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