Implementing registration measurements on photomasks at the Nanometer Comparator
Implementing registration measurements on photomasks at the Nanometer Comparator
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DOI：
10.1088/0957-0233/23/9/094010
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发表时间：
2012-09-01
影响因子：
2.4
通讯作者：
Bosse, Harald
中科院分区：
文献类型：
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作者：
Koening, Rainer;Weichert, Christoph;Bosse, Harald
由于半导体工业生产过程中引入了双重图案化方案，以及光刻投影过程中对掩模特征光学图像放置误差（1.2纳米（3西格玛））相应的严格规范，因此需要对光掩模的套准测量进行重大改进。德国物理技术研究院（PTB）的纳米比较仪是一种一维真空干涉长度比较仪，已经在线性标尺和线性编码器上展示了这一水平的测量重复性，因此该比较仪也应用于光掩模的放置计量。由于光掩模是一块相对较薄的板，几乎在其两端被支撑，所以弯曲影响比线性标尺大得多，必须采取预防措施以减少样品支撑对测量结果的影响。构建了一种新的样品支架，它具有机械对准辅助装置。此外，通过有限元计算校正了由掩模弯曲引起的位置偏差。用纳米比较仪对一个高质量掩模进行的测量显示，测量的特征位置与公共平均值的最大偏差低于0.5纳米，重复性为0.2纳米。这些结果表明，使用掩模测量机的一维校准使我们能够以足够的精度进行可溯源的套准测量。
Due to the introduction of double patterning schemes in the production processes of the semiconductor industry and the corresponding stringent specifications of the placement errors of the optical images of mask features (1.2 nm (3 sigma)) in the lithographic projection process, significant improvements of the registration measurements on photomasks are required. The Nanometer Comparator of the PTB, a one-dimensional vacuum-interference length comparator, has already demonstrated measurement reproducibility at this level on line scales and linear encoders, and therefore this comparator should also be applied for placement metrology on photomasks. Because a photomask is a relatively thin plate which is supported almost at its ends, the bending influence is much larger than for line scales and precautions had to be taken to reduce the influence of the sample support on the measurements results. A new sample mount was built, which exhibits mechanical alignment aids. In addition the position deviations caused by the mask bending were corrected by means of finite element calculations. Measurements performed with the Nanometer Comparator on a high-quality mask showed a maximum deviation of measured feature positions from the common mean of below 0.5 nm and a reproducibility of 0.2 nm. These results suggest that the use of a one-dimensional calibration of mask measuring machines allows us to perform traceable registration measurements with sufficient accuracy.