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以逐个芯片曝光方式工作的分步重复投影复印法,要得到良好的芯片就需要一个快速而精确的对准系统,这在其它的图象转换系统中尤为重要。目前的对准精度要求是图形特征尺寸的1/5到1/10,对于1微米的线宽来说,其对准精度应为0.2～0.1微米。为保证每小时有60到100片的高生产效率,每枚片子总的对准(X、Y向和角度)时间应小于几秒钟。这样,每个芯片或每个陈列局部的反复对准时间约为0.1秒。多次反复地对准时间与片子的畸变程度有关。如果各道光刻工序不是在同一台机器上进行,那么它还与各光刻机的一致性有关。另外重要的一点是在电路的整个制造过程中,应始终保持精度和速度的一致性。也就是说,在工艺过程中无论所涂复的厚度和层数如何度化,所涂复的片子对准标记必须保持良好的反差。本文主要描述了一个把衍射光栅制作在掩模和片子上的“同轴”对准法。该衍射光栅标记的相关就给出了一个具备下列三个条件的对准信号:1、这样的对准标记结构可以消除由于片子上散射和反射而产生的光噪声,从而给出了一个高反差信号;2、该反差与涂层的反射率无关;3、此相关信号能用一个快速光探测器来探测。
The step-and-repeat projection method, which operates on a chip-by-wafer basis, requires a fast and accurate alignment system to get a good chip, which is especially important in other image conversion systems. Current alignment requirements are 1/5 to 1/10 the size of the features used for the pattern, and the alignment accuracy should be 0.2 to 0.1 microns for a line width of 1 micron. To ensure high productivity of 60 to 100 tablets per hour, the total alignment (X, Y, and angle) per film should be less than a few seconds. In this way, the repeat alignment time locally for each chip or each display is about 0.1 second. Repeatedly aligning the time repeatedly with the degree of distortion of the film. If the lithography process is not on the same machine, then it is also consistent with the consistency of the lithography. Another important point is that the accuracy and speed of the circuit should always be consistent throughout the manufacturing process. In other words, no matter how thick the coating and the number of layers in the process, the applied film alignment marks must be kept in good contrast. This article describes a “co-axial” alignment method for making diffraction gratings on masks and films. The correlation of the diffraction grating marks gives an alignment signal with the following three conditions: 1. Such an alignment mark structure can eliminate optical noise due to scattering and reflection on the film, giving a high contrast Signal; 2, the contrast has nothing to do with the reflectivity of the coating; 3, this correlation signal can be detected with a fast photodetector.