在以往的研究，極紫外光干涉式微影所使用的穿透式繞射光柵窗口皆為以氫氧化鉀(KOH)濕式蝕刻製作，但KOH濕式蝕刻製程不容易控制，需保持穩定的蝕刻速率。若有蝕刻液滲透至正面圖案，可能會造成光柵結構損壞。
因此，為了改善KOH蝕刻的缺點，實驗使用奈米壓印微影術結合底層塗佈犧牲層PMGI的方式，成功的避免KOH蝕刻製程所造成的問題，製作出無基材穿透式繞射光柵。無基材光柵不需要透過KOH蝕刻就可以製作，因此相較於以往需成長Si3N4薄膜作為KOH蝕刻遮罩的一般穿透式光柵，我們可以大幅增加光穿透效率與製程良率，並且可以更佳的掌控每次干涉曝光所需的時間。除此之外，我們直接使用SU-8光阻當作穿透式繞射光柵的阻擋層。此阻擋層除了可以抑制零階光外，還可以藉由SU-8其固化後高穩定的特性，當作我們無基材穿透式繞射光柵的支撐層使用。SU-8阻擋層的製作不需要複雜的流程，直接對光阻進行曝光即可定義出阻擋層結構。實驗中我們使用嚴格耦合波分析法(RCWA)討論光柵之光學特性。
最後，我們成功利用300奈米與200奈米週期的無基材穿透式光柵結合極紫外光干涉式微影，干涉出75奈米、50奈米、37.5奈米以及25奈米的PMMA阻劑的干涉條紋，並且光柵的製作不需要使用KOH蝕刻製程即可製作。

In the experiment of transmission grating window fabrication, KOH etching process is the commonly used tool for fabrication of the windows. However, KOH etching process is not easy to control.
Therefore, we proposed the use of nano-imprint and sacrificial layer (PMGI) process to improve the process yield of the transmission gratings and to reduce the overall process time. Freestanding transmission grating can increase the diffraction efficiency because it does not need a Si3N4 layer as a mask of KOH etching process. In order to further simplify the stop-layer process, we replace Cr metal with SU-8 photoresist that does not need complex process. The SU-8 stop-layer can not only suppress the zero order EUV light but also support our transmission grating structure. The optical behavior of a grating was analyzed by rigorous coupled-wave analysis (RCWA).
In conclusion, we have fabricated 300-nm and 200-nm pitch freestanding transmission diffraction grating and successfully recorded 75, 50, 37.5 and 25 nm half-pitch interference fringe on the PMMA resist by EUV-IL experiment. These gratings can be easily transferred to any supporting frame. Therefore, KOH wet etching is not required. Overall processing time is reduced, and fabrication yield of transmission gratings is increased.

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