多重電子束直寫微影中具球形結構場發射源之電子光學系統設計與最佳化

為了延續摩爾定律，電子束直寫微影被認為是能可靠發展的技術其中之一，因為其擁有超高解析度之微影能力。很可惜的，由於電子束微影受限於其低產量之特性，到目前為止始終無法善用其優點至直接曝寫晶圓之範疇。多重電子束直寫微影因為有著開發並行的特性，理論上來說將很有機會得以妥善應用來改善電子束微影低產量的致命缺點。為了增加多重電子束微影可行的機會，每一個電子光學系統必須要被微小化且整合在一起。利用微機電製程技術將有機會得以實現多個電子光學系統微縮且製造在同一基板上，同時驅動大量的平行電子束以進行電子束微影製程之應用。雖然開發並行可有效的改善產量，但畢竟無限制的增加整合電子光學系統的基板面積並不實際，電子束與電子束之間也必須保留一定大小的空間以避免因密度過高所帶來的相互干擾影響，此時如能有效的增加每一個電子光學系統之電流量則為另一個潛在能改善電子束微影產量不足之辦法。文獻中有許多不同結構的場發射源被研究者討論與比較，研究指出一個在頂端具有球狀結構的發射源，在相同的環境情況下能比一般的場發射源具有更高的電場分佈總值，且被期望能發射出更大的電流量。在本論文當中，為了定量的探討使用此種特別結構之場發射源所能帶來的改善，我們參考並且修改了一電子光學系統之設計方法，透過加入不同的參數設定，以進一部探討其放電特性，包括電流大小以及聚焦之能力。根據我們提出的電子光學系統設計方法，初步的模擬結果顯示在被我們設計描述的電子光學系統環境下，頂端有球形結構之場發射源將能在相同的解析度要求下發射出相較於傳統之場發射源六倍的發射電流，且兩者進一步之圖案製作真確度模擬也在相同之水平。綜合以上兩者結論，具有球形結構之場發射源能在一樣的微影品質下發射出相較於傳統發射源六倍大的發射電流以改善電子束微影之產量。

關鍵字

最佳化；電子束微影；電子束直寫；無光罩；產量；發射電流；電子點尺寸；圖案製作保真度

並列摘要

Electron-beam–direct-write (EBDW) lithography is considered as a promising candidate for next-generation lithography due to the high-resolution patterning capability. Suffering from the low-throughput nature, EBDW lithography fails in high-volume manufacturing. Multiple-electron-beam–direct-write (MEBDW) lithography can theoretically improve the throughput performance by exploited parallelism. To achieve the feasibility of MEBDW lithography, electron-optical systems in it are miniaturized and integrated together. By utilizing MEMS processes, electron-optical systems (EOSs) can be shrunk and fabricated on a single substrate to drive massively parallel beams simultaneously, and thus implementing MEBDW lithography. Although the exploited parallelism can effectively improve the throughput, the amount of EOSs is limited by the required space between each EOS to prevent interaction between beams and integrate other devices in a fixed-size area. Since it is unrealistic to increase the amount of EOSs without limitation, improving the throughput by enlarging the emission current of each beam is another feasible way. Field distribution comparisons between geometrically different emission sources, which are conducted by previous researchers, indicate that with a spherical profile on the top of the emission source in an EOS, it is expected to achieve higher emission current comparing to the one with conventional emission source. The conventional emission source is in the shape of a sharp pin with a chamfered surface on the top of the pin. However, the increase of emission current and the lithographic qualities of using this particular tip as an emission source still remain quantitatively unclear. In this work, an EOS design flow is employed and modified with newly introduced parameter for quantitatively analyzing advantages of adding the spherical profile into an emission source. Based on our method, preliminary optimized result indicates that comparing to using a conventional emission source, a six-time-larger emission current is obtained in the EOS that the ball-tip emission source is used. Furthermore, the results of patterning fidelity of the two EOSs with different emission sources are at the same level. With the two results mentioned above, it is considered that employing an EOS with a ball-tip emission source, much higher throughput is obtained without losing quality of patterning fidelity.

並列關鍵字

optimization ； electron-beam lithography ； direct write ； mask-less ； throughput ； emission current ； beam spot size ； patterning fidelity

參考文獻

[1] R. R. Schaller, "Moore's Law: Past, present, and future," Ieee Spectrum, vol. 34, pp. 52-&, Jun 1997.

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