超高真空系統之抽氣測試與應用

Abstract

本文研究電子束直寫微影系統之超高真空系統的抽氣測試與應用，此超高真空系統包含一個真空腔體、一個乾式幫浦、一個渦輪分子幫浦、一個離子幫浦、一組低真空計、一組高真空計及一組包覆於腔體上之加熱系統。此真空系統之初型製作已經完成，且已經陸續完成其性能測試。為了在短時間內達成各種特定的壓力，本論文針對超高真空系統之各種不同操作程序組合做了測試與分析。影響抽氣性能之主要因素包含離子幫浦、烘烤溫度及烘烤程序等。在所有系統抽氣測試中，都必須使用油式幫浦與渦輪幫浦。從不同抽氣之操作程序組合測試結果中可得到一些結論，在加入離子幫浦及烘烤五天的情況下，此超高真空系統之壓力可以在七天內達到1.3E-9 Torr。研究也指出，在加入離子幫浦及一次烘烤情況下，此系統壓力可以在一天之內達到9.7E-9 Torr。從研究結果中可以確定，增加烘烤程序可以有效的降低真空系統的抽氣時間及壓力。最後，施加1200伏特電壓的4x4矽針尖陣列之場發射實驗，可以在此超高真空系統腔體中持續做兩個小時。在場發射實驗設備安裝於真空腔內之情況下，真空系統可以在一小時內到達1.0E-7 Torr等級之壓力。

This paper studies the pump down tests and applications of an ultra high vacuum (UHV) system for electron-beam direct-write lithography. The UHV system includes a vacuum chamber, an oil vane pump, a turbo molecular pump, an ion pump, a low vacuum gauge, a high vacuum gauge, and a baking heater fitted around the chamber. The prototype of the vacuum system is manufactured and performances of the prototype are tested. In order to reach different specified vacuum pressure within the shortest time, effects of the different operating process combinations are tested and analyzed. Main factors affecting the pump down characteristics include effect of ion pump, baking temperature, and baking periods. The oil vane pump and the turbo pump are always turned on during the entire pump down tests. From the test results of different operating process combinations, it shows that the vacuum system can reach the lowest vacuum pressure of 1.3E-9 Torr within 7 days, with turned on ion pump and baking of chamber for 5 days. It also shows that the chamber can reach the vacuum pressure to 9.7E-9 Torr within 1 day with turned on ion pump and one baking period. It is also concluded that both the pump down time and vacuum pressure can be greatly reduced with the adding of baking process. Finally, a field emission test of a 4x4 silicon tip array is carried out successfully inside the UHV chamber under the constant applied voltage of 1200V for test duration of 2 hours. With the field emission test species inside the chamber, the vacuum pressure reaches the order of 1.0E-7 Torr within 1 hour.