利用背向散射電子偵測電子束微影系統電子束漂移現象

Abstract

對於22奈米世代之IC製造技術，多重電子束微影術被公認為極具潛力的發展中技術之一，利用多重束電子束同時運作可大量增加系統之產能。在此類系統中，光電二極體(SPD)電子感測器極可用於有限的工作距離及低能量電子偵測，其擁有小尺寸，高電子偵測率，以及低成本等等的優點，因此適合整合於多重電子束系統當中。 本研究的目標在架設位置感測光電二極體於掃描式電子顯微鏡系統(SEM)，並以低能量電子束及低工作距離實驗其感測效能，以作為多感測器陣列設計參數的驗證。感測區分割為四像限，可用於分析電子束所產生之背向散射電子分布，以及長時間操作下電子束光學系統所產生的電子束漂移現象，並藉由高斯分布模型模擬背向散射電子在四像限之分布特性，可用以分析實驗中電子束掃描時四像限訊號之變化。此外，搭配電子束掃描線圈以及光電二極體電子感測器達成背向散射電子影像之偵測, 在未來可使發展中之多電子束直寫微影系統—MPML2具有成像能力。

Multiple Electron beam lithography is one of the promising technologies for 22nm-node Integrated Circuit (IC) fabrications. For the purpose of improving system throughput, large amount of beams should be driven at the same time, and miniature electrostatic elements are widely utilized in these systems. Silicon Photodiodes Detector (SPD) can be used in the systems under the small working distance and low electron energy. The advantages of small profile, high electron collection efficiency and efficient cost make it suitable to integrate in the multiple electron beam lithography system. The purpose of this research is to build the silicon photodiodes detector in the Scanning Electron Microscope (SEM) system. The detection performance is illustrated under the low electron energy and small working distance through experiment. The quadrant cells of active area on silicon photodiodes are used to analysis the backscattered electron generated from the primary beam. The beam drifting problem of the electron beam optical system for the long time operation is observed. The characteristic of backscattered electron in of Gaussian distribution is simulated on quadrant cell of SPD. The variations of quadrant cell signal in experiment can be analysis through the simulation. Besides, Backscattered Electron Image (BEI) is built through deflection coil scanning and makes it possible to forming an image in the developing massively parallel mask-less lithography system (MPML2).