發展下一世代環保微影光罩結構材料

Abstract

本論文使用氮化矽來製作光罩，試圖以環境友善材料，取代污染較嚴重之鉻、鉬等材料。我們利用化學氣相沈積方式，控制SiH4及NH3氣體流量比例，以改變氮化矽組成成分，進而控制氮化矽的光學常數。經過模擬計算，得知數組合適的光學常數與厚度。為了與市售光罩比較，實驗中我們選定氣體流量比例50：5來製作氮化矽，光學常數為（3.514, 0.803），厚度為75.2nm，作為i-line衰減式相位移光罩之相位移層。在製作光罩的同時，我們也利用UV-VIS測定光罩穿透率約為6％，確保其擁有弱穿透的性質。同時以SEM、AFM觀察薄膜形貌，測得知粗糙度約為0.32nm，遠遠優於市售二元式鉻膜光罩。並以FITR、XPS等儀器分析薄膜組成成分，觀察薄膜化學鍵結變化，以確認此Si-rich氮化矽薄膜應為SiN0.22，同時驗證並確保薄膜成份穩定，不會因為批次或厚度不同而改變。最後以i-line曝光機曝光驗證，比較實驗製作之衰減式相位移光罩與二元式鉻膜光罩的解析能力，結果顯示，本實驗製作之衰減式相位移光罩對密集洞的解析能力有明顯改善，可以製作出0.56μm間距的密集洞，相較於二元式鉻膜光罩的0.60μm間距密集洞優異許多。綜合實驗結果，証明此材料可為下一世代環保微影光罩結構材料。

In this thesis, the environment friendly materials, silicon nitride was used to replace general chromium film used for binary mask as well as to replace molydium silicide embedded material for attenuating phase-shifting mask (Att-PSM) in lithography. The optical properties of the nitride film was controlled well by plasma enhanced chemical vapor deposition (PECVD). The film stack with suitable optical properties (3.514, 0.803) and thickness 75.2nm was deposited by PECVD under 50 sccm SiH4 with 5 sccm NH3 gas flow rate for i-line Att-PSM usage. The transmittance of the Att-PSM measured by ultraviolet-visible spectroscopy is about 6％. Topography and roughness were observed and determined by scanning electron microscope and atomic force microscope that is result in 0.32 nm. The infrared absorption spectra of the films were measured to chemical bond variation make sure film content stability by Fouier transform infrared spectroscopy. The atom concentration for silicon nitride obtained here is SiN0.22 using X-ray photoelectron spectroscopy calculation. The capability of resolution was evaluated by i-line stepper exposure. The significant improvement was shown in 0.56μm dense hole patterns more better than the 0.6μm dense hole patterns exposed by binary mask. The powerful proof of a green material for mask of next generation lithography was demonstrated.