碳化硼介面層於鉬/矽極紫光微影多層膜反射鏡中的熱與光學性質之研究

Abstract

本論文研究在於鉬矽多層膜中加入碳化硼當作中介層，試圖藉此增加極紫光微影應用下鉬矽多層膜鏡的熱與光學性質。對於多層膜反射鏡層結構進行了設計及模擬，之後以磁控濺鍍技術對各層鍍膜。為了得到更密集的鍍膜堆疊我們將鍍膜參數進行優化。穿透式電子顯微鏡(TEM)的剖面圖指出在純鉬矽多層膜的介面有模糊地帶產生，但在有著硼化碳的多層膜的介面是清楚平整。X射線光電子能譜(XPS)的縱深分析中同樣也指出在純鉬矽的架構中，鉬與矽的元素百分比的振幅交替的變化且強度振幅較小；然而，在有著硼化碳的多層膜的鉬與矽元素百分比的振幅比例相較更為明顯。將純鉬矽多層膜以及含有硼化碳的鉬矽多層膜退火至400度一個小時也可以發現同樣的現象。在TEM與XPS的結果中指出搭配著硼化碳的多層膜可以有效地降低鉬矽間的擴散現象，藉此可能可以改變多層膜在高通量的EUV照射下的光學表現。 本論文多層膜反射率量測是使用同步輻射光源。最高反射率的多層膜為40膜堆含有硼化碳的多層膜，反射率接近46%(模擬值反射率70%)。由TEM分析得知多層膜主要偏差來自於厚度誤差。儘管精確的膜厚控制是多層膜製程的關鍵，初步研究提出含有硼化碳作為中介層的鉬矽多層膜是有潛力作為EUVL上光學與熱學性能的應用。

In this study, boron carbide (B¬4C) was added in the Mo/Si multilayer as an interlayer, attempting to enhance the thermal and optical properties of the Mo/Si multilayer mirror in EUVL (Extreme ultraviolet lithography) application. The layer structures of the multilayer mirrors were designed and simulated, and then deposited layer-by-layer with magnetron sputtering technique. The sputtering parameters were optimized to give a dense deposit with high surface quality. Cross-section TEM images show that the interfaces between Mo and Si are blurred in pure Mo/Si multilayer, but are clear in B¬4C-added multilayer. The depth profiles of XPS analysis also indicate that the concentration of Mo and Si change slightly and alternatively in the pure Mo/Si multilayer; however, the Mo/Si composition change obviously in the B-4C-added multilayer. These phenomena are more pronounced when the pure Mo/Si and B-4C-added multilayers were annealed at 400oC for one hour. The TEM and XPS results clearly indicate that the added B¬4C interlayer can effectively retard the diffusion between the Mo/Si layers, and then might improve its optical performance under high-flux EUV irradiation. The EUV reflectance of the prepared multilayer mirrors was also measured with a reflectometer using synchrotron EUV as the light source. The highest reflectance of the B¬4C-added multilayer (40 stacks) was about 46%, lower than the simulated value of 70%. This deviation mainly attribute to the incorrect film thickness as observed in the TEM image. Although precise thickness control is very critical for a good multilayer mirror, this preliminary study has presented that B¬4C can be used as a potential interlayer to improve the thermal and optical performance of the Mo/Si multilayer in EUVL application.