- 學位論文
用於直寫式極紫外光微影系統之高頻高反射率快門建置
Construction of a High Frequency and High Reflectance Shutter for Direct Write EUV Lithography System
摘要
隨著微影技術的進步，曝光所使用的光源波長不斷降低，繼深紫外光微影（DUVL，193 nm）之後，極紫外光微影（EUVL，13.5 nm）成為下個世代微影技術的主流之一，然而，投影式極紫外光微影系統存在光罩精度要求極高的問題，因此發展出直寫式極紫外光微影系統。而本論文的主要目標是建置一直寫式極紫外光微影系統之快門，以有效地將EUV幅射能量適時地做開關的動作。然而，因極紫外光波長較短的關係，大部分的材料對其都有強吸收的現象，若以吸收方式製作微影系統中之快門時，需考慮結構吸收高能輻射後所造成的升溫問題，致使高精度微影系統於曝寫過程中產生位置的誤差（Pattern placement error, PPE）或是圖像的模糊（Image blur）。 因此，本論文提出以高反射率來取代材料吸收的方法，以減小微影系統中因光開關產生之溫升，而造成曝光系統精度驟減的問題。由於光開關的應用並不像光罩或聚光用反射鏡必須以近垂直的角度入射，為了降低製程上的複雜性，本論文採用單一層之鉬薄膜材料，以斜角入射的方式提高反射率，大幅衰減快門結構所需吸收的幅射能量。 本論文先期以雷射做為光源，建立一套反射率及穿透率自動化量測系統，以驗證光源入射角對材料反射率之提升，且以多次實驗結果證實本實驗之再現性與可靠度；並藉由量測後之反射角搭配積層式壓電做為致動器，量測雷射光源之高頻反射訊號。結果顯示，固定入射角83°時能得到反射率50%，且開關頻率最高能夠達到10 kHz，驗證了以反射能量的方式做為光源開關之可行性。最後於國家同步輻射研究中心（NSRRC），以極紫外光（EUV）作為光源，量測單層100 nm及200 nm之鉬與鋁薄膜材料，在不同入射角下之反射率曲線。實驗結果驗證了本論文所設計之單層薄膜結構於高反射角時確實有反射率大幅提升之現象，並比較出鉬在入射角約65°即有明顯的反射率提高，相較於鋁的75°，鉬的低角度反射率起始角較有利於微影系統機構之安裝。
並列摘要
With the recent progress of lithography technology, the wavelengths of light sources for exposure have been continuously reduced. After Deep Ultraviolet Lithography (DUVL) technology, Extreme Ultraviolet Lithography (EUVL) seems to be one of the most promising techniques for next generation lithography methods. The target of this thesis is to build a high speed shutter, which is able to switch the EUV light source rapidly in the direct-write EUV lithography system. However, the wavelength (13.5 nm) of the EUV is extremely short, so that beam energy will be absorbed by most materials. For this reason, the construction of high frequency shutter using the absorption method may cause temperature to rise and result in pattern placement error and image blur. Therefore, this thesis proposes to use reflection instead of absorption to construct a high speed shutter for an EUVL system. In order to simplify the process and reduce the mass of the shutter, we suggest using single layer molybdenum thin film material as our reflector and operating at a high incident angle to reduce the energy absorptance. In the first step of the process, we utilized a blue ray laser as the light source, and built up an automatic measurement system to measure the reflectance and absorptance, which can be used to find the total reflection angle. The repeatability of the experiment is also verified. According to the experimental results, we found the optimal reflectivity to be about 50% with an 83 degree incident angle. We fixed this angle and used piezo-stack as the actuator to measure the high frequency reflection signal of the laser. A 10 kHz switching signal is obtained, which verifies the feasibility of using the reflection method as optical switches. Finally, we measured the reflectance curve with different thicknesses of molybdenum and aluminum thin film samples using an EUV light source in NSRRC. According to the results of this experiment, the starting angle for molybdenum was about 65 degrees smaller than that of aluminum, which may be beneficial to the installation of the shutter. This experiment also proves that using single layer molybdenum thin film with a high incident angle will lead to a high reflection phenomenon.