微影光罩的不同清洗方法的效果比較

Abstract

在半導體相關製程中，如何減少由黃光微影製程導入的缺陷，一直是極大的挑戰。當線寬持續縮小，使得曝光波長從早期的G-line（436nm），進展到現今常用I-line（365nm）、KrF （248nm）及ArF （193nm）的製程技術，如此波長越來越短的發展趨勢下，在光徑上所出現的污染更是容易被轉移至晶圓上，而造成晶圓製造良率的下降。 其中一種為霧狀污染，被稱為Haze，研究指出其成份為硫酸銨（(NH4)2SO4），而此類污染主要來自光罩清潔的殘留物質、或是光罩保護膜（photo mask pellicle）、貯存環境以及製造環境。其中來自光罩清洗過程的硫離子或銨離子殘留，被視為Haze形成的主要貢獻者，故國內外學者著手改善光罩清洗方法，以降低Haze的產生。 目前已發表的改善方法各有其優缺點，此研究整理比較各光罩清洗方法的離子殘留去除效率，以及清洗後對於光學性質的影響，包括相損失（phase loss）、穿透度（transmission），期能找出最佳的清洗方法，為接下來的世代－極紫外光微影技術（EUVL）及浸潤式微影技術（Immersion）提供清洗方法相關條件之參考選擇。

How to reduce the formation of photo-induced defect has becomes a big challenge in the manufacture of semiconductors. When the critical dimension gets smaller and smaller, the exposure wavelength changed from G-line (436nm) in the early years, then it comes the I-line (365nm)、DUV KrF(248nm) and ArF (193nm). With the trend of shorter wavelength, the contamination on mask will become easier to transfer failed pattern to wafer, and cause the yield to drop. This kind of defect is called “Haze”. The sources of these types of contamination are from photo mask itself, photo mask pellicle, mask cleaning process residuals or manufacture process. Many researchers have focused on the development of new mask cleaning methods to eliminate haze. A lot of improve methods have been published. This paper will discuss the effectiveness of mask cleaning methods and compare the change of optical properties, like phase angle and transmittance, and ion residuals with these methods to indentify the most optimal method. It is hoped that this study is able to provide choices on the mask cleaning conditions for the next generation cleaning method: EUVL and Immersion Lithograph.