Potential Limitations of Conventional Photomasks Due to Inherent Internal Stress — The Need for an Alternative Opaque Layer

作     者：James A. Cairns Liu-Wing Chi Andrew C. Hourd Robert P. Keatch Brian Lawrenson 

作者机构：Department of Applied Physics and Electronic & Mechanical Engineering University of Dundee Dundee Scotland 

出 版 物：《MRS Online Proceedings Library》 

年 卷 期：2011年第356卷第1期

页      面：239-244页

摘      要：Conventional photomasks consisting of chromium films on fused silica or glass substrates are widely used. However, it is becoming apparent that interfacial stress between the chromium and the transparent substrate, as well as the need for wet chemical processing for pattern production, will ultimately limit a photomask’s ability to be patterned reproducibly. An alternative approach is to chose an opaque layer which exhibits minimum interfacial stress with respect to the substrate while having the ability of being patterned by fluorocarbon gas plasma processing. This work describes the use of silicon/germanium as an alternative opaque layer, which can be deposited uniformly by co-sputtering and patterned by fluorocarbon reactive ion etching. The suitability of the material in terms of interfacial stress is demonstrated by the use of microfabricated silicon dioxide cantilever structures. In addition, the influence of Si/Ge ratio on optical properties, the plasma processing performance, and chemical compatibility with the rest of the photomask making process is described.