IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Photonics Materials Topical Conference Thursday Sessions
       Session PH-ThA

Paper PH-ThA7
Application of Photosensitive Methylsilsesquiazane(MSZ) to Lithographic Fabrication of Three Dimensional Periodic Structures

Thursday, November 1, 2001, 4:00 pm, Room 120

Session: Photonic Materials: Applications and Processing
Presenter: T. Matsuura, Tohoku University, Japan
Authors: T. Matsuura, Tohoku University, Japan
A. Yamada, Tohoku University, Japan
J. Murota, Tohoku University, Japan
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|> We have proposed a novel lithographic process for fabricating three dimensional periodic structures.@footnote 1@ The essence of the process is that multiple layers of photoresist are coated on the wafer with each layer being exposed with a different pattern without development, and finally after all the photoresist layers are exposed they are developed from upper ones. In this paper, we have applied photosensitive methylsilsesquiazane (MSZ) to enhance the potential of the process. MSZ was spin-coated on the Si wafer, pre-baked at 90°C, and exposed to UV light with a lines-&-spaces mask. Then, the wafer was kept in a moisture case. MSZ contains Si-N bonds, which are converted to alkaline-soluble Si-O bonds after UV-generated photoacid and hydrolysis. Without development of the MSZ at this time, 20nm-thick aluminum is vacuum-evaporated, and then the second photosensitive MSZ was coated. Here, the aluminum layer suppresses mixing of the MSZ layers during coating and penetration of the light to the first layer during exposing the second layer with a different pattern. After these coating and pre-patterning processes are repeated for desired times, the wafers were dipped in a standard developer (TMAH) for MSZ. The areas of the thin aluminum layers wetted by TMAH are also etched, and a periodically stacked structure is formed. When the wafer is cured at 400°C in O@sub 2@, the remaining MSZ is converted directly to methylsilsesquioxane (MSQ) containing stable Si-O-Si networks. As remarkable merits, the present process is simple, easy, and fast, and it possesses intentional-defect-introduction-ability and compatibility with microlithography technology. @FootnoteText@ @footnote 1@ Matsuura et.al, SSDM 2000, p.542.