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Silicon membrane mask blanks for X-ray and ion projection lithography

 

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Japanese Journal of Applied Physics. Part 1, Regular papers, short notes and review papers 29 (1990), No.11, pp.2605-2609
ISSN: 0021-4922
Micro Process Conference <1990, Chiba>
English
Journal Article, Conference Paper
Fraunhofer ISIT ()
anodic bonding; experimental design; flatness optimization; ion projection; mask blank; membrane fabrication; membrane homogeneity; particle density; silicon membrane; X-ray lithography

Abstract
In the subquarter-micron range, X-ray lithography and demagnifying ion projection are promising printing techniques. For both methods special designed masks are needed which have to fulfil strong requirements including flatness, stability, defect density, transparency and surface properties. In this paper we would like to demonstrate that silicon membrane based mask blanks are well suited to meet most of these demands. Furthermore, silicon as membrane material offers the advantage to make use of the experience in semiconductor process technology. A fabrication sequence has been developed, based on silicon epitaxial growing, clean compatible wet etching and anodic bonding techniques. The application of this process and the results of the blank characterization are presented and discussed. In the subquarter-micron range, X-ray lithography and demagnifying ion projection are promising printing techniques. For both methods special designed masks are needed which have to fulfil strong requi rements including flatness, stability, defect density, transparency, and surface properties. In this paper we would like to demonstrate that silicon membrane based mask blanks are well suited to meet most of these demands. Furthermore, silicon as membrane material offers the advantage to make use of the experience in semiconductor process technology. A fabrication sequence has been developed, based on silicon epitaxial growing, clean-room compatible wet etching and anodic bonding techniques. Highly boron doped silicon layers with germanium as counter-dopant offer the possibility of stress engineering. An etching process on the base of KOH/IPA is applied in a clean-room environment to decrease the particle density during etching. A very comfortable bonding process for fixing silicon membra nes on glass ring carriers was optimized and yields super flat mask blanks. The application of this process and the results of the blank characterization are presented and discussed.

: http://publica.fraunhofer.de/documents/PX-33504.html