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A Novel Inorganic Pellicle for 157nm lithography

IP.com Disclosure Number: IPCOM000032870D
Original Publication Date: 2004-Nov-16
Included in the Prior Art Database: 2004-Nov-16
Document File: 5 page(s) / 44K

Publishing Venue

Motorola

Related People

James Wasson: AUTHOR

Abstract

The industrial effort on lithography pellicles has been focused on extending the existing soft pellicle technology for use with 157nm reticles. Several, perhaps all, organic materials that have been investigated either "chemically darken" or breakdown under 157nm or 7.9eV photon irradiation resulting in either an opaque pellicle and/or physical disintegration of the pellicle. A discussion of material properties is presented covering electronic band gap and its relation to transmission. Also discussed is how the imaginary component of the dielectric function can be used to screen materials for transmission at 157nm without having to reduce the data to n & k and/or having to create a membrane for transmission measurement. The 157nm pellicle issue has initiated an investigation of inorganic materials that could be used to form a thin membrane pellicle for 157nm reticles. Notably, a thin membrane material of SiOF is being studied but has not yielded a pellicle with sufficient transmission at 157nm. The lack of transmission at 157nm is possibly due to surface/interface contaminates that may have reacted with excess fluorine producing a large extinction coefficient material. Another technique to form a high transmission 157nm pellicle is proposed with possible methods for implementation. The technique utilizes H2 in a SiO2 matrix and has been tested with bulk material (e.g. ~5-mm thick fused silicia) to produce lens material for 157nm equipment. The quest for a thin membrane pellicle material for 157nm will surely not be easy or simple but it is worth the effort if it enables significantly lower cost reticles for future IC technology nodes.

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A Novel Inorganic Pellicle for 157nm lithography

James Wasson

Abstract

                    The industrial effort on lithography pellicles has been focused on extending the existing soft pellicle technology for use with 157nm reticles.  Several, perhaps all, organic materials that have been investigated either “chemically darken” or breakdown under 157nm or 7.9eV photon irradiation resulting in either an opaque pellicle and/or physical disintegration of the pellicle.  A discussion of material properties is presented covering electronic band gap and its relation to transmission.  Also discussed is how the imaginary component of the dielectric function can be used to screen materials for transmission at 157nm without having to reduce the data to n & k and/or having to create a membrane for transmission measurement.  The 157nm pellicle issue has initiated an investigation of inorganic materials that could be used to form a thin membrane pellicle for 157nm reticles.  Notably, a thin membrane material of SiOF is being studied but has not yielded a pellicle with sufficient transmission at 157nm.  The lack of transmission at 157nm is possibly due to surface/interface contaminates that may have reacted with excess fluorine producing a large extinction coefficient material.  Another technique to form a high transmission 157nm pellicle is proposed with possible methods for implementation.  The technique utilizes H2 in a SiO2 matrix and has been tested with bulk material (e.g. ~5-mm thick fused silicia) to produce lens material for 157nm equipment.  The quest for a thin membrane pellicle material for 157nm will surely not be easy or simple but it is worth the effort if it enables significantly lower cost reticles for future IC technology nodes.

Introduction

                    The industrial effort on lithography pellicles has been focused on extending the existing soft pellicle technology for use with 157nm reticles.  Several, perhaps all, organic materials that have been investigated either “chemically darken” or breakdown under 157nm or 7.9eV photon irradiation resulting in either an opaque pellicle and/or physical disintegration of the pellicle.[1],[2],[3],[4]  This white paper will focus on possible inorganic materials for future experimental evaluation to form a self-supporting membrane pellicle.  There are four main criteria the material must meet to be considered as a possible 157nm pellicle.  The material must be transparent at 157nm; growth of the appropriate phase and crystal structure must be achievable on a Si substrate; the thin film stress of the material must be tensile; and the exposed surfaces of membrane material must be chemically stable, preferably with low RMS surface roughness. 

                    There are four main groups of inorganic materials from which membranes could be formed; carbides, nitrides, oxides and fluorides.  Perhaps no single material can meet all four criteria simultaneously.  In...