A Novel Inorganic Pellicle for 157nm lithography
Original Publication Date: 2004-Nov-16
Included in the Prior Art Database: 2004-Nov-16
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.