Date of Award

1-1-2012

Language

English

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College/School/Department

Department of Nanoscale Science and Engineering

Program

Nanoscale Engineering

Content Description

1 online resource (vii, 56 pages) : illustrations (some color)

Dissertation/Thesis Chair

Robert Geer

Committee Members

Kathleen Dunn, Gregory Denbeaux, Abbas Rastegar, Bradley Thiel

Keywords

Defect, Extreme Ultraviolet, Lithography, Planarization, Extreme ultraviolet lithography, Chemical mechanical planarization, Masks (Electronics), Surfaces (Technology)

Subject Categories

Nanoscience and Nanotechnology

Abstract

A modified CMP process was investigated and developed with the goal of removing surface defects (nanoscale depressions or `pits') from quartz mask blank substrates. Initially, quartz glass wafers were evaluated to observe surface roughness and defect introduction due to low down-force CMP processing. Following analysis of quartz glass wafers subjected to such processing it was determined that a CMP-based processing for pit removal of maskblank substrates was potentially viable. Consequently, a specially-designed mask carrier for investigating and developing CMP-based defect removal from EUV maskblank substrates was mounted on a Strasbaugh 6DS-SP CMP laboratory tool. A series of experiments was performed in order to investigate CMP-based pit removal with respect to CMP polish parameters, slurry dilution ratio, and polish time. For these experiments, additional surface pitting defects were generated on a number of maskblank substrates for the purpose of investigating the ability of a modified CMP process in removing said defects. The defects were generated using an ozonated DI water solution in concert with SC1 in a megasonic targeted cleaning system. After each polishing experiment, the mask substrates were cleaned using a standard cleaning process before AFM analysis to quantitatively measure pit modification and removal. Based on topographic analysis of pit defects (pre- and post-CMP) it was determined that chemical mechanical planarization was an effective route for pit defect removal from EUV maskblank substrates. Furthermore, it was observed that plate-bowing effects linked to the backpressure being used to hold the mask substrate in the modified carrier resulted in a radial dependence in the pitting defect removal data. Modification of the backpressure profile was sufficient to substantially reduce radial dependence in the pit defect removal data. It is noted that removal of particles from the maskblank substrate surface introduced by the CMP process requires further optimization.

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