Plasma-surface interactions of model polymers for advanced photoresist systems
by Engelmann, Sebastian Ulrich, Ph.D., UNIVERSITY OF MARYLAND, COLLEGE PARK, 2008, 241 pages; 3339448

Abstract:

Plasma processing of advanced photoresist (PR) materials is a critical step in nano-manufacturing. We have studied the interactions of PRs and polymers in fluorocarbon/Ar discharges. The effects of process time, PR material, bias and source power, pressure and gas chemistry (C4F8/Ar, CF4/Ar and CF4/H2/Ar) were studied by ellipsometry, atomic force microscopy and x-ray photoelectron spectroscopy. Additionally, patterned structures of 193nm PR were examined using scanning electron microscopy. Polymer destruction in the top surface, oxygen and hydrogen loss along with fluorination were observed for all materials initially, which was followed by steady state etch conditions. A strong dependence of plasma-induced surface chemical and morphological changes on polymer structure was observed. In particular, the adamantane group of 193 nm PR showed poor stability. Two linked mechanisms for the roughening behavior of the films during processing were identified: A physical pattern transfer mechanism enhances initial roughness by nonuniform removal. Additional to that, roughness formation occurred linear to the energy density deposited during processing. For adamantyl polymers, a higher roughening constant was found. Additionally, fluorocarbon (FC) deposition on the damaged PR affected roughening in two opposing ways: Ion-induced mixing with the damaged PR increased roughening, whereas for simple FC precursor deposition a reduction of roughness was seen. Fluorination of the PR surfaces using plasma increased etching yields, which were found to improve the roughness of 193nm PR after etch. The fluorination of the PR prevented the formation of characteristic small scale roughness features at the cost of large scale roughness introduction. Use of low energy density processes suppressed the roughness growth by ion-induced transfer. Examining 3-dimensional trenches and contact holes patterned in PR showed that the sidewall roughness changed with process parameters similar to that seen for blanket films. The close correlation suggested that our model of polymer surface roughening also applies to resist sidewall evolution during etch. All process conditions can be combined in the energy density roughening model. Even for various feedgas chemistries adamantyl containing polymers show enhanced roughening rates, suggesting that the instability of the adamantyl structure used in 193nm PR polymers is the performance limiting factor for processing PR materials.

 
AdviserGottlieb S. Oehrlein
SchoolUNIVERSITY OF MARYLAND, COLLEGE PARK
SourceDAI/B 70-01, p. , Mar 2009
Source TypeDissertation
SubjectsMaterials Science
Publication Number3339448
Adobe PDF Access the complete dissertation:
 

» Find an electronic copy at your library.
  Use the link below to access a full citation record of this graduate work:
  http://gateway.proquest.com/openurl%3furl_ver=Z39.88-2004%26res_dat=xri:pqdiss%26rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation%26rft_dat=xri:pqdiss:3339448
  If your library subscribes to the ProQuest Dissertations & Theses (PQDT) database, you may be entitled to a free electronic version of this graduate work. If not, you will have the option to purchase one, and access a 24 page preview for free (if available).

About ProQuest Dissertations & Theses
With over 2.3 million records, the ProQuest Dissertations & Theses (PQDT) database is the most comprehensive collection of dissertations and theses in the world. It is the database of record for graduate research.

The database includes citations of graduate works ranging from the first U.S. dissertation, accepted in 1861, to those accepted as recently as last semester. Of the 2.3 million graduate works included in the database, ProQuest offers more than 1.9 million in full text formats. Of those, over 860,000 are available in PDF format. More than 60,000 dissertations and theses are added to the database each year.

If you have questions, please feel free to visit the ProQuest Web site - http://www.proquest.com - or call ProQuest Hotline Customer Support at 1-800-521-3042.