Polymers for Next Generation Lithography

Since the invention of microlithography there has been an exponential increase in the speed and performance of electronic devices with smaller and smaller arrays. Since then, the semiconductor industry has relied on electron beam lithography for sub-micron patterning of integrated circuits. Materials with unique properties are required to meet the needs of the lithography industry. Scientists are modifying the properties of resist materials by synthesizing new polymers to enhance lithographic performance. PMMA is one of the best e-beam resists, but suffers from fundamental drawback of poor radiation sensitivity, brittle film formation and poor resistance to plasma etching, making it a bad choice for the process of lithography. This can be partially offset by functionalizing with more stable pendant groups. We have selected substituted N-methacryloyloxy phthalimide, containing cycloimido group as a pendant, which is strong enough to give sufficient thermal stability, at the same time expected to be sensitive to electron beam exposure because of the labile N - 0 bond. Electronic substituents on the cycloimido group aid in the cleavage of this bond. Electron withdrawing chloro and nitro groups weakens the N - 0 bond and copolymers of these monomers with methyl methacrylate showed sufficiently high mechanical properties which allow them to survive the semiconductor processing, yet are sensitive to degradation. The GPC results showed that most of the polymers had molecular weight ~18,000 g/mol with a PDI of ~2.0. The electron beam lithography studies of polymer with nitro substitution on the pendant group showed the least line width of 0.54 µm among the four selected polymers. Least dosage (251 µC/cm2) with fastest writing speed (1000 µsec/mil) was observed for the polymer with methyl substitution. These two polymers were observed to be the promising materials as positive photoresists and can be studied for further evaluation of lithographic properties.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Chemistry

Grantor

Texas State University-San Marcos

Year dc:date.issued

2006

Author dc:creator

• Guntupalli, Maheedhar

Advisor dc:contributor.advisor

• Cassidy, Patrick E.

Committee members dc:contributor.committeemember

• Wilkins, Cletus W.
• Booth, Chad Jeffrey

• polymers
• lithography
• electron beam
• science and industry

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10877/10181

OAI identifier oai:identifier

oai:digital.library.txst.edu:10877/10181