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Proceedings Paper

Electron Beam Lithographic Evaluation And Chain Scissioning Yields Of Itaconate Resists
Author(s): Y. M.N. Namaste; S. K. Obendorf; C. C. Anderson; F. Rodriguez
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Paper Abstract

Previous work has demonstrated that copolymers of itaconic acid with methyl methacrylate, P(ItA-MMA), are promising positive working electron beam resists.1'2 However, synthesis of itaconic acid copolymers with molecular weights greater than 250,000 or itaconic acid contents higher than 50% is difficult, and these copolymers are quite sensitive to process conditions such as prebake temperature and aging times. To overcome these limitations and to develop resist materials with improved sensitivity, alkyl ester derivatives of itaconic acid have been synthesized, both as homopolymers and as copolymers with methyl methacrylate. In the present work, the electron-beam chain scissioning yields, G(s), of these derivatives have been determined, and the most promising of these copolymers and homopolymers have been evaluated as electron beam resists in terms of sensitivity, contrast, resolution, and thermal stability. The G(s) values of the alkyl itaconates depend greatly on the structure of the alkyl group. It was found that mono-alkyl itaconates yield polymers with G(s) values several times greater than the corresponding di-alkyl itaconates. The mono-methyl itaconate (MeI) copolymers with methyl methacrylate are very promising resist materials with high sensitivities. Methyl itaconate was polymerized with methyl methacrylate with compositions ranging from 20 to 85% MeI content and molecular weights well above one million. These copolymers are more sensitive than the itaconic acid copolymers and less dependent on prebake conditions and aging times. Sensitivities are presented for a series of MMA-MeI copolymers as well as for the MeI homopolymer. Patterns exposed with P(MMA-73 mole % MeI) at 4 pC/cm4 (20 KV) were developed with less than 10% thinning of the unexposed resist and with a contrast (v) of 2. Vertical walls were observed for 1 pm wide lines using P(MMA - 73% MeI) at a dose of about 6 μC/cm2.

Paper Details

Date Published: 21 May 1984
PDF: 7 pages
Proc. SPIE 0469, Advances in Resist Technology I, (21 May 1984); doi: 10.1117/12.941788
Show Author Affiliations
Y. M.N. Namaste, Cornell University (United States)
S. K. Obendorf, Cornell University (United States)
C. C. Anderson, Cornell University (United States)
F. Rodriguez, Cornell University (United States)

Published in SPIE Proceedings Vol. 0469:
Advances in Resist Technology I
C. Grant Willson, Editor(s)

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