ISSN:
1042-7147
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
The synthesis and lithographic characterization of the three positional isomers of polyhydroxystyrene is described. Large differences in dissolution rates are found as a function of the position of the hydroxy group, which are explained in terms of intra- vs. intermolecular hydrogen bonding and steric shielding of the hydroxy group by the polymer backbone. In plots of log (dissolution rate) vs. developer strength, linear plots are observed for the 2- and 4-isomers, while for poly(3-hydroxystyrene), a break occurs in the plot, leading to two linear regions. While the 2-hydroxy isomer is too slow and the 4-hydroxy isomer too fast for use in conventional dissolution inhibition systems, the copolymerization of both allows any dissolution rate between these extremes to be chosen ( “dial a dissolution rate” copolymers). Determination of the copolymerization parameters of the corresponding 4- and 2-acetoxystyrene precursors by the method of Kelen and Tüdös shows the polymerization to be nearly ideal and azeotropic (r1 = 0.76, r2 = 0.94). Analysis of the dissolution rates as a function of developer strength according to the Huang-Reiser-Kwei equation shows that the critical concentrations c* are a linear function of copolymer composition, whereas the penetration exponents in show a minimum near unity in the region of the 1 : 1 copolymer, down from the values of 3.2-3.3 observed for all three homopolymers. The 1 : 1 copolymer shows a dissolution rate comparable to novolak resins, and when formulated into a photoresist together with a diazonaphthoquinone sensitizer resolved 0.4μm features at a dose of 340 mJ/cm2. The thermal flow resistance of the resist was found to be improved over that of novolak resists although not to the degree expected from the increased Tg of the 1:1 copolymer.
Additional Material:
12 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pat.1994.220050105
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