Design and syntheses of photoactive polymer systems capable of chemical amplification.

Title: Design and syntheses of photoactive polymer systems capable of chemical amplification.
Authors: Houlihan, Francis Michael.
Date: 1984
Abstract: A short history of the development of resist systems for use in the electronics industry is given. The shortfalls of classical resist systems are exposed, and the phenomenon of chemical amplification is shown as a possible way of circumventing these shortfalls. A review of polymeric resists showing chemical amplification is given. Polycarbonates bearing photolabile ortho-nitrobenzyl groups are shown to be theoretically capable of undergoing photodepolymerization. Several synthetic approaches to such polymer systems are presented. One of the proposed pathways leads to the desired polymer. This polymer shows the expected photochemically induced depolymerization, however the temperature differential between the depolymerization of the protected and deprotected polymer is insufficiently large to give complete development of an image. A novel approach towards the t-butyloxycarbonylation of alcohols, phenols, thiols, and enols under phase-transfer conditions is presented. This method is also extended to the t-butyloxycarbonylation of polymer bearing pendant hydroxyl groups such as novolac and poly(p-hydroxystyrene). The selective t-butyloxycarbonylation of polyfunctional molecules is also explored. Another approach in the design of photoactive polymer is achieved by the introduction in the main chain or in pendant groups of the t-BOC group, or structures resembling it, that are capable of undergoing acidolysis on irradiation in the presence of a catalytic amount of an onium salt. The introduction of t-BOC bearing pendant groups is attempted both through polymer modification of PVCLO and monomer synthesis starting from vinyl chloroformate. The synthesis of polymers having t-BOC groups directly attached to the main chain is not achieved, however polymers containing a spacer group between the main chain and the t-BOC group are prepared successfully. These polymers show the expected thermal loss of isobutene and carbon dioxide at 200$\sp\circ$C, however, on irradiation in the presence of an onium salt, acidolysis is incomplete because of the occurence of other cleavages that are not catalytic in nature. The synthesis of polymers having main chains with t-BOC-like structures in their main chain is achieved by the reaction of diimidazolides with various diols. In this way linear polycarbonates are made that contain either tertiary carbonates, or secondary benzylic carbonates in their main chain. These polymers are capable of undergoing catalytic depolymerization on irradiation in the presence of an onium salt and are currently still under study as potential resist systems.
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
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