Patterning Characteristic Control of Sol-Gel-derived Random-Structure Oligomeric Silsesquioxanes Having a Diazonaphthoquinone Derivative

Positive photosensitive materials prepared by adding a diazonaphthoquinone (DNQ) derivative to matrices of oligomeric silsesquioxanes (oligo-SQs) with random structures, including only a phenyl (Ph) substituent or both Ph and methyl (Me) substituents (wherein the Ph group content is over 50 mol. %), exhibit a high patterning ability (i.e., a high-resolution pattern formation under 10 μm). One cause of such a high patterning ability is the particularly low solubility of unexposed areas in an alkaline developer, caused by the DNQ derivative-containing oligo-SQs having over 50 mol. % of Ph group content. However, the effects of the exposed areas on the alkaline dissolution behavior, which can be another factor of high patterning ability, have not been examined yet. In this study, the effects of the Me group content on the alkali solubility of the exposed areas on the optimum exposure dose (Eop), the resolution limit, and the pattern shape were examined for a positive photosensitive material having over 50 mol. % of Ph group content. As a result, the resolution did not change with increasing Me group content but the Eop decreased, and the pattern shape tended to change from showing a protruding defect in the central portion to having a normal taper shape. Furthermore, density functional theory calculations for the oligo-SQ model compounds suggested the formation of a new hydroxyl (OH) group domain that includes Me groups in oligo-SQs with increasing Me group content. This new type of OH group domain differs from that derived from oligo-SQs possessing only Ph groups. Moreover, the results suggested that the intramolecular hydrogen bonding was weaker in the new domain than in the domain from oligo-SQs containing only the Ph groups and that the intermolecular interaction between the domain and the DNQ was also weak. The weak intermolecular interaction seemed to be the cause of the high alkali solubility in the exposed areas.