Optimization of monomer content and degree of linearity in lithographically interesting novolac copolymers using NMR spectroscopy

Abstract

In view of the current realization that nanoscale fabrication of VLSI’s can only be met through careful design and engineering of the matrix polymers of DNQ-novolac photoresists, three m-/ p-cresol based novolac copolymers have been synthesized and characterized using 1-D and 2-D 1H and 13C NMR techniques. The ‘high ortho’ ‘tandem type’ novolac resins with optimum m-/ p-cresol content and optimum base solubility are demonstrated to be important for obtaining well-resolved pattern formation using positive photoresists. Lithographic performance of negative photoresist is shown to be critically determined by the strong base resistance of the novolac resins and offer an important guideline for the preparation of better performing photoresists. The applied NMR methodologies are used to formulate quantitation of polymer microstructure. These methodologies could also be successfully applied to refine the calculation of different precursor amount in the polymer skeleton.