Fabrication of a Highly Dense Line Patterned Polystyrene Brush on Silicon Surfaces Using Very Large Scale Integration Processing

Abstract

In this study we used a novel fabrication process, involving a very large scale integration and isotropic oxygen plasma treatment to generate highly dense lines and well-defined patterns of polystyrene (PS) brushes on patterned Si(100) surfaces. We defined trench patterns having a duty ratio of 1:1 on the Si surface using electron beam lithography and then applied isotropic oxygen plasma (IOPT) to treat the bottom of the trenches. The resolution of the line patterns of the PS brushes approached 160 nm, with a duty ratio of 1:1. We established the surface grafting polymerization kinetics of the PS chains on the Si surface by analyzing their thicknesses and number-average molecular weights (Mn). The propagation rate (kp) and active grafting species deactivation rate (kd) had values of 3.3 × 10−2 s−1 M−1 and 7.5 × 10−5 s−1, respectively. The measured thicknesses (ellipsometry) and analyzed values of Mn (gel permeation chromatography) of the corresponding “free” PS fit well to the polymerization kinetics model. In addition, we used friction coefficients to verify the structures of the dense lines of patterned PS brushes after immersion in various solvents. We observed different patterns and friction coefficients for the surfaces presenting dense lines of PS brushes grafted from 160 nm wide trenches for 26 h, after immersion in water and toluene, respectively. Thus, the densely patterned PS brushes on the Si surface exhibited solvent-responsive switching properties.