The effect of random copolymer on the characteristic dimensions of cylinder-forming PS-b-PMMA thin films

Abstract

The block copolymer self-assembly approach has received great attention in recent years as a possible way to overcome the limits of conventional lithography and to fabricate sub-22 nm structures. At this level, precise nanometric control is crucial for technological applications and the search for a flexible and reproducible protocol is a great challenge. The polystyrene-b-poly(methylmethacrylate) (PS-b-PMMA) system, with a styrene fraction of 0.71, spontaneously separates into a periodic array of hexagonally packed PMMA cylinders embedded in a matrix of PS and, under suitable processing conditions, this is perpendicularly oriented with respect to the underlying substrate. The selective removal of the PMMA allows us to obtain a nanoporous PS matrix with well-defined pore dimensions. Perpendicular orientation of the PMMA cylinders requires surface neutralization by means of a suitable PS-r-PMMA random copolymer. The choice of the random copolymer is not trivial, because different PS-r-PMMA copolymers strongly affect the characteristics of the PS-b-PMMA film deposited on it. In this paper the effects of the selected PS-r-PMMA on the arrangement as well as on the peculiar dimensions (pore diameter, pore to pore distance) of the final nanoporous PS thin film are studied. Reliable protocols for the fabrication of a disposable polymeric mask are proposed in view of its application in advanced lithographic processes.

Ultrathin Random Copolymer-Grafted Layers for Block Copolymer Self-Assembly

“…22,23 The average pore diameter in the final polymeric film deposited on the RCP depends on the duration of the O 2 plasma treatment that is necessary to remove the RCP from the bottom of the pores and completely open the mask. 47 In this regard, a thin RCP layer would result in a relatively short O 2 plasma exposure and consequently a minimization of the pore enlargement caused by the isotropic etching. …”

Dynamic behavior in self-assembly process of cylindrical phase PS- b -PMMA block copolymer

“…They demonstrated pore diameters ranging from 20 nm to 30 nm by increasing molecular weight by a factor of two. Similarly, Andreozzi et al [23] studied the evolution of the mean pore diameter in the polymeric films as a function of the oxygen plasma irradiation time. They showed that a different compositions of the random copolymers, induced variations of the dimensions of the nanopores in the PS matrix.…”

“…The hole formation was also studied over the past. Guarini and Andreozzi [22,23] investigated the influence of process parameters on the self-assembly process for PS/ PMMA System, focusing on the distribution of the pore diameters, and the pore spacing across the film. In this article we investigate the dynamics of BCP S-A, using an in-plane analysis technique (CD-SEM) by following the evolution of the critical dimension (CD) and the hole circularity in the finale template as function of the processing parameters, which to the best of our knowledge has not been reported so far.…”

Silicon crystallization in nanodot arrays organized by block copolymer lithography

“…The PMMA cylinders were selectively removed through immersion in acetic acid bath and subsequent rinsing in deionized water. O 2 plasma treatment was subsequently used to remove the brush layer from the bottom of the nanopores and to guarantee a good adhesion between the SiO 2 substrate and the evaporated Si (Andreozzi et al 2011b). The random copolymers and the block copolymers were marked as R62, R58, and B71 where R and B stand for random and block, respectively, and the numbers represent the percent of styrene units.…”