In photolithography, light is applied to a substrate to change its surface chemistry. The process can be used in nanofabrication to pattern surfaces for the self assembly of diblock copolymers which consist of two chemically different polymer chains connected at one end by a covalent bond that can spontaneously form ordered structures at the molecular scale. The proposed technology iterates the standard lithographic process of diblock copolymer assembly in order to define more specific patterns for self assembly and hence obtain more control over the created patterns.
The process employs multiple resistless lithographic steps that directly change the surface energy of the resist without requiring subsequent surface modification, deposition, or plasma etch steps. In this approach the initial surface modification followed by imaging gives one a surface differentiated from the initial surface by a number of material surface properties.
A second surface modification step is employed to convert the exposed region to a third surface different from the first and the second by type of surface energies. The result of double surface modification and imaging is that three different surfaces become lithographically defined on the original material surface and as such the final surface is more prone to directed material assembly.