Study of nano-patterning using silicon-containing materials

Abstract

Fabrication of Nano-Patterning Using Silicon-Containing Materials by Top-Down Approaches

The chemically amplified (CA) system utilizing acid-catalyzed reactions has been widely used in the common photoresists due to its high photo-sensitivity. Exposure of the resist generates acid within the polymer film to catalyze the thermal deprotection or cross-linking reactions. However, the common CA system has produced serious problems such as the appearance of T-top and foot profiles caused by air-borne or substrate contamination, and post-exposure delay (PED), which hinder fabrication of nanometer-scale patterns. To overcome these problems of the CA system, the non-chemically amplified (non-CA) systems have been proposed as potential solutions. A top surface imaging (TSI) approach offers a higher resolution than a conventional photolithography because of the anisotropic pattern transfer of a thin silicon-containing top layer into the thick underlying polymer film. Despite all those advantages of TSI, controlling of the silylation reaction, which is the key process in TSI, on the specific region is still challenged. The insufficient reaction of silicon-containing moieties causes problems with the edge and surface roughness after dry etching. Therefore, Silicon-containing photoresists are gaining increasing interest for an imaging layer in the bilayer system. In this report, we propose a new imaging method by combining an interfacial imaging reaction with thin layer imaging. The acid produced in the exposed areas of the bottom chemically amplified resist layer induces the crosslinking reaction of the top thin layer. Also, we propose a novel photoresists using blends of polymers containing photoactive diazo-groups and amine-functionalized silicon compounds to adjust the properties of the imaging layer to adjust easily the properties of the imaging layer without post-exposure delay problems.

Fabrication of Nano-Patterning Using Silicon-Containing Materials by Top-Down and Bottom-Up Approaches

Block copolymer lithography has attracted much attention because it is easier than conventional lithography in the process of nanofabrication. Particularly, nanostructures of amphiphilic block copolymers are attractive because each block can be designed to be selectively responsive to different external stimuli. However, amphiphilic block copolymers tend to self-associate in aqueous solution and form micelles. It would be an excellent alternative for making thin film of amphiphilic block copolymer to utilize deprotection reaction during thermal annealing process simply by starting with protected block copolymer thin film. First, highly dense Au nanoparticles arrays were fabricated via a selective chemical reaction with a functionalized block copolymer template. Polystyrene-b-poly(acrylic acid/acrylic anhydride) (PS-b-PAA/AN) thin films on an SU-8 photoresist, generated from polystyrene-b-poly(tert-butylacrylate) (PS-b-PtBA) by acid-catalyzed thermal deprotection, were used as templates. Also, a novel patterning technique is proposed here that combines a top down approach based on photolithography and a bottom-up strategy through self-assembly of multifunctional molecules. Self-assembled monolayers (SAMs) offer unique opportunities to promote or resist the adhesion of specific substances and are some of the most promising subjects of current research, including molecular electronics, nanolithography, and sensors. The generation of chemical surface patterns is an active research area in biotechnology and nanotechnology due to the decreased amount of analyte material required for successful analysis. However, these techniques have some inherent drawbacks, such as molecular intercalation and side reactions. To promote the fabrication of different functional patterns, we design silicon oxide ($SiO_2$) prepatterns on an Au substrate via silicon-containing negative photoresist lithography. The direct-prepatterned $SiO_2$ is further subjected to site-specific chemical functionalization of the pattern with a combination of silanes and thiols to selectively self-assemble them onto $SiO_2$ and Au, respectively. The functional groups are very suitable for the selective adsorption of various materials from nanoparticles to biomolecules.