Area-selective deposition is a promising technique for positional self-alignment of materials at a prepatterned surface. Critical to this is the development of molecular systems that have selective surface binding and can act as templates to material growth. This paper reports how end functionalized polymers can be used to create oxide films through a grafting method. Here, we detail a facile approach for rapid grafting (in seconds) of polymer brush films with complete coverage over large areas with high uniformity (pinhole free). Subsequent conversion to an oxide (∼3−4 nm thickness) is performed via liquid-phase metal ion infiltration. Exposing the covalently grafted polymer brush (P2VP-OH) to a metal salt-solvent solution (using the Al 3+ ion as a model species) swells the polymer, facilitating ion inclusion. Early results suggest that a solvent-mediated approach to polymer film infiltration can be used to develop inorganic films in a facile process. While data shows inclusion into both large-area and patterned films, the mechanism and understanding of these have been limited. In particular, the solution-mediated process described here shows the precise tailoring of nanometer-thin polymer films that are pinhole-free and that can be activated to create semiconductor-compatible oxide films that are parallel in quality to ALD-or CVD-derived processes. A surface deactivation strategy is also realized using a hydroxyl-terminated polystyrene (PS-OH) brush that prevents the deposition of ions. We consider this strategy as a means to prevent electromigration of ions as well as the possibility of coating ALD layers.

We describe a versatile bottom-up approach to covalently and rapidly graft hydroxyl terminated poly (2-vinyl pyridine) (P2VP-OH) polymers in 60 seconds that can subsequently be used to fabricate high quality TiO2 films on silicon substrates. A facile strategy based upon room temperature titanium vapor phase infiltration of the grafted P2VP-OH polymer brushes produces TiO2 nanofilms of 2-4 nm thickness. In order to fabricate coherent inorganic films with precise thickness control, it is critical to generate a high-quality polymer brush film i.e. a complete monolayer. Definition of precise and regular polymer monolayers is straightforwardly achieved for polymers which are weakly interacting with one another and the substrate (apart from the reactive terminal group used for grafting). However this is much more challenging for reactive systems. Crucial parameters are explored including molecular weight and solution concentration for grafting dense P2VP-OH monolayers from the liquid phase with very high coverage and uniformity across wafer scale areas. Additionally, we compare the P2VP-OH polymer system with another reactive polymer PMMA-OH and a relatively non-reactive polymer PS-OH, the latter we prove to be extremely effective for surface blocking and deactivation. Our methodology provides new insight into the grafting of polymer brushes and their ability to form dense TiO2 films. We believe the results described herein are important for further expanding the use of reactive and unreactive polymers for fields including area selective deposition, solar cell absorber layers and antimicrobial surface coatings.

The turn of the 21st century heralded in the semiconductor age alongside the Anthropocene epoch, characterised by the ever-increasing human impact on the environment. The ecological consequences of semiconductor chip manufacturing are the most predominant within the electronics industry. This is due to current reliance upon large amounts of solvents, acids and gases that have numerous toxicological impacts. Management and assessment of hazardous chemicals is complicated by trade secrets and continual rapid change in the electronic manufacturing process. Of the many subprocesses involved in chip manufacturing, lithographic processes are of particular concern. Current developments in bottom-up lithography, such as directed self-assembly (DSA) of block copolymers (BCPs), are being considered as a next-generation technology for semiconductor chip production. These nanofabrication techniques present a novel opportunity for improving the sustainability of lithography by reducing the number of processing steps, energy and chemical waste products involved. At present, to the extent of our knowledge, there is no published life cycle assessment (LCA) evaluating the environmental impact of new bottom-up lithography versus conventional lithographic techniques. Quantification of this impact is central to verifying whether these new nanofabrication routes can replace conventional deposition techniques in industry as a more environmentally friendly option.