Extending the compositional diversity of films in area selective atomic layer deposition through chemical functionalities

Abstract

As the semiconductor community continues scaling, area selective atomic layer deposition (ASD) offers the potential to relax down stream processing steps by enabling self-aligned processes (e.g., self-aligned vias). Otherwise, conventional means of lithography face increasingly difficult challenges such as patterning and overlay errors as resolution improves. ASD can be achieved under a variety of conditions, and with the use of organic inhibiting materials, it can exhibit some of the highest levels of selectivity. However, the structure property relationship of these inhibiting materials is not completely understood, and therefore the relationship between a materials chemical functionality and its inhibiting properties remains largely unexplored. This was explored with polymeric materials that served as a versatile materials platform allowing a broad variation of chemical functional groups and physical properties that may then enable the ASD community to extend the number and types of films that can be selectively deposited. Initially, hydrophobic polymers including polystyrene (PS) and polyvinyl chloride (PVC), as well as an oleophobic polymer, poly[difluoro-bis(trifluoromethyo)-dioxole-co-tetrafluoroethylene] (PTFE-AF), were surveyed for their inhibitory properties toward the atomic layer deposition of industry relevant metal oxides such as Al 2 O 3 and TiO 2 , which heavily feature as etch masks and other functional nanostructures. Despite blanket deposition of Al 2 O 3 being observed, even when using an oleophobic polymer such as PTFE-AF, TiO 2 deposition was notably inhibited by blanket films of PVC, PS, and PTFE-AF. In light of these results, the functionalization of PVC and PS with selective area substrate anchoring groups such as phosphonic acids (targeting copper oxide surfaces) was conducted to investigate whether grafting selectivity of these polymer films to their intended surface could be inhibited, thereby achieving film growth in the proximal uninhibited area. Two methods of polymer functionalization were evaluated: phosphonic acid groups distributed randomly throughout the polymer backbone of PVC and a single phosphonic acid group localized at the chain end of PS. Notably, the PVC multidentate derivatives and the PS monodentate type polymers exhibited effective inhibition of TiO 2 .