Surface Initiated Polymer Thin Films for the Area Selective Deposition and Etching of Metal Oxides

Abstract

The area selective growth of polymers and their use as inhibiting layers for inorganic film depositions may provide a valuable self-aligned process for fabrication. Polynorbornene (PNB) thin films were grown from surface-bound initiators and show inhibitory properties against the atomic layer deposition (ALD) of ZnO and TiO2. Area selective control of the polymerization was achieved through the synthesis of initiators that incorporate surface-binding ligands, enabling their selective attachment to metal oxide features versus silicon dielectrics, which were then used to initiate surface polymerizations. The subsequent use of these films in an ALD process enabled the area selective deposition (ASD) of up to 39 nm of ZnO. In addition, polymer thickness was found to play a key role, where films that underwent longer polymerization times were more effective at inhibiting higher numbers of ALD cycles. Finally, while the ASD of a TiO2 film was not achieved despite blanket studies showing inhibition, the ALD deposition on polymer regions of a patterned film produced a different quality metal oxide and therefore altered its etch resistance. This property was exploited in the area selective etch of a metal feature. This demonstration of an area selective surface-grown polymer to enable ASD and selective etch has implications for the fabrication of both micro- and nanoscale features and surfaces.

Area-Selective Deposition: Fundamentals, Applications, and Future Outlook

“…In another approach, patterned polynorbornene thin films have been grown from surface-bound initiators, and the resulting polymers were found to successfully impede nucleation of ZnO and TiO 2 during subsequent ALD. 291 To achieve patterned growth, the initiators were designed to selectively bind onto patterned oxide layers. In contrast to o-CVD, this attachment strategy enables selective deposition of the polymer on the insulator rather than on a metal.…”

Nanopatterned Area-Selective Vapor Deposition of PEDOT on SiO2 vs Si-H: Improved Selectivity Using Chemical Vapor Deposition vs Molecular Layer Deposition

“…Low-temperature ASD can be achieved by chemical vapor deposition (CVD), atomic layer deposition (ALD), and molecular layer deposition (MLD), with most recent attention focused on area-selective ALD. − While studies of ASD metals and dielectrics are most common, ASD of polymers is also expected to play an important role in bottom-up synthesis as nucleation inhibitors, low-k layers, and air-gap materials. − Previous studies of polymer CVD include several examples of substrate-preferential growth. − Using a thermally-excited reaction initiator, conjugated poly­( p -phenylene vinylene) (PPV) and nonconjugated parylene N and parylene C were found to preferentially grow on hydroxylated silicon oxide (Si-OH) with minimal growth on iron and other transition metals. , Based on growth rates and surface topology, inhibition on the metal was ascribed to quenching of activated monomers by available surface charge, forming a thin passivation layer that impeded subsequent reaction. Similarly, area-selective CVD of poly­(azomethine) was achieved on Si-OH vs hydrogen-terminated silicon (Si-H), but details of the related mechanism and the extent of selectivity were not well identified …”

Multimaterial Self-Aligned Nanopatterning by Simultaneous Adjacent Thin Film Deposition and Etching

“…Self-aligned area-selective deposition (ASD) uses surface chemistry to promote deposition in predetermined growth regions and minimize growth in adjacent nongrowth regions. At <400 °C, ASD can proceed using chemical vapor deposition (CVD) ,− or atomic layer deposition (ALD). − In these methods, the vapor-phase reactants are generally selected to favor net deposition; i.e. , the Gibbs free energy change for deposition is negative, Δ G < 0. , However, the strong reaction energetics is problematic for ASD because it leads to creation of unwanted nucleation defects.…”