Inhibitor-Free Area-Selective Deposition via Combined Atomic Layer Deposition and Etching

Deposition-based patterning is becoming an important need to manufacture advanced electronic devices. Area-selective deposition (ASD) is used routinely for epitaxial transistor contacts, but reaction temperatures exceeding 700°C are needed.  For new applications, new ASD processes are needed that work at <400°C to avoid material degradation. Recently, we found that ASD could be achieved at <300°C by combining chemical etching with atomic layer deposition so that deposition and etching occur simultaneously in parallel. For a range of materials and process conditions, thermodynamic modeling confirms that deposition and etching are both energetically favorable. Akin to high temperature selective epitaxy, the resulting net deposition is inherently self-aligned with the pre-patterned starting surface because the etching reaction locally consumes the deposition reactant, thereby avoiding unwanted nuclei. Using simultaneous deposition and etching, we show area-selective deposition of tungsten on nanopatterned surfaces. Modeling and initial experimental results show that the concept extends to a range of other material systems, indicating that simultaneous deposition and etching provides opportunities for low temperature bottom-up self-aligned patterning for electronic and other nanoscale systems.