In the field of area-selective deposition (ASD), most groups focus on using self-assembled monolayers (SAMs) to inhibit the growth on specific areas of the surface. We pioneered the approach of using small molecule inhibitors (SMIs), motivated by the compatibility of vapor-phase dosing of SMIs with industrial process flows. Since the writing of the proposal, more research groups started to explore using SMIs for ASD, demonstrating the feasibility of our approach.
In this project we identified the main challenge for using SMIs: as a consequence of vapor-phase dosing, SMIs arrive one-by-one on the surface and adsorb at random surface sites, resulting in a relatively low surface density in saturation. To investigate this adsorption mechanism, we developed a novel simulation approach, referred to as random sequential adsorption (RSA) simulations, which gives insight into the effect of molecular size and shape on the packing of SMIs on a surface.
From an experimental point-of-view, detailed in-situ Fourier transform infrared spectroscopy (FTIR) studies were performed to assess the importance of dosing conditions for the selectivity of area-selective deposition. In previous studies, we learned that SMIs adsorb on a surface in mixture of bonding configurations, that have different stability and do not necessarily all block deposition effectively. The infrared spectroscopy results suggest that a higher coverage of the desired configuration can be obtained by choosing appropriate conditions.
The extension of the toolbox with plasma exposures allows for the development of new and innovative approaches to area-selective deposition. By combining ALD and sputter etching by ions in a process, so-called sputter yield amplification by heavy elements can exploited to achieve area-selective deposition. It was demonstrated that SiO2 can be deposited selectively on Al2O3, with respect to the heavier HfO2. This approach can be described as a physical pathway towards selectivity, in contrast to the chemical pathways that are conventionally explored.
