High-throughput screening of co-adsorbates to promote area-selective ALD
Atomic layer deposition (ALD) is a technique in which a substrate is exposed to precursor gases, which undergo self-limiting and irreversible chemical reactions, allowing for creation of conformal thin films with particular stoichiometric composition. ALD has shown tremendous potential for microelectronics and has been incorporated into many essential applications. In area-selective ALD, one seeks to prevent irreversible growth in areas of the substrate where deposition is not desired. A novel idea to promote selective deposition is to introduce a co-adsorbate with the precursor, which competes for binding sites and prevents precursor adsorption on one substrate, while allowing deposition on the other substrate to proceed unrestrained. We designed and constructed a vacuum chamber incorporating a quartz crystal microbalance (QCM) to characterize behavior of potential co-adsorbates for competitive adsorption. The frequency of quartz wafers can be exploited to measure deposition and adsorption/desorption behavior on the crystal. QCM data can be viewed in real time, which allows us to rapidly assess the effectiveness of molecules as co-adsorbates under different conditions, including changes in temperature, pressure, and flow rates. Additionally, the dynamics and thickness changes of individual cycles can be analyzed, where ex situ analysis may provide the total film thickness only after a particular time or number of cycles. After completing assembly of the chamber, we studied the system flow dynamics and temperature profile. We investigated the effect of individual doses of reaction components on different substrates, and compared ALD cycling with and without a co-adsorbate.