Multi-objective optimization for inherently selective atomic layer deposition of zirconia on silicon and not on copper

Abstract

Atomic layer deposition (ALD) deposits uniform, pinhole free metal or metal oxide films via a self-limiting surface reaction. Area-selective ALD allows selective deposition of these films on targeted areas. Other than using masking to prevent deposition on undesired areas of the substrate, the process parameters can be altered to achieve selectivity. However, determination of whether an ALD process is selective under the chosen reaction conditions requires rigorous experiments to be performed. ALD is a slow process and requires expensive organometallic complexes known as metal precursors. Simulation models built on the experimental data can eliminate the need for performing multiple experiments by predicting reaction conditions that promote selective growth thus saving time and cost. A little or no information was found in literature on models that can predict selectivity window of an ALD process by looking at process parameters. Our inhouse experimental data obtained from the inherently selective atomic layer deposition (ISALD) of zirconia on silicon and not on copper were used to build a simulation model that predicts selectivity of the ISALD process over a wide range of temperature. Multi-objective optimization algorithm was developed to find optimal process condition that can maximize the deposition rate on silicon while minimizing the same on copper. The theoretical framework is based on the equilibrium reached at the substrate surface after chemisorption of the precursor molecules. The chemisorption process is influenced by the interactions of the groups present in the precursor molecules and on the substrate surface. Universal Quasi-chemical Functional-group Activity Coefficient method for group contribution was used to quantify the interactions between different groups. Further, we show that the same group interaction parameters can be used with a different zirconium precursor having same functional groups to predict growth characteristics of zirconia on silicon under similar reaction conditions.