Functional model for analysis of ALD nucleation and quantification of area-selective deposition

Abstract

Bottom-up chemical patterning, to additively form material only in desired locations, is becoming important to address scaling issues in semiconductor device manufacturing, catalytic material design, and other fields utilizing nanometer- and sub-nanometer-scaled material features. In some semiconductor device fabrication steps, chemically driven patterning by area-selective deposition (ASD) is beginning to supplant physical patterning by photolithography. To advance the field of ASD, more understanding is needed regarding mechanisms of thin film nucleation, particularly when nucleation proceeds where thin film deposition is not desired. To better understand thin film nucleation, this work describes a relatively simple analytical model with three adjustable input parameters that quantifies film growth initiation, island growth, and thickness evolution during area-selective atomic layer deposition (AS-ALD) and area-selective chemical vapor deposition. A definition is presented for chemical selectivity during film growth that depends on the extent of film coverage in the desired non-growth region. Fitting the model with experimental data gives quantitative output that allows the extent of selectivity to be compared for different ASD approaches studied in different labs, with data collected using a variety of analytical tools. Using several example published AS-ALD data sets, the article demonstrates how fitting the model to experimental data gives insight into different nucleation mechanisms for unwanted film growth during ASD. The author further describes how the model can be improved and expanded to encompass more complex film growth and nucleation mechanisms.