Electrochimica Acta 50 (2005) 4566–4575 Materials computation towards technological impact: The multiscale approach to thin films deposition Carlo Cavallotti ∗ , Marco Di Stanislao, Davide Moscatelli, Alessandro Veneroni Department Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, Via Mancinelli 7, 20131 Milano, Italy Received 4 February 2004; received in revised form 17 September 2004; accepted 15 October 2004 Available online 14 June 2005 Abstract Thin film deposition is a process complicated by chemical and physical phenomena that take place on different time and length scales. Its correct description requires the development of multiscale models. Here we present the multiscale approach we developed to study the epitaxial chemical vapour deposition (CVD) and etching processes. The model is designed to describe the atomic scale with quantum chemistry, the morphology evolution at the mesoscale with a Kinetic Monte Carlo (KMC) model utilizing parameters either taken from the literature or computed with the atomic scale model, and the fluid dynamic and local composition in the reactor through the solution of mass, energy and momentum conservation equations with the finite element method. The multiscale approach was used to investigate the gas-phase chemistry active during the MOCVD of II–VI semiconductors, the morphology evolution during the epitaxial deposition of Si, and the fluid dynamic and gas-phase composition in a plasma-etching reactor. © 2005 Elsevier Ltd. All rights reserved. Keywords: Multiscale modelling; Chemical vapour deposition; Quantum chemistry; 3D Kinetic Monte Carlo; Computational fluid dynamics 1. Introduction Computational material science of thin solid films has undergone great advancements in the last years. Significant progress has been made not only in the prediction and descrip- tion of the surface and bulk properties of the materials, but also, from an engineering point of view, in the comprehen- sion of the influence that the operating conditions of the growth process have on the desired material properties. In this framework particular attention was given to research projects composed of an experimental and a theoretical part, mutu- ally interacting so that models are validated on the results of experiments and used to propose new experiments or, in some cases, the synthesis of new materials or new deposition pro- cesses [1,2]. A sector in which the computational approach has had a high impact is the design of reactors for the deposi- tion of thin solid films with optimal geometries and operating conditions. ∗ Corresponding author. Tel.: +39 02 23993176; fax: +39 02 23993180. E-mail address: carlo.cavallotti@polimi.it (C. Cavallotti). An approach that has recently proved successful in the description of the thin film deposition processes is the multi- scale modelling approach. It is based on the fact that growth of materials with well-controlled morphological and compo- sitional properties is a process complicated by chemical and physical phenomena that occurs on time and length scales that can differ even by several orders of magnitude. In par- ticular there is a direct relation between key features of the material and the corresponding characteristic length scale. Thus, film growth rate and local composition are usually determined by geometry, fluid dynamics and thermal field of the growth reactor (or electrochemical cell), which are defined at a length scale between 10 -3 and 1 m, which we will refer to in the following as the reactor scale. Suitable models to describe these processes are continuum models based on the solution of partial differential equations, such as mass, energy and conservation equations, usually by means of finite elements, finite volumes or finite differences methods [3]. A length scale which has been receiving much atten- tion, mainly because of its importance for the electronic industry, is that of the device, be it a MOSFET, a laser, a 0013-4686/$ – see front matter © 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2004.10.092