Simulation Study of Copper Cluster Deposition
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Simulation Study of Copper Cluster Deposition Jin C. Kang, Jeong W. Kang , and Ho J. Hwang Semiconductor Process and Devices Laboratory, Department of Electronic Engineering, Chung-Ang University, 221 HukSuk-Dong, DongJak-Ku, Seoul 156-756, Korea ABSTRACT The ionized cluster beam deposition of Al and Cu clusters has been investigated with a classical molecular dynamics simulation and the Metropolis Monte Carlo simulation. The spreading of the cluster has been studied as functions of cluster size and initial cluster energy. When the local area reached local melting spot on the surface, around the impact point of an energetic cluster, during a few ps, intermixing was easily achieved and a good epitaxial film with optimum bulk density was formed. For uniform film growth using cluster impact, it is necessary to make the local area temperature higher than melting temperature on the surface around the impact point of an energetic cluster. INTRODUCTION The ionized cluster beam deposition (ICBD) has been regarded as a method for growing highquality films at low substrate temperatures [1-4]. Molecular dynamics (MD) simulations have been widely applied to the investigation of interactions between metal clusters and metal surfaces. Most authors for the ICBD of metals have studied the collision of a single cluster with an ideal surface [5-9]. This allows one to study the cluster-surface interaction, but is not sufficient to understand thin film morphology in detail. Müler[10] studied a two-dimensional MD simulation using the Lennard-Jones potential, which is not adequate for metals. Haberland, Insepov, and Moseler [11] investigated energetic cluster impact (ECI) grown film using Mo cluster containing around 1,000 atoms with three-dimensional MD simulation and the embedded atom method (EAM) potential. The important requirements to grow ideal epitexial films without defects via ICBD are that each impinging cluster on the substrate should dissociate and spread in a uniform layer on the substrate, and intermixing between cluster and surface should be achieved. In Si cluster deposition simulations, Lu, Xie, and Feng [12] found that higher surface diffusion and spreading of the deposited cluster, which were achieved with a moderate cluster velocity, are necessary for epitaxial film growth and the substrate temperature also played an important role. However, they did not give a clear and exact explanation for ‘a moderate cluster velocity’. Kelchner and DePristo [13] investigated low energy cluster deposition during surface diffusion-limited thin film growth using molecular dynamics simulation. Since the total cluster energy of their studies is not large enough to allow the cluster to flatten into a twodimensional structure, as has been for simulations using high temperature or energetic cluster deposition, their study did not deal with intermixing effect during film growth using energetic cluster impacts. Hou et al. [14] simulated the low-energy cluster beam deposition (LECBD) with nanometer size AuN cluster. Since they simulated the
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