Paper TF-TuA10
Multi-Scale Simulation of High-κ Gate Dielectrics Deposited by Atomic Layer Deposition

Tuesday, October 16, 2007, 4:40 pm, Room 613/614

Two of the most critical issues currently facing the semiconductor industry are the discovery of high-κ gate dielectric replacement materials for SiO₂ and the development of deposition processes that will afford high surface uniformity and controlled growth at the atomic scale. Atomic layer deposition (ALD) is an ideal candidate for meeting these challenges, enabling the deposition of a material through highly uniform and conformal growth, with thickness control at the atomic layer level. Our current work involves the use of a multi-scale modeling strategy to gain theoretical insights into the structure, properties and deposition process of high-κ dielectrics materials, which can provide a better understanding of experimental results and accurate predictions of specific properties of the thin films deposited by atomic layer deposition (ALD). In this work, we present results obtained from ab-initio quantum mechanical cluster calculations and periodic density functional theory (DFT) calculations based on tight-binding techniques. A series of calculations were carried out to study the initial ALD surface reactions. We present detailed chemical mechanisms and kinetic data at typical ALD temperatures range from 150°C to 450°C. This information can be used to understand experimental results and optimize operating conditions. The effects of surface functionalities and precursors on the thin film deposition process are discussed. Our DFT calculations show the complexity of the growth mechanisms during ALD processing. In addition, we predicted a new oxygen incorporation mechanism, which is relevant to the formation of the SiO₂ interfacial oxide layer during the ALD of Al₂O₃. As a replacement material for SiO₂, the potential high-κ oxide should form a high-quality interface with Si. We used molecular dynamics (MD) simulation to study the TiO₂/Si interface. A variable-charge inter-atomic potential was developed to describe the TiO₂/Si interface where the coordination environment may change. The TiO₂/Si interface structure was investigated by using MD with simulated annealing technique. The post-annealing oxidization process of the Si substrate was simulated by introducing external O atoms into the system to create concentration gradient. The atomic-scale mechanisms that govern the oxidation process can provide fundamental insight into the formation of the SiO₂ interfacial oxide and a better understanding of the TiO₂/Si interface structure.