Paper TF-ThP16
Low Temperature Plasma-assisted Atomic Layer Deposition of Copper Studied using In Situ Reflection-Adsorption Infrared Spectroscopy

Thursday, October 31, 2013, 6:00 pm, Room Hall B

Cu interconnects in modern integrated circuits are fabricated using an electroplating process, which requires an ultrathin, conformal, and continuous Cu seed layer. The resulting interconnect performance depends significantly on the quality of this seed layer. Atomic layer deposition (ALD) is a thin film growth technique, which is widely used to deposit highly conformal, high-purity films with digital control over the thickness. This technique has been successfully implemented to deposit a variety of metals. To enable new deposition chemistries, and to achieve better control over existing ones, it is important to understand the surface reaction processes that occur during film growth. In situ infrared spectroscopy has been shown to be an excellent technique to study surface reactions in an ALD processing environment. However, due to free electron absorption in metals, traditional infrared techniques based on transmission and internal reflection cannot be used to study metal ALD processes beyond the very initial nucleation stage. In this study, we have designed and implemented an in situ reflection-absorption infrared spectroscopy (RAIRS) setup to study the surface reactions during the deposition of Cu from Cu(hfac)₂ and a remote H₂ plasma at a substrate temperature of 80 °C. We specifically report on the surface reactive sites, and the mechanism for Cu(hfac)₂ chemisorption on an oxide (Al₂O₃) surface. Unlike previous studies, we propose a detailed surface reaction mechanism, which does not require the presence of hydroxyl groups on the oxide surface. Lastly, using RAIRS, we also report results with the use of reducing agents other than atomic H, and report on their efficacy.