Electronic Transport Properties of Cu/MnO x /SiO 2 /p-Si MOS Devices
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1156-D04-11
Electronic Transport Properties of Cu/MnOx/SiO2/p-Si MOS Devices V. K. Dixit, K. Neishi and J. Koike
Department of Material Science, Tohoku University, Sendai 980-8579, Japan ABSTRACT An ultrathin barrier layer of MnOx was grown using metal organic chemical vapor deposition (MOCVD) at an interface between Cu and SiO2 dielectric. The electronic transport properties of Cu/MnOx/SiO2/p-Si metal oxide semiconductor (MOS) devices showed leakage current density within the range of 10-8-10-7A/cm2 up to an electric field of 4MV/cm. The current density remained within the same range after bias temperature aging test at 3MV/cm for 6x103s at 550K. The capacitance-voltage curves of the MOS device having the MnOx layer grown at 473K do not show significant shift of flat band voltage after thermal annealing at 673K for 3.6x103s as well as after bias temperature aging test at 1MV/cm, 550K for 2.4x103 s. These results indicate that the ultrathin layer of MnOx is stable under the above conditions and prevents sufficiently Cu ion diffusion into the SiO2 dielectric. INTRODUCTION As the technology node of silicon semiconductors is advanced to a nanometer range, resistance capacitance (RC) delay becomes a serious issue [1-2]. In order to maintain line resistance as low as possible, Cu has been used as the interconnect metal. Since interdiffusion occurs easily between Cu and SiO2 dielectric insulating layer, a diffusion barrier layer is necessary at the interface. However, the barrier layer is not only a high resistivity material but also takes up the portion of the Cu line volume, leading to the increase of effective line resistivity. Thus, the barrier layer should be as thin as possible. Conventional material for the diffusion barrier is a bilayer structure of Ta/TaN formed by sputter deposition. Because of the straight trajectory of energetic sputtered atoms, the barrier layer becomes thinner on the side-wall surface of line trenches and connecting via holes than on other surfaces facing directly towards the sputter cathodes. This thickness non-uniformity of the conventional barrier has been a bottle neck for further thickness reduction. Recently, we developed chemical vapor deposition (CVD) process to form a conformal layer of a thin Mn oxide having a thickness of ~2 nm [3]. The diffusion barrier property was confirmed by an x-ray energy dispersive spectrometer (EDS) attached to a transmission electron microscope. However, the EDS analysis is not capable of detecting the small amount of secondary elements of less than 0.1 at.%. Since electric properties of semiconductors are sensitive to the ppm level of impurities, the detection accuracy of EDS is not sufficient to ensure the diffusion barrier property for interconnect application. In the present work, we investigated the barrier property of the MnOx ultrathin layer at Cu/SiO2 interface through current-voltage (IV) and capacitance-voltage (C-V) measurement. The charge migration into Cu/MnO/SiO2/pSi/Al MOS devices and its effects on the electrical behavior are also addre
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