Robert Tsu

Leakage and breakdown reliability issues associated with low-k dielectrics in a dual-damascene Cu process

Leakage and breakdown characteristics of low-k dielectrics are becoming increasingly important reliability issues for interconnects as they are scaled to 0.18 um and below. Several of the low-k dielectrics, integrated into a dual-damascene Cu process flow, are quite leaky and have difficulty in meeting a leakage spec of 1E-8 A/cm/sup 2/ at 25/spl deg/C. Time-dependent dielectric breakdown (TDDB) for some of the low-k candidate films is also an issue because of generally low breakdown strengths <2 MV/cm. Furthermore, Cu out-diffusion through poor barrier confinement can result in increased electronic leakage and premature TDDB. Also, moisture absorption by these low-k materials serves to: increase the dielectric constant, increase the leakage and reduce the breakdown strength. These findings can have important reliability implications for Cu/low-k and care must be exercised in dual-damascene integration schemes.

Correlations of Ba 1−x Sr x TiO 3 Materials and Dielectric Properties

Thin film barium strontium titanate, Ba 1−x Sr x TiO 3 (BST), has been deposited on Pt bottom electrodes using metal-organic decomposition (MOD). Optimization of BST electric properties, including capacitance density and leakage current, can be achieved by altering the chemical and microstructural attribute of the films. Dielectric properties of BST are strongly dependent on processing temperature, film thickness, composition, and microstructure, which are closely correlated with each other. Nucleation temperatures of BST range from 580°C – 650°C depending on film thicknesses. The chemical composition giving the highest dielectric constant is explained in terms of microstructure; capacitance increases with increasing grain size for the BST films in this study. Capacitance density of 50 fF/μ m 2 and leakage current density 2 at 1.6 V can be achieved by optimizing BST materials properties. In addition, leakage conduction through the Pt/BST/Pt capacitor is shown to consist of polarization current resulting from Debye relaxation and true leakage current attributed to Schottky electron emission.

Effects of interfacial roughness on the leakage properties of SrTiO3 thin film capacitors

Abstract Recent reports on the current-voltage (I-V) characteristics of SrTiO3 and (Ba,Sr)TiO3 thin film capacitors with Pt electrode suggest that their leakage properties are controlled by Schottky emission from cathode. However, their dynamic permittivities obtained from the Schottky plot are always much smaller than those expected from optical measurements. The most plausible approach to explain this disagreement is to incorporate the effect of electric field enhancement due to interfacial roughness into the Schottky emission model. Electric field at the interface, for the first order approximation, can be given by [(r+t)/r](V/t), where r, t and V respectively denote radius of curvature representing interfacial roughness, dielectric thickness and applied voltage. This model predicts that I-V characteristics are the functions of r and V for the ultimate case of r ≪ t. We have closely studied the I-V characteristics of sputter-deposited SrTiO3 films and have obtained the results which strongly support ou...