Achieving ultra low k dielectric constant for nanoelectronics interconnect systems
Air gaps are a promising alternative to porous low-k dielectrics to achieve ultra low k-values in Cu damascene interconnects. Two approaches of air gap formation using wet etch back of sacrificial PECVD SiO2 dielectrics were evaluated concerning their feasibility and preparation results are shown. Electrical measurements were verified by simulation and have shown a capacitance reduction of approximately 50 % compared to the SiO2 filled reference structures. Furthermore finite element method (FEM) simulations were performed to extract the effective k-value for different technology nodes. General k eff extraction procedure by FEM simulation is described. Furthermore the impact of variation of thickness and k-value of the functional layers applied for air gap formation was investigated. These functional layers are etch stop, cap and mask layers and currently consist of PECVD SiC:H films. It has been shown, that both parameters (thickness and k-value) considerably contribute to the effective k-value. For both investigated technology nodes, the 65 nm and 45 nm node, parameters can be found to fulfil the ITRS requirements for keff. Lower k-values of the functional layers are needed, if the thickness has to be increased for processing reasons. For example k=5.5 and thickness of 15 nm yield a keff of about 2.5 for the 45 nm node. Ultimate effective k-values of 2.0 and below could be achieved for lower k-value or thickness of the functional films
Film Characterization of Cu diffusion barrier dielectrics for 90 nm and 65 nm technology node Cu interconnects
This paper describes film characterization of Cu diffusion barrier SiC, SiCN and SiCO in detail. Although SiCN and SiCO achieve reduced leakage current and k-value, the biggest challenge is to achieve robust stability in film stress and k value because undesirable N and O doping cause increased film stress and k value after deposition. Fine-tuned SiC makes it possible to greatly reduce leakage current and k value to 3.9. From Bias Temperature Stress (BTS) measurement, our desired SiCN, SiCO and fine-tuned SiC are assured in 10-year durability to electrical Cu diffusion.
Die wisselwerking tussen ekonomiese en konstitusionele hervormings in Suid‐Afrika
Abstract This article deals with the interplay between economic and constitutional reforms in South Africa. Historical and contemporary forces which obtain in these spheres are taken into consideration after which a number of conclusions are drawn.