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.
Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures
Electrical properties of thin dielectric films at the solid-liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co-polymeric hydrogels of polyacrylic acid co-sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co-planar geometry. Silane-modified glasses were characterized by the co-planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger. The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint-test cell versus this co-planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (Rs) was a spectral feature seen only by the co-planar hydrogel cell. Thus, it can be concluded that the use of such co-planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.