Search

The copper interconnect technology is constrained by the non-uniformity of the current distribution over the wafer due to the terminal effect for resistive thin seeds. As a result, the current in the wafer center becomes insufficient to cathodically protect the copper seed leading to seed corrosion in this wafer area. To improve the current distribution, the exchange current density can be lowered e.g. by lowering the Cu2+ concentration. Our approach is to investigate and develop acid ultra-low copper baths with feature fill capability. For this goal, the optimum additives concentrations were sought and fill studies in 30 nm wide trenches were performed. Additionally, a low-copper/high-acid chemistry, that is also compatible with direct plating, was developed to enable the in-situ copper seed formation and filling in one process step for plating on non-copper seeds. [ABSTRACT FROM AUTHOR]

Cupric ions are a major component in electrolyte baths for Damascene copper plating. To unravel the mechanism of this plating process, knowing the cupric ion activity (aCu2+) is essential. However, determining aCu2+ in such solutions is not straightforward. Calculating the activity often requires complicated models to account for the complex composition and high concentration of the electrolytes. Also experimentally obtained data for these particular solutions are hardly available. In this work, the cupric ion activity in the presence of sulfuric acid is determined by measurements of the open-circuit Cu electrode potential in these solutions. A saturated mercury/mercurous sulfate electrode (SMSE) is used as the reference electrode. Because the potential of this electrode appeared to depend on the solution composition, a silver/silver chloride electrode was used for calibration of the SMSE and for determination of the precise copper electrode potential vs. the standard hydrogen electrode. Consequently, it was possible to calculate aCu2+ in highly concentrated multi-component solutions. [ABSTRACT FROM AUTHOR]

Defect etching is a fast and simple technique for the revelation of defects in single-crystalline materials. We propose here three different chemistries that allow accurate monitoring of the density of threading dislocations in germanium. This work especially focuses on solutions that have low etch rates and high selectivity in order to work on thin layers. Moreover, solutions that do not contain any carcinogenic CrVI nor HF acid are proposed in order to reduce the impact on environment and the risks for the user. A comparison of the etch rate and the selectivity toward defects is given as a function of the composition of the etching solutions (components and concentrations). A complete procedure for the proper determination of threading dislocation densities is also presented. [ABSTRACT FROM AUTHOR]