Influence of megasonic agitation on the electrodeposition of high aspect ratio blind vias

This paper presents preliminary studies in electroplating using megasonic agitation to avoid the formation of voids within high aspect ratio microvias that are used for the redistribution of interconnects in high density interconnection technology in printed circuit boards. Through this technique, uniform deposition of metal on the side walls of the vias is possible. High frequency acoustic streaming at megasonic frequencies enables the decrease of the Nernst diffusion layer down to the sub-micron range, allowing thereby conformal electrodeposition in deep grooves. This effect enables the normally convection free liquid near the surface to be agitated. Higher throughput and better control of the material properties of the deposits can be achieved for the manufacturing of embedded interconnections and metal-based MEMS. For optimal filling performance of the microvias, a full design of experiments (DOE) and a multi-physics numerical simulation have been conducted to analyse the influence of megasonic agitation on the plating quality of the microvias. Megasonic based deposition has been found to increase the deposition rate as well as improving the quality of the metal deposits.

The role of space charge formation in the generation of thermally stimulated current (TSC) spectroscopy data for a model amorphous drug system

Thermally stimulated current (TSC) spectroscopy is attracting increasing attention as a means of materials characterization, particularly in terms of measuring slow relaxation processes in solid samples. However, wider use of the technique within the pharmaceutical field has been inhibited by difficulties associated with the interpretation of TSC data, particularly in terms of deconvoluting dipolar relaxation processes from charge distribution phenomena. Here, we present evidence that space charge and electrode contact effects may play a significant role in the generation of peaks that have thus far proved difficult to interpret. We also introduce the use of a stabilization temperature in order to control the space charge magnitude. We have studied amorphous indometacin as a model drug compound and have varied the measurement parameters (stabilization and polarization temperatures), interpreting the changes in spectral composition in terms of charge redistribution processes. More specifically, we suggested that charge drift and diffusion processes, charge injection from the electrodes and high activation energy charge redistribution processes may all contribute to the appearance of shoulders and 'spurious' peaks. We present recommendations for eliminating or reducing these effects that may allow more confident interpretation of TSC data.