TiN/Al2O3 Interface Study through ALD Process Modulations

Abstract

Integration and miniaturization of highly reliable electronic devices are the basis of advanced technologies used for the manufacturing of implantable medical systems such as pacemakers or neuronal stimulators. Among these components, passive devices and more particularly capacitors have a key role in signal filtering and power energy management. In this context, the capacitance density improvement is a way to enable smaller components, thus increasing the final device miniaturization. Currently, Murata Integrated Passive Solutions is running in production a technology called “PICS™” enabling the 3D structuring of the silicon substrate that dramatically enhances its specific area (i.e. capacitance density) when combined with highly reliable low-k dielectric stacks such as silicon dioxide/nitride/dioxide (ONO). In order to significantly increase the capacitance density, two points are critical: first the 3D structures need to evolve toward a more aggressive template with a higher aspect ratio, so as to increase much more the dielectric specific area. The second point is the change of dielectric toward materials with higher dielectric constant such as Al2O3 or HfO2. Atomic Layer Deposition (ALD) technique is a key requirement here, as it is a method enabling conformal deposition of various materials, dielectrics or conductors, such as TiN, on high aspect ratio structures. In parallel of the integration and the optimization of such materials within 3D structures, planar ALD based Metal/Insulator(s)/Metal (MIM) capacitors need to be studied to serve as a reference point. The aim of our investigations is to link the electrical properties of MIM capacitors with the parameters applied during a batch ALD process such as temperature, pulse and purge times, with the support of physico-chemical characterizations (X-ray Photoelectron Spectrometry (XPS), Secondary Ion Mass Spectrometry (SIMS), Scanning Transmission Electron Microscopy (STEM)…). We will focus on the dielectric/electrode interfaces analysis through leakage current mechanism modeling and interpretations. Especially, the amount of O3 used in the Al2O3 deposition process has an important impact on the electrical properties of the MIM by impacting both TiN/Al2O3 interfaces in different ways. An optimization of the O3 dose is proposed.