NSF-Europe: Distribution, Segregation & Dose-Loss of Dopants in Deca-Nanometer SOI Structures using Ab inito Interface Dopant Analysis by Transmission Electron Microscopy

North Carolina State University, Raleigh NC

Investigators

Abstract

This is a collaborative project between participating groups in Germany, Sweden, and the US. The project addresses fundamental materials science issues in silicon-on-insulator (SOI) structures of particular technological relevance to realization of advanced device performance. The approach involves determination of the distribution and segregation of dopants within deca-nanometer SOI structures utilizing theoretical and experimental tools to gain greater understanding of processes leading to dose-loss and segregation to both oxide interfaces in nanoscale-device structures. Experimental methods will include atomic resolution TEM-based Z-contrast and electron energy-loss spectroscopy. Modeling will consist of atomistic ab initio calculations and process modeling. The core issue of segregation studies is that the atomic structure of silicon/oxide interfaces remains elusive in spite of intensive research. The model dependence of segregation energy in ab initio materials simulations is commonly considered to be a disadvantage. It is planned to exploit this model dependence by combining it with analytical TEM to transform a disadvantage into a powerful characterization tool, called AIDA-TEM (Ab initio Interface Dopant Analysis by Transmission Electron Microscopy). Since the predicted segregation sites of many impurities and dopants are heavily dependent on the atomic structure model of the interface, segregation sites of a number of impurities will first be determined experimentally. Then, which atomic interface model is in agreement with these experimental findings will be determined. In this way, AIDA-TEM helps to determine interface structure, dopant segregation behavior, and (from the ab initio calculations) electronic properties, which can then be used to predict device characteristics. Process modeling, based on experiments and ab initio calculations, is expected to lead to an understanding of dopant redistribution and dose loss mechanisms. And knowledge of structure-property relationships, dependent on dopants and annealing conditions, will allow determination of more optimum device processing parameters. %%% The project addresses fundamental research issues associated with materials having technological relevance in nanoelectronics. An important feature of the project is the strong emphasis on education, with emphasis on integration of research and education, and an international collaboration providing both scientific and educational benefits. Staff and student exchanges will supplement electronic communications between the participating groups. Undergraduate and graduate students involved in the project will be exposed to international and world-class science and technology. Young scientists and students greatly benefit from these kinds of projects, to learn the basics of nanoscience and to become motivated to pursue new ideas of their own. This NSF project is co-funded by the Division of Materials Research (Electronic Materials and Ceramics Programs), and the International Office (Western Europe) as a Cooperative Activity in Materials Research between the NSF and Europe (NSF 02-135). The project is being carried out in collaboration with participating groups in Germany (Heiner Ryssel Professor at the Electrical and Electronic Engineering Department, University of Erlangen-Nurnberg, Germany and Director of the Fraunhofer Institute of Integrated Circuits, Erlangen, Germany), and Sweden (Mikael Ostling Professor, Head of Department, Department of Microelectronics and Information Technology, Laboratory of Solid State Devices, KTH, Royal Institute of Technology).