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Home > Nanotechnology Columns > UAlbany College of Nanoscale Science and Engineering > Materials Characterization and Nanoscale Materials
April 6th, 2010
Nanoscale materials have opened a rich new world of possibilities for science and engineering. In a discussion of nanoscale materials it is useful to divide them into ultra-thin films, ultra thin wires, and nano scale dots. These nano films, wires and dots all exhibit new phenomena which is the origin of the richness. Research, development, and manufacture of nanoscale materials all require advances in materials characterization including microscopy and physical/electrical characterization. In order to perform these measurements, one must both improve the measurement and understand how to interpret the impact of nanoscale phenomena on the measurement. The goal of this article is to provide a brief discussion of some of the key methods used to characterize nanoscale materials. All of these methods work together to provide a complete picture of nanoscale materials and their properties.
X-Ray reflectivity (XRR), X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF) and X-Ray Photoelectron Spectroscopy (XPS) all provide important means of characterizing nanoscale materials. XRR measures film thickness and works well with metal films which are opaque to ellipsometry. XRR is often applied to transistor gate stack measurements and is especially helpful when the top layer in a stack is a metal film. XRD and high resolution XRD provide information about the crystal structure of thick and thin films and grazing incidence XRD can tell us if nanoscale films have begun to crystalize. After deposition, the high k film is typically amorphous. HR-XRD is essential when doing research and development of new materials such as silicon-germanium thin films. XRF measures the amount of an element present in films is frequently used during semiconductor manufacturing to control the composition of thin films. X-Ray Photoelectron Spectroscopy (XPS) has proved essential for understanding the chemical state of high k film stacks. Depth profiles determined using angle dependent XPS provide a picture of the inter-diffusion of film stack components. An XPS depth profiles is shown in Figure 1. Often the high k films contain nitrogen, and XPS is an excellent means of determining the nitrogen concentration.
Ion Beam Methods
Rutherford backscattering and other high energy ion beam methods measure key parameters of the gate film stack. Recently, CNSE added High Resolution Rutherford Backscattering which provides much better depth resolution. This method will greatly enhance CNSE's RBS capability. Another ion beam method, secondary ion mass spectrometry, proves both depth profiles and trace contamination analysis.
Multiple Methods = Better Film Characterization
Through use of multiple methods, CNSE is able to provide thorough characterization of film stacks and remove any ambiguities that one may find by using a single method. In the transition from Lab to Fab, the thorough film characterization applied during research is put into practice inside CNSE's cleanroom to further the R&D efforts of CNSE's partners. Research partnerships such as the one my group has with TEL offer a great opportunity for graduate students to see first hand how industry research and development is done. CNSE partners gain through direct access to leading edge research.