Low Energy Ion Scattering (LEIS): A unique tool for characterization of thin metallic films

The ongoing miniaturization of integrated circuits has in recent years led to an increasing replacement of traditional metal layer deposition methods like chemical or physical vapour deposition (CVD or PVD) by atomic layer deposition (ALD). ALD layers meet high standards with respect to layer closure and homogeneity and are used as diffusion barriers or dielectric layers.

Low Energy Ion Scattering (LEIS) has established itself as a technique for testing these thin layers. In LEIS, the sample surface is bombarded with noble gas ions of some keV energy. Due to scattering with top surface atoms a specific energy loss of the projectiles is observed that allows a quantitative determination of the elemental surface composition. Additionally, information on the layer thickness can be gained when projectiles undergo scatter processes in the subsurface. These unique properties make LEIS an ideal tool for the analysis of ALD processes. It can be used to determine the growth rate even for the first ALD cycle, to minimize the number of cycles for a pin hole-free layer closure and to evaluate the thickness variation within a deposited film.

Figure 1 shows LEIS data from WNxCy-layers that were produced after varying numbers of ALD cycles. The aim of this project in co-operation with ASM, a specialist in ALD, was to optimise the ALD process for the manufacturing of diffusion barriers that were as thin as possible, yet pin hole free. With the aid of LEIS, the element composition of the outermost atomic layer and the thickness of the ALD layer were determined quantitatively. The evaluation of the data resulted in the graph in figure 2. It shows that the WNxCy layer is closed after 50 ALD cycles. In addition the data make it possible to draw conclusions about the growth kinetics of the ALD layers.

Tascon GmbH was founded in 1997 as a testing laboratory specialising in Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Since then the company has not only developed into an internationally leading laboratory for this technology but also continues to contribute to its development. In our lab, you will find a world wide unique combination of state-of-the-art ToF-SIMS instruments and application knowledge. At the end of 2008 we have expanded our activities to the field of Low Energy Ion Scattering (LEIS). In Summer 2009 we added a profiler for the optical characterisation of surface topography (white light interferometry, confocal microscopy). And since January 2010 X-ray Photoelectron Spectroscopy (XPS) has broadened our instrument portfolio. That enables us to extensively characterise surfaces with variable information depth. If necessary, further surface- and nanoanalytical techniques are at your disposal, offered in co-operation with our partner laboratories.

Currently, a staff of 15 highly qualified employees - 10 being university graduates - takes care of our customers' analytical challenges. Given the variety of our customers` requests, a broad background in experience is important to us. Our staff consists of graduates in physics, chemistry, chemical engineering, biology, biochemistry and geology. They are continuously educating themselves in order to keep the knowledge in the company up to date. This does not only include the analytical techniques, but also production technologies and materials science.

tascon GmbH is an independent, privately owned and operated company.

Tascon GmbH
Heisenbergstr. 15
48149 Münster
Germany
Kontakt: Dr. Reinhard Kersting
EMail: reinhard.kersting(ad)tascon-gmbh.de

This release was published on openPR.