Characterisation of ALD Layers

The ongoing miniaturisation of integrated circuits has in recent years led to the replacement of traditional deposition methods 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. 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.


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