Atomic Layer Deposition of Ruthenium for applications in nano-electronics

Group: CoCooN

Promotors: Jolien Dendooven and Christophe Detavernier

Supervisors: Matthias Minjauw

For more information, call 09/264.43.42 or contact one of the persons above (contact details are appearing by clicking on the person's name)

In view of its specific physical properties, Ruthenium is an interesting material for nano-electronics. Because of its low resistivity (7 μΩ.cm), good thermal stability and good adhesion to Copper, Ruthenium is a candidate material for 'seed layers' in interconnect structures. The orange colored regions in Figure 1 are Cu wires or 'interconnects' that are used to electrically connect the transistors in an integrated circuit (represented near the bottom of the figure) with each other and with the outside world. The use of Ruthenium seed layers is envisioned for enabling metallization in the most narrow features (labeled ‘Metal 1’ and ‘Intermediate’ on Fig. 1) of future interconnect architectures.

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The goal of this thesis is to investigate Atomic Layer Deposition (ALD) of Ruthenium. ALD is a thin film deposition technique which enables conformal coating of complex nanostructured surfaces in a very controlled way, by carefully depositing the coating layer-by-layer with atomic scale precision. ALD is based on self-saturating reactions between precursor vapour and the heated substrate. The ALD process that will be investigated during this thesis has been developed at our lab, and uses the RuO4 precursor in combination with H2 gas or H2 plasma as reactant.

Although there is already a lot of experience in deposition of Ru at the UGent-COCOON group, there are still many unanswered fundamental questions concerning the reaction mechanism during growth. During this thesis, we aim to use in vacuo X-ray Photoelectron Spectroscopy (XPS), a technique that has been recently implemented in our lab (Fig. 2) to obtain direct info on this growth mechanism. XPS provides information on the chemical state of the surface. Since there is a direct vacuum coupling between the ALD reactor and the XPS setup, the sample is not exposed to air during transfer, ensuring that the chemical state of the surface is preserved and hence enabling a fundamental characterization of the growth surface.