Bottom-up nanopatterning by selective Atomic Layer Deposition

Group: CoCooN

Promotors: Jolien Dendooven and Christophe Detavernier

Supervisors: Ji-Yu Feng and 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)

During the past five decades, the advances made in the electronics industry have had a huge impact on the development of modern civilization. These advances are largely driven by the downscaling (scaling) of integrated circuits (ICs), represented by Moore’s Law. However, huge challenges arise for future technology nodes below 10 nm. For example, the increasing resistance of  Cu interconnect will become a bottleneck for further downscaling. Therefore, new materials are investigated to replace Cu, for example Co and Ni (Figure 1a). Furthermore, IC-fabrication currently relies almost completely on top-down processing, where thin films are deposited first, and patterned afterwards using lithography. Continued downscaling will require the adoption of bottom-up fabrication schemes for the most demanding processing steps.

Atomic layer deposition (ALD) is a thin film deposition technology in which the growing film is alternately exposed to typically a chemical precursor and a gas (co-reactant), each reacting with the surface in a self-limited way. This results in the sequential deposition of mono or sub-monolayers of material and enables the deposition of thin films with precise thickness control and excellent conformality. As a result, ALD of oxide films is already being applied for some of the most demanding processing steps in IC-fabrication. As ALD is very sensitive to the surface chemistry, so-called area-selective deposition can be acquired for some ALD processes, enabling bottom-up processing. For instance, ALD of Ru using the RuO4-precursor in combination with H2 gas as the co-reactant, has recently been shown to preferentially grow on H-terminated Si, rather than SiO2 (Figure 1b). Continued research is necessary to enable the application of area-selective ALD in IC-fabrication.

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The Winter research group at Wayne State University recently reported two very promising Co and Ni ALD processes. However, the reaction mechanism for these processes is still largely unknown. Therefore, by using in situ Fourier transform infrared spectroscopy (FTIR), in situ quadrupole mass spectroscopy (QMS) and in vacuo X-ray photoelectron spectroscopy (XPS), the ALD reaction mechanism during steady growth will be investigated. This knowledge is crucial to develop possible strategies for area-selective ALD of Co and Ni, as a potential bottom-up fabrication method for interconnects. This way, the student will acquire experience with both thin film deposition and several characterization methods.