Cluster devices/interconnects for nanotechnology
Thesis DisciplineElectrical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Integrated circuit (IC) technology has evolved rapidly but the continual development of transistors and interconnects (the connection between the transistors) is facing greater and greater challenges, which require new materials and new processes. Research in nano-particles (or nanoscale clusters) creates possibilities for both new materials and new processes. This thesis explores the electrical properties of amorphous antimony clusters and develops a new copper cluster deposition technique for application to transistors and interconnects respectively. For amorphous antimony clusters, an electron diffraction technique was applied to identify the phase of the clusters prior to deposition on electrically contacted samples. The deposition process produced uniform cluster films suitable for electrical measurements. A consistent percolation exponent for conduction (t=1.85) was obtained. After deposition, the resistance of the films continued to increase because of coalescence. Although it was previously reported that amorphous antimony films were semiconducting, from linear I(V) curves, a low temperature coefficient of resistance (10⁻⁴ K⁻¹) and no observable gate effect, it was found that the antimony cluster films in this study were not semiconducting, possibly due to the effect of coalescence. The development of the copper clusters for the interconnects application was very successful. Trenches of sub-200 nm widths, with different diffusion barriers and seed layers, and up to 5:1 aspect ratios have been completely filled with copper clusters. Due to the propensity for reflection of clusters from the planar surfaces between trenches, the process results in selective deposition into the trenches and bottom up filling is demonstrated. After annealing in hydrogen or in vacuum, the clusters sinter into a copper seed layer. The resistivity measured by a thin film four-point probe (1.6 - 2.3 × 10⁻⁸ Ωm) meets the requirement by industry (2.2 × 10⁻⁸ Ωm). The process is therefore promising for industrial application, but further testing and investigation of integration issues is required.