Zvonimir Gabric

Electrical Interconnects Made of Carbon Nanotubes

The unique properties of carbon nanotubes (CNTs) make them promising candidates for electrical conductors in microelectronic devices. The parallel integration of CNTs into processes that are compatible with the requirements of the microelectronic industry will be important for their future application in chip devices. We present lithography‐based processes to create vertical electrical interconnects made of CNTs. The approach involves catalyst and dielectric (insulator) deposition, lithography, standard etch processes, CVD growth of the CNTs, and the structured deposition of metallic top contacts. This paper will discuss the electrical properties of these CNT vertical interconnects and compare them with the requirements of the ITRS roadmap.

Template grown multiwall carbon nanotubes

A range of pure metal and metal compound catalysts have been investigated for chemical vapor deposition (CVD) growth of multi-walled carbon nanotubes on silicon oxide substrates under various conditions. Catalysts including iron, cobalt and nickel and their carbonyl, chloride, oxalate and acetylacetonate compounds deposited on SiO2 substrates were prepared and reduced in flowing hydrogen prior to nanotube growth from hydrogen and acetylene at temperatures ranging from 500 to 750 °C. The highest quality nanotubes were grown from elemental iron and iron compound catalysts at temperatures around 700 °C.

Controlled CVD‐growth of multiwalled CNTs

Many applications of carbon nanotubes (CNTs) require a material with defined properties, however most synthesis routes yield CNTs of varying purity, structure, diameter, and length. Chemical vapor deposition (CVD) allows a good control over the CNTs synthesis and leads to promising results, however the effect of many parameters remains unclear. In order to improve this situation a comprehensive study was carried out under highly controlled conditions. The used CVD reactor was capable to perform deposition processes with temperature deviations smaller than 1°K. The substrates were patterned Fe films with a thickness below 10 nm on silicon/siliconoxide. The effects of the conditioning of the catalyst prior to growth, growth temperature, and growth time were investigated. The synthesis in a hydrogen/acetylene atmosphere yielded pure multi‐walled CNTs with diameters between 10 – 20 nm. The length of the CNTs was accurately controlled by the growth time. The density of the CNTs can be varied by the preconditio...

Scaling of Metal Interconnects: Challenges to Functionality and Reliability

Copper‐based nano interconnects featuring CDs well beyond today’s chip generations and air gap structures were fabricated and subjected to electrical characterization and tests to get already today insight on functionality and reliability aspects of metallization schemes in future semiconductor products. Size effects observed already in today’s advanced products will definitely limit the resistivity in future interconnects. Copper diffusion barrier layers were scaled down to the 1nm regime of thicknesses without observable degradation effects regarding adhesion properties and functionality. Interconnect reliability was found to decrease with decreasing barrier thickness. Worst results regarding adhesion properties and interconnect reliability were obtained for vanishing barrier thickness which promotes unrestricted mass flow of copper along the interconnect line. Air gaps were developed and characterized as an alternative approach to porous ultra low‐k materials. They allowed the realization of effective ...