Rahimah Mohd Saman

Selective formation of tungsten nanowires

We report on a process for fabricating self-aligned tungsten (W) nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD) using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions.

Multiwalled Carbon Nanotube Growth Mechanism on Conductive and Non-Conductive Barriers

We report on the catalytic growth of multiwalled carbon nanotubes by plasma enhanced chemical vapor deposition using Ni and Co catalyst deposited on SiO2, Si3N 4,ITO and TiN Xbarrier layers; layers which are typically used as diffusive barriers of the catalyst material. Results revealed higher growth rates on conductive ITO and TiN Xas compared to non con-ductiveSiO2, and Si3N 4,barriers. Micrograph images reveal the growth mechanism for nanotubes grown on SiO2, Si3N 4 and ITO to be tip growth while base growth was observed for the TiN X barrier layer. Initial conclusion suggests that conductive diffusion barrier surfaces promotes growth rates however it is possible that multiwalled carbon nanotubes grown onSiO2, and Si3N 4,were encumbered as a result of the formation of silicide as shown in the results here.

Morphology and particle size analysis on Al/Ni binary catalyst for carbon nanotube growth through plasma enhanced chemical vapour deposition

Carbon nanotubes (CNT) has attracted much attention in recent years due to its unique properties and vast potential in nanotechnology. Over the years, extensive research has been conducted to develop a reliable synthesis methodology to produce CNT. Among many methods for CNT growth, transition metal based catalyst via plasma enhanced chemical vapour deposition (PECVD) is one of the widely adaptable methods for large scale CNT growth.

Self-aligned nanostructures by CMOS technology

In semiconductor fabrication, there are various methods that can be employed to form fine structures. Such techniques include a combination of advance lithography and etching, chemical mechanical planarization (CMP), or metal lift-off. However, these techniques may not be the easiest or the most cost effective. When using lithographic methods such as ultraviolet (UV), deep ultraviolet (DUV), extended ultraviolet (EUV), E-Beam [1], and X-ray, there are always resolution and alignment issues such as how small a structure can be produced and how closely and accurately a structure can be aligned to another. Even when lithography issues are resolved, patterning of very fine structures is also a problem. Wet chemical etching is not feasible when trying to produce submicrometer features because of large undercuts due to the isotropic nature of the etch solution. Lift-off with sacrificial resist [2] is a more common solution to produce nanostructures, but the technique does have resist imposed limitations where deposition must take place below 200°C because of resist thermal stability preventing its use with chemical vapour deposition processes. Also, organizing nanostructures into highly ordered array can also prove extremely challenging.

Capacitance Density Comparison of PECVD Silicon Oxynitride and Silicon Nitride Dielectric for MIM Capacitor

In this work, we compare capacitance density of MIM capacitors between PECVD Silicon Nitride (SiN) and PECVD Silicon Oxynitride (SiON). Process parameters for both dielectrics are different in term of gasses, refractive index, and dielectric constant, while thicknesses are similar. The capacitors are tested on two different test structures, which are stand alone and matching cells. The size of the cell is 90times90mum2. Our measurements show that SiN capacitors are superior to SiON capacitors in terms of higher capacitance density and lower matching variation