Ahmed Busnaina

Experimental and Numerical Investigation of Nanoparticle Removal Using Acoustic Streaming and the Effect of Time

The removal of nanoparticles is becoming increasingly challenging as the minimum linewidth continues to decrease in semicon-ductor manufacturing. In this paper, the removal of nanoparticles from flat substrates using acoustic streaming is investigated. Baresilicon wafers and masks with a 4 nm silicon cap layer are cleaned. The silicon-cap films are used in extreme ultraviolet masks toprotect Mo–Si reflective multilayers. The removal of 63 nm polystyrene latex PSL particles from these substrates is conductedusing single-wafer megasonic cleaning. The results show higher than 99% removal of PSL nanoparticles. The results also showthat dilute SC1 provides faster removal of particles, which is also verified by the analytical analysis. Particle removal from the4 nm Si-cap substrate is slightly more difficult as compared to bare silicon wafers. The experimental results show that the removalof nanoparticles takes a relatively long removal time. Numerical simulations showed that the long time is due to particleoscillatory motion and redeposition, and that this phenomenon is not observed in the removal of sub- m or larger size particles.© 2006 The Electrochemical Society. DOI: 10.1149/1.2217287 All rights reserved.Manuscript submitted January 9, 2006; revised manuscript received April 24, 2006. Available electronically July 19, 2006.

Large scale directed assembly of nanoparticles using nanotrench templates

The authors describe a general high throughput directed assembly technique to address some of the challenges to enable high rate∕high volume nanomanufacturing. The directed assembly of colloidal particles using an applied electric field shows the ability of precise control of nanoparticles by controlling assembly voltage, time, and geometric design of templates. The results show that single nanoparticle lines as small as 10nm wide and 100000nm long over a 2.25cm2 area as well as other nanoparticle structures can be fabricated using electrophoresis. This approach offers a simple, robust, and fast means of directed assembly of nanoelements for many applications.

Directed assembly of gold nanoparticle nanowires and networks for nanodevices

Alternating electric field is used to assemble gold nanoparticle nanowires from liquid suspensions. The effects of electrode geometry and the dielectrophoresis force on the chaining and branching of nanowire formation are investigated. The nanowire assembly processes are modeled using finite element calculations, and the particle trajectories under the combined influence of dielectrophoresis force and viscous drag are simulated. Nanoparticle nanowires with 10nm resolution are fabricated. The wires can be further oriented along an externally introduced flow. This work provides an approach towards rapid assembly and organization of ultrasmall nanoparticle networks.

Three-dimensional assembly of single-walled carbon nanotube interconnects using dielectrophoresis

We present a hybrid approach that combines top-down fabrication with bottom-up directed assembly for making single-walled carbon nanotube (SWNT) based three-dimensional interconnects. The SWNTs are assembled using dielectrophoresis at room temperature on a microfabricated 3D platform. The two-terminal resistance of the assembled SWNTs at 10xa0Vpp assembly voltage is approximately 545xa0Ω. Simulation of the dielectrophoretic assembly is carried out to understand the behavior of the SWNTs during assembly. Encapsulation of these devices using a conformal pinhole-free parylene layer resulted in a decrease of the total resistance.

Directed Assembly of Polymer Blends Using Nanopatterned Templates

The direct assembly of polymer blends on chemically functionalized surfaces is shown to produce a variety of nonuniform complex patterns. This method provides a powerful tool for easily producing nonuniform patterns in a rapid (30 s), one-step process with high specificity and selectivity for a variety of applications, such as nanolithography, polymeric optoelectronic devices, integrated circuits, and biosensors.

Experimental and Analytical Study of Submicrometer Particle Removal from Deep Trenches

Particle removal from patterned wafers and trenches presents a tremendous challenge in semiconductor manufacturing. In this paper, the removal of 0.3 and 0.8 μm polystyrene latex (PSL) particles from high-aspect-ratio 500 μm deep trenches is investigated. An experimental, analytical, and computational study of the removal of submicrometer particles at different depths inside the trench is presented. Red fluorescent polystyrene latex (PSL) particles were used to verify particle removal. The particles are counted using scanning fluorescent microscopy. A single-wafer megasonic tank is used for the particle removal. The results show that once a particle is removed from the walls or the bottom of a trench, the vortices and circulation zones keep the particles in the trench for a few minutes before eventually moving the particle out of the trench. The experimental results show that the time required for complete removal of particles from the bottom of the trench takes a much longer time than particles on the surface. This has been also verified and explained by physical modeling of the cleaning process. The removal efficiency and cleaning time are reported at different trench depths.

Scalable nanotemplate assisted directed assembly of single walled carbon nanotubes for nanoscale devices

The authors demonstrate precise alignment and controlled assembly of single wall nanotube (SWNT) bundles at a fast rate over large areas by combining electrophoresis and dip coating processes. SWNTs in solution are assembled on prepatterned features that are 80nm wide and separated by 200nm. The results show that the direction of substrate withdrawal significantly affects the orientation and alignment of the assembled SWNT bundles. I-V characterization is carried out to demonstrate electrical continuity of these assembled SWNT bundles.

Three dimensional controlled assembly of gold nanoparticles using a micromachined platform

By using optical lithographic procedures, the authors present a micromachined platform for large scale three dimensional (3D) assembly of gold nanoparticles with diameters of ∼50nm. The gold nanoparticles are formed into 3D low resistance bridges (two terminal resistance of ∼40Ω) interconnecting the two microelectrodes using ac dielectrophoresis. The thickness of the parylene interlevel dielectric can be adjusted to vary the height of the 3D platform for meeting different application requirements. This research represents a step towards realizing high density, three dimensional structures and devices for applications such as nanosensors, vertical integration of nanosystems, and characterization of nanomaterials.

Effect of Different Deposition Mediums on the Adhesion and Removal of Particles

The purpose of this study is to investigate the effect of the different deposition mediums on the adhesion and removal of particles. Polystyrene latex (PSL) particles (50 μm) are deposited on thermal oxide and silicon nitride coated silicon wafers using different suspension mediums: air, isopropyl alcohol (IPA), and deionized water and then removed in a dry environment. The results show that PSL particles deposited on oxide are easier to remove than those on nitride due to a higher van der Waals force in all deposition mediums. In addition, dry particles deposited in air are much easier to remove than those desposited in a liquid medium. When particles are deposited from a liquid suspension, a liquid meniscus is formed between the particle and the substrate, resulting in a capillary force. The capillary force induces a plastic deformation for soft particles such as PSL, which increases the contact area between the particle and the substrate, making them more difficult to remove. The liquid meniscus evaporates shortly after it is exposed to either a dry air environment or vacuum; however, the plastic deformation of particles would take place mainly due to the initial adhesion force in addition to the short time exposure of the capillary force.

A three dimensional Multi-Walled Carbon Nanotube based thermal sensor on a flexible Parylene substrate

We present the first design, fabrication and testing results from a three dimensional multi-walled carbon nanotube based thermal sensor fabricated on a flexible parylene-C substrate. Parylene-C is an inert, biocompatible, optically transparent, room temperature deposited polymer with a high mechanical strength, yet is rarely used as a flexible substrate. By utilizing a 2 mask process, we have manufactured a versatile microplatform for nanoscale assembly and then by utilizing dielectrophoretic assembly, incorporate MWNTs onto the platform in a 3D manner. The MWNTs are next encapsulated using a thin Parylene-C layer that acts as an environmental barrier and in addition keeps the MWNTs intact. The temperature Coefficient of Resistance of the MWNT sensor is measured to be between -0.21% and -0.66% per degree. The thermal sensor is compact, is very high density and could potentially be used for diverse temperature sensing applications such as in wearable textiles, on non planar surfaces and for in-vivo applications.