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.
The removal of nanoparticles is becoming increasingly challenging as the minimum linewidth continues to decrease in semiconductor manufacturing. In this paper, the removal of nanoparticles from flat substrates using acoustic streaming is investigated. Bare silicon wafers and masks with a 4 nm silicon cap layer are cleaned. The silicon-cap films are used in extreme ultraviolet masks to protect Mo-Si reflective multilayers. The removal of 63 nm polystyrene latex ͑PSL͒ particles from these substrates is conducted using single-wafer megasonic cleaning. The results show higher than 99% removal of PSL nanoparticles. The results also show that dilute SC1 provides faster removal of particles, which is also verified by the analytical analysis. Particle removal from the 4 nm Si-cap substrate is slightly more difficult as compared to bare silicon wafers. The experimental results show that the removal of nanoparticles takes a relatively long removal time. Numerical simulations showed that the long time is due to particle oscillatory motion and redeposition, and that this phenomenon is not observed in the removal of sub-m or larger size particles. Fabrication of micro-and nanoelectronics requires nanoscale particle and other contaminant removal from wafers and associated thin films. These undesired particles on the wafer surface influence the device yield and reliability. These particles could result from chemical vapor deposition, physical vapor deposition, etching processes, and many other fabrication processes. The FEOL ͑front end of the line͒ critical particle size is expected to decrease to 9 nm by the year 2018.1 The smaller the particles, the harder it is to overcome the adhesion force between the particle and the substrate. The adhesion force consists of the van der Waals and the electrostatic double-layer forces. High-frequency sonic energy in liquids ͑megasonic cleaning͒ has proven to be an effective method for particle removal. Although megasonic cleaning is widely used in the semiconductor industry, the fundamental physical processes are not thoroughly understood. Olaf 2 made early observations of sonic cleaning of glass surfaces in the range from 15 kHz to 2.5 MHz. McQueen 3 recognized the importance of acoustic streaming and the thin boundary layer thickness in small particles removal from surfaces. Busnaina and Kaskoush 4 found that increasing the frequency above 300 kHz could eliminate the surface damages on wafer surfaces during wafer cleanings. Gale and Busnaina 5 studied the mechanisms of particle removal in megasonic and ultrasonic cleaning, including the effects of frequency, temperature, and power density.Acoustic streaming is considered to be the key cleaning mechanism in the removal of sub-m particles.6-8 According to Olim, 9 theoretically it is not possible to remove particles below 100 nm using megasonic cleaning. But, in practice, particle sizes down to and less than 100 nm have been effectively removed using megasonics. The underestimation of Olim's model is because the viscous drag force and the ...
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 m polystyrene latex ͑PSL͒ particles from high-aspect-ratio 500 m 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 ͑PSL͒ 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. The current trend in semiconductor technology toward smaller device features has led to narrower linewidths in integrated circuits ͑ICs͒. During the IC fabrication process, trenches and vias have to be cleaned before the next processing step. Contamination during etching, deposition, and other processes is a major concern in IC fabrication because they are responsible for most of the yield losses in semiconductor manufacturing. Although the trench width used in this paper is large for semiconductor applications, it does present valuable information about imaging, counting, and removing nanoscale particles in deep trenches, provided that the particles are much smaller than the trench. The current trench geometry is important to cleaning Head Gimbal Assembly ͑HGA͒ at different manufacturing steps in hard disk manufacturing. Megasonic cleaning has been widely used in semiconductor fabrication and other industries for over 30 years and has been found effective in particle removal. Although megasonic cleaning has been used to clean patterned wafers with three-dimensional geometries, the mechanism of megasonic cleaning process for patterned wafer trenches and vias is not well-understood. Prior work that did not involve megasonic cleaning or acoustic streaming reported 1 that sinusoidally forced flow leads to an excellent mixing of the mainstream and the cavity fluid through the mechanism of the destruction and regeneration of the trapped vortex in the cavity ͑trench or vias͒. The enhancement of mass transfer in a deep cavity due to external steady channel flow was also investigated. 2,3 Lin et al. 4 showed that rinse flow normal to the wafer surface creates orders of magnitudes higher cleaning efficiency than the parallel flow for both steady flow rinse and oscillating flow rinse on wafer surfaces and inside trenches. Nilson and Griffiths 5 used ...
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Effective cooling of the airfoil leading-edge is imperative in gas turbine designs. Amongst several methods of cooling the leading edge, impingement cooling has been utilized in many modern designs. In this method, the cooling air enters the leading edge cavity from the adjacent cavity through a series of crossover holes on the partition wall between the two cavities. The crossover jets impinge on a smooth leading-edge wall and exit through the film holes, and, in some cases, form a crossflow in the leading-edge cavity and move toward the end of the cavity. It was the main objective of this investigation to measure the heat transfer coefficient on a smooth as well as rib-roughened leading-edge wall. Experimental data for impingement on a leading edge surface roughened with different conical bumps and radial ribs are reported by the same authors, previously. This investigation, however, deals with impingement on different horseshoe ribs and makes a comparison between the experimental and numerical results. Three geometries representing the leading-edge cooling cavity of a modern gas turbine airfoil with crossover jets impinging on 1) a smooth wall, 2) a wall roughened with horseshoe ribs, and 3) a wall roughened with notched-horseshoe ribs were investigated. The tests were run for a range of flow arrangements and jet Reynolds numbers. The major conclusions of this study were: a) Impingement on the smooth target surface produced the highest overall heat transfer coefficients followed by the notched-horseshoe and horseshoe geometries. b) There is, however, a heat transfer enhancement benefit in roughening the target surface. Amongst the three target surface geometries, the notched-horseshoe ribs produced the highest heat removal from the target surface which was attributed entirely to the area increase of the target surface. c) CFD could be considered as a viable tool for the prediction of impingement heat transfer coefficients on an airfoil leading-edge wall.
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