Vacuum-based deposition

At present it is felt that in this context, a fundamentally important recent advance in the silicon-based semiconductor industry is the development of copper interconnects on chips. Tliis new technology replaces aluminum or aluminum alloy (e.g., Al-Cu) conductors produced via vacuum-based deposition techniques with copper conductors themselves produced through electroless and/or electrodeposition. Specifically, vacuum-based deposition techniques include physical vapor deposition (PVD) and chemical vapor deposition (CVD). 

Combustion Chemical Vapor Deposition (CCVD) allows deposition of thin films that confer special electronic, catalytic, or optical properties, corrosion and oxidation resistance. The CCVD process is a novel, open-atmosphere process that is environmentally friendly and does not require expensive reaction/vacuum chambers. Often coatings are of equal or better quality than those obtained by vacuum-based methods. Coating costs are significantly lower than for more traditional processes such as Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD). Equally important, this novel technology can be implemented in a production-line environment, thus enabling uninterrupted processing. To date over 70 different inorganic materials have been deposited onto a variety... 

Film Deposition by Sputtering and Vacuum-Based Techniques... 

Thin films of ceramic materials are important both scientifically and commercially. For example, the operation of semiconductor devices relies on thin dielectric layers. In this chapter we described some of the main techniques used to produce such films. The conunon feature of all techniques for growing thin films is that we require a vacuum chamber. Deposition may occur at atmospheric pressure (e.g., some versions of CVD), but prior to deposition the chamber was evacuated. The choice of technique is based on several factors, including the type of material being deposited, whether we need an epitactic layer, and often the cost. The substrate plays an important role in the growth of thin films and thus we need to know the properties of the substrate and how to prepare it. Some of the techniques we described, such as PECVD, are important not only for growing thin films but also for producing nanostructures such as nanowires and nanosprings. 

In ion-plating deposition, the substrate and the deposited film (as it forms) are subjected to bombardment by particles (ions, atoms, molecules) which alter the formation process and the properties of the coating.l ll l The process is also called ion-beam assisted deposition (IBAD). Two basic versions of the process, plasma-based ion plating and vacuum-based ion plating, are illustrated in Figs. 15.8 and 15.9. 

Vacuum-based displays ultimately were unable to fulfiU the growing needs of the computer industry for a lightweight, low-power portable display that was less than an inch thick. It took the sohd-state revolution in electronic materials to identify candidates that could truly fill the needs of such devices. An early effort in electroluminescence was translated into hght-generating matrix displays such as the one shown in Fig. 7.16. The matrix itself is an array of pixels, each of which is a capacitor structure built of thin films vacuum-deposited... 

As compared with CVD growth, solution-based deposition is preferred for the following reasons (1) the low-temperamre process allows for deposition on the substrate, (2) easy upscaling to large areas, (3) and decreased cost without vacuum. Therefore, the solution-based method is an important method for further consideration. 

Let us focus first on cake filtration and microfiltration for the case where the fluid is a liquid. In the configuration of Figure 6.3.21, the techrtique is called deadend filtration. The same configuration is routinely employed in lahoratories with a filter paper on, say, a Buchner funnel and a partial vacuum on the side of the permeate/filtrate a precipitate/ deposit builds up quickly on the filter paper as the slurry is filtered. As time passes, a particle based deposit continues to build up on the filter paper it is called a cake. This cake provides an additional resistance to the flow of the filtrate through the membrane/filter/cloth in deadend filtration. As time passes, deposition of the particles onto/in the cake continues. Therefore the resistance to the flow of the filtrate increases with time. If one wants to maintain a constant eflae of the filtrate flux, the applied pressure difference AP has to increase with time. Alternatively, for a constant applied pressure difference, the flux of the filtrate will decrease with time (Figure 6.3.22). 

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