Wet Cleanings

Wet wire-pipe ESPs are used much more frequently than dry wire-pipe ESPs, which are used only in cases in which wet cleaning is undesirable, such as high temperature streams or wastewater restrictions. Table 1 provides a list of typical applications. 

Sludge The waste product formed by a wet cleaning process. 

Washer, air A device for adding moisrure to an air stream by means of spray or capillary action. This term should not be used to relate to any wet cleaning process of a gas or other air stream. 

More Cl and O were observed by adding 1% O2 in CI2 and the amounts of residues were removed by wet cleaning process. It is expected that the residues generated during etching on the gate stack can be removed by wet cleaning process such as dilute HF. 

Currently wet cleaning process is an essential step to remove particles and residues... 

Another type of sterile ophthalmic product is the contact lens solution (section 4.5) however, unlike the other types, this is not used for medication purposes but merely as wetting, cleaning and soaking solutions for contact lenses. 

Methods of dust removal depend mainly on the particle size of the dust and the temperature and moisture content of the gas. The methods used are broadly divided into dry methods and wet methods. The dry methods involve the use of gravity and baffle chambers, cyclones, filters, and electrostatic precipitators, while the wet methods involve the use of spray towers and venturi scrubbers. In principle, wet cleaning is preferred to dry cleaning because of the excessive wear associated with and the difficulty in handling the fine dusty material removed in the dry methods. The wet methods, however, must be followed by such operations as filtration, drying of filter cakes, and recycling of water. 

Lack of a wet cleaning label for garments To date, there has been no care label for wet cleaning. In 2002, the International Committee of Textile Care (CINET) proposed such a new label (a bold W in a circle), which will be voted on in 2005. 

However, the majority of dry cleaners continue to use perchloroethylene because there is little awareness and no legislative imperative to choose safer substitutes." With both wet cleaning and CO now available in Europe and commercially competitive, there can be no Justification for the continued use of PERC to clean clothes. 

Liquid and solid interface (water drop resting on a solid, wetting, cleaning of surfaces, adhesion). 

The old scrubber technique is in fact very attractive for post-CMP cleaning as the same mechanical effect is active for all the materials present at the surface (insulators, metal barriers). Doubled-sided scrubbers for cleaning the frontside and the backside of the wafer and lateral brushes to take care of the wafer side are now proposed on the market. Furthermore, the implementation of megasonic sprays in the scrubber can sometimes help for difficult cases. The major limitation is in terms of cost of ownership (COO) as a single-wafer process is involved. Indeed according to Witt et al. [17] who used the standard SEMATECH COO model, brush cleaning is more than three times more expensive than wet cleaning, which was confirmed by other economic studies [18]. 

In conventional wet benches or spray tools, the wafers are processed in batches of 25 or more, which leads to lower COO. This is the main advantage of wet cleanings. As demonstrated earlier [18], the slurries from the market unfortunately contain foreign particles as well. Therefore wet processes must be able to remove both positive and negative particle types to reach a low final level. 

The existing cleaning methods can be divided into wet and dry cleaning. The wet cleaning process uses a combination of solvents, acids, surfactants and deionized (DI) water to spray and dissolve contaminants from the surface area. The Dl water is used to rinse after each chemical use. The oxidation of the wafer surface is sometimes integrated into the cleaning... 

The RCA cleaning was developed at a time where the semiconductor industry was much smaller and the environmental restrictions were not as strict as today. Since then the goal in the development of new processes was to reduce the number of necessary cleaning steps, chemical consumption and waste disposal. Recent improvements in wet cleaning have been very successful in further reducing costs, chemical and water usage. Many advances are based on the use of ozonated ultra pure water (UPW) as a replacement for hydrogen peroxide or even sulfuric based mixtures (Heyns et al., 1999). 

Cells may become contaminated as a result of evaporation of solvent from solutions, and also by acquiring a film of grease as a result of careless handling. Such films and dust particles decrease transmission and can also contaminate liquids placed subsequently in the cell. Immediately after use therefore cells must be emptied and rinsed with clean solvent and then cleaned with a suitable detergent solution and stored in distilled water. A brush which might scratch the optical surface should never be used. Solid contaminants must always be removed by the following wet cleaning procedure ... 

The shrinkage of ordinary acetate fabrics, such as suit linings, is not a problem in the Micare system. Since susceptibility to shrinkage (and dye loss) increases with the degree of acetylation of the acetate fiber, the exposure of triacetate fabric to C02 should be avoided when possible. Triacetates, which are rarely encountered, can be successfully wet-cleaned. Most other acetates can be successfully processed in the Micare system, including acetate suit lining. 

Use HEP A vacuum system before wet cleaning. Vacuum system should be dedicated for operating area... 

Any contaminated equipment should be cleaned using wet cleaning methods, such as a wet cloth prior to removal from the weigh hood. 

Note About Cleaning Methods. A number of cleaning techniques can be used. For example, a balance brush could be used to sweep residual powder off the balance and onto a filter paper. However, this method is not ideal because the powder tends to be distributed over the base of the unit. Wet cleaning methods tend to be more... 

Most common adhesive liquids readily wet clean metal surfaces, ceramic surfaces, and many high-energy polymeric surfaces. However, epoxy adhesives do not wet low-energy surfaces such as polyethylene and fluorocarbons. The fact that good wetting requires the adhesive to have a lower surface tension than the substrate explains why organic adhesives, such as epoxies, have excellent adhesion to metals, but offer weak adhesion on many untreated polymeric substrates, such as polyethylene, polypropylene, and the fluorocarbons. 

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