Clean chemistry

Sherringron, D. C. (1991). Polymer Supported Systems Towards Clean Chemistry Chemistry and Industry (7 January), 15-19. 

What can ADMET offer in terms of tailoring the properties of a given polymer The answer lies in the clean chemistry of metathesis. If a metathesis active a,co-diene can be synthesized, then a known polymer can be produced. Few other polymerization techniques are so versatile, yet so precise. In recent years, our group has focused attention toward modeling polymers and copolymers made from ethylene in particular, we have been examining the effect of precise placement of alkyl and polar branches sequentially along tire backbone of polyethylene. 

Ethylene oxide is an important intermediate for ethylene glycol (antifreeze) and for plastics, plasticizers, and many other products [R.A. van Santen and H.P.C.E. Kui-pers, Adv. Catal. 35 (1987) 265]. In Chapter 1 we explained that the replacement of the traditional manufacturing process - which generated 1.5 mole of byproducts per 1 mole of epoxide - by a catalytic route based on silver catalysts is a major success story with respect to clean chemistry (Fig. 9.16). 

Photochemical reactions have the principal advantage of clean chemistry , as they use light of defined energy [72, 74], Synthesis of vitamin D and photocleavage of protection groups, for example, are accepted organic synthesis routes. Nevertheless, no widespread use of photochemistry has been made so far as this technique... 

Filtration can reduce the particles adhered to the wafer, but only slightly. Filtration will, however, reduce scratch defects. Slurry particles can be more effectively cleaned if more elaborate post-CMP clean chemistry is used [8]. 

Even if oxidant species are not intentionally introduced in the cleaning chemistries the latter are all oxidant due to the omnipresence of dissolved oxygen. The only way to annul this effect is to introduce a reducing agent. From the same reference [2] the behavior of the metals used in IMD processes can be predicted ... 

We observe that the Fe metal contamination problem is related to the post-W CMP cleaning chemistry used. We have found that the effectiveness of the chemistry to remove Fe contamination is in the order of... 

El Dib G, Chakir C, Roth E, Brion J, Daumont D. J Phys Chem A 2006 110 7848-57. Sussingham R. Can Coal Be Clean Chemistry, Spring 2007. 

Leadbeater, N.E., Fast, Easy, Clean Chemistry by Using Water as a Solvent and Microwave Heating, Chemical Communications, 2881-2902 (2005). 

Centre for Clean Chemistry Department of Chemistry University of Wales Swansea Swansea SA2 8PP UK... 

J. Langan, S. Rogers, R. Ciotti, B. Felker, (Air Products and Chemicals, Inc.), Investigation of Alternative Chamber Clean Chemistries for PFC Emission Reduction in the Novellus Concept One Reactor, Proceedings of the Perfluorocompound (PFC) Technical Update (SEMICON West 97), San Francisco, CA, 1997, H-l. 

The post-W CMP cleaning with ammonia in the past has caused wafer surface defect issues. Is it possible for you to determine alternative cleaning chemistries for the post-W CMP process Explain why you think they will provide a more efficient process. 

The CMP consumable industry must develop the infrastructure to respond to the challenge of the 2 year consumables development cycle. Because each new CMP application is likely to bring with it new and unique challenges, slurry, pad, and cleaning chemistries will need to be tailored to best suit the need of the new application. The vendor who can reliably have consumables ready in time will win the business. But to be nimble enough to develop the consumable on the 2 year cycle, the industry must increase its fundamental understanding of how the... 

In summary it seems that in situ synthesis of long chain carbon molecules is presently the most convincing of the various formation mechanisms. In particular, spallation of organic grains s ms rather unlikely in the cold dark clouds such as TMC 1. We note, incidentally, that the dark clouds produce an absolutely clean chemistry , in the sense that many types of reactions which occur in terrestrial chemistry are excluded. Shocks, for example, appear not to be present if one can judge from the observed narrow line profiles. The gas is very quiescent and cold. On the other hand, ions such as HCO and (Guelin et al., 1977)... 

Some Cr and F Incorporated in Outer Oxide Residual From Certain Cleaning Chemistries... 

Wet cleaning of wafers during the semiconductor production process often requires uniform removal of a few nanometers of material. Ideally, a single cleaning chemistry can be found that etches all exposed features at a comparable rate. Etch rates near 1 nm/min are desired for batch process and near 10 nm/min for single-wafer processes. A mixture of 500 1 DHF (dilute HF) with dissolved oxygen controlled near parts-per-million (ppm) levels has been found to meet these requirements for post copper CMP (chemical-mechanical polishing) cleans with exposed SiOj and Cu metal. 

Etch experiments were carried out in a MERCURY MP centrifugal spray acid processor [7]. In the acid processor, four cassettes of 25 wafers are mounted on a turntable in a sealed chamber. Cleaning chemistries and rinse water are atomized onto the wafers fiom sprayposts mounted at the center of the chamber (near the axis of rotation of the turntable) and on the outer chamber wall. When the DHF etchant is atomized, the tiny drops of liquid have a very high surface-area-to-volume ratio. The dissolved Oj concentration in the DHF nearly equilibrates with the atomizing gas before striking the surface. The concentration of dissolved Oj in the DHF can be controlled by the volume fraction of O2 in the atomizing gas. 

To address all these factors, an improved copper cleaning chemistry has been developed by Hoppe, et al. Designed to replace an effective, but overly aggressive concentrated nitric acid etch, this peroxide-based method allows for more controlled cleaning of surfaces. 

Maturation of the petro-chemical industry, environmental pressures for "clean chemistry" and the explosive development of biotechnology have increased interest in the application of enzymatic processes to organic synthesis. Enzymatic processes play an increasing role in the generation of chiral pharmaceutical intermediates, water-soluble materials and biopolymers. One problem in the development of enzymatic reactions for organic synthesis is the prediction of the stereochemistry of reaction. Reliable models for prediction of stereochemistry are needed to broaden the application of enzymes to organic synthesis. 

As far as chemical variables are concerned, especially in case of trace determinations, all the steps of sample collection, treatment in the field and storage must be carefully considered in order to maintain sample integrity before analysis. In this respect the selection of appropriate equipment and non-contaminant materials, as well as the application of efficient cleaning procedures, are of paramount importance. For the most critical applications clean chemistry laboratories (equipped with Class 100 laminar flow cabins) must be available in the field or on board. 

Analyses can be carried out in clean chemistry laboratories both on site, in order to check sampling procedures immediately after collection and after a long storage period (27, 49, 56, 57). Successful results obtained from experiments performed on site confirmed that this technique is the only one which can be used in remote areas, allowing checks on samples/sampling procedures and measurements directly immediately in the field. 

---