Principal steps

In this chapter we will focus on contact and via fill using the blanket tungsten approach. In chapter 5 we will discuss another application of blanket tungsten, namely, that of tungsten as the interconnect material. 

Three important steps must be considered after the contact openings have been etched  

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Step-growth polymerizations can be schematically represented by one of the individual reaction steps VA + B V —> Vab V with the realization that the species so connected can be any molecules containing A and B groups. Chain-growth polymerization, by contrast, requires at least three distinctly different kinds of reactions to describe the mechanism. These three types of reactions will be discussed in the following sections in considerable detail. For now our purpose is to introduce some vocabulary rather than develop any of these beyond mere definitions. The principal steps in the chain growth mechanism are the following ... 

There are numerous variations of the wet process, but all involve an initial step in which the ore is solubilized in sulfuric acid, or, in a few special instances, in some other acid. Because of this requirement for sulfuric acid, it is obvious that sulfur is a raw material of considerable importance to the fertilizer industry. The acid—rock reaction results in formation of phosphoric acid and the precipitation of calcium sulfate. The second principal step in the wet processes is filtration to separate the phosphoric acid from the precipitated calcium sulfate. Wet-process phosphoric acid (WPA) is much less pure than electric furnace acid, but for most fertilizer production the impurities, such as iron, aluminum, and magnesium, are not objectionable and actually contribute to improved physical condition of the finished fertilizer (35). Impurities also furnish some micronutrient fertilizer elements. 

The principal steps in the mechanism of polyisoprene formation in plants are known and should help to improve the natural production of hydrocarbons. Mevalonic acid, a key intermediate derived from plant carbohydrate via acetylcoen2yme A, is transformed into isopentenyl pyrophosphate (IPP) via phosphorylation, dehydration, and decarboxylation (see Alkaloids). IPP then rearranges to dimethylaHyl pyrophosphate (DMAPP). DMAPP and... 

Resias are seldom used oace and discarded. Whether the system is mn batchwise or ia columns, the resia must be periodically removed from service and regenerated. An exception is the use of a resia as a catalyst ia organic reactions. Each cycle consists of two principal steps, adsorption and regeneration, and one or more iatermediate steps, tinse and backwash. Eailure to use good practices results ia poor cycHc performance. 

Fig. 1. Principal steps in a balanced vinyl chloride process.

There are four principal steps in bromine production (/) oxidation of bromide to bromine (2) stripping bromine from the aqueous solution (3) separation of bromine from the vapor and (4) purification of the bromine. Most of the differences between the various bromine manufacturing processes are in the stripping step. 

A typical reactor operates at 600—900°C with no catalyst and a residence time of 10—12 s. It produces a 92—93% yield of carbon tetrachloride and tetrachloroethylene, based on the chlorine input. The principal steps in the process include (/) chlorination of the hydrocarbon (2) quenching of reactor effluents 3) separation of hydrogen chloride and chlorine (4) recycling of chlorine to the reactor and (i) distillation to separate reaction products from the hydrogen chloride by-product. Advantages of this process include the use of cheap raw materials, flexibiUty of the ratios of carbon tetrachloride and tetrachloroethylene produced, and utilization of waste chlorinated residues that are used as a feedstock to the reactor. The hydrogen chloride by-product can be recycled to an oxychlorination unit (30) or sold as anhydrous or aqueous hydrogen chloride. 

FIGURE 5.22 The three principal steps in electrospray mass spectrometry (ES-MS). 

A different reaction takes place between an ethereal solution of the disulfide and hydrogen azide this reaction proceeds according to Eq. (15). Probably the principal step of this reaction is the spontaneous decomposition of the disulfide into nitrogen, sulfur, and... 

Step 3 is an electrophilic substitution. The principal step of the mechanism, step 4, is a rearrangement. 

The principal step will be to determine the stage and reflux requirements. This is a relatively simple procedure when the feed is a binary mixture, but a complex... 

We use plug assisted thermoforming when we wish to make thick-walled products or thin-walled, deep draw products. The principal steps of the process are illustrated in Fig. 16.2. The first two stages are similar to those of vacuum forming. Once the sheet has been clamped, a plug made from a material with low heat conductivity is thrust downwards into the cavity,... 

A schematic representation of the principal steps (initiation, propagation and termination) of a radical chain polymerisation is presented in Figure 18. 

The second method, i.e. electroless plating, has been used also to produce graphite - Sn, Sn02 composite materials. The chemical deposition of metals on the graphite supports is performed through two principal steps. 

Figure 1.2 Schematic outlining the purification protocol. The principal steps of purifying FLAG-tagged eIF2B proteins from yeast whole cell extracts are outlined in the diagram for details, refer to the main text.

Alkylation of a-amino esters with 9-bromo-9-phenylf uorene serves as the principal step in the preparation of N-(9-phenylfluoren-9-yl)-a-amino carbonyl compounds which are useful chiral educts for asymmetric synthesis. A discussion of the synthetic utility of N-9-phenylfluoren-9-yl derivatives of amino adds and amino acid esters appears in the procedure following. 

As described earlier, the C=N double bond of the azaquinone structures is readily hydrated to provide the corresponding hydroxy derivatives, a principal step involved in their dimerization. Generally the chemis-... 

The principal step of the sampling process is the taking of the sample. Here we intend to deal only with the risk of contaminating the sample during its collection, storage and processing, since any subsequent separation is applied only after the sample has been brought into solution. 

Figure 12.12 Principal steps in the mechanism of alkaline phosphatase. (Reprinted with permission from Parkin, 2004. Copyright (2004) American Chemical Society.)...

Scheme 1. The Principal Step Involved in the Thermal Degradation of Vinylidene Chloride Polymers.

A process sequence schematic of the principal steps is given in Fig. 4.14. The process sequence is similar and compatible to the fabrication of the circular hotplate in Sect. 4.1.2. The most important modifications include the additional process steps to apply the local passivation. The modifications of the other steps are described in the following section [115]. 

The formation of benzothiazole-2-thiol (386) from aniline (385), carbon disulfide, and sulfur af 230 °C has been shown fo occur by a sequence of fhree principal steps. Labelling experiments confirmed fhaf bofh sulfur afoms originafed from carbon disulfide. An initial polar reaction to form thiocarbanilide (389) via phenylcarbamic acid... 

Refineries employ a wide spectrum of contact solvent processes, which are dependent upon the differential solubilities of the desirable and undesirable feedstock components. The principal steps are countercurrent extraction, separation of solvent and product by heating and fractionation, and solvent recovery. Naphthenics, aromatics, unsaturated hydrocarbons, and sulfur and other inorganics are separated, with the solvent extract yielding high-purity products. Many... 

Figure S.1 The principal steps of MeOH carbonyla-tion reactions.

While the main carbonylation cycles are now understood in considerable detail for these apparently simple catalytic systems, there will undoubtedly be considerably more work done on these and related sytems to understand the factors influencing the principal steps of oxidative addition, migratory insertion and reductive elimination and, in particular, further work to understand the unwanted reactions that lead to by-products. 

Scheme 7.2 summarises the principal steps of the alternating ethene/CO copolymerisation in MeOH by Pd" catalysts modified with bidentate ligands [lb,c]. 

Here pn is 1,2-diaminopropane and bn is 2,3-diaminobutane. Decomposition of the amine cation radicals obtained by photooxidation of the ligands en, bn, and pn have been discussed by Moeller. The products of Co(en)33+ photolysis can be satisfactorily explained by postulating that carbon-carbon bondbreaking is the principal step in decomposition of the cation radical H2NCH2CH2NH2t.58 Presuming a similar mechanism to obtain in photoreduction of Co(pn)33+, there are then two possible reaction pathways leading to different products. 

Fig. 12.3. Principle of the two-component pathway. The fignre shows the principal steps of the two-component pathway in bacterial systems. An extraceUnlar signal (change in osmolarity, N availability, etc.) is registered by a receptor. An interaction takes place with the first component, the sensor kinase", which undergoes autophosphorylation at a His residue (H). The phosphate residue is transferred to the carboxyl side chain of an Asp residue (D) of the reaction regulator. Phosphorylation of the second component activates this for further signal conduction. The sen-sor kinase" may also be localized in the cytoplasmic domain of the receptor.

Identifying a suitable developmental project requires that you apply creative processes to originating a specific idea for improvement or change and translating it into a practical plan of action. Figure 4.1 sets out the principal steps involved. Referring to Figure 4.1 ... 

The pathway for the formation and metabolism of angiotensin II (Ang II) is summarized in Figure 17-1. The principal steps include enzymatic cleavage of angiotensin I (Ang I) from angiotensinogen by renin, conversion of Ang I to Ang II by converting enzyme, and degradation of Ang II by several peptidases. 

Integration of systems of nonlinear partial differential equations (54),(86) has been performed [33,49]. Here we indicate the principal steps of the integration procedure. While integrating (54),(86), we essentially apply the fact that the general solution of system of equations 1,2 from (86) is known [62]. With already known (x) in hand, we proceed to integrating linear partial differential equations 3,4 from (86). Next, we insert the results obtained into the remaining equations and get the final forms of the functions (x), ). 

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