Vapor-phase silanization reactions

Surface Modification with Chlorosilanes. Chlorosilanes are volatile and very sensitive to the presence of trace amounts of water. Vapor-phase silanization reactions with rigorous control of the absence of water show that Cl SiMe4-n-type chlorosilanes react with aerosil (nonporous microparticulate silica) as... 

Figure 10 Dark and photocurrents with FeCp 70 redox couple before and after interfacial passivation, (a) Effect of blocking recombination at the Sn02 surface, reaction (5) (Fig. 9a), by electropolymerization of PPO. (b) Effect of blocking recombination at both the Sn02 and Ti02 surfaces, reactions (4) and (5) (Fig. 9b), by vapor-phase silane treatment without PPO. (Data from Ref. 49.)...

Byproduct adsorption and/or reaction is an ubiquitous feature in vapor phase silanizations. We include the possibility of reaction because of the following experiments. Exposure of clean pellet to byproducts (HC1, CH3OH, or NH3) generates the respective absorption bands cited above, but it also causes gross attenuation of the 0-H bands. Such a result is consistent with equation 2 ... 

An interesting question is whether these results are characteristic of vapor-phase silanizations or whether they extend to liquid-phase reaction conditions. Silanizations are most commonly performed in solutions. We are pursuing this question currently. 

Despite the potential for atomic-scale manipulation of interfaces displayed by molecular-beam epitaxial growth, a majority of the vapor-phase growth of silicon is accomplished by the reaction of silane with silicon substrates This... 

TFSA satisfies all these requirements for hydrophilic silicone surfaces. Using silica as a model for extensively oxidized silicone surfaces, we showed that silylation with vapor phase TFSA took place at room temperature under scrupulously dry conditions. In contrast, others have found for the more conventional silylating agents, the methylchlorosilanes and the methylmethoxy-silanes, that no reaction occurred at temperature below 200°C under similar dry conditions [38]. 

The double promoter process involves the successive application of liquid promoter solutions of vinyltrichlorosilane (VTS) and 3-chloropropyltrimethoxy-silane followed by successive cure cycles in dry N2 at 90°C after each application and before photoresist application. The double promoter process evolved because it was felt that the silane reaction with the SiOH surface groups of low temperature oxides was incomplete for a single promoter application, and because vapor silane equipment did not exist at that time. Interestingly, a double HMDS liquid promoter process failed to yield adequate adhesion as well. Later in time, the successful but somewhat complex double promoter process was replaced by the vapor phase HMDS process in the Star 1000 (or 2000) then superior resist image adhesion was obtained on all four oxide substrates with all the photoresists tested. Before the advent of the HMDS vapor priming in standalone or wafer track equipment module chambers, liquid priming solutions were widely used, especially in development areas. 

Dehydrodimerization. On excitation with a mercury vapor lamp, mercury is converted to an excited state, Hg, which can convert a C—H bond into a carbon radical and a hydrogen atom. This process can result in dehydrodimerization, which has been known for some time, but which has not been synthetically useful because of low yields when carried out in solution. Brown and Crabtree1 have shown that this reaction can be synthetically useful when carried out in the vapor phase, in which the reaction is much faster than in a liquid phase, and in which very high selectivities are attainable. Secondary C—H bonds are cleaved more readily than primary ones, and tertiary C—H bonds are cleaved the most readily. Isobutane is dimerized exclusively to 2,2,3,3-tetramethylbutane. This dehydrodimerization is also applicable to alcohols, ethers, and silanes. Cross-dehydrodimerization is also possible, and is a useful synthetic reaction. 

Dichlorocarbene. This silane decomposes in the vapor phase at 120-140° to liberate dichlorocarbene and SiF3Cl. Added olefins are converted into gem-dichlorocyclopropanes in 85-95% yields. The reaction is stereospecific with cis- and tra/is-2-butene. ... 

Vapor phase reaction of SiCU or silane (SilE) with... 

In contrast to the Si-melt infiltration, highly porous, single-phase, biomorphous SiC-ceramics can be manufactured by the reactive infiltration of gaseous Si-containing reactants such as Si/SiO-vapor or silanes ]355, 356]. Based on rapid fluid infiltration into the accessible cellular template structure, a variety of chemical processing routes offer a wide range of chemical compositions and structural modifications in the ceramic reaction products. 

Fumed silica, or fumed silicon dioxide, is produced by the vapor phase hydrolysis of silicon tetrachloride in an H2/O2 flame. The reactions are shovm in Chapter 19. Hydrophilic fumed silica bearing hydroxyl groups on its surface is produced by this process. Hydrophobic fumed silica is made by processing fumed hydrophilic silica through in-line hydrophobic treatments such as with silanes, siloxanes, silazanes, and so on [1]. Examples of different types of hydrophobic fumed silica coatings include DMDS (dimethyldichlorosilane), TMOS (trimethoxyoctylsilane), HMDS (hexamethyldisilazane). 

Pressureless sintered SiC bodies made from ultrafine SiC powders which are themselves highly milled Aecheson powders or are made from vapor-phase reactions of silanes with hydroearbons. Such ultrafine powders are usually mixed with carbon and boron sintering aids in order to achieve the necessary high densities. 

Chemical vapor deposition (CVD) The deposition of atoms or molecules by the reduction or decomposition of a chemical vapor species (precursor vapor) that contains the material to be deposited. Example Silicon (Si) from silane (SiH4). See also Vapor phase epitaxy (VPE) Decomposition reaction (CVD) Reduction reaction (CVD) Disproportionation reaction (CVD). 

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