Front double-sided

Double-sided brush scrubbing followed by a spin-rinse-dry step dominates the industry. An example of a double-sided brush scrubber is shown schematically in Fig. 16. The rollers keep the wafer positioned and rotating while the brushes dean debris from both the front and back sides of the wafer. The cleaning solution is delivered through the bristles themselves. Typically, the bristles are porous so that fresh solution can be delivered directly to the wafer and minimal amounts of debris accumulate on the brush. Increasing the down force increases the particle removal efficiency up... 

Brush Cleaning Since the introduction of the CMP process, the most commonly used material for brush cleaning has been PVA. In order to receive thoroughly clean surfaces, the wafer is usually sandwiched between the double-sided brush scrubbers so that the front and back sides of the wafer can be cleaned simultaneously (Fig. 16.6). In addition, a lateral brush is used to clean the edges of the wafer. 

Regarding the supply and removal of the medium to be pumped by the front surfaces of the respective compressor stage, one distinguishes single-sided and double-sided pressurised machines. 

In Figure 3.5, a double-sided pressurised machine is described. It possesses two inter casings with suction and pressure ports, so that an exchange of the medium to be compressed can take place via both front faces of the compressor stage. This type of arrangement is necessary if large suction capacities are to be realised with comparatively long impellers. 

Figure 13.7 Side view of a double front panel with a common horizontal bus, but separate vertical bus bars (not visible) (Courtesy ECS)...

To explain the very varied behaviour patterns shown by the various monomers in various solvents, use has been made of a further, hitherto unrealized, implication of the model, namely that the rate of the isomerization-propagation must depend upon the electrochemical environment of the complex. This vague idea has been given precision by concentrating attention on the species which occupies the site at the back-side of the near-planar carbenium ion, the front-side of which is 7t-bonded to the double bond of the monomer. The idea is that the stronger the dipole at the back, the weaker is the Jt-bond, and the lower is the energy of the transition state, and therefore the greater is the rate. 

Figure 2-15 A stereoscopic alpha-carbon plot showing the three-dimensional structure of favin, a sugar-binding lectin from the broad bean (Viciafaba). In this plot only the a-carbon atoms are shown at the vertices. The planar peptide units are represented as straight line segments. Side chains are not shown. The protein consists of two identical subunits, each composed of a 20-kDa a chain and a 20-kDa 3 chain. The view is down the twofold rotational axis of the molecule. In the upper subunit the residues involved in the front 3 sheet are connected by double lines, while those in the back sheet are connected by heavy solid lines. In the lower subunit the a chain is emphasized. Notice how the back 3 sheet (not the chain) is continuous between the two subunits. Sites for bound Mn2+ (MN), Ca2+ (CA), and sugar (CHO) are marked by larger circles. From Reeke and Becker.112...

NMR studies of polymers made with deuterated monomers provide additional information on the cyclic isotactic transition state. Miyazawa and Ideyuchi (97) have shown that the isotactic polymerization of propylene takes place with cis opening of the olefinic double bond. This shows that the 4-membered cyclic transition occurs with reaction of the new monomer on the front side of the propagating ion as illustrated in Fig. 12. 

Intermediate 46 is responsible for the retention of configuration observed by Shoppee. The 5,6-double bond that has displaced the leaving group from the back side now shields this side from attack by the entering group, thus leaving the front side as the only available route to substitution. 

In addition to the locations of the double bonds, another difference of alkenes is the molecule s inability to rotate at the double bond. With alkanes, when substituent groups attach to a carbon, the molecule can rotate around the C-C bonds in response to electron-electron repulsions. Because the double bond in the alkene is composed of both sigma and pi bonds, the molecule can t rotate around the double bond (see Chapter 6). What this means for alkenes is that the molecule can have different structural orientations around the double bond. These different orientations allow a new kind of isomerism, known as geometrical isomerism. When the non-hydrogen parts of the molecule are on the same side of the molecule, the term cis- is placed in front of the name. When the non-hydrogen parts are placed on opposite sides of the molecule, the term trans- is placed in front of the name. In the previous section, you saw that the alkane butane has only two isomers. Because of geometrical isomerism, butene has four isomers, shown in Figure 19.12. 

To explain the formation of (S )-(+)-/3-methylhydrocinnamic acid by the reaction of the D-xylofuranose derivative 20 with phenylmagnesium bromide in the absence of cuprous chloride, the coordinated adduct 20 was envisaged as the precursor, with attack from the front side of the double bond now giving the acid having the S-configuration. 

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