Carrier design

The simplicity of early carrier designs was complicated by their use as part of the robot used to move wafers from the load cassette to the unload cassette. On a so-called gimbaled carrier, the down force was applied to a central point on a plate behind the wafer, and it was assumed that the applied force was transferred through the wafer backing plate to be distributed uniformly across the wafer. Lateral motion of the pad then caused a torque to be applied to the carrier. To compensate for this rotation, a gimbal was built into the carrier at the point where the down force was applied. 

This approach has proved to be so successful that it has spawned a cottage industry of carrier designs based on the use of hydrostatic pressure. With some of these inventions a backing plate is present, with others [32]... 

Fig. 9. (a) The distributed polish head extends the concept of hydrostatic pressure by integrating polish blocks in the carrier design to ensure that locally the spatial variation in the polish pressure is low, (b) Schematic representation of the region on a wafer that a polish block may contact. 

Preston s equation indicates a pressure dependency and if the pressure distribution across the surface of the wafer is not uniform, one expects a wafer-level removal rate dependency. Runnels et al, for example, report a model incorporating pressure dependencies to account for wafer scale nonuniformity [42]. The distribution of applied force across the surface of the wafer is highly dependent on the wafer carrier design, and significant innovation in head design to achieve either uniform or controllable pressure distributions is an important area of development. 

Kono K. Apphcation of dendrimers to dmg delivery systems—from the view point of carrier design based on nanotechnology. Dmg Deliv Syst 2002 17 462-470. 

A biopolymer-based drug carrier designed for protein delivery must meet the following requirements. In addition to controlling the release of drug, (1) the carrier must be biocompatible and degraded products must be nontoxic, (2) the carrier must incorporate the protein in a sufficiently gentle manner to retain bioactive conformation, and (3) the carrier must be able to incorporate the protein in pharmaceutical scale [12]. 

Transport is a three-phase process, whereas homogeneous chemical and phase-transfer [2.87, 2.88] catalyses are single phase and two-phase respectively. Carrier design is the major feature of the organic chemistry of membrane transport since the carrier determines the nature of the substrate, the physico-chemical features (rate, selectivity) and the type of process (facilitated diffusion, coupling to gradients and flows of other species, active transport). Since they may in principle be modified at will, synthetic carriers offer the possibility to monitor the transport process via the structure of the ligand and to analyse the effect of various structural units on the thermodynamic and kinetic parameters that determine transport rates and selectivity. 

The question of carrier design was first addressed for the transport of inorganic cations. In fact, selective alkali cation transport was one of the initial objectives of our work on cryptates [1.26a, 6.4]. Natural acyclic and macrocyclic ligands (such as monensin, valinomycin, enniatin, nonactin, etc.) were found early on to act as selective ion carriers, ionophores and have been extensively studied, in particular in view of their antibiotic properties [1.21, 6.5]. The discovery of the cation binding properties of crown ethers and of cryptates led to active investigations of the ionophoretic properties of these synthetic compounds [2.3c, 6.1,6.2,6.4-6.13], The first step resides in the ability of these substances to lipophilize cations by complexation and to extract them into an organic or membrane phase [6.14, 6.15]. 

Figure 9. Low temperature carrier designed to accommodate 20 No. 3 cylinders. For irradiations at controlled temperatures between room temperature and —190°C.

Touitou, E., et al. 1994. Modulation of caffeine skin delivery by carrier design Liposomes versus permeation enhancers. Int J Pharm 103 131. 

Carrier based pH membranes (4-7) have traditionally required the addition of trapped, hydrophobic negative sites, typically tetraphenylborate (TPB) and p-chlorotetraphenyl borate (p-CITPB). In comparative studies we have frequently noticed the improved pH response of the membranes containing additional sites compared with those with only naturally occurring fixed sites, found in all the PVCs we have tested. Specifically, there is a distinctive deterioration in accuracy in the latter sensors at low pH. In addition, membranes prepared from aminated PVC with TPB have previously shown a good pH response (8). However, our preliminary impedance studies have shown that undoped aminated PVC membranes have a relatively low conductivity when compared with the neutral carrier designs above. 

FIGURE 3.13 Several methods to control the polishing profile such as process conditions, carrier design, pad roughness, conditioner (dresser) design, and slurry. 

Figure 3.14 shows the polishing profile control by carrier design. The polishing profile of the wafer center area can be modulated by backside pressure and modification at the carrier center. The polishing profile of the... 

FIGURE 3.14 Schematic illustration of how carrier design can affect the polishing profile. 

Mezo, G., Kajtar, J., Nagy, I., Szekerke, M., and Hudecz, F. (1997) Carrier design Synthesis and conformational studies of poly[L-lysine] based branched polypeptides with hydroxyl groups. Biopolymers 42, 719-730. 

Hudecz, F., Nagy, I. B., Koczan, G., Alsina, M. A., and Reig, F. (2001) Carrier design influence of charge on interaction of branched polymeric polypeptides with phospholipid model membranes, in Biomedical Polymers and Polymer Therapeutics (Chiellini, E., Sunamoto, J., Migliaresi, C., Ottenbrite, R. M., and Cohn, D. eds.), Kluwer Academic/Plenum Publishers, New York, pp. 103-120. 

Photosynthetically active quinones include plastoquinone of green-plant photosystem II, ubiquinone and menaquinone in photosynthetic bacteria, and phylloquinone in photosystem I. Plastoquinone is present in green-plant photosystem II both as a tightly-bound and a loosely-bound electron carrier, designated Qa and Qb, respectively. Qa is photoreduced only to the semiquinone (PQ ) but Qb can accept two electrons, forming the plastohydroquinone (PQ-Hj) [see Chapters 5, 6 and 16 for further discussion]. Plastohydroquinone PQb H2 is the final reduction product of photosystem II and goes on to reduce the cytochrome bj complex as part of the electron transport and proton translocation processes [see Chapter 35 for detailed discussions]. 

There are broadly two types of product handling conveyors used in cobalt-60 gamma irradiators, conveyor bed designs and carrier designs. 

Vauthier C, Fattal E, Labarre D (2004). From polymer chemistry and physicochemis-try to nanoparticulate drug carrier design and applications. In Yaszemski M J, Trantolo D J, Lewandrowski K V, et al. (eds.). Tissue Engineering and Novel Delivery System Marcel Dekker, New York, pp. 562-598. 

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