Micro displays

OLEDs are normally fabricated on a transparent substrate and therefore on top of a transparent anode. However, several potential applications, such as micro-displays integrated on a crystalline silicon chip or a totally transparent OLED array for a heads-up display, require a transparent top electrode. There has been some work published describing the development of transparent cathodes. The most obvious approach is to use a very thin metal layer, such as Mg Ag, overcoated with a transparent conductor, such a.s ITO [94]. This is not so trivial as it appears, since the cathode metal must survive the reactive sputtering process employed to deposit the ITO. Another approach uses no metal but rather a CuPc layer between the electron-transporting Alqs and the ITO [95]. It is suggested dial the oxidative environment during ITO deposition results in heavy n-type doping near the CuPc interface. 

As indicated in the previous sections, CMP has found many applications in the manufacturing of More than Moore devices. In this chapter, examples will be discussed where polishing processes have to be employed for the manufacturing of power devices, MEMS and MOEMS chips, and micro-displays. The described applications are exemplary and do not claim completeness. Wafer bonding will be covered with examples from the fields of stacked devices and wafer-level packaging (WLP), while TSVs will be treated in more depth in a separate chapter in this book. 

Micro displays using OLED technology are active displays and show a very high brightness in comparison to back-lit LCD displays. They are used, for example, for electronic viewfinders of very advanced system cameras. The assembly consists of a CMOS circuit to drive the individual cells and a structured OLED layer on top. 

Figure 18.18 200 mm wafer with OLED micro-displays after grinding and polishing of the glass covers (a) and test of the finished OLED micro-display (b). 

Pseudomorphism received methodical study from about 1905. A micro-section taken across the interface between a substrate and an electrodeposit shows the grain boundaries of the former continue across the interface into the deposit (Fig. 12.5). As grain boundaries are internal faces of metal crystals, when they continue into the deposit the latter is displaying the form of the substrate. Hothersall s 1935 paper contains numerous excellent illustrations with substrates and deposits chosen from six different metals, crystallising in different lattice systems and with different equilibrium spacing. Grain boundary continuation and hence pseudomorphism is evident despite the differences. 

In more sophisticated instruments, the modern tendency is to replace the micro-ammeter by a digital read-out, and there is an increasing trend to use visual display units to show the results. Such instruments are controlled by microprocessors which may either show sequentially the successive operations which must be performed to measure the absorbance of a solution at a fixed wavelength or to observe the absorption spectrum of a sample alternatively the whole procedure may be automated. Such instruments will display the absorption spectrum on the VDU screen, and by linking to a printer, a permanent record is produced. 

In Spite of the existence of numerous experimental and theoretical investigations, a number of principal problems related to micro-fluid hydrodynamics are not well-studied. There are contradictory data on the drag in micro-channels, transition from laminar to turbulent flow, etc. That leads to difficulties in understanding the essence of this phenomenon and is a basis for questionable discoveries of special microeffects (Duncan and Peterson 1994 Ho and Tai 1998 Plam 2000 Herwig 2000 Herwig and Hausner 2003 Gad-el-Hak 2003). The latter were revealed by comparison of experimental data with predictions of a conventional theory based on the Navier-Stokes equations. The discrepancy between these data was interpreted as a display of new effects of flow in micro-channels. It should be noted that actual conditions of several experiments were often not identical to conditions that were used in the theoretical models. For this reason, the analysis of sources of disparity between the theory and experiment is of significance. 

We begin the comparison of experimental data with predictions of the conventional theory for results related to flow of incompressible fluids in smooth micro-channels. For liquid flow in the channels with the hydraulic diameter ranging from 10 m to 10 m the Knudsen number is much smaller than unity. Under these conditions, one might expect a fairly good agreement between the theoretical and experimental results. On the other hand, the existence of discrepancy between those results can be treated as a display of specific features of flow, which were not accounted for by the conventional theory. Bearing in mind these circumstances, we consider such experiments, which were performed under conditions close to those used for the theoretical description of flows in circular, rectangular, and trapezoidal micro-channels. 

The second case study. This involves all silica micro- and mesoporous SBA-15 materials. SBA-15 materials are prepared using triblock copolymers as structure-directing templates. Typically, calcined SBA-15 displays pore sizes between 50 and 90 A and specific surface areas of 600-700 m g with pore volumes of 0.8-1.2cm g h Application of the Fenton concept to mesoporous materials looks simpler since mass transfer would be much less limited. However, it is not straightforward because hydrolysis can take place in the aqueous phase. 

The importance of surface characterization in molecular architecture chemistry and engineering is obvious. Solid surfaces are becoming essential building blocks for constructing molecular architectures, as demonstrated in self-assembled monolayer formation [6] and alternate layer-by-layer adsorption [7]. Surface-induced structuring of liqnids is also well-known [8,9], which has implications for micro- and nano-technologies (i.e., liqnid crystal displays and micromachines). The virtue of the force measurement has been demonstrated, for example, in our report on novel molecular architectures (alcohol clusters) at solid-liquid interfaces [10]. 

For axial dispersion in the micro-channel reactor, the usual relationships from Taylor-Aris theory were employed. In order to assess the performance of both reactor types, the widths of two initially delta-like concentration tracers are compared after they have passed through the flow domain. The results of this comparison are displayed in Figure 1.16. 

Figure 2.42 Micro mixer geometry with staggered groove structures on the bottom wall, as considered in [137], The top of the figure shows a schematic view of the channel cross-section with the vortices induced by the grooves. At the bottom, confocal micrographs showing the distribution of two liquids over the cross-section are displayed.

In contrast to this result, polymer samples taken from processing without a micro mixer displayed a small but significant fraction of high-molecular weight polymer with a mass > 10 [126]. Here, in some cases, heavy precipitation occurred, resulting even in plugging of the static-mixer internals of the tube reactors [125]. 

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