Multilayers, electronic devices

Recently commercially available X-ray systems for laminography have a spatial resolution limited to hundred microns, which is not enough for modem multilayer electronic devices and assembles. Modem PCBs, flip-chips, BGA-connections etc. can contain contacts and soldering points of 10 to 20 microns. The classical approach for industrial laminography in electronic applications is shown in Fig.2. 

The ability to apply a planarizing, optically transparent, thermally stable polymer system that cures under relatively mild conditions has recently been demonstrated to have utility in the fabrication of multilayer devices such as advanced color liquid-crystal display31,32 The ability to apply this material as a dielectric or optical coating for thin-film electronics devices has also recently been demonstrated with the fabrication of an optical wave guiding device.33... 

Thin films (qv) of vitreous silica have been used extensively in semiconductor technology. These serve as insulating layers between conductor stripes and a semiconductor surface in integrated circuits, and as a surface passivation material in planar diodes, transistors, and injection lasers. They are also used for diffusion masking, as etchant surfaces, and for encapsulation and protection of completed electronic devices. Thin films serve an important function in multilayer conductor insulation technology where a variety of conducting paths are deposited in overlay patterns and insulating layers are required for separation. 

Figure 10.1 A prototype multilayered organic thin film as a molecular electronic device. The layers were deposited on a glass substrate (which may be coated with a transparent metal electrode). The first layer contains an electron donor, carbocyanine (D), dispersed in a fatty acid monolayer matrix. The second and third layers contain quinquethienyl as molecular wires (Wj and W2). The fourth layer (A) consists of a monolayer of bipyridinum as the electron acceptor. The energy diagram is shown below. A device like this imitates the photosynthetic reaction center (biomimetic device). (Reproduced from [8].)...

Figure 14-16. Multilayer EL device composed of HITL (hole-injection and transport layer), EITL (electron-injection and transfer layer) and EML (emitter layer).

There may be a useful niche for multilayer LB films as passive layers in electronic devices. For example, even a single monolayer is sufficient to increase the breakdown strength of a leaky oxide film °. In order to illustrate the effectiveness... 

In addition, if these assemblies can be effectively coupled to appropriate solid supports including sensing devices, they may find application in such molecular electronic devices as ultrathin electrodes and interconnects in multilayer superlattices, optical waveguides and switches, and chemical and biochemical sensors. 

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