Semiconductor dielectric

For films on non-metallic substrates (semiconductors, dielectrics) the situation is much more complex. In contrast with metallic surfaces both parallel and perpendicular vibrational components of the adsorbate can be detected. The sign and intensity of RAIRS-bands depend heavily on the angle of incidence, on the polarization of the radiation, and on the orientation of vibrational transition moments [4.267]. 

The most important aspect of this project was the time line. In mid-1996 the specific polymer composition was selected, and in April 1997 Dow publicly announced what became known as SiLK Semiconductor Dielectric. In April 2000, IBM reported the complete integration of the SiLK dielectric and copper wiring and announced its intent to commercially fabricate integrated circuits using SiLK resin. 

Dielectric Constant The dielectric constant of material represents its ability to reduce the electric force between two charges separated in space. This property is useful in process control for polymers, ceramic materials, and semiconductors. Dielectric constants are measured with respect to vacuum (1.0) typical values range from 2 (benzene) to 33 (methanol) to 80 (water). The value for water is higher than that for most plastics. A measuring cell is made of glass or some other insulating material and is usually doughnut-shaped, with the cylinders coated with metal, which constitute the plates of the capacitor. 

As with crystalline organic semiconductors, there are only few systematic and quantitative studies of bias stress in polymeric TFTs. For example, it is still unclear whether in all polymers a positive VG leads to positive Vj shifts [7, 18]. Here we will concentrate on negative AVT after application of a negative Vg, which is nearly universally observed in p-type devices with a number of semiconductor-dielectric combinations. In the next section of this chapter we will focus on studies of poly-fluorene and polythiophene TFTs, because these are the polymer devices for which bias stress has been most thoroughly characterized in recent years. 

Later, the evolution of the electronic industry initiated the development of an immense variety of materials and devises based, essentially, on the properties of semiconductor, dielectric, ferromagnetic, superconductor, and ferroelectric materials. 

In the top-gate architecture, the semiconductor is deposited before the gate dielectric and the gate electrode. This has several advantages. First, since the semiconductor is deposited on a known surface (the substrate itself, in typical examples), it is possible to exploit the fact that this substrate is typically extremely smooth and of known chemistry to ensure that the quality of the printed semiconductor is maximized. Most current in a transistor flows very close to the semiconductor-dielectric interface. In a top-gated transistor, therefore, this current flows near the top interface of the semiconductor this may then be optimized to maximize the quality of the same. Additionally, since this layer is covered by the dielectric and gate, it may be protected from damage from subsequent process steps, etc. 

Lucovsky, G. Yang, H. Niimi, H. Thorpe, M.F. Phillips, J.C. Intrinsic limitations on ultimate device performance and reliability at (I) semiconductor-dielectric interfaces and (II) internal interfaces in stacked dielectrics. J. Vac. Sci. Technol. 2000, B18, 2179-2186. 

In the case of QW heterostructures, the electron and hole of an exciton are well confined within the layer since the band gap discontinuity is quite large, especially for III-V heterostructuies. On the other hand, dielectric and lattice properties of group III (II) and group V (VI) semiconductors (dielectric permittivities, lattice constants, elastic moduli) are in close proximity in their values [7]. Therefore, we model our system by the localized quasi-2D IS-exciton interacting with bulk-like phonon modes in the QW with infinite potential barriers. We describe such an excitonic state by quasi-2D wave fimction... 

As shown in Fig. 7.26, when the sensor is exposed to vapor, individual molecules can diffuse into the semiconductor thin film and be adsorbed mostly at the grain boundaries [13], If the adsorbed analytes have large dipole moment, such as H2O ( 2 debye) and DMMP ( 3 debye), the adsorption of those analyte molecules at the grain boundaries close to or at the semiconductor-dielectric interface can locally perturb the electrical profile around the conduction channel, and hence change the trap density in the active layer. We can interpret the trapping effects by a simple electrostatic model discussed briefly in Sect. 7.2. The electric field induced by a dipole with dipole moment of p (magnitude qL in Fig. 7.4) is ... 

One frequently examined interface is the solid-liquid interface, where the solid phase may be a dielectric, a semiconductor, or a metal. Species located at these interfaces are of primary importance in electtochemisny and in chemistry of surface-active substances (surfactants). Another common type of interface is the solid-solid interface, specifically dielectric-dielectric, dielectric-semiconductor, dielectric-metal, semiconductor-semiconductor, semiconductor-metal, and metal-metal interfaces. These structures have an extremely important role in such areas as microelectronics and the chemistry of composites. Furthermore, positioning an ultrathin film at the interface of two media, one can substantially increase surface sensitivity of all IR spectroscopic methods. 

Measuring the spectrum of a layer located at the semiconductor (dielectric)-metal interface is more complicated. Snch systems are widespread and are found, for example, in microelectronics, and in particnlar in integrated circuits. To record the spectra of such layers, a special method was proposed [79] in which the incoming beam is incident onto a transparent plate at the angle (pi = (pg = arctan(n2/ni) ( i and nz are the refractive indices of the snrround-ings and the semiconductor plate, respectively) (Fig. 2.33). At such angle of incidence, the intensity of p-polarized radiation reflected from the front plane of... 

Here, R1-R5 are the reflectances at the air-semiconductor, semiconductor-dielectric, dielectric-metal, and dielectric-air interfaces and metallic mirror, respectively 2d and Idz are the effective thicknesses of the dielectric layer corresponding to the optical pathlength of the light beam before and after the metal deposition and o-oi, o-i, and q 2 are the absorption coefficients of the dielectric layer at the TO (before and after the metal deposition) and LO frequencies, respectively. The intensity of the incident IR radiation /q is assumed to be independent of the frequency. 

Organic electronics relies on electrically active materials that can be used as conductors, semiconductors, dielectrics, luminescent, electrochromic or electrophoretic materials. The materials have to be carefully chosen since process conditions and the interplay with the other layers will influence the performance of the device. Many approaches are being taken on the material side which have resulted in, as yet, unresolved questions such as organic or inorganic Solntion based or evaporated It is very likely that several approaches will be used in parallel. 

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