Dielectrics, thick-film dielectric constant

However, for the oxide electrode, such as SrRuOj, the structural similarity of the electrode and dielectric material allows a certain penetration of the dielectric polarization into the oxide electrode. As a result, the formation of the intrinsic low dielectric interfacial layer is effectively suppressed and film thickness independent dielectric constants are obtained, as reported by the author for the case of sputtered BST films on IrO electrodes and more recently reported by Toshiba researchers for the case of MOCVD BST films on SrRu03 electrodes. Under these circumstances dielectric constants are solely determined by processing conditions. The stoichiometric composition and good crystallization of the films are the two most important parameters for a high dielectric constant. 

The effect of nanometer dielectric films on the ellipsometric parameters and reflectance of linearly polarized light is investigated within the framework of the perturbation theory. The novel approach is developed for simultaneous determining the thickness and dielectric constant of nanometer-scale films by the differential reflectance and ellipsometric measurements. 

Optical techniques can be used to monitor optical thickness and dielectric constant parameters. This includes ellipsometry, multiple reflection interferometry (74), evanescent wave (75), and surface plasmon resonance spectroscopy techniques (43). Ellipsometry has been used widely and routinely to investigate film thickness of pol3mier brush films (76). For optical properties of films, it is important that the average film roughness and imiformity is specified. Often, sampling is localized by the spot size, such that it is necessary to probe and average different areas of a sample. 

PI structures Film types Film thickness (pm) Dielectric constant (k) 1MHz Porosity (%)... 

Insulator Dielectrics. Insulator thick film dielectrics are multiphase materials. The electronic, ionic, and interfacial polarization mechanisms all contribute to the dielectric constant of glass-ceramic materials. Electronic polarization is directly proportional to the density of electrons in the glass-ceramic. Thus, dielectrics based on glasses containing oxides of high atomic number elements (e.g., lead) or high density exhibit high dielectric constants. 

The fired micro structure of a thick film dielectric contains ferroelectric phases and other phases produced by sintering additives or modifiers. The dielectric constant of this complex mixture of phases can be estimated by using various mixture rules. For example, one of the mixture rules used in estimating the dielectric constant of a mixture is... 

Whenever the lateral interaction in an adlayer is weak, we observe a linear dependence of I R/R on coverage 6 (or on the average film thickness d). Such a relation, which simply implies that the film dielectric constants, ej, are independent of 0 (Eq. 29), is conveniently used for a precise determination of coverages and hence of adsorption isotherms. Especially in cases like halide adsorption where the evaluation of surface excesses from charge measurements is hampered by an unknown electrosorption valency (unless a very elaborate concentration dependence study is made " ), the spectroscopic method of determining coverages can indeed be advantageous. Adzic et have... 

Dielectric constants of metals, semiconductors and insulators can be detennined from ellipsometry measurements [38, 39]. Since the dielectric constant can vary depending on the way in which a fihn is grown, the measurement of accurate film thicknesses relies on having accurate values of the dielectric constant. One connnon procedure for detennining dielectric constants is by using a Kramers-Kronig analysis of spectroscopic reflectance data [39]. This method suffers from the series-tennination error as well as the difficulty of making corrections for the presence of overlayer contaminants. The ellipsometry method is for the most part free of both these sources of error and thus yields the most accurate values to date [39]. 

Dielectric Film Deposition. Dielectric films are found in all VLSI circuits to provide insulation between conducting layers, as diffusion and ion implantation (qv) masks, for diffusion from doped oxides, to cap doped films to prevent outdiffusion, and for passivating devices as a measure of protection against external contamination, moisture, and scratches. Properties that define the nature and function of dielectric films are the dielectric constant, the process temperature, and specific fabrication characteristics such as step coverage, gap-filling capabihties, density stress, contamination, thickness uniformity, deposition rate, and moisture resistance (2). Several processes are used to deposit dielectric films including atmospheric pressure CVD (APCVD), low pressure CVD (LPCVD), or plasma-enhanced CVD (PECVD) (see Plasma technology). 

Let s consider the simple case of a point charge at a distance z over a film of thickness L and dielectric constant ei on a substrate of dielectric constant S2 [29], In this case the force can be calculated exactly by the multiple-image method. The result is ... 

Replacement of gas by the nonpolar (e.g., hydrocarbon) phase (oil phase) has been sometimes used to modify the interactions among molecules in a spread film of long-chain substances. The nonpolar solvent/water interface possesses an advantage over that between gas and water in that cohesion (i.e., interactions between adsorbed molecules) due to dipole and van der Waals s forces is negligible. Thus, at the oil/water interfaces, the behavior of adsorbates is much more ideal, but quantitative interpretation may be uncertain, in particular for the higher chains, which are predominantly dissolved in the oil phase to an unknown extent. The oil phase is poured on the surface of an aqueous solution. Thus, the hydrocarbon, such as heptane or decane, forms a membrane a few millimeters thick. It is thicker than the adsorbed monolayer. Owing to the small difference in dielectric constant between the air and a hydrocarbon oil, the... 

The copyrolysis of 1 wt% dibromotetrafluoro-p-xylylene with commercially available hexafluoro-p-xylene (Aldrich) with metals was examined and it was found that it was indeed possible to prepare films that were spectroscopically indistinguishable from those deposited from dimer. The PA-F films obtained are of excellent quality, having dielectric constants of2.2-2.3 at 1 MHz and dissociation temperatures up to 530°C in N2. A uniformity of better than 10% can be routinely achieved with a 0.5-gm-thick film on a 5-in. silicon wafer with no measurable impurities as determined by XPS. During a typical deposition, the precursor was maintained at 50°C, the reaction zone (a ceramic tube packed with Cu or Ni) was kept at 375-550°C, and the substrate was cooled to -10 to -20°C. The deposited film had an atomic composition, C F 0 = 66 33 1 3 as determined by XPS. Except for 0, no impurities were detected. Within instrumental error, the film is stoichiometric. Poly(tetrafluoro-p-xylylene) has a theoretical composition ofC F = 2 1. Figure 18.2 illustrates the XPS ofthe binding energy... 

The CCS approach is well matched to the synthesis part of the problem of the identification of new thin-film high dielectric constant materials for embedded DRAM applications. As noted above, low-temperature deposition is essential and the CCS approach provides in situ mixing at low temperatures. Samples are obtained in thin-film form and can be made in thicknesses that are similar to those that will actually be used. 

---