Leveling thin-film fabrication process

Interconnect. Three-dimensional structures require interconnections between the various levels. This is achieved by small, high aspect-ratio holes that provide electrical contact. These holes include the contact fills which connect the semiconductor silicon area of the device to the first-level metal, and the via holes which connect the first level metal to the second and subsequent metal levels (see Fig. 13.1). The interconnect presents a major fabrication challenge since these high-aspect holes, which may be as small as 0.25 im across, must be completely filled with a diffusion barrier material (such as CVD titanium nitride) and a conductor metal such as CVD tungsten. The ability to fill the interconnects is a major factor in selecting a thin-film deposition process. 

Micro/nanostructures generated using these and related top-down approaches are geometrically and electrically homogeneous, with layouts that can be controlled over a wide range to realize not only ribbons and wires but also bars, platelets, membranes, and other structures. The main limitations of the top-down approach are as follows (1) The composition of the fabricated objects is limited to materials that are readily available in wafer or thin-film forms, (2) the etching processes can lead to some level of roughness on the surfaces of the structures, and (3) dimensions of less than 20 nm, for other than the thickness, are difficult to obtain reliably. 

A complete review of the reported properties of ferroelectric thin films prepared by CSD is beyond the scope of this chapter. Suffice it to say that fabrication approaches from each of the three CSD categories noted above have been used to prepare high-quality films in a range of thicknesses. The dielectric response and ferroelectric hysteresis behavior have been widely reported and the reader is referred to References 12 and 13 for representative results. Despite space limitations, three aspects of CSD processing and film properties warrant consideration here. These are (i) the ability to prepare oriented films by CSD (ii) typical stress levels within the films and (iii) the general dielectric properties of the thin film materials compared to the corresponding bulk materials. 

Metal oxide nanostructures have been fabricated using different methods and preparation conditions. The most promising technique is sol-gel processing in combination with dipcoating technique.This method enables us to prepare spinel oxide thin film electrodes at ambient temperature with high level of doping and large surface area [117,118], The physical and chemical vapor deposition is another technique for metal oxide preparation [119,120],... 

As opposed to inertial sensors, micromachined anemometers are often based on micro hot plates, that is, combinations of heaters and thermometers on thermally insulating membranes or multilayered thin films [4]. Functional sensor parameters are obviously determined by thermal conductivities and heat capacities, which can be monitored to reject faulty chips. Until recently, suitable wafer-level testing methods have not been available, and most sensor designs were based on literature values, despite the fact that these values depend strongly on fabrication processing parameters. 

Elmi, I., Zampolli, S. and CardinaU, G. C. (2008a), Optimization of a wafer-level process for the fabrication of highly reproducible thin-film MOX sensors Sens. Actuators B, 131,548-55. 

Microphase separation (MPS) leading to regular patterns at nanometer levels formed by block copolymers in thin films has recently been a subject of intensive study. Such nanostructures allow for fabrication of even smaller feature sizes than those obtained by the conventional photolithography process, and have potentials for future nanofabrications (Lazzari et al., 2006). Attempts to create active and photocontrollable MPS systems are a fascinating challenge. 

An important question at the outset is that of the dependence of the SCO process, (coupled with hysteresis in the reversible spin transition) on particle size. To address this question or indeed the related one applicable where the nanoparticles are fabricated as thin films, requires convenient means of probing the SCO process, which will be sufficiently sensitive to continue to act as a viable probe over the entire range from the bulk material down to nano dimensions. Raman spectroscopy has been successfully used down to nanoscale levels of ca. 200 nm. ... 

Self-Assembly Process. The ability to readily manipulate a wide variety of electroactive polymers at the nanoscale level makes it possible to create thin film heterostructures with optical and electrical properties that can be fine-tuned at the molecular level. As indicated earlier, we have demonstrated that this process can be utilized with many different conjugated, nonconjugated and electrically conductive polymers. Any variety of complex multilayer heterostructures can be fabricated with... 

Langmuir-Blodgett (LB) technique is one of the processing techniques for the fabrication of thin films of functional materials with controlled film thickness. For the fabrication of the thin films with nano-level control of film thickness, number... 

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