Sputtering dielectric film

Insulator sputtering is similar to the process described for metal sputtering. The only difference is that the source target is a dielectric film. There is less control of the chemical nature and quaUty of the film as compared to a CVD deposited film. Common sputtered films include siUcon nitride and sihcon oxide. 

Figure 4.10. Representative og(IB)-VGS behavior of an RF-sputtered ZTO-channel TFT on (a) 40-nm A1PO and (b) 100-nm Si02 gate dielectrics on unpatterned p++ Si gate electrodes. Channel and A1 S/D contacts were defined with shadow masks. Dielectric films were annealed at 600 °C prior to channel deposition, whereas the completed stack was annealed at 300 °C. 

The Penn State group has employed an ion-beam sputter process for silicon dioxide. This process deposits a dielectric film at low temperatures (80 °C) and is suitable for deposition on glass and flexible substrates [2, 29, 30]. With this ion-... 

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. 

Anodization is an intriguing approach to generating controlled thickness dielectric films. Sputtering the metals onto flexible substrates opens up the possibility of flexible devices. Anodization is a low-temperature process that occurs in aqueous solution, which suggests potentially easy processing methods. 

For films produced by evaporative techniques, it is approximately true that with metal films deposited on a substrate at room temperature and even higher, tensile stresses are predominant. The magnitude of the tensile stresses is between 108 and 10 dyn cm 2. Films of high-melting metals have the larger values, those of lower melting metals the smaller values in this range. Reactively sputter deposited dielectric films and metal films modified by chemical and/or physical gas incorporation frequently have compressive stresses. Compared with metal films, dielectric films often have smaller stress values. 

The scheme of such a metal-arch capacitance transducer is shown in Fig. 50. The transducer is about 3 mm thick and has a diameter between 6 and 10 mm. The fixed electrode consists of a sputtered tantalum film on a glass substrate, the dielectric is a reactively sputtered tantalum pentoxide film, and the variable electrode consists of phosphor bronze and is either an arch shaped 15 pm thin foil obtained from a metal strip or a spherical dome shaped foil made by sputtering [245]. A maximum capacitance value of 340 pF could be obtained and short time and long time stability s were better than 0.2 pF min 1 and 0.05 pF hour 1 respectively. The sensitivity of such transducers was between 2000 and 8000 pF mm 1. Q factors have been obtained in... 

Fractal dimensions of some non-living and living systems including crystallization patterns, electro-deposited aggregates, polymers, chemical dissolution patterns, dielectric breakdown, sputter deposited film of NbGcj, retinal vessel and bacterial growth are given in Table 13.3. 

Various multilayer dielectric films are commonly used in microelectronics, including, for example, combination oxides Si3N4-Si02. Combination oxides, which consist of a thin thermal Si02 layer (to achieve interface properties equivalent to thermal Si02> followed by sputtered bulk oxide (produced at low temperatures), were studied by IR spectroscopy [294]. The peak position and the FWHM of the stretching mode of combination oxides only differ by 6-8 cm from those of dry thermal oxides. This minor deviation indicates that the combination oxides and thermal ones have a comparable stoichiometry. 

Bennett, X., Beebe, M., Sparks, C., Gondran, C., Vandervorst, W. (2004) Sputter rate variations in silicon under high-k dielectric films. Applied Surface Science, 257-252,565-568. 

The absorption of water by polymers is especially suited to the development of a capacitive humidity sensor based on the high dielectric constant of water, since capacitance depends on the area, the thickness, and the dielectric constant of a dielectric. Uptake of water causes an increase in the dielectric constant followed by an increase in capacitance. Polyimide is a suitable sensitive material, but so are certain inorganic ceramics such as AI2O3 [142] and low-density Ta205, which change their capacitance with the formation of water dipoles. Low-density Ta20s layers can be formed by anodic oxidation of sputtered tantalum films, whereas polyimide films are deposited by spin coating and subsequent polymerization. 

The suppression of arcs generated in the dc discharge (arc suppression) is important to obtaining stable performance of the dc power supply, particularly when reactively sputter depositing dielectric films. Arcing can occur any time a hot (thermoelectron-emitting) spot is formed or when surface charging is different over surfaces in contact with the plasma. 

Baumann, R., Rost, T., Stone, B. and Rabson, T., Characterisation of sputtered thin films of barium strontium titanate on silicon substrates, presented at 1st European Conference on Applications of Polar Dielectrics/Intemational Symposium on Applications of Ferroelectrics, Zurich, Switzerland, August 2 h-September 1st, 19B8. 

Dielectric Deposition Systems. The most common techniques used for dielectric deposition include chemical vapor deposition (CVD), sputtering, and spin-on films. In a CVD system thermal or plasma energy is used to decompose source molecules on the semiconductor surface (189). In plasma-enhanced CVD (PECVD), typical source gases include silane, SiH, and nitrous oxide, N2O, for deposition of siUcon nitride. The most common CVD films used are siUcon dioxide, siUcon nitride, and siUcon oxynitrides. 

Figure 4.9. Log(/D)-VGS (VDS = 20V) and (inset) /D Vds characteristics for an RF-sputtered ZnO TFT on a spin-coated A1PO dielectric annealed at 300 °C. VGS is stepped from 0 to 40V in 5-V increments for the ID-VDS curves device W/L = 5 L = 100 pm. [Reproduced with permission. Meyers, S. T. Anderson, J. T. Hong, D. Hung, C. M. Wager, J. F. Keszler, D. A. 2007. Solution processed aluminum oxide phosphate thin-film dielectrics. Chem. Mater. 19 4023-4029. Copyright 2007 American Chemical Society.]...

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