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We describe the formation of ultrathin tantalum oxide capacitors, using rapid thermal nitridation of the storage-node polycrystalline-silicon surface prior to low pressure chemical vapor deposition of tantalum oxide. The amorphous tantalum oxide film is deposited on the nitrided polysilicon surface using penta-ethoxy-tantalum [Ta(OC 2 H 5 ) 5 ] and oxygen (O 2 ) gas mixture at 410 o C. The films are annealed at 600-900 o C in dry O 2 . Densification of the as-deposited film by annealing in dry O 2 is indispensable to the formation of highly reliable ultrathin tantalum oxide capacitors. During this densification, CH 4 and H 2 O desorb from the as-deposited film, and the film crystallizes into an orthorhombic structure

The systematic decrease in charge per unit weight (CV/g) in electrolytic tantalum capacitors as a function of decreasing anodization voltage is explored from both experimental and theoretical viewpoints for a range of tantalum particle sizes. Analysis by transmission electron microscopy shows that a native thermal oxide about 3.3 nm in thickness is present on the tantalum surface before anodization and that the thickness is independent of tantalum particle size. Studies in which the initial oxide thickness is altered via a preanodization heat-treatment show that the anodic oxide thickness becomes independent of the initial thermal oxide thickness once its thickness is exceeded. A theoretical model based on a cylindrical geometry explains the loss in the CV/g with decreasing anodization voltage and attributes the behavior to the 3.3 nm oxide thickness corresponding to zero anodization voltage.

A combination of structural and electrical characterization techniques was applied to polymer Ta capacitors with in situ and prepolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) cathodes with a broad range of Ta 2 O 5 dielectric thicknesses. The in situ PEDOT was produced by polymerizing the EDOT monomer using an oxidizer/dopant. The prepolymerized material was an aqueous suspension of doped polymer which was dried to produce the PEDOT film. Experimental data show that polymer Ta capacitors with prepolymerized PEDOT have lower dc leakage and higher breakdown voltage (BDV) compared to polymer Ta capacitors with in situ PEDOT. The difference in dc leakage and BDV between these two types of capacitors becomes greater with increasing thickness and improved structure of the Ta 2 O 5 dielectric film. These experimental results are inconsistent with current theories presented in the literature. An alternative model is presented based on classical metal/insulator/semiconductor (MIS) theory, where in this case M corresponds to the Ta metal, I corresponds to the Ta 2 O 5 insulator, and S corresponds to the semiconducting PEDOT. According to this model, a potential barrier for the current carriers at the insulator/semiconductor interface controls the current flow through the Ta 2 O 5 dielectric under normal operating conditions (positive polarity on the Ta anode and a temperature range of ―55°C ≤ T ≤ 105°C). In situ polymerization of the PEDOT adversely affects this barrier, while the prepolymerized PEDOT suspension leaves it essentially intact. The different migratory ability of the dopants in in situ and prepolymerized PEDOT also contributes to the differences in electrical performance of polymer Ta capacitors with in situ and prepolymerized PEDOT cathodes.

Physical and electrical properties of hafnium-doped tantalum oxide thin films were studied. The doping process affects the structures, composition, thickness, dielectric constant, charges, and leakage current density of both the bulk film and the interface layer. Compared with the undoped film, the lightly doped film exhibited improved dielectric properties, such as a higher dielectric constant, a smaller fixed charge density, a larger dielectric strength, and a lower leakage current. The postdeposition annealing process condition, such as temperature and time, also influences the high-k film's dielectric properties. In summary, the hafnium-doped tantalum oxide film is a promising high-k gate dielectric material for future metal-oxide-semiconductor devices.

This work investigates in the first place, the improvement in leakage current and breakdown field of the copper metal-insulator-semiconductor (Cu-MIS) capacitor with a plasma-enhanced chemical vapor deposited (PECVD) amorphous silicon oxycarbide (α-SiCO, k = 3.7) dielectric barrier. This is followed by investigating the improvement in leakage current and breakdown field of the Cu-comb capacitor with a carbon-doped low-k PECVD organosilicate glass (k = 3) as the intermetal dielectric and an α-SiCO dielectric film as the Cu cap barrier. The leakage current and breakdown field of Cu-MIS and Cu-comb capacitors are dependent on the species of the dielectric barrier. The Cu-MIS and Cu-comb capacitors with an α-SiCO dielectric barrier exhibit a leakage current at least three orders of magnitude smaller than those with an amorphous silicon carbide (α-SiC, k = 4.4) dielectric barrier at an applied electric field of 1.6 MV/cm between 25 and 250°C. Moreover, the breakdown field of the Cu-MIS and Cu-comb capacitors with an α-SiCO dielectric barrier, measured at 200°C, are 60 and 25%, respectively, higher than that of the capacitors with an α-SiC barrier. The decreased leakage current and increased breakdown field of the Cu-MIS and Cu-comb capacitors with an α-SiCO dielectric barrier are attributed to the higher density, oxygen-improved film property, non-semiconductor behavior, and lower fringe- or surface-electric field of the α-SiCO dielectric film.

The density of anodically formed thin films on sputtered tantalum has been measured in situ. The method used is the measurement of the average density of the assemblage tantalum‐tantalum oxide and subsequent separation of the contributions of each component to this measured density. From a knowledge of the stoichiometry of the reaction, both the thickness and the angstrom per volt values (thickness of oxide formed per volt) can be determined for the oxide. Application of the capacitance formula for a parallelplate capacitor leads to a value for η. The values obtained are: Density; ; anodization constant, ; dielectric constant, at 1 kcps.

Starting with the known but unexplained fact that high‐voltage electrolytic capacitors need operating electrolytes of high resistivity, breakdown (sparking) voltages of aluminum and tantalum anodes have been examined. If interfering side reactions are eliminated, breakdown voltage increases linearly with the logarithm of electrolyte resistivity and is insensitive to variations in electrolyte composition and to changes in temperature between 65°C and 95°C.