In Situ Ellipsometry Analysis on Formation Process of Al[sub 2]O[sub 3]-Ta[sub 2]O[sub 5] Films in Ion Beam Sputter Deposition

Abstract

Al 2 O 3 -Ta 2 O 5 thin films are known as highly corrosion-resistant materials for coatings. Here the formation process of Al 2 O 3 -Ta 2 O 5 films was analyzed by in situ ellipsometry during deposition by ion beam sputtering. Composite targets composed of Al 2 O 3 and Ta 2 O 5 plates were used for sputter deposition. During deposition, the formation process of thin films was monitored by a single-wavelength rotating analyzer ellipsometer attached to the sputtering system. The composition, the chemical binding states of constituent elements, and the depth profile of the elements of the films were analyzed by inductively coupled plasma-atomic emission spectroscopy, X-ray photoelectron spectroscopy ͑XPS͒, and auger-electron spectroscopy ͑AES͒, respectively. Ellipsometric analysis showed that the thickness of the film increased linearly with time after short induction periods. The refractive index of the films increases with increasing tantalum cationic fraction. The extinction coefficient of the films was larger than those of single Al 2 O 3 and Ta 2 O 5 films. The XPS analysis showed that the preferential deposition of the Ta 2 O 5 component occurred in the induction period and the codeposition of Ta 2 O 5 and Al 2 O 3 in the linear growth stage. The AES analysis showed that the content of constituent elements was homogeneous from the top to the bottom of the films in the linear growth stage.In ion beam sputter deposition ͑IBSD͒, 1,2 target materials are sputtered by inert gas ions, such as Ar + ions, from an ion gun, and sputtered particles are deposited on a substrate to form a film. Advantages of IBSD are that the film is scarcely irradiated by highenergy particles generated in a plasma area and is formed under relatively high vacuum. Because of these advantages, the film formed is free from irradiation damages and absorption of process gas. Consequently, IBSD is widely used for the formation of highquality metal, alloy, or oxide thin films. 3-10 However, most research has been engaged with characteristics of the films; a very few research projects have been concerned with the formation process of the films.Ellipsometry is a sensitive method for analyzing changes in the thickness and optical constant of surface films. It provides nondestructive optical measurements in a vacuum, gases, and solutions. Because of these features, ellipsometry has been used for in situ analysis of the oxidation and reduction processes of metals and alloys in aqueous solutions, 10-17 the formation process of oxide films by chemical vapor deposition, [18][19][20][21][22] and that of metal, oxide, nitride, and carbide films by physical vapor deposition. [23][24][25][26][27][28][29][30] Several reports are available for ellipsometric analyses of the formation process of thin films by magnetron sputtering. Aouadi et al. 23 analyzed the formation of Inconel/carbon multilayer films on a Si substrate. Lee et al. 24,25 studied the initial stage of growth of Au thin films on heat-oxidized Si substrates. Vergohl et al. 26 reported the process...

Comparison of different methods for measuring the passive film thickness on metals

“…For this reason, several techniques have been employed to accurately measure the film oxide thickness on different metals. Those techniques are mainly based on either optical (ellipsometry) [2,3,4], electronic (X-ray photoelectron spectroscopy (XPS)) [5,6] or electric (electrochemical impedance spectroscopy (EIS)) [7,8] properties. Among them, EIS is a widely used technique, which allows investigation of different processes at the electrode/electrolyte interface [9].…”

Performance and Stability of Low Temperature Transparent Thin-Film Transistors Using Amorphous Multicomponent Dielectrics

“…Sputtered Ta 2 O 5 , which has been extensively used as a dielectric in organic TFTs, 30,31 is selected here as a starting high-material essentially due to its relatively high sputtering rate even with low power density, which results in high throughput and low damage to the growing film and its interfaces. The combination of Ta 2 O 5 with SiO 2 or Al 2 O 3 has been found to be useful for applications such as optical filters and corrosion-resistant coatings, [32][33][34] but in most cases, the materials are grown as multilayer structures rather than as single multicomponent layers. However, for a transistor's insulator, multicomponent layers ͑or alternatively multiple layers of multicomponent materials͒ are preferable because binary oxides often have a tendency to crystallize even at low ͑post͒processing temperatures.…”

Hydrogen Gas Sensor Using Pt- and Pd-Added Anodic TiO[sub 2] Nanotube Films

“…Preparation of Ti alloy thin films by ion-beam-sputter deposition.-To fabricate hydrogen sensors composed of noble-metaladded TiO 2 nanotubes, Pt-Ti and Pd-Ti alloy thin films were used as a starting material for anodization. These thin films were sputter deposited on glass slide substrates ͑15 ϫ 26 mm͒ by an ion-beamsputter deposition ͑IBSD͒ system 29 ͑Tokyo Denshiyakin, DIBS-3000HC, TDY-0395͒ equipped with a Kaufman-type ion source ͑Ion Tech, model 3.0-1500-100 FHC͒. Figure 1 shows a schematic illustration of the IBSD system and the arrangement of a complex target used for the deposition of Ti alloy thin films with different compositions.…”