Fabrication and characterization of zirconium oxide thin films
Zirconium oxide (ZrO2) is an important material with a potential for a wide range of technological applications. The outstanding chemical stability, electrical and mechanical properties, high dielectric constant, and wide band gap of ZrO2 make it suitable for several industrial applications in the field of optics, electronics, magneto-electronics, and optoelectronics. ZrO2 is frequently used as a high refractive index material in multilayer optical coatings in high power laser systems. ZrO2 is employed in super plastic structural ceramics that demonstrate excellent strength and fracture toughness. ZrO2 has been considered as a promising dielectric to replace SiO2 in advanced metal oxide semiconductor (MOS) devices in gate stack. In addition, ZrO2 exhibits functionality in the ultraviolet regions of the electromagnetic spectrum. If the properties can be tuned, it can become a useful candidate for all applications in the desired regions of the electromagnetic spectrum. However, it is well known that the electrical and optical properties of ZrO2 thin films are highly dependent on the film-substrate interface structure, morphology, and chemistry, which are in turn controlled by the film-fabrication technique, growth conditions, and post-deposition processes. The goal of present work is to grow and demonstrate the high quality of ZrO2 thin films for application in electronic and optoelectronic devices. The specific objectives of the work are: (1) grow ZrO2 films under varying growth conditions using radio frequency (RF) magnetron sputtering, (2) gain a better understanding of the growth and local structure, interface structure and chemical reactions at the ZrO2-Si interface for ZrO2 films grown on Si (100) substrates, (3) study the material properties and (4) optimize the conditions to produce high quality ZrO 2. In the present work, ZrO2 thin films have been prepared by the radio-frequency magnetron sputter-deposition onto Si (100) substrates as a function of growth temperature (Ts) varied in a wide range of 30-400°C. The growth behavior, surface structure, morphological features, interface structure, and chemical analysis of surfaces and interfaces have been examined by the high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning electron microscopy (HR-SEM). The crystal structure and interface analysis have been performed using x-ray diffraction (XRD) and x-ray reflectivity (XRR). The optical and electrical properties were evaluated by studying the optical absorption and capacitance-voltage measurements, respectively. The results indicate that the effect of Ts on the surface structure, interface layers and morphology of ZrO2 films is significant. ZrO2 films grown at 30°C are nanocrystalline without an interface layer (IL) formation. An increase in Ts results in the improvement in the crystallinity of ZrO2 films. The grain sizes determined were in the range 5-40 nm, where the temperature-dependence is clear. Similarly, it was found that the effect of Ts is significant on the optical band gap and dielectric constant of ZrO2 films. Efforts are made to explain the quantitative information, obtained based on the electron microscopy results, making use of the existing models to account for growth behavior and interface structure.
Electrical engineering|Materials science
Vemuri, Venkata Rama Sesha Ravi Kumar, "Fabrication and characterization of zirconium oxide thin films" (2009). ETD Collection for University of Texas, El Paso. AAI1473899.