| The perovskite Strontium-Titanate (SrTiO3 or ST) and Barium-Strontium-Titanate ((Ba,Sr)TiO3 or BST) thin films with high permittivity (K∼200–300) are potential candidates for storage elements in gigabit Dynamic Random Access Memories (DRAMs), tunable dielectrics in communication devices, and embedded passive components in mixed-mode microelectronic packages. To date, attempts to develop a robust metal-organic chemical vapor deposition (MOCVD) process that produces device-quality films have been limited by the lack of understanding in the processing-structure-property interrelationships. This work addresses the critical MOCVD process issues that control the nanostructure and hence, the properties of polycrystalline high K films (sub-300 Å). The specific objectives of this research were: (a) to understand and control the nanostructure evolution in these films, (b) to understand the effects of macroloading and microloading on step coverage, and (c) to understand the nanostructure evolution and dielectric and electrical behavior in as-deposited, amorphous films that have undergone rapid thermal annealing (RTA). Additionally, thermodynamic phase stability diagrams were calculated to provide for the process development of very high K (∼1000) films.; Initially, from nanostructure analysis, a preliminary growth mechanism and an alternative but plausible origin of roughness of BST by MOCVD were forwarded. Also, the Curie-Weiss behavior in 275 Å BST films, exhibiting a dieletric anamoly at ∼37°C, was explained in terms of the in-plane biaxial stress, incommensuration, cation ratio, and grain size. Next, the electrical properties of as-deposited, amorphous BST films (220–880 Å) that have undergone RTA were modelled [series combination of an interfacial K (45) and a bulk K (369)] and qualitatively compared with the properties of as-deposited, crystalline BST films.; The effects of deposition temperature and nature of Pt-passivated Si substrate on the site for nucleation, nucleation density, grain size, and orientation of SrTiO3 were observed by various analytical techniques. By understanding the nucleation and growth phenomena, optimal properties (C/A and loss tangent of ∼83 fF/μm2 and 0.003, respectively) of SrTiO3 films were illustrated.; The structure evolution and conformality (100–0%) of ST by MOCVD in three-dimensional topographies as functions of the deposition temperature, nature of the patterned substrate surface (TiN coated SiO2/Si Vs bare SiO2/Si), and pattern geometry and density (i.e., aspect ratio and pitch) were observed and discussed in terms of the existing mechanisms. Finally, the thermodynamic phase stability diagrams were calculated for the very high K Pb-Ba-Zr-O system. In future MOCVD studies, this information may be used for the design of experiments to control both the cost and time of development. |
