Thin Film Dielectrics for Electronics Using Combustion Chemical Vapor Deposition
- PDF / 3,284,571 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 50 Downloads / 226 Views
Mat. Res. Soc. Symp. Proc. Vol. 574 ©1999 Materials Research Society
switched using regular integrated circuit voltages. In DRAM storage cells, higher permittivity dielectric materials reduce individual capacitor dimension and therefore, a larger number of capacitors can be built in a given chip and/or more area is available for integration with other devices. As a result, the device density is higher and the speed to access the modules is increased. High temperature superconductors (HTSC) are also of great interest for electric power applications such as current leads, motors, transmission cables, generators, transformers and current limiters. Prior to depositing these high temperature superconductors, dielectric materials such as CeO 2 have to be coated, followed by YSZ to function as buffer layers. Processes amenable to scale-up that will facilitate the buffer layer deposition at a low cost with good stoichiometry and improved texture control are, thus, required for high volume, low-cost manufacturing of HTSC wires. To meet the increasing needs of depositing high-quality, complex oxide thin films, the recently patented Combustion Chemical Vapor Deposition (CCVD) process [5-7] was utilized. The key advantage of this technology is its ability to use inexpensive chemical reagents to vapor deposit films in open atmosphere without an expensive furnace, vacuum, or reaction chamber and thus, enables deposition for continuous, production-line manufacturing. Consequently, CCVD's throughput potential is expected to be greater than conventional vacuum coating technologies that are restricted to batch processing. This paper reviews our work on ferroelectric thin films and superconductor buffer layers, using the CCVD process. EXPERIMENT In the CCVD process (Figure 1), precursors were dissolved in a solvent which typically also acted as combustible fuel. The solution was atomized to form submicron droplets by means of a patent-pending technology. An oxygen stream then carried the fine mist of the precursor droplets to a flame where they were combusted. The heat from the flame provided the energy required to evaporate the droplets and for the precursors to react. The vapor was then deposited on substrate by drawing it over the steady-state flame plasma. Doping and stoichiometry were controlled by adjusting concentrations and constituents of the precursor solution.
Meter
Vaporizer
Flow
e , :JjPLC.. . •!•....Filter •
Substrate
Intine
Precursor
Solution
Figure 1. Schematic representation of the CCVD. All films in this work were deposited, using appropriate concentrations of low-cost precursors, such as acetylacetonates and 2-ethylhexanoates, in organic solvents. For wireless communication, BST and SrTiO 3 coatings were coated on (100) MgO single crystals. Deposition time ranged between 30-60 min at gas temperatures of 8000-1 100 0 C. (Substrate temperature is always lower than the gas temperature.) Substrates were ultrasonically cleaned
372
in toluene and rinsed with isopropanol prior to use. The ferroelectric films
Data Loading...
