Synthesis and characterization of TiO2 films for deep trench capacitor applications

Traditionally, DRAM storage capacitors have employed silicon dioxide, silicon nitride, or a combination of both as the capacitor dielectric. With the advent of smaller structures however, gains in capacitance made via the utilization of thinner films and/or enhanced-surface-area-structures are offset by increased leakage current or added processing complexity. In an effort to maintain capacitance as the ground rules shrink, work has been conducted on the synthesis and integration of titanium dioxide films into deep trench capacitors. For this investigation, films between 150 and 300 Å thick have been synthesized via the high temperature oxidation of titanium nitride at temperatures between 600 to 900°C. Microstructural and electrical characterization has been performed on both blanket films and deep trench structures. Results show the films to be polycrystalline-rutile with a dielectric constant of about 30. Leakage current densities measured at 1 V were found to increase from values on the order of 10 ^-8 A/cm² as grown to 10^-6 A/cm² upon annealing at 1050°C for 3 minutes in inert ambient. TEM/SEM analyses have illustrated the step coverage of the deposition technique and results indicate film conformality to be better than 90%