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The effects of post-annealing on the properties of Ru films formed by metalorganic chemical vapor deposition were investigated, aiming to the application to the bottom electrode of ferroelectric capacitors. Ruthenium films were deposited at a temperature of 350°C using a liquid-type source of Ru[EtCp]2 without introducing O2. Post-annealing was performed in vacuum at a temperature of 400°C. Surface morphology and crystallinity of Ru were very similar between as-deposited and post-annealed Ru films. In addition, the Pt/BLT/Ru structure exhibits similar polarization hysteresis loops regardless of the annealing duration. However, leakage current density was drastically decreased as the annealing duration was increased. It is presumed from the thermal desorption spectroscopy that decrease of out-diffused gas from Ru film by post-annealing is a main reason for the improvement of leakage current characteristics.

Ruthenium films formed by metalorganic chemical vapor deposition were investigated, taking account of the application to the bottom electrode of ferroelectric capacitors. Ruthenium films were deposited using a liquid-type source of Ru[EtCp]2 in a cold-wall type reactor with infrared lamps. A smooth and flat Ru film was successfully formed on a SiO2-covered Si substrate without a seed layer. As the deposition temperature increased to 400°C, the crystallinity of the Ru film improved and the film exhibited high c-axis orientation. After forming a Bi4 − x La x Ti3O12 (BLT) film by a sol-gel technique, a Pt/BLT/Ru capacitor was fabricated on the Ru film. Good hysteresis loops with 2P r = 20 μC/cm2 and 2V c = 3.4 V were successfully obtained and the ferroelectric property did not depend on the deposition temperature of Ru in the temperature range from 325°C to 400°C. On the contrary, the leakage current density was significantly suppressed down to 1/100 as the deposition temperature of Ru increased from 325°C t...

Microstructures (texture and grain size) dependence of PZT thin films on the oxidation state of lead, heating rate of crystallization annealing, and the quality of bottom electrode was discussed. The spatial variations of the switching charge for a PZT capacitor is mainly determined by the texture of PZT thin film. Switching charge variation less than ±2% is achieved by making a film highly [111] textured.

Degradation of ferroelectricity in PZT (Pb(Zr0.52, Ti0.48)O3) thin-film capacitors caused by heat treatment in a reductive ambience is investigated. We have found that the degradation of ferroelectricity depends upon the metal used for the top electrode of the PZT capacitor. The increased degradation in the case of a PZT capacitor with Pt electrodes can be explained by a catalytic reaction on the Pt surface. With the use of an IrO2 non-catalytic top electrode, we have made the ferroelectricity of an IrO2/PZT/Pt capacitor retained even after the H2 annealing at 400°C, or above. This IrO2/PZT/Pt capacitor is a useful structure to avoid H2 damage in actual LSI fabrication processes.

A one-mask-patterned ferroelectric capacitor memory cell structures designed with a 0.5-μm feature size were fabricated. Oxygen plasma treatment after dry etching decreased the leakage current to as low as as-deposited film. The one-mask-patterned ferroelectric capacitors with switching charge almost equal to as-deposited film were achieved. Ferroelectric memories as dense as dynamic random access memories will become possible with this technology.

The mechanism of TiN barrier metal oxidation of Pt/TiN electrodes are investigated for planarized stacked memory utilizing lead zirconate titanate (PZT). Thinner (