Effect of the metal electrode on the characteristics of Ta2O5 capacitors for DRAM applications

The effect of various electrodes (Al, W, TiN) deposited by evaporation (Al) and sputtering (W, TiN) on the electrical characteristics of thermal Ta2O5 capacitors has been investigated. The leakage currents, breakdown fields, mechanism of conductivity and dielectric constant are discussed in the terms of possible reactions between Ta2O5 and electrode material as well as electrode deposition process-induced defects acting as electrically active centers. During deposition of TiN and Al a reaction that worsens the properties of Ta2O5 occurs while there is not an indication for detectable reduction of Ta2O5 when top electrode is W. The sputtered W top electrode is a good candidate as a top electrode of storage capacitors in DRAMs, but sputtering technique is less suitable for deposition of TiN due to the introduction of radiation defects causing deterioration of leak-age current.