Direct-contact ferroelectric capacitors for memory applications

The manufacturing of high-density ferroelectric memories or DRAM memories with high-dielectric constant materials in sub-micron IC processes demands for a technology where the capacitor is directly contacted from below to the access transistor. In this paper such a technology, based on a sub-micron IC process with planarization and tungsten plugs, is described. The risk of deterioration of the CMOS circuitry (in particular the oxidation of contacts) is successfully prevented by using a Ru/RuPt bottom electrode for the ferroelectric capacitors. With this electrode no increase of contact resistances nor degradation of CMOS characteristics are found after the ferroelectric processing, using a PbZrxT1-xO3 film deposited by organometallic chemical vapour deposition at 700 degrees C. The properties of direct-contact capacitors are good.