Spacers Alternatives for INTEGRATION OF (3D) STACKED SBT FeCAPs

The thermal and mechanical stability of Ir and Ir\Pt metals spacers deposited on top of Ti(Al)N\Ir\IrO2 patterned structures has been investigated in pseudo 3D stacked SrBi2 Ta2O9 (SBT) capacitors. Their stability was compared to standard TEOS spacers. The high compressive stress at the edge of patterned electrodes, as a consequence of the high thermal expansion mismatch between the metals used in the electrode and TEOS, make the system mechanically unstable at the SBT crystallization conditions (700degreesC for 1 hour). The mechanical problems could be overcome if the same noble metals used in the electrode are incorporated as spacers. However, thermal stability during the SBT crystallization conditions is still an issue. For the case of Ir, surface oxidation decreases the SBT polarization values. In the case of Ir\Pt, Ir diffuses through Pt and oxidizes, leading to unstable patterned structures and to the oxidation of the Ti(Al)N layer.