Abstract
Ferroelectric capacitors made by lead zirconate titanate (PZT) thin films and iridium electrodes are fabricated on three-dimensional structures and their properties are investigated. The iridium films are grown by Plasma Enhanced MOCVD at 300°C, while the PZT films are deposited by thermal MOCVD at different process temperatures between 450°C and 550°C. The step coverage and composition uniformity of the PZT films on trench holes and lines are investigated. Phase separation of PZT films has been observed on both 3D and planar structures. No clear dependences of the crystallization and composition of PZT on 3D structure topography have been found. STEM EDX line scans show a uniform Zr/(Zr+Ti) concentration ratio along the 3D profile but the variation of the Pb/(Zr+Ti) concentration ratio is large because of the phase separation. 3D ferroelectric capacitors show good ferroelectric properties but have much higher leakage currents than 2D ferroelectric capacitors. Nevertheless, during cycling tests the degradation of the remnant polarization between 2D and 3D capacitors is similar after 109 switching cycles. In addition, the sidewalls and bottoms of the 3D structures seem to have comparable remnant polarizations with the horizontal top surfaces.
Highlights
Scientists and engineers are always looking for a universal memory device
Ferroelectric capacitors made by lead zirconate titanate (PZT) thin films and iridium electrodes are fabricated on three-dimensional structures and their properties are investigated
The iridium films are grown by Plasma Enhanced MOCVD at 300◦C, while the PZT films are deposited by thermal MOCVD at different process temperatures between 450◦C and 550◦C
Summary
Scientists and engineers are always looking for a universal memory device. It must be nonvolatile and must have low power consumption, high speed, good reliability, high storage density and low cost. Ferroelectric capacitors constructed by Ir/PZT/Ir thin film stacks were made on three-dimensional structures and their properties were investigated. Two different 3D structures (named as 3DA and 3DB) were patterned as parallel trench lines of 1 μm (width & distance) and 2 μm respectively with 1 μm depth They were fabricated as two individual dies on the substrates side by side next to one additional die (named as 2D) with a blank area. All three dies were processed together simultaneously in order to analyze the difference between 2D and 3D capacitors Their Ir bottom electrodes and PZT ferroelectric films were deposited using the same methods and process conditions as mentioned above. At the corners of samples, small area of the PZT film is etched off with a chemical solution in order to provide electrical contact to the bottom electrode
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