Process Dependent Switching Dynamics of Ferroelectric Hafnium Zirconate

The CMOS-compatible ferroelectrics (FE) based on HfO ₂ are being widely explored for emerging memory, logic, and neuromorphic devices [1]. While the applications hinge on the dynamic switching of the FE, process optimization often relies on information obtained from measurement of the quasi-static polarization-field (P-E) hysteresis loops [2]. We have recently been refining methods for characterizing the polarization reversal dynamics of polycrystalline FEs, such as Hafnium Zirconate (HZO). Because of the close agreement between the nucleation limited switching (NLS) model and measurements, detailed physical information such as minimum switching time and activation field distributions can be extracted from polarization reversal measurements vs. pulse amplitude and duration [3]. This characterization has been successfully applied to the prediction of FE switching dynamics under arbitrary voltage waveforms [4]. Here, we utilize this method to study the dependence of the switching dynamics of FE HZO formed by atomic layer deposition (ALD) vs. electrode metal and post deposition anneal temperature. Symmetrical metal/HZO/metal capacitors having 25 gm radius were fabricated by optical lithography, with sputtered 100 nm TiN and W top/bottom electrodes, 10 nm Plasma Enhanced ALD HZO at 300 °C with TDMAH and TDMAZ precursors, having post deposition anneal temperatures of 400, 500, and 600 °C for 30 sec in N2. Polarization reversal curves were obtained by applying voltage pulses to these capacitors, with pulse widths ranging from 200 ns to 1 ms, and pulse amplitudes from 0.1 V to 2.5 V, and the nonvolatile switched FE charge was measured using a unipolar double triangular waveform. The obtained curves were then fitted using the NLS model [3], which considers the FE HZO film to be comprised of many independently switching FE grains with different activation fields belonging to a distribution function. The switching time constant of each grain depends on the applied field, the activation field, and the minimum switching time constant.