Switching Dynamics Measurement of Ferroelectric Y-Doped HfO2 M-I-M Capacitor

Abstract

Domain-switching kinetics of 5 mol% Y-doped HfO2 metal-insulator-metal (MIM) capacitor was characterized. The changes in polarization indicate the polarization reversal in HfO2. In this research, we show the polarization reversal of an 20-nm-thick Y-doped HfO2 deposited by atomic layer deposition (ALD) by switching the applied voltage (2.6 to 4.6V) and the pulse duration (1μs to 500μs). We use the measurements of Kolmogorov-Avrami-Ishibashi (KAI) model to extract the minimum switching time of the domains. Introduction Ferroelectric HfO2 layer has attracted attraction in CMOS and memory applications owing to its scaling ability and process compatibility. It has been demonstrated that doping of foreign elements, including Zr, Si, Al, Y, atoms under post-deposition annealing (PDA) or post-metallization annealing (PMA) induces the ferroelectricity in HfO2 [1]. The switching dynamics of ferroelectric Al- and Zr-doped HfO2 metal-insulator-metal (MIM) capacitors has been well-modeled by nucleation limited switching (NLS) model, where multigrain polarization takes place assuming a distribution in the switching time [2, 3]. In this study, we apply the KAI model to fit the switching dynamics of Y-doped HfO2 MIM capacitor using the following equation,, △P=Ps*(1-exp{-(t/τ)β })where △P, P s, τ and β are the partial, saturation polarization, switching time constant and a fitting parameter, respectively [4]. Experiments An MIM capacitor with a 20-nm-thick 5 mol% Y-doped HfO2 film was fabricated by atomic layer deposition (ALD). The top and bottom electrode were both W deposited by sputtering. PMA was then carried out at 500 oC for 1 minute. Typical polarization-voltage (P-V) hysteresis is shown in fig. 1, where a remanent polarization (P r) of 12 mC/cm2 was obtained. A voltage waveform shown in fig. 2 was applied to the electrode to measure the polarization reversal of the devices after certain polling process. Polarization reversal was extracted by applying pulses with various height ranging from 2.6 to 4.6 V and width from 1 ms to 500 ms followed by half P-V measurement. Results and discussions Fig 3 shows measured partial polarization with different pulse width and voltage. As the pulse width increases, △P increases, indicating that a certain time is required to fully switch the domains. Data fit using the KAI model has well reproduced the measured data, indicating the presence of multigrain switching. However, a β of 0.6 to 0.8, which is smaller than those of Zr-doped HfO2 (typically b=2.1), needs to be used to fit the data. This may imply the difference in the domain size among dopants incorporated in the HfO2 layer. Conclusion Switching dynamics of ferroelectric Y-doped HfO2 MIM capacitors has been measured. The device has shown to follow the multidomain switching based on KAI model as is explained for Zr-doped HfO2 ones, except for the difference in the fitting parameter.