Large Ferroelectric Polarization of Tin/Hf0.5Zr0.5O2/Tin Capacitors Due to Stress-Induced

[Supplementary material]

Large ferroelectric polarization of TiN/Hf0.5Zr0.5O2/TiN capacitors due to stress-induced crystallization at lowthermal budget

Si Joon Kim1,Dushyant Narayan1, Jae-Gil Lee1, Jaidah Mohan1, Joy S. Lee1,Jaebeom Lee1, Harrison S. Kim1, Young-Chul Byun1, Antonio T. Lucero1, Chadwin D. Young1, Scott R. Summerfelt2, Tamer San2, Luigi Colombo2,and Jiyoung Kim1,*

1Department of Materials Science and Engineering, The University of Texas at Dallas,

800 West Campbell Road,Richardson, Texas 75080, United States

2Texas Instruments,

13121 TI Blvd, Dallas, Texas 75243, United States

Keywords

Ferroelectric random access memory, Hf0.5Zr0.5O2,Atomic layer deposition, Stress-induced crystallization, Low thermal budget process

*Electronic mail:

For the pulse write/read measurement (see Fig. S1(a)),1a series of write and read trapezoidal voltage pulses with a pulse width of 4 μs, a rising/falling time of 1 μs, and a delay time of 10 μs were applied to the Hf0.5Zr0.5O2 (HZO)samples using a pulse generator (Agilent 81110A). The subsequent voltage drop on the internal resistor of 50Ω (shunt resistor) was measured using an oscilloscope (Tektronix DPO7104). The load current was calculated from the load voltage using Ohm's law and the load current of each pulse was integrated over time to extract the polarization. Figure S1(b) and (c) show an example of the pulse write/read result of the HZO sample according to the pulse sequence.

In the write/read sequence, the write pulse is applied such that the switching and non-switching polarization can be extracted from the read pulse. For example, applying +2.5V write pulse and -2.0V read pulse can help us extract the switching polarization at -2.0V from the read pulse. Similarly, applying -2.5V write pulse and -2.0V read pulse can help us extract the non-switching polarization at -2.0V from the read pulse. Hence, the applied write voltage was fixed at ±2.5 V and the read voltage varied from -2.5V to 2.5V with 0.1V step as shown in Fig.S1(c). It takes around 5 s to initialize the pulse generator and the oscilloscope between each write/read sequence, which gives the domains sufficient time to relax. By subtracting the integrated current values of the switching and non-switching read pulses, the real ferroelectricswitching polarization (Psw) were extracted. The slope of the integrated current values of non-switching read pulses can be also used to extract the dielectric constant of the HZO sample as shown in Fig. S1 and Fig. S2(a).

We can see two different slope regions in non-switching pulse write/read results (see Fig. S2(a) inset). Therefore, two dielectric constants in two different read voltage operation regions are extracted from non-switching pulse write/read results, respectively. The dielectric constant in the first region (when read voltage is much lower than coercive voltage) and the second region (when read voltage is coercive voltage or higher) are about 45.3 and 67.2, respectively. The dielectric constant extracted from the first region is similar to the dielectric constant obtained from the small signal capacitance-voltage (C-V) measurement at 2.5 MV/cm (higher than coercive field) where the ferroelectric switching effect is minimized (at a frequency of 10 kHz with an amplitude of 50 mV using an Agilent 4284A) as shown in Fig. S2(b). Meanwhile, the extracted dielectric constant at or above the coercive voltage is close to the maximum dielectric constant in small signal C-V measurement at the coercive voltage. These extracted values are shown in Table I of the manuscript.

[1] S. J. Kim, D. Narayan, J.-G. Lee, J. Mohan, J. S. Lee, J. Lee, C. D. Young, J. Kim, S. R. Summerfelt, T. San, and L. Colombo, in Proc. 9th IEEE International Memory Workshop (IMW), (2017).

FIG. S1. (a) Schematic diagram of pulse write/read measurement. (b) Pulse write/read result of the HZO sample annealed at 400°C after TiN TE deposition. (c) The sequence of pulse write/read measurement: for example, the write voltage was fixed at ±2.5 V and the read voltage varied (-2.0 V, -1.5 V, -0.5 V, 0.5 V, 1.5 V, and 2.0 V).

FIG. S2.The extracted dielectric constant of the HZO sample annealed at 400°C after TiN TE deposition from (a) non-switching pulse write/read result and (b) small signal C-V measurement.