Hafnium oxide-based ferroelectric thin-film transistor with a-InGaZnO channel fabricated at temperatures <= 350°C

Authors

Che-Chuan Lee, National Taiwan UniversityFollow
Chun-Wei Chang, National Taiwan University
Min-Hung Lee, National Taiwan Normal University
I-Chun Cheng, National Taiwan University

Conference Dates

May 15-18, 2023

Abstract

HfO₂-based ferroelectric materials integrated with oxide-based thin-film transistors have been considered as potential candidates for back-end-of-line compatible ferroelectric field-effect transistors, which can be vertically stacked on silicon CMOS circuits to realize high-density neural network applications. However, the formation of ferroelectric orthorhombic phase in HfO₂-based materials usually requires an annealing temperature of 400°C or higher. In this work, ferroelectric thin-film transistors (Fe-TFTs) were developed by monolithically integrating HfZrO2 (HZO) ferroelectric capacitors with amorphous indium-gallium-zinc oxide (a-IGZO) TFTs at a maximum processing temperature of 350°C on a glass substrate. A butterfly-shaped C-V curve was clearly observed in the low-temperature annealed metal-HZO-metal capacitor, indicating the formation of ferroelectricity in the HZO layer, as shown in Fig. 1. The positive and negative coercive voltages were 3 V and -2.4 V, respectively. The dielectric constant was 20.65. The field-effect mobility, threshold voltage, subthreshold swing and on/off current ratio of the a-IGZO TFT extracted from the transfer characteristics shown in Fig. 2 were 6.15 cm²V^-1s^-1, 1.5 V, 0.1 V/dec and 4.3´10⁷, respectively. Fig. 3 shows the transfer hysteresis curves of the low-temperature Fe-TFTs in a metal-ferroelectric-metal-insulator-semiconductor configuration. The Fe-TFTs exhibited large hysteresis memory windows of 2.8 V and 3.8 V when the area ratios between ferroelectric capacitors and gate insulators (A_FE / A_DE) were 1/8 and 1/12, respectively. The result shows a great potential for back-end-of-line compatible memory applications.

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Recommended Citation

Che-Chuan Lee, Chun-Wei Chang, Min-Hung Lee, and I-Chun Cheng, "Hafnium oxide-based ferroelectric thin-film transistor with a-InGaZnO channel fabricated at temperatures <= 350°C" in "Semiconductor Technology for Ultra Large Scale Integrated Circuits and Thin Film Transistors (ULSIC VS TFT 8)", Y. Kuo, Texas A&M University, USA Eds, ECI Symposium Series, (2022). https://dc.engconfintl.org/ulsic_vs_tft_8/3