Ultrathin ferroic HfO2–ZrO2 superlattice gate stack for advanced transistors

• Published in: Nature (London) Vol. 604; no. 7904; pp. 65 - 71
• Main Authors: Cheema, Suraj S., Shanker, Nirmaan, Wang, Li-Chen, Hsu, Cheng-Hsiang, Hsu, Shang-Lin, Liao, Yu-Hung, San Jose, Matthew, Gomez, Jorge, Chakraborty, Wriddhi, Li, Wenshen, Bae, Jong-Ho, Volkman, Steve K., Kwon, Daewoong, Rho, Yoonsoo, Pinelli, Gianni, Rastogi, Ravi, Pipitone, Dominick, Stull, Corey, Cook, Matthew, Tyrrell, Brian, Stoica, Vladimir A., Zhang, Zhan, Freeland, John W., Tassone, Christopher J., Mehta, Apurva, Saheli, Ghazal, Thompson, David, Suh, Dong Ik, Koo, Won-Tae, Nam, Kab-Jin, Jung, Dong Jin, Song, Woo-Bin, Lin, Chung-Hsun, Nam, Seunggeol, Heo, Jinseong, Parihar, Narendra, Grigoropoulos, Costas P., Shafer, Padraic, Fay, Patrick, Ramesh, Ramamoorthy, Mahapatra, Souvik, Ciston, Jim, Datta, Suman, Mohamed, Mohamed, Hu, Chenming, Salahuddin, Sayeef
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 07-04-2022; Nature Publishing Group
• Subjects: 140/146; 639/166/987; 639/301/1005/1007; 639/925/357/995; 639/925/927/1007; Antiferroelectricity; Capacitance; Current leakage; Electron transport; Electronic devices; Electronic equipment; Energy; Equivalence; Ferroelectric materials; Hafnium oxide; Heterostructures; Humanities and Social Sciences; Leakage current; MATERIALS SCIENCE; Metal oxide semiconductors; multidisciplinary; Multilayers; Permittivity; Phase transitions; Scavenging; Science; Science (multidisciplinary); Semiconductor devices; Silicon dioxide; Spectrum analysis; Stacks; Superlattices; Thickness; Transistors; Zirconium dioxide
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-022-04425-6

With the scaling of lateral dimensions in advanced transistors, an increased gate capacitance is desirable both to retain the control of the gate electrode over the channel and to reduce the operating voltage
1
. This led to a fundamental change in the gate stack in 2008, the incorporation of high-dielectric-constant HfO
2
 (ref. 
2
), which remains the material of choice to date. Here we report HfO
2
–ZrO
2
superlattice heterostructures as a gate stack, stabilized with mixed ferroelectric–antiferroelectric order, directly integrated onto Si transistors, and scaled down to approximately 20 ångströms, the same gate oxide thickness required for high-performance transistors. The overall equivalent oxide thickness in metal–oxide–semiconductor capacitors is equivalent to an effective SiO
2
thickness of approximately 6.5 ångströms. Such a low effective oxide thickness and the resulting large capacitance cannot be achieved in conventional HfO
2
-based high-dielectric-constant gate stacks without scavenging the interfacial SiO
2
, which has adverse effects on the electron transport and gate leakage current
3
. Accordingly, our gate stacks, which do not require such scavenging, provide substantially lower leakage current and no mobility degradation. This work demonstrates that ultrathin ferroic HfO
2
–ZrO
2
multilayers, stabilized with competing ferroelectric–antiferroelectric order in the two-nanometre-thickness regime, provide a path towards advanced gate oxide stacks in electronic devices beyond conventional HfO
2
-based high-dielectric-constant materials.
In the standard Si transistor gate stack, replacing conventional dielectric HfO
2
 with an ultrathin ferroelectric–antiferroelectric HfO
2
–ZrO
2
 heterostructure exhibiting the negative capacitance effect demonstrates ultrahigh capacitance without degradation in leakage and mobility, promising for ferroelectric integration into advanced logic technology.