IEEE ELECTRON DEVICE LETTERS, VOL. 21, NO. 4, APRIL 2000
Electrical Characteristics of Highly Reliable Ultrathin Hafnium Oxide Gate Dielectric Laegu Kang, Byoung Hun Lee, Student Member, IEEE, Wen-Jie Qi, Student Member, IEEE, Yongjoo Jeon, Student Member, IEEE, Renee Nieh, Student Member, IEEE, Sundar Gopalan, Katsunori Onishi, and Jack C. Lee, Member, IEEE
Abstract—Electrical and reliability properties of ultrathin HfO2 have been investigated. Pt electroded MOS capacitors with HfO2 gate dielectric (physical thickness – Å and equivalent oxide thickness – Å) were fabricated. HfO2 was deposited using reactive sputtering of Hf target with O2 modulation technique. Leakage current of the 45 Å HfO2 sample 4 A/cm2 at V with a breakdown field was about MV/cm. Hysteresis was 100 mV after 500 C annealing in N2 ambient and there was no significant frequency dispersion of capacitance ( %/dec.). It was also found that HfO2 exhibits negligible charge trapping and excellent TDDB characteristics with more than ten years life- time even at DD V.
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Index Terms—Gate dielectric, hafnium oxide, HfO2 . Fig. 1. Schematic diagram of oxygen modulated dc magnetron sputtering. During , only Ar gas is flown; during , both Ar and O are used.
ATE dielectric materials having high dielectric constant, low leakage current, good thermal stability, interface characteristics comparable to Si–SiO are needed as alternative to SiO as device dimensions are scaled down. However, many high- dielectric materials such as Ta O , TiO and STO are thermally unstable when in direct contact with Si . Thus, additional passivation layers, such as Si N or SiO N between high- layer and Si substrate is needed to prevent interfacial reaction , . This raises concerns regarding scalability of EOT (equivalent oxide thickness) and process complexity. On the other hand, some binary layers such as HfO , ZrO , Y O , and Al O have been shown to be thermally and chemically is the most stable oxide stable on Si –. HfO . Hf can also scavwith the highest heat of formation enge native oxide to form HfO . In spite of very promising properties as a gate dielectric, little attention has been given to HfO as a gate dielectric. In this letter, the electrical and reliability characteristics of ultrathin HfO capacitor down to Å have been investigated. an EOT of II. EXPERIMENTS Metal insulator semiconductor (MIS) capacitors with HfO dielectric were fabricated on p-type silicon wafers. Active recm were defined using patterned gions with an area of
Manuscript received September 6, 1999; revised December 21, 1999. The review of this letter was arranged by Editor D. J. Dumin. The authors are with the Microelectronics Research Center,The University of Texas at Austin, Austin, TX 78758 USA (e-mail: [email protected]
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