This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE TRANSACTIONS ON ELECTRON DEVICES 1 The Demonstration of High-Performance Multilayer BaTiO 3 /BiFeO 3 Stack MIM Capacitors Chin Lien , Cho-Fan Hsieh, Hung-Sen Wu, Teng-Chun Wu, Syu-Jhih Wei, Yu-Heng Chu, Ming-Han Liao , and Min-Hung Lee Abstract — Multilayer BaTiO 3 /BiFeO 3 (BTO/BFO) stack structures were prepared on the Pt/TiO 2 /SiO 2 /Si (100) sub- strate via highly accurate magnetron sputtering process. The cubic to the tetragonal phase transition of BTO was confirmed by both the X-ray diffraction and Raman spectroscopy after the process of rapid thermal anneal. An ∼74.1% increase of the relative permittivity was observed with the increasing thickness of BFO in the metal–insulator–metal capacitor. On the other hand, we also demonstrate that the leakage current density and the relative permittivity are found to have 20–50 times reduction and 26.6% improvement, respectively, with the additional cap of the BTO layer. Index Terms— Barium titanate (BaTiO 3 , BTO), bismuth ferrite (BiFeO 3 , BFO), metal–insulator–metal (MIM) capaci- tor, multilayer stack, rapid thermal anneal (RTA). I. I NTRODUCTION C APACITORS are widely used in portable, power, and radio frequency (RF) electronics [1], [2]. Especially a metal–insulator–metal (MIM) capacitor has become popular because the metal electrodes provide depletion free and high conductance nature, which are suitable for the high-speed application. With the development of the scaling technology, the requirements of MIM capacitors such as high capacitance density with low-leakage current and good compatibility of the miniaturizing circuit design should be met. In the past decades, many scientists focused on developing high-k dielectrics such as Al 2 O 3 [3], [4], Ta 2 O 5 [5], [6], ZrO 2 [7], and HfO 2 [8], [9] Manuscript received July 26, 2018; accepted September 1, 2018. This work was supported in part by the Department of Industrial Technology, Ministry of Economic Affairs, Taiwan, in part by the Department of Mechanical Engineering, National Taiwan University, and in part by the National Device Laboratory supports the device fabrication and measurement. The review of this paper was arranged by Editor B. Kaczer. (Corresponding authors: Chin Lien; Ming-Han Liao.) C. Lien, C.-F. Hsieh, H.-S. Wu, and T.-C. Wu are with the Center of Measurement Standards, Industrial Technology Research Institute, Hsinchu 31040, Taiwan (e-mail: clien@itri.org.tw). S.-J. Wei, Y.-H. Chu, and M.-H. Liao are with the Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan (e-mail: mhliaoa@ntu.edu.tw). M.-H. Lee is with the Institute of Electro-Optical Science and Technol- ogy, National Taiwan Normal University, Taipei 10610, Taiwan. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TED.2018.2868849 which can be used as the dielectric layer in MIM capacitors. However, permittivity (ε) and leakage current ( J g) are the critical issues which would limit the usage of these high-k dielectrics in the high-power circuit or the applications of energy storage devices [10]. Thanks to the continuous development of material, bar- ium titanate-based (BaTiO 3 , BTO) and bismuth ferrite-based (BiFeO 3 , BFO) materials have been proposed to be used as the dielectric layer in semiconductor devices since the past decade [11], [12]. For example, some researchers have, nowadays, observed the negative capacitance (NC) effect and demonstrate its successful and useful application in the low power emerging field-effect transistors (FETs) and memory devices. The FETs with NC effect possess the lower operated drain voltage (V DD ), and the steeper subthreshold swing is regarded as a potential candidate for the next-generation logic devices [13]–[16]. A BTO with a spontaneous polarization associated with the extremely high permittivity has a good breakdown endurance [17], [18], which can be regarded as the poten- tial candidate of capacitor dielectric in the next generation. Unfortunately, even in the tetragonal phase, a small saturated polarization of BTO limits its application on the energy storage devices in the future. On the other hand, a BFO is found to be as a nature multiferroic material, which exists two ferroic orders including ferroelectric and antiferromagnetic at the room temperature. High theoretical saturated polarization (∼90 μC/cm 2 ) implies more charges can be stored in this kind of dielectric. In addition, a BFO has a ferroelectric Curie temperature (T C ) of 1103 K and antiferromagnetic Néel temperature (T N ) of 643 K, which are suitable to be used in the high-temperature operation conditions [19]–[21]. However, the high J g associated with poor ferroelectricity limit the pos- sibility to use BFO only dielectric for the device applications. In this paper, we proposed a novel MIM capacitor structure with the multilayer BTO/BFO stack design. The tetragonal phase of a BTO thin film was presented through a few seconds rapid thermal anneal (RTA) process. The thickness of BFO thin film and an additional cap of BTO film were investigated and optimized to achieve the outstanding electrical characteristics in our multilayer BTO/BFO MIM capacitors. 0018-9383 © 2018 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. 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