Nonvolatile Memory Characteristics of Nanocrystalline Molybdenum Oxide Embedded High- k Film - Device Performance and Li
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Nonvolatile Memory Characteristics of Nanocrystalline Molybdenum Oxide Embedded High-k Film - Device Performance and Light Wavelength Effects Yue Kuo1, Xi Liu1,2, Chia-Han Yang1,3, and Chi-Chou Lin1 1
Thin Film Nano & Microelectronics Research Laboratory, Texas A&M University, College Station, TX 77843-3122, U.S.A. 2 Department Department of Industrial and Systems Engineering, Ohio University, Athens, OH 45701 3 Department of Industrial and Information Engineering, University of Tennessee, Knoxville, TN 37996, U.S.A. ABSTRACT The nanocrystalline molybdenum oxide embedded Zr-doped HfO2 high-k nonvolatile memory device has been fabricated using the one pumpdown sputtering process and a rapid thermal annealing step. The majority embedded molybdenum existed in the MoO3 nanocrystal form but a small amount of metallic molybdenum was also detected. The memory function of this device was based on the hole trapping-and-detrapping mechanism. The embedded nanocrystals retained charges after the breakdown of the high-k stack. The charge storage capacity was influenced by light exposure, especially the wavelength. The silicon/high-k interface was also affected by the exposed light. This study provided an insight of the function of the embedded nanocrystals and the light effects on the device. INTRODUCTION The high-k gate dielectric material is a critical element in the nano size MOSFET, e.g., for the low leakage current and high reliability [1]. High-k dielectrics are also important for nonvolatile memory (NVM) devices [2]. The nanocrystals embedded high-k dielectric structure has many advantages over the polysilicon-based floating gate dielectric structure in memory applications, such as the lower power consumption and the longer charge retention time [3,4]. Among many metal oxide high-k dielectrics, the Zr-doped HfO2 (ZrHfO) film has a higher crystallization temperature, a larger effective k value, and a lower interface state density than the undoped HfO2 film [5-8]. Recently, the authors’ group reported several nanocrystals embedded ZrHfO high-k dielectric NVMs [3, 9,10,11]. In addition to the large charge storage capacity, the capacitor retained charges for more than 10 years at room temperature. The charge trapping and detrapping characteristics of the capacitor with the ZrHfO gate dielectric and the ITO gate electrode were not sensitive to light exposure [12]. However, when the discrete nanocrystalline ZnO (nc-ZnO) dots were embedded in the ZrHfO layer, the memory function and capacitor were changed upon the exposure to the tungsten light because of the generation of electron-hole pairs in the nanodots. This phenomenon is potentially important in many electronic and optoelectronic applications. However, there is lack of information on the influence of the individual wavelength on the charge storage mechanism and capacity, which are critical in practical applications. In this paper, authors studied the memory functions of the nanocrystalline molybdenum oxide (nc-MoOx) embedded ZrHfO high-k dielectric structure in the dark
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