Multi-Layered SiC Nanocrystals Embedded in SiO 2 Dielectrics for Nonvolatile Memory Application
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1160-H04-01
Multi-Layered SiC Nanocrystals Embedded in SiO2 layer for Nonvolatile Memory Application Dong Uk Lee1, Tae Hee Lee1, and Eun Kyu Kim1* Jin-Wook Shin2 and Won-Ju Cho2 1
Quantum-Function Spinics Laboratory and Department of Physics, Hanyang University, Seoul 133-791, Korea 2 Department of Electronic Materials Engineering, Kwangwoon University, Seoul 139-701, Korea
ABSTRACT A nonvolatile memory device with the multi-layered SiC nanocrystals embedded in the SiO2 dielectrics for long-term data storage was fabricated and its electrical properties were evaluated. The multi-layered SiC nanocrystals were formed by using post thermal annealing process. The transmission electron microscope analysis showed that the multi-layered SiC nanocrystals are created between the tunnel and the control oxide layers. The average size and density of the SiC nanocrystals were approximately 5 nm and 2x1012 cm-2, respectively. The memory window of nonvolatile memory devices with the multi-layered of SiC nanocrystals was about 2.7 V, and then it was maintained around 1.1 V after 105 sec.
INTRODUCTION The trend in development of electronic memory devices is toward small size, high density, and fast programming/erasing speeds. Moreover, a nonvolatile memory based on the charge storage in discrete charge traps requires a long retention time combined with these features [1]. As a charge trapping layer the silicon-oxide-nitride-oxide-semiconductor (SONOS) devices have a better performance than conventional flash memory [2]. However, they have problems with scaling down the structures of these devices. Above all, it was leakage current to the substrate because the tunnel oxide layer becomes ultra thin. Thus it doesn’t have a large on/off ratio for device performance. The nano-floating gate memory (NFGM) is a structure which has a few nano-sized particles isolated in dielectric materials and distributed between the tunnel and the control oxide layer. Due to these features, the NFGM has an advantage of preventing leakage current and improves the data retention and endurance. Recently, many studies have been reported about the NFGM including the various kinds of nanocrystals [3-10]. Especially, the SiC is a compound semiconductor belonging to IV group including SiGe. And it has many polytypes of different crystal structures with the cubic, the hexagonal or the rhombohedral, etc. The work function of SiC is about 4.0 ~ 4.5 eV. Also, its thermal stability is superior rather than metal materials. [11-14]. In this study the silicon-on-insulator (SOI) NFGM device structure with multi-layered SiC nanocrystals embedded in SiO2 dielectrics was fabricated and its electrical properties were evaluated as a function of temperature such as subthreshold characteristics (Vg-Id), output characteristics (Vd-Id), threshold voltage shift, and retention times.
EXPERIMENT The NFGM devices with SiC nanocrystals formed in the SiO2 dielectric were fabricated on the p-type (100) UNIBOND SOI wafers. These wafers consist of a thickness of 200 nm buried oxide lay
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