No abstract

No abstract

A nanoscale vertical-channel thin film transistor (V-TFT) with a channel length shorter than 160 nm was fabricated and characterized, in which In−Ga−Zn−O (IGZO) and SiO 2 thin films were prepared by atomic layer deposition and plasmaenhanced chemical-vapor deposition as active and spacer layers, respectively. The prototype device showed sound transistor operation with an on/off ratio of 8.8 × 10 3 and robust stabilities without any shift in transfer curves under positive/negative bias stresses at 1 MV/cm for 10 4 s. It was also noteworthy that there was no anomalous increase in off-state current during the positive bias stress test, which is suggested to originate from a high-quality interface between the SiO 2 spacer and IGZO active layers on the back-channel region. Alternatively, high off-state current levels were found to result from the formation of conduction paths generated by carbon-related residues on the vertical back-channel region through the surface time-of-flight secondary ion mass spectrometer analysis. Improvements in device performance and analysis of operation failures will provide insight into the implementation of nanoscale oxide V-TFTs.

With the rapid growth of the Internet, the importance of application traffic analysis increases for efficient network management. The statistical information in traffic flows, can be efficiently utilized for application traffic identification. However, the packet out-of-order and retransmission generated at the traffic collection point reduce the performance of the statistics-based traffic analysis. In this paper, we propose a novel method to detect and resolve the packet out-of-order and retransmission problem in order to improve completeness and accuracy of the traffic identification. To prove the feasibility of the proposed method, we applied our method to a real traffic analysis system using statistical flow information, and compared the performance of the system with the selected 9 popular applications. The experiment showed maximum 4.9% of completeness growth in traffic bytes, which shows that the proposed method contributes to the analysis of heavy flow.

Vertical channel thin film transistors (VTFTs) have been expected to be exploited as one of the promising three-dimensional devices demanding a higher integration density owing to their structural advantages such as small device footprints. However, the VTFTs have suffered from the back-channel effects induced by the pattering process of vertical sidewalls, which critically deteriorate the device reliability. Therefore, to reduce the detrimental back-channel effects has been one of the most urgent issues for enhancing the device performance of VTFTs. Here we show a novel strategy to introduce an In-Ga-Zn-O (IGZO) bilayer channel configuration, which was prepared by atomic-layer deposition (ALD), in terms of structural and electrical passivation against the back-channel effects. Two-dimensional electron gas was effectively employed for improving the operational reliability of the VTFTs by inducing strong confinement of conduction electrons at heterojunction interfaces. The IGZO bilayer channel structure was composed of 3-nm-thick In-rich prompt (In/Ga=4.1) and 12-nm-thick prime (In/Ga=0.7) layers. The VTFTs using bilayer IGZO channel showed high on/off ratio (4.8×109), low SS value (180 mV/dec), and high current drivability (13.6 µA/µm). Interestingly, the strategic employment of bilayer channel configurations has secured excellent device operational stability representing the immunity against the bias-dependent hysteretic drain current and the threshold voltage instability of the fabricated VTFTs. Moreover, the threshold voltage shifts of the VTFTs could be suppressed from +5.3 to +2.6 V under a gate bias stress of +3 MV/cm for 104 s at 60 °C, when the single layer channel was replaced with the bilayer channel. As a result, ALD IGZO bilayer configuration could be suggested as a useful strategy to improve the device characteristics and operational reliability of VTFTs.