Hyuckjae Oh

Novel Silicon On Insulator Metal Oxide Semiconductor Field Effect Transistors with Buried Back Gate

One of the most promising ways of realizing metal oxide semiconductor field effect transistors (MOSFETs) with high speed and ultralow power consumption is by varying the threshold voltage of fully depleted silicon on insulator (FD-SOI) MOSFETs by changing back gate bias. We have studied FD-SOI MOSFETs with buried back gate by experiment and simulation in order to realize both high-performance and low-voltage ULSIs. It was confirmed that the back gate is very effective not only for increasing the ON current in the active mode but also for decreasing the cut-off current in the standby mode by controlling the threshold voltage.

A novel atomic doping technology for ultra-shallow junction of SOI-MOSFETs

A novel technology to fabricate an ultra shallow source and drain extension (SDE) junctions for the future SOI-MOSFETs was investigated. In this technology, a dopant in an adsorbed layer on SOI surface diffuses into the substrate by the rapid thermal annealing (RTA) or laser annealing (LA). Arsenic adsorbed layer is formed using UHV CVD apparatus during thermal decomposition of AsH3 on Si (001) at 550 °C with a base pressure of 1× 10 − 10 Torr. RTA and LA have been identified as preferred annealing process for shallow junction formation because it provides low thermal budget control for junctions and high level of dopant activation and defect annealing. This method made it possible to control the junction depth with low sheet resistance for the sub 0.1 m SOI-MOSFET.

Low-Power and High-Sensitivity Magnetoresistive Random Access Memory Sensing Scheme with Body-Biased Preamplifier

In this paper, we describe a new magnetoresistive random access memory (MRAM) sensing scheme with a body-biased preamplifier for low-power and high-sensitivity operation. The proposed new MRAM sense amplifier consists of a current sense preamplifier with a body biasing differential pair of a common-gate amplifier and a voltage sense amplifier. The preamplifier controls bitline voltage appropriately and amplifies the difference in bitline current as current-mode sense amplifier. The new sense amplifier enhances sensitivity, and the body-biased preamplifier enables low-voltage operation. To evaluate the proposed circuit, the modeling of magnetic tunnel junction (MTJ) resistance characteristics was performed with a VHDL-AMS description, and the proposed circuit was simulated with a mixed signal circuit simulator. From the simulation result, it is confirmed that the proposed sensing scheme results in a 1.57 times faster access time than a conventional scheme, and that the power of the sense amplifier is lower than that of the conventional amplifier at the same speed.

Effects of ion implantation damage on elevated source/drain formation for ultrathin body silicon on insulator metal oxide semiconductor field-effect transistor

For high-speed and low-power performance, ultrathin body (UTB) silicon on insulator (SOI) metal oxide semiconductor field-effect semiconductors (MOSFETs) with an elevated source/drain (ESD) have been investigated using selectively epitaxial growth (SEG) technology. In this work, we found that the morphology of a SEG layer on an ultrathin Si film and the crystallinity of the top Si film are strongly dependent on ion implantation damage. The morphology and surface roughness of SEG layers were investigated by field emission scanning electron microscopy (FE-SEM) and the crystallinities of the top silicon films with and without ion implantation were characterized by atomic force microscopy (AFM) and Rutherford backscattering spectroscopy (RBS), respectively. Furthermore, to suppress ion implantation damage, a SEG layer was formed before ion implantation for source drain extension (SDE) formation by the sacrificial sidewall spacer method. As results, UTB SOI-MOSFETs with a flat ESD were successfully fabricated by the proposed method.

Fabrication and Evaluation of Magnetic Tunnel Junction with MgO Tunneling Barrier

Magnetoresistive random access memory (MRAM) has recently attracted considerable attention due to its non-volatility and high programming speed. A high Tunnel magnetoresistance (TMR) ratio is a key factor of MRAM. However, a conventional MRAM using aluminum oxide as insulator film shows a low TMR ratio of several tens of percents. MgO tunneling insulator is one of the candidates for achieving a high TMR ratio. In this study, we fabricated and evaluated Magnetic tunnel junctions (MTJs) with MgO tunneling barrier on a clad Cu word line.

Characteristics of Silicon-on-Low

We proposed a silicon-on-low k insulator (SOLK) metal oxide semiconductor field effect transistor (MOSFET) with a metal back gate for high-speed and ultralow power devices. In this work, Benzocyclobutene (BCB) and tetramethyl ammonium hydroxide (TMAH) were employed to fabricate SOLK Devices without damaging the transistor channels. We successfully fabricated the proposed submicron fully depleted (FD) SOLK MOSFETs with a metal back gate. The process technologies and electrical properties of SOLK MOSFETs were introduced in detail. Furthermore, threshold voltage shift was obtained at 55 mV/V using a NMOSFET and at 35 mV/V using a PMOSFET and drain current characteristics are enhanced by the back gate bias.

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SiGe selective epitaxial growth(SEG) and Ni silicidation technologies were developed for realizing high performance SOI MOSFETs with high current drivability. Then these technologies were applied for SOI MOSFET with elevated source/drain structure. The source/drain with the sheet resistance of 7/spl Omega//square could be obtained.

Insulator Metal Oxide Semiconductor Field Effect Transistor with Metal Back Gate

Requirements for the shallow junction technology in the sub-50 nm regime have been discussed. We propose a new ultra-shallow junction formation method called as Laser Induced Atomic Layer Doping (LI-ALD). The ultra-shallow junction with the depth of less than 20 nm could be formed using LI-ALD. The NMOS transistors with the ultra shallow junction formed by LI-ALD were demonstrated in this paper.