Dohyun Lee

Fabrication of body-tied FinFETs (Omega MOSFETs) using bulk Si wafers

Nano scale body-tied FinFETs have been firstly fabricated. They have fin top width of 30 nm, fin bottom width of 61 nm, fin height of 99 nm, and gate length of 60 nm. This Omega MOSFET shows excellent transistor characteristics, such as very low subthreshold swing, Drain Induced Barrier Lowering (DIBL) of 24 mV/V, almost no body bias effect, and orders of magnitude lower I/sub SUB//I/sub D/ than planar type DRAM cell transistors.

Gate oxide integrity (GOI) of MOS transistors with W/TiN stacked gate

With W/TiN stack gate deposited at high temperature, excellent time-dependent dielectric breakdown (TDDB) characteristics of the gate oxide were obtained in MOS capacitors. In the case of negative gate bias where thin oxide reliability becomes critical, the TiN gate provides a much longer time to breakdown than that of n/sup +/-poly gate due to a larger barrier height and less F-N tunneling current. In spite of skipping the conventional reoxidation process, a breakdown field larger than 10 MV/cm could be obtained in MOS transistors by undercutting TiN with boiling H/sub 2/SO/sub 4/. With a double spacer and undercutting scheme, the short channel effect of NMOS and PMOS transistors could be suppressed up to L/sub gate//spl sim/0.3 /spl mu/m.

A new floating gate cell structure with a silicon-nitride cap layer for sub-20 nm NAND flash memory

A new cell structure of NAND memory devices, which employs an additional nitride layer between the top of a floating gate (FG) and inter-poly dielectrics (IPD), is devised to lesson a high electric field on the FG top edges during program. The cell structure is proved to be promising in sub-20 nm NAND generation in terms of larger program window, better endurance, and more robust data retention, which are obtained by decreasing a leakage current of IPD relating with the electric field on the FG top edges.

Characteristics of CMOSFETs with sputter-deposited W/TiN stack gate

W/TiN stack gate has been investigated as a new gate electrode in ULSI CMOSFETs. With the combination of low resistivity of W and Si-midgap workfunction of TiN, very low sheet resistance and the proper characteristics of both types of transistors could be obtained simultaneously. With the deposition of TiN film at high substrate temperature, the breakdown characteristics of gate oxide could be improved considerably. The proper condition of dry etching on this structure has been also obtained.

Oxygen- and photoresist-related interface states of 4H-SiC Schottky diode observed by deep-level transient spectroscopy

Trap levels play an important role in semiconductor power devices. The barrier height of a metal-semiconductor junction, one of the important factors of unipolar devices, is influenced by the trap levels at its interface, i.e., interface states. However, there has not been much research on the interface states of Schottky diodes yet. Here, we report newly found KI1, KI2, and KI3 interface states of 4H-SiC Schottky diodes. We observed their changes after the first deep-level transient spectroscopy measurements, in which temperature rises to 750 K, and discussed the origins of these changes by using X-ray photoelectron spectroscopy and scanning electron microscopy. The KI1 was related to oxygen and photoresist (PR) residue, the KI2 was related to oxygen, and the KI3 was related to the PR residue.

Robust process integration of 0.78 /spl mu/m/sup 2/ embedded SRAM with NiSi gate and low-K Cu interconnect for 90 nm SoC applications

The smallest high density embedded 0.78 /spl mu/m/sup 2/ 6T-SRAM cell for high performance 90 nm SoC applications was successively integrated by using leading edge technologies such as 193 nm ArF lithography, 1.2 nm gate oxide, 50 nm transistor and Cu dual damascene with low-K dielectric. Fully working for SRAM shows the SNM value above 200 mV. Device current of 870 /spl mu/A//spl mu/m and 390 /spl mu/A//spl mu/m for NMOS and PMOS respectively is achieved at 1.0 V operation. Reliability life time on hot carrier immunity shows more than 10 years.