Jin-Suk Wang

Passivation of dry-etching damage using low-energy hydrogen implants

Reactive-ion etching-and ion-beam etching have been shown to cause a damaged layer at silicon surfaces. In-this study it is demonstrated that the damage in this layer can be passivated using a room-temperature low-energy hydrogen ion implantation from a Kaufman ion source. For the etching conditions used and for the range of beam parameters explored, 5-min implants with a 0.4-keV hydrogen beam were most effective in passivating dry-etching damage.

Ni Germanide Utilizing Ytterbium Interlayer for High-Performance Ge MOSFETs

In this article, ytterbium (Yb) incorporation into NiGe is proposed to improve the thermal stability of Ni germanide for high-performance Ge metal-oxide-semiconductor field-effect transistors (Ge MOSFETs). The Yb/Ni/TiN structure shows suppression of NiGe agglomeration and better surface morphology than the Ni/TiN structure after a postgermanidation annealing of up to 550°C for 30 min. It is notable that Yb atoms distribute uniformly at the top region of NiGe. NiGe agglomeration was retarded by Yb incorporation, and the thermal stability of NiGe was therefore improved.

Work function variation of nickel silicide using an ytterbium buffer layer for Schottky barrier metal-oxide-semiconductor field-effect transistors

In this article, incorporating ytterbium into Ni-silicide using an Yb interlayer is proposed to reduce the work function of Ni-silicide for a Ni-silicided Schottky barrier diode. The proposed Ni-silicide exhibited good Schottky barrier diode characteristics owing to the reduced work function of about 0.15−0.38 eV. Even though the ytterbium layer was deposited below nickel, a ternary phase (YbxNi1−x)Si is formed at the top region of the Ni-silicide, which is believed to reduce the work function.

The Effect of Triple Capping Layer ( Ti ∕ Ni ∕ TiN ) on the Electrical and Structural Properties of Nickel Monosilicide

The effects of a triple capping layer (Ti/Ni/TiN) on the electrical and structural properties of nickel monosilicide (NiSi) have been investigated as a function of rapid thermal annealing temperature. It is shown that thesamples with the triple capping layer produce lower sheet resistances than the samples with double (Ti/TiN) or single (TiN) capping layers across the whole annealing temperature range. Scanning transmission electron microscopy results show that, after annealing, interfacial layers consisting of Ni, Ti, and Si elements are formed in the samples with the triple and double capping layers. It is further shown that the triple-capped samples are more thermally stable than the double- and single-capped samples. This could be attributed to the segregation of Ti atoms in grain boundaries of NiSi film, which reduces grain boundary energy. The simple model is presented to explain the influence of Ti reaction flux on the surface morphology and the interface uniformity between the silicide and Si substrate.

Novel Nitrogen Doped Ni Self-Alingned Silicide Process for Nanoscale Complementary Metal Oxide Semiconductor Technology

In this paper, 1%-nitrogen doped nickel was proposed to improve the thermal stability of Ni-silicide for nano-scale N-type Metal Oxide Semiconductor Field Effect Transistor. It is shown that thermal stability of nickel silicide is improved a lot by the Nitrogen incorporation in NiSi layer using the 1%-nitrogen doped nickel target. Even after post-silicidation annealing at 650°C for 30 min, the low resistivity NiSi with low junction leakage current can be achieved. Moreover, improved device characteristics such as threshold voltage, transconductance, and on-off current, subthreshold slope were obtained in 80 nm NMOSFET.

Characterization of Nickel-Silicide Dependence on the Substrate Dopants for Nanoscale Complementary Metal Oxide Semiconductor Technology

In this paper, the dependency of silicide properties such as sheet resistance and cross-sectional profile of NiSi on the source/drain and gate dopants is described. There was minimal difference in sheet resistance among the dopants used, namely, As, P, BF2 and B11, just after the formation of NiSi using RTP. However, NiSi properties strongly depended on the dopants when additional thermal treatment was applied after silicidation. P-type dopants showed superior properties compared to n-type dopants, and BF2-doped silicon showed the most stable property, while As-doped silicon, the poorest. The principal reason for the excellent properties of the BF2-doped sample is the retarded Ni diffusion due to the existence of fluorine. In contrary, the As-doped sample showed severe agglomeration and abnormal oxidation of NiSi possibly due to the As sublimation.

Characterization of Surface Morphology and Light Scattering of Transparent Conducting ZnO:Al Films as Front Electrode for Silicon Thin Film Solar Cells

Changes in the surface morphology and light scattering of textured Al doped ZnO thin films on glass substrates prepared by rf magnetron sputtering were investigated. As-deposited ZnO:Al films show a high transmittance of above 80% in the visible range and a low electrical resistivity of 4.5×10 Ω·cm. The surface morphology of textured ZnO:Al films are closely dependent on the deposition parameters of heater temperature, working pressure, and etching time in the etching process. The optimized surface morphology with a crater shape is obtained at a heater temperature of 350 C, working pressure of 0.5 mtorr, and etching time of 45 seconds. The optical properties of light transmittance, haze, and angular distribution function (ADF) are significantly affected by the resulting surface morphologies of textured films. The film surfaces, having uniformly size-distributed craters, represent good light scattering properties of high haze and ADF values. Compared with commercial Asahi U (SnO :F) substrates, the suitability of textured ZnO:Al films as front electrode material for amorphous silicon thin film solar cells is also estimated with respect to electrical and optical properties.

Microstructural Innovation of Ni Germanide on Ge-on-Si Substrate by Using Palladium Incorporation

In this article, thermally stable Ni germanide using palladium (Pd) incorporation is proposed for high performance germanium metal-oxide-semiconductor field-effect transistors, and a microstructural analysis of the Ni germanide is performed in depth. The proposed Pd/Ni/TiN structure exhibited a stable sheet resistance despite high temperature postgermanidation annealing of up to 500°C for 30 min. The cause of the improved thermal stability is determined to be caused by the pileup of Pd atoms at the bottom region of NiGe, which resulted in the retardation of NiGe agglomeration by the formation of PdGe or NiPdGe there.

On-chip charge pumping method for characterization of interface states of ultra thin gate oxide in nano CMOS technology

For the first time, on-chip charge pumping method is proposed to characterize ultra thin gate oxide for nano-scale CMOSFETs. Designed on-chip charge pumping system can supply 30-500MHz square-type pulse waves to DUT transistor and measured charge pumping current showed no gate tunneling current dependency which can be easily monitored in very thin gate oxide. In addition to the measurement of interface states by fixed-amplitude method, the distribution of interface states in channel region can be easily extracted by fixed-base method using this system. The proposed method is also successfully applied to analyze hot-carrier stress-induced threshold voltage (Vt)-degradation and to evaluate plasma process induced damage in terms of interface trap density

Abnormal oxidation of nickel silicide on N-type substrate and effect of preamorphization implantation

In this study, the abnormal oxidation of nickel silicide on an n-type substrate and the suppression of the abnormal oxidation by N2 preamorphization implantation (PAI) have been investigated. Although there is little difference in the sheet resistance regardless of dopants just after the silicidation, a strong dependence was observed after high-temperature postsilicidation annealing. Only the As-doped source/drain was oxidized during the postsilicidation annealing, and silicide properties were severely degraded. To prevent the unintended oxidation of the As-doped source/drain, N2 or Ge PAI was implemented and the thermal stability was greatly improved by N2 PAI with a Ti capping layer.