Young-Bae Kim

Characterization of atomic-layer-deposited hafnium oxide/SiON stacked-gate dielectrics

Hafnium–oxide films deposited on a thermally grown SiON film and a hydrogen-terminated Si bare substrate by an atomic-layer-deposition technique have been investigated. Capacitance–voltage measurements show equivalent-oxide thicknesses of about 1.79 nm for a 4.2u200anmu200aHfO2/SiON stack capacitor and of about 1.84 nm for a 5.2u200anmu200aHfO2 single-layer capacitor. These measurements also show a dielectric constant of 18.1 for the HfO2 in the stack capacitor and of 11.2 for the HfO2 single-layer capacitor. The hysteresis of the stack capacitors is measured to be less than 40 mV, whereas that of the single-layer capacitor is 206 mV. Transmission-electron microscopy (TEM) and x-ray photoelectron spectroscopy indicated that the dielectric films are amorphous structure, rather than crystalline or phase-separated silicide and oxide structures. TEM showed that the interface of the stack capacitor can be stable to at least 850u200a°C.

Enhanced leakage current properties of Ni-doped Ba0.6Sr0.4TiO3 thin films driven by modified band edge state

1% Ni-doped barium strontium titanate (BST) thin film deposited at room temperature reveals the significantly enhanced leakage current performance which is extraordinarily effective for low temperature applications. Significant leakage current suppression of >2 orders was achieved for electric fields from 0.25 to 2 MV/cm in Pt/Ni-doped BST/Pt metal-insulator-metal (MIM) capacitor cells compared to undoped BST. For Ni doping at the 1% level, the spectral dependence of (i) the imaginary part of the complex dielectric constant, e2, obtained from the rotating compensator enhanced spectroscopic ellipsometry and (ii) OK1 absorption spectra obtained from synchrotron x-ray absorption spectroscopy shows significant differences (0.26±0.15u2002eV) in the conduction band edge trap depth relative to undoped BST. The valence band (VB) edge x-ray photoelectron spectroscopy analysis reveals the Fermi energy level downshift of 0.4 eV for Ni-doped BST toward the VB edge. There is a direct correlation between these changes in band edge states of BST thin films with Ni doping and the improved electrical performance in MIM capacitors led by the qualitatively different charge injection mechanism. The proposed transition metal doping process and analysis approach provide a pathway for charge injection control driven by band edge state changes in other perovskite oxides for low temperature (i.e., room temperature) applications.1% Ni-doped barium strontium titanate (BST) thin film deposited at room temperature reveals the significantly enhanced leakage current performance which is extraordinarily effective for low temperature applications. Significant leakage current suppression of >2 orders was achieved for electric fields from 0.25 to 2 MV/cm in Pt/Ni-doped BST/Pt metal-insulator-metal (MIM) capacitor cells compared to undoped BST. For Ni doping at the 1% level, the spectral dependence of (i) the imaginary part of the complex dielectric constant, e2, obtained from the rotating compensator enhanced spectroscopic ellipsometry and (ii) OK1 absorption spectra obtained from synchrotron x-ray absorption spectroscopy shows significant differences (0.26±0.15u2002eV) in the conduction band edge trap depth relative to undoped BST. The valence band (VB) edge x-ray photoelectron spectroscopy analysis reveals the Fermi energy level downshift of 0.4 eV for Ni-doped BST toward the VB edge. There is a direct correlation between these changes in b...

Influence of electric field intensity on the copper catalyst-mediated crystallization of amorphous silicon

The effects of electric field intensity on the crystallization of amorphous silicon (a-Si) using the field-aided lateral crystallization (FALC) process have been studied in the range of 0–180 V∕cm. The crystallization velocity increases as the electric field intensity increases. Moreover, the better quality of polycrystalline silicon resulted in the films that crystallized faster. The activation energy of the metal-induced lateral crystallization process calculated from the Arrhenius plot is 1.79 eV (±0.03 eV), whereas that of the FALC process is 1.65 eV (±0.04 eV) regardless of the electric field intensities. It is also shown that the electric field affects both the enhancement of the preexponential factor in the Arrhenius equation and the decrease in the energy barrier height for the crystallization. In particular, the effect is almost the same in the temperature range of 400–500u2009°C. The increase in the crystallization velocity is attributed to the field-enhanced diffusion of copper ions in the Cu3Si cr...

Auger Electron Spectroscopy Study on the Tolerance to Forming Gas Anneal of (Ba, Sr)TiO3 with SiO2 capped (Ba, Sr)RuO3 Electrode

The tolerance to forming gas anneal of (Ba, Sr)TiO3 with SiO2 capped (Ba, Sr)RuO3 as its electrode was investigated through Auger electron spectroscopy (AES). All the samples were prepared by RF magnetron sputtering technique and forming gas (10% H2 + 90% N2) anneal was carried out at 400°C for 30 min. In measuring AES spectroscopy, the KLL transition of oxygen was used for the criterion of reduction because oxygen showed the most sensitive chemical shift and concentration change during forming gas anneal among the constituent elements. Several kinds of relevant experiments were carried out in order to find out the effects of SiO2 capping. It turned out that the major causes of the tolerance to the forming gas anneal are the blocking capability of SiO2 against the diffusion of H2O that is one of the reduction reaction products and the good properties of interfaces between the (Ba, Sr)RuO3 and the (Ba, Sr)TiO3 originated from the outstanding structural match and chemical compatibility between them.

Spike Annealing Effect on Cu-Field Aided Lateral Crystallization

In this study, the influence of spike anneal on the crystallization of amorphous silicon films in the field aided rapid thermal annealing (FARTA) process was investigated. The base temperature was maintained at 450°C and the spike anneal temperatures ranged from 530°C to 750°C. By this process, the crystallization was accomplished in a significantly reduced time frame compared to that required by the conventional field aided lateral crystallization (FALC), although the portion of thermal budget for the spike anneal in the total thermal budget is at most 8.7%. In addition, the comparison of the degree of crystallization between the typical FALC process and the 700°C spike anneal FARTA process revealed a 13% higher degree of crystallization in the latter process. Consequently, it was demonstrated that the FARTA process, which combines the FALC and spike anneal, could realize not only the usage of a cost-effective, low-temperature softening substrate because of its low thermal budget and fast crystallization, but also high-quality polysilicon formation.

Crystallization of amorphous silicon films by Cu-field aided rapid thermal annealing

In this study, a technique, field aided rapid thermal annealing (FARTA) was proposed to crystallize the amorphous silicon films for a substantially short process time at low temperature. A spike shape pulsed rapid thermal annealing has been added to the field aided lateral crystallization (FALC) of amorphous silicon films deposited by plasma enhanced chemical deposition on glass. By adopting the FARTA process, directional crystallization of a-Si could be successfully achieved at 450u200a°C within a few hundreds of seconds. Other advanced crystallization methods such as FALC and metal induced lateral crystallization (MILC) normally require several hours for the same degree of crystallization even at 500u200a°C. Crystallization velocity using the FARTA process was measured to be 186.3 μm/h when the a-Si experienced 10 cycles of 60 s 450u200a°C thermal bias followed by 1 s 750u200a°C spike anneal. This value was six times faster than that by the MILC process at the same heating condition. From this study we found that both ...

Effect of Forming Gas Anneal on the Properties of (Ba, Sr)RuO3 and (Ba, Sr)TiO3

The effects of forming gas anneal on (Ba, Sr)RuO3 and (Ba, Sr)TiO3 films are investigated. Three kinds of samples such as BSR/Si, SiO2/BSR/Si, and SiO2/BSR/BST/BSR/Si were prepared by RF magnetron sputtering technique and forming gas (10% H2+90% N2) anneal was carried out at 400°C for 30 min. The samples having a SiO2 capping layer were employed to examine the effects of forming gas anneal (FGA) on the films under the similar condition to the standard complementary metal oxide semiconductor (CMOS) process. In contrast to the BSR film directly exposed to H2 ambient, the SiO2 capped BSR film was not damaged during H2 annealing. The SiO2 capping turned out to be also effective in preserving the properties of BSR film in BSR/BST/BSR capacitor structure, and the BSR electrode with the use of SiO2 capping layer made it possible to keep the electrical properties of BST films in the capacitor structure within the practical level.