Suheun Nam

Dielectric characteristics of Al2O3–HfO2 nanolaminates on Si(100)

The structural characteristics and the chemical state of a HfO2–Al2O3 nanolaminate structure, depending on the postannealing temperature, were examined by x-ray diffraction and x-ray photoelectron spectroscopy. The structural stability is significantly enhanced up to 870 °C and so is able to sustain its amorphous and laminate structure. However, the laminate structure is drastically broken at the annealing temperature of 920 °C and the crystallization is locally generated. In particular, the formation of the interfacial layer during the postannealing treatment is effectively suppressed in the nanolaminated structure. The dielectric constant of the nanolaminate structure calculated from the accumulation capacitance increases from ∼10 to ∼17 as the annealing temperature increases. This change is closely related to the degree of the mixture composed by Al2O3 and HfO2.

Annealing effects of aluminum silicate films grown on Si(100)

The annealing effects of the thin aluminum silicate films grown on Si(100) by sputtering method were investigated using various physical and electrical measurements. All the films grown at the temperature of 300 °C using sputtering Al2O3 target show an amorphous structure as examined by x-ray diffraction and transmission electron microscopy. The amorphous structure is maintained up to 700 °C and then transformed to crystalline Al1.7SiO0.15O2.85 or mullite phase above the annealing temperature of 800 °C. The conduction process, charge trapping and detrapping characteristics, and trap charge density in metal–oxide–semiconductor structure are influenced by the annealing temperature. The depth profiling data using x-ray photoelectron spectroscopy show that the properties are closely related to the change of the interfacial layer and chemical state under the high temperature annealing. The breakdown characteristics are degraded after the annealing temperature of 900 °C due to the rapid change of the interfacia...

Interface control by modified sputtering on Pt/HfO2/Si system

Abstract Hafnium oxide (HfO 2 ) thin films were deposited by two different sputtering methods. In one case, hafnium (Hf) metal layer was pre-deposited before reactive sputtering process (method A), with the object of suppressing growth of the interfacial layer. Another one is conventional reactive sputtering, using DC magnetron in Ar+O 2 ambient (method B). Films made by method A showed thinner interlayer as well as good leakage current behavior, demonstrating that Hf pre-deposited layer can protect from incorporation of the oxidizing species. With high-temperature annealing, interfacial layer increases considerably, showing composition changes from silicate to SiO 2 (method A). In contrast, films by method B displayed little change in interlayer thickness since there exists previously thick SiO x bottom layer formed by O 2 stabilizing before reactive sputtering. Equivalent oxide thickness (EOT) of as-deposited and annealed HfO 2 films by method A is calculated to be ∼20 and ∼30 A, respectively, with allowable level of leakage current density.

Characteristics of ZrO2 Films with Al and Pt Gate Electrodes

We investigated interfacial stabilities of ZrO 2 films with Al and Pt electrodes formed by magnetron sputtering upon annealing and consequent changes of their metal-oxide-semiconductor capacitor characteristics. The as-deposited ZrO 2 films deposited using a sputtering power of 300 W were amorphous, while after annealing in N 2 at 600°C for 5 min the films became polycrystalline with a mixture of monoclinic and tetragonal phases. After the deposition of electrodes, we found that the amorphous interlayer which is presumed to be Al 2 O 3 was formed at the ZrO 2 /Al interface, while platinum (Pt) electrodes showed no interlayer at the interface with ZrO 2 films. The value of the capacitance equivalent thickness for the ZrO 2 film with the Al electrode was larger than that of the case with the Pt electrode by about 12 A, which is due to the presence of the additional Al 2 O 3 interlayer at the Al/ZrO 2 interface. The capacitance-voltage measurement showed that the difference in fiatband voltage (V FB ) between the ZrO 2 films and the two different electrodes is about 1.2 V, which is due to the work function difference between the two electrode materials.

Evaluation of the electrical properties and interfacial reactions for the polycrystalline Si1−xGex(x=0,0.6)/HfO2 gate stack

The effect of interfacial reactions on the electrical properties of a polycrystalline (poly) Si1−xGex/HfO2 gate stack were evaluated in terms of annealing conditions and the results were compared with those of a conventional poly-Si/HfO2 system. In the poly-Si0.4Ge0.6/HfO2 gate stack, silicate formation was the dominant reaction at the poly-Si0.4Ge0.6/HfO2 interface after annealing at 900 °C, resulting in the significant decrease in leakage current. From x-ray photoelectron spectroscopy analysis, the binding states of Hf silicates were clearly observed at a binding energy of about 16.1 eV in Hf 4f spectra and 102.7 eV in Si 2p spectra. However, in the poly-Si/HfO2 gate stack, the accumulation capacitance became undeterminable and the leakage current increased suddenly after annealing at 900 °C due to silicide formation at the poly-Si/HfO2 interface. The differences in reactions between a poly-Si/HfO2 interface and a poly-Si0.4Ge0.6/HfO2 interface are attributed to the accumulation of Ge.

Effect of deposition conditions of poly Si1−xGex films and Ge atoms on the electrical properties of poly Si1−xGex (x=0,0.6)/HfO2 gate stack

The effect of interfacial reactions at the poly Si1−xGex/HfO2 interface on the electrical properties of metal–oxide–semiconductor (MOS) capacitors with a poly Si1−xGex (x=0,0.6)/HfO2 gate stack was investigated relative to the deposition conditions for the poly Si1−xGex films, the Ge content of the poly Si1−xGex films, and the annealing temperatures, by the electrical measurements and x-ray photoelectron spectroscopy. With an increase in hydrogen induced from doping or from deposition gas used during the deposition of poly Si1−xGex (x=0,0.6) films, the accumulation capacitance of the MOS capacitors with a poly Si1−xGex/HfO2 gate stack became anomalous and the leakage current increased significantly, due to the formation of hydroxyl(OH–) ions or the partial reduction of HfO2 at the grain boundary. With an increase in Ge content of the poly Si1−xGex films, silicate formation became dominant at the poly Si1−xGex/HfO2 interface, resulting in a significant decrease in leakage current.

Interfacial Reaction in Poly Si1 − x Ge x / ZrO2 with Ge Content in Poly Si1 − x Ge x Films

The interfacial reaction between poly Si 1 - x Ge x (x = 0, 0.2, 0.4) and ZrO 2 films after annealing was investigated to use ZrO 2 films as an alternative gate dielectric. In the poly Si/ZrO 2 structure, silicidation was the dominant reaction due to continuous formation of Zr-silicide and SiO during annealing. However, in poly Si 1 - x Ge x (x = 0.2. 0.4)/ZrO 2 , silicate formation was the main reaction after annealing at 900°C for 30 min. In addition, after annealing at 800°C, the silicate layer was observed only in the poly Si 0 . 6 Ge 0 . 4 /ZrO 2 system.