Yong Chan Jung

Atomic layer deposition of Y2O3 films using heteroleptic liquid (iPrCp)2Y(iPr-amd) precursor

Y2O3 films grown with a new liquid Y precursor, (iPrCp)2Y(iPr-amd), have been investigated in terms of the chemical properties of the precursor, atomic layer deposition (ALD) process, and material characterization of the deposited film, as well as its non-volatile resistive switching behavior has been investigated. A heteroleptic (iPrCp)2Y(iPr-amd) has been synthesized because it exists in a liquid phase at room temperature. A vapor pressure of 1 Torr is obtained at 168 °C, and thermal evaporation and decomposition begins from 250 °C and 425 °C, respectively. The Y2O3 film is fabricated by ALD technique using (iPrCp)2Y(iPr-amd) and water as the precursors. The growth of the Y2O3 films is self-limited with an ALD window from 350 °C to 450 °C and a growth rate of 0.06 nm per cycle. The deposited Y2O3 film shows a polycrystalline cubic structure, higher refractive index of over 1.8 at 632.8 nm, and a high dielectric constant of 24. The as-deposited Y2O3 film is highly stoichiometric and constant in terms of Y and O through the depth, and it also includes small –OH bonds in the film without any additional processes. The Ru/Y2O3/Ru resistor shows resistance switching between the low and high resistance states with voltage sweeping, and the resistance ratio between the two states is more than 1000 times, which is preferable for non-volatile memory operation.

Anode dependence of set voltage in resistive switching of metal/HfO2/metal resistors

The anode dependence of set voltage in resistive switching behaviors of metal/HfO2/metal resistors is investigated by applying positive and negative voltage polarity, and by changing the location of the electrodes made of various metals including Al, Pt, Mo, and Ru. When the same anode is applied to resistors whatever cathodes are, their set voltages in high resistance state are very similar. The strong anode dependence on set voltage is related to the potential near the anode domain owing to the partial rupture of the conducting filament. This rupture of filaments makes the thick insulator film thinner with a small potential barrier.

Uniform dehydrogenation of amorphous silicon thin films using a wide thermal annealing system

To prevent ablation caused by sudden hydrogen eruption during crystallization of hydrogenated amorphous Si (a-Si:H) thin films, a wide dehydrogenation thermal annealing (wDTA) system was developed to reduce hydrogen content in a-Si:H film prior to its crystallization process. The annealed a-Si:H films were fully dehydrogenated and nanocrystallized by the wDTA system. Raman scattering measurement revealed that the dehydrogenation process lowers the hydrogen content through disappearance of the peak intensity at 2000 cm−1. The a-Si:H film was transformed into nanocrystallized Si with lower residual stress. The major advantage of this wDTA was the large area uniformity of the thermal and the resulting material properties for 8 generation display. The uniform material characteristics of the hydrogen content, thickness, energy bandgap, and transmittance of the annealed Si films in the overall area was confirmed by Raman spectroscopy, spectroscopic ellipsometry, and UV–vis spectrometer measurement.

Metal-HfO2-Ge capacitor: Its enhanced charge trapping properties with S-treated substrate and atomic-layer-deposited HfO2 layer

The charge trapping properties of metal-HfO2-Ge capacitor as a nonvolatile memory have been investigated with (NH4)2S-treated Ge substrate and atomic-layer-deposited HfO2 layer. The interfacial layer generated by (NH4)2S-treated Ge substrate reveals a trace of -S- bonding, very sharp interface edges, and smooth surface morphology. The Ru-HfO2-Ge capacitor with (NH4)2S-treated Ge substrate shows an enhanced interface state with little frequency dispersion, a lower leakage current, and very reliable properties with the enhanced endurance and retention than Ru-HfO2-Ge capacitor with cyclic-cleaned Ge substrate.

Dielectric function of Si1−xGex films grown on silicon-on-insulator substrates

The dielectric functions of undoped and P-doped Si1−xGex (SiGe) films with a compressive strain on silicon-on-insulator (SOI) substrates are obtained by using spectroscopic ellipsometry. The respective Kato–Adachi and Tauc–Lorentz models are best fitted to the undoped and P-doped SiGe films to obtain their complex dielectric functions. The undoped SiGe films are characterized by multimodal peaks in the dielectric function, whereas the P-doped SiGe films exhibit only a broad peak. Further, the E0 and E1 critical points (CPs) of the undoped SiGe films are strongly dependent on the Ge concentration, whereas the E2 CPs are independent of concentration. The E0 and E2 CPs in the undoped SiGe films on an SOI substrate are lower than those of SiGe on a bulk-Si substrate owing to the higher strain. For P doping in SiGe, its dose causes non-monotonic variations in Eg and E0.

GeOx interfacial layer scavenging remotely induced by metal electrode in metal/HfO2/GeOx/Ge capacitors

The metal gate electrodes of Ni, W, and Pt have been investigated for their scavenging effect: a reduction of the GeOx interfacial layer (IL) between HfO2 dielectric and Ge substrate in metal/HfO2/GeOx/Ge capacitors. All the capacitors were fabricated using the same process except for the material used in the metal electrodes. Capacitance-voltage measurements, scanning transmission electron microscopy, and electron energy loss spectroscopy were conducted to confirm the scavenging of GeOx IL. Interestingly, these metals are observed to remotely scavenge the interfacial layer, reducing its thickness in the order of Ni, W, and then Pt. The capacitance equivalent thickness of these capacitors with Ni, W, and Pt electrodes are evaluated to be 2.7 nm, 3.0 nm, and 3.5 nm, and each final remnant physical thickness of GeOx IL layer is 1.1 nm 1.4 nm, and 1.9 nm, respectively. It is suggested that the scavenging effect induced by the metal electrodes is related to the concentration of oxygen vacancies generated by o...