Dong Chan Suh

Improved thermal stability of Al2O3/HfO2/Al2O3 high-k gate dielectric stack on GaAs

Thermal stability of HfO2 high-k gate dielectric on GaAs is investigated. Compared to HfO2 gate dielectric, significant improvements in interfacial properties as well as electrical characteristics were found by constructing a Al2O3/HfO2/Al2O3 dielectric stack. At elevated temperatures, the amorphous Al2O3 layers were effective in inhibiting crystallization of HfO2. Since the passivating Al2O3 layers prevent interfacial oxide and trap charge formation, it aids in reducing the increasing rate of equivalent oxide thickness as well as capacitance-voltage hysteresis. Transmission electron microscopy and x-ray photoelectron spectroscopy data supported the improved electrical characteristic of GaAs metal-oxide-semiconductor capacitors with Al2O3/HfO2/Al2O3 gate dielectric stack.

Changes in the structure of an atomic-layer-deposited HfO2 film on a GaAs (100) substrate as a function of postannealing temperature

The effects of postannealing temperature on the crystal structure and energy band gap (Eg) values of atomic-layer-deposited HfO2 films grown on a GaAs (100) substrate were investigated. In postannealed HfO2 films prepared using a rapid thermal annealing (RTA) process in a N2 ambient at temperatures over 600 °C, the initially produced, partially crystallized HfO2 film changed into a well-ordered crystalline structure with no detectable interfacial layer between the film and the GaAs substrate. In the case of a RTA prepared at 700 °C, the thickness of the film was relatively increased compared to that of an as-grown film. Changes in the depth profile data related to stoichiometry and electronic structure after the annealing treatment indicated that Ga oxide is formed within the HfO2 film during the RTA. The formation of Ga oxide in the film significantly affected the Eg values, i.e., the Eg changed from 5.5 for an as-grown film to 4.7 eV for a film annealed at 700 °C.

Effects of Interface Al2O3 Passivation Layer for High-k HfO2 on GaAs

Effects of Interface Al2O3 Passivation Layer for High-k HfO2 on GaAs Dong Chan Suh,* Young Dae Cho,* Dae-Hong Ko, Yongshik Lee, Kwun Bum Chung, and Mann-Ho Cho Department of Materials Science and Engineering, Department of Electrical and Electronics Engineering, and Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea Department of Physics, Dankook University, Cheonan 330-714, Korea

Effects of postnitridation annealing on band gap and band offsets of nitrided Hf-silicate films

The effects of film composition and postnitridation annealing on band gap and valence band offset were examined in nitrided Hf-silicate films prepared using direct plasma nitridation. Regardless of the composition of Hf-silicate films, the band gap characteristics were similar after direct plasma nitridation (4.5±0.1eV) and postnitridation annealing (5.6±0.1eV). The decrease in band gap after direct plasma nitridation was caused by the formation of Si–N and Hf–N bonds, while the recovery of band gap by postnitridation annealing was influenced by the dissociation of unstable Hf–N bonds. The difference in valence band offset was strongly related to the chemical states of Si–N bonds.

The Effect of NH3 on the Interface of HfO2 and Al2O3 Films on GaAs(100) Surfaces

We investigate the effects of heat-treatment under NH 3 ambient on the formation of Ga-O at the interface between GaAs and high-k dielectric materials deposited by atomic layer deposition. Compared with the heat-treatment under N 2 ambient, the monochromatic X-ray photoelectron spectroscopy analysis reveal that the formation of Ga-O is greatly suppressed under NH 3 ambient for HfO 2 on GaAs. However, the same experiments for Al 2 O 3 on GaAs show that the effect is negligible. We examine the different reaction mechanisms of the NH 3 nitridation processes for two different high-k dielectric materials on GaAs.

Growth Kinetics of Atomic Layer Deposited Hf Silicate-Like Films using Hf [ N ( CH3 ) ( C2H5 ) ] 4 and SiH [ N ( CH3 ) 2 ] 3 Precursors via an H2O Oxidant

The growth kinetics of Hf silicate-like films, prepared using Hf[N(CH 3 )(C 2 H 5 )] 4 and SiH[N(CH 3 ) 2 ] 3 precursors and H 2 O as an oxidant were investigated as a function of alternating deposition of HfO 2 and SiO 2 . The ratio of the alternate deposition of HfO 2 and SiO 2 affected the growth behavior of Hf silicate-like films, but the thickness of the films remained constant, regardless of the total cycles of HfO 2 and SiO 2 . The nucleation of HfO 2 showed a strong dependence on the preceding growth cycles of SiO 2 , as evidenced by in situ medium energy ion scattering analysis. Hf coverage was reduced with an increasing ratio of SiO 2 deposition cycles. The suppression of the nucleation of HfO 2 is related to remnant Si-H bonds induced by the SiH[N(CH 3 ) 2 ] 3 precursor after the atomic layer deposited growth of SiO 2 .

Investigation of the Interface Oxide of Al2O3/HfO2 and HfO2/Al2O3 Stacks on GaAs(100) Surfaces

The physical and the electrical properties of ALD Al2O3 / HfO2 and HfO2 / Al2O3 stacks on GaAs systems before after heat treatment are investigated. Results reveal that the addition of Al2O3 layers suppresses not only the poly-crystallization of HfO2 even after heat treatment, but also the formation of interfacial oxide. High-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS) analysis results are presented.