Doh-Y. Kim

Effect of methane concentration on size of charged clusters in the hot filament diamond CVD process

Abstract Negatively charged clusters of 3000–18000 atomic mass units, which had been predicted by the charged cluster model, were experimentally confirmed under typical process conditions of hot-filament diamond CVD using gas mixtures of 1–5% CH4 and H2. The cluster size increased with increasing methane concentration. Under conditions for the generation of small clusters containing a few hundred carbon atoms, high-quality diamond films were deposited while under conditions for the generation of larger clusters (>∼1000 atoms), a cauliflower structure was obtained.

Electrical and interfacial characteristics of ultrathin ZrO2 gate dielectrics on strain compensated SiGeC/Si heterostructure

Ultrathin ZrO2 gate dielectrics have been deposited on strain-compensated Si0.69Ge0.3C0.01 layers by rf magnetron sputtering. High-resolution transmission electron microscopy along with energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy show the formation of a polycrystalline ZrO2 and an amorphous Zr–germano–silicate interfacial layer between the deposited oxide and SiGeC films. A dielectric constant of 17.5 for ZrO2 and 7.0 for an interfacial-silicate layer have been calculated from the high-frequency capacitance–voltage measurements. These dielectrics show an equivalent oxide thickness as low as 1.9 nm for ZrO2 and 2.0 nm for the interfacial silicate layer. An extremely low leakage current density of ∼9×10−8 A/cm2 at a gate voltage of −1.0 V, breakdown field of 7 MV/cm and moderate interface state density of 6×1011 cm−2 eV−1 have been obtained for the fabricated capacitors.

Characteristics of ultrathin HfO2 gate dielectrics on strained-Si0.74Ge0.26 layers

The structural and electrical characteristics of HfO2 gate dielectrics along with the interfacial layers formed on strained-Si0.74Ge0.26 films have been investigated. The polycrystalline HfO2 film with a physical thickness of ∼4.0 nm and an amorphous Hf–silicate interfacial layer with a physical thickness of ∼4.5 nm have been observed by high-resolution transmission electron microscopy and time-of-flight secondary ion mass spectroscopy. The electrical properties have been studied using metal–oxide–semiconductor (MOS) structures. A dielectric constant of 26 for HfO2 film and 8.0 for Hf–silicate interfacial layer have been calculated from the accumulation capacitances of the capacitors. These dielectrics show an equivalent oxide thickness as low as 0.6 nm for HfO2 and 2.2 nm for the Hf–silicate layers. The fabricated SiGe MOS capacitors show a low leakage current density of ∼6.5×10−7 A/cm2 at a gate voltage of −1.0 V, breakdown field of 6.5 MV/cm, and moderately low interface state density of 5.5×1011 cm−2 ...

Spontaneous generation of charged clusters of a few nanometers during thermal evaporation of copper

Charged copper clusters of a few nanometers were spontaneously generated under typical copper thin film processing by evaporation at 1573 K. The deposition behavior of these clusters was drastically influenced under an electric field. After deposition for 10 s with a bias of +200, 0, and -200 V applied to the substrate, the number density of clusters was negligible on a positively biased substrate but ~1010 mm−2 on neutral and negatively biased substrates. After deposition for 5 min, the film thickness was 10, 100 and 120 nm on positive, neutral and negative substrates, respectively.

Effect of substrates on morphological evolution of a film in the silicon CVD process: approach by charged cluster model

Film morphology depends on the types of substrates used in the CVD process. This dependency has been studied based on the charged cluster model in the silicon CVD process. There exists a strong correlation between microstructure evolution and the charge transfer rate (CTR) of substrate materials. Films tended to be porous on substrates with a high CTR and dense on substrates with low CTR. The microstructure evolution could be explained by the interaction of charged clusters with the substrate. On substrates with a high CTR, charged clusters lose their charge quickly prior to landing. The resultant neutral clusters undergo attraction-dominant random sticking (flocculation), leading to a porous structure. On substrates with a low CTR, charged clusters lose their charge slowly after landing and undergo repulsion-dominant selective sticking (deflocculation), leading to a dense film.

Physical and electrical properties of ultrathin HfO2/HfSixOy stacked gate dielectrics on compressively strained-Si0.74Ge0.26/Si heterolayers

The physical properties of HfO2/HfSixOy stacked gate dielectric films deposited on compressively strained-Si0.74Ge0.26/Si heterolayers have been investigated using Rutherford backscattering spectrometry, high-resolution transmission electron microscopy, time-of-flight secondary ion mass spectroscopy, and Auger electron spectroscopy measurements. Polycrystalline HfO2 film with physical thickness of ∼4.0 nm and an amorphous interfacial layer with a physical thickness of ∼4.5 nm has been observed. Secondary ion mass spectroscopy and Auger electron spectroscopy analyses show the formation of an amorphous Hf-silicate interfacial layer between the oxide deposited and SiGe films. The electrical properties in terms of capacitance–voltage (C–V), conductance–voltage, hysteresis, current density-electric field, and shift in gate voltage under constant current stress have been studied using a metal–oxide–semiconductor structure. Dielectric constants of 26 for HfO2 and 8.0 for the interfacial Hf-silicate layer have be...

Low-pressure synthesis of diamond without hydrogen: approach by charged cluster model

Although hydrogen was firmly believed to be essential for the low-pressure synthesis, there have been a few reports, where diamond was synthesized in the absence of hydrogen. All the process of low-pressure diamond formation including the interstellar diamond dust have one common factor: presence of electric charge. The charged cluster model (J. Crystal Growth 62 (1996) 55) predicts that stabilization of diamond originates from charge rather than hydrogen. The diamond synthesis without hydrogen could be approached successfully by the charged cluster model.