Hironobu Miya

Electrical and physical properties of HfO2 films prepared by remote plasma oxidation of Hf metal

The electrical and physical properties of thin hafnium oxide (HfO2) films fabricated by a remote plasma oxidation of a hafnium metal were investigated. The HfO2 capacitors with TiN electrodes exhibited excellent electrical characteristics such as equivalent oxide thickness (EOT) of 0.65 nm with leakage current density of 2.7 A/cm2 at the gate bias of Vfb-1 (V). The HfO2 thickness dependence of the EOT demonstrated that the permittivity of 19 for HfO2 layer and the interfacial layer thickness of 0.36 nm. X-ray photoelectron spectroscopy study revealed that the oxygen radicals oxidize the Hf metal selectively than Si substrate, leading to an increase of permittivity of HfO2 with reduced interfacial layer growth.

Infrared Study of Tris(dimethylamino)silane Adsorption and Ozone Irradiation on Si(100) Surfaces for ALD of SiO2

Adsorption of tris(dimethylamino)silane {[(CH 3 ) 2 N] 3 SiH, TDMAS} and decomposition of the adsorbed TDMAS with an ozone ambient on Si(100) surfaces as an atomic layer deposition (ALD) process of SiO 2 have been investigated using Fourier transform infrared absorption spectroscopy (IRAS) with a multiple internal reflection geometry. TDMAS dissociatively adsorbs on the Si(100) surface to produce adsorbates including hydroaminocarbons and Si hydrides even at room temperature. IRAS suggests that TDMAS adsorbs preferentially on OH sites on Si surfaces that are produced by an H 2 O adsorption. Ozone oxidizes TDMAS adsorbed on the Si surface and makes the surface active to further TDMAS adsorption to progress the ALD cycle. The mechanism of SiO 2 ALD process with TDMAS and ozone is discussed in this paper.

Metalorganic Chemical Vapor Deposition of HfO2 Films through the Alternating Supply of Tetrakis(1-methoxy-2-methyl-2-propoxy)-Hafnium and Remote-Plasma Oxygen

Thin films of hafnium oxide were deposited by sequence in which the supply of tetrakis (1-methoxy-2-methyl-2-propoxy)-hafnium and remote-plasma oxygen were alternated. Increasing the number of cycles of alternating supply led to decreased amounts of hydrocarbon impurities in the film and the realization of an amorphous characteristic for the as-deposited films. HfO2 dielectric capacitors produced by using this alternating supply technique exhibit values for leakage current that are two orders of magnitude lower than those of capacitors produced using the conventional process of metalorganic chemical vapor deposition. This effective improvement can be explained by the reduced presence of impurities, particularly H2O.

Impact of Hf Metal Predeposition on the Properties of HfO2 Grown by Physical and Chemical Vapor Deposition

Electrical and microstructural properties of a hafnium oxide (HfO2) grown by physical vapor deposition (PVD) and chemical vapor deposition (CVD) onto a predeposited hafnium metal (Hf) are investigated. In PVD in an Ar/O2 plasma atmosphere, energetic oxygen species oxidize the Si substrate through HfO2, generating a thick interfacial layer between the HfO2 and Si substrates. The interfacial layer, however, is found to be controllable to have a minimum equivalent oxide thickness (EOT) and lower leakage current by the predeposition of Hf metal due to the blocking of oxygen diffusion into the Si substrate by the oxidation of Hf metal itself. In addition to the oxygen blocking, the CVD-grown HfO2 films on the predeposited Hf metal layer are improved due to the easy dissociation of the Hf precursor on the metallic Hf layer with a shorter incubation time. The leakage current with the predeposited Hf metal is two orders of magnitude lower than that on the Si substrate, whereas the EOT and the interfacial layer thickness are invariant.

Metal-Organic Chemical Vapor Deposition of HfO2 by Alternating Supply of Tetrakis-Diethylamino-Hafnium and Remote-Plasma Oxygen

HfO2 films were fabricated through an alternating supply process, which consisted of deposition using tetrakis-diethylamino-hafnium (TDEAHf:Hf(N(C2H5)2)4), followed by oxidation using remote-plasma oxygen (RPO). Deposition rates were found to depend on temperature (above 350°C) and the supply duration of TDEAHf, which indicated a non-self-limiting growth mode. X-ray photoelectron spectroscopy (XPS) analysis revealed that as-deposited films fabricated by supplying only TDEAHf were unstable with the presence of carbon and nitrogen impurities, but these can be removed by supplying RPO. Sufficient supply durations of RPO produced stoichiometric HfO2 films accompanied by an efficient reduction in the leakage current of the films, but an excess RPO supply duration resulted in a larger equivalent oxide thickness (EOT) due to a decrease in the permittivity of the interfacial layer. By optimizing the supply durations of TDEAHf and RPO, a minimal EOT of 1.6 nm and a leakage current of 1×10-4 A/cm2 at -1 V relative to the flat-band voltage were achieved.

Analysis of Chemical Structures of Ultrathin Oxynitride Films by X-Ray Photoelectron Spectroscopy and Secondary Ion Mass Spectrometry.

Oxynitride films were formed on a hydrogen-terminated Si wafer and on a 2 nm Si oxide film wafer using nitrous oxide, nitric monoxide, and ammonia as nitrogen sources in a vertical furnace with a vacuum load-lock function. Thickness of the oxynitride films and their chemical depth profiles were studied by ellipsometry, angle-resolved X-ray photoelectron spectroscopy (AR-XPS), and secondary ion mass spectrometry (SIMS). Results revealed that the majority of nitrogen in oxynitride films is unevenly distributed at the interface between the Si wafer and the oxide film. The dissociation energies of the nitrogen sources were evaluated using the density functional theory. Nitrogen concentration was found to be related to the nitrogen sources in the following order, ammonia > nitric monoxide > nitrous oxide, which is the order of the dissociation energies of the nitrogen sources where ammonia exhibited the smallest dissociation energy and nitrous oxide the largest.

Low-temperature-atomic-layer-deposition of SiO2 with Tris(dimethylamino)Silane (TDMAS) and Ozone using Temperature Controlled Water Vapor Treatment

SiO2 ALD with precursors of tris(dimethylamino)silane (TDMAS) and ozone on Si(100) surfaces at room temperature were investigated by infrared absorption spectroscopy with a multiple internal reflection geometry. TDMAS dissociatively adsorbs on OH sites of hydroxylated Si surfaces and ozone irradiation is effective to remove the hydroaminocarbon adsorbates introduced in the course of the TDMAS adsorption. After the ozone treatment, H2O vapor treatments at substrate temperatures around 160 aC allow generation of OH sites for the TDMAS adsorption. The TDMAS adsorption and the ozone treatment at room temperature followed by the H2O treatment at 160 aC enable the cyclic deposition of SiO2. V-I measurements of SiO2 grown by the present 160 aC ALD indicated the deposited film has breakdown electric fields from 3 to 11 MV/cm. C-V measurements indicated that the present ALD is available for MOS capacitors.

Growth and effects of remote-plasma oxidation on thin films of HfO2 prepared by metal-organic chemical-vapor deposition

The metal-organic (MO) chemical vapor deposition of hafnium oxide (HfO2) films from a new MO precursor, Hf(OC(CH3)2CH2OCH3)4, was investigated. The deposition rate of HfO2 is higher when oxygen gas is being supplied with the precursor. However, films deposited in the presence of added oxygen contain large amounts of H2O due to oxidation of the Hf precursor. O2 addition process degraded HfO2 film properties. In situ remote-plasma oxidation (RPO) is found to be effective in reducing the contaminants in HfO2. Leakage current in HfO2/Si capacitors with TiN gate electrode is also shown to be lower when deposition is without the oxygen addition and RPO treatment is subsequently performed.

Atomic-Layer-Deposition of SiO2 with Tris(Dimethylamino)Silane (TDMAS) and Ozone Investigated by Infrared Absorption Spectroscopy

We have studied SiO2 ALD processes with precursors of tris(dimethylamino)silane (TDMAS) and ozone on Si(100) surfaces at room temperature by infrared absorption spectroscopy with a multiple internal reflection geometry. It was found that TDMAS dissociatively adsorbs on OH sites of hydroxyrated Si surfaces and ozone irradiation is effective to remove the hydroaminocarbon adsorbates introduced in the course of the TDMAS adsorption. Compensation of OH sites by a water vapor treatment after the ozone process is effective to sustain the cyclic SiO2 deposition.

Adsorption of Dibutyl Phthalate and Dioctyl Phthalate on Si Substrate

The behaviors of organic compounds such as dibutyl phthalate (DBP) or dioctyl phthalate (DOP) on a Si substrate are investigated by gas chromatograph and mass analysis (GC–MS). DBP or DOP source is set in a chemically clean booth, and organic amount is measured in air and on the substrate. At various concentrations of DBP or DOP, organic adsorption amount is measured and this amount is expressed by the Langmuir equation. In a mixed-gas atmosphere, the amounts of DBP and DOP are measured and it is clear that DBP concentration decreases when the total organic amount exceeds the saturated adsorption amount on the substrate. This phenomenon is understood as the replacement of DBP by DOP. In this paper, we describe the adsorption amount quantitatively in individual atmosphere of DBP or DOP and a mixed-gas atmosphere.