Sadayoshi Horii

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 2.7u2009A/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.

Enhancing memory efficiency of Si nanocrystal floating gate memories with high-κ gate oxides

High-performance floating gate memory devices of Si nanocrystal (NC) dots on HfO2 gate oxide were fabricated at temperatures below 400°C. A large counterclockwise hysteresis of 5.2V, at an applied voltage of +6V, and a stored charge density of 6×1012cm−2 were observed. Moreover, the smaller band offset of the high-κ tunneling layer resulted in higher charge tunneling probabilities towards the Si NC dots than those observed with a SiO2 tunneling layer. Advantages in terms of scaling for a high-performance and stable reliability memory device are confirmed.

Effect of Nitrogen on Electrical and Physical Properties of Polyatomic Layer Chemical Vapor Deposition HfSixOy Gate Dielectrics

The effect of nitrogen incorporation on polyatomic layer chemical vapor deposition (PLCVD) hafnium silicate (HfSixOy) films was investigated. The physical and electrical properties of nitride hafnium silicate (HfSixOyNz) and HfSixOy dielectric films are reported. X-ray photoelectron spectroscopy (XPS) was used to check chemical compositions, nitrogen profile, band gap, and band offset of the HfSixOy and HfSixOyNz films. The nitrogen incorporation results in decreases in the band gap and band offset of the HfSixOy sample. The nitrogen profile obtained by secondary ion mass spectroscopy (SIMS) shows a gradient decrease from the surface to the interface. The prepared HfSixOy and HfSixOyNz films have reasonable electrical performance.

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.

Improving high-κ gate dielectric properties by high-pressure water vapor annealing

High-pressure water vapor annealing has been found to improve the electrical properties of high-κ gate oxides. A vapor-annealing time of less than 60 min was effective in decreasing leakage current density and increasing capacitance density. This improvement is related to the active species in the water vapor which can react with unsaturated bonds in the bulk oxide film and dangling bonds at the film interface. However, the electrical properties did not improve after longer annealing periods. Optimizing the annealing conditions is essential for obtaining high quality high-κ films.

Scalability of TiN/HfAlO/TiN MIM DRAM capacitor to 0.7-nm-EOT and beyond

We have proposed guiding principle of material selection of electrode/dielectric combination for MIM DRAM capacitors by theoretically taking the tunneling barrier height into account. Accordingly, we found that phase-controlled HfO2 (HfAlO) with TiN electrode is promising. TiN/HfAlO/TiN MIM capacitors with an ultra-thin Al2O3 on the bottom TiN electrode were fabricated and an EOT of 0.7 nm with a leakage current of 80 nA/cm2 was successfully achieved.

Theoretical Screening of Candidate Materials for DRAM Capacitors and Experimental Demonstration of a Cubic-Hafnia MIM Capacitor

To screen candidate materials for dynamic random-access memory capacitors, the tunneling probability at a constant equivalent oxide thickness (EOT) of metal-insulator-metal (MIM) capacitors was theoretically maximized according to a tradeoff between permittivity and band offset. As a result, it was found that cubic HfO2 with a TiN electrode is a promising candidate. TiN/Al-doped HfO2/TiN MIM capacitors were fabricated by inserting Al2O3 layers for phase control of HfO2 and for suppression of TiN oxidation. The fabricated capacitors exhibit leakage current of 80 nA/cm2 at 1 V and EOT of 0.7 nm. Moreover, the main leakage current was estimated to originate from oxygen vacancies.

lmproving high-k gate dielectrics properties by high pressure water vapor annealing

High-pressure water vapor annealing has been found to improve the electrical properties of highgate oxides. A vaporannealing time of less than 60min was effective in decreasing leakage current density and increasing capacitance density. This improvement is related to the active species in the water vapor which can react with unsaturated bonds in the bulk oxide film and dangling bonds at the film interface. However, the electrical properties did not improve after longer annealing periods. Optimizing the annealing conditions is essential for obtaining high quality highfilms. [DOI: 10.1143/JJAP.45.L120]

Hafnium Oxide Film Etching Using Hydrogen Chloride Gas

Hydrogen chloride gas removes the hafnium oxide film formed by atomic layer deposition at the etch rate of about 1 nm/min. A 100 nm-thick hafnium oxide film was perfectly etched off at 1173 K for 60 min by 100% hydrogen chloride gas at 100 sccm. A weight decrease in the hafnium oxide film was observed at temperatures higher than ca. 600 K, which corresponds to the sublimation point of hafnium tetrachloride. The etching by-product is considered to be hafnium tetrachloride. The etching technique developed in this study is expected to be applicable to various processes, such as the cleaning of a hafnium oxide film deposition reactor.

Production-Worthy HfSiON Gate Dielectric Fabrication Enabling EOT Scalability Down to 0.86 nm and Excellent Reliability by Polyatomic Layer Chemical Vapor Deposition Technique

0.86 nm and Excellent Reliability by Polyatomic Layer Chemical Vapor Deposition Technique Dai Ishikawa, Satoshi Kamiyama, Atsushi Sano, Sadayoshi Horii, Takayuki Aoyama, and Yasuo Nara Research Dept. 1, Semiconductor Leading Edge Technologies (Selete), Inc., 16-1 Onogawa, Tsukuba-city, Ibaraki, 305-8569, Japan Research Dept. 2, Semiconductor Equipment System Lab., Hitachi Kokusai Electric Inc., 2-1 Yasuuchi, Toyama-city, Toyama, 939-2393, Japan E-mail: ishikawa.dai@selete.co.jp Tel: +81-29-849-1261