Toshio Nakanishi

Characterization of Strain for High-Performance Metal-Oxide-Semiconductor Field-Effect-Transistor

Strain evaluation in a small area is required because the extremely short channel length in state-of-the-art metal–oxide–semiconductor field-effect transistors (MOSFETs) leads to a narrow and shallow channel region. The strain in this limited area strongly affects the device performance owing to carrier mobility modification. We used UV–Raman spectroscopy with a quasi-line-shape excitation source and a two-dimensional charge-coupled-device detector in order to evaluate the strain distribution in Si or Si-on-insulator (SOI) substrates with a patterned SiNx film. As results, the strain was concentrated at the SiNx/Si interface and SiNx film pattern edge. A large tensile (compressive) strain was induced by the SiNx film with inner tensile (compressive) stress in the space region that corresponds to a channel region of the n- or p-MOSFETs. We assume that these large strains in the space region are the origin of the mobility enhancement in n- or p-MOSFETs. Furthermore, in addition to the size effect of channel length, we confirmed that the strain could be controlled by changing SiNx film thickness, film stress, and the substrate (SOI or bulk-Si). The quantitative evaluation of strain by means of simulation is also discussed.

Study of Strain Induction for Metal–Oxide–Semiconductor Field-Effect Transistors using Transparent Dummy Gates and Stress Liners

Strain induction was studied on a sample that had a dummy gate tetraethyl orthosilicate–silicon dioxide (TEOS–SiO2) and SiN film by UV-Raman spectroscopy with high spatial and high wave-number resolution. The UV laser penetrated through the dummy gate that was transparent to UV light, which enabled us to evaluate strain in the channel of the metal–oxide–semiconductor field-effect transistor (MOSFET) model. Furthermore, we compared stress profiles obtained by finite element (FE) calculations with those obtained by UV-Raman measurements. There was a difference between the stress profiles in the line-and-space pattern sample and in the dummy-gate sample; large compressive (tensile) strains were concentrated at the channel edges in the dummy-gate sample with the compressive (tensile) stress liner, although both tensile and compressive strains existed at the channel edge in the line-and-space pattern sample. The results from UV-Raman spectroscopy were consistent with those obtained by the FE calculation.

Depth Profile of Nitrogen Atoms in Silicon Oxynitride Films Formed by Low-Electron-Temperature Microwave Plasma Nitridation

Angle-resolved photoelectron spectroscopy study was performed on the depth profile of nitrogen atoms in silicon oxynitride (SiON) films formed by the plasma nitridation of silicon dioxide using low-electron-temperature microwave plasma. The depth profile of nitrogen near the SiON surface was confirmed to increase and its peak position moves into SiON films with an increase in the nitridation time, which improves boron immunity. A new transport and reaction model of plasma nitridation is proposed to explain the time evolution of nitrogen concentration and its depth profile in the films. Here, the density of radical nitrogen atoms decreases exponentially with an increase in the distance from the surface, and the nitrogen concentration incorporated in the SiON film is approximately proportional to the logarithmic time of plasma nitridation. It was newly found that post-nitridation annealing strongly enhances the pile-up of nitrogen atoms at the Si–SiON interface owing to their diffusion from the inward tail of the nitrogen depth profile near the surface. It is deduced that the pile-up of nitrogen atoms induces Si–H bonds at the interface, which become the main trigger for the degradation of the negative bias temperature instability of p-channel metal–oxide–silicon transistors.

Nitrogen Profile Study for SiON Gate Dielectrics of Advanced Dynamic Random Access Memory

Nitrogen profile variations were systematically studied for the plasma nitridation process of the dynamic random access memory (DRAM) gate dielectrics, using angle-resolved X-ray photoelectron spectroscopy (AR-XPS), and their influences to the boron blocking and the device performances including negative bias temperature instability (NBTI) were investigated. Nitrogen atoms incorporated are localized in the surface vicinity within 1.5 nm of the thickness and at the peak positions around 0.5 nm. The high pressure and high temperature conditions of plasma nitridation are preferred for improving the NBTI and the tool productivity. Post nitridation anneal stabilizes the nitrogen atoms incorporated, and improves the immunity against the boron penetration into the gate dielectrics. Both of re-oxidation and the out-diffusion of nitrogen atoms take place simultaneously near the surface during the queue time after the plasma nitridation. Microwave plasma with the radial line slot antenna (RLSA) is a successful SiON gate insulator formation technology in the manufacturing of DRAM as well as logic devices.

Establishment of very uniform gas-flow pattern in the process chamber for microwave-excited high-density plasma by ceramic shower plate

The authors developed a ceramic upper shower plate used in the microwave-excited high-density plasma process equipment incorporating a dual shower-plate structure to establish a very uniform gas-flow pattern in the process chamber. Thousands of very fine gas-injection holes are implemented on this Al2O3 upper shower plate with optimized allocation to establish a uniform gas-flow pattern of plasma-excitation gases and radical-generation gases for generating intended radicals in the plasma-excitation region. The size of these fine holes must be 50μm or less in diameter and 8mm or more in length because these holes perform an essential role: They completely avoid the plasma excitation in these fine holes and upper gas-supply regions resulting from the plasma penetration into these regions from excited high-density plasma, even if very high-density plasma greater than 1×1012cm−3 is excited just under the ceramic upper shower plate by microwaves supplied from the radial line slot antenna. On the other hand, va...

HAX-PES Study of SiN Film for Charge Storage Layer in High Performance SONOS Type Flash Memory Cell

1 School of Science and Technology, Meiji University 1-1-1 Higashimita, Tama-ku, Kawasaki, 214-8571, Japan Phone: +81-44-934-7324 E-mail: d_kose@isc.meiji.ac.jp 2 TOKYO ELECTRON AT LTD 1-8 Fuso-cho, Amagasaki, Hyogo, 660-0891, Japan 3 Japan Synchrotron Radiation Research Institute (JASRI) 1-1-1 Koto, Saya-cho, Sayo-gun, Hyogo, 679-5198, Japan 4 Research Fellow of the Japan Society for the Promotion of Science 8 Ichiban-cho, Chiyoda-ku, Tokyo, 102-8472, Japan

Nitrogen Profile Study for SiON Gate Dielectrics of Advanced DRAM

Tokyo Electron Ltd., TBS Broadcast Center, 3-6 Akasaka 5-chome, Minato-ku, Tokyo 107-8481, Japan, Phone: +81-3-5561-7967 FAX: +81-3-5561-7396 E-mail: shigemi.murakawa@tel.com Management of Science and Technology, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan Tokyo Electron AT Ltd., SPA Development and Engineering 1-8 Fuso-cho, Amagasaki, Hyogo 660-0891, Japan New Industry Creation Hatchery Center, Tohoku University, Sendai 980-8579, Japan