Shuichi Ishizuka

Diagnostics of hydrogen role in the Si surface reaction processes employing in-situ Fourier transform infrared-attenuated total reflection

The oxidation process of H-terminated amorphous Si film on Ge and the reaction mechanism of the triethylsilane (TES)/H system which allows us to deposit an organic Si film conformably have been investigated employing in-situ FTIR(Fourier transform infra red)-ATR(attenuated total reflection). This measurement was demonstrated to be a sensitive and simple method to inspect the role of H(hydrogen) in their surface reactions. In the Si oxidation case, the H-terminated Si is readily oxidized by O(oxygen) atoms. The oxidation with O2 molecules proceeds gradually as the breaking of Si-H bonds and forming of H-Si-O bonds due to binding of O atoms with the back bond of Si for 700 min. After about 700 min, dissociated O atoms rapidly penetrate the Si film, and oxidize the bulk Si, leaving both Si-H and H-Si-O bonds still on the Si surface. Next, in the TES/H reaction system, gas phase FTIR spectra obtained by reactions of H atoms or H2 molecules with TES do not show appreciable change in a wide range of pressure. Nevertheless, in-situ FTIR-ATR reveals that TES reacts easily with H atoms on the surface, desorbing H2, methyl and ethyl groups.

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.