Yoshitomo Kamiura

Evaluation of the initial oxidation of heavily phosphorus doped silicon surfaces using angle-dependent X-ray photoelectron spectroscopy

Abstract The room temperature oxidation of heavily P-doped Si(100) and poly-Si prepared by HF-treatment has been monitored for a period of about 1 year, using angle-dependent X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM), Immediately after HF-treatment, the P/Si atomic ratio increased with decreasing the photoelectron take-off angle, which implies that the more segregated-P existed in near the top surface region. The amount of activated Si, whose binding energy of Si2p was lower by 0.5 eV referred to that of lattice Si related to the amount of segregated-P closely. In the case of the P-doped samples, the chemical composition of the growing oxide films showed that not the Si ++ but the Si 3+ state was the dominant component until the oxide thickness, d , went up to over ~1.5 nm, while the Si 4+ was the major species for the moderately doped Si(100) and nondoped poly-Si, except in the very initial oxide ( d ). In contrast to the smooth AFM image of the moderately doped Si(100) surface, the heavily P-doped Si(100) showed very unique geometrical pattern.

Annealing behavior of phosphorus in native oxide films on heavily phosphorus doped silicon

Abstract Phosphorus redistribution and its chemical structure in the native oxide/Si as well as thermal oxides (∼ 30 nm)/Si were investigated using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The Si substrates were both heavily P-doped Si(100) and poly-Si, together with nondoped poly-Si. The in-depth profiles of P obtained by both XPS and SIMS showed that the dopant-P redistributed in the thin native oxide film (NOF) even at room temperature, and the amount of P increased drastically upon annealing. The amount of redistributed P was much larger for Si(100) than for poly-Si. The dominant chemical structure of P was not P2O5 but elemental-P and/or Si-P. Clear pileup of P at theNOF/Si interface could not be observed, since the thickness of NOF is very thin and probably P diffused into throughout the NOF. In the case of thermal oxides, both SIMS and XPS profiles exhibited a big pileup-P at the oxide/Si interface. The amount of pileup-P was about two times larger for the Si(100) than for the poly-Si, and it increased with annealing temperature. In the oxide films, the31P in SIMS as well as P0 and P2O5 features in XPS were also detected, although the intensities were very weak compared to those at the interface.

Phosphorus redistribution in the surface region of heavily phosphorus doped silicon

Abstract Heavily phosphorus doped samples of both Si(100) and polycrystalline silicon (poly-Si) together with nondoped poly-Si were examined using X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The surfaces were treated by HF or a mixed solution of HCl, H 2 O 2 and H 2 O. The Si2p photoelectron spectra from the heavily P-doped samples showed a new peak at below 0.4 eV from the Si 0 state, which suggests that the Si-P bond and/or activated Si atoms with dangling bond exist in the surface region of as large as several nanometers. This is further supported by the analysis of P2p spectra. A lots of P atoms diffused to the surface and broke the Si-Si bond, which caused the surfaces chemically unstable. Consequently, although the H-terminated nondoped poly-Si surface showed no oxide features, the heavily P-doped samples of both Si(100) and poly-Si exhibited 0.5–1 nm thick oxides. The sputter profiles of XPS and SIMS revealed that P atoms redistributed in the thin native oxide film and formed not P 2 O 5 but Si-P and/or elemental-P, even without intentional heating. The P-segregation was much more pronounced for the single crystal Si than for the poly-Si.

Investigation of Reoxidation and Phosphorus Behavior in HF-Treated Heavily Doped Silicon Surfaces

The thermally stimulated desorption (TSD) from aqueous HF-treated heavily phosphorus-doped Si(100) and polycrystalline Si surfaces was studied by Auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS) and mass spectroscopy. Desorption analyses indicated that reoxidation takes place slightly, to the same extent in the doped Si(100) and polycrystalline Si surfaces owing to hydrogen desorption. Moreover, a large quantity of phosphorus segregates to the top few layers in the desorption process of the oxides. It was clarified that the HF-treated polycrystalline silicon surface is terminated by hydrogen and resists oxidation similarly to a single-crystal one.

Spectroscopic study of rapid mixing and cooling of a high-density He plasma flow penetrating into hydrogen gas

Rapid mixing and cooling of a high-density helium plasma flow injected into hydrogen gas was experimentally confirmed for the first time, which is essentially of importance to generate a recombining plasma as a short-wavelength laser medium. The plasma flow was produced by a small Z-pinch gun. The electron temperature and density was spectroscopically measured to be 12 eV and 6×1016 cm-3, respectively, before injected into the hydrogen gas. After injection of the gas, the plasma was rapidly cooled down to 4 eV while the density increased only by about 30%. It was also found that the cooled plasma tended to a recombining phase. A simplified calculation was also performed on the collisional radiative model to show that the rapid cooling was due to the atomic collisions between the electrons and hydrogen atoms mixed with the plasma.