Hiroko Tashiro

Effect of fluorine on boron diffusion in thin silicon dioxides and oxynitride

We investigated the effects of fluorine on boron diffusion in thin silicon oxides used for metal‐oxide‐semiconductor structures, including silicon dioxide and oxynitride. We used secondary ion mass spectroscopy to measure the boron penetration depth from p+‐polycrystalline silicon to the silicon substrate through the silicon oxides for various fluorine doses. We compared experimental and simulated results and determined the boron diffusion coefficients in the silicon oxides. The diffusion coefficients have an Arrhenius relationship for each fluorine dose. The diffusion coefficients at a fluorine dose of 1×1016 cm−2 were 30 times larger than with no fluorine dose, and at a fluorine dose of 1×1015 cm−2, diffusion coefficients were 5 times larger. With oxynitride, fluorine has the same enhancing effect. With no fluorine, the diffusion coefficients were independent of oxide thickness. When fluorine is implanted into polycrystalline silicon, especially with a high dose, the diffusion coefficient is larger for ...

Boron Diffusion Through Pure Silicon Oxide and Oxynitride Used for Metal‐Oxide‐Semiconductor Devices

We studied boron diffusion in thin silicon oxides including pure SiO 2 and oxynitride that are used for metal-oxide-semiconductor transistors. We measured the boron penetration using secondary ion mass spectrometry. By comparing simulated and experimental results, we found that the boron diffusivity in pure SiO 2 , D PO , is 3.96 × 10 -2 exp (-3.65eVLkT) cm 2 /s, and that in oxynitride containing 4% nitrogen, D NO , is 3.42 × 10 -2 exp (-3.75 eV.kT) cm 2 /s

High activity of B during solid-phase epitaxy in a pre-amorphized layer formed by Ge ion implantation and deactivation during a subsequent thermal process

We have shown that ion-implanted boron (B) in an amorphous layer formed through Ge ion implantation becomes highly active during solid-phase epitaxy. The activated B concentration reaches about 10/sup 20/ cm/sup -3/ and is almost completely independent of the temperature. This active concentration corresponds to the solid solubility at 900/spl deg/C, hence the B becomes active at levels greater than the solid solubility below this temperature. This activated B was deactivated as a result of the subsequent thermal process in which the diffusion length reached about 10 nm. A low-resistance shallow junction can thus be realized in the low-temperature region provided we end the annealing before the onset of the rise in resistance.

Structural Analysis of Ag–In–Sb–Te Phase-Change Material

The Ag–In–Sb–Te system is widely used for phase-change discs such as compact disc rewritable (CD-RW) and rewritable digital versatile disc (DVD+RW). To clarify the effect of Ag and In in the Ag–In–Sb–Te system, we studied the local structure of Ag–In–Sb–Te phase-change material by extended X-ray absorption fine structure (EXAFS). The results suggest that the existence of Ag contributes to the thermal stability of amorphous marks and existence of In contributes to high-speed phase-change.

Diffusion of Boron, Phosphorus, Arsenic, and Antimony in Thermally Grown Silicon Dioxide

We studied the diffusion of dopant impurities, that is, ion-implanted boron, phosphorous, arsenic, and antimony in SiO 2 and determined the diffusivity of the impurities in SiO 2 using secondary ion mass spectrometry and a process simulator. We also revealed anomalous diffusion of the dopant impurities in SiO 2 .

Flat-band voltage shifts in p-MOS devices caused by carrier activation in p/sup +/-polycrystalline silicon and boron penetration

We found that the annealing time dependence of the flat-band voltage (V/sub FB/) shift of a p/sup +/-polysilicon gate MOS diode is attributed to the activation of boron in the polysilicon instead of the boron penetration through the gate SiO/sub 2/. We identified the process window for p/sup +/-polysilicon gate pMOSFETs taking into account that boron is sufficiently activated in polysilicon without penetrating through the gate SiO/sub 2/.

High activation of Sb during solid-phase epitaxy and deactivation during subsequent thermal process

Ion-implanted Sb is activated with higher concentrations than at thermal equilibrium during solid phase epitaxy, this Sb being deactivated at thermal equilibrium during the subsequent thermal process. It seems that Sb is trapped at the lattice sites at values above solid solubility during solid phase epitaxy and the diffusion of dopants degrades the resistance, as dopants begin to aggregate and deactivate. We showed that the onset of the increase in resistance is related to the diffusion length of Sb. By using a thermal process before deactivation, we could obtain shallow junctions with low resistance.

Boron Diffusion in Nitrided-Oxide Gate Dielectrics Leading to High Suppression of Boron Penetration in P-MOSFETs

Nitrided-oxide gate dielectrics have been proposed to suppress boron penetration in deep submicron metal-oxide-semiconductor field effect transistors (MOSFETs). However, few quantitative reports have been released on how nitrided oxides enlarge the permissible thermal budget. We evaluated the diffusivities of a nitrided oxide formed by annealing SiO2 in NO gas and demonstrated that this film enables us to use BF2+ for scaled devices. We also proposed a model depicting boron penetration through the nitrided-oxide layer.

Nitrogen Concentration Dependence on Boron Diffusion in Thin Silicon Oxynitrides Used for Metal‐Oxide‐Semiconductor Devices

The effect of nitrogen concentration on boron diffusion in silicon oxides (oxynitride) used for metal-oxide-semiconductor structures was investigated. The oxynitrides, which were formed by oxidizing thin, thermally grown nitrides, contained uniform amounts of nitrogen. The boron diffusion coefficients in the oxynitrides were determined, and experimental and simulated results were compared. The diffusion coefficients have an Arrhenius relationship to each concentration of nitrogen, and are smaller in higher nitrogen concentrations. A 25% concentration of nitrogen exhibited an oxynitride diffusion coefficient at least two orders smaller than that of SiO 2 . The higher the nitrogen concentration was, the larger the activation energy was. The diffusion coefficient data is useful for evaluating the boron penetration of various types of oxynitrides, including nitrided oxides. An empirical diffusion model is proposed in order to explain the experimental data qualitatively.

Diffusion coefficient of B in HfO/sub 2/

We implanted B ions in a 110-nm-thick HfO/sub 2/ layer, subjected the substrates to various thermal processes, and evaluated the diffusion coefficient by comparing experimental and numerical data. We found that the diffusion coefficient of B in HfO/sub 2/ is higher than that in SiO/sub 2/ by about four orders and almost the same as that in Si. Therefore, the penetration of B through this layer can be expected to be significant, making the use of a cover layer indispensable for p/sup +/ polycrystalline silicon gate devices.