Grain boundary diffusion of phosphorus in polycrystalline silicon

Phosphorus and boron diffusion paths in polycrystalline silicon gate of a trench-type three-dimensional metal-oxide-semiconductor field effect transistor investigated by atom probe tomography

Abstract: The dopant (P and B) diffusion path in n- and p-types polycrystalline-Si gates of trench-type three-dimensional (3D) metal-oxide-semiconductor field-effect transistors (MOSFETs) were investigated using atom probe tomography, based on the annealing time dependence of the dopant distribution at 900 °C. Remarkable differences were observed between P and B diffusion behavior. In the initial stage of diffusion, P atoms diffuse into deeper regions from the implanted region along grain boundaries in the n-type polycrystalline-Si gate. With longer annealing times, segregation of P on the grain boundaries was observed; however, few P atoms were observed within the large grains or on the gate/gate oxide interface distant from grain boundaries. These results indicate that P atoms diffuse along grain boundaries much faster than through the bulk or along the gate/gate oxide interface. On the other hand, in the p-type polycrystalline-Si gate, segregation of B was observed only at the initial stage of diffusion. After f...

Scanning tunneling microscopy investigation of phosphorus-doped polycrystalline silicon films

Abstract: Scanning tunneling microscopy (STM) in air has been used to investigate the surface of highly phosphorus-doped polysilicon films produced by low pressure chemical vapour deposition (LPCVD). It has been found that, even when working in air, the technique gives detailed information about microroughness and mean grain size. Distinguishing between two different length scales, values for inter — and intra-grain roughness as a function of phosphorus doses are reported.

Rapid Activation of Phosphorous-Implanted Polycrystalline Si Thin Films on Glass Substrates Using Flash-Lamp Annealing

Abstract: Intense visible light irradiation was applied to phosphorous-implanted polycrystalline Si thin films on glass substrates, whichexhibited strong absorption features due to their amorphization by the application of a large implantation dose. Despite the shortpulsedurationofthevisiblelight,theuseofahigh-poweredandsubsequentlyintensifiedXearclampallowedforsignificantelectricalactivation even at near-ambient temperatures and above, surpassing the efficacy of conventional thermal activation processes. Usinga simple optical-thermal model, theoretical predictions indicate that the instantaneous temperatures of the phosphorous-implantedSi thin films reach approximately 680

Predoping effects of boron and phosphorous on arsenic diffusion along grain boundaries in polycrystalline silicon investigated by atom probe tomography

Abstract: The effect of P or B predoping on As diffusion in polycrystalline Si was investigated by atom probe tomography. In all samples, a high concentration of As was found at grain boundaries, indicating that such boundaries are the main diffusion path. However, As grain-boundary diffusion was suppressed in the B-doped sample and enhanced in the P-doped sample. In a sample codoped with both P and B, As diffusion was somewhat enhanced, indicating competition between the effects of the two dopants. The results suggest that As grain-boundary diffusion can be controlled by varying the local concentration of P or B.

Micro-structures of BF2 +- And As +-implanted polycrystalline silicon thin films of various thicknesses and heat treatments

Abstract: Characterization of annealed BF2+- and As+-doped polycrystalline silicon (polysilicon) films is presented. Effects of heat treatment, doping concentration, and thickness of film on the grain size and mobility of polysilicon films are investigated and discussed. By using transmission electron microscopy (TEM), it is found that the grain size, effective carrier concentration, and carrier mobility of a polysilicon thin film increases with increasing film thickness. Our results show that a high concentration of As dopant could enhance the recrystallization of the polysilicon films. Heavily As+-doped samples were seen to have a relatively larger grain size compared to the lightly doped film. The maximum grain size of about 278 nm can be realized in a polysilicon film with 150 nm in thickness. In contrast, the B dopant has a negligible effect on the recrystallization of polysilicon films. With increasing film thickness and thermal annealing temperature, a high performance polysilicon film with high mobility and grain size can be obtained.

The electrical properties of polycrystalline silicon films

Abstract: Boron doses of 1×1012–5×1015/cm2 were implanted at 60 keV into 1‐μm‐thick polysilicon films. After annealing at 1100 °C for 30 min, Hall and resistivity measurements were made over a temperature range −50–250 °C. It was found that as a function of doping concentration, the Hall mobility showed a minimum at about 2×1018/cm3 doping. The electrical activation energy was found to be about half the energy gap value of single‐crystalline silicon for lightly doped samples and decreased to less than 0.025 eV at a doping of 1×1019/cm3. The carrier concentration was very small at doping levels below 5×1017/cm3 and increased rapidly as the doping concentration was increased. At 1×1019/cm3 doping, the carrier concentration was about 90% of the doping concentration. A grain‐boundary model including the trapping states was proposed. Carrier concentration and mobility as a function of doping concentration and the mobility and resistivity as a function of temperature were calculated from the model. The theoretical and ex...

CXXXVIII. Concentration contours in grain boundary diffusion

Abstract: Formulae are obtained for the concentration in a poorly diffusing half space bisected by a thin well-diffusing slab, at different times after the edge of the half-space has been suddenly raised from zero to unit concentration. This represents a simplified model for studying ‘grain boundary’ diffusion of one metal into another. The problem also has obvious application to the study of heat flow in a poorly conducting solid with a metallic fin.

The analysis of grain boundary diffusion measurements

Abstract: Whipple's exact solution of the grain boundary diffusion problem is evaluated numerically and the results presented in graphical form suitable for immediate application to the commoner types of experimental measurement of D?, the grain boundary diffusion coefficient. This enables a detailed comparison to be made between the results obtained using the exact solution and the approximate but commonly employed Fisher solution. The most interesting result is that indiscriminate use of the Fisher equation may lead to anomalously high activation energies for grain boundary diffusion, especially in low angle boundaries. The Whipple solution is also compared with another exact solution due to Suzuoka, which employs a different surface condition from the one assumed by Whipple. For the sectioning method of measurements the two solutions will give nearly the same value of D?. This is a distinct advantage for this method over others, for the conditions prevailing at the surface in a grain boundary experiment are not easily controllable. Mathematical treatments of grain boundary diffusion by other authors are briefly mentioned. Most of these give results already contained in the Whipple solution.