Gotowa bibliografia na temat „Plasma Chemistry - SiH4”

The rapid and uniform growth of hydrogenated silicon (Si:H) films is essential for the manufacturing of future semiconductor devices; therefore, Si:H films are mainly deposited using SiH4-based plasmas. An increase in the pressure of the mixture gas has been demonstrated to increase the deposition rate in the SiH4-based plasmas. The fact that SiH4 more efficiently generates Si2H6 at higher gas pressures requires a theoretical investigation of the reactivity of Si2H6 on various surfaces. Therefore, we conducted first-principles density functional theory (DFT) calculations to understand the surface reactivity of Si2H6 on both hydrogenated (H-covered) Si(001) and Si(111) surfaces. The reactivity of Si2H6 molecules on hydrogenated Si surfaces was more energetically favorable than on clean Si surfaces. We also found that the hydrogenated Si(111) surface is the most efficient surface because the dissociation of Si2H6 on the hydrogenated Si(111) surface are thermodynamically and kinetically more favorable than those on the hydrogenated Si(001) surface. Finally, we simulated the SiH4/He capacitively coupled plasma (CCP) discharges for Si:H films deposition.

In this study, the effect of dielectric elements on plasma radial uniformity was analyzed for a 300 mm wafer process in a capacitively coupled plasma deposition reactor. Based on a two-dimensional self-consistent fluid model, numerical simulations were performed for SiH4/He discharges at 1200 Pa and at the radio frequency of 13.56 MHz. Although in current plasma processes the wafer is often coated with non-conducting films and placed on a ceramic substrate, related materials have not been analyzed. Therefore, the plasma characteristics were studied in depth by changing the wafer material from silicon to quartz, the electrode material from aluminum to aluminum nitride, and the sidewall material from quartz to perfect dielectric. It was demonstrated that dielectric elements with a lower dielectric constant modify the spatial distributions of plasma parameters. In spite of the thinness of the wafer, as the dielectric constant of the wafer decreases, the electric field at the wafer edge becomes weaker owing to the stronger surface-charging effect. This gives rise to the relatively lower density of reactive species such as SiH2+, Si+, He*, and SiH3 near the wafer edge. In addition, radially uniform plasma was induced by the perfect dielectric sidewall, regardless of the dielectric constant of the wafer. This modification occurred because the radial positions of the peak values of the plasma parameters were moved away from the wafer edge. Therefore, the uniform distribution of the plasma density could be largely achieved by the optimal combination of dielectric elements.

Nanocrystalline Si films were prepared with a RF-PECVD system using different SiH4/H2 ratios, plasma powers, substrate temperatures and annealing conditions. The film's intrinsic stress was characterized in relation to the crystallization fraction. Results show that an increasing H2 gas ratio, plasma power or substrate temperature can shift the growth mechanism across a transition point, past which nanocrystalline Si is dominant in the film structure. The film's intrinsic stress normally peaks during this transition region. Different mechanisms of stress formation and relaxation during film growth were discussed, including ion bombardment effects, hydrogen induced bond-reconstruction and nanocomposite effects (nanocrystals embedded in an amorphous Si matrix). A three-parameter schematic plot has been proposed which is based on the results obtained. The film structure and stress are presented in relation to SiH4 gas ratio, plasma power and temperature.