Activation energy and spectroscopy of the growth of germanium films by ultraviolet laser-assisted chemical vapor deposition

Abstract

Emission and absorption spectroscopic studies of a reactor used to grow germanium thin films by photodissociating GeH4 at 248 nm with an excimer laser are described here. For every Ge or GeH (A→X) transition examined, the dependence of the emission line intensity on pump laser fluence was found to be quadratic, indicating that Ge and GeH have a common precursor which is itself produced by the simultaneous absorption of two 5-eV photons. This conclusion is supported by the known photochemistry of SiH4 and CH4 in the ultraviolet and the laser wavelength and intensity thresholds for the growth of Ge films. The short (∼2 μs) lifetime of GeH2 in the reactor suggests that the immediate precursor to Ge and GeH is the germyl radical, GeH3. The activation energy for Ge film growth in the temperature range 300≤T≤500 K has been measured to be 2.0±0.5 kcal/mole which suggests that the limiting mechanisms for the film growth rate are a gas-phase reaction and surface desorption of residual gases rather than surface diffusion. Radiation trapping on several Ge emission lines and absorption measurements at 422.6 nm indicate that the steady-state Ge number density in the reactor is ∼1012 cm−3 which is sufficient to account for the observed film growth rates. Spatial profiles of the atomic Ge and GeH emission from the reactor have been measured with a resolution of ∼100 μm.

Ab initio potential energy surfaces for both the ground (X̃ A1′) and excited (Ã A1″) electronic states of HGeCl and the absorption and emission spectra of HGeCl/DGeCl

“…[1][2][3][4][5][6][7][8][9] However, the detailed mechanism of such processes is still not fully understood due partly to the lack of definitive spectroscopic signatures. [1][2][3][4][5][6][7][8][9] However, the detailed mechanism of such processes is still not fully understood due partly to the lack of definitive spectroscopic signatures.…”

Ab initio calculation of the inversion barrier in the germyl radical

“…From a practical point of view, the latest interest in this species has been motivated by the fact that it occurs as an intermediate during chemical vapor deposition of germanium films [1]. From a practical point of view, the latest interest in this species has been motivated by the fact that it occurs as an intermediate during chemical vapor deposition of germanium films [1].…”

Study on growth processes of particles in germane radio frequency discharges using laser light scattering and scanning electron microscopic methods

“…2͑a͒ is the highest around the plasma/sheath boundary near the powered electrode and the spatial profile is very similar to that of emission intensity of Ge atoms, which indicates the spatial profile of radical production rates due to a quite short radiative lifetime (р1.3 ns) of the upper excited state of Ge atoms for the Ge 265 nm line. 22 As highly reactive species tend to have a spatial profile similar to that of their production rates, the profile similarity between the particle amount and emission intensity implies that highly reactive species, generated at a high rate, mainly contribute to the particle initial growth. Since, the initial growth rate of particles for GeH 4 is much higher than that for SiH 4 , the species responsible for Ge particle growth are expected to have a high reactivity and/or high production rate compared to those for Si particle growth.…”