SiH₃ Radical Density in Pulsed Silane Plasma

Abstract

The SiH3 radical density in pulsed silane discharge plasma was measured by infrared diode laser absorption spectroscopy (IRLAS) for three buffer gases and also as functions of the sample pressure and the pulse width. They were compared with the SiH and SiH2 radical densities. The growth rate of a-Si:H thin film was compared with the SiH3 radical density on various plasma conditions. These data were employed to discuss the contribution of SiH3 to a-Si:H thin-film growth.

Thin-Film Silicon –Growth Process and Solar Cell Application–

“…Steady-state densities of reactive species have been measured using various gas-phase diagnostic techniques [10][11][12][13][14][15][16] such as optical emission spectroscopy (OES), 14) laser-induced fluorescence (LIF), 12,15) infrared-laser-absorption spectroscopy (IRLAS), 10,11) and ultraviolet light-absorption spectroscopy (UVLAS). 16) Figure 3 shows the steadystate number densities of neutral chemical species including emissive species in the realistic SiH 4 and SiH 4 /H 2 plasmas used for preparing device-grade a-Si:H and c-Si:H. Figure 4 shows a linear relationship between the deposition rate of c-Si:H as well as that of a-Si:H and the Si à -emission intensity from the plasma, and also one-to-one correspondence between those deposition rates and number density of SiH 3 radicals in the plasma.…”

A modified molecular beam instrument for the imaging of radicals interacting with surfaces during plasma processing

“…This is based primarily on experimental evidence that SiH 3 is the dominant monosilicon radical in SiH 4 plasmas. 28,29 In addition, several studies on the gas phase reactions of SiH x radicals show that SiH and SiH 2 react rapidly with SiH 4 ͑the dominant species in typical rf SiH 4 plasmas 7 ͒, while SiH 3 does not. [30][31][32][33] SiH 3 does, however, react very rapidly with other radicals.…”

Modeling of a monosilane rf-discharge plasma

“…A more plausible explanation, in our opinion, is one in which the nonuniform heating of electrons is identified with the abrupt decrease in their density at the boundaries of the sheaths, which causes the conductivity of the plasma to drop sharply in these locations and therefore intensifies the Joule heat [IlL The flux of high-energy ions onto the surface of a substrate situated on the electrode can significantly influence the film growth processes. The poor quality of amorphous silicon fdms grown at high discharge power densities (> 0.1 W/cm 2) is customarily attributed to an increase in the ratio of the volume densities of the radicals SiH2/SiH 3 and the unfavorable surface kinetics of Sill 2 radicals from the standpoint of film quality [4,8,10]. Our calculations show (see Table 2) that large power densities are accompanied by substantial flows of ions with energies much greater than the binding energy of particles in the film (Si-Si ~ 3 eV; Si-H -~ 3 eV); such flows, of course, influence the surface kinetics, even though the mechanisms of this influence (other than the obvious possibility of etching of the film) are not altogether clear.…”