Spatial profiles of reactive intermediates in rf silane discharges

Abstract

Spatial concentration profiles of ground-state SiH and electronically excited SiH* radicals are measured using laser-induced fluorescence and emission spectroscopy, respectively. The measurements are made in pure silane, as well as in mixtures with helium, hydrogen, and argon, in a capacitively coupled rf glow-discharge apparatus used for the deposition of a-Si:H. Low-power–low-depletion conditions are maintained throughout, whereas pressure is varied from 20 to 400 mTorr. Our observations indicate a close relationship between concentration profiles of the species and local electron energy distribution. We conclude that spatial concentration profiles represent stationary generation rates of the radicals. In the case of diluted silane the process is strongly influenced by diffusional transport of detected species to the deposition electrode. The dependence of this effect on dilution grade and buffer gas used is presented.

Heterogeneity in microcrystalline-transition state: Origin of Si-nucleation and microcrystallization at higher rf power from Ar-diluted SiH4 plasma

“…In addition to the regular process of electron impact dissociation of SiH 4 , 22 metastable state energy transfer from the noble gases would lead directly to increased dissociation and, thereby, contributes to the high density plasma and results in an increased deposition rate when SiH 4 is diluted with noble gases. For very high Ar dilution of SiH 4 plasma, very fast quenching of metastable Ar was observed by Mataras et al 23 from laser induced fluorescence measurements and by Sansonnens et al 24 with time modulated optical emission and absorption spectroscopy during rf power modulation period. Thus, for extremely high Ar dilution of SiH 4 , an ample contribution of Ar* in SiH 4 decomposition, via very fast quenching of metastable states may result in a higher yield of SiH n radicals from the source gas.…”

Effect of frequency in the deposition of microcrystalline silicon from silane discharges

“…13,15 The setup used for recording emission intensities of SiH (A 2 ⌬→X 2 ⌸) as well as ␣ and ␤ Balmer lines of atomic hydrogen, has been described in detail elsewhere. 16,17 Mass spectrometric measurements have been performed using a Hidden analytical ͑HAL 301͒ quadrupole mass spectrometer connected at the exhaust port of the reactor. The gas sampled through a variable leak valve in a small chamber has been analyzed after 70 eV electron impact ionization.…”

Electrical and structural properties of nano-crystalline silicon intrinsic layers for nano-crystalline silicon solar cells prepared by very high frequency plasma chemical vapor deposition

“…Since understanding of the plasma process is critical for obtaining the required film properties, it is necessary to diagnose the plasma during the deposition process. Several diagnostic techniques such as mass spectrometry [15], laser-induced fluorescence spectroscopy [16], optical emission spectroscopy (OES) [17], Langmuir probe [18] and reflection high-energy electron diffraction [19] have been used to investigate the plasma and the precursors involved during deposition. Among these, OES is one of the predominant tools to investigate the in situ plasma process due to its simple setup, minimal influence on the plasma and it provides valuable information about the film forming precursors and radicals present in the plasma.…”