Ion energy distributions and optical emission spectra in NF3-based process chamber cleaning plasmas

Abstract

To minimize ion bombardment induced damage in NF3-based chamber cleaning plasmas, we have studied the effects of diluent gases and reactor pressure on ion energy distribution functions in NF3 plasmas. We have utilized plasma ion mass spectrometry, ion energy analysis, and optical emission spectroscopy in 25 mol % NF3 plasmas with argon, helium, and oxygen diluents. We have also compared the NF3-based plasma measurements to those of 50 mol % C2F6/O2 plasmas. We have demonstrated that diluting with helium and operating at higher pressures will reduce ion energies in NF3 plasmas while maintaining superior chamber cleaning performance. In addition, we have correlated the intensity ratio of specific argon emission lines to average ion energies at the grounded electrode. This correlation provides a practical diagnostics tool for further optimization work.

Rf discharge dissociative mode in NF3and SiH4

“…Rf discharge in NF 3 is widely used for cleaning technological chambers [1][2][3][4][5][6], etching silicon-containing materials [7][8][9][10][11][12][13][14][15][16] and plasma treatment of polymeric dielectrics [17]. This gas is of interest due to the following reasons.…”

“…Therefore NF 3 may present a more promising alternative to these gases. The discharges in NF 3 do not form polymer layers, and the lifetime of NF 3 molecules in atmosphere is comparatively small [6]. We will show below that NF 3 also possesses an additional advantage in the form of almost complete dissociation of NF 3 molecules under discharge conditions usually employed in technological processes.…”

“…However, the properties of rf capacitive discharge in NF 3 remain almost unknown until now. Paper [19] reports a single voltage-power characteristic registered at fixed gas pressure in the industrial etching system (GIR 100 made by Alcatel).…”

“…Paper [20] contains the measurements of the impedance and phase shift between rf current and voltage in different NF 3 /Ar mixtures in GEC Reference cell. In the same chamber the authors of [14] studied the effect of gas pressure on the power, impedance and phase shift in NF 3 mixtures with argon and some other gases. As we observe, the experiments in [14,19,20] were performed in asymmetric technological reactors.…”

“…As we observe, the experiments in [14,19,20] were performed in asymmetric technological reactors. Until now the available references do not contain the information on modes of burning and characteristics of the symmetric rf capacitive discharge in NF 3 .…”