Mass spectrometric determination of the percent dissociation of a high-density chlorine plasma

Abstract

Recent computer modeling of high-density chlorine plasmas has indicated that the gas is highly dissociated. This important prediction has only been recently confirmed by optical measurements, which require either external or internal calibration. Unfortunately, these optical techniques cannot readily be applied to the more chemically complex multicomponent plasmas commonly used in real processing. Using a new mass spectrometric method capable of detecting the local concentrations of both atomic and molecular atomic species within a plasma, a percent molecular dissociation of >85% has been measured in an electron cyclotron resonance chlorine plasma at low pressures.

Ion-enhanced chemical etching of ZrO2 in a chlorine discharge

“…33 At 3 mTorr and 700 W, we measured approximately 60% dissociation of Cl 2 by QMS, in good agreement with several other experimental works 21,34,35 and modeling studies. The QMS sampling head has a magnetic shielding to shield the magnetic field up to 1000 G. A 100 m orifice on the sampling head was placed atop the etched ZrO 2 sample, through which we sampled either ionic species directly from the plasma or repelled ions and ionized the neutral species with energetic electrons ͑70 eV͒ for detection.…”

Chlorine plasma and polysilicon etch characterization in an inductively coupled plasma etch reactor

“…On the other hand, the larger diffusion length at lower pressures leads to an increase in the ion loss rate to the reactor walls, which necessitates an increase in the electron average energy to sustain the plasma. The increase in T e at low pressures is also facilitated by an increase in the gas dissociation (larger Cl/Cl 2 ratio) because Cl has a larger ionization potential [31,36,37].…”