Negative ion measurements in electron cyclotron resonance plasmas

Summary form only given. Electrically confined negative ions are known as the precursors of particle formation in low pressure processing plasmas. The presence of negative ions can cause various negative aspects during the process: contamination of wafers, limitation of the manufacturing productivity and device reliability in microelectronics production. Various negative ions were detected in low-pressure, high-density Electron Cyclotron Resonance plasmas (H/sub 2/, O/sub 2/, CF/sub 4/, and Cl/sub 2/) by an Omegatron mass spectrometer. Preliminary results show H/sup -/ and H/sub 2//sup -/ in H/sub 2/ plasmas, O/sup -/ in O/sub 2/ plasmas, F/sup -/ and CF/sup -/ in CF/sub 4/ plasmas. Two other techniques were employed for the verifications of the observed negative ions: photo-detachment and a Langmuir probe in magnetized plasmas. (1) For photodetachment, a pulsed nitrogen laser (/spl sim/4 mJ, 50 nsec) was used to detach the electrons from H/sup $/and Cl/sup -/ and a cylindrical probe, positively biased above the plasma potential, was used to collect the additional electrons. (2) A Langmuir probe theory was developed and employed for various ECR plasmas (H/sub 2/, He, N/sub 2/, O/sub 2/, Ar and CF/sub 4/). The theory, adapted to magnetized, partially ionized, low temperature processing plasmas, was based on radial diffusion into the depleted flux tube unlike earlier work by Stangeby in fusion plasmas where Bohm diffusion dominates.