Improvements for two established methods for plasma-density measurements have been developed: (a) microwave interferometry and (b) single Langmuir-probe technique. The new microwave interferometer design allows us to avoid a rigid waveguide as the reference line and therefore results in a high flexibility for the use at plasma chambers with different geometries. The system is operated at 35 GHz and has a bandwidth of 10 MHz. The cylindrical single Langmuir-probe system has been equipped with a new rf-suppression circuit. This allows the application of probes of nearly arbitrary geometrical dimensions in rf-driven plasmas. The circuit is simply mounted outside the vacuum chamber between the probe feedthrough and the dc circuit. The performance of these two developments has been demonstrated and comparative measurements of charge carrier densities in a conventional rf-driven plasma show good agreement between the two methods.
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An apparatus has been constructed to analyze the particle flux of positive ions on surfaces from dry etching reactors. The particle flux can emerge from a great variety of reactive ion etching systems or from reactive ion beam etching sources. The particle beam passes through a small orifice with a diameter of 100 μm. A differentially pumped quadrupole mass spectrometer with a specially designed ion transfer optics performs the energy analysis of positive ions. The energy range can be varied between 0 and 500 eV with a resolution of 1%. The angular distribution measurements of the particle flux are carried out varying the inclination of the mass analyzer by ±20° with the vertex lying centrally in the sampling orifice. The angular resolution is about 1°. Rotation of the source on top of the apparatus and translation over ±10 cm in xy direction and 15 cm in z direction perpendicular to it is provided in order to assure fully local resolution. The electrical properties of the orifice-ion optics system is discussed with respect to their influence on ion trajectories. The purpose of the apparatus is to provide data on particle fluxes relevant for microelectronic processing.
We have developed a novel dry etch tool LASSIE-standing for Large Area Source Supported Ion Etching-appropriate for the processing of substrate sizes of presently up to 600*400 mm2. The plasma is produced through an array of 4 inductively coupled plasma sources driven by a 13.56 MHz-generator. A second rf-generator serves for substrate biasing. Plasma diagnostic data suggest that LASSIE has strong capabilities for future large area etch applications avoiding several draw backs of conventional reactive ion etching (RIE) using parallel plate reactors. In particular we expect considerably higher etch speed since the plasma densities are roughly one order of magnitude higher than in conventional RIE. In addition processing will be more flexible and better controlled due to the decoupling of plasma densities and ion bombardment energies. An upscale with respect to the processing of wafer sizes larger than presently envisaged is easily achieved by the LASSIE concept
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