Multipolar magnetic field structures for the scaling-up of high density plasmas excited in the dc to microwave frequency range and applicable to sputtering and chemical processing

Multipolar magnetic fields, used for the production of large areas of low pressure, high density plasmas at electron cyclotron resonance, can also be employed favourably to scale-up plasma sources at any given excitation frequency. Since fast electrons responsible for plasma excitation undergo a drift motion perpendicular to the static magnetic field of a multipolar structure, plasma production along such a structure will be uniform when the amplitude of the electric field. which accelerates the electrons, is constant along the structure and the loss of energetic electrons al the extremities of the magnets is avoided by closing the magnetic structures onto themselves according to magnetron-like configurations. The limitations to the scaling-up of sources are derived in terms of the wave propagation, wavelength, source dimensions and mean free path of the fast electrons. Other requirements in the process scale-up concern the uniform distribution of process parameters, such as gas feeding, pumping, substrate biasing and substrate heating. The use of three-dimensional magnetron structures satisfies the explicit requirements, in particular the distribution of gas supply and pumping through the excitation structure. Two examples of novel reactor configuration, designed for chemical processing and sputtering, illustrate the new concepts developed in this work.