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A new electron cyclotron resonance (ECR) ion source has been developed in the laboratory. The ECR condition at 2.45 GHz is obtained in a multicusp arrangement using a set of four parallelepiped-shaped SmCo magnets regularly spaced around a cylindrical ionization chamber 50 mm in diameter and 50 mm in height. The electromagnetic cavity is made of a shielded quarter-wavelength Lecher line resonator coaxially coupled to the microwave generator through an excitation loop antenna and a SMA-type connector. The extracted argon ion beam current density has been measured for different excitation modes fixed by the loop antenna orientation. A current density of 1 mA/cm2 has been reached with an incident microwave power of 110 W and a chamber pressure of 9×10−3 mbar. The small dimensions of this ion source and its performance allow to use it not only in applications such as ion beam processing and cleaning or surface treatments in advanced microelectronics, but also as a neutralizer for ion deposition applications.

In our argon, oxygen, or nitrogen broad beam ion source, 80 mm in diameter, which is either an electrostatic reflex ion source, or a magnetic and electrostatic reflex ion source, the hot filament has been replaced by a carefully optimized microwave plasma (MP) cathode under the electron cyclotron resonance condition. Different geometries of antennae in which the microwave transverse electric field is more or less favored have been tested. A major improvement was obtained when a dc polarization of these antennae was superimposed onto the microwave field, allowing a fine tuning via the sheath thickness adjustment. Registered cathode currents under various conditions of pressure of neutrals, microwave power, and polarization voltage have shown a gain of a factor of 3 relative to the previous case where the single disk antenna was at a floating potential. Best results with argon gas at a pressure of 3×10−2 mbar were obtained with a spear-head shaped antenna fed at a microwave power of 50 W and polarized at 26 V. Extracted ion beam current densities as high as 5 mA/cm2 resulted from these different MP cathode improvements. Moreover, we have shown that the internal electronic tuning of the source can advantageously replace the traditional external tuning.

The demand has increased for a high-current, long lifetime ion source in various fields of application. The present work concerning the production of atomic hydrogen ions H+ in competition with molecular ions H+2 has been essentially motivated by recent trends in the field of passivation of silicon [V. Le Thanh, M. Eddrief, and C. A. Sébenne, Appl. Phys. Lett. 64, 3308 (1994)]. For a given low neutral energy, passivation with a neutral atomic beam H instead of H2 is preferred. The most straightforward method to produce the neutral beams is by the extraction of low energy atomic ions, and neutralization by electron capture. We have thus developed an electron cyclotron resonance coaxial hydrogen ion source that produces a 30-mm-diam ion beam, is operated with a microwave power in the range of 50–130 W, and has a pressure of neutrals in the range of 6×10−4–4×10−3 mbar. We have compared the proportion of extracted H+ and H+2 ions with the two principal parameters of the plasma: the pressure of neutrals and microwave injected power. These parameters have been optimized for the production of an 83% atomic ion beam.

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