Performance Of A Radio Frequency Plasma Ion Source

A radio frequency, inductively coupled plasma (RFICP), gridded ion source was developed to produce energetic ion beams for use in ion assisted deposition (IAD) and plasma enhanced chemical vapor deposition. The source was designed to operate without filament and utilizes a single extraction grid. In addition, the RFICP ion source does not require an auxiliary electron neutralizer, such as a hot-filament or hollow cathode, since the flux of electrons extracted from the source is sufficient to neutralize the ion beam space charge, and eliminate space charge arcing in the chamber. The source was integrated in a Denton Vacuum electron-beam evaporator. The present study discusses its performance in IAD applications. Ion current density measurements with different grid geometries are presented, and mechanisms for ion and electron extraction are discussed. The combination of single grid ion optics and self-neutralization facilitates stable source operation with reactive gases over long periods of time, and results are presented to that effect. The system is used to deposit films typically used in antireflective coatings, TiO₂ and Ta₂O₅, which are characterized for optical properties, uniformity over wide deposition areas, and stability. Optical properties are correlated to plasma ion source parameters, and beam profile measurements to ion dose coverage area and film uniformity.