Integrated silicon grid ion extraction system for O2 processes

Abstract

A novel multibeamlet very low energy ion extraction optic technology avoiding cumbersome grid readjustment and thermal degradation of beam properties during a reactive process has been developed. In this approach anisotropically etched silicon grids ([100]-oriented Si wafers) are permanently integrated into a holder made of layered ceramics or micromachined AlN. The performance of such extraction systems having 300, 600, and 900 μm grid separation was tested in a 3 cm capacitively coupled rf-ion source. Stable system operation with use of oxygen has been achieved for an extended period of time (>100 h) for a total extraction voltage of 140 V which represents the maximum voltage to be applied for a grid separation of 0.3 mm. Additionally detailed Faraday-cup measurements of the extracted ion beam have been carried out for a total voltage range of 0–600 V, a vacuum chamber pressure of 1×10−4–1×10−3 mbar, rf-power levels of 10–170 W, a net-to-total voltage ratio of 0.5–1.0 and an axial magnetic field of up to 22 mT. For O2 an ion current density of 1.3 mA/cm2 could be extracted with ions having a mean energy of 60 eV. Even for energies as low as 50-eV current densities of 0.8 mA/cm2 could be achieved. In combination with the filamentless capacitively coupled rf source used, this approach has promise in various fields of materials research and processing such as ion beam assisted deposition of high-Tc YBaCuO layers and etching/modification of diamondlike, diamond and polymer thin films.