Mass and energy selected ion beam for deposition and ion induced surface modifications

A mass and energy selected ion beam source, differentially pumped for ultrahigh vacuum (UHV) applications, was constructed and successfully tested. Ions with a mass up to 2048 amu and with energies of 5–500 eV can be selected from a Penning discharge chamber by a quadrupole massfilter and an electrostatic lens system. The ion gun is operated in combination with a VG ESCALAB spectrometer for x‐ray photoelectron spectroscopy and diffraction working at a base pressure in the 10⁻¹¹ mbar range. Two applications of low energy ion bombardment are discussed in this article: etching of PMMA with 5 eV Ar⁺ ions, and deposition of a‐C:H films on silicon. Ar⁺ ions at very low energies can react with a PMMA surface by a charge exchange reaction leading to a breakup of chemical bonds and to the preferential etching of oxygen. By depositing CH_x ions (x=3,4) on a silicon surface under UHV conditions an oriented SiC layer is formed upon annealing at 800 °C. The ion beam was characterized with respect to mass and energy resolution and beam spreading for different ion energies.