Proposals for producing novel periodic structures by ion bombardment sputtering

It is proposed, and confirmed analytically that if multiple ion fluxes are incident simultaneously, all at the same oblique polar angle but at different azimuthal angles, on to a target then the individual ripple patterns generated by sputtering are superimposed to produce novel surface structures. It is also shown that single focused ion fluxes incident on to rotating targets can produce circular ripple patterns.     

Measurement of carbon sputtering yield by N ion beam and lifetime dependence of resulting foils on thickness

Carbon stripper foils with a higher nitrogen content were made by ion beam sputtering with reactive nitrogen gas. Such foils seem to be very useful as strippers for high-intensity heavy ion accelerators. To know further characteristics of the lifetime of such carbon foils, we have measured the sputtering yield of the carbon source material at a sputtering voltage of 4–15 kV and the lifetime dependence of such foils on thickness. Lifetime measurement was performed with a 3.2 MeV Ne⁺ ion beam. The sputtering yield on average showed 0.75 atoms/ion at over 9 kV sputtering voltage. The lifetime of the foils noticeably depends on the foil thickness, and the thickness range as practical stripper foil is to be around 15 to 33 μg/cm². Two foils made at 13 kV showed extremely long lifetimes of 6800 and 6000 mC/cm² at maximum and the foils made above 10 kV lived longer than about 900 mC/cm², which correspond to about 270 and 40 times longer than commercially available best foils. We measured the thickness ratio of nitrogen to carbon in each foil made at the different sputtering voltages and at the different irradiation stages (mC/cm²) by RBS method. We also inspected the structure of a nitrided carbon foil by transmission electron microscopy.     

A novel technique for fabrication of metallic structures on polyimide by selective electroless copper plating using ion implantation

The successful use of palladium ion implantation into polyimide to seed an electroless plated film of copper on the polyimide surface is reported. Polyimide (Hitachi PIX 3400) was implanted with palladium ions to doses of 1.5 × 10¹⁵ − 1.2 × 10¹⁷ ions cm⁻² using a MEVVA ion implanter. The implanted ions acted as sites for nucleation of copper film. A copper film was then deposited on implanted polyimide using a commercial electroless plating solution. The ion energy was kept low enough to facilitate a low critical ‘seed’ threshold dose that was measured to be 3.6× 10¹⁶ Pd ions cm⁻². Test patterns were made using polyimide to study the adaptability of this technique to form thick structures. Plated films were studied with optical microscopy, Rutherford Backscattering Spectrometry (RBS) and Profilometry. The adhesion of films was qualitatively assessed by a ‘scotch tape test’. The film growth (thickness) was observed to be linear with plating time. A higher implantation dose led to greater plating rates. The adhesion was found to improve with increasing dose.