An ionized
physical vapor deposition apparatus (10, 10a, 10b) is provided with an RF element, preferably a
helical coil (30), that surrounds space (11) within a
vacuum chamber (12) between a target (16) and a substrate holder (14). RF energy, preferably at about 2 MHz or elsewhere in the 0.1 to 60 MHz range, is coupled into the space to form a secondary
plasma (29) in a volume (26) of the space between the substrate holder and the main
plasma that is adjacent the target. The secondary
plasma ionizes sputtered material which is then attracted toward a substrate (15) on the support by a bias on the substrate and / or by an axial
magnetic field to impart directionality to the moving ionized sputtered particles to render them perpendicular to the substrate at incidence, so as to coat the bottoms of narrow high
aspect ratio features on the substrate. A window (60) of
dielectric material such as
quartz, either in the wall of the chamber or inside the chamber, or insulation on the coil, protects the coil from adverse interaction with plasma. Shields (100, 200, 300) between the space and the
dielectric material prevent sputtered particles
coating the
dielectric material. The shields are partitioned or slotted to prevent induced currents in the shields. The shields may be biased to control
contamination and may be commonly or individually biased to optimize the uniformity of
coating on the substrate and the directionality of the flux of ionized material at the substrate. The shield may be formed of a plurality of angled segments (302) that are spaced to facilitate communication of a secondary RF plasma from adjacent the window to the volume of the chamber where the sputtered material is ionized, with the sections angled and spaced to shadow at least most of the target from the window. Alternatively,
electrically conductive shield (100) may be provided in close proximity to the window or insulation.