ICP Source-Coil Assembly

ICP source coils come in planar and helical geometries, and the choice between them shapes exactly how the induced electric field couples into the plasma — a geometry decision that directly affects plasma uniformity and density profile across the chamber, not just an arbitrary mechanical layout choice.

A planar coil's radial symmetry is what makes it the default choice for uniform, wafer-scale plasma processing. Mounted flat above the chamber, concentric with the wafer below, a planar coil's induced field naturally respects the same radial symmetry the wafer itself has — producing a plasma density profile that, with proper tuning, maps reasonably evenly across a circular wafer, which is exactly the uniformity most etch and deposition processes are trying to achieve.

Helical geometry remains relevant specifically where chamber constraints or field-profile needs favor a different coupling pattern than a flat planar coil naturally produces. Wrapping the coil around the chamber's cylindrical sidewall rather than flat above it changes how the induced field couples into the plasma volume, which can be the better choice for certain chamber form factors or process requirements where a planar coil's specific field profile isn't the ideal fit — the two geometries aren't ranked better-or-worse, they're matched to different chamber designs and uniformity goals.

Planar and helical ICP source-coil geometries both induce the same basic plasma-generating electric field, and the choice between them is a real engineering decision about which resulting field pattern best serves a specific chamber's uniformity and process requirements.