Toroidal Plasma Source

A toroidal plasma source generates plasma in a closed, ring-shaped loop using transformer-coupled induction rather than a simple coil-over-chamber or parallel-plate arrangement — a geometry chosen specifically to sustain a high-density, low-contamination plasma without the coil or electrode sitting directly inside the chamber where it could erode and contaminate the process.

Process needs high-density plasma with minimal source-hardware contamination risk
A coil or electrode exposed inside the chamber can erode into the process
Toroidal source mechanism
Transformer-coupled induction
Current induced in a closed ring-shaped plasma loop, like a transformer secondary
No internal electrode exposed to plasma
Source hardware sits outside the plasma-contact region
High-density, low-contamination plasma sustained
No eroding source hardware directly facing the wafer

The transformer analogy is literal here, and it's exactly what lets the toroidal source avoid putting an electrode or coil inside the contaminating region of the chamber. A toroidal plasma source works like a transformer where the plasma itself forms the secondary winding — current is induced into the closed, ring-shaped plasma current loop from an external primary winding, without that primary ever being directly exposed to the plasma or process chemistry. That's a meaningful difference from a standard ICP coil mounted directly above the chamber, which does sit close to (though usually outside) the plasma-exposed volume.

Toroidal Plasma Source — Transformer-Coupled, Ring-Shaped plasma itself acts as the transformer's secondary winding Transformer-coupled ring plasma closed plasma ring — "secondary" primary winding — induces current, stays outside plasma no electrode or coil sits directly inside the process-exposed region avoiding an eroding internal source keeps metal/particle contamination out of sensitive processes

Avoiding an internal, eroding source component matters most in processes where even trace metal contamination from source hardware is unacceptable, since a toroidal source has nothing exposed inside the plasma that can sputter or flake into it. A conventional electrode or coil positioned where it contacts or sits very close to the plasma can slowly erode under ion bombardment, introducing trace metal contamination into the process; a toroidal source's closed-loop design keeps the actual current-carrying hardware outside that contaminating zone entirely, which is specifically valuable for remote-plasma-style applications — resist strip, surface cleaning — where metal contamination from the source itself would be a real yield risk.

A toroidal plasma source solves the same basic problem as a remote plasma source — generating reactive plasma species without risking contamination from source hardware exposed to the process — through a distinctly different, transformer-coupled mechanism that keeps every current-carrying component outside the plasma-contact region entirely.

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