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The TEL focus ring designated 380-T4.O (Tokyo Electron OEM part number 3D10-250442-31) is a circular, wafer-encircling consumable that installs in the electrostatic-chuck region of a Tokyo Electron 300 mm plasma etch process chamber. It sits concentrically around the production wafer, resting on the cathode assembly so that its inner bore frames the wafer edge and its upper surface forms a continuous, planar extension of the wafer plane. In doing so it carries the plasma sheath outward beyond the silicon, so that the reactive ion flux at the extreme edge of the wafer behaves as if it were striking material located several millimetres further out.
Focus rings of this class are among the most heavily worked consumables in any etch toolset. Because they live directly at the boundary between the wafer and the chamber hardware, they are continuously bombarded by energetic ions, exposed to aggressive fluorine- and chlorine-bearing chemistries, and cycled through large thermal swings every time RF power is struck and extinguished. The 380-T4.O is therefore a scheduled replacement item rather than a lifetime component, and its condition has a direct, measurable bearing on edge die yield.
The “E” suffix and “380” designation in the raw part name reflect TEL’s internal revision and configuration coding for the ring geometry and profile. ESCT Fab Support supplies this item as ES7099-036, a second-source, newly manufactured part built to match the form, fit and function of the original ring so that engineers can maintain plasma-edge performance without committing to single-source OEM procurement.
The focus ring does far more than physically surround the wafer. It is an active participant in shaping the plasma sheath, defining the electrical boundary of the etch field, and stabilising the thermal and gas environment at the wafer perimeter. Its principal functions include:
Focus rings for TEL 300 mm etch chambers are produced from process-matched materials selected for their plasma resistance, electrical character and freedom from yield-killing contaminants. Depending on the process step, rings in this family are commonly fabricated from high-purity silicon, silicon carbide or quartz, each chosen because it interacts predictably with the chamber chemistry rather than introducing foreign species.
The ring material must withstand sustained exposure to fluorine- and chlorine-based etch chemistries and continuous ion bombardment while eroding at a slow, uniform and predictable rate. Predictable erosion is the key requirement, it allows the ring to be qualified for a defined number of RF hours or wafer passes before its profile drifts out of specification.
Because the ring’s upper surface and inner bore define the geometry of the sheath at the wafer edge, flatness, bore concentricity, step height and surface finish must be held to tight tolerances. Even small departures from the qualified profile change the local electric field and shift edge etch results, so dimensional fidelity to the original 380-T4.O geometry is required.
A focus ring in good condition is invisible in the data; a worn or out-of-specification ring announces itself through edge-die failures and rising scrap. Because edge dies represent a meaningful fraction of the die count on a 300 mm wafer, focus-ring condition has an outsized effect on overall yield. The consequences of running a degraded ring include:
The dominant wear mechanism is steady sputter and chemical erosion of the ring’s upper surface and inner edge. As accumulated RF hours mount, the ring thins and its step height changes, gradually lowering the sheath at the wafer edge and pulling edge etch results outside the qualified window. This is normal, expected behaviour and is the reason the ring is treated as a planned-replacement consumable.
Repeated RF on/off cycling subjects the ring to thermal expansion and contraction. Over many cycles, or following a localised hot spot, micro-cracks can initiate and propagate, particularly in brittle ceramic and quartz variants. A fractured ring is an immediate source of large particles and lost plasma confinement and must be replaced without delay.
Etch by-products and polymer can accumulate on the ring surface, while ion bombardment roughens and pits it over time. The combination raises particle risk, can flake onto the wafer, and may create sites for micro-arcing that damage both the ring and adjacent hardware. Roughening also alters local secondary-electron behaviour and can subtly shift the edge process.
Focus-ring replacement is performed during scheduled preventive maintenance and demands strict cleanliness and careful handling, as the ring is brittle and any contamination it introduces lands directly on production wafers. The following sequence reflects good practice; always defer to your facility’s TEL maintenance procedure and safety protocols.
Focus rings are scheduled, high-frequency replacement items, which makes their supply chain a recurring cost and an availability risk. Sourcing ES7099-036 through ESCT Fab Support gives fabs and refurbishers a dependable alternative for keeping etch chambers in qualified condition without depending on a single OEM channel:
It surrounds the wafer at the chuck and extends the plasma sheath beyond the wafer edge, keeping ion trajectories vertical and the etch uniform across perimeter dies. It also confines the plasma, provides an RF return path and protects the cathode beneath it.
No. ES7099-036 is supplied as a second-source, newly manufactured OEM-compatible part. It is built to match the original ring to TEL OEM P/N 3D10-250442-31 in form, fit and function, but it is not an original Tokyo Electron OEM part and is not sold as one.
Replacement is typically driven by accumulated RF hours or wafer passes, supported by trends in edge-uniformity and particle data. Visible thinning, profile loss, cracking or rising edge-die failures all indicate the ring has reached end of life.
Rings in this family are produced from process-matched, high-purity materials such as silicon, silicon carbide or quartz, selected for plasma resistance, predictable erosion and low contamination. The correct material is matched to the specific TEL process step.
A new ring restores the qualified starting geometry and sheath condition, so edge results should return to baseline. As with any consumable change, run your standard qualification and particle wafers after installation to confirm the chamber is back within specification.
The current lead time is 4-5 weeks. Because focus rings are consumed on a regular cycle, we recommend ordering against your planned-maintenance schedule and holding suitable buffer stock to protect tool availability.
The TEL focus ring 380-T4.O (OEM P/N 3D10-250442-31), offered by ESCT Fab Support as ES7099-036, is a wafer-edge plasma confinement consumable that governs edge etch uniformity, sheath shaping, RF coupling and particle performance in Tokyo Electron 300 mm plasma etch chambers. Manufactured from process-matched, high-purity material and held to tight dimensional tolerances, it erodes predictably as a planned-replacement item and has a direct effect on edge-die yield. Supplied as a second-source new part with a 4-5 week lead time, it provides a cost-effective, well-supported route to keeping etch tools in qualified condition.
Disclaimer: This part is supplied by ESCT Fab Support as a new, OEM-compatible second-source component, verified to the form, fit and function of Tokyo Electron part number 3D10-250442-31. It is not an original OEM part and is not sold as one. It is not manufactured by, endorsed by, or affiliated with Tokyo Electron, and all manufacturer names and part numbers are quoted for identification and compatibility purposes only.
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