TL;DR
Etch non-uniformity is usually a dirty or eroded upper electrode, an RF match detuning, or a gas distribution change. Run a blanket film etch and map the result before changing any parameter.
What you might see
- radial etch depth variation on monitor wafers
- center-fast or edge-fast etch pattern
- CD uniformity failing wafer acceptance
- etch rate trending down over multiple runs
Likely causes
Upper electrode (showerhead) erosion or deposition changing gas distribution
RF match network detuned from ideal impedance, reducing plasma uniformity
Gas flow MFC calibration drift altering the actual etch chemistry ratio
Chamber wall polymer buildup changing the etch environment over time
Required tools
- Ellipsometer or profilometer for etch depth measurement
- MFC calibration kit
- RF power meter
- Showerhead inspection tools
Safety first
- Plasma etch systems use toxic and corrosive process gases including fluorine compounds, chlorine, and HBr. Follow site gas-safety procedures and confirm exhaust scrubber operation before opening any gas line.
- The chamber interior may be contaminated with etch by-products. Wear chemical-resistant gloves and eye protection when opening the chamber.
- Confirm the RF generator is locked out before accessing the match network or electrode components.
Procedure
- 1
Run a blanket oxide or silicon etch on a monitor wafer using the standard qualification recipe.[1]
- 2
Measure etch depth at 49 or 121 points and map the uniformity. Identify whether the pattern is center-fast, edge-fast, or asymmetric.
- 3
Review the RF match network position log. A match position at the edge of its travel range indicates an impedance shift that needs re-optimization.[1]
- 4
Check all gas flow MFCs for set-point vs. actual deviation. Recalibrate any line deviating more than 2%.
- 5
Inspect the upper electrode (showerhead) visually for erosion pitting or polymer deposits. Schedule a showerhead clean or replacement if the erosion depth approaches the replacement threshold.
- 6
Check the chamber wall condition. If the last wet-clean is beyond the maintenance interval, schedule a chamber clean.
- 7
Run the RF power calibration routine and verify forward power vs. set-point.
- 8
Run a qualification wafer after any repair and accept the chamber only when uniformity is within specification.
Sources
Lam Research Lam Kiyo / Vector / Versys Plasma Etch System general technical documentation, Lam Research
Lam Research plasma etch system general process qualification and hardware maintenance procedures (general)
More guides for Lam Research Lam Kiyo / Vector / Versys
How to reduce chamber particle contamination on a Lam Research Kiyo / Vector / Versys
Particle excursions are usually a polymer flaking event after missed chamber conditioning, a worn focus ring, or an o-ring shedding particles. Condition the chamber and inspect the focus ring.
How to troubleshoot plasma ignition failure on a Lam Research Kiyo / Vector / Versys
Ignition failures are most often a process gas interlock, an RF generator fault, or a match network impedance mismatch at low pressure. Check the gas interlocks and RF power delivery first.
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