Lesson 4 – Zernike Terms & Wave Maps

What You Will Learn

• Identify common Zernike modes on 2D wave maps
• Relate 3D topography to symmetric vs. asymmetric process errors
• Use Zernike decomposition to separate tilt, power, astigmatism, and HOAs
• Correlate machine forces/speeds/ratios with Zernike signatures
• Build a diagnostic checklist before changing parameters

Metrology First

Ensuring good metrology is essential—test plates and objectives all have error. Confirm calibration and alignment before attributing signatures to process. Use both 2D/3D wave maps for a complete view.

Applying Zernike Terms

Use Zernike polynomials to classify and quantify form contributions: remove piston/tilt/power, then evaluate astigmatism and higher order terms. Symmetric terms often track dwell or pressure distribution; asymmetric terms often implicate fixturing, tool runout, or transport nonuniformities.

From Maps to Actions

Link signatures to causes: e.g., zonal dwell errors, pad compliance, slurry starvation, thermal gradients, or spindle misalignment. Adjust in small, logged steps and re‑measure.