{
  "schema": "semiagora.process-simulation.v1",
  "experiment_id": "SA-PROC-METRO-ELLIPSOMETRY-001",
  "title": "Ellipsometry thickness fit replay",
  "execution_mode": "precomputed-only",
  "model_boundary": "Educational thin-film metrology replay. It illustrates fitting discipline and residual review; it is not a calibrated optical model, certified reference-material result, or qualified metrology report.",
  "lesson_route": "/learn/process-metrology",
  "simulation_route": "/simulations/process-ellipsometry-thickness-fit",
  "measurement_context": {
    "film_stack": "single transparent teaching film on silicon",
    "nominal_thickness_nm": 28,
    "observable": "psi_deg",
    "wavelength_nm": [400, 450, 500, 550, 600, 650, 700],
    "measured_psi_deg": [27.4, 29.1, 31.2, 33.0, 34.5, 35.6, 36.3]
  },
  "fit_candidates": [
    {
      "thickness_nm": 26.5,
      "model_psi_deg": [26.98, 28.77, 30.95, 32.83, 34.38, 35.52, 36.25],
      "residual_deg": [0.42, 0.33, 0.25, 0.17, 0.12, 0.08, 0.05],
      "mse": 0.092
    },
    {
      "thickness_nm": 27.8,
      "model_psi_deg": [27.37, 29.15, 31.18, 33.01, 34.46, 35.63, 36.29],
      "residual_deg": [0.03, -0.05, 0.02, -0.01, 0.04, -0.03, 0.01],
      "mse": 0.012
    },
    {
      "thickness_nm": 29.0,
      "model_psi_deg": [27.71, 29.35, 31.39, 33.14, 34.60, 35.66, 36.32],
      "residual_deg": [-0.31, -0.25, -0.19, -0.14, -0.10, -0.06, -0.02],
      "mse": 0.076
    }
  ],
  "derived_metrics": {
    "best_fit_thickness_nm": 27.8,
    "best_mse": 0.012,
    "next_best_delta_mse": 0.064,
    "teaching_confidence_interval_nm": "+/-0.8",
    "residual_span_deg": 0.08
  },
  "methods": [
    "Compare measured and candidate psi curves at the same wavelength samples.",
    "Select the candidate with the lowest mean squared residual.",
    "Report the residual span so users inspect the fit shape, not only the best thickness.",
    "Keep the optical-stack assumption attached to the fitted number."
  ],
  "limitations": [
    "No calibrated optical constants, roughness layer, backside reflection, depolarization, or covariance matrix is included.",
    "No qualified metrology, certified reference-material traceability, facility setting, wafer acceptance, or production-film claim is implied.",
    "Measured thickness signoff would require tool calibration, reference materials, uncertainty budget, and rights-clean raw data.",
    "This replay must not be used as a process recipe or film acceptance criterion."
  ],
  "sources": [
    {
      "label": "NIST Thin Film Reference Geometry Test Materials",
      "url": "https://www.nist.gov/programs-projects/thin-film-rgtms",
      "note": "Public NIST page describing thin-film reference materials and comparison of XRR and spectroscopic ellipsometry maps."
    },
    {
      "label": "NIST thin-film reference materials report",
      "url": "https://www.nist.gov/publications/semiconductor-measurement-technology-thin-film-reference-materials-development-final",
      "note": "Public NIST report context for reference materials used in semiconductor thin-film measurement technology."
    }
  ]
}