baseline establishment

Baseline establishment is the process of defining the reference performance level for a manufacturing process by collecting and analyzing data under known-good, stable conditions. This baseline serves as the benchmark against which all future process performance is compared — enabling detection of drift, degradation, or improvement.

Why Baselines Are Essential

• Without a baseline, there is no way to determine whether the process is running normally or has drifted.
• Baselines define what "good" looks like — they provide the control limits and target values that SPC (Statistical Process Control) charts use.
• They enable quantitative decision-making: is a measured CD of 28.5 nm acceptable? Only the baseline can answer that question.

How to Establish a Baseline

• Stable Process: Ensure the process is running in a stable, controlled state before collecting baseline data. Do not baseline during startup, troubleshooting, or after a recipe change.
• Sufficient Data: Collect enough data points to capture the natural variation of the process. Typically 20–30 consecutive lots or 50+ measurements over a representative time period.
• Representative Conditions: Data should cover normal operating variations — different lots, different times of day, different operators (if applicable), before and after PMs.
• Statistical Analysis: Calculate mean, standard deviation, Cp/Cpk (process capability indices), and establish control limits (typically mean ± 3σ).

What Gets Baselined

• Etch: Etch rate, uniformity, selectivity, CD, sidewall angle.
• Deposition: Film thickness, uniformity, stress, refractive index, composition.
• Lithography: CD, overlay, focus, dose.
• CMP: Removal rate, uniformity, dishing, erosion.
• Implant: Dose, energy, uniformity.
• Metrology: Tool-to-tool offsets, gauge capability.

Baseline Maintenance

• Baselines are not permanent — they must be updated when:
• Process recipes are intentionally changed.
• New materials or consumables are introduced.
• Equipment undergoes major upgrade or modification.
• Process improvement initiatives produce a new, better operating point.
• Rebaselining follows the same data collection and analysis process as initial baseline establishment.

Baseline establishment is the foundation of all process control — without a well-defined baseline, SPC charts are meaningless and process excursions cannot be reliably detected.