PWQ (Process Window Qualification) is a lithographic qualification methodology that uses FEM data and electrical test results to validate that a patterning process has sufficient margin — combining optical (CD-based) and electrical (device performance) process windows to ensure manufacturability.

PWQ Methodology

• FEM Wafers: Expose FEM wafers with systematic focus/dose variation across the wafer.
• Metrology: Measure CD, profile, and overlay at each focus/dose setting.
• Electrical Test: Probe the FEM wafers for electrical functionality (Vth, leakage, drive current) at each setting.
• Intersection: The electrical process window (where devices work) overlaps with the optical process window.

Why It Matters

• Correlation: CD specs alone may not guarantee electrical performance — PWQ validates the connection.
• Safety Margin: PWQ quantifies the actual margin between the operating point and the electrical failure boundary.
• Qualification: PWQ is the standard method for qualifying new technology nodes, mask sets, and process changes.

PWQ is proving it works electrically — validating the lithographic process window against actual device performance, not just CD specifications.