Partial Via-First is a hybrid dual-damascene integration approach that partially etches the via before patterning and etching the trench — combining advantages of both via-first and trench-first approaches by controlling the via depth in the initial etch step.

Partial Via-First Process

• Via Litho: Pattern the via openings.
• Partial Via Etch: Etch only partway through the dielectric (e.g., 50-70% depth).
• Trench Litho: Pattern the trench openings.
• Trench + Via Completion: Etch the trench to its target depth while simultaneously completing the via etch.

Why It Matters

• Easier Via Protect: Partial (shallower) vias are easier to protect during trench lithography than full-depth vias.
• Better Control: The trench etch step completes the via — final via depth is set by the trench etch, improving uniformity.
• Reduced Defects: Lower aspect ratios during trench lithography reduce resist and etch defects.

Partial Via-First is the compromise approach — starting the via early (for alignment) but finishing it with the trench etch (for control).