design for manufacturability

**Design for Manufacturability (DFM)** — design practices and rules that ensure chip layouts can be reliably fabricated with high yield, bridging the gap between design and manufacturing. **Why DFM?** - A design that is "correct" in simulation may be unfabricable or have low yield - Process variability increases dramatically at advanced nodes - DFM rules ensure robust manufacturing across process windows **Key DFM Practices** - **Recommended Rules** (beyond minimum DRC): Wider wires, larger spaces where possible. Improves yield without area penalty in non-critical regions - **Redundant Vias**: Multiple vias at each connection point to survive single-via failures - **Dummy Fill**: Add non-functional metal/poly patterns to maintain uniform density for CMP planarity - **Restricted Design Rules**: Limit layout to regular, grid-based patterns that lithography can print reliably - **OPC (Optical Proximity Correction)**: Modify mask shapes to pre-compensate for optical distortion - **SRAF (Sub-Resolution Assist Features)**: Small mask features that improve printability of main features **DFM Flow** 1. Design rule check (DRC) — hard constraints 2. DFM check — recommended rules for yield 3. OPC and mask synthesis 4. Lithography simulation verification **DFM** is the discipline that translates theoretical designs into products that can actually be manufactured profitably at scale.