buried power rail integration

**Buried Power Rail Integration** is the **detailed process engineering required to fabricate BPRs within the device substrate** — addressing the challenges of deep trench formation, dielectric isolation, metal fill, and connection to both transistors and the power delivery network. **Key Integration Challenges** - **Trench Aspect Ratio**: Deep, narrow trenches (>5:1 AR) must be etched without damaging adjacent active regions. - **Isolation**: Complete dielectric isolation prevents leakage between the metal rail and the doped substrate. - **Metal Fill**: Void-free fill of high-aspect-ratio trenches with low-resistance metals (Ru, W). - **Connection**: Reliable connection from BPR to S/D contacts (via contact-to-BPR vias). **Why It Matters** - **Parasitic Management**: BPR-to-transistor coupling must be minimized to avoid performance degradation. - **Yield**: BPR defects (voids, shorts to substrate) can kill all transistors along the power rail. - **Co-Development**: BPR integration must be co-developed with the transistor and BEOL modules. **BPR Integration** is **the engineering behind buried power** — solving the trench, isolation, fill, and connection challenges of embedding power rails in silicon.