Power network design and analysis of 3D-ICs is a major challenge due to the complex nature and large size of the power network. In addition, designers must deal with the complexity of routing power through the interposer, multiple dies, through-silicon vias (TSVs), and through-dielectric vias (TDVs).
Cadence’s Integrity 3D-IC Platform and Voltus IC Power Integrity Solution provide a fully integrated solution for early planning and analysis of 3D-IC power networks, 3D-IC chip-centric power integrity signoff, and hierarchical methods that significantly improve capacity and performance of power integrity (PI) signoff while maintaining a very high level of accuracy at signoff. This blog summarizes the typical design challenges faced by today’s 3D-IC designers, as discussed in our recent webinar, “Addressing 3D-IC Power Integrity Design Challenges.” Please click here to view the full webinar.

Major Trends in Advanced Chip Design

From chips to chiplets, stacked die, 3D-ICs, and more, three major trends are impacting advanced semiconductor packaging design. The first is heterogenous integration, which we define as a disaggregated approach to designing systems on chip (SoCs) from multiple chiplets. This approach is similar to system-in-package (SiP) design, except that instead of integrating multiple bare die – including 3D stacking – on a single substrate, multiple IPs are integrated in the form of chiplets on a single substrate.

The second major trend is around new silicon manufacturing techniques that leverage silicon vias (TSVs) and high-density fanout RDL. These advancements mean that silicon is becoming a more attractive material for packaging, especially when high bandwidth and form factor become key attributes in the end design. This brings new design and verification challenges to most packaging engineers who typically work with organic and ceramic substrate materials.

Finally, on the ecosystem side, all the large semiconductor foundries now offer their own versions of advanced packaging. This brings new ways of supporting design teams with technologies like reference flows and PDKs, concepts that have typically been lacking in the packaging community. Cadence has worked with many of the leading foundries and outsourced semiconductor assembly and test facilities (OSATs) to develop multi-chip(let) packaging reference flows and package assembly design kits. The downside is that, with the time restrictions designers are under today, there isn’t enough time to simulate the details of these flows and PDKs further.

For those who must make the best electro/thermal/physical decisions to achieve the best power/performance/area/cost (PPAC), factors can include accurate die size estimations, thermal feasibility, die-to-die interconnect planning, interposer planning (silicon/organic), front-to-front and front-to-back (F2F/F2B) planning, layer stack and electromigration/ IR drop (EMIR)/TSV planning, IO bandwidth feasibility, and system-level architecture selection.

3D-IC Power Network Design and Analysis

The key to success in 3D-IC design is early power integrity planning and analysis. Cadence’s Integrity 3D-IC platform is a high-capacity 3D-IC platform that enables 3D design planning, implementation, and system analysis in a single, unified cockpit. Cadence’s Voltus IC Power Integrity Solution is a comprehensive full chip electromigration, IR drop, and power analysis solution. With its fully distributed architecture and hierarchical analysis capabilities, Voltus provides very fast analysis and has the capacity to handle the largest designs in the industry. Typically, 3D-IC PDN design and analysis is performed in four phases, as shown in Figure 1.

Phase 1 - Perform early power delivery network (PDN) exploration with each fabric’s PDN cascaded in system PI with early circuit models.

Phase 2 – Plan 3D-IC PDNs in Cadence’s Integrity 3D-IC platform, including micro bumps, TSVs, and through dielectric vias (TDVs), power grid synthesis for dies, and early rail analysis and optimization.

Phase 3 – Perform full chip-centric signoff in Voltus with detailed die, interposer, and package models, including chip die models, while keeping some dies flat.

Phase 4 – Perform full system-level signoff with Cadence’s Sigrity SystemPI using detailed extracted package models from Sigrity XtractIM, board models from Sigrity PowerSI or Clarity 3D Solver, interposer models from XtractIM or Voltus, and chip power models from Voltus.

Figure 1. 3D-IC PDN design and analysis phases

3D-IC Chip-Centric Signoff

The integration of Integrity 3D-IC and Voltus enables chip-centric early analysis and signoff. Figure 2 and Figure 3 highlight the chip centric early PI optimization and signoff flows. In early analysis, the on-chip power networks are synthesized, and the micro bumps and TSVs can be placed and optimized. In the signoff stage, all the detailed design data is used for power analysis, and detailed models are extracted and used for package, interposer, and on-die power networks.

Figure 2. Early chip-centric PI analysis and optimization flow

Figure 3. Chip-centric 3D-IC PI signoff

Hierarchical 3D-IC PI Analysis

To improve the capacity and performance of 3D-IC PI analysis, Voltus enables hierarchical analysis using chiplet models. Chiplet models can be reduced chip models in spice format or more accurate xPGV models which are highly accurate proprietary models generated by Voltus. With xPGV models, the hierarchical PI analysis has almost the same accuracy as flat analysis but offers 10X or higher benefit in runtime and memory requirements.

Conclusion

This blog has highlighted the major design trends enabled by advanced 3D packaging and the design challenges arising from these advancements. The design of power delivery networks is one of these major challenges. We have discussed Cadence solutions to overcome this PI challenge. To learn more, view our recent webinar, "Addressing 3D-IC Power Integrity Design Challenges" and visit the Voltus web page.

This blog introduces the new Voltus-XFi Custom Power Integrity Solution, a transistor-level EM-IR tool that enables designers to complete comprehensive analysis and debugging easily and quickly.(read more)

DFT (Design for testing) Engineer: 4-6 years of experience Experience with Synopsys Toolset is mandatory. Scan insertion, Debug DRC, ATPG patterns Gate Level Simulation ( timing and no-timing) Knowledge in P1500 and JTAG is an advantage. Knowledge in MBIST is an advantage. Phy