Enhancing Power Reliability Through Design-Stage Layout Optimization

As integrated circuit (IC) designs continue to scale, the demand for efficient power management, performance optimization and reliable physical layout modification grows more critical. Meeting these power, performance and area (PPA) targets is essential for ensuring that IC designs operate effectively at advanced process nodes. One of the main challenges for design and verification engineers is how to address issues like IR drop and electromigration (EMIR) early in the design process without compromising performance and area goals.

This is where a shift-left approach to power grid optimization can make a significant difference. By implementing design-stage layout modifications, designers can proactively tackle power management issues, enhancing reliability and overall PPA metrics. This strategy not only benefits engineering teams but also delivers substantial business advantages by reducing rework, lowering costs and helping design teams achieve faster time to market.

The need for design-stage layout modifications

In any IC design, maintaining an optimal power distribution network is a fundamental requirement. Challenges such as IR drop and electromigration (EM) can significantly impact an IC’s reliability and performance (figure 1). Traditional approaches to address these issues tend to be reactive, with modifications and adjustments taking place during signoff verification stages. Unfortunately, this reactive method can result in longer design cycles, delayed schedules and higher costs.

Fig. 1: EM can create short circuits between two interconnects through the development of hillocks, or an open circuit through the creation of voids.

Shifting left—addressing power grid optimizations during the design implementation stage rather than waiting until signoff—allows design teams to anticipate and mitigate issues like IR drop and EM early in the process. This shift-left methodology supports the integration of correct-by-construction layout enhancements, resulting in a smoother design flow and improved outcomes.

Key layout modification techniques

Modern layout modification tools, like Calibre DesignEnhancer, provide automated solutions to address specific power management and physical layout challenges. These capabilities are tailored to tackle issues like IR drop and EM without impacting performance and area and are built to work seamlessly within place and route (P&R) and custom/analog design flows (figure 2).

Fig. 2: The Calibre DesignEnhancer flow enables design teams to quickly and easily back-annotate their IC design layouts for signoff analysis.

Calibre DesignEnhancer leverages foundry-preferred Calibre design rule decks and Calibre connectivity data to ensure that all layout modifications are Calibre-clean and meet design rule check (DRC) constraints. Here’s an overview of the main use models and how each of them contributes to achieving PPA goals:

Via insertion for IR drop mitigation

How it works: The via insertion feature is driven by user identified critical nets within the design and automatically maximizes the vias on that net to reduce IR drop. Calibre’s complete understanding of the DRC rules enable superior results without introducing costly respins.

Key processes: This feature leverages a “Via kit,” which includes all the complex via-related rules needed to ensure correct placement and compliance with DRC constraints. The Via kit provides access to multilayer enclosure and extension rules, net type spacing, via count checks, coloring rules and other critical parameters, ensuring that all inserted vias meet manufacturing requirements.

Benefits: By automating the via insertion process, design teams can achieve higher manufacturing robustness and lower IR drop without resorting to manual placement. Additionally, automated prioritization of high-current nets ensures that vias are inserted only where they provide the most benefit, optimizing both runtime and resource usage (figure 3). Real usage of Calibre DesignEnhancer has shown that adding vias to critical nets using the DE Via use model provided up to a 68% reduction in IR drop violations.

Fig. 3: Automated via insertion using the Calibre DesignEnhancer Via use model maximizes the insertion of Calibre-clean sign-off quality vias.

Parallel run lengths for enhanced electromigration resilience

How it works: To address both IR drop and electromigration, the tool identifies open tracks in the layout where additional metal and vias can be inserted to create parallel run lengths. These parallel structures reduce resistance on power grid lines and help distribute current more effectively.

Key processes: Designers are encouraged to use EMIR analysis to identify areas of the design that need improvement. Then using detailed knowledge of the DRCs DesignEnhancer Pge inserts Calibre-clean parallel metal and vias to reduce resistance. This targeted approach allows design teams to focus enhancements on areas most vulnerable to EMIR issues, rather than making blanket changes across the design.

Benefits: By inserting parallel runs where they are most needed, designers can reduce EMIR impact with minimal effect on timing. The process is efficient enough to run at the block or even chip level, making it viable for large-scale designs where EMIR issues could become significant bottlenecks (figure 4).

Fig. 4: The Calibre DesignEnhancer Pge use model automatically inserts Calibre-clean metal and vias in open areas to help lower resistance on power grid structures.

Automated filler and DCAP cell insertion for physical verification readiness

How it works: To prepare designs for physical verification, the tool automatically fills open areas in the layout with filler cells and decoupling capacitor (DCAP) cells. These cells prepare the design for physical verification. Detailed placement of the DCAP cells help reduce the dynamic IR drop.

Key processes: The filler/DCAP insertion model applies a correct-by-construction approach, guided by Calibre SmartFill technology. This ensures that all inserted cells are compliant with DRC requirements and electrically correct power domains. Knowledge of voltage threshold (Vt) rules is incorporated to ensure proper placement and continuity of power/ground structures across the layout.

Benefits: Automated cell insertion is less time-consuming. An order of magnitude reduction in run times is common because cell insertion is Calibre-clean. This allows designers to start their physical verification earlier and reduce their time to market (figure 5). Calibre DesignEnhancer yielded a consistent runtime that was nearly independent of the design size and generated a 6-16X reduction in runtime per design iteration.

Fig. 5: The Calibre DesignEnhancer Pvr use model automatically adds filler and DCAP cells to prepare designs for physical verification.

Advantages of design-stage layout modifications

Adopting a tool like Calibre DesignEnhancer provides compelling business benefits that go beyond technical capabilities. By leveraging design-stage layout modifications as part of a shift-left strategy, companies can achieve faster time-to-market, reduced development costs and enhanced design reliability. Here’s how:

• Accelerated time-to-market: Faster verification and correction cycles enable design teams to move from implementation to physical verification more efficiently. By minimizing time-consuming manual rework and achieving Calibre-clean layouts earlier, companies can reduce the overall time to market for their products.
• Lower development costs: Automation of layout optimization helps reduce resource-intensive manual or script based processes. Leveraging Calibre technology leads to fewer late-stage design iterations so companies can avoid costly delays and achieve predictable tapeout schedules.
• Enhanced reliability and competitiveness: By addressing IR drop and EM issues proactively, design teams can improve the long-term reliability of their IC products, resulting in fewer field failures. This increased reliability translates into a competitive edge, as customers seek robust and durable solutions.

Achieving shift-left verification

The shift-left methodology is about performing verification and optimization activities earlier in the design flow, allowing designers to tackle potential issues before they become costly problems at signoff. With Calibre DesignEnhancer, design teams can incorporate design rule check (DRC) constraints and foundry-preferred rules directly into their layout modifications. This approach ensures that the design meets both electrical and physical verification requirements as early as possible, streamlining the path to successful tapeout.

By taking advantage of Calibre’s analysis-based layout modification solutions, companies gain the Calibre confidence that their designs are DRC-compliant and physically optimized, reducing risks associated with IR drop, EM and physical signoff.

Learn more about IC power management

Design-stage layout modifications offer IC design teams and decision-makers an effective way to improve power management, streamline design cycles and reduce costs. By adopting a shift-left approach to power grid optimization, teams can effectively address power management challenges during implementation, rather than reacting to them at signoff.

To learn more about how to transform your design flow and help your team achieve EMIR targets with confidence, download our full technical paper today: Calibre DesignEnhancer design-stage layout modification improves power management faster and earlier.