Can smarter RTL-to-GDSII flows revolutionise chip design? With AI, automation, and better design practices, semiconductor development is getting faster, leaner, and more efficient than ever.
The semiconductor industry is continuously driven by the need to deliver higher performance, lower power, and smaller form-factor chips at increasingly rapid turnaround times. As chip designs become more complex, optimising the efficiency of the register transfer level (RTL) to graphic data system (GDSII) flow is critical for meeting these challenges. The RTL-to-GDSII flow bridges the conceptual high-level design stage with the final physical layout, and improving efficiency in this flow can significantly impact the design cycle time, resource utilisation, and overall quality of results (QoR).
Inside the RTL-GDSII journey
The RTL-to-GDSII journey encompasses critical design stages that must work in sync to transform high-level logic into manufacturable layouts. This workflow demands technical precision and proactive risk management to prevent downstream delays. Any inefficiency or misstep at one stage cascades into downstream problems, leading to delays and suboptimal results.
While traditional flows are often sequential and tool-centric, today’s design requirements demand tighter integration, automation, and optimisation across stages. Enhancing efficiency in this flow can lead to faster time-to-market and lower costs while maintaining high quality.
Key Strategies for Enhancing RTL-GDS Efficiency
1. Improving RTL quality
The quality of RTL directly influences the success of the downstream physical design stages. Poor RTL coding practices can lead to high design complexity, timing bottlenecks, and congestion, which are challenging to resolve during synthesis and place-and-route stages.
- Design guidelines and checks: Implementing static analysis tools, RTL linting, and power-aware coding practices ensures that the RTL is clean and optimised before entering synthesis.
- Hierarchical design: Breaking down complex designs into smaller, modular blocks facilitates easier floorplanning, placement, and routing, improving overall efficiency.
2. Efficient design synthesis
Efficient synthesis bridges RTL with the gate-level domain, directly impacting area, timing, and power outcomes.
- Constraint management: Accurate timing and power constraints must be defined at the synthesis stage to minimise iterations during timing closure.
- Use of advanced synthesis tools: Modern synthesis tools offer optimisation techniques such as retiming, logic restructuring, and multi-threshold libraries to balance power, performance, and area (PPA).
- Incremental synthesis: By synthesising only the updated portions of the design rather than the entire design, engineers can save significant runtime.
3. Automated and optimised floorplanning
Floorplanning is the process of defining the placement of major functional blocks and macros in the chip layout. A poor floor plan leads to routing congestion, power integrity issues, and longer design cycles.
- Early congestion analysis: Tools that provide early feedback on congestion hotspots enable designers to refine the floor plan before moving to placement.
- Power-aware floorplanning: Strategically placing high-power blocks near power rails and implementing power gating techniques improves power efficiency and reduces IR drop.
4. Placement and clock tree synthesis (CTS)
Placement involves arranging standard cells and macros, while CTS ensures that clock signals reach all parts of the design with minimal skew and delay.
- Placement optimisation: Integrating timing and congestion-aware placement tools reduces timing violations and routing issues early in the design.
- Skew optimisation: Advanced CTS tools use techniques like multi-corner analysis and clock gating to minimise clock skew and reduce power consumption.
5. Efficient routing techniques
Routing is one of the most computationally intensive steps in the RTL-GDSII flow, as it involves connecting millions of gates and ensuring signal integrity.
- Congestion-aware routing: Tools that analyse and optimise routing congestion help mitigate design risks before final tape-out.
- Signal integrity checks: Automated checks for noise, crosstalk, and electromagnetic interference (EMI) ensure robust design performance.
6. Automation and machine learning in the flow
With growing design complexity, automation and AI-driven tools are playing an increasing role in improving efficiency:
- AI-based prediction models: Machine learning models can predict design bottlenecks, timing violations, and congestion, enabling early corrections.
- Automation of repetitive tasks: Automating redundant tasks such as ECO (engineering change order) implementation and design rule checks (DRCs) saves time and effort.
7. Early sign-off and verification
Physical verification, including DRC and LVS (Layout Versus Schematic), ensures that the design meets manufacturing and design rules.
- Parallel verification: By running verification checks concurrently with the design process, engineers can catch errors early and reduce last-minute iterations.
- Sign-off tools integration: Leveraging integrated sign-off tools during place-and-route ensures that designs are DRC and LVS clean before final GDSII generation.
Why this matters: key benefits
- Reduced turnaround time: Minimising iterations, automating processes, and improving design quality shorten the overall cycle.
- Improved PPA (power, performance, area): Efficient synthesis, placement, and routing directly enhance QoR.
- Lower design costs: Streamlined design cycles and reduced tool runtimes cut costs.
- Enhanced scalability: Efficient flows handle growing design sizes and complexities with ease.
Final thoughts
Optimising the RTL-to-GDSII flow remains crucial for coping with modern semiconductor challenges. By combining high RTL quality, automation, and AI-driven tools, design teams can achieve faster time-to-market and better power, performance, and cost outcomes.
References
Author By: Vinayak Ramachandra Adkoli holds a BE degree in Industrial Production and has been a lecturer in three different polytechnics for ten years. He is also a freelance writer and cartoonist.
