Calibre xACT takes a hybrid approach to parasitic extraction
By Mark Tawfik
Parasitic extraction plays a pivotal role in the design and optimization of integrated circuits (ICs). Extraction involves modeling unintended elements such as resistances, capacitances and interconnect parasitic that can significantly affect the circuit’s performance. Accurate extraction is essential, especially in advanced technology nodes where the parasitic effects become more pronounced due to smaller device sizes and complex interconnect architectures.
Understanding the parasitic extraction process
The parasitic extraction process consists of several sequential stages:
- Data preparation: Preparing the necessary design data for the extraction process.
- Extraction: Identifying and quantifying the parasitic elements within the circuit.
- Reduction: Simplifying the parasitic model to improve computational efficiency.
- Verification: Ensuring the accuracy of the parasitic model.
- Optimization: Refining the parasitic model to achieve the desired circuit performance.
These stages collectively ensure a precise representation of the parasitic elements and their impact on the IC’s behavior. By correctly modeling these parasitic, you can achieve better control over key factors like signal integrity, timing and power consumption, thus ensuring that the IC meets the required specifications. This approach is particularly crucial for achieving design closure and delivering high-quality IC products.
Addressing parasitic challenges in analog and digital design flows
In semiconductor design, analog and digital flows follow distinct paths, each catering to specific circuit requirements. Analog design involves managing continuous signals, such as in amplifiers, filters and converters, and requires a deep focus on minimizing noise and distortion while balancing power efficiency. On the other hand, digital design primarily deals with binary signals to create circuits using logic gates and other digital components. The objectives are speed, power efficiency, and noise resistance, often utilizing automated tools for faster and more consistent circuit development. While analog designs are typically more intricate due to the need for precision in signal processing, digital designs are streamlined through standard cell libraries and automated synthesis tools. However, both analog and digital design workflows necessitate reliable parasitic extraction to ensure optimal circuit behavior across various operating conditions.
Leveraging parasitic extraction tools
Parasitic extraction tools are generally classified into two main types: field solver-based and rule-based. Field solver methods utilize 3D numerical techniques to solve Maxwell’s equations, providing highly accurate results that are ideal for intricate geometries and interconnects, especially in high-frequency and radiofrequency (RF) circuit designs where accuracy is paramount. However, the computational intensity and resource requirements of 3D field solvers limit their practicality for large-scale digital designs where quick turnaround times are necessary. In contrast, rule-based extraction utilizes a 2.5D approach by applying predefined rules and design guidelines to estimate parasitic elements more rapidly, though it may sacrifice some accuracy in more complex scenarios. This approach is well-suited for most digital and analog workflows due to its efficiency and ease of use. Additionally, pattern matching serves as another 2.5D technique that further enhances efficiency by identifying recurring layout patterns and applying pre-characterized parasitic values. Designers often choose between these methodologies based on the design’s specific requirements, balancing accuracy and computational demands.
The Calibre xACT hybrid approach
The Calibre xACT comprehensive parasitic extraction tool stands out for its ability to combine the strengths of both field solver and rule-based approaches. It is widely adopted in the semiconductor industry due to its versatility and precision in capturing parasitic effects across both analog and digital design flows. Calibre xACT facilitates the modeling of various parasitic components, such as resistances, capacitances, and metal fills, which are often necessary to meet design rules and manufacturing specifications. Its hybrid approach allows designers to switch between precision and efficiency depending on the complexity of the circuit and the design requirements. Key features like multi-corner extraction, hierarchical LEF/DEF support and dummy metal fill modeling enhance its ability to handle the demands of modern IC designs, ensuring accurate simulation and reliable performance. Additionally, Calibre xACT’s support for various formats such as SPEF, DSPF and SPICE makes it a versatile choice for different stages of the design flow.
Key features of Calibre xACT-Digital
The digital flow capabilities of Calibre xACT are further enhanced by features such as detection and reporting of shorts and opens, hierarchical extraction for large-scale designs, simultaneous multi-corner extraction and user-defined rules for selective net extraction. These features help streamline the extraction process and improve the accuracy of parasitic modeling in complex digital circuits. Calibre xACT’s dprep tool simplifies the preparation of LEF/DEF-based digital designs by automating layer mapping and rules generation, making it easier to set up extraction runs. The tool is qualified across all design nodes, from mature technologies to advanced processes, ensuring broad foundry support and reliability.
Summary
Parasitic extraction is essential for modeling unintended elements like resistances, capacitances and interconnect parasitic that can significantly impact circuit performance, especially in advanced technology nodes. Calibre xACT offers a powerful hybrid approach to parasitic extraction, allowing semiconductor companies to achieve design closure efficiently, optimize performance and bring high-quality products to market with confidence. We discuss this topic even further in a recent technical paper Achieving precision in parasitic extraction
