3D IC design

Three-dimensional integrated circuits (3D-ICs) are revolutionizing the semiconductor industry. Manufactured by stacking and interconnecting dies so they perform as a single device, 3D-ICs deliver more capabilities by offering higher performance and bandwidth — while also reducing power consumption, package size and costs. However, 3D-ICs present tough design challenges to engineers. Significantly larger than a single-chip system on a chip (SoC), these assemblies have more components, more integration points and longer interconnects, that translate to new risks for high-frequency signal failure, reliability, and other performance issues such as thermal buildup. As the lines between silicon and system continue to blur, engineers must conduct concurrent, multivariate analysis to assess every possible failure mode ― not only at the component level, but also across the entire 3D-IC assembly ― a technical obstacle for many development teams accustomed to applying a series of single-physics engineering simulation tools in a sequential approach. 3D-ICs are assembled in a complex package using a serial analysis approach that doesn’t take into account system-level interactions, as well as the many thousands of bump connection points where something can go wrong. By contrast, concurrent, multivariate simulation and analysis takes into account all physics simultaneously from the earliest prototyping stages of design. Most semiconductor development teams not only lack the technical tools to perform this complex simulation and analysis, but they also face cultural obstacles as they undertake system-level analysis. Diverse teams working with disparate tools simply aren’t equipped to perform seamless handoffs and collaborate effectively on a complex 3D IC design from an early stage. Instead, they scramble to address system-level issues later when launch delays are likely, the cost of rework is high and their positive contributions to the design are diminished. The Value of a True Multiphysics, Multivariate Approach As market demand for 3D-ICs increases, semiconductor development teams need a single simulation platform that enables simultaneous multiphysics analysis — including power integrity, reliability, electromagnetics (EM), thermal, computational fluid dynamics (CFD) and mechanical studies ― across the entire assembly. A unified simulation platform that brings together best-in-class solutions for every physics enables semiconductor engineers to collaborate across functions, seamlessly hand off analysis tasks between engines, and partner to optimize 3D-IC designs across every performance parameter. Costly surprises from signal integrity to thermal conductivity and structural strength are far less likely when the team reaches physical assembly to help ensure on-time, cost-effective product launches. An example of simultaneous multivariate analysis of a chip stack showing both thermal gradients and mechanical stress/warpage of the package at an early prototyping stage. By contrast, applying multiple physics sequentially can lead to ongoing and expensive setbacks. For example, as one team resolves signal integrity issues, another team could discover that timing failures or thermal risks have arisen. It’s not only back to the drawing board, but back to a series of time- and resource-intensive handoffs across disconnected simulation and analysis tools, as well as across functional boundaries. The Importance of Considering Novel Physics Because the pressure is on to launch innovative 3D-IC designs rapidly, development teams might be tempted to focus on existing signoff metrics ― which are complicated enough, across today’s multi-die assemblies — but overlook the application of more novel physics. This is a mistake that can result in failures in the field, product recalls, warranty expenses and lasting damage to the brand reputation. To achieve full product confidence across the entire 3D-IC system, semi engineering teams need a solution set and associated best practices that make it fast and intuitive to not only optimize performance and cost, but to concurrently analyze novel physics that will impact electrical reliability, mechanical stability and thermal failure modes. The number of physical effects that need careful simulation has risen in lockstep with Moore’s Law and has increased even more for 3D-IC design. The use of a single, connected platform enables this kind of true multiphysics analysis. A multiphysics platform should interface with popular design systems, and be extensible by Python API's to the user and to other vendors. For example, engineers can check the thermal behavior and the likelihood of melting and local failures of each solder bump based on the electrical current it carries. The engineers can apply computational fluid dynamics to evaluate how well airflows generated by fans and heat sinks work to cool down the assembly. They can maximize system reliability by examining unfamiliar effects like low-frequency power oscillations on the distributed power supply network. Best of all, a unified and purpose-built simulation platform enables semiconductor development teams to conduct all these studies simultaneously to rapidly reveal design trade-offs that arise when many elements are brought together in a complex assembly. Only this type of multiphysics, multivariate, concurrent approach enables engineering teams to reach all their goals for speed, confidence, innovation and product performance as 3D-IC designs take over the global market. Supporting a Culture of Vertical Integration Global leaders in the semiconductor and electronics industries benefit from a culture and organizational model based on vertical integration, which supports high levels of design collaboration. It can be tough for horizontally integrated, smaller companies to establish this depth of collaboration. Customers require open and extensible platforms that support a broad range of analysis tools across many different abstraction levels – from device to chip to board to system. The right simulation technology platform can significantly help. A shared platform that brings cross-functional engineering teams together for simultaneous, not sequential, multiphysics design can make it easy and seamless to collaborate across functional boundaries and support excellence in every aspect of power, performance, reliability and cost. By balancing these foundational performance aspects with simultaneous optimizations of temperature, mechanical stress and other subtle effects, semiconductor engineering teams can position themselves as leaders, not followers, in the 3D-IC revolution. Learn More at the Ansys IDEAS Digital Forum Register for Ansys IDEAS Digital Forum on demand to learn more about 3D-IC best practices from leading industry experts (www.ansys.com/ideas). John Lee is General Manager of the Electronics and Semiconductor Business Unit at Ansys.

Spend any time with Ansys’ John Lee, Rich Goldman or Marc Swinnen and you’ll hear plenty of optimism about the semiconductor industry even though they tick off a long list of looming design challenges. The need for reliable and effective electronic systems, they emphasize, is great and runs through high tech, aerospace and defense, automotive, IoT and 5G with communications being a common denominator. The three are especially bullish these days on changing market dynamics brought on by systems companies building company-specific bespoke, or custom, silicon. These systems companies are building chips with a different perspective and a fresh look at silicon design, a move away from the more traditional segment-specific silicon due to much more complexity. Ansys, a member of the ESD Alliance, a SEMI Technology Community, is a 4,100-employee company with a comprehensive portfolio of multiphysics engineering simulation software for product design, testing and operation products and services. John, Rich, Marc and I focused on Ansys’ semiconductor and electronics segment for our conversation. Smith: When did you notice the move by systems companies to build their own chips? What drives this trend? Lee: The inflection point was about three years ago when hyperscale data center and system companies recognized they needed an enterprise system design platform. They are designing bespoke silicon, driven to do this for cost efficiencies and to avoid relying on outside suppliers. They also want differentiation based on their specific platform needs so they can optimize compute power to their specific needs. Smith: What is driving the trend for multiphysics experience to ensure effective and reliable electronic systems? Lee: The increasing need for multiphysics analysis is acute. The physics of 3D IC, for example, brings in mechanical engineering with the convergence of mechanical and electrical as 3D emerges at the intersection of IC and System. As a result, physics becomes a necessity to analyze the stability of the chip in the package. Goldman: As well, the move to stacked chips, 3D IC and wafer-on-wafer requires thermal, electromagnetic and mechanical analysis in addition to the traditional analysis for function, performance and power. They all need to be analyzed together, not serially. It becomes multiphysics, not multiple physics. Smith: Two distinctly different disciplines – multiple physics and multiphysics – are needed for semiconductor design. How are they different? Why the need now? Swinnen: Multiple physics refers to the sheer breadth of physics that is now needed to analyze from the IC up to the largest system whereas multiphysics refers to the capability to analyze several physical effects concurrently, accounting for their impact on the design and interactions between various physics. Multiphysics are necessary to analyze the full context of the system environment – from nanometers to kilometers – for multi-chip packaging, chip-to-package-to-silicon and systems with multi-domain guidance. Goldman: A self-driving car, as an illustration, includes AI systems-on-chip, solid-state sensors, infotainment systems and radar/lidar detectors that must all work in the rain, the heat and the bitter cold. Smith: Why are design groups being reorganized to include expertise in mechanical and electromagnetic issues? Swinnen: Complexity has exploded, driven by a long list of technical requirements and, perhaps, mischaracterization. Goldman: Just consider the system on chip, mischaracterized by the semiconductor industry. The chip is never a system by itself. Rather, it is a complex component in a larger system and must be analyzed in that context. 3D IC is where this comes together and forces a recognition of physics outside the traditional scope of SoC design. 3D IC chips are much closer together on the board and it takes multiphysics embedded into the workflow of semiconductor design, packaging, system design and 3D IC to ensure they work reliably and efficiently. Smith: What is the solution? Goldman: It’s clear a specialized digital thread is necessary to move disparate groups with expertise in systems, physics and silicon together. Today, these groups or disciplines might not exist in the same company, whether it be a foundry, fabless or outsourced semiconductor assembly and test (OSAT) company. Lee: In order to unify the entire system design environment, a cloud-based, open and extensible heterogenous enterprise compute platform is required. It is similar to the SaaS-based business model and known as Simulation-as-a-Service (also SaaS). While vertical integration of design groups is already taking place at leading system design houses, there have also been advances in electronic design tools. These are starting to offer more comprehensive multiphysics capabilities including thermal, fluid dynamics (CFD), mechanical stress and reliability analysis in a single analysis cockpit. Today’s system designers face two platform challenges: First, they need an environment that is open enough to accept analysis results from multiple sources so that they can be overlapped and cross-analyzed. Second, the design platform must have the capacity to handle the enormous amounts of data generated by the latest 3-nanometer chips and 3D IC systems, and this implies an intimate coupling to elastic cloud computing. The days of an engineer writing Perl scripts and handing it off to someone else are gone. We believe that the industry is responding to this challenge with a new generation of design platforms that a cloud-native, open and extensible to allow heterogenous enterprise design. We are definitely at an inflection point in electronic design today, but the electronic industry has faced these before an we are confident it will master these challenges as well. About Rich Goldman Rich Goldman is director of marketing for the Electronics and Semiconductor Business Unit of Ansys. He holds a Bachelor of Science degree from Syracuse University and an MBA and Master of Science degree in Engineering Management. Moscow Institute of Electronic Technology (MIET)’s first honorary professor, he is also the recipient of honorary PhD degrees from Russian-Armenian (Slavnoic) University and State Engineering University of Armenia for contributions to the advancement of Armenia’s high-tech education and economic ecosystem. Rich served on EDAC’s board of directors. About John Lee John Lee is general manager and vice president of the Ansys Electronics and Semiconductor Business Unit. Lee co-founded and served as CEO of Gear Design Solutions (now Ansys), developer of the first purpose-built big data platform for integrated circuit design. He cofounded two other startups (Mojave Design and Performance Signal Integrity), which successfully exited into companies now part of Synopsys. He holds undergraduate and graduate degrees from Carnegie Mellon University. About Marc Swinnen Marc Swinnen is director of product marketing for the Electronics and Semiconductor Division of Ansys. He holds Master degrees in Electronic Engineering and Industrial Management from KU Leuven, Belgium, as well as an MBA from San Jose State University. About Bob Smith Robert (Bob) Smith is executive director of the ESD Alliance, a SEMI Technology Community. He is responsible for the management and operations of the ESD Alliance, an international association of companies providing goods and services throughout the semiconductor design ecosystem.