EDA (Electronic Design Automation) refers to the computer software tool cluster used to assist in the completion of the entire process of ultra-large-scale integrated circuit chip design, manufacturing, packaging, and testing. It is a kind of generalized CAD (Computer Aided Design). EDA evolved from the concepts of computer-aided design (CAD), computer-aided manufacturing (CAM), computer-aided testing (CAT), and computer-aided engineering (CAE) in the mid-60s of the 20th century.
Introduction of EDA
EDA is a sub-industry in the industrial software industry. Industrial software refers to the software dedicated to or mainly used in the industrial field to improve the research and development, manufacturing, management level and industrial equipment performance of industrial enterprises.
Industrial software can be divided into R & D design, production scheduling and process control, business management three major areas from the application link, of which PLM, MES and ERP are typical representatives of industrial software systems in these three fields, EDA and PLM, belong to the R & D and design of industrial software.
The design, production and manufacturing of integrated circuits is complex, and EDA technology integrates the latest achievements in applying electronic technology, computer technology, information processing and intelligent technology, and uses computers as working platforms for automatic design of electronic products.
EDA design tools cover the front-end circuit design, verification, back-end physical design, packaging design and testability design of the industry chain, driving the development of chip design, manufacturing and terminal applications.
Before the birth of EDA tools, developers draw circuit design manually. Since using EDA software, electronic designers can design electronic systems from concepts, algorithms, protocols and complete the whole process of integrated circuit products from circuit design, performance analysis to design IC layout or PCB layout, which optimize the chip manufacturing process, drive the downstream links of the chip industry chain to greatly improve work efficiency, and reduce labor intensity.
In the semiconductor industry chain, EDA is the most upstream and high-end industry of the integrated circuit industry chain, the “cornerstone” of chip design, and one of the important auxiliary tools to promote chip design innovation.
Roles of EDA in IC design
In chip design, EDA can reduce risk and reduce trial and error costs. Most chip products cannot be changed once manufactured, but their design is extremely complex, manufacturing and R&D costs are also extremely high, EDA has at least three roles in this process:
(1) It can accurately express complex physical problems as quantitative models, simulate circuit processes in virtual software, and reproduce various effects in the chip development process, so as to discover potential design defects and risks.
(2) Under the premise of ensuring the correct logic function, it can simulate and analyze the optimal solution of performance, power consumption, cost, etc. of a specific process under various conditions, solve the multi-objective constraint problem, and reduce the cost of trial and error.
(3) Verify the model consistency to ensure that the logic functions of the chip are consistent in multiple design links.
Types of EDA
In addition to playing a huge role in chip design, EDA also has very important applications in PCB design and flat panel display design. There are different statements on the classification of EDA. A common classification method is to divide EDA into IC design software, circuit design and simulation tools, PCB design software, PLD design tools and other EDA software, etc.. Another common classification method is to divide EDA into digital design, analog design, wafer manufacturing, packaging, services and other five categories according to products.
1. IC EDA
1.1 IC design category
The chip design process can be mainly divided into front-end design and back-end design, of which front-end design (also known as logic design) mainly involves the functional design of the chip, and back-end design (also known as physical design) mainly involves process-related design, making it a chip with manufacturing significance.
In terms of subdivision, chip design includes multiple processes such as RTL writing, functional verification, logic synthesis, formal verification, DFT, layout and route, Sign Off, and layout verification. The specific process of digital chip design and analog chip design is different, so the EDA software required is also different.
In summary, EDA software mainly includes the following functions in IC design, of which functional verification and Sign-Off mainly refer to circuit simulation and analysis:
Functional verification: to ensure that the design functions correctly and to ensure that the chip can achieve the predetermined and expected behavior and actions;
Logic synthesis: translate each functional module described in behavior-level language to low-level language, and use the combination of underlying logic gates to realize the function of the circuit module;
Layout and routing: replace the logic gate after logic synthesis with logic gates with actual physical parameters, and interconnect them together according to the established functions to form a layout with manufacturing significance;
Sign-Off: Ensures that all traces, timing, and power consumption of the chip design meet the requirements of the manufacturing, product, and system.
Note: The literal meaning of Sign Off here is signed, which can refer to the signature and consent of the design manager, layout manager, and process leader. Tape Out originally means “offline”, which refers to the submission of the final GDSII file, that is, the mask information, to the mask factory for production.
1.1.1 Digital circuit design
It mainly divided into front-end logic design and back-end physical design, and team roles are usually divided into front-end designers and back-end designers. Although there is no uniform and clear boundary, front-end design and back-end design are usually separated by the generated gate-level netlist.
The front-end designer takes the chip architecture as the starting point and the netlist as the end point, mainly satisfies the design and verification of circuit functions and logic, and has front-end verification engineers, architecture engineers, DFT engineers, etc. to complete the work; The back-end designer starts with layout-and-route and ends with a GDSII file that can be sent to the fab for tape-out.
Digital circuit front-end design uses logic circuits to achieve expected specifications, focuses on logic functions, and mainly includes two parts: design and verification. The specific process includes: system overall planning, module design, top-level module integration and top-level functional module verification, logic synthesis, formal verification, static timing analysis, testability timing insertion, etc.
The back-end design of digital circuits pays attention to layout and simulation, mainly including process implementation and flow. The specific process includes: layout physical planning, power analysis, unit layout and optimization, clock tree synthesis (CTS), wiring, signal integrity analysis, parasitic parameter extraction, physical verification, etc.
1.1.2 Analog circuit design
Compared with digital circuits, analog circuit design requires higher long-term practical experience of engineer. The whole process is usually undertaken by a group of engineers, resulting in blurring the boundary between the front-end and the back-end. It can also divide its design process into two parts, namely the functional design of the front-end and the physical implementation of the back-end.
The front-end functional design of analog circuits mainly refers to the logical process of design requirements and performance parameters. First of all, it is necessary to determine the system input-output relationship, define the system function, standardize the parameter range such as timing, area, power consumption, signal-to-noise ratio, etc., and complete the first step of target quantification. Then, the performance of the circuit application is evaluated through simulation to determine the interval and limit of the circuit operation, and optimize the circuit logic function structure in the repeated verification and result improvement.
When the simulation results of the circuit performance meet the design requirements, it begins to enter the back-end circuit layout design stage, that is, customize the physical layout that meets the process requirements. As a bridge between circuit related parameters and physical models, the physical layout realizes the conversion of the design circuit to the graphical description format. After going through physical layer verification, computer simulation verification and improvement, the physical manufacturing of the design layout is finally realized.
1.2 IC manufacturing
EDA is not only used in chip design, but also widely used in wafer manufacturing, and is a bridge and link connecting the two links of integrated circuit design and manufacturing. In the process platform development stage, after the fab completes the design of semiconductor devices and manufacturing processes, it needs to use EDA tools to establish device models, generate PDKs, and IP and standard cell libraries, in addition to lithography calculations and yield improvement in the wafer manufacturing process, EDA software tools are also required. Wafer fabrication EDA tools include device model extraction tools, process and device simulation (TCAD), PDK development and verification, computational lithography, mask calibration, mask synthesis, and yield analysis.
1.3 IC packaging
It mainly provides packaging design platform, covering package design, verification, implementation and other links. It should be noted that as the chip process approach the physical size limit, 2.5D/3D packaging, chiplets and other advanced packaging have become a new direction to improve chip integration, and the demand for the entire IC package is more and more similar to the situation of IC design. This also makes chip design no longer a single-chip problem, but gradually evolves into multi-chip system engineering.
New problems have emerged, and large-scale data reading in advanced packages has shown that the requirements for high-density silicon interconnect assembly, high performance yield and low power consumption have put forward higher requirements for EDA algorithm engines.
2. PCB EDA
PCB EDA includes PCB design and manufacturing. There are many types of PCB design software, such as Protel, OrCAD, Viewlogic, PowerPCB, Cadence PSD, Mentor’s Expedition PCB, Zuken CadStart, WinboardWindraftIvex-SPICE, PCB Studio, TANG and many more. PCB manufacturing software mainly includes tools in the field of PCB fabrication and process control.
3. Flat panel display EDA
3.This mainly includes flat panel display design EDA for panel manufacturers. The FPD design process includes circuit schematic design, layout design, circuit simulation, circuit layout parasitic parameter extraction, circuit design verification, etc., similar to the design process of analog integrated circuits, but also has its own unique design process and design method. Similar to integrated circuit design, EDA is also the cornerstone of flat panel display circuit design.
The development history of the EDA
1. CAD stage: In the 70s of the 20th century, due to the low complexity of the chip, designers could manually complete the input, layout and wiring of the circuit diagram. In the mid-70s, the advent of programmable logic design technology made it possible to automate chip design. With the increase in integration, designers began to try to use CAD tools for design engineering automation instead of manual drawing, and realized interactive graphics editing, IC layout design, PCB layout and routing, design rule checking, gate-level circuit simulation and verification.
2. CAE stage: in the 80s of the 20th century, EDA technology entered the stage of development and improvement, the launch of EDA tools to logic simulation, timing analysis, failure analysis, automatic layout and wiring as the core, focusing on solving problems such as function detection, using these tools, designers can predict product function and performance before product production. In the late 80s, EDA tools were available for design description, synthesis and optimization, and verification of design results. During this period, EDA commercialization gradually matured, and the predecessors of the current EDA international giant, Siemens EDA, Mentor Graphics, Synopsys and Cadence, were established in 1981, 1986 and 1988, respectively.
3. EDA stage: In the 90s of the 20th century, with the standardization and development of chip design process and the improvement of integrated circuit design methodology, EDA tools characterized by high-level language description, system-level simulation and synthesis technology appeared. Since then, EDA technology has made a great breakthrough and truly realized the automation of design.
4.Modern EDA era: Around 2000, EDA software tools that support standard hardware languages at the two levels of simulation verification and design are more powerful, larger programmable logic devices are continuously introduced, and system-level and behavior-level hardware description languages tend to be more efficient and simple. At present, EDA tools have been able to achieve full coverage of the design, manufacturing, packaging and other links of integrated circuits, and are used in design work in many fields including analog circuits, digital circuits, PCBs, panels and so on.
Conclusion
EDA tools are the support of integrated circuit design and manufacturing process, the carrier of integrated circuit design methodology, and the link and bridge connecting the two links of design and manufacturing. Integrated circuit companies need to use EDA tools to complete the design and manufacturing process. With the increasing complexity of chip design, the scale of integrated circuits based on advanced process nodes can reach billions of semiconductor devices, and chip design can no longer be completed without EDA.
EDA refers to the use of computer-aided design (CAD) software to complete the functional design, synthesis, verification, physical design (including layout, wiring, layout, design rule checking, etc.) of very large scale integrated circuit (VLSI) chips.
● Verify the correctness of the circuit design scheme
● Optimized design of circuit characteristics
● Implement analog testing of circuit characteristics
1. CAD stage
2. CAE stage
3. EDA stage
4. Modern EDA era
