This article discusses how an analog chip engineer progresses step by step from the initial stage to tape-out. This process is described from a personal perspective and may vary slightly between different companies.1. First, you need to have a project, which means having a client. Communicate with the client to conduct a requirements analysis and determine the chip’s specifications. Who is responsible for this work? Usually, it is the department head, but the direct communication with the client is typically not done by the head; I am not sure who it is. ♀️2. Document writing. What documents? Generally, it includes the overall specifications of the analog circuit and the specific specifications of each module. This specification is preliminary; for example, for the ADC module of the analog circuit, the overall parameter requirements need to be defined, such as accuracy, speed, signal-to-noise ratio, etc. The specific structure to be used is not determined at this stage. Additionally, there are documents for circuit naming conventions, design rules, etc., which mainly explain the naming rules for each module, pin naming rules, paths for process files, paths for various simulation files, and which libraries to use for simulation. This document is written by the head to inform everyone to follow unified rules and not to design arbitrarily.3. The head assigns tasks, determining who is responsible for each small module in the analog circuit. Once the tasks are assigned, each person reviews the specifications for their respective modules.4. Research phase. Now that you know which module you are responsible for, the next step is to research circuit structures or reuse structures from old projects. Verified circuits that can be used directly should be used; if not, new structures need to be researched to determine the structure of each person’s block.5. Determining the block structure is not as simple as it sounds. If new structures need to be researched, it can be quite time-consuming, involving research papers, patents, etc. Reviewing literature or examining chips from other companies are all part of the research process.6. After reaching a certain stage in the research, circuit assembly begins. Once the structure is confirmed to be feasible, practical simulations are conducted to see if the structure meets the requirements. If it does not, the structure is changed, and simulations are repeated to check if the parameters can meet the preliminary specification requirements. If the results are far from acceptable, the structure is changed again, and simulations are conducted until the simulation parameters align with the preliminary specifications, at which point the structure is finalized.7. After finalizing the structure, detailed circuit simulations are performed. Based on the simulation results, the circuit is adjusted and simulated again, repeating this process until the simulation parameters fully meet the specifications, ensuring that the simulations are detailed and comprehensive.8. The process of finalizing the circuit structure mentioned above requires regular reviews and discussions with the head and colleagues.9. Depending on client requirements, certain circuit functions may be reintroduced or some circuit parameters may be modified, but these are generally minor changes and not significant alterations.10. After the final circuit review, once it is confirmed that there are no issues with the circuit simulation, each person must create a checklist for their module, summarizing the important simulation results. Then, each person must write a detailed specification for their module, covering detailed parameters, functional descriptions, interface introductions, voltage domain descriptions, and sometimes drawing timing diagrams, etc. This detailed specification differs from the initial specifications set by the head and is intended for the head or the digital team for easy reference.11. Then, layout work can begin. The layout engineer first needs to create a floor plan, and after completion, they will show it to you for review. If the layout is satisfactory, they will proceed with the wiring. During this time, the analog engineer will have regular meetings with the layout engineer to communicate.12. If the analog circuit you are responsible for requires mixed-signal simulation, the analog engineer must also write a documentation for the digital team, explaining how the mixed-signal simulation should be conducted, and the digital team will provide the corresponding mixed-signal environment.13. During this period, the head will periodically request documents from everyone for TOP-level work, such as area estimates for each module and important considerations for each layout. In summary, all matters related to the TOP are communicated and completed by the head.14. After the layout engineer completes the layout, the analog engineer begins post-layout simulation. Based on the results of the post-layout simulation, they will determine whether to modify the layout. Once the post-layout and mixed-signal simulations are completed without issues, the head will conduct a simple overall simulation for the TOP. It is referred to as simple because the scale of the TOP is large, and complex simulations cannot be performed; only simple functional simulations can be conducted, while complex simulations are handled at the module level by each analog engineer.15. Finally, once the layout engineer completes the TOP layout and exports the GDS, tape-out can proceed!
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