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Table of Contents
Semiconductor Tape-Out: The Start of the Manufacturing Process
Tape out is the process in which the final design of a semiconductor chip is sent to the manufacturing facility for production. It marks the end of the design phase and the beginning of the manufacturing process. During the design phase, engineers create a detailed blueprint of the chip, including its architecture, circuitry, and layout.
Once the design is complete, it undergoes rigorous testing and verification to ensure that it functions correctly. This includes checking for any potential defects or issues that could affect the chip’s performance.
When the design has been thoroughly tested and verified, it is time for tape-out. This involves generating a set of electronic files that contain the precise instructions for fabricating the chip. These files specify the exact dimensions, materials, and structures that make up the chip, as well as the positioning and connections of the various components.
The tape-out files are then sent to a semiconductor manufacturing facility, or fab, where the actual fabrication process takes place. The fab uses these files as a guide to manufacture the chip on a silicon wafer, layer by layer, through processes like photolithography, etching, and deposition among others.
After the manufacturing process is complete, the chip undergoes further testing to ensure that it meets the required specifications and functions as intended. Once it passes these tests, it can be packaged and prepared for distribution to electronics manufacturers who integrate the chip into smartphones, PCs, or other electronic devices.
In the next section you can find a real life case study about the tape-out process, involving NVIDIA and TSMC.
NVIDIA's Turing GPU Tape-Out Process
NVIDIA Corporation is an American chip fabless company known for its graphics processing units (GPUs) and deep learning accelerators. In 2018 Nvidia developed and taped-out their Turing GPU.
Challenges:
- Architectural Complexity: The Turing architecture aimed to deliver substantial advancements in graphics rendering, ray tracing, and AI processing. This complexity increased the challenge of ensuring a successful tape-out.
- Manufacturing Partnership: NVIDIA collaborated with Taiwan Semiconductor Manufacturing Company (TSMC), a leading semiconductor foundry, to manufacture the Turing GPUs. Coordinating with an external foundry added complexity to the tape-out process.
Tape-Out Process:
- Design Refinement: NVIDIA’s engineers began with the architectural design and refined it iteratively to optimize performance, power consumption, and die size. They used advanced simulation tools to verify the design’s functionality.
- Photomask Generation: Generating the photomasks for each layer of the GPU design was a crucial step. NVIDIA’s engineers ensured the accuracy of these masks, as any defect could result in a non-functional or suboptimal product.
- Design Rules and DFM Checks: Design for manufacturability (DFM) checks were conducted to identify potential manufacturing issues, such as spacing violations, layer overlaps, or other design rule violations. Corrections were made as needed.
- Prototyping and Validation: NVIDIA produced engineering samples to validate the design’s functionality and performance. These prototypes helped identify and rectify design or manufacturing flaws.
- Tape-Out Planning: Prior to the tape-out, NVIDIA and TSMC collaborated closely to plan and schedule the manufacturing process. This included ensuring that TSMC’s fabrication facilities were equipped to handle the tape-out.
- Final Data Preparation: NVIDIA prepared the final design data and documentation, including the verified design files and the photomask data, for transmission to TSMC.
- Tape-Out Execution: The tape-out process involved sending the design data to TSMC, where the semiconductor fabrication process began. TSMC manufactured the GPUs according to NVIDIA’s specifications.
Results: NVIDIA’s Turing GPU architecture, manufactured through TSMC, was a significant success. It introduced real-time ray tracing to gaming and marked a major leap in graphics and AI processing capabilities. The successful tape-out ensured that the complex design was translated into functional silicon, enabling NVIDIA to maintain its leadership in the GPU market.
This case study underscores the crucial role of the tape-out phase in semiconductor manufacturing. NVIDIA’s meticulous planning, validation, and collaboration with a trusted foundry (TSMC) were essential in ensuring the successful production of their Turing GPUs. It highlights the importance of precision and attention to detail during the tape-out process to achieve the desired product’s functionality and performance.
History: From Manual Artwork to Advanced Automation
In the 1980s, the tape-out process was done manually and was a time-consuming and error-prone process. Designers would create artwork of the various layers of the chip using pen plotters, and these artworks would then be photographed onto film. In the 1990s, computer-aided design (CAD) tools began to automate the tape-out process. Designers could create digital versions of the chip artwork using software and these designs could be uploaded to the foundry directly.
The move to smaller process nodes (i.e. smaller transistors) at the beginning of the 20th century meant that the tape-out process became more complex. Designers needed to consider factors like power consumption, timing, and signal integrity in addition to the physical layout of the chip. More recently there has been a move towards “multi-project wafer” (MPW) services, where multiple designs from different customers are fabricated on a single wafer. This approach allows smaller companies and startups to get their designs fabricated at a lower cost.
Nowadays, the tape-out process is highly automated and uses sophisticated software tools to create and verify chip designs. Foundries typically offer a range of process options, from mature nodes optimized for cost and reliability to the latest cutting-edge technology nodes. The outcome of the fabrication is a packaged chip that can be used in a variety of electronic devices.
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