Part One: What is “Chip Fabrication”?
We can understand it as “the first trial print of constructing an ultra-complex skyscraper”.
Imagine you want to build a special skyscraper—it is a microchip with billions of “rooms” (transistors), and the design is extremely complex. If you start construction directly and make a design error, the entire “building” will be scrapped, resulting in huge losses. “Fabrication” is the “first trial production” process that solves this problem, which is specifically divided into three steps:
1. Drawing the design blueprint: The engineering team uses computer software, spending months or even years, to create a “blueprint” detailing all aspects of the chip (completing the chip design).
2. Conducting the first trial production: This “blueprint” is handed over to a chip foundry (such as TSMC or SMIC, equivalent to an “expensive 3D printing factory”), allowing the factory to produce a few to dozens of miniature chip samples according to the drawings.
3. Testing whether the samples are qualified: These samples are not for sale but for testing and validation, such as checking whether the “circuit functions correctly” (is the building structure solid?), whether the “signal transmission is smooth” (are the water and electricity pipelines clear?), and whether there are any design flaws (are there any doors that cannot be opened?).
In simple terms, fabrication is the process of sending the design to the factory for the first trial production of samples after the chip design is completed, followed by rigorous testing to verify whether the design is feasible.
Why is fabrication “important yet daunting”? The key lies in its extremely high cost—just like spending hundreds of millions to build a miniature model for trial construction of a skyscraper. The cost of a single fabrication can reach tens of millions of dollars, or even over a hundred million RMB. If the tests are successful, it can lead to large-scale mass production; but if it fails, hundreds of millions in costs will be “down the drain”, and the design team will have to revise the drawings, fabricate again, and incur another exorbitant cost.
Part Two: The Complete Chip Manufacturing Process (Simplified Version)
The entire process can be likened to “using light to imprint the most complex patterns in the world on silicon wafers”, mainly divided into three major stages: design, manufacturing, and packaging/testing.
Stage One: Design—Drawing the Blueprint for the “Super City”
This step involves formulating a detailed “construction plan” for the chip, ultimately outputting the design blueprint to be used for fabrication, progressing through four steps:
1. Defining the system architecture: First, clarify the chip’s purpose and goals—will it be the “brain” of a mobile phone (CPU) or the “graphics core” (GPU) for image processing? What performance is required?
2. Conducting logical design: Engineers use “Hardware Description Language (HDL)” to write code, transforming the chip’s functional logic into a “city functional zoning map”—for example, where the “residential areas” and “commercial areas” are, and how the roads connect.
3. Drawing the circuit design: Break down the logical functions into individual transistors, resistors, capacitors, and other basic components, creating a specific circuit diagram, akin to detailing every block and building’s structure.
4. Conducting physical design (layout and routing): This is the most meticulous step—on the chip’s “ground”, all circuit components are arranged reasonably, and “nanoscale wires” are used to connect them. It’s like high-density planning of every building, street, and pipeline in a limited space, ensuring no conflicts and high efficiency. Finally, output the “GDSII format” of the final blueprint for the factory’s use.
Stage Two: Manufacturing—Carving the “Nano City” on the “Silicon Wafer”
The foundation for manufacturing is the silicon wafer: first, pure silicon ingots are extracted from sand (silicon dioxide), then sliced into thin sheets like cutting sausage, which is the “wafer”. The following five steps will be repeated on the wafer, layer by layer building transistors and circuits:
1. Thin film deposition: Various material thin films (such as insulating layers and conductive layers) are laid on the wafer (foundation), similar to “painting” or “tiling” the foundation.
2. Photolithography (the most critical step): A layer of light-sensitive “photoresist” is applied to the wafer (like applying light-sensitive ink); then ultraviolet light is shone through a “mask” (equivalent to a photographic negative with the circuit diagram) onto the wafer. The areas where the mask blocks light remain unchanged; finally, a chemical solution washes away the exposed photoresist, and the circuit diagram is “copied” onto the wafer.
3. Etching: Using chemical or physical methods, the silicon or thin film not protected by photoresist is “carved out”, akin to sculpting according to the copied pattern.
4. Ion implantation: Chemical impurities are injected into specific areas to alter the electrical properties of silicon (creating P-type or N-type semiconductors, which are the core of transistors), similar to giving certain areas of the city “special attributes”.
5. Repeating the above steps: A chip has dozens of structural layers, so the above steps must be repeated dozens of times, each time using different masks, ultimately constructing a three-dimensional “nano city”.
After manufacturing, the wafer will be filled with hundreds or thousands of identical small chip squares, called “Die”.
Stage Three: Packaging and Testing—Settling the Chip and Conducting a “Health Check”
This step ensures the chip can function properly and guarantees quality, divided into four steps:
1. Preliminary testing: Precision probes check the functionality of each “Die” on the wafer, marking any that are defective.
2. Cutting the wafer: Like cutting a cake, the wafer is sliced into individual “Die”.
3. Packaging the chip: The good “Die” is fixed onto a substrate, with extremely fine gold wires connecting the “Die” interfaces to the substrate pins, finally encased in a black plastic shell (or other materials). This becomes the “chip” we usually see—equivalent to adding a “skull (shell)” and “nerve endings (pins)” to the chip’s “brain”, allowing it to communicate with external devices.
4. Final testing: Comprehensive functional and performance tests are conducted on the packaged chip, and only those that pass can be shipped out to be installed in mobile phones, computers, and other devices.
Fabrication: It is the first trial production after chip design, and the core is to verify whether the design is correct, making it the most expensive and critical step in R&D.
The complete process: Design (drawing the blueprint) → Manufacturing (using photolithography, etching, and other processes to “carve” circuits on silicon wafers) → Packaging and Testing (settling the chip and conducting a health check).
Through this process, a small chip can transform from design to a usable product, hoping to help you intuitively understand the logic of chip manufacturing~