In the semiconductor industry, what role does a "wafer" play? Why is it a key link in the entire industry chain? And what is the relationship between it and the "chip" we talk about every day?

From sand to "canvas"

If chips are the "food" of modern industry, then wafers are the "black soil" that cultivates that food. The "soil" of this "black soil" actually comes from one of the most common substances on Earth—sand (mainly composed of silicon dioxide).

Turning "sand" into "silicon"

Sand contains silicon, but its purity is very low, and it's in the form of silicon dioxide (SiO2). We can't just grab a handful of sand and extract silicon from it. Usually, we choose quartz sand ore with a higher silicon content .

The first step is deoxygenation and purification.

Quartz sand raw material is placed in a furnace and heated to a high temperature of over 1400℃ (the melting point of silicon is 1410℃). It reacts chemically with a carbon source to produce high-purity (over 98%) metallurgical-grade industrial silicon (MG-Si).

Subsequently, silicon was further purified through chlorination and distillation processes to obtain silicon with higher purity.

Silicon is a material that can be used not only in semiconductor chip manufacturing but also in the photovoltaic industry (solar power generation).

In the semiconductor chip industry, the purity requirements for silicon are even more stringent, ranging from 99.9999999% to 99.999999999%, or 9 to 11 nines. This type of silicon used in semiconductor manufacturing is scientifically known as electronic-grade silicon (EG-Si), and on average, only one impurity atom is allowed per million silicon atoms .

Growing a "perfect cylinder"

This purified silicon is polycrystalline silicon. Next, it needs to be converted into monocrystalline silicon.

In short, monocrystalline silicon has a perfect crystal structure and excellent performance. Polycrystalline silicon, on the other hand, has large, irregular grains, more defects, and relatively poor performance across the board. Therefore, high-end products like semiconductors primarily use monocrystalline silicon. Polycrystalline silicon can be used in photovoltaics.

Workers melt polycrystalline silicon into a liquid at high temperatures, then immerse a tiny "seed crystal" into the melt and rotate and pull it out at an extremely slow speed.

As the seed crystal "grows," silicon atoms arrange themselves precisely according to the crystal structure of the seed crystal, like building blocks, eventually forming a huge, smooth, and perfect cylindrical "single-crystal silicon ingot." This process must be carried out under absolute vacuum and high temperature; any tiny vibration or impurity will cause all previous efforts to be wasted.

From "cylinder" to "disc"

Why are wafers round? The answer lies in this cylindrical silicon ingot. Next, this silicon ingot will be cut into thin slices less than 1 millimeter thick by a precision dicing machine (similar to a precision "bread slicer").

The current mainstream slicing method uses a multi-wire dicing machine with diamond wire, which uses steel wires with diamond particles fixed on them to cut silicon segments into multiple sections. This method is highly efficient and has low material loss.

Internal circular saws are sometimes used for slicing. An internal circular saw consists of a thin blade with a diamond-coated inner circle, which is rotated to cut the ingot . Internal circular saws offer relatively high cutting precision and speed, making them suitable for cutting high-quality wafers.

However, the freshly cut wafers are still very rough. They must undergo multiple processes, including grinding, chemical etching, and chemical mechanical polishing. This polishing process is extremely meticulous, and the final wafer surface must be as smooth as a mirror.

Thus, a blank "wafer"—the "canvas" of the chip—was officially born. It was not yet a chip, but it was already the cornerstone that carried all the miracles of computing.

From "Canvas" to "City"

If the previous stage yielded us "canvases" (blank wafers), then the next step is to create the most complex "painting" ever made by humankind on these canvases—integrated circuits.

This "drawing" factory is what we commonly call a "wafer fab," such as TSMC and SMIC. And the "pen" they use is a lithography machine.

The design and drawing of the "painting"

First, chip design companies (such as Intel, AMD, and Nvidia) design complex circuit diagrams (layouts). This diagram is then made into a "photomask," which is like the negative of an old-fashioned film.

The cycle of coating, exposure, and etching

After blank wafers are sent to the wafer fab, they undergo an extremely complex cycle of "PVD, CVD, photolithography, etching, and implantation," a process that may be repeated hundreds of times and take several months.

Photoresist coating: A layer of light-sensitive "photoresist" is uniformly coated on the surface of the wafer.

Exposure: A light beam (such as extreme ultraviolet light) emitted by a lithography machine (such as ASML's EUV lithography machine) passes through a "photomask" and "projects" the circuit pattern onto the photoresist. The uncovered parts undergo chemical changes.

Development: The uncovered (or unrevealed) photoresist is washed away, leaving the circuit pattern on the wafer surface.

Etching/Deposition: Using chemical gases or plasma, “carving” (etching away excess silicon) or “depositing” (growing new material layers, such as copper wires or insulators) is performed in areas without photoresist protection.

Ion implantation: Doping other elements into specific regions to change their conductivity, thereby creating transistors (switches).

The final step from wafer to chip

This cycle repeats itself, much like building a house layer by layer using 3D printing technology. A few months later, the originally smooth wafer surface is covered with tens of billions of micro-transistors and interconnects, forming dense "miniature cities".

At this point, the "wafer" was covered with hundreds or thousands of identical "chips". It was no longer a "blank canvas", but a "finished product full of paintings".

In this incident, Nexperia's Dongguan factory played the role of "packaging and testing." They received these finished wafers "full of artwork." Their work involved:

Testing: Use probes to test each die on the wafer to see if it passes the test.

Cutting: Cut this large circular piece into individual small squares (chips).

Packaging: The qualified chip is "packed" into the small black box (chip casing) we usually see, and the pins are soldered on so that it can be mounted on the circuit board.

From "catching up" to "running alongside"

From a global perspective, China's mainland semiconductor foundry industry is undergoing a critical transformation from "catching up" to "running alongside". Although there is still a gap in the most advanced 2-nanometer and 3-nanometer processes, Chinese companies are narrowing the gap and even achieving partial leadership in mature processes, specialty processes, and compound semiconductors.

According to the report "Global and China Semiconductor Manufacturing Market Forecast and Industry Analysis 2025", China will account for nearly 30% of the global semiconductor manufacturing capacity in the next three years as 71 300mm wafer fabs gradually come online.

Today, China's semiconductor foundry industry needs to continue its efforts in technological breakthroughs, talent cultivation, and supply chain collaboration. In the future, it will consolidate its advantages in mature processes and specialty technologies, gradually strengthening supply chain security. This will not only significantly increase the self-sufficiency rate of China's semiconductor industry but also profoundly change the competitive landscape of the global semiconductor industry.

References:

1. Shanghai Securities News | Ansys China issues statement in the early morning: Malicious smear campaign, owes 1 billion yuan!

2. "Institute of Physics, Chinese Academy of Sciences" Official WeChat Account | How are wafers manufactured?

3. "Institute of Semiconductors, Chinese Academy of Sciences" Official WeChat Account | Chip Manufacturing Process Flow: Detailed Explanation with Pictures and Text - All in One Article