In the world of nanotechnology, where tiny chips play a crucial role, the question of their shape always piques curiosity. Why are wafers, the foundation for creating chips, circular, while the chips themselves are square?
Chip manufacturing, a cutting-edge field in modern technology, is a complex and challenging process. From raw materials to the final product, each step requires high precision and sophisticated technology.
The raw material for chip production is silica (silicon dioxide) with a high silicon content. First, this raw material must be melted in a graphite crucible, then refined and undergoes the Czochralski process to create a cylindrical silicon ingot. This process helps eliminate impurities and produces high-purity silicon required for chip manufacturing.
The raw material for chip production is silica (silicon dioxide) with a high silicon content.
Most silicon wafers today are produced using the Czochralski method. This process begins by dipping a small silicon crystal into molten silicon. As this crystal is pulled upwards, it rotates simultaneously, creating a large cylindrical single-crystal silicon ingot.
From this silicon ingot, engineers will cut, grind, and polish to create wafers – circular, flat, and smooth silicon discs. These wafers are then sent to semiconductor fabrication plants for photolithography and etching steps to create complex logic circuits on their surfaces. This process fills the wafers with chips.
Wafers are circular, flat, and smooth silicon discs.
The circular shape maximizes the use of molten silicon and minimizes waste. The uniform pulling process helps distribute stress evenly across the material, reducing the formation of defects in the crystal. Cutting a cylindrical ingot into circular slices is simpler and more efficient than other shapes.
Finally, after rigorous testing, the wafers are sliced to obtain the square chips we see daily. The reason for selecting round wafers is that the circular structure can withstand uniform stress during cooling, cutting, and processing, thereby reducing the likelihood of breakage or damage.
While cutting the chips does generate some waste, this waste is acceptable considering the efficiency and stability of the overall production process. So, how many chips can be produced from a 12-inch wafer?
The surface area of a 12-inch wafer is about 70,659 mm². If a chip is 100 mm², theoretically, it could produce over 700 chips, but this is not feasible.
The reason, as mentioned earlier, is that since chips are square and wafers are round, there will inevitably be some scraps that will be discarded. Therefore, if we calculate based on an 85% semiconductor utilization rate, approximately 600 chips can be produced. However, considering factors such as yield rates, the actual number of chips produced is around 500.
Cutting a cylindrical ingot into circular slices is simpler and more efficient than other shapes.
Most integrated circuits are designed in rectangular or square shapes. Dividing a round wafer into square chips maximizes the wafer’s surface area. Additionally, square shapes facilitate the packaging and assembly of chips onto circuit boards. Since circuit boards are typically rectangular, square chips can be easily placed into corresponding positions.
Of the 500 chips, some may be faulty or underperforming. Instead of discarding them, manufacturers will downgrade and maximize their utility.
For example, if a 9-core chip has one faulty core, the manufacturer will disable the faulty core and turn it into an 8-core chip. This is why we see differences between chip lines such as i9, i7, i5, and i3.
If the core is not damaged but some chip components are underperforming, such as voltage and frequency tests, the model will differ. Similarly, manufacturers will categorize them under various labels such as i9-10900F, i9-10900T, i7-10700K, etc., with the main goal of minimizing waste.
Likewise, Apple’s M-series chips like M3 Ultra, M3 Max, and M3 Pro are also processed in this way to maximize the utility of each product.
Square shapes facilitate the packaging and assembly of chips onto circuit boards.
The circular shape of wafers and the square shape of chips are results of a complex manufacturing and design process. While there are other options, round and square remain the optimal shapes for wafers and chips today. The harmonious combination of production efficiency, design convenience, and standardization has contributed to the characteristic shapes of these electronic components.
However, as the chip manufacturing process becomes increasingly complex, the defect rate also rises. The yield rate – the number of non-defective chips out of the total produced – has become a significant challenge for manufacturers. Initial yields of 4nm chips from some companies only reached 35%, compared to 70% for more established manufacturers.
Chip manufacturing is a complex process that continuously evolves. From raw material processing, wafer fabrication, chip cutting, and testing, to the utilization and classification of chips, each step demands precision and advanced technology. Despite many challenges, chip manufacturers strive to improve processes to achieve the best performance and quality.
