Before a semiconductor can be built, silicon must turn into a wafer. This begins with the growth of a silicon ingot. Growing a silicon ingot can take anywhere from one week to one month, depending on many factors, including size, quality, and the specification. Let’s take a deeper look at silicon wafer processing and how exactly they are made.
To grow an ingot, the first step is to heat the silicon to 1420°C, above the melting point of silicon. Once the polycrystalline and dopant combination has been liquefied, a single silicon crystal, the seed, is positioned on top of the melt, barely touching the surface. The seed has the same crystal orientation required in the finished ingot.
Once the ingot is fully-grown, it is ground to a rough size diameter that is slightly larger than the target diameter of the final silicon wafer. After passing a number of inspections, the ingot proceeds to slicing. Because of the silicon’s hardness, a diamond edge saw carefully slices the silicon wafers so they are slightly thicker than the target specification.
The final and most crucial step in the manufacturing process is polishing the wafer. This process takes place in a clean room. To help maintain this level of cleanliness, the workers must wear cleanroom suits that cover their body from head to toe and do not collect or carry any particles. They also stand under a fan that blows away any small particles that might have accumulated before entering the room.
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