Silicon is a chemical element that makes up almost 30% of the earth’s crust. Next to oxygen, it is the most abundant element in nature. Silicon is the most common material to build semiconductors and microchips with despite the fact that on its own, it doesn’t conduct electricity very well. Before a semiconductor can be built though, the silicon must be turned into a wafer. Let’s take a look at how a silicon wafer is made.
Growing a silicon ingot can range in time from one week to one month depending on factors such as size, quality, and specification. More than 75% of silicon wafers grow via the Czochralski (CZ) method, in which chunks of virgin polycrystalline silicon are placed in a quartz crucible along with small quantities of the element dopants. The adding of dopants gives the electrical properties needed to grow ingot.
Once the ingot has gone through its full growing process, it is ground to a size that is slightly larger than the target size of the final silicon wafer in diameter. After passing a number of inspections, the ingot is sliced by using a diamond edge saw. The diamond edge saw is used not only to slice the wafers so they are slightly thicker than the target size but also to help minimize damage to the silicon wafer.
After the wafer has been sliced, it gets lapped. The lapping process removes saw marks and surface defects from the wafer. It also thins the wafer out, relieving the stress accumulated in the slicing process.
After lapping, the silicon wafers go through the process of being cleaned and etched. Sodium hydroxide or acetic and nitric acids alleviate any microscopic cracks and/or surface damage that may have come about during lapping.
The final, and arguably most crucial step is the polishing of the silicon wafer. The polishing process takes place in a clean room where the workers wear cleanroom suits that cover their entire bodies. A fan is also blowing that blows away any small particles that might have accumulated before entering the clean room.
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