What Is “Dopant” in Regard to a Silicon Wafer?


February 8, 2016

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We generally do not like to be called dopes. Nor do we want to call others dopes. And doping has a negative connotation since it usually implies some form of cheating in sports. But a dopant? Or doping agent? Now, we’re talking some good stuff here!Not to be confused with dopes or doping, a dopant is what is used to help produce conductive electricity in semiconducting substances for electronics. Why is it called a dopant? And why is it needed?

Natural-state Silicon In its most common state, silicon as an element is a semiconductor of electricity, but you generally do not find it all by itself – it is often connected to some other element such as hydrogen, oxygen or carbon (in a few cases). A silicon wafer is supposed to be made of pure silicon in order to maximize the element’s conductivity. But the partner element doesn’t just fall away. A process is done to draw out the pure silicon.

The Role of Dopant In the process of drawing out the silicon, a pure trace element such as boron or arsenic may be put into a silicon “soup” that contains impure silicon. As the dopant is placed into this “soup,” the silicon molecules react to the dopant and start clinging to it. The dopant is spun and slowly drawn out of the “sup,” and it brings the silicon out with it, almost like a chain that creates a circular shape. The dopant, in other words, purifies the silicon, which prepares it for use as a wafer. The monocrystalline silicon form that is created is then cut into very thin wafers, and the hundreds or thousands of transistors are etched onto the surface of each wafer. The way it is easy to distinguish a dopant from doping is that a dopant purifies something that is impure, while doping “muddies” or “dirties” whatever is pure. Now you can be a science geek around your friends and clarify that point, just in case anyone decides to bring it up at the next cocktail party. And you can call him or her a “dope” for getting “dopant” and “doping” confused. If you want to keep this friend, though, we probably would encourage you to keep the name-calling to yourself, for the sake of harmony.

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