Why are Silicon Wafers Round?


October 22, 2015

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This is certainly an interesting question, and is one that is popular among those who are not studied in science but do notice that many silicon wafers are not square or rectangular in shape.

It would seem to make perfect sense, and reduce a lot of waste, to have silicon wafers be created in a square or rectangular shape instead of the circular disc shapes that we see.

Why don’t we do it that way? The easiest way to answer the question is to think about how a vinyl record or a compact disc, or a DVD or a Blu-ray disc, plays their music or videos.

We really can’t spin this any other way – it’s about the spinning.

For a DVD to play in a DVD player, there is a laser that stays in one place, and the disc rotates or spins so that every frame of the movie is read in proper sequence by the laser, which then converts the digital information on the disc into a frame of the movie.

The spinning is what makes the disc function properly; otherwise the laser is fixed and would just read the same frame over and over again. The most efficient spinning is a circular motion. Have you ever seen a square wheel, or a pinwheel spin in anything other than a circular fashion?

Silicon wafers are made from a spinning mechanism. Wafers are thin cuts from a single silicon crystal that is formed with an ingot is dipped into a liquid silicon “soup” and pulled out. For the single crystal to be made, the ingot is spun as it is pulled out, and the centrifugal force attracts and locks in the silicon molecules. And the molecules stay still, so it is up to the ingot to spin in order to gather the silicon, and again, have you seen anything spin effectively in anything other than a circular motion?

We’re interested in finding ways to use those unused rounded edges to maximize the efficiency of silicon wafers. If you think you have an idea, we’d love to get your feedback, just for fun. How would you like to see us use those unused edges, if we had a chance to do so?