What Determines the Dimensions of a Wafer?


January 31, 2022

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Determining wafer dimensions is an important part of the design process. The possibilities vary depending on the materials used for the wafer, along with the production process used. GaAs reclaim wafers, for instance, can have different dimensions than silicon wafers.

This decision impacts how much computing power the wafer will have, as well as what it can fit into. To take another example, a chip for a gaming computer is going to have different needs when compared to what you’d find in a smartphone.  

How Are Wafers Measured?

We used to measure wafers in terms of inches. Their ever-decreasing size has made that less and less practical, though, which is why the industry now measures wafers in terms of millimeters.

This measurement is also useful for ensuring accuracy. When measuring wafers in terms of inches, sometimes people would round up, giving an inaccurate number. Millimeters give you the information necessary to understand exactly how big the wafer is.

How Much Diameter Should a Wafer Have?

The regular decrease of transistor size has been one of the biggest trends in semiconductor manufacturing history. This was one of the major factors pushing computerized technology forward, since devices could keep getting smaller while computing power increased at a fast rate.

Currently, researchers have come up with ways to make chips 1-nm wide, though they’re still in the R&D phase. The largest chip you’ll find on the market is 3-nm.

The smaller these materials, the more of them you can fit onto a wafer. That also incentivizes researchers to come up with ways to create large wafers: the bigger the wafer, the more chips and transistors can fit onto it.

The most common wafer size is 300mm, but researchers are working to make 450 mm wafers more practical and thus more common. Currently, they range in size from 25.4 mm to 450 mm.

How Thick Should a Wafer Be?

Wafer diameter has increased over time, mainly to make it as sturdy as possible. There are several ways in which increasing its thickness makes it less susceptible to damage.

First, it makes it harder for the wafer to snap accidentally. It also ensures that the wafer can withstand high levels of heat. Finally, it helps the wafer meet the “defect kinetic properties” necessary for its structure.

The thickness of a wafer will vary based on its diameter. Today, 300-mm wafers are often 775 μm thick. If you’re unsure how thick your wafer needs to be, speak with your manufacturer. They will be able to come up with an answer specific to your needs.

Can Reclaiming Wafers Impact Wafer Size?

Yes, reclaimed wafers are often thinner than new wafers. Often, these wafers can be reused multiple times as well. We can reclaim GaAs wafers of the following sizes:

  • 2”
  • 3”
  • 4”
  • 5”
  • 6”

4” and 6” wafers are the ones that are the most reclaimed.

a worker examines one of the newly manufactured gaas reclaim wafers

Why Are Wafers Circular?

Wafers typically start out round because of how they’re grown: The Czochralski method of growing gives us circular material, which we then cut into a round shape. Any other shape would waste some of that material. Luckily, that shape also comes with several other advantages:

  • It allows us to fit more chips and integrated circuits than any other shape.
  • It allows us to rotate the wafers quickly and easily, which is important both for making the polishing process easy and for pouring photoresist onto a wafer.
  • It doesn’t have any corners, which means that weak points aren’t created when the wafer is heated.

Does the Wafer’s Circular Shape Have Anything to Do with Why It’s Called a Wafer?

Yes, the word “wafer” is derived from the Anglo-French “wafer,” which corresponds to the Middle Dutch “wafele,” which evolved into the word waffle – pastry used at the time coined the term for the shape.

Essentially, wafers got their name from their shape. This is also why they share a name with the candy. While we love the wafers we make, we don’t recommend eating them. They’re expensive and don’t taste very good!

Why Are Processors Square?

If wafers are circular, that begs the question: why are processors square? The most efficient shape we could cut for getting the most wafers per chip is a hexagon. However, hexagons would require us to cut many different lines, whereas squares or rectangles are much more efficient.

Given the fact that a hexagon is impractical given current manufacturing capabilities, we end up creating rectangular processors.

Why Does the Sheet Have to Be Cut at All?

A sheet of chips isn’t designed to fit into a device. Typically, it has much more processing power than is required, and it also won’t be compatible with the device.

Moreover, cutting the sheet is necessary because we can’t print circuits on the edge of a sheet. Instead, we need to take that sheet and cut out the circuits necessary for the device it's being manufactured for. This also gives us the opportunity to cut out some of that excess boundary material.

How Do You Know What Wafer Dimensions You Need?

Some clients come to us with an idea of the exact wafer size they need. However, we’re also happy to speak with you about what you’re looking for from your wafer. If you’re unsure what dimensions you need, we’ll provide it as part of our quote.

a worker cleans a batch of gaas reclaim wafers

Looking for GaAs Reclaim Wafers?

You’ve come to the right place! Wafer World is committed to ensuring that all our customers get the high-quality wafers their businesses need. Along with the wafers we offer on our site, we’re always happy to speak with people about what we can manufacture to best assist them.

Do you have any questions about our facility? Maybe you are looking to get a free quote on wafers specific to your needs? Please don’t hesitate to reach out to us at Wafer World via the information on our contact page. We’re excited to hear from you and are always ready to help you with any wafer need you might have.

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