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Does size matter? Understanding Wafer Size

October 23, 2012, anysilicon

size-matters

Silicon wafers are the most essential element in the realization of ICs. The semiconductor industry had invested heavily to increase the wafer size during the last 30 years, so while foundries used to produce 1 inch wafers, today’s common wafer size is 300mm (118 times larger than 1 inch). There is a clear plan to move towards a 450mm wafer size (1.5 times larger than 300mm).

Increasing wafer size is not a trivial process. As a matter of fact, silicon wafer manufacturing technologies were re-engineered in order to achieve the technology necessary to increase the wafer size during the years. It is difficult to grasp the amount of capital invested in the size growth innovation. My guess is around a triple-digit Billion USD.

Why does wafer size matter?

A larger wafer diameter enables producing more semiconductor devices from a single wafer, enhancing productivity and efficiency. If foundries would still produce 1 inch wafer today, there is no chance they’d be able to support the volume of smart-phones, tablets and PCs.

Common Mistake: 300mm wafer is NOT 12 inch!

Wafer diameter was traditionally noted in inches, but today’s ‘correct’ figures use millimeters and they describe the wafer diameter; the following table shows the correct size of the wafer.

One of the common mistakes in the  industry is the actual physical size of the 300mm and 450mm wafers. Many seem to automatically use the inch metrics and announce “12 inch” and “18 inch” accordingly.

This is absolutely incorrect. A 300mm wafer is actually 11.8 inch.

So next time you hear someone referring to 12 inch wafer, use this info to correct the misunderstanding.

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  • george storm says:

    Wafer size made a huge difference to cost/die in the days when you could expose a whole wafer in a single flash. Since the individual exposures became decoupled from wafer size wafer size has mainly been a competitive-cost parameter*. So far as I can judge, the intrinsic die-cost difference between manufacture on even 6″ and manufacture on 18″ would be less than 30%; naturally, once you make the decision to design the high-resolution equipment for the larger diameter the 6″ wafer won’t be making best use of the equipment.
    Regarding correcting people who use the inch convention – that would be ignorant in both senses of the word. We can assume that professionals know that sizes have been rounded to mm (and nominal tolerances +/-0.5mm) since the 4″ node (pace variations at the specialist 5″ node).
    *Even uniformity across the die would be adequate except where required for speed-selection…

  • For additional 450 indepth information, visit the SEMI 450 Central website (www.semi.org/450). It features industry news, viewpoint articles, new product announcements, SEMI Standards updates, presentations, and other relevant information on 450mm wafer processing.


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