Study Shows FD-SOI Most Cost-Effective Approach at 22nm

A new IC Knowledge report examines the costs of potential solutions for a foundry at 22nm.


By Adele Hars

What are you doing at 22nm? The debate is raging in the press and forums alike. Now research firm IC Knowledge has issued a report showing that from a straight cost perspective, planar FD-SOI is a better choice than bulk.

We’ve known for a while that sticking with bulk at the 22nm node would get pretty complicated. This study shows just how complicated bulk will be: about 35% more process steps. That really adds up.

Key results from IC Knowledge study of manufacturing costs at 22nm.

Real world scenarios

IC Knowledge has been doing these sorts of studies for over 10 years, so their Strategic Cost Models are tried and true.  In this case, they worked with Soitec and an independent wafer-processing consultant.

First, they determined the most likely scenarios for bulk and FD-SOI in terms of threshold voltages, gate oxides, stressors, metal layers and various design strategies. For the bulk model, they figured $130 for an epi wafer. For the FD-SOI wafers (they actually settled on two likely process strategies), they figured $500.

They applied the data to their model of a typical, well-run fab in Taiwan (they have to choose a place to accurately reflect things like labor and overhead), running 30K wafers/month at the 22nm node next year.

The Price is Right

The bottom line shows that whether you’re using standard bulk or FD-SOI, your per-finished-wafer cost is just a hair over $3000.

So for about the same price as bulk – or even less – you can get all the performance and power benefits of FD-SOI.

The IC Knowledge study doesn’t get into this side of things. But in case you missed it, FD-SOI does very well for both performance and power savings – at high and at low voltages. (See “FD-SOI: The Right Choice”.) At 0.7V, for example, FD-SOI is getting a +125% operating frequency improvement over bulk.  What’s more, if you’re on the design side, you don’t have to change your design flow, and you can re-use key IP.

The wafers are ready. The price is right. The results are fantastic. So what are you doing at 22nm?  Chances are it will be FD-SOI.

Note: the full FD-SOI cost report is available as a free download from IC Knowledge.