Organic Produce and DFM
 Above: Dummy features?identified on TI OMAP 2420 Applications Processor (Source: Semiconductor Insights) More Information |
Aren’t fruits and vegetables by definition organic? DFM - or design for manufacturability - is a common buzzword these days. Am I alone on this one too, or were we not always designing for manufacturability? If not, why did designers even use design rule manuals?
What really happened is that the semiconductor industry reached a peak where the planets aligned and there was so much standardization and repeatability in process technology and design tools that creating working IC?s became relatively simple. No one would say that getting a state-of-the-art IC to work today is a simple task. Why? Repeatability has been replaced by process variability across the wafer and within the IC. This is not suggesting that the fab guys have turned their attention to recreational drugs and the technology has gone to pot. Moore?s Law has simply pushed our industry so close to the physical limits that purely statistical fluctuations create many of the challenges to achieving acceptable device yields.
Enter DFM.
I don?t think DFM would be the media darling it is today if not for the massive industry shift to fabless or fab-light models. Why? Responsibilities are split across corporate boundaries. You create a design, then the corresponding layout files that can be written onto a mask. They take the mask design, print and pattern the wafer. What if the circuit operates below target specs? What if clock timings are out of sync? What if the test chips you get are complete duds?
Well, if your design data has not just been thrown over a wall, but also over the largest ocean on the planet along with some major language barriers, chances are that something will go wrong. So count on a long cycle from conception to volume production of working chips. DFM ? whether it?s a new EDA tool or simply a new teamwork process ? will doubtless be the difference between functional devices and a pile of useless junk. But the real success of the design will ultimately be measured by how well you hit the market window for your product.
Perhaps DFM needs to be design for marketability.
From our analysis, a lot of DFM is starting to ?stick.? Control and consistency of CMP process has required so-called dummy features for a long time, but these are becoming more critical as low-k dielectrics become softer. Dummy metal fill is also necessary to keep the chip’s layers from peeling apart.
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