|
If metrology doesn't add value to your fab, then why don't you stop using it? |
|
|
|
Oct 12, 2006 at 08:49 AM |
"Metrology doesn't add value--it's a necessary evil." Few more wrong-headed cliches are spouted in the semi fab world.
A presentation on metrology's return on investment by ISMI's Ben Bunday at the consortium's manufacturing effectiveness symposium yesterday in Austin provided more compelling evidence that it's time to recognize that the wise use of metrology separates world-class chip factories from the rest of the pack.
What are some examples of where metrology enables the manufacturing process? Although there are many, Bunday focused on metrology's critical dimension (CD) roles, such as the calibration and verification of optical proximity correction (OPC) models, litho tool qualifications, in situ CD monitoring of gate trim-etch, and feedforward of gate CD to diffusion. He spent a major portion of his talk on the alphabet soup of OPC, DFM (design for manufacturing), and APC (advanced process control), crucial elements in the 21st-century fab-process tool bag which would not be possible without well-matched, accurate, and precise metrology systems.
Bunday said that a fab with a good metrology approach finds the best equipment for the application, and keeps the tool matching well maintained and the accuracy tightly calibrated. A bad approach pays too-little attention to finding the right gear for the right application, slacks off in the matching department, and ignores accuracy considerations. Using fleet measurement precision (FMP, yet another initialism from the bottomless bowl of alphabet soup), Bunday showed data that good metrology can keep FMP in the 0.5-nm neighborhood, while less-good metrology practices can only hit an FMP of 1.5 nm. The biggest challenge, he noted, is matching, in terms of pushing the ever-important "ultimate error uncertainty" down in the fab and thereby improving the process control and yield potential of tighter processes.
Data shown by Bunday underscored that those with the good sense to employ a top-notch metrology strategy--with the best metrics, expertise, and metholodologies--will reap more dollars. When comparing two fabs, one with a sound strategy and the other with a less-than-solid one, the metrology-saavy fab's would save $38 million in potential lost revenue at 90 nm compared to the slacker fab, with the numbers escalating to $73 million at 65 nm, and a whopping $132 million at 45 nm. It seems that the more complex and advanced the process, the more important metrology becomes to a fab's dollar flow.
As if much more evidence were needed, those kind of revenue pops put the lie those who still believe that metrology adds no value to the bottom line.
|
Blogs 
