Chips Tracked in Fab by Wi-Fi
Freescale furthers the removal of humans from the chip-making process
28 September 2007—Freescale Semiconductor has found another way to extend the life of its fabs, some of which are 15 years old—a truly geriatric age in an industry that routinely pronounces its US $3 billion production facilities obsolete after five years. The chip maker is automatically tracking wafers through all stages of fabrication by marking boxes with RFID tags that communicate using Freescale’s existing Wi-Fi infrastructure. This is the first time Wi-Fienabled active RFID tags have been used to automate a fab.
AeroScout, in Redwood City, Calif., supplied the RFID tags that Freescale is using in its Oak Hill plant in Austin, Texas. Like most fabs, Oak Hill, which processes 200-millimeter wafers, is about the size of two football fields. In a standard facility, it’s almost impossible to immediately distinguish one black box of wafers from the other hundreds of very similar black boxes. ”Just think about having to look for one box with an identical black-and-white label in a bunch of identical black boxes,” says Freescale spokesman Glaston Ford, ”versus being able to punch an ID code into a computer, activate a box’s LED display, walk over to the right shelf, and see the right box glowing.”
In Freescale’s new system, boxes are tagged with the LED labels, which transmit a constant signal. A technician who needs to locate a box punches an ID code into a computer and the box’s location is displayed on the workstation. The employee goes directly to that rack or shelf, where a multicolored, glowing label pinpoints the box. A search that can normally take 5 minutes now takes just seconds.
To put Freescale’s innovation in a larger context, consider that the current cost of building a fab is estimated at between $1 billion and $3 billion. To get the most return on the investment, chip makers must have fabs up and running constantly and at full speed, but any manufacturing step that involves a human can slow or even stop the process. That motivates chip manufacturers to automate every process they can.
Aging manufacturing plants face a peculiar set of challenges: to operate at maximum capacity, they need to upgrade frequently. But because fabs are such sensitive environments, upgrades must be carefully controlled, lest unforeseen factors compromise the quality of the chips being made. (One such facility is rumored to have ruined several batches of chips, because one technician’s low-carb diet caused the increased ketones in the employee’s breath to upset the delicate chemical balance in the clean room.) Yet a company can’t stop production for long periods of time to install new infrastructure while everything is tested, modeled, and retested.
AeroScout’s Active RFID tags finessed several problems at once for Freescale. Because the tags work with Freescale’s existing Wi-Fi infrastructure and do not require a special dedicated frequency, the company avoids any potential radio interference with sensitive manufacturing equipment. Using the harmless 2.4-GHz Wi-Fi also eliminated the need for costly and invasive rewiring.
”The payback has exceeded our expectation,” Freescale’s Ford reports. He would not give exact figures but said that Freescale is working on implementing the system in its six other factories, and AeroScout says that other semiconductor manufacturers have expressed interest in adopting the technology for their older fabs.