Apple currently has its Touch ID sensors manufactured with a 12-inch process over at TSMC’s fabs, but the Cupertino giant wants TSMC to employ a new, 8-inch process to avoid yield concerns.
iPhone 5s has seen shortages because of the poor Touch ID yield rates, so Apple wants to right this wrong with the iPhone 6 and have TSMC deliver better sensors in a faster manner.
According to industry sources quoted by DigiTimes, “Taiwan Semiconductor Manufacturing Company (TSMC) will use its 8-inch processing, instead of 12-inch, to produce fingerprint sensors for Apple's next-generation iPhone due to concerns about yield rates for 12-inch wafer-level packaging (WLP).”
The manufacturing process is not without precedent. However, the sources noted that, so far, 8-inch production of the sensors has “suffered unsatisfactory yield rates limiting the availability of the 5s.”