There are hints in that quote that TSMC has been under pressure to make this announcement from both the US government directly and indirectly through its leading customer Apple, to create a leading-edge fab in the United States. Apple alone was responsible for about 23 percent of TSMC's sales in 2019, according to reports (see HiSilicon breaks into top ten chip vendor ranking).
TSMC is general prefers to keeps its manufacturing in large clusters of fabs on its native island of Taiwan. It does have one US wafer fab – in Camas, Washington. This is there for legacy reasons and is left over from a joint venture operation called WaferTech established in 1996. The original partners – Altera, Analog Devices and ISSI – wanted local manufacturing and guaranteed supply during times of allocation but subsequently dropped out of the joint venture. This left WaferTech as a wholly-owned subsidiary of TSMC and TSMC's only US wafer fab.
If it goes ahead an Arizona facility would be TSMC’s second manufacturing site in the US although it has design centers in Austin, Texas and San Jose, California. TSMC also has wafer fabs in Nanjing and Shanghai, China.
However, the planned Arizona fab is not large by TSMC's standards
The Arizona fab is due to follow on from TSMC's Fab 18 at Tainan in the south of Taiwan scheduled to begin producing 5nm silicon in 2020. That fab is due to be built out in three phases over several years. But once all three enter production the facility’s estimated annual capacity will exceed one million 12-inch wafers, approaching 100,000 wafer starts per month.
The planned investment for Fab 18 is NT$500 billion or about US$16.6 billion. In October 2019 TSMC was reported to have broken ground for a 3nm wafer fab that would be completed in 2023 with an anticipated lifetime cost $19.6 billion.
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