Amkor Technology plans to add nearly 646,000 square feet of cleanroom space to its semiconductor packaging and test campus in north Peoria, increasing the project’s planned investment to approximately $12 billion.
The company announced the expansion Sept. 8, saying customer commitments have already surpassed the 33,000 square meters of cleanroom capacity planned for phase 1. The newly announced phase 2 would add another 60,000 square meters, bringing the campus to about 93,000 square meters of cleanroom space.
That works out to roughly 1 million square feet of cleanroom capacity across the two phases. Amkor said phase 2 construction is expected to begin in late 2027 and be completed by the end of 2029.
Phase 1 is already under construction
Amkor’s first phase is being built in the Peoria Innovation Core after the company shifted the project to a 104-acre site there in 2025. Production from phase 1 is expected to begin in early 2028, according to company and Arizona economic-development updates.
In May, Amkor secured another 67 acres next to the original site. The company now describes the overall Arizona campus as roughly 170 acres, giving it room for the larger second phase and potential future expansion.
The campus is planned to include wafer bump, probe, assembly and test capabilities. Amkor says it will be the first U.S. high-volume production site operated by an outsourced semiconductor assembly and test provider for advanced packaging.
A project that started at $2 billion is now planned at $12 billion
The scale of the Peoria project has changed sharply since it was first announced in November 2023. At that time, Amkor described a roughly $2 billion facility expected to employ about 2,000 people.
By the October 2025 groundbreaking, Amkor had raised the planned investment to $7 billion and expanded the project to two phases. The latest announcement lifts the total planned investment another $5 billion to approximately $12 billion.
Amkor now expects the two phases to support more than 3,500 Arizona-based employees. Peoria said in May that the earlier $7 billion plan was expected to create about 3,000 jobs with an average annual salary of roughly $90,000. The new phase 2 announcement does not provide an updated average wage for the larger workforce.
TSMC and NVIDIA are part of the broader demand picture
Amkor did not identify which customer commitments caused phase 1 demand to exceed its planned cleanroom capacity. Recent agreements, however, show how closely the Peoria plant is being tied into Arizona’s fast-growing advanced-chip supply chain.
In June, TSMC and Amkor signed a 10-year agreement under which TSMC can procure advanced packaging and testing services from Amkor. That arrangement is intended to connect TSMC’s front-end chip manufacturing in north Phoenix with back-end packaging and testing capacity in Peoria.
In July, Amkor also announced a $1.5 billion multi-year agreement with NVIDIA to support advanced packaging and test development for next-generation artificial-intelligence and accelerated-computing platforms. NVIDIA’s agreement includes a prepayment intended to support expansion of Amkor’s U.S. advanced-packaging capacity.
The Sept. 8 announcement does not say how much of phase 2 is tied to any one customer, so those earlier agreements should not be read as a direct allocation of the new space.
What to watch next
The most immediate milestone is continued construction of phase 1 ahead of the planned 2028 production start. Phase 2 is scheduled to begin construction in late 2027, meaning work on the two phases could overlap.
For Peoria and the broader West Valley, the expansion raises the expected scale of a project that was already one of the region’s largest private investments. It also adds more advanced-packaging capacity near TSMC’s north Phoenix fabs, strengthening the physical link between chip fabrication and the packaging and testing work needed before finished processors reach customers.
West Valley Post is tracking Amkor, TSMC and other semiconductor suppliers on its TSMC & West Valley Semiconductor Supplier Tracker.
Featured image: Representative semiconductor cleanroom. NASA Glenn Research Center photo via Wikimedia Commons, public domain. The image does not depict Amkor’s Peoria campus.
