By Brad Cheshire and David Brown
Semiconductors play a central role in almost all consumer goods produced today. Chips are integral to appliances, vehicles, computers, smartphones, ATMs, medical equipment, and more. The industry must double semiconductor production to keep pace with future demand, according to 2023 report by McKinsey & Company, “Semiconductor Fabs: Construction Challenges in the United States.” As a result, many companies have announced plans to build new semiconductor wafer fabrication plants (fabs), with several already under construction. Federal funding from the U.S. Chips and Science Act has accelerated this production boom.
From robust foundations to support heavy equipment and vibration isolation to cleanrooms and temperature and humidity control, the structural design of these facilities is complex. Structural engineers and architects must evaluate many factors to ensure fabs meet the stringent precision and reliability requirements of such manufacturing plants.
Vibration Sensitivity
As semiconductor chips have become smaller and more powerful, the line widths of the circuitry have been drastically reduced. Chips are now being manufactured with 7 to 14 nanometer line widths in many cases, which is far smaller than a human hair that averages 80,000 to 100,000 nanometers wide. This miniature architecture requires special attention to the structural systems and vibration isolation to make it possible to manufacture them. The impact of humans working in the cleanroom, electrical sources, mechanical sources, and even ambient sources of vibration such as highways and railroads outside the facility must be considered. Structural systems must be stiffened to prevent vibration. Large equipment such as that found in the Central Utility Plants must be separated and isolated from the cleanrooms and piping, and other utility systems must be spring-isolated to prevent transmission into the structures. Semiconductor tools must also be supported on special bases to reduce vibration. Every source of vibration, both internal and external, to the cleanroom must be identified and addressed.
Cleanrooms
Cleanroom structural design involves the implementation of airtight enclosures, advanced filtration systems, and airflow control mechanisms to maintain specified cleanliness levels. The choice of construction materials is crucial to prevent the generation of particles, and the structural support system should allow for the installation of complex HVAC systems that can regulate temperature, humidity, and particles that may impact production. Flooring and wall surfaces should also be non-porous and resistant to chemical damage to prevent even minor disturbances.
Automated Material Handling Systems
The goal to limit human contact in the wafer production process has given rise to automated material handling systems, where manufacturers of robotic networks aim to enhance efficiency. These configurations are evolving to deliver individual wafer packages precisely when and where needed within the factory. Stockers, or temporary storage shelves once inefficiently stationed on the floor, are now hung from the ceiling to save space. Robots can drop front-opening universal pods into a designated storage spot along a track, giving way to a streamlined and responsive material handling process. This shift, however, requires the design of roofs and supporting structures to accommodate heavier loads as the weight distribution of valuable semiconductor products changes from resting on the floor to hanging from overhead systems.
Resiliency, Sustainability, and Climate Change
The increasing frequency of extreme weather events and climate change have led designers to prioritize resiliency, strength, and durability when building fabs. Optimizing source materials (concrete, steel, timber, etc.) and minimizing waste is critical to future-proofing these facilities. Considering insulation thickness or incorporating lower-carbon cement or recycled steel into early design stages can help ensure structural sustainability.
Facilities also run millions of gallons of water through their systems daily to cool machinery and ensure contaminant-free wafer sheets. These water-intensive processes require innovative water reclamation and storage solutions. To support green building initiatives and adhere to environmental standards, some chip makers must build water recycling facilities to help support their operations. Many semiconductor plants also include infrastructure to store large quantities of water to reduce the impact of their peak demands on the local water supply.
Semiconductors are essential to society. With the continued growth of chip manufacturing, architects and structural engineers must work together to build facilities that meet their unique spatial needs and ensure the structural integrity required for high-precision processes. ■