The "Muscle Fibers" of Lithography Machines: Rare Earth Magnets Support Nanometer-Level Precision

The "crown jewel" of semiconductor equipment, the lithography machine, is often hailed as the "pearl on the crown of human industry." However, few people know that its "pearl" status is entirely supported by rare earth magnets. EUV lithography machines require the wafer stage to move at several meters per second while maintaining sub-nanometer positioning accuracy. This "high-speed yet rock-solid" movement is made possible by the "violent output" of rare earth permanent magnets.

Neodymium iron boron (NdFeB) magnets are the core players. This alloy composed of neodymium (Nd), iron, and boron has a magnetic energy product more than ten times that of traditional magnets, earning it the title of "King of Permanent Magnets." However, neodymium alone is not enough: when the lithography machine is in operation, the motor temperature can exceed 100°C, and ordinary NdFeB magnets will "demagnetize and stop working" at this temperature. At this point, two rare earth elements, dysprosium (Dy) and terbium (Tb), come into play. They act like "high-temperature stabilizers," raising the Curie temperature (the demagnetization critical point) of the magnet from 312°C to over 400°C. Data shows that a single EUV lithography machine requires tens of kilograms of NdFeB magnetic steel, with neodymium accounting for about 30%, and dysprosium and terbium each making up 1% to 3%. These "trace elements" directly determine whether the lithography machine can scan wafers at a speed of 125 per hour while keeping the positioning error less than 0.3 nanometers (equivalent to an error of 1 centimeter in the diameter of the Earth).

More crucially, this reliance is almost irreplaceable. Currently, China accounts for over 90% of the global production capacity of the most advanced rare earth permanent magnets, and China holds 73% and 40% of the global reserves of dysprosium and terbium, respectively. Without rare earth magnets, the wafer stage of the lithography machine would become a "Parkinson's patient," and it would be impossible to stably mass-produce even 28-nanometer processes, let alone 3-nanometer ones.