The 28 nm lithography machine belongs to the DUV (Deep Ultraviolet) lithography machine. The DUV lithography machine uses an ultraviolet light source with a wavelength of 193 nanometers, which enables chip fabrication with a minimum line width of about 28 nanometers. In contrast, the EUV (Extreme Ultraviolet) lithography machine uses an extreme ultraviolet light source with a wavelength of 13.5 nm, which can achieve a smaller line width, but the EUV technology is not yet fully mature, and commercial applications still face some technical and economic challenges. Therefore, the main lithography technology used in the 28-nanometer lithography machine is DUV.