The current chip is using copper baseband, that is, using copper as the wire in the chip. A copper atom is more than two nanometers in diameter. So the lithography machine can only go to 3 nanometers. If you want to break through 3 nanometers, it is only necessary to abandon the existing baseband system, choose elements with smaller diameters, and must have a certain melting point, which is why many people are optimistic about carbon baseband. By the way, with the current computer system, the thread width can never be less than 1 nanometer.