"Longer" if you're talking atom by atom is an understatement, you're going to almost never finish. Electron beams might be something relevant, but they're alrea

"Longer" if you're talking atom by atom is an understatement, you're going to almost never finish. Electron beams might be something relevant, but they're already being investigated. E-beam lithography is a thing, and as with all next-gen litho techniques, it too has its fair share of problems. For example, shot noise is a major problem which means that every time you halve your node, you're going to halve your throughput. This is devastating for semiconductor manufacturing, TSMC is already working double shifts trying to match demand. Also, the important thing to realize about semiconductors is that demonstrating something in the lab is a relatively easy ordeal, but making it mass manufacturable in a timely fashion with good yields is a herculean task. You can actually use X-ray litho for something more "nanoscale in origin" but it's really, REALLY difficult to make it in production.