Could a subtractive mechanism work? For example, if you want to create a 5nm bump, but you only have a 20nm thick tool to draw bumps, you could draw "everything except the 5nm bump".

In other words, draw a 20nm thick annulus around a 5nm center, thereby having achieved the desired result: drawing a 5nm object with a 20nm tool.

That's a toy example, idk quite how that would translate to photolithography.