According to wikipedia, it's 180nm:
But I think they may be referring to the Prop 2, as Beau said Prop 1 die photo is 350nm:
In addition, 350nm only needs 3.3v whereas 180nm requires 1.8v, so this is consistent.
By the way, are all 3.3v chips made on a 350nm process? Or do they have some kind of voltage regulator inside?