Some light research shows that it would cost closer to 3-4 billion dollars to build a fab from 2014[1] This makes a good bit of sense since the clean rooms required are massive and require a good bit of work to get right. Also from my experience with auditing PCB manufacturing in the united states. 100M might be able to get you a old TI Fab to make some TTL Parts at.

[1] https://en.wikipedia.org/wiki/Semiconductor_fabrication_plan...