ASML is in Eindhoven, an hour's drive north of Maastricht.
50m above sea is not that safe !
50m is a lot. Somewhere around 25-30% of the world's population lives below 50m MSL; if something were to happen that even threatened a facility at 50m, semiconductors are pretty far down our list of concerns.
The Netherlands is possibly the safest (coastal) country in the world when it comes to rising sea levels. They've been taking back land from water for centuries.