In general, getting a phd is the best way to go but it is not the only way. "The AI Epiphany" channel by Aleksa Gordić is worth watching. Check out his origin story: https://www.youtube.com/watch?v=SgaN-4po_cA He works at DeepMind. He is self taught; without a phd.
Also check out Jeremy Howard from fast.ai - also no PhD but amazing teacher and contributes actively to research.
Chris Olah (Google Brain, OpenAI, etc) go to university at all.
PhD definitely not required.