I recently had an interview with a professor regarding a PhD opening in their research group, for which I applied and successfully interviewed. The professor has offered me the opportunity to pursue a PhD at their university, which is located in the USA. While the university is excellent, I have always had a personal goal to attend a university ranked in the top 100, and eventually progress to a top 20 or even higher-ranking institution. However, since a PhD will be the final degree in my academic career, I am keen to have an affiliation with a prestigious university such as Caltech, MIT, Stanford, and others.
My question is how I can approach the professor to inquire about the possibility of funding for a master's degree only. I want to clarify that my interest in pursuing a master's degree elsewhere is not due to any concerns about the research quality or the professor's group. In fact, I greatly admire their work. My main concern is fulfilling my aspiration of being affiliated with a highly ranked university.