Impact of Master's Degree on Physics PhD Admission in the United States: will I be held to a higher standard?
You'll be held to the same standard as everyone else - they are looking for people who are going to be successful graduate students.
You mention in a comment:

I want to stay in school longer to get more research experience

I think that's a great way to improve an application in that more research experience gives you more space to demonstrate you'll be a successful graduate student. The number or type of degree earned along the way will mean little compared to the total research and academic experience and proficiency you can demonstrate.