I don't think of lit review as being a phase, rather a continuous process. I read journals, conference papers and things from the internet regularly, a little each day. I think doing it solidly would be very boring for me!
And, at the risk of being pedantic, I think it is more relevant to talk about an interdisciplinary PhD topics rather than interdisciplinary subjects. My topic is 'computer-aided knitwear design', my supervisor is a computer scientist, but as well as articles from computer science (case-based reasoning) I sometimes read ones in knitwear, engineering/design, and psychology. Many articles in computer science are completely irrelevant to me.