You must pass both JEE Mains Papers(1 & 2) and  should also qualify with a good rank in JEE Advanced(i.e. CML Rank) in order to be eligible for AAT for IIT. This is because JEE Advanced is the main paper on which you are judged for admission into ant IIT. Scoring good marks in AAT will make you eligible for B.Arch/B.Des programs in IITs. But still your JEE Advanced Rank is required for admission, as there is no score in AAT(just qualify/disqualify).
The link below will provide you with further related details:

https://engineering.careers360.com/articles/jee-advanced-aat/amp