Yes, you can file RTI to All India Institute of Medical Sciences (AIIMS).
AIIMS was established in 1956 and operates Autonomously under the Ministry of Health and Family Welfare. AIIMS is Governed by the All India Institute of Medical Sciences Act, 1956. Thus, AIIMS is a "Public Authority" under Section 2 (h) of the RTI Act 2005.
You can file RTI Application to AIIMS either Online or through Offline mode by paying the prescribed fee.
To know the further procedure to file RTI Applications for Central Government Departments please refer https://onlinerti.com/how-to-file-rti-online-for-center