The IIIT's do not come under a single governing council so it is difficult to say in general. If you have query about any particular IIIT then you have to visit the official website of that IIIT and look there or you can post another query here so that we can help you. Thank you.

Hello Gautam, As per new rule of government of india from 2016, SC/ST students are exempted from paying any fees for studying any of the IITS

Apart from this, IIIT Naya Raipur however offers a large fee relaxation to students as per performance, merit and category including 100% fees in form of stipend to SC/ST students under Chattisgarh state govt scholarships. 

You may check out the following link for list and detailed info on all the IIITs: https://engineering.careers360.com/tags/list-of-iiit-in-india