How can I do PhD after Btech? please tell me the whole procedure.
Yes for sure. Since B.tech is a professional course hence it's considered equivalent to conventional masters courses like M.Sc etc.
There are various IITs which directly admit students after B.tech for PhDs ( like IIT Kanpur and IIT Gandhinagar) and many of them even prefer grad students because they are more energetic, have nominal family commitments and still inclined and in touch with academics ,when ,compared to their M.Tech counterparts.
Further I would like to tell you, even IIMs offer PhDs after B.tech, they run the course by the name of FPM (Fellow Program in Management). It's a 4–5 year program after which you even have the chance to be recruited as a faculty member in IIMs itself. The shortlisting for FPM is done on the basis of GATE/CAT/GMAT scores, followed by interview.
I hope this helps.