Hi there,

You can become a scientist in abroad after completing IIT as well. And most of the scientists in drdo, barc, or isro are mostly engineers or doctors as the work . Even the physics or chemical scientists also have to complete their bachelor's degree in bsc or btech then they choose to pursue phd to grow as a scientists.

Even in Abroad you will require the bachelor's degree and if it would be of IIT then you would get some benefit as well.

The salary are also very good of the scientists across the globe.

I hope this helps