Which course among MBA or M.Tech should I pursue after B.Tech in biotechnology to become a research scientist?

Obviously u need to do M.Tech not MBA. As, through MBA, you will lead in managerial line which does not suit you. But, you also have to complete your Ph.D in respective field to be a complete 'research scientist'. So, my answer is a big 'No' to MBA, although you have to go for M.Tech. Best of Luck.