Hi Mayur,

Both of these branches are good branches but for placement point of view, biotechnology is ahead of that of civil engineering. But before that, I would like to highlight one of the most important point, that for any engineering branch placements one the most important thing for placements is the college from which you have studied. If you have studied from some Top NIT or IITs or GFTIs then there's a high possibility that you will make it to any big company with any of the aforementioned branches but if the college is not a good one then you will struggle to find a decent job. However, in such a case you will find it easy to get a placement in biotechnology as compared to civil engineering. 

The main reason for this is that biotechnology is an advanced branch of engineering and only a handful of colleges are providing this branch in their curriculum. This reduces the competition and hence the chances of placements increases.

But as I have said it earlier that you should try to make it to a good college as it is only then you have an upper hand in placements. For the admission process in NITs and IITs, you have to give JEE main exam. Here are the details of the exam:- https://engineering.careers360.com/exams/jee-main

Some other helpful links:-

https://engineering.careers360.com/articles/how-prepare-for-jee-main

https://engineering.careers360.com/articles/nits-cutoff-for-top-btech-branches

Hope this helps.

ALL the best. Thank you.