Which field has a better scope, architecture, engineering or computer science?

Architecture has wide scope nowadays.

I think u should join b.tech with CS branch.

going for b.tech is foolish. if you are really interested in computer Science then go for research programs like B.S in cse with specialization in cloud computing and bigdata. you can register at www.educationalservices.in

Dear, all these Branches have good Future Scope But Select your Branch as per your Interest area which will make you to generate good Future Scope also of your own....