hi,

see phd can be done after the course in master degree. some times dual 5 years master+ phd courses available. but it is really difficult to into ivy league colleges as you dont have any background in economics. i would suggest you to first go for master in economics, then if you can adapt it than you may do phd, see engineering and economics are two different paths , its true that we do need economical model to run a business in our engineering corporation, however it will take time to adapt the things while learning masters. please think again if you really want to do it.