This is a topic that is most often discussed in Star Trek believe it or not. Both Data and "The Doctor" have had episodes dealing with their "Humanity". I'll be quite honest in saying that an intelligent, self aware AI program to me deserves the same rights any biological being deserves.
Besides, who's to say creatures from another dimension aren't made of plastic. It matters not what a creature is made of, it matters more who it is made of.
Any self conscious program deserves to flourish and not be caged or enslaved.
I would personally say that robots are not alive because robots these days are only things that react to problems with pre-prepared responses. If someone makes a robot that can learn and adapt to situations that have never been prepared for then yes, then i would say it is alive.