They used to call that "falsetto."
But yeah, they had (and I'm sure you can still find) very expensive hardware solutions, or you could try a harmonizer, or some software (which will definitely have artifacts).
But the real question is "Why?" If you need a female voice, not for some comedy bit or experimental reason, the quickest and best way is to get a female vocalist or voice-over artist in there (as posted above).
GJ