The one thing you must be using for such a photo is special lights. Many studios specializing in those types of photos do not even use a DSLR but a fixed-lens camera. The quality needed for a passport photo is limited considering how small the print is. There are however strict rules, depending on the country passport photo requirement.
Mostly here in Canada, the background must be white with no visible shadows. A built-in flash will do that since it projects light right from the camera position. There must also not be any shadow on the face which is causes by an small light-source, which again your flash is.
Therefore a reasonably minimal setup with be to have a background light and another diffuse light to illuminate the subject. A typical example is a strobe reflected into or through an umbrella.