I am not sure - if there are no small plastic plugs or pieces of trim hiding the retaining screws (most sensible assumption) the door interior will need dismantling to access the screw heads.

A microwave door is often made up of several layers to provide light weight with rigidity and provide adequate screening against microwave escape and if dismantling is possible (not always) it really should be entrusted to a professional or at least applying the utmost attention to detail.