A semiconductor device has a semiconductor die containing a base material having a first surface and a second surface with an image sensor area. A masking layer with varying width openings is disposed over the first surface of the base material. The openings in the masking layer are larger in a center region of the semiconductor die and smaller toward edges of the semiconductor die. A portion of the first surface of the base material is removed by plasma etching to form a first curved surface. A metal layer is formed over the first curved surface of the base material. The semiconductor die is positioned over a substrate with the first curved surface oriented toward the substrate. Pressure and temperature is applied to assert movement of the base material to change orientation of the second surface with the image sensor area into a second curved surface.