Deep 3D Optical Metrology

Confocal technique and white light interferometry have demonstrated to be suitable for characterization of transparent thick films. Layer's thickness and 3D topographies of its upper and lower interfaces can be determined from the two peaks in the confocal axial response or from the two sets of interference fringes developed during a vertical scan. Refraction index mismatch between immersion medium and layer worsens the performance of these techniques when profiling lower surface.