## 3 Experimental Design and Result Analyses
Figure 13 illustrates the measurement result obtained using a laser confocal  
Figure 11: Measurement results of the tested wafer sample shown in Figure 1: (**a**) captured deformed fringe image of specular light, (**b**) captured deformed fringe image of diffuse light, (**c**) wrapped phase map of (**b**,**d**) wrapped phase map of (**c**,**e**) reconstructed cross-section of (**c**,**f**) reconstructed cross-section of (**d**,**g**) reconstructed 3-D map of the smooth wafer surface, (**h**) reconstructed 3-D map of the laser-etched groove surface, and (**i**) reconstructed 3-D shape of the whole tested wafer surface. Figure 12: Height cross-section of a surface cross-section on the wafer in Figure 1: (**a**) reconstructed cross-section profile by capturing specular light. (**b**) reconstructed cross-section profile by capturing diffuse light, and (**c**) mapped cross-section profile. microscope (KEYENCE VK-X1000) on the same measured wafer surface region. The measured average step height of the laser-etched groove in a 30-time measurement was 18.853 \(\upmu\)m. With the developed method, the measured average step height on the same wafer surface was 20.21 \(\upmu\)m, in which the measurement deviation in this case was 1.357 \(\upmu\)m.  
To further check the feasibility of the developed method on an industrial semiconductor parts with variant surface reflectivity, an IC chip was selected for measuring its surface profile. Figure 14 shows the measured results on an industrial IC surface with extreme reflectivity variance between the substrate and the metal pads. The substrate image detected by specular light is shown in Figure 14a while the diffuse image detected by diffuse light is illustrated in Figure 14b. Neither of these two images can cover the entire surface detection. With the developed method, both specular and diffuse images can be detected simultaneously and reconstructed accurately. The phase map and one surface cross-section profile can be reconstructed for smooth substrate surface regions, as seen in Figure 14c,e, respectively. Similarly, Figure 14d,f represent respectively the phase map and one surface cross-section profile of the metal-pad regions. Compared with the developed method, the traditional fringe projection method will find excessive noises measured around the IC chip's pads which are mainly reflected diffuse light areas, as seen in Figure 14g. By using the developed technique, the surface measurement of the IC chip can be successfully obtained, in which both the pad and substrate areas can be reconstructed simultaneously and accurately, as shown in Figure 14j. In other words, a significant improvement in surface profilometry of objects with substantial variance of surface reflectance can be achieved with the developed approach. Figure 13: Measurement results of the wafer obtained using a laser confocal microscope (KEYENCE VK-X1000): (**a**) 2D captured image of the wafer, (**b**) 3-D measured profile of wafer, and (**c**) one cross-section of the 3-D profile. Figure 14: Measurement results of industrial IC chip: (**a**) image captured by camera receiving specular light; (**b**) image captured by vertical camera; (**c**) wrapped phase map of tilted camera; (**d**) wrapped phase map of vertical camera; (**e**) cross-section on wrapped phase map of tilted camera; (**f**) cross-section on wrapped phase map of vertical camera; (**g**) 3-D shape of IC chip measured by tilted camera; (**h**) 3-D shape of IC chip measured by vertical camera; (**i**) measured ROI of industrial IC chip; and, (**j**) 3-D shape of measured ROI in (**i**). Figure 15a,b illustrate the cross-section of height map at Column 400 on the IC chip imaged by the two cameras in charge of capturing specular and diffuse light, respectively. With the mapping algorithm, the merged cross-section profile can be obtained, as seen in Figure 15c. The measurement standard deviations of the specular and diffuse surfaces on the IC chip are 0.602 and 1.285 \(\upmu\)m, respectively.