**4. Conclusion**

results shown in **Figure 11** have different forms because different surface tensions are generated when fixing this film sample in these two separate measurements. Both 3D and 2D surface topography results demonstrate that LSDI is capable of detecting most of defects as the CCI

**Figure 11.** Defects detection on the Al2O3 ALD barrier film surface: (a) 3D surface map result using CCI and (b) result

**Figure 12.** 2D view of defects on the Al2O3 ALD barrier film surface: (a) CCI result and (b) LSDI result.

Defect 1 0.17 × 0.15 0.16 × 0.15 Reference point (0, 0)

**Table 1.** Defects' specifications (size, location).

**Size width × length (mm) Position (x, y) (mm) WLCSI CCI WLCSI CCI**

Defect 2 0.03 × 0.04 0.03 × 0.04 (0.61, 0.21) (0.62, 0.19) Defect 3 0.05 × 0.03 0.05 × 0.03 (1.29, 0.36) (1.30, 0.30) Defect 4 0.05 × 0.03 0.04 × 0.03 (1.90, 0.24) (1.92, 0.16) Defect 5 0.12 × 0.14 0.12 × 0.14 (1.24, 0.23) (1.25, 0.18) Defect 6 0.08 × 0.06 0.08 × 0.05 (1.36, 0.07) (1.37, 0.00) Defect 7 0.10 × 0.09 0.10 × 0.09 (1.68, −0.03) (1.68, −0.10)

does and the relative positions between each defect are well matched.

using LSDI.

56 Optical Interferometry

Two case studies for online surface measurement by means of interferometry have been discussed. The first case study presents a surface measurement technique with active control of environmental noise and disturbance. Nanometre accuracy surface measurement results have been obtained for micrometre step height samples. Disturbance has been reduced by 12.2 dB at 40 Hz vibration frequency. The second case study presents a line-scan dispersive interferometer with a good lateral resolution and nano-scale measurement repeatability. It has an extended axial measurement range by dispersing the output of the spectrometer along the camera pixels, without the 2π phase ambiguity. Free from any mechanical scanning and obtaining a surface profile in a single shot allows this set-up to minimize the effect of external perturbations and environmental noise.
