Nano-level 3-D measurement system using 3-wavelength laser light interference

To improve the productivity of very large scale of LSIs or large LCD panels, the nano-level measurement to inspect the LSIs is required. To meet with these requirements, a nano-level 3D shape extraction method has been introduced and the measurement results are described. To extract a nano-level 3D shape, the method using laser interference images is effective. Interference image is produced by light reflected by LSI and by reference mirror. At this time, if the position of reference light is changed at regular intervals, the brightness of same coordinate of interference images change like a sine wave. When position heights of LSI differ between two coordinates, the brightness of interference image differs and the phases of brightness pattern differ according to height between each pixel. And combining with different wavelength laser lights, different brightness is able to measure more than one wavelength. Look-up table method is used to combine the multi-wavelength laser light measurement. The experiment results show the method is able to measure more than 10 um height with 10 run accuracy.