Raman spectroscopy is similar to infrared spectroscopy in a way that both techniques are used to identify unknown substances. Raman spectroscopy uses a laser to interact with an unknown substance. Confocal Raman microscopy combines the Raman spectroscopy with an optical microscope, which provides extra spatial (vertical and horizontal) resolution of samples. Therefore, this technique is especially useful for microscopic defect analysis. Analyses can be performed in 1D, 2D and 3D with spot sizes of less than 1,0 μm.