SUBSTRATE INSPECTION APPARATUS AND SUBSTRATE INSPECTION METHOD

A substrate inspection apparatus includes an optical coherence tomography (OCT) measuring device which outputs a cross-sectional image generated by optical interference between light radiated onto an organic layer on a substrate and reflected light reflected from the organic layer, a memory which stores one or more instructions and a processor which executes the one or more instructions stored in the memory, where the processor sets a reference line extending from a line in contact with one surface of the substrate, on which the organic layer is not disposed, from the cross-sectional image, measures an optical thickness from a first upper line to a lower line of the organic layer in a first area in the cross-sectional image, measures a physical thickness from the first upper line of the organic layer to the reference line, and calculate a refractive index based on the optical thickness and the physical thickness.