Patent ID: 7355729
Filing Date: 2008-04-08
Classification: G01B

Abstract:
1. An apparatus which measures the thickness of a substrate, comprising: a sample stage, wherein the sample stage includes a first upper surface for supporting a standard sample of a known thickness; a substrate stage which supports a substrate, wherein the substrate stage includes a second upper surface positioned at substantially the same height as the first upper surface of the sample stage; a lighting unit which selectively projects light to the standard sample on the sample stage or to the substrate on the substrate stage; a first light-focusing lens which concentrates light reflected from the standard sample and light reflected from the substrate, wherein the first light-focusing lens includes a first light axis substantially perpendicular to the first upper surface and the second upper surface; a detector which detects the concentrated light reflected from the standard sample and the concentrated light reflected from the substrate through the first light-focusing lens, wherein the detector converts the light intensity of the concentrated light reflected from the standard sample and the concentrated light reflected from the substrate into a first electrical signal and a second electrical signal, respectively; a driving unit for moving the substrate stage and the sample stage, wherein: an operating unit which determines a first peak value from the first electrical signal that changes in accordance with changes in the first distance and a second peak value from the second electrical signal that changes in accordance with changes in the second distance, wherein the operating unit calculates the thickness of the substrate by using a standard distance corresponding to the first peak value between the standard sample and the first light-focusing lens, a moving distance of the substrate corresponding to the second peak value, and the known thickness of the standard sample.