Patent ID: 7372579
Filing Date: 2008-05-13
Classification: G01B

Abstract:
1. An apparatus for monitoring a trench profile, comprising: a radiation-emitting unit for irradiating a section of a pattern surface of a substrate having trenches with an incident infrared radiation beam that comprises a plurality of measuring frequencies between a lower radiation frequency limit and an upper radiation frequency limit; an infrared radiation detection unit for measuring the intensity and/or polarization state of reflected infrared radiation beams being reflected from the section of the pattern substrate at the measuring frequencies; an analyzing unit for determining intermediate values in relation to the respective measuring frequency, such that an intermediate spectrum comprising pairs of variables is obtained from the measured intensity and/or polarization state, and wherein each pair of variables comprises a measuring frequency and a corresponding intermediate value; a processor for performing a Fourier transformation of the intermediate spectrum that obtains a second order Fourier spectrum comprising pairs of calculated variables that include: a value for a virtual amplitude, a corresponding value for a frequency periodicity that corresponds with a substrate depth, and a value for a peak of the virtual amplitude that indicates a reflective plane within the substrate, wherein the apparatus outputs the pairs of calculated variables.