Patent ID: 6252670
Filing Date: 2001-06-26
Classification: G01B

Abstract:
A method for measuring photoresist thickness using a constant-angle reflection-interference spectrometer (CARIS) with more accurate Cauchy coefficients comprising the steps of:coating monitor wafers with photoresist layers having varying thicknesses formed by varying the spin speed during said coating of said photoresist layers;exposing said photoresist layers using monochromatic radiation through a mask and developing said photoresist layers to form photoresist patterns, wherein said radiation has a dose sufficient to just clear said photoresist layers during development;measuring the linewidths of said photoresist patterns and plotting said linewidths as a function of photoresist thickness to generate a critical dimension (CD) swing curve having an essentially sinusoidal shape resulting from interference between the transmitted and reflected said monochromatic radiation in said photoresist;using one of said monitor wafers having one of said photoresist thicknesses for a predetermined minimum in said CD swing curve to calculate more precisely said Cauchy coefficients for measuring said thicknesses;using said Cauchy coefficients to accurately calibrate said CARIS to measure photoresist thickness for product wafers.