Patent ID: 6259092
Filing Date: 2001-07-10
Classification: B82Y,G01B,G01N

Abstract:
A method for determining the thickness of an overlayer which is present on a substrate, said method comprising:effectuating x-ray photoelectron spectroscopy with respect to said overlayer, wherein said effectuating includes:measuring the intensity of an Auger electron emission peak with respect to an element in said overlayer; andmeasuring the intensity of a non-Auger electron emission peak with respect to said element; andevaluating the ratio of the measured intensity of said Auger electron emission peak to the measured intensity of said non-Auger electron emission peak, wherein said evaluating includes considering said Auger electron emission peak to be attributable to the combination of:direct x-ray excitation of said substrate; andx-ray excitation of photoelectrons from said substrate;wherein said evaluating includes solving for d in the equationI.sub.Znl /I.sub.Z(A) ={K(1-exp[-d/.lambda..sub.Z (E.sub.Znl)sin .theta.]})/{(1-exp[-d/.lambda..sub.Z (E.sub.Z(A))sin .theta.])(1+I.sub.Z(A).sup.e /I.sub.Z(A).sup.x)},whereinZ represents said element;Z(A) is said Auger electron emission peak;Znl is said non-Auger electron emission peak;I.sub.Z(A) is the intensity of said Auger electron emission peak;I.sub.Znl is the intensity of said non-Auger electron emission peak;d is said thickness of said overlayer;.lambda..sub.Z (E.sub.Z(A)) is the inelastic mean free path of the Auger electrons in said element;.lambda..sub.Z (E.sub.Znl) is the inelastic mean free path of the nl photoelectrons in said element;.theta. is the angle of emission of photoelectrons with respect to the plane defined by said substrate;K is a constant which is equal to the measured I.sub.Znl /I.sub.Z(A) for an infinitely thick elemental sample;I.sub.Z(A).sup.x is a first portion of said intensity of said Auger electron emission peak, said first portion corresponding to direct x-ray excitation of said substrate;I.sub.Z(A).sup.e is a second portion of said intensity of said Auger electron emission peak, said second portion corresponding to photoelectron excitation from said substrate;[I.sub.Z(A).sup.e /I.sub.Z(A).sup.x ] equals [.pi.N.sub.s.sigma..sub.s.sup.i (h.nu.).lambda..sub.s (E.sub.s.sup.i).sigma..sub.Z(A) (E.sub.s.sup.i)] divided by [.sigma..sub.Z(A) (h.nu.)];N.sub.s is the number of atoms/cm.sup.3 in said substrate;.sigma..sub.s.sup.i (h.nu.) is the cross-section for photoelectron emission from the ith core level of said substrate;.lambda..sub.s (E.sub.s.sup.i) is the inelastic mean free path of substrate photoelectrons in said substrate;.sigma..sub.Z(A) (E.sub.s.sup.i) is the cross-section for Auger emission upon bombardment by electrons from the ith core level of said substrate; and.sigma..sub.Z(A) (h.nu.) is the cross-section for Auger emission by x-ray excitation.