Method for studying a zone of an object so as to determine a mass-thickness and a composition thereof by using an electron beam and measurements of X-ray radiation intensity

Method for studying a zone of an object, the zone exhibiting a mass-thickness and comprising at least one chemical element, wherein the method comprises:

• a step of exposing a part of the zone of the object to an electron beam, wherein the part of the zone of the object is selected irrespective of the mass-thickness of the object in the part of the zone, provided the exposure step is carried out so that the electron beam is partially transmitted by the object in a manner allowing measuring for each chemical element identified, a corresponding intensity of an X-ray radiation emergent from the object on account of the exposure step,
• a step of identifying each chemical element present in the zone by virtue of the exposure step,
• a step of measuring, for each chemical element identified, the corresponding intensity of an X-ray radiation emergent from the object on account of the exposure step,
• a step of determining a value of the mass-thickness dependent on each measurement step,
• a step of determining a value of the concentration of each chemical element identified using the value of the mass-thickness determined,
• wherein the method comprises an initialization step in which an intermediate value of the mass-thickness ρz0, with ρ an assumed density and z0 an assumed thickness of the object at the level of the zone, and an intermediate value of concentration Cic of each chemical element identified are determined by choice, and wherein the method comprises an iterative cycle of steps comprising for each iteration of the said cycle:
• a step of calculating an incidence correction term Θ intended to take account of an angle of incidence θ of the electron beam and associated with the zone studied,
• a fitting step, implemented for each chemical element identified, and comprising:
• a step of calculating an incidence correction term Θim associated with the chemical element identified and intended to take account of the angle of incidence θ of the electron beam,
• a step of calculating an atomic number correction term φi for the corresponding chemical element using the incidence correction terms Θ and Θim calculated in the course of the said cycle,
• a step of calculating an absorption correction term χi for the corresponding chemical element using the incidence correction terms Θ and Θim calculated in the course of the said cycle and the atomic number correction term φi calculated in the course of the said cycle,
• a step of modifying the intermediate value of mass-thickness ρz0 using the incidence correction term Θ calculated in the course of the cycle and the incidence correction Θim, atomic number correction φi and absorption correction χi terms calculated in the course of the cycle for each chemical element and dependent on each measurement step,
• a step of modifying, for each chemical element, the intermediate value of concentration Cic of the corresponding chemical element using the intermediate value of mass-thickness ρz0 as modified in the course of the cycle, the incidence correction term Θ, calculated in the course of the cycle, and the incidence correction Θim, atomic number correction φi and absorption correction χi terms calculated in the course of the cycle and corresponding to the chemical element,
• wherein the iteration is halted when a variation, between two successive iterations of the intermediate values of mass-thickness ρz0 and of the intermediate values of concentration Cic of each chemical element, is less than an associated predetermined threshold, the modified intermediate mass-thickness value defining the mass-thickness value determined and each modified intermediate concentration value defining the corresponding concentration value determined.