Process and apparatus for real-time determination of a solid sample composition as a function of the depth within the sample

Process for teal-time determination of a solid sample composition which comprises:

• (a) forming a glow discharge (16) of atoms sputtered from an exposed area (17) of the sample (13) and analysing the glow discharge by optical emission spectroscopy;
• (b) measuring the distance between said exposed area (17) and a fixed reference surface (12a) and determining from the measured distance the depth of the exposed area within the sample;
• and
• (c) correlating the determined depth of the exposed area with the glow discharge analysis
• (d) calculating a theoretical depth of the exposed area (17) within the sample after step (a) using classical algorithms based on sample density estimation;
• and
• (e) comparing the determined depth of step (b) with the calculated theoretical depth of step (d) to decide whether or not there is a clear error in the estimated sample density as indicated by a significant difference between the determined and calculated depths.

Process for real-time determination of a solid sample composition which comprises:

• (a) forming a glow discharge (16) of atoms sputtered from an exposed area (17) of the sample (13) and analysing the glow discharge by optical emission spectroscopy;
• (b) measuring the distance between said exposed area (17) and a fixed reference surface (12a) and determining from the measured distance the depth of the exposed area within the sample;
• and
• (c) correlating the determined depth of the exposed area with the glow discharge analysis,
• and the sample (13) is a multilayer sample, thickness of the sample layers are approximately known, each layer contains at least a known element which can be used as an indicator of the layer, and steps (b) and (c) are carried out each time an indicator is highlighted, thereby obtaining a precise determination of the positions of the layers within the sample as well as an accurate measurement of their thicknesses.

Apparatus for implementing the process according to anyone of the preceding claims which comprises:

• means (10) for creating a glow discharge of atoms sputtered from an exposed area (17) of a sample (13) to be analysed;
• means (20) for spectroscopically analysing the glow discharge;
• means (18, 19, 20) for measuring the distance between said exposed area and a reference surface (12a) said means comprising a laser interferometer;
• means (30) for determining from the measured distance the depth of the exposed area (17) within the sample (13) and correlating the glow discharge spectroscopic analysis with the determined depth of the exposed area.