Method for classifying unknown particles on a surface of a semi-conductor wafer

A method for classifying unknown particles on a surface of a semiconductor wafer, comprising:

• applying SiO2 particles of different sizes in the form of a suspension of the SiO2 particles in a liquid to a test wafer, ascertaining a size of a plurality of the SiO2 particles, and recording a spectrum of an energy-dispersive x-ray spectroscopy of the plurality of the SiO2 particles;
• subsequently respectively ascertaining a substantive content of the plurality of the SiO2 particles therefrom, and constructing a best-fit curve of size and substantive content of the plurality of the SiO2 particles;
• and
• ascertaining a particle size of an unknown particle by means of an electron microscope, recording a spectrum of an energy-dispersive x-ray spectroscopy of the unknown particle, and determining therefrom the substantive content of the unknown particle on the semiconductor wafer, and classifying the unknown particle as the result of the comparison of the size and the substantive content of the unknown particle with the best-fit curve;
• wherein the semiconductor wafer comprises silicon;
• and
• wherein the particles are in a size range of 20 nm-200 nm.