Methods and systems for semiconductor metrology based on wavelength resolved soft X-ray reflectometry

A method comprising:

• providing an amount of soft x-ray radiation including multiple illumination wavelengths within a photon energy range from 10 electronvolts to 5,000 electronvolts, the amount of soft x-ray radiation directed to a metrology target fabricated on a semiconductor wafer as an x-ray illumination beam incident on the semiconductor wafer at a nominal grazing incidence angle between 1 and 45 degrees;
• detecting a first amount of x-ray radiation scattered from the metrology target into multiple, different diffraction orders in response to the incident x-ray illumination beam;
• generating a first plurality of measurement signals, each of the first plurality of measurement signals indicative of the detected amount of x-ray radiation at a different location on an active surface of a first detector, wherein each of the first plurality of measurement signals is indicative of a distinct wavelength of the multiple illumination wavelengths diffracted at a distinct diffraction order of the multiple, different diffraction orders;
• and
• determining a value of a parameter of interest characterizing the metrology target based on the first plurality of measurement signals.

A metrology system comprising:

• an x-ray illumination source configured to generate an amount of soft x-ray radiation including multiple illumination wavelengths within a photon energy range from 10 electronvolts to 5,000 electronvolts, the amount of soft x-ray radiation directed to a metrology target fabricated on a semiconductor wafer as an x-ray illumination beam incident on the semiconductor wafer;
• a first detector disposed in an optical path of a first amount of x-ray radiation scattered from the metrology target into multiple, different diffraction orders in response to the incident x-ray illumination beam, the first detector configured to generate a first plurality of measurement signals, each of the first plurality of measurement signals indicative of the detected amount of x-ray radiation at a different location on the first detector, wherein each of the first plurality of measurement signals is indicative of a distinct wavelength of the multiple illumination wavelengths diffracted at a distinct diffraction order of the multiple, different diffraction orders;
• a second detector disposed in an optical path of a second amount of x-ray radiation scattered from the metrology target into one or more different diffraction orders in response to the incident x-ray illumination beam, the second detector configured to generate a second plurality of measurement signals, each of the second plurality of measurement signals indicative of the detected amount of x-ray radiation at a different location on the second detector, wherein each of the second plurality of measurement signals is indicative of the one or more different diffraction orders;
• and
• a computing system configured to determine a value of a parameter of interest characterizing the metrology target based on the first and second plurality of measurement signals.