Methods and systems for semiconductor metrology based on polychromatic soft X-Ray diffraction

A method comprising:

• generating an amount of soft x-ray radiation including multiple illumination wavelengths within a photon energy range from 80 electronvolts to 3,000 electronvolts;
• focusing the amount of soft x-ray radiation including the multiple illumination wavelengths onto a semiconductor wafer as an x-ray illumination beam incident on the semiconductor wafer at a nominal grazing incidence angle between 5 and 20 degrees;
• detecting an amount of x-ray radiation scattered from the semiconductor wafer in response to the incident x-ray illumination beam;
• and
• determining a value of a parameter of interest characterizing a structure disposed on the semiconductor wafer based on the detected amount of x-ray radiation.

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 80 electronvolts to 3,000 electronvolts;
• one or more x-ray illumination optical elements disposed in an illumination optical path between the x-ray illumination source and a semiconductor wafer, wherein the one or more x-ray illumination optical elements focus the amount of soft x-ray radiation including the multiple wavelengths onto a metrology target disposed on the semiconductor wafer as an x-ray illumination beam incident on the metrology target at a nominal grazing incidence angle between 5 and 20 degrees, wherein the metrology target includes an array of nominally periodic unit cells, wherein one or more structural elements of each nominally periodic unit cell is deleted at a programmed or random location within each of the unit cells;
• an x-ray detector configured to detect an amount of x-ray radiation scattered from the semiconductor wafer in response to the incident x-ray illumination beam;
• and
• a computing system configured to determine a value of a parameter of interest characterizing a structure disposed on the semiconductor wafer based on the detected amount of x-ray radiation.