Combined X-Ray and Optical Metrology

A method comprising:

• generating a geometric model of a structure of a specimen;
• generating an optical response model and an x-ray response model based at least in part on the geometric model;
• receiving a first amount of measurement data based on an amount of x-ray radiation detected from the specimen in response to an x-ray illumination beam incident on the specimen;
• determining directly a first specimen parameter value based on the received first amount of measurement data;
• receiving a second amount of measurement data based on an amount of optical radiation detected from the specimen in response to an optical illumination beam incident on the specimen;
• determining a second specimen parameter value based on the first specimen parameter value, a fitting analysis of the first amount of measurement data with the x-ray response model, and a fitting analysis of the second amount of measurement data with the optical response model;
• and
• storing the second specimen parameter value.

A non-transitory, computer-readable medium, comprising:

• code for causing a computer to generate a geometric model of a structure of a specimen;
• code for causing the computer to generate an optical response model and an x-ray response model based at least in part on the geometric model;
• code for causing the computer to receive a first amount of measurement data based on an amount of x-ray radiation detected from the specimen in response to an x-ray illumination beam incident on the specimen;
• code for causing the computer to determine directly a first specimen parameter value based on the received first amount of measurement data;
• code for causing the computer to receive a second amount of measurement data based on an amount of optical radiation detected from the specimen in response to an optical illumination beam incident on the specimen;
• code for causing the computer to determine a second specimen parameter value based on the first specimen parameter value, a fitting analysis of the first amount of measurement data with the x-ray response model, and a fitting analysis of the second amount of measurement data with the optical response model;
• and
• code for causing the computer to store the second specimen parameter value.