Methods and systems for nanoscale imaging based on second harmonic signal generation and through-focus scanning optical microscopy

A method comprising:

• providing a first amount of probe illumination light to a semiconductor wafer at each of a plurality of focus planes within a complex, three-dimensional structure disposed on the semiconductor wafer in accordance with a first optical mode, wherein the first amount of probe illumination light stimulates second harmonic generation (SHG) light emission around material interfaces buried deep within the complex, three-dimensional structure;
• imaging a first amount of SHG light emission from the complex, three-dimensional structure to a detector at each of the plurality of focus planes;
• detecting the first imaged SHG light at each of the plurality of focus planes;
• and
• generating a three dimensional volume image of the complex, three-dimensional structure based on the first imaged SHG light at each of the plurality of focus planes;
• and
• identifying a buried defect or estimating a value of a parameter of interest characterizing a buried structure based at least in part on the three dimensional volume image.

A system comprising:

• an illumination subsystem that provides a first amount of probe illumination light to a semiconductor wafer at each of a plurality of focus planes within a complex, three-dimensional structure disposed on the semiconductor wafer in accordance with a first optical mode, wherein the first amount of probe illumination light stimulates second harmonic generation (SHG) light emission around material interfaces buried deep within the complex, three-dimensional structure;
• a collection subsystem that images a first amount of the SHG light emission from the complex, three-dimensional structure to a detector at each of the plurality of focus planes in accordance with the first optical mode, wherein the detector detects the first imaged SHG light at each of the plurality of focus planes;
• and
• a non-transitory, computer-readable medium storing instructions, that when executed by one or more processors, cause the one or more processors to:
• generate a three dimensional volume image of the complex, three-dimensional structure based on the first imaged SHG light at each of the plurality of focus planes;
• and
• identify a buried defect or estimate a value of a parameter of interest characterizing a buried structure based at least in part on the three dimensional volume image.