Measuring a height profile of a hole formed in non-conductive region

A computer program product that stores instructions that, once executed by a computerized system to measure a hole having a nanometric width formed in an object, causes a particle imager that includes a secondary electron detector and an energy filter disposed between the object and the secondary electron detector to perform the steps of:

• charging a portion of the object in a vicinity of the hole with a charged particle beam;
• obtaining a plurality of electron images of the hole with the charged particle imager, wherein each electron image in the plurality of electron images is obtained by:
• (i) setting an electron energy threshold of the energy filter to block electrons having an electron energy below the energy threshold level from reaching the secondary detector;
• and
• (ii) sensing, with the secondary detector, electrons having an electron energy that exceeds the electron energy threshold associated with the electron image;
• wherein the electron energy threshold is different for each electron image in the plurality of electron images;
• receiving or generating a mapping between height values and the electron energy thresholds;
• processing the multiple electron images to provide hole measurements;
• and
• generating three dimensional measurements of the hole based on the mapping and the hole measurements.

A particle imager for measuring a hole having a nanometric width formed in an object, the particle imager comprising:

• a stage to support the object;
• a secondary electron detector;
• an energy filter disposed between the object and the secondary electron detector;
• a processor and a memory that stores instructions that, once executed by the processor, cause the particle imager to:
• charge a portion of the object in a vicinity of the hole with a charged particle beam;
• obtain a plurality of electron images of the hole with the charged particle imager, wherein each electron image in the plurality of electron images is obtained by:
• (i) setting an electron energy threshold of the energy filter to block electrons having an electron energy below the energy threshold level from reaching the secondary detector;
• and
• (ii) sensing, with the secondary detector, electrons having an electron energy that exceeds the electron energy threshold associated with the electron image;
• wherein the electron energy threshold is different for each electron image in the plurality of electron images;
• receive or generate a mapping between height values and the electron energy thresholds;
• process the multiple electron images to provide hole measurements;
• and
• generate three dimensional measurements of the hole based on the mapping and the hole measurements.