Reducing variations in energy reflected from a sample due to thin film interference
AssigneeKLA-Tencor Technologies Corporation
InventorsYung-Ho Chuang, J. Joseph Armstrong
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Abstract
A system and method for inspecting a multi-layer sample, such as a silicon wafer, is disclosed. The design reduces variations in total reflected energy due to thin film interference. The design includes illuminating the sample at two incident angle ranges, where the two incident angle ranges are such that variation in total reflected energy at a first incident angle range may be employed to balance variation in total reflected energy at a second incident angle range. Defects are detected using die-to-die subtraction of the sample illuminated at the two incident angle ranges.
Claims23
A method to reduce variations in total reflected energy due to thin film interference when inspecting a sample, comprising:
- producing p-polarized light based on at least one from a group comprising linear, circular, and random polarized light;
- and
- illuminating the sample at an incident angle similar to Brewster's angle for a top most film, wherein said illuminating uses p-polarized light from said producing;
- wherein the incident angle, polarization of the p-polarized light, and illumination wavelength of the p-polarized light are configured to be selectively altered based on thin film interference encountered on the sample.
A method to reduce variations in total reflected energy due to thin film interference when inspecting a sample, comprising:
- illuminating the sample using ring illumination provided using two light energies of different polarizations produced using at least one segmented waveplate, providing variation in total reflected energy at a first incident angle range to balance variation in total reflected energy at a second incident angle range;
- and further comprising transmitting light energy having a first polarization at the first incident angle range and light energy having a second polarization at the second incident angle range.
A method for inspecting a sample, comprising:
- producing p-polarized light based on at least one from a group comprising linear, circular, and random polarized light;
- illuminating the sample at an incident angle, wherein said illuminating uses p-polarized light from said producing, and
- additionally illuminating the sample at a second incident angle, wherein further illumination at said second incident angle differs in wavelength from illumination at the incident angle;
- wherein the first incident angle, second incident angle, polarization of the p-polarized light, and illumination wavelength of the p-polarized light are configured to be selectively altered based on thin film interference encountered on the sample.
Dependencies are inferred from the claim text.