Abstract: An overlay metrology tool may include an illumination source to generate a first illumination beam distribution with a first linear polarization and a second illumination beam distribution with a second linear polarization orthogonal to the first linear polarization, an illumination sub-system to sequentially illuminate two or more cell pairs of an overlay target on a sample having orthogonally oriented grating-over-grating structures, a collection sub-system with two collection channels to capture collected light from an illuminated cell pair and filtering optics to direct light from different cells in an illuminated cell pair to different collection channels for detection. The tool may further include a controller to generate separate overlay measurements for orthogonally-oriented grating-over-grating structures in the two or more cell pairs.

Abstract: A multipole illumination system may include an illumination source to generate a source beam, one or more acousto-optic deflectors to diffract the source beam along at least two directions; one or more collection lenses to collect at least some of the diffracted light from the one or more acousto-optic deflectors, and a controller to generate one or more drive signals for the one or more acousto-optic deflectors. For example, the one or more drive signals may cause the one or more acousto-optic deflectors to generate a symmetric distribution of two or more illumination beams formed from light diffracted from the one or more acousto-optic deflectors and collected by the one or more collection lenses, where a distribution of wavelength and intensity of the two or more illumination beams is symmetric in a plane formed by the first and second directions.

Abstract: A beamsplitter includes a substrate formed from a material transparent to wavelengths of light at least above a selected cutoff wavelength and reflective structures distributed across a surface of the substrate. The reflective structures split incident light having wavelengths above the selected cutoff wavelength into a reflected beam formed from portions of the incident light reflected from the reflective structures and a transmitted beam formed from portions of the incident light transmitted through the substrate. A splitting ratio of a power of the reflected beam to a power of the transmitted beam is based on a ratio of surface area of the reflective surfaces to an area of the incident light on the substrate. Separation distances between neighboring reflective structures are smaller than the cutoff wavelength such that diffracted power of the incident light having wavelengths above the selected cutoff wavelength is maintained below a selected tolerance.

Abstract: A multipole illumination system may include an illumination source to generate a source beam, one or more acousto-optic deflectors to diffract the source beam along at least two directions; one or more collection lenses to collect at least some of the diffracted light from the one or more acousto-optic deflectors, and a controller to generate one or more drive signals for the one or more acousto-optic deflectors. For example, the one or more drive signals may cause the one or more acousto-optic deflectors to generate a symmetric distribution of two or more illumination beams formed from light diffracted from the one or more acousto-optic deflectors and collected by the one or more collection lenses, where a distribution of wavelength and intensity of the two or more illumination beams is symmetric in a plane formed by the first and second directions.

Abstract: A beamsplitter includes a substrate formed from a material transparent to wavelengths of light at least above a selected cutoff wavelength and reflective structures distributed across a surface of the substrate. The reflective structures split incident light having wavelengths above the selected cutoff wavelength into a reflected beam formed from portions of the incident light reflected from the reflective structures and a transmitted beam formed from portions of the incident light transmitted through the substrate. A splitting ratio of a power of the reflected beam to a power of the transmitted beam is based on a ratio of surface area of the reflective surfaces to an area of the incident light on the substrate. Separation distances between neighboring reflective structures are smaller than the cutoff wavelength such that diffracted power of the incident light having wavelengths above the selected cutoff wavelength is maintained below a selected tolerance.