Abstract: Methods and systems for performing measurements of semiconductor structures based on high-brightness, polychromatic, reflective small angle x-ray scatterometry (RSAXS) metrology are presented herein. RSAXS measurements are performed over a range of wavelengths, angles of incidence, and azimuth angles with small illumination beam spot size, simultaneously or sequentially. In some embodiments, RSAXS measurements are performed with x-ray radiation in the soft x-ray (SXR) region at grazing angles of incidence in the range of 5-20 degrees. In some embodiments, the x-ray illumination source size is 10 micrometers or less, and focusing optics project the source area onto a wafer with a demagnification factor of 0.2 or less, enabling an incident x-ray illumination spot size of less than two micrometers.

Abstract: Optical elements that efficiently propagate x-ray radiation over a desired energy range and reject radiation outside the desired energy range are presented herein. In one aspect, one or more optical elements of an x-ray based system include an integrated optical filter including one or more material layers that absorb radiation having energy outside the desired energy band. In general, the integrated filter improves the optical performance of an x-ray based system by suppressing reflectivity within infrared (IR), visible (vis), ultraviolet (UV), extreme ultraviolet (EUV) portions of the spectrum, or any other undesired wavelength region. In a further aspect, one or more diffusion barrier layers prevent degradation of the integrated optical filter, prevent diffusion between the integrated optical filter and other material layers, or both. In some embodiments, the thickness of one or more material layers of an integrated optical filter vary over the spatial area of the filter.

Abstract: Optical elements that efficiently propagate x-ray radiation over a desired energy range and reject radiation outside the desired energy range are presented herein. In one aspect, one or more optical elements of an x-ray based system include an integrated optical filter including one or more material layers that absorb radiation having energy outside the desired energy band. In general, the integrated filter improves the optical performance of an x-ray based system by suppressing reflectivity within infrared (IR), visible (vis), ultraviolet (UV), extreme ultraviolet (EUV) portions of the spectrum, or any other undesired wavelength region. In a further aspect, one or more diffusion barrier layers prevent degradation of the integrated optical filter, prevent diffusion between the integrated optical filter and other material layers, or both. In some embodiments, the thickness of one or more material layers of an integrated optical filter vary over the spatial area of the filter.

Abstract: Optical elements that efficiently propagate x-ray radiation over a desired energy range and reject radiation outside the desired energy range are presented herein. In one aspect, one or more optical elements of an x-ray based system include an integrated optical filter including one or more material layers that absorb radiation having energy outside the desired energy band. In general, the integrated filter improves the optical performance of an x-ray based system by suppressing reflectivity within infrared (IR), visible (vis), ultraviolet (UV), extreme ultraviolet (EUV) portions of the spectrum, or any other undesired wavelength region. In a further aspect, one or more diffusion barrier layers prevent degradation of the integrated optical filter, prevent diffusion between the integrated optical filter and other material layers, or both. In some embodiments, the thickness of one or more material layers of an integrated optical filter vary over the spatial area of the filter.

Abstract: Methods and systems for positioning a specimen and characterizing an x-ray beam incident onto the specimen in a Transmission, Small-Angle X-ray Scatterometry (T-SAXS) metrology system are described herein. A specimen positioning system locates a wafer vertically and actively positions the wafer in six degrees of freedom with respect to the x-ray illumination beam without attenuating the transmitted radiation. In some embodiments, a cylindrically shaped occlusion element is scanned across the illumination beam while the detected intensity of the transmitted flux is measured to precisely locate the beam center. In some other embodiments, a periodic calibration target is employed to precisely locate the beam center. The periodic calibration target includes one or more spatially defined zones having different periodic structures that diffract X-ray illumination light into distinct, measurable diffraction patterns.

Abstract: Methods and systems for controlling illumination beam spot size for Transmission, Small-Angle X-ray Scatterometry (T-SAXS) measurements of different sized metrology targets are described herein. An X-ray illumination optics subsystem includes one or more focusing optical elements with object and image planes at fixed locations and one or more illumination apertures or slits that independently control magnification and beam divergence. In a further aspect, the illumination source size and shape is controlled, along with magnification and beam divergence. In this manner, beam divergence and illumination spot size on a specimen are independently controlled, while maintaining constant illumination flux.

Abstract: Multilayer targets enabling fast and accurate, absolute calibration and alignment of X-ray based measurement systems are described herein. The multilayer calibration targets have very high diffraction efficiency and are manufactured using fast, low cost production techniques. Each target includes a multilayer structure built up with pairs of X-ray transparent and X-ray absorbing materials. The layers of the multilayer target structure is oriented parallel to an incident X-ray beam. Measured diffraction patterns indicate misalignment in position and orientation between the incident X-Ray beam and the multilayer target. In another aspect, a composite multilayer target includes at least two multilayer structures arranged adjacent one another along a direction aligned with the incident X-ray beam, adjacent one another along a direction perpendicular to the incident X-ray beam, or a combination thereof. In some embodiments, the multilayer structures are spatially separated from one another by a gap distance.

Abstract: Methods and systems for calibrating the location of x-ray beam incidence onto a specimen in an x-ray scatterometry metrology system are described herein. The precise location of incidence of the illumination beam on the surface of the wafer is determined based on occlusion of the illumination beam by two or more occlusion elements. The center of the illumination beam is determined based on measured values of transmitted flux and a model of the interaction of the beam with each occlusion element. The position of the axis of rotation orienting a wafer over a range of angles of incidence is adjusted to align with the surface of wafer and intersect the illumination beam at the measurement location. A precise offset value between the normal angle of incidence of the illumination beam relative to the wafer surface and the zero angle of incidence as measured by the specimen positioning system is determined.

Abstract: Multilayer targets enabling fast and accurate, absolute calibration and alignment of X-ray based measurement systems are described herein. The multilayer calibration targets have very high diffraction efficiency and are manufactured using fast, low cost production techniques. Each target includes a multilayer structure built up with pairs of X-ray transparent and X-ray absorbing materials. The layers of the multilayer target structure is oriented parallel to an incident X-ray beam. Measured diffraction patterns indicate misalignment in position and orientation between the incident X-Ray beam and the multilayer target. In another aspect, a composite multilayer target includes at least two multilayer structures arranged adjacent one another along a direction aligned with the incident X-ray beam, adjacent one another along a direction perpendicular to the incident X-ray beam, or a combination thereof. In some embodiments, the multilayer structures are spatially separated from one another by a gap distance.

Abstract: Methods and systems for reducing the effect of finite source size on illumination beam spot size for Transmission, Small-Angle X-ray Scatterometry (T-SAXS) measurements are described herein. A beam shaping slit having a slender profile is located in close proximity to the specimen under measurement and does not interfere with wafer stage components over the full range of angles of beam incidence. In one embodiment, four independently actuated beam shaping slits are employed to effectively block a portion of an incoming x-ray beam and generate an output beam having a box shaped illumination cross-section. In one aspect, each of the beam shaping slits is located at a different distance from the specimen in a direction aligned with the beam axis. In another aspect, the beam shaping slits are configured to rotate about the beam axis in coordination with the orientation of the specimen.

Abstract: Methods and systems for performing measurements of semiconductor structures based on high-brightness, polychromatic, reflective small angle x-ray scatterometry (RSAXS) metrology are presented herein. RSAXS measurements are performed over a range of wavelengths, angles of incidence, and azimuth angles with small illumination beam spot size, simultaneously or sequentially. In some embodiments, RSAXS measurements are performed with x-ray radiation in the soft x-ray (SXR) region at grazing angles of incidence in the range of 5-20 degrees. In some embodiments, the x-ray illumination source size is 10 micrometers or less, and focusing optics project the source area onto a wafer with a demagnification factor of 0.2 or less, enabling an incident x-ray illumination spot size of less than two micrometers.

Abstract: Methods and systems for positioning a specimen and characterizing an x-ray beam incident onto the specimen in a Transmission, Small-Angle X-ray Scatterometry (T-SAXS) metrology system are described herein. A specimen positioning system locates a wafer vertically and actively positions the wafer in six degrees of freedom with respect to the x-ray illumination beam without attenuating the transmitted radiation. In some embodiments, a cylindrically shaped occlusion element is scanned across the illumination beam while the detected intensity of the transmitted flux is measured to precisely locate the beam center. In some other embodiments, a periodic calibration target is employed to precisely locate the beam center. The periodic calibration target includes one or more spatially defined zones having different periodic structures that diffract X-ray illumination light into distinct, measurable diffraction patterns.

Abstract: Methods and systems for controlling illumination beam spot size for Transmission, Small-Angle X-ray Scatterometry (T-SAXS) measurements of different sized metrology targets are described herein. An X-ray illumination optics subsystem includes one or more focusing optical elements with object and image planes at fixed locations and one or more illumination apertures or slits that independently control magnification and beam divergence. In a further aspect, the illumination source size and shape is controlled, along with magnification and beam divergence. In this manner, beam divergence and illumination spot size on a specimen are independently controlled, while maintaining constant illumination flux.

Abstract: Methods and systems for calibrating the location of x-ray beam incidence onto a specimen in an x-ray scatterometry metrology system are described herein. The precise location of incidence of the illumination beam on the surface of the wafer is determined based on occlusion of the illumination beam by two or more occlusion elements. The center of the illumination beam is determined based on measured values of transmitted flux and a model of the interaction of the beam with each occlusion element. The position of the axis of rotation orienting a wafer over a range of angles of incidence is adjusted to align with the surface of wafer and intersect the illumination beam at the measurement location. A precise offset value between the normal angle of incidence of the illumination beam relative to the wafer surface and the zero angle of incidence as measured by the specimen positioning system is determined.

Abstract: Methods and systems for reducing the effect of finite source size on illumination beam spot size for Transmission, Small-Angle X-ray Scatterometry (T-SAXS) measurements are described herein. A beam shaping slit having a slender profile is located in close proximity to the specimen under measurement and does not interfere with wafer stage components over the full range of angles of beam incidence. In one embodiment, four independently actuated beam shaping slits are employed to effectively block a portion of an incoming x-ray beam and generate an output beam having a box shaped illumination cross-section. In one aspect, each of the beam shaping slits is located at a different distance from the specimen in a direction aligned with the beam axis. In another aspect, the beam shaping slits are configured to rotate about the beam axis in coordination with the orientation of the specimen.