Metrology and Scatterometry with Collimated Illumination
Development of novel lithography techniques such as nanoimprint lithography and the possibility of creating periodic and quasi-periodic structures (such as gratings and metasurfaces) with complex shapes and geometries has led to a need for rethinking our conventional metrology tools for non-destructive and rapid quality inspection of the fabricated structures. These tools not only must be able to measure the optical performance of these structures, but also provide geometrical information about the fabricated structures.
TeraNova's technology based on Fourier microscopy with collimated illumination enables us to extract critical information such as optical performances of fabricated structures and quantifies the quality of the samples during the fabrication process. In addition, using our elaborated algorithms we are able to extract variations in the geometrical parameters of the samples and refractive indices of the materials used during the processing.
• Compact table top instrument
• Inspection area of approximately 100 micrometer diameter
• Simultaneous detection of several diffraction orders
By scanning the angle of incident on the surface of a sample, we determine intensity of diffracted orders at each incident angle and for a given polarization (TE or TM). An illustrative example of such a measurement for a grating is shown in figure above. The acceptance angle is set by the numerical aperture (NA) of the objective lens.
Minor modifications in samples such as geometrical changes, refractive index variations or inhomogeneities in the substrate will affect the measured curved significantly.
In figure below, two identical samples (1D gratings, 380 nm pitch size) are baked at 90°C and 300 °C. Metrology measurements (Intensity of zeroth-order diffraction) in combination with simulations are used for extracting geometrical parameters and refractive indices.