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AssigneeASML Netherlands B.V.
InventorMartijn Constant Van Beurden
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Improved convergence in the volume-integral method (VIM) of calculating electromagnetic scattering properties of a structure is achieved by numerically solving a volume integral equation for a vector field, F, rather than the electric field, E. The vector field, F, may be related to the electric field, E, by a change of basis, and may be continuous at material boundaries where the electric field, E, has discontinuities. Convolutions of the vector field, F, are performed using convolution operators according the finite Laurent rule (that operate according to a finite discrete convolution), which allow for efficient matrix-vector products via 1D and/or 2D FFTs (Fast Fourier Transforms). An invertible convolution-and-change-of-basis operator, C, is configured to transform the vector field, F, to the electric field, E, by performing a change of basis according to material and geometric properties of the periodic structure. After solving the volume integral for the vector field, F, an additional post-processing step may be used to obtain the electric field, E, from the vector field, F. The vector field, F, may be constructed from a combination of field components of the electric field, E, and the electric flux density, D, by using a normal-vector field, n, to filter out continuous components.
A method of calculating electromagnetic scattering properties of a structure, the structure being periodic in at least one direction and including materials of differing properties such as to cause a discontinuity in an electromagnetic field at a material boundary, the method comprising:
A method of reconstructing an approximate structure of an object from a detected electromagnetic scattering property arising from illumination of the object by radiation, the method comprising:
An inspection apparatus for reconstructing an approximate structure of an object, the inspection apparatus comprising:
A tangible computer readable medium having stored thereon computer executable instructions that, if executed by a computer device, cause the computing device to perform a method comprising:
A method of calculating electromagnetic scattering properties of a structure, the structure being periodic in at least one direction and including materials of differing properties such as to cause a discontinuity in an electromagnetic field at a material boundary, the method comprising:
Dependencies are inferred from the claim text.