Patent Document ID: 10146140
Application ID: 15285051
Patent Flag: 1

Claim One:
1. A method for determining changes to a lithographic exposure process used to form a structure on a substrate or expose one or more subsequent substrates, the method comprising: defining a layered structure model to represent the structure on the substrate in a two- or three-dimensional model space, the structure model defining for each layer of the structure a homogeneous background permittivity and for at least one layer a non-homogeneous contrast permittivity; and using the layered structure model in a modal method to simulate interaction of radiation with the structure, a total field being calculated in terms of a background field and a contrast field, the background field within each layer being independent of the non-homogeneous contrast permittivity, wherein the simulated interaction uses Maxwell's equation in a Born approximation, whereby a product of the non-homogeneous contrast permittivity and the total field is approximated by a product of the non-homogeneous contrast permittivity and the background field; comparing the interaction simulated with results of a real interaction observed in a metrology apparatus with the structure to generate comparison results; and storing the comparison results in a memory such that adjustments to exposure of subsequent substrates or reworking of the substrate with the structure can be done using the comparison results to improve yield.