Abstract:
In scatterometry, a merit function including a regularization parameter is used in an iterative process to find values for the scattering properties of the measured target. An optimal value for the regularization parameter is obtained for each measurement target and in each iteration of the iterative process. Various methods can be used to find the value for the regularization parameter, including the Discrepancy Principle, the chi-squared method and novel modifications of the Discrepancy Principle and the chi-squared method including a merit function.
Abstract:
An apparatus for determining a characteristic of a feature of an object comprises: a measurement radiation source; a measurement radiation delivery system; a measurement system; a pump radiation source; and a pump radiation delivery system. The measurement radiation source is operable to produce measurement radiation and the measurement radiation delivery system is operable to irradiate at least a part of a top surface of the object with the measurement radiation. The measurement system is operable to receive at least a portion of the measurement radiation scattered from the top surface and is further operable to determine a characteristic of the feature of the object from at least a portion of the measurement radiation scattered from the top surface. The pump radiation source is operable to produce pump radiation and the pump radiation delivery system is operable to irradiate at least a part of the top surface of the object with the pump radiation so as to produce a mechanical response (for example an acoustic wave) in the object.