EP-4738007-A1 - METROLOGY METHOD AND ASSOCIATED METROLOGY DEVICE

Abstract

Disclosed is a method of metrology comprising: obtaining measurement data relating to scattered radiation, having been scattered by a structure of interest and captured on at least one detector; determining at least a magnitude of a derivative of the phase of at least one component of said scattered radiation from said intensity; and determining at least one parameter of interest of said structure of interest from said at least the magnitude of the derivative of the phase.

Inventors

• TINNEMANS, PATRICIUS, ALOYSIUS, JACOBUS
• VAN PUTTEN, Eibert, Gerjan
• COENE, Willem, Marie, Julia, Marcel
• El GAWHARY, Omar
• NIENHUYS, HAN-KWANG
• PORTER, Christina, Lynn

Assignees

• ASML Netherlands B.V.

Dates

Publication Date

20260506

Application Date

20241104

Claims (15)

1. A method of metrology comprising: obtaining measurement data relating to scattered radiation, having been scattered by a structure of interest and captured on at least one detector; determining at least a magnitude of a derivative of the phase of at least one component of said scattered radiation from said intensity; and determining at least one parameter of interest of said structure of interest from said at least the magnitude of the derivative of the phase.
2. A metrology method as claimed in claim 1, comprising using a Kramers-Kronig based algorithm to retrieve said at least the magnitude of the derivative of the phase of at least one component.
3. A metrology method as claimed in claim 1 or 2, wherein said determining at least the magnitude of the derivative of the phase of at least one component comprises determining a Hilbert transform of a derivative of an intensity of the at least one component or a derivative of the Hilbert transform of the intensity of the at least one component.
4. A metrology method as claimed in claim 3, comprising determining the phase of said at least one component from said at least the magnitude of the derivative of the phase by solving a weighted variant and/or discrete version of Poisson's equation.
5. A metrology method as claimed in any preceding claim, comprising determining the phase in two-dimensions from a retrieval equation for said at least the magnitude of the derivative of the phase, solved for two shear directions.
6. A metrology method as claimed in any preceding claim, wherein said determining step comprises determining the magnitude of the derivative of the phase.
7. A metrology method as claimed in claim 6, further comprising the additional step of determining the sign of said derivative of the phase.
8. A metrology method as claimed in any of claims 1 to 5, wherein said determining step comprises directly determining the derivative of the phase from said intensity.
9. A metrology method as claimed in any preceding claim, wherein said obtaining said metrology data comprises: illuminating the periodic structure with said illumination; and capturing said scattered radiation from said periodic structure as a result of said illuminating at a detection plane. comprising performing a measurement to obtain said measurement data.
10. A metrology method as claimed in any preceding claim, wherein each said one or more non-zero diffraction orders comprises a plurality of diffraction orders, each said diffraction order comprising a plurality of sub-component, each sub-component relating to a different wavelength.
11. A metrology method as claimed in claim 10, comprising an initial step of removing a source spectrum from said measurement data to obtain diffraction efficiency data.
12. A metrology method as claimed in claim 11, comprising converting, per diffraction order, said diffraction efficiency data into an intensity signal data which is a quantity which is a function of wavelength and the wave vector of an incident beam, which is incident on said structure of interest to generate said scattered radiation; and transforming said diffraction efficiency data to obtain said at least the magnitude of the derivative of the phase .
13. A metrology method as claimed in any preceding claim, wherein said scattered radiation comprises broadband radiation.
14. A metrology method as claimed in claim 13, wherein said broadband radiation comprises radiation generated via high harmonic generation.
15. A metrology apparatus being operable to perform the method of any of claims 1 to 14.

Description

FIELD The present invention relates to a metrology method and device which may, for example, be used for determining a characteristic of structures on a substrate. BACKGROUND A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (also often referred to as "design layout" or "design") at a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate (e.g., a wafer). To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which can be formed on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm and 13.5 nm. A lithographic apparatus, which uses extreme ultraviolet (EUV) radiation, having a wavelength within the range 4-20 nm, for example 6.7 nm or 13.5 nm, may be used to form smaller features on a substrate than a lithographic apparatus which uses, for example, radiation with a wavelength of 193 nm. Low-k1 lithography may be used to process features with dimensions smaller than the classical resolution limit of a lithographic apparatus. In such process, the resolution formula may be expressed as CD = k1×λ/NA, where λ is the wavelength of radiation employed, NA is the numerical aperture of the projection optics in the lithographic apparatus, CD is the "critical dimension" (generally the smallest feature size printed, but in this case half-pitch) and k1 is an empirical resolution factor. In general, the smaller k1 the more difficult it becomes to reproduce the pattern on the substrate that resembles the shape and dimensions planned by a circuit designer in order to achieve particular electrical functionality and performance. To overcome these difficulties, sophisticated fine-tuning steps may be applied to the lithographic projection apparatus and/or design layout. These include, for example, but not limited to, optimization of NA, customized illumination schemes, use of phase shifting patterning devices, various optimization of the design layout such as optical proximity correction (OPC, sometimes also referred to as "optical and process correction") in the design layout, or other methods generally defined as "resolution enhancement techniques" (RET). Alternatively, tight control loops for controlling a stability of the lithographic apparatus may be used to improve reproduction of the pattern at low k1. In lithographic processes, it is desirable to make frequently measurements of the structures created, e.g., for process control and verification. Various tools for making such measurements are known, including scanning electron microscopes or various forms of metrology apparatuses, such as scatterometers. A general term to refer to such tools may be metrology apparatuses or inspection apparatuses. In many metrology applications, it is desirable to access the full electric field (i.e., intensity and phase) rather than only intensity. Holography tools enable this, however they require a reference beam and very stringent operation to ensure interference between the reference beam and measurement radiation beam. Other phase retrieval methods may comprise an iterative retrieval of phase, however these are computationally demanding, It would be desirable to improve on present methods for measuring the full electric field in metrology applications. SUMMARY Embodiments of the invention are disclosed in the claims and in the detailed description. In a first aspect of the invention there is provided a method of metrology comprising: obtaining measurement data relating to scattered radiation, having been scattered by a structure of interest and captured on at least one detector; determining at least a magnitude of a derivative of the phase of at least one component of said scattered radiation from said intensity; and determining at least one parameter of interest of said structure of interest from said at least the magnitude of the derivative of the phase. These and other aspects and advantages of the apparatus and methods disclosed herein will be appreciated from a consideration of the following description and drawings of exemplary embodiments. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: Figure 1 depicts a schematic overview of a lithographic apparatus;Figure 2 depicts a schematic overview of a lithographic cell;Figure 3 depicts a schematic representation of holistic lithography, representing a cooperation between three key technologies to optimize semiconductor manufacturing;Figure 4 is a schematic illustration of a scatterometry apparatus;Figure 5 comprises (a) a schematic diagram of a dark field