CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national phase entry of PCT Patent Application No. PCT/EP2018/076639, which was filed on Oct. 1, 2018, which claims the benefit of priority of European Patent Application No. 17198202.8 which was filed on Oct. 25, 2017 and which is incorporated herein in its entirety by reference.

BACKGROUND

Field of the Invention

The present invention relates to an inspection tool, a lithographic apparatus, an electron beam source and an inspection method.

Description of the Related Art

A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g. including part of, one, or several dies) on a substrate (e.g. a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. Conventional lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

The radiation beam as typically applied in lithographic apparatuses may e.g. be a DUV radiation beam (e.g. having a wavelength of 248 nm or 193 nm) or an EUV radiation beam (e.g. having a wavelength of 11 nm or 13.5 nm).

The manufacturing of an integrated circuit may typically require the stacking of a plurality of layers, whereby the layers need to be accurately aligned. Without such an alignment, a required connection between layers may be flawed, resulting in a malfunctioning of the integrated circuit.

Typically, the bottom layer or layers of the integrated circuit will contain the smallest structures, such as transistors or components thereof. The structures of subsequent layers are typically larger and enable connections of the structures in the bottom layers to the outside world. In view of this, an alignment of two layers will be the most challenging in the bottom portion of the integrated circuit.

In order to ensure that a circuit or a circuit layer is properly patterned, substrates are often subjected to inspection, using inspection tools such as e-beam inspection tools.

An example of such an inspection tool is a high resolution SEM (scanning electron microscope), which is e.g. used to examine dimensions of patterns on a substrate. Such a high resolution SEM typically uses electrons, with an energy between 200 eV and 30 keV, which are accelerated towards the surface of the substrate, where they diffuse into and generate new electrons (i.e. secondary electrons). Due to this, secondary and/or backscattered electrons are emitted from the surface. These secondary and/or backscattered electrons may then be recorded by a detector. By scanning an area of a substrate using a beam of electrons, information about the surface structure of the substrate can be obtained.

It would be desirable to improve the performance of e-beam inspection tools such as high resolution SEMs as currently available.

SUMMARY

It is desirable to improve the performance of e-beam inspection tools.

According to an embodiment of the present invention, there is provided an inspection method for a substrate, the inspection method comprising:providing an electron beam having a first polarization state to a sample of the semiconductor substrate;detecting a first response signal of the sample caused by interaction of the electron beam having the first polarization state with the sample;providing an electron beam having a second polarization state to the sample of the semiconductor substrate;detecting a second response signal of the sample caused by interaction of the electron beam having the second polarization state with the sample;determining a geometric or material property of the sample, based on the first response signal and the second response signal.

According to an embodiment of the invention, there is provided an inspection tool comprising:an e-beam source configured to generate an e-beam having a first polarization state and an e-beam having a second polarization state;a beam manipulator configured to direct the electron beam having the first polarization state and the e-beam having the second polarization state onto a sample;a detector configured to detect a first response signal of the sample caused by interaction of the electron beam having the first polarization state with the sample and a second response signal of the sample caused by interaction of the electron beam having the second polarization state with the sample;a processing unit configured to determine a geometric or material property of the sample, based on the first response signal and the second response signal.

According to an embodiment of the invention, there is provided an electron beam source comprising:a tip-shaped Schottky emitter configured to emit an electron beam, whereby the tip-shaped Schottky emitter comprises a metallic coating;a magnetic field generator configured to magnetize the metallic coating, thereby in use spin-polarizing the electron beam.

According to an embodiment of the invention, there is provided a lithographic apparatus comprising:an illumination system configured to condition a radiation beam;a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam;a substrate table constructed to hold a substrate; anda projection system configured to project the patterned radiation beam onto a target portion of the substrate,wherein the apparatus further comprises an inspection tool according to the present invention.

