An optical system used in a charged particle beam inspection system. The optical system includes one or more optical lenses, and a compensation lens configured to compensate a drift of a focal length of a combination of the one or more optical lenses from a first medium to a second medium.

A photomask includes a patterned photomask plate and a supporting member. The patterned photomask plate has a pattern region and a peripheral region surrounding the pattern region. The patterned photomask plate includes a plurality of openings in the pattern region. The supporting member directly abuts the patterned photomask plate and is in a peripheral region of the patterned photomask plate. The supporting member is formed from a different material than the patterned photomask plate.

An inspection apparatus for adjusting a working height for a substrate for multiple target heights is disclosed. The inspection apparatus includes a radiation source configured to provide a radiation beam and a beam splitter configured to split the radiation beam into multiple beamlets that each reflect off a substrate. Each beamlet contains light of multiple wavelengths. The inspection apparatus includes multiple light reflecting components, wherein each light reflecting component is associated with one of the beamlets reflecting off the substrate and is configured to support a different target height for the substrate by detecting a height or a levelness of the substrate based on the beamlet reflecting off the substrate.

A method includes: receiving a photomask; patterning a wafer by directing a first radiation beam to the wafer through the photomask at a first tilt angle; and inspecting the photomask. The inspecting includes: directing a second radiation beam to the photomask at a second tilt angle greater than the first tilt angle; receiving a third radiation beam reflected from the photomask; and generating an image of the photomask according to the third radiation beam.

A method includes: receiving a photomask; patterning a wafer by directing a first radiation beam to the wafer through the photomask at a first tilt angle; and inspecting the photomask. The inspecting includes: directing a second radiation beam to the photomask at a second tilt angle greater than the first tilt angle; receiving a third radiation beam reflected from the photomask; and generating an image of the photomask according to the third radiation beam.

A system for switching between an optical pellicle and an EUV pellicle includes one or more inspection tools configured to perform one or more inspection processes on a mask. The system includes one or more extreme ultraviolet (EUV) lithography tools configured to perform one or more lithographic exposures on the mask. The system includes a dual pellicle handler operatively coupled to the one or more inspection tools and the one or more EUV lithography tools, wherein the dual pellicle handler is configured to attach at least one of an optical pellicle or an EUV pellicle to the mask, wherein the dual pellicle handler is configured to detach at least one of the optical pellicle or the EUV pellicle from the mask.

A system for switching between an optical pellicle and an EUV pellicle includes one or more inspection tools configured to perform one or more inspection processes on a mask. The system includes one or more extreme ultraviolet (EUV) lithography tools configured to perform one or more lithographic exposures on the mask. The system includes a dual pellicle handler operatively coupled to the one or more inspection tools and the one or more EUV lithography tools, wherein the dual pellicle handler is configured to attach at least one of an optical pellicle or an EUV pellicle to the mask, wherein the dual pellicle handler is configured to detach at least one of the optical pellicle or the EUV pellicle from the mask.

Disclosed is an object table for holding an object, comprising: an electrostatic clamp arranged to clamp the object on the object table; a neutralizer arranged to neutralize a residual charge of the electrostatic clamp; a control unit arranged to control the neutralizer, wherein the residual charge is an electrostatic charge present on the electrostatic clamp when no voltage is applied to the electrostatic clamp.

Disclosed is a method of, and associated apparatus for, determining an edge position relating to an edge of a feature comprised within an image, such as a scanning electron microscope image, which comprises noise. The method comprises determining a reference signal from said image; and determining said edge position with respect to said reference signal. The reference signal may be determined from the image by applying a 1-dimensional low-pass filter to the image in a direction parallel to an initial contour estimating the edge position.

Disclosed is a method of, and associated apparatus for, determining an edge position relating to an edge of a feature comprised within an image, such as a scanning electron microscope image, which comprises noise. The method comprises determining a reference signal from said image; and determining said edge position with respect to said reference signal. The reference signal may be determined from the image by applying a 1-dimensional low-pass filter to the image in a direction parallel to an initial contour estimating the edge position.