A method for producing a protective buffer flow in an EUV light source and an EUV mask inspection apparatus are provided. The method includes directing light along a light path from the EUV light source toward a collector. A first buffer gas from a buffer gas injector is injected through a plurality of through holes in the collector. The first buffer gas is directed away from a surface of the collector. A second buffer gas is injected from a ring manifold arranged peripherally to the collector and arranged a first distance toward the light path in relation to the collector. The second buffer gas is directed away from the surface of the collector. The first distance corresponds to a distance from the collector where the first buffer gas merges into a single flow.

An extreme ultraviolet light generation system may include a chamber, a first partition wall having at least one opening which provides communication between a first space and a second space, an EUV light concentrating mirror located in the second space and configured to concentrate extreme ultraviolet light generated in a plasma generation region located in the first space, a first gas supply port formed at the chamber, and a gas exhaust port formed in the first partition wall, a distance between the center of the plasma generation region and an edge of the at least one opening being equal to or more than a stop distance L.sub.STOP [mm] calculated by the following equation:
L.sub.STOP=272.8.Math.E.sub.AVG.sup.0.4522.Math.P.sup.−1 E.sub.AVG [eV] representing average kinetic energy of ions generated in the plasma generation region and P [Pa] representing a gas pressure inside the first partition wall.

An extreme ultraviolet light generation system may include a laser device configured to emit pulse laser light, an EUV light concentrating mirror configured to reflect and concentrate extreme ultraviolet light generated by irradiating a target with the pulse laser light, and a processor configured to receive a first energy parameter of the extreme ultraviolet light and control an irradiation frequency of the pulse laser light with which the target is irradiated so that change in a second energy parameter related to energy per unit time of the extreme ultraviolet light reflected by the EUV light concentrating mirror is suppressed.

A method for determining a deformation of a resist in a patterning process. The method involves obtaining a resist deformation model of a resist having a pattern, the resist deformation model configured to simulate a fluid flow of the resist due to capillary forces acting on a contour of at least one feature of the pattern; and determining, via the resist deformation model, a deformation of a resist pattern to be developed based on an input pattern to the resist deformation model.

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 computer program product causes a processor to execute a process of causing an optical system to illuminate at least one structure on a substrate that comprises first repetitive features at a first pitch in a first layer and second repetitive features at a second pitch in a second layer, the first repetitive features at least partially overlapping with the second repetitive features. The first pitch is different from the second pitch. The processor causes the optical system to receive radiation scattered by the at least one structure and transmit a portion of the received scattered radiation to a sensor arranged in an image plane of the optical system or in a plane conjugate with the image plane for detecting the received scattered radiation and configured to detect a characteristic of radiation impinging on the sensor. The processor then determines a characteristic of interest of the structure.

Disclosed herein is a method for increasing signal-to-noise (SNR) in optical imaging of defects on unpatterned wafers. The method includes: (i) irradiating a region of an unpatterned wafer with a substantially polarized, incident light beam, and (ii) employing relay optics to collect and guide, radiation scattered off the region, onto a segmented polarizer comprising at least four polarizer segments characterized by respective dimensions and polarization directions. The respective dimensions and polarization direction of each of the at least four polarizer segments are such that an overall power of background noise radiation, generated in the scattering of the incident light beam from the region and passed through all of the at least four polarizer segments, is decreased as compared to utilizing a linear polarizer.

A photoresist with a detection additive is utilized to help increase the contrast of images during an after development inspection process. The detection additive fluoresces during the after development inspection process and adds to the energy that is reflected during the after development inspection process, increasing the contrast during the after development inspection process and helping to identify defects that are not otherwise detectable.

Embodiments of the present disclosure provide a substrate measuring device in a lithography projection apparatus that provides multiple light sources having different wavelengths. In some embodiments, a lithography projection apparatus includes a substrate measuring system disposed proximate to a substrate stage, the substrate measuring system further including an emitter including multiple light sources configured to provide multiple beams of light, each of at least some of the multiple beams of light having a different wavelength, at least one optical fiber, wherein each of respective portions of the at least one optical fiber is configured to pass a respective one of the multiple beams of light, and a receiver positioned to collected light emitted from the emitter and reflected off of a substrate disposed on the substrate stage.

According to one embodiment, a prism system is provided. The prism system includes a polarizing beam splitter (PBS) surface. The PBS surface is configured to generate first and second sub-beams having corresponding first and second polarization information from a received beam, the second polarization information being different than the first polarization information. A first optical path of the first sub-beam within the prism system has substantially same length as a second optical path of the second sub-beam within the prism system. Additionally or alternatively, the first sub-beam achieves a predetermined polarization extinction ratio.