EP-4742465-A2 - ARRANGEMENT FOR SOLID-STATE LASER

EP4742465A2EP 4742465 A2EP4742465 A2EP 4742465A2EP-4742465-A2

Abstract

An arrangement for pumping a gain medium of a solid-state laser to produce laser radiation during production periods separated by dormant periods. The arrangement comprises at least one radiation source and a source driver. The at least one radiation source is configured to provide production radiation of a production wavelength and compensation radiation of a compensation wavelength different from the production wavelength. The source driver is configured to drive the at least one radiation source to provide the production radiation at least during the production periods, wherein the source driver is further configured to drive the at least one radiation source to provide the compensation radiation so as to increase temperature uniformity of the gain medium.

Inventors

REININK, Johan
O'DWYER, David

Assignees

ASML Netherlands B.V.

Dates

Publication Date: 20260513
Application Date: 20260206

Claims (15)

An arrangement for producing laser radiation in a gain medium of a solid-state laser during production periods separated by dormant periods, the arrangement comprising: at least one radiation source configured to provide production radiation of a production wavelength to the gain medium and to provide compensation radiation of a compensation wavelength different from the production wavelength to the gain medium, the production radiation being provided to produce the laser radiation; and a source driver configured to drive the at least one radiation source to provide the production radiation at least during the production periods, wherein the source driver is further configured to drive the at least one radiation source to provide the compensation radiation so as to increase temperature uniformity of the gain medium.
The arrangement of claim 1, wherein the source driver is configured to drive the at least one radiation source to provide the compensation radiation during the dormant periods so as to increase temperature uniformity of the gain medium across the production periods and the dormant periods.
The arrangement of claim 2, wherein the source driver is configured to drive the at least one radiation source such that the temperature distribution in the gain medium remains substantially temporally stable across the production periods and the dormant periods.
The arrangement of any preceding claim, wherein the source driver is configured to drive the at least one radiation source to provide the compensation radiation at a higher power during the dormant periods than during the production periods.
The arrangement of any preceding claim, wherein the source driver is configured to drive the at least one radiation source to provide the production radiation at a higher power during the production periods than during the dormant periods.
The arrangement of any preceding claim, wherein the at least one radiation source comprises: at least one of a production diode and a production photonic-crystal surface-emitting laser (PCSEL) configured to provide the production radiation; and at least one of a compensation diode and a compensation photonic-crystal surface-emitting laser configured to provide the compensation radiation.
The arrangement of any preceding claim, wherein the source driver is configured to drive the at least one radiation source to provide the compensation radiation during the production periods so as to increase temperature uniformity across an active region of the gain medium.
The arrangement of claim 7, wherein the source driver is configured to drive the at least one radiation source to provide the compensation radiation during the production periods such that the temperature distribution across the active region of the gain medium is substantially constant.
The arrangement of claim 7 or 8, wherein the source driver is configured to drive the at least one radiation source during the production periods to provide the production radiation and the compensation radiation such that a gain is substantially uniform across the active region.
The arrangement of any of claims 7 to 9, wherein the source driver is configured to drive the at least one radiation source during the production periods to direct the production radiation to an inner portion of the active region and the compensation radiation to an outer portion of the active region radially outward of the inner portion.
The arrangement of any preceding claim, wherein the at least one radiation source is configured to provide the production radiation substantially coaxially with the compensation radiation.
A solid-state laser comprising: the arrangement of any preceding claim; and the gain medium, wherein the arrangement is configured to provide the production radiation and the compensation radiation to the gain medium.
The solid-state laser of claim 12, wherein the production radiation is closer in wavelength than the compensation radiation to the fundamental lasing wavelength of the gain medium.
A method for producing laser radiation in a gain medium of a solid-state laser during production periods separated by dormant periods, the method comprising: driving at least one radiation source to provide a production radiation of a production wavelength to the gain medium at least during the production periods; producing laser radiation by the provision of the production radiation: and driving the at least one radiation source to provide a compensation radiation of a compensation wavelength different from the production wavelength so as to increase temperature uniformity of the gain medium.
The method of claim 14, wherein the at least one radiation source provides the production radiation substantially coaxially with the compensation radiation.

Description

FIELD The present invention relates to an arrangement, a solid-state laser, a DUV radiation source, and a method for producing laser radiation in a gain medium of a solid-state laser. 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") of a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate (e.g., a wafer). As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as 'Moore's law'. To keep up with Moore's law the semiconductor industry is chasing technologies that enable to create increasingly smaller features. 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 are patterned on the substrate. Typical wavelengths currently in use are 365 nm, 248 nm, 193 nm, and 13.5 nm. A deep ultra-violet (DUV) radiation source, typically an excimer gas-based source such as a KrF (248 nm) laser or an ArF (193 nm) laser, may be used to provide the radiation with the required wavelength for the patterning process. Such excimer lasers are expensive to manufacture and can be inefficient. It is desirable to facilitate the generation of laser radiation at a reduced cost. It is desirable to facilitate more efficient generation of laser radiation, and more particularly DUV radiation. Solid-state lasers are emerging radiation sources providing radiation with suitable wavelengths for lithography applications. Instead of a gaseous medium, the lasing medium of a solid-state laser is a crystal. Solid-state lasers provide reliability, a high quantum efficiency and are relatively simple and easy to maintain. The crystal (or solid-state medium) of the solid-state laser is pumped by a radiation beam (or pump beam). A portion of the energy of the radiation beam, which is absorbed by the crystal, provides a thermal load to the crystal. Hereby, the temperature of the crystal changes, i.e., the temperature of the crystal increases. As a result of the temperature change, the refractive index of the crystal changes. Typically, the radiation beam generates a temperature distribution in the crystal, and hereby a refractive index distribution. The effect that a refractive index distribution takes on a radiation beam is called thermal lensing. This thermally induced lensing effect alters the properties of the optical path in the crystal for the optical radiation beam passing through the crystal. It is desirable to improve on aspects of thermal lensing in solid-state laser crystals, which obviates or mitigates one or more of the problems of the prior art, whether identified herein or elsewhere. SUMMARY According to a first aspect of the present invention, there is provided an arrangement for pumping a gain medium of a solid-state laser to produce laser radiation during production periods separated by dormant periods. The pump arrangement comprises at least one radiation source that is configured to provide production radiation of a production wavelength and compensation radiation of a compensation wavelength different from the production wavelength to the gain medium, and a source driver configured to drive the at least one radiation source to provide the production radiation at least during the production periods, wherein the source driver is further configured to drive the at least one radiation source to provide the compensation radiation so as to increase temperature uniformity of the gain medium during the usage of the solid-state laser. According to a second aspect of the present invention, there is provided a method for pumping a gain medium of a solid-state laser to produce laser radiation during production periods separated by dormant periods. The method comprises driving at least one radiation source to provide a production radiation of a production wavelength to the gain medium at least during the production periods, producing laser radiation by the provision of the production radiation, and driving the at least one radiation source to provide a compensation radiation of a compensation wavelength different from the production wavelength so as to increase temperature uniformity of the gain medium during usage of the solid-state laser. 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 schematically depicts two cross-sectional views of a gain me