Patent ID: 12198921

DETAILED DESCRIPTION

Reference will now be made in detail to the subject matter disclosed, which is illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with respect to certain embodiments and specific features thereof. The embodiments set forth herein are taken to be illustrative rather than limiting. It should be readily apparent to those of ordinary skill in the art that various changes and modifications in form and detail may be made without departing from the spirit and scope of the disclosure.

Referring generally toFIGS.1A-7, a laser-sustained plasma broadband light source with a tapered window for deflecting light from selected portions of the plasma chamber is described, in accordance with one or more embodiments of the present disclosure.

Embodiments of the present disclosure are directed to an LSP broadband source equipped with one or more tapered windows configured for deflecting broadband light away from one or more portions of the chamber used to generate the plasma source. For example, embodiments of the present disclosure may include a tapered window (e.g., polished tapered conical surface) arranged to deflect broadband light emitted by a plasma away from one or more seals forming a seal between the window and the wall of the chamber.

FIG.3illustrates a simplified schematic view of a LSP broadband light source100with one or more tapered windows, in accordance with one or more embodiments. In embodiments, the light source100includes a gas containment structure102containing one or more gases103. For example, the gas containment structure102may contain one or more high-pressure gases (e.g., 50-300 atm). In embodiments, the light source100includes a tapered window104configured to transmit broadband light through an aperture107within a wall105of the gas containment structure102. In embodiments, the tapered window104includes a tapered section including a tapered surface122. The tapered surface122may be configured to deflect a portion118of light impinging on a peripheral portion of the tapered window104away from the of the gas containment structure102to protect one or more portions123of the gas containment structure102. For example, the tapered window104may be configured to deflect illumination118away from one or more seals123. In embodiments, the tapered window104may transmit some illumination120passing through a central face124of the window104and through the aperture107while avoiding the one or more seals123. In embodiments, the tapered surface122of the tapered window104may internally reflect some illumination121such that illumination121passes through aperture107and avoids one or more seals123. In embodiments, the illumination120,121passed through the aperture107is transmitted to one or more downstream optics111.

The tapered window may be used as an input or output window. While the present disclosure has depicted the window104as an output window, this configuration should not be interpreted as a limitation on the scope of the present disclosure and in other embodiments the window may be used as an input window. For example, window110may be replaced by window104.

In embodiments, the light source100includes a laser pump source106configured to generate an optical pump108. The laser pump source106is configured to direct the optical pump108into the gas containment structure102to sustain a plasma112within the gas containment structure102to generate broadband light116. For example, the laser pump source106and focusing lens109may direct and focus the optical pump108into the gas containment structure102through window110to sustain plasma112.

The laser pump source106may include any laser known in the art of plasma-based broadband light generation. In embodiments, the laser pump source106may include one or more continuous wave (CW) pump lasers and/or one or more pulsed lasers. The laser pump source106may be configured to emit infrared (IR) radiation, near infrared (NIR) radiation, ultraviolet (UV) radiation, visible radiation, or other radiation suitable to form a plasma when incident on a suitable target material.

In embodiments, the light source100includes one or more collection optics114. For example, the one or more collection optics may include one or more mirrors and/or one or more lenses. For example, as shown inFIG.3, the one or more collection optics114may include a retroflector configured to collect broadband light116from plasma112and redirecting the illumination toward the aperture107and through the tapered window104.

The gas contained within the gas containment structure102an used to generate plasma112may include any gas or mixture of gases suitable for used in broadband generation via laser-sustained plasma sources. For example, the one or more gases may include, but are not limited to, Ar, Xe, Kr, Ne, or He or a mixture of two or more of Ar, Xe, Kr, Ne, or He.

The broadband source100may be configured to emit broadband light in one or more of the spectral ranges including UV light, VUV light, and/or DUV light.

FIG.4Aillustrates a cross-sectional view of the tapered window104, in accordance with one or more embodiments of the present disclosure. The broadband light116may impinge the tapered window104. A central portion120of the illumination116may pass through the front face124of the tapered window104and pass through the aperture107of wall105without impinging on the one or more seals123. A peripheral portion of the illumination116may impinge the tapered surface122of the tapered window104. A first portion118of the light impinging on the tapered surface122may be deflected away from the tapered window104and away from the one or more seals123. A second portion121of the light impinging on the tapered surface121may be internally reflected through the bulk of the tapered window104and through the aperture107of the wall105while avoiding the one or more seals123.

In embodiments, the tapered surface122of the tapered window104may be polished to reflect a portion119of broadband light impinging on the peripheral portion of the window104away from the aperture107in the wall105of the gas containment structure102to protect one or more portions of the gas containment structure102. In embodiments, the tapered surface122includes a ground tapered surface configured to scatter a portion119of light impinging on the peripheral portion of the window124away from the aperture107in the wall105of the gas containment structure102to protect one or more portions of the gas containment structure102.

The tapered window104may be formed from any optical material known in the art suitable for operating in high-pressure VUV light sources. For example, the tapered window104may be formed from, but is not limited to, MgF2, CaF2, LiF, sapphire, quartz, and the like.

FIG.4Billustrates a simplified schematic view of the tapered window104, in accordance with one or more embodiments of the present disclosure. The tapered window104may be formed as a monolithic structure having a tapered cylindrical shape. For example, the tapered window104may include a cylindrical body126, the tapered surface122, and the face124. In embodiments, the tapered surface122includes a conical surface. The conical surface may include one or more conical sections. It is noted that the scope of the present disclosure is not limited to the conical structure depicted inFIG.4Bwhich is provided merely for illustrative purposes.

FIGS.5A-5Billustrate simplified schematic view of the the tapered window104with a convex lensing surface, in accordance with one or more embodiments of the present disclosure. In embodiments, the convex lensing surface130may be formed at the center portion of the tapered window104. For example, as shown inFIG.5A, the convex lensing surface130may be configured to collimate light impinging on the convex lensing surface130of the tapered window104. By way of another example, as shown inFIG.5B, the convex lensing surface130may be configured to focus light impinging on the convex lensing surface130of the tapered window104. The convex lensing surface130may include, but is not limited to, a spherical lensing surface. The surface of the tapered window104may be modified to condition the broadband light in a desired manner. For example, the tapered window104may include a lensing surface or a filtering surface.

FIG.6illustrates a simplified schematic view of an optical characterization system600incorporating the compact LSP broadband light source, in accordance with one or more alternative and/or additional embodiments. In embodiments, system600includes the LSP light source100, an illumination arm603, a collection arm605, a detector assembly614, and a controller618including one or more processors620and memory622.

It is noted herein that system600may comprise any imaging, inspection, metrology, lithography, or other characterization system known in the art. In this regard, system600may be configured to perform inspection, optical metrology, lithography, and/or any form of imaging on a sample607. Sample607may include any sample known in the art including, but not limited to, a wafer, a reticle, a photomask, and the like. It is noted that system600may incorporate one or more of the various embodiments of the LSP light source100described throughout the present disclosure.

In one embodiment, sample607is disposed on a stage assembly612to facilitate movement of sample607. Stage assembly612may include any stage assembly612known in the art including, but not limited to, an X-Y stage, an R-e stage, and the like. In another embodiment, stage assembly612is capable of adjusting the height of sample607during inspection or imaging to maintain focus on sample607.

In one embodiment, the illumination arm603is configured to direct broadband light117from the Broadband LSP light source100to the sample607. The illumination arm603may include any number and type of optical components known in the art. In one embodiment, the illumination arm603includes one or more optical elements602, a beam splitter604, and an objective lens606. In this regard, illumination arm603may be configured to focus broadband light117from the Broadband LSP light source100onto the surface of the sample607. The one or more optical elements602may include any optical element or combination of optical elements known in the art including, but not limited to, one or more mirrors, one or more lenses, one or more polarizers, one or more gratings, one or more filters, one or more beam splitters, and the like. It is noted herein that the collection location may include, but is not limited to, one or more of the optical elements602, a beam splitter604, or an objective lens606.

In one embodiment, system600includes a collection arm605configured to collect light reflected, scattered, diffracted, and/or emitted from sample607. In another embodiment, collection arm605may direct and/or focus the light from the sample607to a sensor616of a detector assembly614. It is noted that sensor616and detector assembly614may include any sensor and detector assembly known in the art. The sensor616may include, but is not limited to, a CCD sensor or a CCD-TDI sensor. Further, sensor616may include, but is not limited to, a line sensor or an electron-bombardment line sensor.

In one embodiment, detector assembly614is communicatively coupled to a controller618including one or more processors620and memory622. For example, the one or more processors620may be communicatively coupled to memory622, wherein the one or more processors620are configured to execute a set of program instructions stored on memory622. In one embodiment, the one or more processors620are configured to analyze the output of detector assembly614. In one embodiment, the set of program instructions are configured to cause the one or more processors620to analyze one or more characteristics of sample607. In another embodiment, the set of program instructions are configured to cause the one or more processors620to modify one or more characteristics of system600in order to maintain focus on the sample607and/or the sensor616. For example, the one or more processors620may be configured to adjust the objective lens606or one or more optical elements602in order to focus broadband light117from broadband LSP light source100onto the surface of the sample607. By way of another example, the one or more processors620may be configured to adjust the objective lens606and/or one or more optical elements610in order to collect illumination from the surface of the sample607and focus the collected illumination on the sensor616.

It is noted that the system600may be configured in any optical configuration known in the art including, but not limited to, a dark-field configuration, a bright-field orientation, and the like. The system600may be configured as any type of metrology tool known in the art such as, but not limited to, a spectroscopic ellipsometer with one or more angles of illumination, a spectroscopic ellipsometer for measuring Mueller matrix elements (e.g., using rotating compensators), a single-wavelength ellipsometer, an angle-resolved ellipsometer (e.g., a beam-profile ellipsometer), a spectroscopic reflectometer, a single-wavelength reflectometer, an angle-resolved reflectometer (e.g., a beam-profile reflectometer), an imaging system, a pupil imaging system, a spectral imaging system, or a scatterometer.

Additional details of various embodiments of optical characterization system600are described in U.S. Published U.S. Pat. No. 7,957,066B2, entitled “Split Field Inspection System Using Small Catadioptric Objectives,” issued on Jun. 7, 2011; U.S. Published Patent Application 2007/0002465, entitled “Beam Delivery System for Laser Dark-Field Illumination in a Catadioptric Optical System,” published on Jan. 4, 2007; U.S. Pat. No. 5,999,310, entitled “Ultra-broadband UV Microscope Imaging System with Wide Range Zoom Capability,” issued on Dec. 7, 1999; U.S. Pat. No. 7,525,649 entitled “Surface Inspection System Using Laser Line Illumination with Two Dimensional Imaging,” issued on Apr. 28, 2009; U.S. Published Patent Application 2013/0114085, entitled “Dynamically Adjustable Semiconductor Metrology System,” by Wang et al. and published on May 9, 2013; U.S. Pat. No. 5,608,526, entitled “Focused Beam Spectroscopic Ellipsometry Method and System, by Piwonka-Corle et al., issued on Mar. 4, 1997; and U.S. Pat. No. 6,297,880, entitled “Apparatus for Analyzing Multi-Layer Thin Film Stacks on Semiconductors,” by Rosencwaig et al., issued on Oct. 2, 2001, which are each incorporated herein by reference in their entirety.

The one or more processors620of the present disclosure may include any one or more processing elements known in the art. In this sense, the one or more processors620may include any microprocessor-type device configured to execute software algorithms and/or instructions. In one embodiment, the one or more processors620may consist of a desktop computer, mainframe computer system, workstation, image computer, parallel processor, or other computer system (e.g., networked computer) configured to execute a program configured to operate the system600and/or Broadband LSP light source100, as described throughout the present disclosure. It should be recognized that the steps described throughout the present disclosure may be carried out by a single computer system or, alternatively, multiple computer systems. In general, the term “processor” may be broadly defined to encompass any device having one or more processing elements, which execute program instructions from a non transitory memory medium622. Moreover, different subsystems of the various systems disclosed may include processor or logic elements suitable for carrying out at least a portion of the steps described throughout the present disclosure. Therefore, the above description should not be interpreted as a limitation on the present disclosure but merely an illustration.

The memory medium622may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors620. For example, the memory medium622may include a non-transitory memory medium. For instance, the memory medium622may include, but is not limited to, a read-only memory, a random access memory, a magnetic or optical memory device (e.g., disk), a magnetic tape, a solid state drive, and the like. In another embodiment, the memory622is configured to store one or more results and/or outputs of the various steps described herein. It is further noted that memory622may be housed in a common controller housing with the one or more processors620. In an alternative embodiment, the memory622may be located remotely with respect to the physical location of the processors620. For instance, the one or more processors620may access a remote memory (e.g., server), accessible through a network (e.g., internet, intranet, and the like). In another embodiment, memory medium622maintains program instructions for causing the one or more processors620to carry out the various steps described through the present disclosure.

FIG.7illustrates a process flow diagram depicting a method700generating VUV light with an LSP broadband light source with a taped window, in accordance with one or more alternative and/or additional embodiments. It is noted herein that the steps of method700may be implemented all or in part by broadband LSP light source100. It is further recognized, however, that the method700is not limited to the broadband LSP light source100in that additional or alternative system-level embodiments may carry out all or part of the steps of method700.

In step702, method700includes containing a gas within a gas containment structure. In step704, method700includes generating an optical pump and directing the optical pump within the gas containment structure to sustain a plasma within the gas containment structure to generate broadband light. In step706, method700includes deflecting a portion of broadband light impinging on a peripheral portion of a window away from an aperture within the wall of the gas containment structure to protect one or more portions of the gas containment structure. In step708, the method includes transmitting broadband light impinging on a center portion of the window through the aperture within the wall of the gas containment structure via the center portion of window.

One skilled in the art will recognize that the herein described components, operations, devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken as limiting.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations are not expressly set forth herein for sake of clarity.

The herein described subject matter sometimes illustrates different components contained within, or connected with, other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “connected,” or “coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “couplable,” to each other to achieve the desired functionality. Specific examples of couplable include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components.

Furthermore, it is to be understood that the invention is defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” and the like). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, and the like” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, and the like). In those instances where a convention analogous to “at least one of A, B, or C, and the like” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, and the like). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”

It is believed that the present disclosure and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction, and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely explanatory, and it is the intention of the following claims to encompass and include such changes. Furthermore, it is to be understood that the invention is defined by the appended claims.