Laser-sustained plasma light source with reverse vortex flow

A laser-sustained plasma (LSP) light source with reverse vortex flow is disclosed. The LSP source includes gas cell including a gas containment structure including a body, neck, and shaft. The gas cell includes one or more gas delivery lines for delivery gas to one or more nozzles positioned in or below the neck of the gas containment structure. The gas cell includes one or more gas inlets and one or more gas outlets arranged to generate a reverse vortex flow within the gas containment structure of the gas cell. The LSP source also includes a laser pump source configured to generate an optical pump to sustain a plasma in a region of the gas containment structure. The LSP source includes a light collector element configured to collect at least a portion of broadband light emitted from the plasma.

TECHNICAL FIELD

The present invention generally relates to a laser sustained plasma (LSP) broadband light source and, in particular, an LSP source including reverse vortex flow.

BACKGROUND

The need for improved light sources used for inspection of ever-shrinking semiconductor devices continues to grow. One such light source includes a laser sustained plasma (LSP) broadband light source. LSP broadband light sources include LSP lamps, which are capable of producing high-power broadband light. The gas in the vessel is typically stagnant as most current LSP lamps do not have any mechanisms for forcing gas flow through the lamp except for natural convection caused by the buoyancy of hot plasma plume. Previous attempts at flowing gas through LSP lamps have resulted in instabilities within the LSP lamp caused by unsteady turbulent gas flow. These instabilities are amplified at higher power and at locations of mechanical elements (e.g., nozzles), whereby high radiative thermal load on these mechanical elements is created, resulting in overheating and melting. As such, it would be advantageous to provide a system and method to remedy the shortcomings of the previous approaches identified above.

SUMMARY

A laser-sustained light source is disclosed. In one embodiment, the laser-sustained light source includes a gas containment structure for containing a gas, wherein the gas containment structure comprises a body, a neck, and a shaft. In another embodiment, the laser-sustained light source includes a plurality of nozzles position in or below the neck of the gas containment structure. In another embodiment, the laser-sustained light source includes a plurality of gas delivery lines fluidically coupled to the plurality of nozzles and configured to deliver gas to the plurality of nozzles. In another embodiment, the laser-sustained light source includes one or more gas inlets fluidically coupled to the gas delivery lines for providing gas into the plurality of gas delivery lines. In another embodiment, the laser-sustained light source includes one or more gas outlets fluidically coupled to the gas containment structure and configured to flow gas out of the gas containment structure, wherein the one or more gas inlets and the one or more gas outlets are arranged to generate a vortex gas flow within the gas containment structure. In another embodiment, the laser-sustained light source includes a gas seal positioned at a base of the gas containment structure. In another embodiment, the laser-sustained light source includes a laser pump source configured to generate an optical pump to sustain a plasma in a region of the gas containment structure within an inner gas flow within the vortex gas flow. In another embodiment, the laser-sustained light source includes a light collector element configured to collect at least a portion of broadband light emitted from the plasma.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present disclosure are directed to improvements in the operation of flow-through plasma cell designs for use in laser-sustained plasma light sources. One of the most significant limitations for plasma lamp operation is the thermal stress placed on the glass of the plasma lamp and any other construction elements placed in the vicinity of the plasma (e.g., electrodes, seals, etc.). In particular, positioning high-power plasma in the proximity of construction elements (e.g., nozzle orifice) creates a high radiative thermal load on these construction elements and results in overheating and melting. For flow-through designs, removing the convection control elements from the plasma to safe distance results in their reduced efficiency. For example, almost half of the flow emerging from gas inlets of other designs fails to propagate into the main body of the plasma cell. A flow-through plasma cell design is described in U.S. patent application Ser. No. 17/223,942, filed on Apr. 6, 2021, which is incorporated herein by reference in the entirety.

Cooling of the glass lamp envelope is another severe problem in high-power lamp operation. These heat sources include hot gas circulating within the plasma lamp and large amounts of plasma VUV radiation that is absorbed on the inside surface of the glass of the lamp. Glass cooling occurs on the outside of the cell, resulting in large thermal gradients across the thickness of the glass. In some cases, the thermal gradients can exceed 100° C./mm. This creates an unfavorable thermal regime where the inside surface of the glass is much hotter than the outside surface, thereby reducing the efficiency of cooling. Uneven temperature distribution also creates a likelihood of glass damage.

Embodiments of the present disclosure are directed to an LSP light source implementing reverse vortex flow to organize gas flow through the LSP region of the LSP light source. Embodiments of the disclosure are directed to a transparent bulb, cell, or chamber used to contain high-pressure gas needed for LSP operation and gas transport components (gas inlet(s), delivery lines, nozzles, and gas outlet(s)) used to produce the reverse-vortex gas flow. Embodiments of the present disclosure are directed to a set of gas nozzles arranged in or below the neck of a body of the gas containment structure of a gas cell. The gas nozzles are arranged to generate gas jets in a spiral pattern that impinge on an inner surface of the body of the gas containment structure, which serve to efficiently cool the gas containment structure.

FIG.1is a schematic illustration of an LSP light source100with reverse-vortex flow, in accordance with one or more embodiments of the present disclosure. The LSP source100includes a reverse-flow vortex cell101. The LSP source100includes a pump source102configured to generate an optical pump104for sustaining a plasma110within the reverse-flow vortex cell101. For example, the pump source102may emit a beam of laser illumination suitable for pumping the plasma110. In embodiments, the light collector element106is configured to direct a portion of the optical pump104to a gas contained in a gas containment structure108of the vortex-producing cell107to ignite and/or sustain the plasma110. The pump source102may include any pump source known in the art suitable for igniting and/or sustaining plasma. For example, the pump source102may include one or more lasers (i.e., pump lasers). The pump beam may include radiation of any wavelength or wavelength range known in the art including, but not limited to, visible, IR radiation, NIR radiation, and/or UV radiation. The light collector element106is configured to collect a portion of broadband light115emitted from the plasma110.

The gas containment structure108may include one or more gas inlets120and one or more gas outlets122, which are arranged to form a reverse-flow vortex124within the interior of the gas containment structure108. The broadband light115emitted from the plasma110may be collected via one or more additional optics (e.g., a cold mirror112) for use in one or more downstream applications (e.g., inspection, metrology, or lithography). The LSP light source100may include any number of additional optical elements such as, but not limited to, a filter117or a homogenizer119for conditioning the broadband light115prior to the one or more downstream applications. The gas containment structure108may include a plasma cell, a plasma bulb (or lamp), or a plasma chamber.

FIG.2illustrates a simplified schematic view of the reverse-flow vortex cell101, in accordance with one or more embodiments of the present disclosure. In embodiments, the gas containment structure108of the reverse-flow vortex cell101includes a body202, a neck204, and a shaft206. In embodiments, the reverse-flow vortex cell101includes one or more nozzles206. The one or more nozzles206may be positioned in or below the neck204of the gas containment structure108. In embodiments, the reverse-flow vortex cell101includes one or more gas delivery lines208. The one or more delivery lines208may direct gas through the shaft208to the one or more nozzles206. The one or more delivery lines208may be formed in any suitable manner. For example, the one or more delivery lines208may be extruded.

In embodiments, the reverse-flow vortex cell101includes one or more gas inlets202configured to flow the gas into the reverse-flow vortex cell101. For example, the reverse-flow vortex cell101includes a set of gas inlets212distributed along the periphery of the vortex cell101and configured to flow gas into the set of gas delivery lines208, which in turn deliver gas to the set of gas nozzles206. The reverse-flow vortex cell101also includes one or more gas outlets214. For example, the reverse-flow vortex cell101may include a first gas outlet214located at a center location of the vortex cell101.

In embodiments, the reverse-flow vortex cell101includes seal210. For example, the seal210may include a glass-to-metal seal, which serves to hermetically couple the shaft205of the gas containment structure108to flange assembly211. The flange assembly211may terminate/seal the glass portion of the gas containment structure108. In embodiments, the flange assembly211may secure inlet and/or outlet pipes or tubes and additional mechanical and electronic components. The use of a flanged plasma cell is described in at least U.S. Pat. No. 9,775,226, issued on Sep. 26, 2017; and U.S. Pat. No. 9,185,788, issued on Nov. 10, 2015, which are each incorporated previously herein by reference in the entirety.

The gas containment structure108formed from an optically transmissive material (e.g., glass) configured for containing the plasma-forming gas and transmitting optical pump illumination104and broadband light115. For example, the body202of the gas containment structure108may include a spherical section formed from a material transparent to at least a portion of the pump illumination104and the broadband light115. It is noted that the body202is not limited to a spherical shape and may take on any suitable shape including, but not limited to, a spherical shape, an ellipsoidal shape, a cylindrical shape, and so on. The transmissive portion of the gas containment structure of the vortex cell101can be formed from any number of different optical materials. For example, the transmissive portion of the gas containment structure108may be formed from, but is not limited to, sapphire, crystal quartz, CaF2, MgF2, or fused silica. It is noted that the vortex flow of the vortex cell101keeps the hot plume of the plasma110from the walls of the vortex cell101, which reduces the thermal head load on the walls and allows for the use of optical materials sensitive to overheating (e.g., glass, CaF2, MgF2, crystal quartz, and the like).

During operation, in embodiments, the set of nozzles206are configured to generate a set of gas jets216in a spiral pattern impinging on an inner surface of the body202of the gas containment structure108. For example, the nozzles206direct fast-moving spiraling jets of gas into the body202of the gas containment structure108. In this embodiment, the gas flow moves upward into body202and impinges on the wall of the body202. Then, axial flow218reverses direction (moving downward) and leaves the body near the axis of neck204of the gas containment structure108. The plasma110, located at the axis in the region of reverse flow, creates hot plume of gas that is entrained and mixed with the return flow toward the centrally-located outlet214.

It is noted that the reverse-flow vortex cell101serves to distance the various mechanical components of the vortex cell101(e.g., seal, outlet, inlet, and the like) from the plasma110, thereby reducing thermal load on these elements. For example, the heat load on a swirler used in previous solutions that is located at 50 mm from a 20 kW plasma and absorbing 20% of plasma radiation is approximately 300 W and is likely to require additional cooling provisions (e.g., water cooling). In the case of the reverse-flow vortex cell101of this disclosure, the directly illuminated regions of the cell101are placed at much larger distance from the plasma110, thereby reducing the heat load to about 20 W. This amount of heat can be easily removed by the gas passing through delivery lines208and nozzles206. In embodiments, there is additional radiation protection for delivery lines placed in the shadow created by reduced diameter of the neck204.

Another benefit of reverse-flow vortex cell of the present disclosure includes placement of the nozzles206very close to the neck204of cell101and directed into the divergent area of the body202, which forms fast moving jets in the immediate vicinity of neck204. The gas jets entrain additional gas into body202, thereby increasing the efficiency of the gas flow (e.g., by a factor of about two). Without this feature, inefficiency may result from the cold inlet gas entrained by the back flow below the neck region.

Yet another benefit of the reverse-flow vortex cell101of the present disclosure includes directing the gas jets on the internal surface of body202of the cell101. This provides more efficient cooling the glass of the cell101than cooling from the outside of the cell101. The heat transfer coefficient (HTC) between cold gas and hot glass increases with gas density. Because of higher operating pressure, jets originating from nozzles206and impinging on the internal glass surface carry much denser gas than gas outside of the cell101and therefore have about 10 times higher HTC that can be achieved from outside of the cell101. In addition, this cooling is applied to the same surfaces where the glass is heated by plasma radiation, resulting in very efficient cooling compared to traditional methods.

FIG.3illustrates a schematic view of the reverse-flow plasma cell101including binding302and seal shielding304, in accordance with one or more embodiments of the present disclosure. In embodiments, the binding302is applied to the delivery lines208or the nozzles206to stabilize the one or more nozzles206. It is noted that there is a significant lateral recoil force expected to be applied to the nozzles206. Typical gas volumes passing through a given nozzle is about 1 kg/s at 50 m/s. The change of momentum in response to the gas flow is approximately 20 N. In order to stabilize nozzle positions, the binding302can be applied to delivery lines208and/or nozzles206in a manner that connects them together in a rigid structure. In embodiments, the binding302may be positioned in the neck shadow protected from direct plasma radiation306from the plasma110. The binding302may include any mechanical structure capable of stabilizing the position of the delivery lines and/or nozzles. For example, the binding302may include, but is not limited to, a wire wrapped around the set of deliver lines208and/or nozzles206. In additional embodiments, the optical shielding304may be attached to the delivery lines208to protect the seal210(and other components) from direct plasma radiation306to reduce the thermal load on seal210and its light-induced degradation.

FIG.4illustrates a schematic view of a gas distribution manifold402of the reverse-flow plasma cell, in accordance with one or more embodiments of the present disclosure. The distribution manifold402is configured to distribute gas into and out of the gas containment structure108of the reverse-flow vortex cell101. In embodiments, the distribution manifold402includes a gas inlet manifold404. Additionally, the gas distribution manifold402includes an inlet plenum406. In embodiments, the delivery lines206are fluidically coupled to the inlet plenum406. In this embodiment, gas is received by the intake manifold404and directed to the inlet plenum406. The inlet plenum406then equally distributes gas to the delivery lines206. In embodiments, the gas distribution manifold402includes a gas exhaust manifold408. The gas exhaust manifold408is fluidically coupled to the outlet214.

In embodiments, the distribution manifold is part of a flange assembly410. For example, the flange assembly410may include a top flange412and a bottom flange414. In this example, the top flange412may couple to the bottom flange414, thereby hermetically sealing the end of the glass containment structure108. In embodiments, the intake manifold404and the outlet manifold408may be integrated into the bottom flange414and the seal416may be integrated into the top flange412such that when the top flange412and the bottom flange414are coupled together the gas distribution pathway is complete and the end portion of the gas containment structure108is sealed.

It is noted that the shape of the gas containment structure108of the plasma cell101may take on any shape and is not limited to the shape depicted previously herein. For example, as shown inFIG.5, the shaft, neck, and body of the gas containment structure108may all have a cylindrical shape of the same diameter, resulting in a purely cylindrical lamp, with the top of the gas containment structure108maintaining a curved shape to maintain gas flow reversal.

FIGS.6A-6Eillustrate a set of schematic diagrams of the reverse-flow plasma cell101including a set of inclined delivery lines602, in accordance with one or more embodiments of the present disclosure.FIG.6Ais a perspective view of the reverse-flow plasma cell101equipped with the set of inclined delivery lines602.FIG.6Bis a top view of the reverse-flow plasma cell101equipped with the set of inclined delivery lines602.FIG.6Cis a top view of the delivery line assembly601including the gas delivery lines602.FIG.6Dis a bottom view of the delivery line assembly601including the gas delivery lines602.FIG.6Eis a cross-sectional view of the reverse-flow plasma cell101including the gas delivery lines602.

In this embodiment, the construction of the delivery lines and nozzles is simplified by inclining the delivery lines. In this embodiment, the reverse-flow vortex cell101includes a delivery line assembly601. The delivery line assembly601includes a set of delivery lines602arranged to generate a set of gas jets216that impinge the inner surface of the body202of the gas containment structure108in a spiral pattern. It is further noted that jets formed by the nozzles would have most of the propulsion force directed along the axes of delivery lines602. In this embodiment, as shown inFIG.6D, the gas inlets212, which fluidically couple to the deliver lines602, are located at the periphery of the gas containment structure108, while the outlet214is located at the center of the gas containment structure108.

FIGS.7A-7Dillustrate a set of schematic diagrams of the reverse-flow plasma cell101including a set of inclined delivery lines702, in accordance with one or more alternative embodiments of the present disclosure. In this embodiment, the gas inlets212are located at a central region of the gas containment structure108and the gas outlet214is located at the periphery of the gas containment structure108.

Any number of peripheral or centered inlet sets may be utilized within the cells of the present disclosure. The inlets and outlets and the rate of flow through them are to be configured depending on the desired flow regime. The location of the gas inlets212and gas outlets214as well as inclination and shapes of delivery lines206may be adjusted to suit other design goals (e.g., reducing diameter of lamp shaft and seal for better pressure handling).

FIG.8illustrates a simplified schematic view of the reverse-flow vortex cell101equipped with an extended top pocket802, in accordance with one or more embodiments of the present disclosure. In embodiments, the gas inlets212are extended along the gas containment structure108such that the gas nozzles206are located at mouth of the body202of the gas containment structure108. In addition, the extended top pocket802may be located opposite the gas nozzles206. This extended top pocket802servers to create a large distance between the plasma110and the glass wall of the gas containment structure108in the top portion of the glass containment structure108, where convection cooling is minimal.

The generation of a light-sustained plasma is also generally described in U.S. Pat. No. 7,435,982, issued on Oct. 14, 2008, which is incorporated by reference herein in the entirety. The generation of plasma is also generally described in U.S. Pat. No. 7,786,455, issued on Aug. 31, 2010, which is incorporated by reference herein in the entirety. The generation of plasma is also generally described in U.S. Pat. No. 7,989,786, issued on Aug. 2, 2011, which is incorporated by reference herein in the entirety. The generation of plasma is also generally described in U.S. Pat. No. 8,182,127, issued on May 22, 2012, which is incorporated by reference herein in the entirety. The generation of plasma is also generally described in U.S. Pat. No. 8,309,943, issued on Nov. 13, 2012, which is incorporated by reference herein in the entirety. The generation of plasma is also generally described in U.S. Pat. No. 8,525,138, issued on Feb. 9, 2013, which is incorporated by reference herein in the entirety. The generation of plasma is also generally described in U.S. Pat. No. 8,921,814, issued on Dec. 30, 2014, which is incorporated by reference herein in the entirety. The generation of plasma is also generally described in U.S. Pat. No. 9,318,311, issued on Apr. 19, 2016, which is incorporated by reference herein in the entirety. The generation of plasma is also generally described in U.S. Pat. No. 9,390,902, issued on Jul. 12, 2016, which is incorporated by reference herein in the entirety. In a general sense, the various embodiments of the present disclosure should be interpreted to extend to any plasma-based light source known in the art.

Referring generally toFIGS.1-8, the pump source102may include any laser system known in the art capable of serving as an optical pump for sustaining a plasma. For instance, the pump source102may include any laser system known in the art capable of emitting radiation in the infrared, visible and/or ultraviolet portions of the electromagnetic spectrum.

In embodiments, the pump source102may include a laser system configured to emit continuous wave (CW) laser radiation. For example, the pump source102may include one or more CW infrared laser sources. In embodiments, the pump source102may include one or more lasers configured to provide laser light at substantially a constant power to the plasma110. In embodiments, the pump source102may include one or more modulated lasers configured to provide modulated laser light to the plasma110. In embodiments, the pump source102may include one or more pulsed lasers configured to provide pulsed laser light to the plasma. In embodiments, the pump source102may include one or more diode lasers. For example, the pump source102may include one or more diode lasers emitting radiation at a wavelength corresponding with any one or more absorption lines of the species of the gas contained within the gas containment structure. A diode laser of pump source102may be selected for implementation such that the wavelength of the diode laser is tuned to any absorption line of any plasma (e.g., ionic transition line) or any absorption line of the plasma-producing gas (e.g., highly excited neutral transition line) known in the art. As such, the choice of a given diode laser (or set of diode lasers) will depend on the type of gas used in the light source100. In embodiments, the pump source102may include an ion laser. For example, the pump source102may include any noble gas ion laser known in the art. For instance, in the case of an argon-based plasma, the pump source102used to pump argon ions may include an Ar+ laser. In embodiments, the pump source102may include one or more frequency converted laser systems. In embodiments, the pump source102may include a disk laser. In embodiments, the pump source102may include a fiber laser. In embodiments, the pump source102may include a broadband laser. In embodiments, the pump source102may include one or more non-laser sources. The pump source102may include any non-laser light source known in the art. For instance, the pump source102may include any non-laser system known in the art capable of emitting radiation discretely or continuously in the infrared, visible or ultraviolet portions of the electromagnetic spectrum.

In embodiments, the pump source102may include two or more light sources. In embodiments, the pump source102may include two or more lasers. For example, the pump source102(or “sources”) may include multiple diode lasers. In embodiments, each of the two or more lasers may emit laser radiation tuned to a different absorption line of the gas or plasma within source100.

The light collector element106may include any light collector element known in the art of plasma production. For example, the light collector element106may include one or more elliptical reflectors, one or more spherical reflectors, and/or one or more parabolic reflectors. The light collector element106may be configured to collect any wavelength of broadband light from the plasma110known in the art of plasma-based broadband light sources. For example, the light collector element106may be configured to collect infrared light, visible light, ultraviolet (UV) light, near ultraviolet (NUV), vacuum UV (VUV) light, and/or deep UV (DUV) light from the plasma110.

The transmitting portion of the gas containment structure of source100(e.g., transmission element, bulb or window) may be formed from any material known in the art that is at least partially transparent to the broadband light115generated by plasma110and/or the pump light104. In embodiments, one or more transmitting portions of the gas containment structure (e.g., transmission element, bulb or window) may be formed from any material known in the art that is at least partially transparent to VUV radiation, DUV radiation, UV radiation, NUV radiation and/or visible light generated within the gas containment structure. Further, one or more transmitting portions of the gas containment structure may be formed from any material known in the art that is at least partially transparent to IR radiation, visible light and/or UV light from the pump source102. In embodiments, one or more transmitting portions of the gas containment structure may be formed from any material known in the art transparent to both radiation from the pump source102(e.g., IR source) and radiation (e.g., VUV, DUV, UV, NUV radiation and/or visible light) emitted by the plasma110.

The gas containment structure108may contain any selected gas (e.g., argon, xenon, mercury or the like) known in the art suitable for generating a plasma upon absorption of pump illumination. In embodiments, the focusing of pump illumination510from the pump source102into the volume of gas causes energy to be absorbed by the gas or plasma (e.g., through one or more selected absorption lines) within the gas containment structure, thereby “pumping” the gas species in order to generate and/or sustain a plasma110. In embodiments, although not shown, the gas containment structure may include a set of electrodes for initiating the plasma110within the internal volume of the gas containment structure108, whereby the illumination from the pump source102maintains the plasma110after ignition by the electrodes.

The source100may be utilized to initiate and/or sustain the plasma110in a variety of gas environments. In embodiments, the gas used to initiate and/or maintain plasma110may include an inert gas (e.g., noble gas or non-noble gas) or a non-inert gas (e.g., mercury). In embodiments, the gas used to initiate and/or maintain a plasma110may include a mixture of gases (e.g., mixture of inert gases, mixture of inert gas with non-inert gas or a mixture of non-inert gases). For example, gases suitable for implementation in source100may include, but are not limited, to Xe, Ar, Ne, Kr, He, N2, H2O, O2, H2, D2, F2, CH4, CF6one or more metal halides, a halogen, Hg, Cd, Zn, Sn, Ga, Fe, Li, Na, Ar:Xe, ArHg, KrHg, XeHg, and any mixture thereof. The present disclosure should be interpreted to extend to any gas suitable for sustaining a plasma within a gas containment structure.

In embodiments, the LSP light source100further includes one or more additional optics configured to direct the broadband light115from the plasma110to one or more downstream applications. The one or more additional optics may include any optical element known in the art including, but not limited to, one or more mirrors, one or more lenses, one or more filters, one or more beam splitters, or the like. The light collector element106may collect one or more of visible, NUV, UV, DUV, and/or VUV radiation emitted by plasma110and direct the broadband light115to one or more downstream optical elements. For example, the light collector element106may deliver infrared, visible, NUV, UV, DUV, and/or VUV radiation to downstream optical elements of any optical characterization system known in the art, such as, but not limited to, an inspection tool, a metrology tool, or a lithography tool. In this regard, the broadband light115may be coupled to the illumination optics of an inspection tool, metrology tool, or lithography tool.

FIG.9is a schematic illustration of an optical characterization system900implementing the LSP broadband light source100illustrated in any ofFIGS.1through8(or any combination thereof), in accordance with one or more embodiments of the present disclosure.

It is noted herein that system900may comprise any imaging, inspection, metrology, lithography, or other characterization/fabrication system known in the art. In this regard, system900may be configured to perform inspection, optical metrology, lithography, and/or imaging on a sample907. Sample907may include any sample known in the art including, but not limited to, a wafer, a reticle/photomask, and the like. It is noted that system900may incorporate one or more of the various embodiments of the LSP broadband light source100described throughout the present disclosure.

In embodiments, sample907is disposed on a stage assembly912to facilitate movement of sample907. The stage assembly912may include any stage assembly912known in the art including, but not limited to, an X-Y stage, an R-8 stage, and the like. In embodiments, stage assembly912is capable of adjusting the height of sample907during inspection or imaging to maintain focus on the sample907.

In embodiments, the set of illumination optics903is configured to direct illumination from the broadband light source100to the sample907. The set of illumination optics903may include any number and type of optical components known in the art. In embodiments, the set of illumination optics903includes one or more optical elements such as, but not limited to, one or more lenses902, a beam splitter904, and an objective lens906. In this regard, set of illumination optics903may be configured to focus illumination from the LSP broadband light source100onto the surface of the sample907. The one or more optical elements may 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.

In embodiments, the set of collection optics905is configured to collect light reflected, scattered, diffracted, and/or emitted from sample907. In embodiments, the set of collection optics905, such as, but not limited to, focusing lens910, may direct and/or focus the light from the sample907to a sensor916of a detector assembly914. It is noted that sensor916and detector assembly914may include any sensor and detector assembly known in the art. For example, the sensor916may include, but is not limited to, a charge-coupled device (CCD) detector, a complementary metal-oxide semiconductor (CMOS) detector, a time-delay integration (TDI) detector, a photomultiplier tube (PMT), an avalanche photodiode (APD), and the like. Further, sensor916may include, but is not limited to, a line sensor or an electron-bombarded line sensor.

In embodiments, detector assembly914is communicatively coupled to a controller918including one or more processors920and memory medium922. For example, the one or more processors920may be communicatively coupled to memory922, wherein the one or more processors920are configured to execute a set of program instructions stored on memory922. In embodiments, the one or more processors920are configured to analyze the output of detector assembly914. In embodiments, the set of program instructions are configured to cause the one or more processors920to analyze one or more characteristics of sample907. In embodiments, the set of program instructions are configured to cause the one or more processors920to modify one or more characteristics of system900in order to maintain focus on the sample907and/or the sensor916. For example, the one or more processors920may be configured to adjust the objective lens906or one or more optical elements902in order to focus illumination from LSP broadband light source100onto the surface of the sample907. By way of another example, the one or more processors920may be configured to adjust the objective lens906and/or one or more optical elements902in order to collect illumination from the surface of the sample907and focus the collected illumination on the sensor916.

It is noted that the system900may 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.

FIG.10illustrates a simplified schematic diagram of an optical characterization system1000arranged in a reflectometry and/or ellipsometry configuration, in accordance with one or more embodiments of the present disclosure. It is noted that the various embodiments and components described with respect toFIGS.1through9may be interpreted to extend to the system ofFIG.10. The system1000may include any type of metrology system known in the art.

In embodiments, system1000includes the LSP broadband light source100, a set of illumination optics1016, a set of collection optics1018, a detector assembly1028, and the controller918including the one or more processors920and memory922.

In this embodiment, the broadband illumination from the LSP broadband light source100is directed to the sample907via the set of illumination optics1016. In embodiments, the system1000collects illumination emanating from the sample via the set of collection optics1018. The set of illumination optics1016may include one or more beam conditioning components1020suitable for modifying and/or conditioning the broadband beam. For example, the one or more beam conditioning components1020may include, but are not limited to, one or more polarizers, one or more filters, one or more beam splitters, one or more diffusers, one or more homogenizers, one or more apodizers, one or more beam shapers, or one or more lenses.

In embodiments, the set of illumination optics1016may utilize a first focusing element1022to focus and/or direct the beam onto the sample907disposed on the sample stage1012. In embodiments, the set of collection optics1018may include a second focusing element1026to collect illumination from the sample907.

In embodiments, the detector assembly1028is configured to capture illumination emanating from the sample907through the set of collection optics1018. For example, the detector assembly1028may receive illumination reflected or scattered (e.g., via specular reflection, diffuse reflection, and the like) from the sample907. By way of another example, the detector assembly1028may receive illumination generated by the sample907(e.g., luminescence associated with absorption of the beam, and the like). It is noted that detector assembly1028may include any sensor and detector assembly known in the art. For example, the sensor may include, but is not limited to, CCD detector, a CMOS detector, a TDI detector, a PMT, an APD, and the like.

The set of collection optics1018may further include any number of collection beam conditioning elements1030to direct and/or modify illumination collected by the second focusing element1026including, but not limited to, one or more lenses, one or more filters, one or more polarizers, or one or more phase plates.

The system1000may 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.

A description of an inspection/metrology tools suitable for implementation in the various embodiments of the present disclosure are provided in U.S. Pat. No. 7,957,066, entitled “Split Field Inspection System Using Small Catadioptric Objectives,” issued on Jun. 7, 2011; U.S. Pat. No. 7,345,825, entitled “Beam Delivery System for Laser Dark-Field Illumination in a Catadioptric Optical System,” issued on Mar. 18, 2018; 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. Pat. No. 9,228,943, entitled “Dynamically Adjustable Semiconductor Metrology System,” issued on Jan. 5, 2016; 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,” issued on Oct. 2, 2001, which are each incorporated herein by reference in their entirety.

The one or more processors920of controller918may include any processor or processing element known in the art. For the purposes of the present disclosure, the term “processor” or “processing element” may be broadly defined to encompass any device having one or more processing or logic elements (e.g., one or more micro-processor devices, one or more application specific integrated circuit (ASIC) devices, one or more field programmable gate arrays (FPGAs), or one or more digital signal processors (DSPs)). In this sense, the one or more processors920may include any device configured to execute algorithms and/or instructions (e.g., program instructions stored in memory) from a memory medium922. The memory medium922may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors920.

In embodiments, the LSP light source100and systems900,1000, as described herein, may be configured as a “stand alone tool,” interpreted herein as a tool that is not physically coupled to a process tool. In other embodiments, such an inspection or metrology system may be coupled to a process tool (not shown) by a transmission medium, which may include wired and/or wireless portions. The process tool may include any process tool known in the art such as a lithography tool, an etch tool, a deposition tool, a polishing tool, a plating tool, a cleaning tool, or an ion implantation tool. The results of inspection or measurement performed by the systems described herein may be used to alter a parameter of a process or a process tool using a feedback control technique, a feedforward control technique, and/or an in-situ control technique. The parameter of the process or the process tool may be altered manually or automatically.