阅读说明：本技术 高功率宽频带照明源 (High-power wide-band illumination source ) 是由 O·可哈达金 I·贝泽尔 于 2018-07-23 设计创作，主要内容包括：本发明揭示一种用于产生宽频带辐射的系统。所述系统包含目标材料源,其经配置以将液态或固态目标材料中的一或多者输送到腔室的等离子体形成区域。所述系统进一步包含泵源,其经配置以产生泵辐射来激发所述腔室的所述等离子体形成区域中的所述目标材料产生宽频带辐射。所述系统经进一步配置以通过无窗孔隙将所述腔室的所述等离子体形成区域中所产生的所述宽频带辐射的至少一部分传输出所述腔室。(A system for generating broadband radiation is disclosed. The system includes a target material source configured to deliver one or more of a liquid or solid target material to a plasma formation region of a chamber. The system further includes a pump source configured to generate pump radiation to excite the target material in the plasma formation region of the chamber to generate broadband radiation. The system is further configured to transmit at least a portion of the broadband radiation generated in the plasma formation region of the chamber out of the chamber through a windowless aperture.)

1. An apparatus, comprising:

a chamber configured to contain a quantity of buffer gas;

a source of target material positioned on a first side of the chamber;

a debris collector positioned on a second side of the chamber opposite the source of target material,

wherein the target material source is configured to deliver a flow of target material through a plasma formation region of the chamber, wherein the debris collector is configured to collect target material;

a pump source configured to deliver pump radiation to the plasma formation region of the chamber, wherein the pump radiation is sufficient to generate broadband radiation via formation of a plasma by exciting the target material within the plasma formation region of the chamber;

one or more focusing optics configured to focus the pump radiation into the plasma formation region; and

one or more reflective collection optical elements configured to collect a portion of the broadband radiation from the plasma and transport the portion of the broadband radiation through an aperture in a wall of the chamber to one or more optical elements outside the chamber.

2. The apparatus of claim 1, wherein the broadband radiation comprises:

at least one of vacuum ultraviolet VUV or deep ultraviolet DUV radiation.

3. The apparatus of claim 1, wherein the pump source, the one or more focusing optics, and the reflection collection optics are configured such that the broadband radiation has a numerical aperture higher than a NA of the pump radiation.

4. The apparatus of claim 1, wherein the pump source, the one or more focusing optics, and the reflection collection optics are configured such that the broadband radiation has a numerical aperture that is lower than an NA of the pump radiation.

5. The apparatus of claim 1, wherein the aperture in the wall of the chamber is windowless.

6. The apparatus of claim 1, wherein the stream of target material comprises:

at least one of a stream of liquid target material, a stream of solid target material, or a series of droplets of the target material.

7. The apparatus of claim 1, wherein the target material source is configured to convey the target material stream at a speed between 10m/s to 300 m/s.

8. The apparatus of claim 1, wherein the stream of target material has a diameter between 10 μ ι η and 2000 μ ι η.

9. The apparatus of claim 1, wherein the target material comprises:

at least one of argon, xenon, neon, or helium.

10. The apparatus of claim 9, wherein the target material comprises:

a mixture containing at least one of argon, xenon, neon, or helium.

11. The apparatus of claim 1, wherein the buffer gas comprises:

an inert gas.

12. The apparatus of claim 1, wherein the buffer gas is the same as the target material.

13. The apparatus of claim 1, wherein the buffer gas is different from the target material.

14. The apparatus of claim 1, wherein the chamber is configured to contain the gas at a pressure between 0.1atm and 2.0 atm.

15. The apparatus of claim 1, wherein the pump source comprises:

at least one of a continuous wave CW laser, a pulsed laser, or a modulated CW laser.

16. The apparatus of claim 15, wherein the pump source is configured to generate pump radiation having a pulse spacing of 100-1000 nanoseconds.

17. The apparatus of claim 15, wherein the pump source is configured to generate pump radiation at a power of between 3kW to 100 kW.

18. The apparatus of claim 15, wherein the pump source is configured to generate a fluid having a pressure greater than 10⁵W/cm²Pump radiation of peak laser intensity.

19. An apparatus, comprising:

a broadband source, comprising:

a chamber configured to contain a quantity of an inert gas;

a source of target material positioned on a first side of the chamber;

a debris collector positioned on a second side of the chamber opposite the source of target material,

wherein the target material source is configured to deliver a flow of target material through a plasma formation region of the chamber, wherein the debris collector is configured to collect target material,

a pump source configured to deliver pump radiation to the plasma formation region of the chamber, wherein the pump radiation is sufficient to generate broadband radiation via formation of a plasma by exciting the target material within the plasma formation region of the chamber;

one or more focusing optics configured to focus the pump radiation into the plasma formation region; and

one or more reflective collection optics configured to collect a portion of the broadband radiation from the plasma and transport the portion of the broadband radiation through an aperture in a wall of the chamber to one or more optics outside the chamber;

a set of illuminator optics configured to direct the broadband radiation from the one or more reflection collection optics to one or more samples;

a detector; and

a set of projection optics configured to receive illumination from a surface of the one or more samples and direct the illumination from the one or more samples to the detector.

20. The apparatus of claim 19, wherein the broadband radiation comprises:

at least one of vacuum ultraviolet VUV or deep ultraviolet DUV radiation.

21. The apparatus of claim 19, wherein the pump source, the one or more focusing optics, and the reflection collection optics are configured such that the broadband radiation has a numerical aperture higher than a NA of the pump radiation.

22. The apparatus of claim 19, wherein the pump source, the one or more focusing optics, and the reflection collection optics are configured such that the broadband radiation has a numerical aperture that is lower than an NA of the pump radiation.

23. The apparatus of claim 19, wherein the aperture in the wall of the chamber is windowless.

24. A method, comprising:

conveying a stream of a target material through a plasma formation region of a gas chamber;

collecting debris from the plasma formation region;

generating pump radiation;

focusing the pump radiation into the plasma formation region of the chamber to generate broadband radiation via formation of a plasma by exciting the target material within the plasma formation region of the chamber; and

a portion of the broadband radiation is collected from the plasma and transported through a windowless aperture in a wall of the chamber to one or more optical elements outside the chamber.

Technical Field

The present invention relates generally to plasma-based radiation sources, and more particularly, to Laser Sustained Plasma (LSP) broadband radiation sources that include plasmas generated at near atmospheric pressure.

Background

As the demand for integrated circuits with smaller and smaller device features continues to increase, so does the need for improved illumination sources for verifying these ever-shrinking devices. One such illumination source comprises a Laser Sustained Plasma (LSP) radiation source. The laser sustained plasma light source is capable of generating high power broadband light. Laser sustained plasma light sources operate by focusing laser radiation into a gas volume to excite a gas, such as argon or xenon, into a plasma state capable of emitting light. This effect is commonly referred to as "pumping" the plasma. In the current application, a relatively high density plasma is required and realized by providing a high pressure (30atm to 200atm) to a target gas.

The transmissive element in the LSP radiation source experiences high pressures and temperatures due to the target gas within the chamber that houses the plasma. The transmission window, which is typically made of a material such as calcium fluoride, magnesium fluoride or lithium fluoride, also transmits radiation below 190nm generated by the plasma. The combination of high pressure, high temperature and radiation below 190nm makes the lifetime of the transmission optics used in the LSP radiation source very short.

Accordingly, it would be desirable to provide a system and method that remedies one or more deficiencies in the above-described methods.

Disclosure of Invention

In accordance with one or more embodiments of the present disclosure, an apparatus is disclosed. In one embodiment, the apparatus comprises a chamber. In another embodiment, the chamber is configured to contain an amount of buffer gas. In another embodiment, the apparatus includes a source of target material positioned on a first side of the chamber. In another embodiment, the apparatus includes a debris collector. In another embodiment, the apparatus includes a debris collector positioned on a second side of the chamber opposite the source of target material. In another embodiment, the target material source is configured to deliver a stream of target material through a plasma formation region of the chamber. In another embodiment, the debris collector is configured to collect a target material. In another embodiment, the apparatus includes a pump source. In another embodiment, the apparatus includes a pump source configured to deliver pump radiation to the plasma formation region of the chamber. In another embodiment, the pump radiation from the pump source is sufficient to generate broadband radiation via formation of a plasma by exciting the target material within the plasma formation region of the chamber. In another embodiment, the apparatus includes one or more focusing optical elements. In another embodiment, the one or more focusing optical elements are configured to focus the pump radiation into the plasma formation region. In another embodiment, the apparatus includes one or more reflection collection optical elements. In another embodiment, the one or more reflective collection optical elements are configured to collect a portion of the broadband radiation from the plasma and transport the portion of the broadband radiation through an aperture in a wall of the chamber to one or more optical elements outside the chamber.

In accordance with one or more embodiments of the present disclosure, a system is disclosed. In one embodiment, the system includes a broadband source. In another embodiment, the broadband source includes a chamber configured to contain a quantity of an inert gas. In another embodiment, the broadband source includes a source of target material positioned on a first side of the chamber. In another embodiment, the broadband source includes a debris collector positioned on a second side of the chamber opposite the source of target material. In another embodiment, the target material source is configured to deliver a stream of target material through a plasma formation region of the chamber. In another embodiment, the debris collector is configured to collect a target material. In another embodiment, the broadband source comprises a pump source. In another embodiment, the pump source is configured to deliver pump radiation to the plasma formation region of the chamber. In another embodiment, the pump radiation from the pump source is sufficient to generate broadband radiation via formation of a plasma by exciting the target material within the plasma formation region of the chamber. In another embodiment, the broadband source includes one or more focusing optical elements. In another embodiment, the one or more focusing optical elements are configured to focus the pump radiation into the plasma formation region. In another embodiment, the broadband source includes one or more reflection collection optical elements. In another embodiment, the one or more reflective collection optical elements are configured to collect a portion of the broadband radiation from the plasma and transport the portion of the broadband radiation through an aperture in a wall of the chamber to one or more optical elements outside the chamber. In another embodiment, the broadband source includes a set of illuminator optics. In another embodiment, the illuminator optics group is configured to direct the broadband radiation from the one or more reflection collection optics to one or more samples. In another embodiment, the broadband source includes a detector. In another embodiment, the broadband source comprises a set of projection optics. In another embodiment, the set of projection optics is configured to receive illumination from a surface of the one or more samples and to direct the illumination from the one or more samples to the detector.

According to one or more embodiments of the present disclosure, a method is disclosed. In one embodiment, the method includes: a stream of the target material is conveyed through a plasma formation region of the gas chamber. In another embodiment, the method includes: collecting debris from the plasma formation region. In another embodiment, the method includes: pump radiation is generated. In another embodiment, the method includes: focusing the pump radiation into the plasma formation region of the chamber to generate broadband radiation via formation of a plasma by exciting the target material within the plasma formation region of the chamber. In another embodiment, the method includes: a portion of the broadband radiation is collected from the plasma and transported through a windowless aperture in a wall of the chamber to one or more optical elements outside the chamber.

Drawings

The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying drawings in which:

fig. 1 illustrates a simplified schematic diagram of a Laser Sustained Plasma (LSP) broadband radiation source in accordance with one or more embodiments of the present disclosure;

fig. 2A illustrates a pump and collection configuration including a low NA pump and a high NA collection in accordance with one or more embodiments of the present disclosure;

fig. 2B illustrates a pump and collection configuration including a high NA pump and a low NA collection in accordance with one or more embodiments of the present disclosure;

FIG. 3 illustrates a simplified schematic diagram of an optical characterization system implementing an LSP radiation source in accordance with one or more embodiments of the present disclosure; and

fig. 4 illustrates a flow diagram depicting a method for generating broadband radiation in accordance with one or more embodiments of the present disclosure.

Detailed Description

The present invention has been particularly shown and described with respect to particular embodiments and particular features thereof. The embodiments set forth herein are considered to be illustrative and not restrictive. It will be readily apparent to persons skilled in the relevant art that various changes and modifications in form and detail can be made therein without departing from the spirit and scope of the invention.

The present invention generally relates to a Laser Sustained Plasma (LSP) radiation source. LSPs include a material source that provides one or more target materials in non-gaseous form (e.g., argon, xenon, neon, or helium) for laser excitation. For example, an LSP can provide a target material in the form of at least a liquid, a solid, or a combination of a liquid and a solid. For example, the target material provided by the material source may be provided by one or more of a jet, a stream, a slurry, a mist, a spray, droplets, beads, granules, particles, or another other non-gaseous form of the material. The plasma generated by the LSP emits broadband radiation that is directed out of the LSP by the reflective collection optics through the windowless aperture. It is noted herein that an advantage of the present invention is the utilization of reflective optics that do not require a transmissive window. It is noted herein that another advantage of the present invention is that high pressure gas chambers are not required for transporting high density target materials in solid, liquid, or a combination of solid and liquid.

Reference will now be made in detail to the disclosed subject matter as illustrated in the accompanying drawings.

Referring generally to fig. 1-5, systems and methods for generating an improved Laser Sustained Plasma (LSP) radiation source in accordance with one or more embodiments of the present disclosure are described. Embodiments of the present invention are directed to delivering a target material in the form of a liquid jet, a droplet, a frozen jet, a frozen droplet, a slurry, a stream, or a combination of these target material forms. Additional embodiments of the present invention are directed to liquid jets having a diameter of 10 microns to 2000 microns and/or droplets having a velocity of about 10m/s to about 300 m/s. Additional embodiments of the present invention are directed to delivering target materials at atmospheric or near atmospheric pressures (e.g., 0.1atm to 2 atm). Additional embodiments of the present invention utilize reflective collection optics to transmit broadband radiation from the LSP radiation source through the windowless aperture. It should be noted herein that the enhanced rapid flow of target material within the chamber may facilitate stable plasma 116 generation. Additional embodiments of the present invention use high Numerical Aperture (NA) (e.g., approximately π srad) broadband reflective optics to collect broadband radiation such as, but not limited to, VUV and/or DUV radiation. It is further noted herein that in order for the LSP radiation source to have significant brightness in the DUV and/or VUV, a relatively high density plasma is required. For example, the density of the LSP radiation sources should be high enough to absorb the pump beam and also dense enough to provide sufficient emissivity in the DUV and/or VUV and other spectral regions. Embodiments of the invention deliver a high density working gas to the plasma in the form of a liquid or solid jet.

Fig. 1 illustrates a simplified schematic diagram of a broadband LSP radiation source 100 in accordance with one or more embodiments of the present disclosure. In one embodiment, the LSP radiation source 100 includes a target material source 102, a pump source 108, pump light focusing optics 110, and a set of collection optics 120. In another embodiment, the LSP radiation source 100 includes a debris collector 124. It should be noted that LSP radiation source 100 may generate broadband radiation 118 of any wavelength range including, but not limited to, Vacuum Ultraviolet (VUV), e.g., 100nm to 190nm, and/or Deep Ultraviolet (DUV), e.g., 190nm to 260 nm.

In one embodiment, the target material source 102 delivers one or more target materials 104 into the chamber 106. For example, the target material source 102 may cause one or more target materials 104 to be introduced into the chamber 106 in the form of liquid jets, droplets, frozen jets, frozen droplets, or a combination of these target material forms. In another embodiment, the flow delivery parameters of the target material 104 from the target material source 102 are adjusted such that all of the material delivered by the target material source 102 is vaporized in the plasma region or some of the material passes through the plasma and is collected by the debris collector 124. In another embodiment, the debris collector 124 is positioned on the opposite side of the chamber from the target material source 102. It is noted herein that adjustment of the flow delivery parameters may facilitate stable plasma 116 generation and generate broadband radiation 118 having one or more substantially constant properties.

The target material source 102 may transport any type of target material known in the art for LSP broadband sources. For example, the target material may include, but is not limited to, Ar, Xe, Ne, and He, or a mixture of Ar, Xe, Ne, and He.

In one embodiment, the pump source 108 is configured to generate a pump beam 112 (e.g., laser radiation) that is focused by pump laser focusing optics 110. In another embodiment, the pump source 108 includes any radiation source known in the art including, but not limited to, one or more lasers. In another embodiment, the pump beam 112 includes radiation of any wavelength or range of wavelengths known in the art, including, but not limited to, Infrared (IR) radiation, Near Infrared (NIR) radiation, Ultraviolet (UV) radiation, visible radiation, or other radiation suitable for forming a plasma upon incidence on a suitable target material.

In one embodiment, the pump light focusing optics 110 focus the pump beam 112 into the chamber 106 through a pump light window 114. In another embodiment, the pump light focusing optics 110 focus the pump beam 112 into one or more target materials 104 to generate and/or maintain the plasma 116. In another embodiment, the target material 104 is vaporized and ionized by the pump beam 112 to provide a high local concentration of plasma in the chamber. In another embodiment, the pressure of the heated material ejected from the plasma will decrease rapidly outward from the plasma region. It should be noted herein that the pump light focusing optics 110 may include any optical element known in the art for directing and/or focusing radiation, including, but not limited to, a lens, mirror, prism, polarizer, grating, filter, or beam splitter.

Focusing the pump beam 112 into the target material 104 causes energy to be absorbed through the target material contained within the chamber 106 and/or one or more absorption lines of the plasma 116, thereby "pumping" the one or more target materials 104 to generate and/or maintain the plasma 116. For example, the pump light focusing optics 110 may generate and/or maintain the plasma 116 by focusing the pump beam 112 to one or more focal points within one or more target materials 104 contained within the chamber 106 to generate and/or maintain the plasma 116. It is noted herein that the LSP radiation source 100 may include one or more additional ignition sources for facilitating the generation of the plasma 116 without departing from the spirit or scope of the present invention. For example, the chamber 106 may include one or more electrodes that may initiate and/or maintain the plasma 116.

In one embodiment, the broadband radiation 118 generated by the plasma 116 exits the chamber 106 through one or more apertures 122. For example, the collection optics 120 may be configured to collect broadband radiation 118 from the plasma 116 and to guide collection of at least a portion of the broadband plasma through the one or more apertures 122. In another embodiment, the one or more apertures 122 are windowless and are located in a wall of the chamber 106. For example, the one or more apertures 122 may include, but are not limited to, holes, ports, outlets, vents, spaces, or any other opening that allows the broadband radiation 118 to exit the chamber 106 through the walls of the chamber 106 and not be transmitted through materials other than the surrounding atmosphere.

In one embodiment, the chamber 106 is fluidly coupled to a vacuum pump 126. In another embodiment, the pressure in the chamber 106 is maintained at about 1 atm. For example, the pressure in the chamber 106 may be maintained in the range of 0.1atm to 2 atm. For example, the vacuum pump 126 may remove gases (e.g., gases ejected from the plasma, buffer gases) from the chamber 106 to maintain the pressure in the chamber 106 in the range of 0.1atm to 2 atm.

In one embodiment, the set of optics 120 includes one or more optical elements known in the art configured to collect radiation (e.g., the broadband radiation 118) including, but not limited to, one or more mirrors, one or more prisms, one or more lenses, one or more diffractive optical elements, one or more parabolic mirrors, one or more elliptical mirrors, and the like. It is noted herein that the set of optics 120 may be configured to collect and/or focus broadband radiation 118 generated by the plasma 116 for one or more downstream processes including, but not limited to, imaging processes, inspection processes, metrology processes, lithography processes, and the like. In another embodiment, the set of optics 120 is protected from damage by being positioned a sufficient distance from the plasma 116. For example, the set of optics 120 may be positioned in a range from 5cm to 100cm of the plasma to avoid damage by the plasma 116.

In one embodiment, the pump light focusing optics 110 and the collection optics 120 are physically separate. It should be noted that the physical separation of the pump light focusing optics 110 and the collection optics 120 eliminates the need for cold mirrors and/or dual bandwidth reflective elliptical optics.

In one embodiment, the reflective optical surfaces of collection optics 120 in chamber 106 are protected by a buffer gas. For example, a buffer gas (e.g., an inert gas, the same material as the target material, a material different from the target material) maintains about 1atm in the chamber 106.

In one embodiment, the particular geometry of the pump laser focusing optics 110 and collection optics 120 is optimized depending on the laser power and collection etendue requirements. In another embodiment, the collection optics 120 direct the broadband radiation to the collection location 128.

In one embodiment, the pump source 108 includes one or more radiation sources. For example, the pump source 108 may include any laser system known in the art. For example, the pump source 108 may 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 another embodiment, the pump source 108 includes a laser system configured to emit Continuous Wave (CW) laser radiation. For example, the pump source 108 may include one or more CW infrared laser sources.

In another embodiment, the pump source 108 includes one or more modulated CW lasers configured to provide modulated laser light to the plasma 116. In another embodiment, the pump source 108 may include one or more pulsed lasers configured to provide pulsed laser light to the plasma 116.

In one embodiment, the pump source 108 may include one or more diode lasers. For example, the pump source 108 may include one or more diode lasers that emit radiation at wavelengths corresponding to any one or more absorption lines of the species of the target material 104 contained within the chamber 106. It should be noted that the diode laser implementing the pump source 108 may be selected such that the wavelength of the diode laser is tuned to any absorption line of any plasma (e.g., ion transition line) or plasma generation target material known in the art (e.g., highly excited neutral transition line). Thus, the selection of a given diode laser (or group of diode lasers) will depend on the type of target material contained within the chamber 106 of the system 100.

In another embodiment, the pump source 108 comprises an ion laser. For example, the pump source 108 may comprise any inert gas ion laser known in the art. For example, with argon-based plasmas, the pump source 108 for pumping argon ions may comprise an Ar + laser.

In another embodiment, the pump source 108 includes one or more frequency converted laser systems. For example, the pump source 108 may comprise a Nd: YAG or Nd: YLF laser.

In another embodiment, the pump source 108 includes one or more non-laser sources. In general, the pump source 108 may comprise any non-laser light source known in the art. For example, the pump source 108 may include any non-laser system known in the art capable of discrete or continuous emission of radiation in the infrared, visible, and/or ultraviolet portions of the electromagnetic spectrum.

In another embodiment, the pump source 108 includes two or more radiation sources. For example, the pump source 108 may include, but is not limited to, two or more lasers. For example, the pump source 108 (or several pump sources) may include multiple diode lasers. In another example, the pump source 108 may include multiple CW lasers and/or pulsed lasers. In another embodiment, each of the two or more lasers may emit laser radiation tuned to a different absorption line of the target material or plasma within the chamber 106 of the system 100.

In one embodiment, the pump source 108 generates pump radiation having a pulse spacing of 100ns to 1000 ns. In another embodiment, the pump source 108 operates at a power in a range of 3kW to 100 kW. In another embodiment, the pump source 108 comprises greater than 10,000W/cm²Peak laser intensity of (1). For example, pump source 108 may include greater than 10⁵W/cm²Peak laser intensity of (1). In another embodiment, short pulses are used (e.g.<100ns) high peak power: (>10⁸W/cm²) The laser performs ignition of one or more target materials 104 used to generate the plasma 116.

Fig. 2A illustrates a pump and collection configuration including a low NA pump and a high NA collection in accordance with one or more embodiments of the present disclosure. In one embodiment, the pump source 108, the one or more focusing optics 110, and the reflection collection optics 120 are configured such that the broadband radiation 118 has a numerical aperture that is higher than the NA of the pump radiation 112. In another embodiment, the collection optics 120 direct the broadband radiation to the collection location 128.

Fig. 2B illustrates a pump and collection configuration including a high NA pump and a low NA collection in accordance with one or more embodiments of the present disclosure. In one embodiment, the pump source 108, the one or more focusing optics 110, and the reflection collection optics 120 are configured such that the broadband radiation 118 has a numerical aperture that is lower than the NA of the pump radiation. In another embodiment, the collection optics 120 direct the broadband radiation to the collection location 128.

Fig. 3 illustrates a simplified schematic diagram of an optical characterization system 300 implementing LSP radiation source 100, in accordance with one or more embodiments of the present disclosure. In one embodiment, system 300 includes LSP radiation source 100, illumination branch 303, collection branch 305, detector 314, and controller 318 including one or more processors 320 and memory 322.

It should be noted herein that the system 300 may include any imaging, inspection, metrology, lithography, or other characterization system known in the art. In this regard, the system 300 may be configured to perform inspection, optical metrology, lithography, and/or any form of imaging on the sample 307. The sample 307 may comprise any sample known in the art including, but not limited to, a wafer, a reticle, a photomask, and the like. It should be noted that system 300 may incorporate one or more of the various embodiments of LSP radiation source 100 described in this disclosure.

In one embodiment, sample 307 is placed on stage assembly 312 to facilitate movement of sample 307. The stage assembly 312 may include any stage assembly 312 known in the art including, but not limited to, an X-Y stage, an R-theta stage, and the like. In another embodiment, stage assembly 312 is capable of adjusting the height of sample 307 during inspection or imaging to maintain focus on sample 307.

In one embodiment, illumination branch 303 is configured to direct broadband radiation 118 from LSP radiation source 100 to sample 307. Illumination branch 303 may include any number and type of optical components known in the art. In one embodiment, illumination branch 303 includes one or more optical elements 302, a beam splitter 304, and an objective lens 306. In this regard, the illumination branch 303 may be configured to focus the broadband radiation 118 from the LSP radiation source 100 onto the surface of the sample 307. The one or more optical elements 302 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 splitters, and the like. It should be noted herein that the collection location 128 may include, but is not limited to, one or more of the optical element 302, the beam splitter 304, or the objective 306.

In one embodiment, the system 300 includes a collection leg 305 configured to collect light reflected, scattered, diffracted, and/or emitted from the sample 307. In another embodiment, the collection leg 305 can direct and/or focus light from the sample 307 to the sensor 316 of the detector assembly 314. It should be noted that the sensor 316 and detector assembly 314 may include any sensor and detector assembly known in the art. The sensor 316 may include, but is not limited to, a CCD sensor or a CCD-TDI sensor. Further, the sensor 316 may include, but is not limited to, a line sensor or an electronic impact line sensor.

In one embodiment, detector assembly 314 is communicatively coupled to a controller 318 that includes one or more processors 320 and memory 322. For example, the one or more processors 320 may be communicatively coupled to the memory 322, wherein the one or more processors 320 are configured to execute a set of program instructions stored on the memory 322. In one embodiment, the one or more processors 320 are configured to analyze the output of the detector assembly 314. In one embodiment, the set of program instructions is configured to cause the one or more processors 320 to analyze one or more characteristics of the sample 307. In another embodiment, the set of program instructions is configured to cause the one or more processors 320 to modify one or more characteristics of the system 300 to maintain focus on the sample 307 and/or the sensor 316. For example, the one or more processors 320 may be configured to adjust the objective 306 or the one or more optical elements 302 to focus the broadband radiation 118 from the LSP radiation source 100 onto the surface of the sample 307. By way of another example, the one or more processors 320 may be configured to adjust the objective 306 and/or the one or more optical elements 310 to collect illumination from the surface of the sample 307 and focus the collected illumination on the sensor 316.

It should be noted that the system 300 may be configured in any optical configuration known in the art including, but not limited to, dark field configurations, bright field orientations, and the like.

It should be noted herein that one or more components of the system 100 may be communicatively coupled to various other components of the system 100 in any manner known in the art. For example, LSP radiation source 100, detector assembly 314, controller 318, and one or more processors 320 can be communicatively coupled to each other and to other components via wired (e.g., copper wires, fiber optic cables, and the like) or wireless connections (e.g., RF coupling, IR coupling, data network communications (e.g., WiFi, WiMax, Bluetooth, and the like)).

Additional details of various embodiments of optical characterization system 300 are described in each of the following: us patent application 13/554,954 entitled "Wafer Inspection System (Wafer Inspection System)" filed on 7/9/2012, us patent application 2009/0180176 entitled "Split Field Inspection System Using Small Catadioptric Objectives" published on 7/16/2009, us patent application 2007/0002465 entitled "Beam Delivery System for Laser Dark Field Illumination in Catadioptric Optical System (Beam Delivery System for Laser Dark Field Illumination-Optical System)" published on 1/4/2007, us patent application 2007/0002465 entitled "Wide-Range Zoom UV microscopy Imaging System with Wide-Range Zoom Capability" published on 12/7/1999, us patent application 5,999,310 entitled "Ultra-Wide-band UV microscopy Imaging System (Ultra-Wide-view microscopy Imaging System) published on 5,999,310" published on 12/7/2009, and us patent application 3528 entitled "two-dimensional Imaging System Using Laser Imaging System" published on Surface Inspection System with Wide-Range Zoom Capability "published on 3/84 (cross Field Inspection System)" published on 7/2009 Us patent 7,525,649 to Laser Line Illumination with Two dimensional imaging, "us published patent application 2013/0114085 by Wang (Wang) et al, entitled" Dynamically Adjustable Semiconductor Metrology System "(Dynamically Adjustable Semiconductor Metrology System)" published on 2013, 5,9, us patent 5,608,526 by picomaka-kele et al, entitled "Focused Beam ellipsometry Method and System" (Focused Beam spectroscopic ellipsometry Method and System) "published on 1997, 3, 4, 2001, us patent 5,608,526 by rosenwaige (Rosencwaig), et al, entitled" apparatus for Analyzing multilayer Thin Film Stacks on Semiconductors "(apparatus for Analyzing multilayer-Layer Stacks), published on 2001, 10, 2, 6,297,880, each of which is incorporated herein by reference in its entirety.

The one or more processors 320 of the present disclosure may include any one or more processing elements known in the art. To this extent, the one or more processors 320 can include any microprocessor-type device configured to execute software algorithms and/or instructions. In one embodiment, the one or more processors 320 may be comprised of a desktop computer, a main computer system, a workstation, an image computer, a parallel processor, or other computer system (e.g., a network computer) configured to execute programs configured to operate system 300 and/or LSP radiation source 100, as described in this disclosure. It should be recognized that the steps described in this disclosure may be implemented 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 components that execute program instructions from the non-transitory memory medium 322. Moreover, different subsystems of the various disclosed systems may include processors or logic elements adapted to implement at least part of the steps described in this disclosure. Accordingly, the above description should not be construed as limiting the invention but merely as illustrative.

Memory medium 322 may include any storage medium known in the art suitable for storing program instructions executable by the associated processor(s) 320. For example, memory medium 322 may include a non-transitory memory medium. For example, the memory medium 322 may include, but is not limited to, read-only memory, random-access memory, magnetic or optical memory devices (e.g., diskette), magnetic tape, solid-state drive, etc. In another embodiment, memory 322 is configured to store one or more results and/or outputs of the various steps described herein. It should be further noted that the memory 322 may be housed in a common controller housing with the one or more processors 320. In alternative embodiments, memory 322 may be remotely located relative to the physical location of processor 320. For example, the one or more processors 320 may access a remote memory (e.g., a server), may be accessed over a network (e.g., the internet, an intranet, etc.). In another embodiment, the memory medium 322 holds program instructions for causing the one or more processors 320 to perform the various steps described in this disclosure.

In one embodiment, the system 300 may include a user interface (not shown). In one embodiment, the user interface is communicatively coupled to the one or more processors 320. In another embodiment, a user interface device may be used to accept selections and/or instructions from a user. In some embodiments, which will be further described herein, a display may be used to display data to a user. The user may, in turn, input selections and/or instructions (e.g., selection, sizing, and/or position of the filter box) in response to data displayed to the user via the display device.

The user interface device may comprise any user interface known in the art. For example, the user interface may include, but is not limited to, a keyboard, a keypad, a touch screen, a lever, a knob, a wheel, a trackball, a switch, a dial, a slider, a scroll bar, a slider, a handle, a touch pad, a pedal, a steering wheel, a joystick, a panel-mounted input device, and the like. In the case of a touch screen interface device, those skilled in the art will recognize that a wide variety of touch screen interface devices may be suitable for implementation in the present invention. For example, the display device may be integrated with a touch screen interface such as, but not limited to, a capacitive touch screen, a resistive touch screen, a surface acoustic wave based touch screen, an infrared based touch screen, or the like. In general, any touch screen interface capable of being integrated with the display portion of a display device is suitable for implementation in the present invention.

The display device may comprise any display device known in the art. In one embodiment, the display device may include, but is not limited to, a Liquid Crystal Display (LCD), an Organic Light Emitting Diode (OLED) based display, or a CRT display. One skilled in the art will recognize that a variety of display devices may be suitable for implementation in the present disclosure and that the particular selection of a display device may depend on a variety of factors including, but not limited to, apparent size, cost, and the like. In general, any display device capable of being integrated with a user interface device (e.g., touchscreen, panel mount interface, keyboard, mouse, touchpad, and the like) is suitable for implementation in the present invention.

In some embodiments, the LSP radiation sources 100 and systems 300 described herein may be configured as "stand-alone tools" or tools that are not physically coupled to a processing tool. In other embodiments, such an inspection or metrology system may be coupled to a tool (not shown) through a transmission medium that may include wired and/or wireless portions. The processing tool may comprise any processing tool known in the art, such as a photolithography tool, an etching tool, a deposition tool, a polishing tool, an electroplating tool, a cleaning tool, or an ion implantation tool. The results of the inspections or measurements performed by the systems described herein may be used to alter parameters of a process or process tool using feedback control techniques, feed forward control techniques, and/or in-situ control techniques. The parameters of the process or treatment process may be altered manually or automatically.

Embodiments of LSP radiation source 100 and system 300 may be further configured as described herein. In addition, LSP radiation source 100 and system 300 may be configured to perform any other step(s) of method embodiment(s) described herein.

Fig. 4 illustrates a flow diagram depicting a method 400 for generating broadband radiation 118 in accordance with one or more embodiments of the present disclosure. It should be noted herein that the steps of method 400 may be performed in whole or in part by LSP radiation source 100. However, it should be further appreciated that method 400 is not limited to LSP radiation source 100, as additional or alternative system level embodiments may implement all or a portion of the steps of method 400.

In step 402, a stream of target material 104 is conveyed through a plasma formation region of the chamber 106. In one embodiment, the target material source 102 introduces one or more target materials 104 into the chamber 106 in the form of liquid jets, droplets, frozen jets, frozen droplets, or a combination of these target material forms. For example, the target material source 102 may deliver one or more of argon, xenon, neon, or helium in one or more of a solid or liquid state into the chamber 106 to generate and/or maintain a plasma. For example, the target material source 102 may be configured to deliver a flow of target material through the plasma formation region at a velocity between 10m/s and 300 m/s. By way of another example, the target material source 102 may be configured to deliver a stream of target material having a diameter between 10 μm and 2000 μm through the plasma formation region.

In step 404, debris is collected by a debris collector. For example, the plasma formation target material 104 from step 402 that is not consumed by the plasma 116 is collected by the debris collector 124. In one embodiment, the flow delivery parameters are adjusted such that all material delivered by the target material source 102 is vaporized in the plasma region or some material passes through the plasma and is collected by the debris collector 124. It is noted herein that adjustment of the flow delivery parameters may facilitate stable plasma 116 generation and generate broadband radiation 118 having one or more substantially constant properties.

In step 406, the pump source 108 generates pump radiation 112. In one embodiment, the pump source 108 generates pump radiation 112 that is focused by pump light focusing optics 110 into the chamber 106. For example, the pump source 108 may include one or more lasers to generate the pump radiation 112 directed into the chamber 106. As another example, one or more non-laser sources may generate the pump radiation 112 directed into the chamber 106.

In step 408, the pump radiation 112 is focused into a plasma formation region of the chamber 106 to generate broadband radiation 118 via formation of a plasma 116 by exciting the target material 104 within the plasma formation region of the chamber 106. For example, the pump source 108 may direct pump radiation 112 into the chamber 106 to generate the plasma 116. In another embodiment, LSP radiation source 100 generates radiation that includes, but is not limited to, broadband radiation 118. For example, the LSP radiation source 100 may generate broadband radiation 118 in the range of Vacuum Ultraviolet (VUV) (100nm to 190nm) and Deep Ultraviolet (DUV) (190nm to 260 nm). It should be noted herein that the chamber 106 may include one or more additional ignition sources (e.g., electrodes) configured to initiate and/or maintain the plasma 116.

In step 410, a portion of the broadband radiation 118 is collected from the plasma 116 and the portion of the broadband radiation 118 is transported through the windowless aperture 122 in the wall of the chamber 106 to one or more optical elements outside the chamber 106 at the collection location 128. For example, the broadband radiation 118 generated by the plasma 116 in the chamber 106 may be collected by the collection optics 120 and directed through the aperture 122 to a collection location 128 where the external optical elements receive the broadband radiation 118.

It will be appreciated by those skilled in the art that for conceptual clarity means, components (e.g., operations), devices, objects, and their accompanying discussion described herein are used as examples and that various configuration modifications may be considered. Thus, as used herein, the specific examples set forth and the accompanying discussion are intended to be representative of their more general categories. In general, use of any particular paradigm is intended to indicate its class, and no particular component (e.g., operation), device, or object is to be considered limiting.

Those skilled in the art will appreciate that there are a variety of vehicles by which processes and/or systems and/or other technologies described herein can be effected (e.g., hardware, software, and/or firmware), and that the preferred vehicle will vary with the context in which the processes and/or systems and/or other technologies are deployed. For example, if the implementer determines that speed and accuracy are paramount, the implementer may opt for a hardware and/or firmware-based vehicle; or, if flexibility is paramount, the implementer may opt for a software-based implementation; alternatively, the implementer may opt for some combination of hardware, software, and/or firmware. Thus, there are several possible vehicles by which the processes and/or devices and/or other techniques described herein can be accomplished, any of which is not inherently superior to others in that utilizing any vehicle is a choice depending on the context in which the vehicle will be deployed and the particular concerns (e.g., speed, flexibility, or predictability) of the implementer, any of which may vary.

The previous description is presented to enable any person skilled in the art to make and use the invention as provided in the context of a particular application and its requirements. As used herein, directional terms such as "top," "bottom," "on …," "under …," "upper," "upward," "lower," "below," and "downward" are intended to provide relative positions for the purposes of description and are not intended to specify an absolute frame of reference. Various modifications to the described embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

With respect to substantially any plural and/or singular terms used 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. For purposes of clarity, various singular/plural permutations are not explicitly set forth herein.

All methods described herein may include storing results of one or more steps of a method embodiment in memory. The results may include any of the results described herein and may be stored in any manner known in the art. The memory may comprise any memory described herein or any other suitable storage medium known in the art. After the results have been stored, the results may be accessed in memory and used by any of the method or system embodiments described herein, formatted for display to a user, used by another software module, method, or system, and so forth. Further, the results may be "permanent," "semi-permanent," "temporary," or stored for a period of time. For example, the memory may be Random Access Memory (RAM), and the results do not necessarily persist indefinitely in the memory.

It is further contemplated that each of the embodiments of the above-described methods may include any other step(s) of any other method(s) described herein. Additionally, each of the embodiments of the method described above may be performed by any of the systems described herein.

Embodiments of the present invention are directed to a buoyancy-driven closed recirculation gas loop for facilitating rapid gas flow therethrough in an LSP radiation source. Advantageously, the LSP radiation source 100 of the present invention may include fewer mechanical actuation components than previous methods. Accordingly, the LSP radiation source 100 of the present invention may generate less noise, require less gas volume, and require lower maintenance costs and safety management.

The objects described herein sometimes illustrate different components being housed within or connected to 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. Conceptually, any configuration of components to achieve the same functionality is effectively "associated" to achieve the desired functionality. 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," etc.). 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, even when the same claim contains 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 generally be interpreted to mean "at least one" or "one or more"), 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 such recitation; the use of definite articles for introducing claim recitations is equally effective. 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). Moreover, in such examples using a convention analogous to "at least one of A, B and C, etc." this construction is generally intended in the sense one of ordinary 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, etc.). In such examples using a convention analogous to "at least one of A, B or C, etc." this construction is generally intended in the sense one of ordinary skill in the art understands the convention (e.g., "a system having at least one of A, B or C" shall include, but not be limited to, systems having 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, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative items, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the items, either of the items, or both items. For example, the phrase "a or B" should be understood to include the possibility of "a" or "B" or "a and B".

It is believed that the present invention 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 forms described are merely illustrative, and the appended claims are intended to cover and include such changes. Furthermore, it is to be understood that the invention is defined by the appended claims.