System, method and apparatus for target material debris cleaning of EUV vessel and EUV collector

Abstract

To provide a system and a method for generating hydrogen radicals H* in situ in an EUV vessel, proximate to target material debris deposits.SOLUTION: A system and a method for removing target material debris deposits simultaneously upon generating EUV light include generating hydrogen radicals in situ in the EUV vessel, proximate to the target material debris deposits and volatilizing the target material debris deposits and purging the volatilized target material debris deposits from the EUV vessel without the need of oxygen-containing species in the EUV vessel.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS [1] This application claims the benefit of U.S. Utility Application No. 15 / 003,385, filed Jan. 21, 2016, entitled “SYSTEM, METHOD AND APPARATUS FOR TARGET MATERIAL DEBRIS CLEANING OF EUV VESSEL AND EUV COLLECTOR,” which is incorporated herein by reference in its entirety. [Background technology]

[0002] [2] Extreme ultraviolet (EUV) light is used in applications such as extreme ultraviolet lithography (EUVL).

[0003] [3] Extreme ultraviolet (EUV) light can be generated using an EUV source, where a target material is irradiated by a high-powered laser source. Irradiation of the target material by the laser source leads to the generation of a plasma that emits EUV light.

[0004] [4] An EUV collector located within the EUV vessel collects and focuses the EUV light emitted by the plasma. The collected EUV light is directed from the EUV vessel into an EUV consumer system, such as an extreme ultraviolet lithography system (EUVL).

[0005] [5] A significant portion of the target material is dispersed around the EUV vessel as target material debris when the target material is irradiated by the high power laser source. The target material debris deposits on various interior surfaces within the EUV collector and EUV vessel. Target material debris deposition on the EUV collector reduces the collection performance of the EUV collector. Target material debris deposition on the interior surfaces of the EUV vessel may eventually flake off the interior surfaces and come to rest on the EUV collector, further reducing the collection performance of the EUV collector.

[0006] [6] In these circumstances, various embodiments arise. Summary of the Invention

[0007] [7] In general, the present invention involves the generation of hydrogen radicals H in situ in an EUV chamber in close proximity to a target material debris deposition. * These needs are met by providing a system and method for generating EUV light. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a computer readable medium, or a device. In situ cleaning provides the ability to clean the EUV collector and EUV vessel at the same time that EUV light is generated. In situ cleaning allows for the EUV generation operation to not have to be interrupted to clean the EUV collector and EUV vessel. Several embodiments of the present invention are described below.

[0008] [8] One embodiment provides a system for generating EUV light and simultaneously removing a target material debris deposit, comprising generating hydrogen radicals in situ in an EUV vessel proximate to the target material debris deposit, volatilizing the target material debris deposit, and purging the volatilized target material debris deposit from the EUV vessel without the need for oxygen-containing species in the EUV vessel.

[0009] [9] Another embodiment provides an EUV light source including an EUV vessel including an EUV vessel purge gas inlet coupled to a purge gas source capable of introducing a quantity of purge gas into the EUV vessel. An EUV collector is disposed within the EUV vessel. The EUV collector includes a reflective surface. A target material source is capable of introducing a quantity of target material into the EUV vessel. A first portion of the quantity of target material is disposed on at least a portion of the reflective surface of the EUV collector as a first target material debris deposit. A first hydrogen radical source is disposed within the EUV vessel. The first hydrogen radical source includes a first hydrogen radical source outlet disposed proximate to the reflective surface of the EUV collector. The first hydrogen radical source also includes a first hydrogen source inlet coupled to a hydrogen source, a first hydrogen source electrode coupled to a first signal source, and a second hydrogen source electrode coupled to a second signal source. The first hydrogen radical source is capable of generating a first quantity of hydrogen radicals and introducing the first quantity of hydrogen radicals from the first hydrogen radical source outlet. The first quantity of hydrogen radicals can combine with the first target material debris pile to form a first quantity of a volatile compound that contains at least a portion of the first target material debris pile. The EUV container purge outlet is included in the EUV container and can exit the first quantity of the volatile compound from the EUV container.

[0010]

[10] The hydrogen radical source may include a hydrogen plasma chamber, such as a capacitively or inductively coupled hydrogen plasma chamber. One of the electrodes used to generate the hydrogen radicals may be part of the conductive layer of the EUV collector. The hydrogen radical source outlet may be located around the periphery of the EUV collector or near the central aperture of the EUV collector. The hydrogen radical source may be located near one or more baffles within the EUV vessel.

[0011]

[11] The hydrogen radicals are generated in close proximity to the target material debris deposit and therefore do not require oxygen-containing species to extend the time before the hydrogen radicals recombine to form hydrogen gas, thus preventing oxygen-containing species from entering the EUV chamber.

[0012]

[12] Another embodiment provides a method of cleaning a target material debris deposit in an EUV light source while simultaneously generating EUV light in the EUV light source. The method includes generating a quantity of hydrogen radicals in an EUV vessel of the EUV light source and outputting the generated quantity of hydrogen radicals proximate to a target material deposit on an interior surface of the EUV vessel. A first quantity of a volatile compound is formed that contains at least a portion of a first portion of the target material deposit. A sufficient amount of purge gas is introduced into the EUV vessel and the first quantity of the volatile compound is purged from the EUV vessel through an EUV vessel purge outlet.

[0013]

[13] Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

[0014]

[14] The present invention will be readily understood from the following detailed description taken in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0015] [Figure 1A]

[15] FIG. 1 is a simplified schematic diagram of a laser-produced plasma EUV light source according to embodiments of the disclosed subject matter. [Figure 1B]

[16] FIG. 1 illustrates a central vessel baffle assembly in an EUV vessel according to embodiments of the disclosed subject matter. [Figure 1C]

[17] FIG. 1 is a schematic diagram of an EUV collector including target material debris deposition according to embodiments of the disclosed subject matter. [Figure 1D]

[18] FIG. 1 is a schematic diagram of a portion of a baffle assembly according to embodiments of the disclosed subject matter. [Diagram 2] FIG. 1 is a simplified schematic diagram of an EUV light source including one or more in situ hydrogen radical sources according to embodiments of the disclosed subject matter. [Figure 3A]

[20] FIG. 2 is a detailed cross-sectional view of a portion of a collector and an in-situ hydrogen radical source according to embodiments of the disclosed subject matter. [Figure 3B]

[21] FIG. 1 is a simplified schematic diagram of a cross-sectional view of a collector and an in-situ hydrogen radical source according to embodiments of the disclosed subject matter. [Figure 4]

[22] FIG. 1 is a simplified schematic diagram of a cross-sectional view of a collector and an alternative in situ hydrogen radical source according to embodiments of the disclosed subject matter. [Diagram 5]

[23] FIG. 1 is a simplified diagram of a collector having an in situ hydrogen radical source substantially surrounding the periphery of the collector, in accordance with embodiments of the disclosed subject matter. [Figure 6]

[24] FIG. 1 is a simplified diagram of a collector having multiple in situ hydrogen radical sources substantially evenly distributed and positioned around the periphery of the collector, in accordance with embodiments of the disclosed subject matter. [Figure 7]

[25] FIG. 1 is a simplified schematic diagram of a cross-sectional view of a collector and multiple in situ hydrogen radical sources according to embodiments of the disclosed subject matter. [Figure 8]

[26] FIG. 1 is a simplified schematic side view of an inductive hydrogen radical generator according to embodiments of the disclosed subject matter. [Figure 9]

[27] FIG. 1 is a simplified schematic top view of an inductive hydrogen radical generator according to embodiments of the disclosed subject matter. [Figure 10]

[28] FIG. 1 is a simplified schematic side view of an inductive hydrogen radical generator according to embodiments of the disclosed subject matter. [Figure 11]

[29] FIG. 1 is a simplified schematic side view of a capacitive hydrogen radical generator according to embodiments of the disclosed subject matter. [Figure 12]

[30] FIG. 1 is a simplified schematic side view of a capacitive hydrogen radical generator according to embodiments of the disclosed subject matter. [Figure 13]

[31] FIG. 1 is a simplified schematic side view of an EUV vessel including a volumetric hydrogen radical source disposed in or near a baffle, in accordance with embodiments of the disclosed subject matter. [Figure 14]

[32] FIG. 13 is a flow chart diagram illustrating method operations performed in generating hydrogen radicals in situ within an EUV vessel according to embodiments of the disclosed subject matter. [Figure 15]

[33] FIG. 1 is a flow chart diagram illustrating method operations performed in generating EUV light while simultaneously removing target material debris buildup within an EUV vessel according to embodiments of the disclosed subject matter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016]

[34] Next, several exemplary embodiments for removing target material debris from an EUV vessel using an in-situ hydrogen radical generator will be described. It will be apparent to one skilled in the art that the present invention may be practiced without some or all of the specific details set forth herein.

[0017]

[35] Several different types of target materials can be used to generate the EUV emitting plasma. In one embodiment, tin and / or tin compounds are used. Some examples of tin-containing target materials are pure tin, SnBr 4 , SnBr 2 , SnH 4 tin alloys including one or more of tin-gallium alloys, tin-indium alloys, tin-indium-gallium alloys, and combinations thereof.

[0018]

[36] Unfortunately, tin-containing debris can contaminate many of the internal surfaces of the EUV vessel, most specifically the EUV collector. Several techniques have been tried to remove the tin-containing debris. One technique involves injecting hydrogen into the EUV vessel to remove the deposited tin, called SnH2O3, which can then be purged from the EUV vessel. 4 Unfortunately, simple hydrogen injection results in a relatively slow conversion of the deposited tin to volatile tin compounds.

[0019]

[37] In one embodiment, H + and / or H - Hydrogen radical containing ions can be generated using a microwave hydrogen radical generator located outside the EUV vessel. Unfortunately, by the time the hydrogen radicals reach the inside of the EUV vessel, most of the hydrogen radicals have combined to form H 2 Hydrogen gas was formed.

[0020]

[38] In one approach to ensure the delivery of a larger number of hydrogen radicals, oxygen, or more specifically water vapor, can be injected together with the hydrogen radicals, so that the number of hydrogen radicals arriving in the EUV vessel is sufficient to carry out the desired combination with the deposited tin to form volatile tin compounds. However, oxygen and / or water vapor cause problems in the EUV generation process, so the injection of oxygen or water vapor into the EUV vessel requires that the EUV generation process carried out in the EUV vessel must be completed in the presence of oxygen or water vapor.

[0021]

[39] One embodiment disclosed herein uses a hydrogen radical source located in situ within an EUV chamber to generate H + and / or H - The objective of the present invention is to increase the conversion of the deposited tin to volatile tin compounds by generating hydrogen radical containing ions. The hydrogen radical source will generate hydrogen radicals in high concentration. The hydrogen radical source can be located in close proximity to the EUV collector such that the outlet of the hydrogen radical source delivers hydrogen radicals directly to the EUV collector. The outlet of the hydrogen radical source can be located at one or more locations around the periphery of the EUV collector and / or near the center of the EUV collector.

[0022]

[40] The hydrogen radical source can be a single hydrogen radical source or multiple hydrogen radical sources. In one embodiment, the hydrogen radical source is in the form of an annular shaped plasma vessel located near the periphery of the EUV collector. In another embodiment, the hydrogen radical source is in the form of multiple hydrogen radical sources located near the periphery of the EUV collector and / or near the center of the EUV collector.

[0023]

[41] One or more additional hydrogen radical sources may also be included within the EUV vessel. For example, an additional hydrogen radical source may be included near the vanes in the outlet portion of the EUV vessel to provide hydrogen radicals near the vanes to convert tin deposited on the vanes to volatile tin compounds.

[0024]

[42] Generating hydrogen radicals within the EUV vessel ensures that a sufficient number of hydrogen radicals are available to convert the deposited tin to volatile tin compounds simultaneously with the use of the EUV vessel to generate EUV. As a result, the EUV source can be operated for a significantly longer period of time before the deposited tin interferes with the generation of EUV. As long as a sufficient number of hydrogen radicals can be generated, the deposited tin can be substantially removed and maintained at essentially zero levels to mitigate the need for disassembly and cleaning of the EUV vessel as a result of excessive tin deposition.

[0025]

[43] Figure 1A is a simplified schematic diagram of a laser-produced plasma EUV light source 20 according to embodiments of the disclosed subject matter. The LPP light source 20 includes a light pulse generation system 22 for generating a train of light pulses and delivering the light pulses into an EUV vessel 26. Each light pulse 23 travels from the light pulse generation system 22 along a beam path 21 inside a beam delivery system 25. The light pulses 23 are focused within the EUV vessel 26 to illuminate and / or irradiate selected target droplets at an irradiation region 28.

[0026]

[44] Suitable lasers for use in the optical pulse generating system 22 shown in FIG. 1 include pulsed laser devices, such as pulsed gas discharge CO lasers operating at relatively high powers, such as about 10 kW or more, and high pulse repetition rates, such as about 10 kHz or more, producing radiation at about 9.3 μm or about 10.6 μm with DC or RF excitation. 2 In one particular embodiment, the laser in the optical pulse generating system 22 has a MOPA configuration with multiple amplification stages, e.g., an axial RF pumped CO laser with seed pulses initiated by a Q-switched master oscillator (MO) with low energy and high repetition rate, capable of operation at 100 kHz. 2 The laser pulse from the MO can then be amplified, shaped and focused before reaching the illumination region 28.

[0027]

[45] Continuous pumping CO 2 The amplifiers can be used in the optical pulse generation system 22. For example, a suitable CO amplifier having one oscillator and multiple amplifiers (e.g., O-PA1-PA2... configuration) can be used. 2 The laser device is disclosed in commonly owned U.S. Patent No. 7,439,530, entitled "LPP EUV LIGHT SOURCE DRIVE LASER SYSTEM," filed on June 29, 2005, and issued on October 21, 2008, the entire contents of which are incorporated herein by reference.

[0028]

[46] Alternatively, the laser in the optical pulse generating system 22 can be configured as a so-called "self-targeting" laser system, in which the surface of the target material in the laser waist acts as one mirror of the optical cavity. In some "self-targeting" arrangements, a master oscillator may not be necessary. Self-targeting laser systems are disclosed and claimed in commonly owned U.S. Patent No. 7,491,954, filed October 26, 2005, and issued February 17, 2009, entitled "DRIVE LASER DELIVERY SYSTEMS FOR EUV LIGHT SOURCE," the entire contents of which are incorporated herein by reference.

[0029]

[47] Depending on the application, other types of lasers may also be suitable for use in the optical pulse generating system 22, such as, for example, excimer or molecular fluorine lasers operating at high power and high pulse repetition rates. Other examples may be suitable, including solid-state lasers with active media in the form of a fiber, rod, or disk, excimer laser systems in a MOPA configuration, such as those shown in commonly owned U.S. Patent Nos. 6,625,191, 6,549,551, and 6,567,450, the entire contents of which are incorporated herein by reference, excimer lasers with one or more chambers, such as an oscillator chamber and one or more amplifier chambers (with multiple amplifier chambers in parallel or series), master oscillator / power oscillator (MOPO) configurations, master oscillator / power ring amplifier (MOPRA) configurations, power oscillator / power amplifier (POPA) configurations, or solid-state lasers seeding one or more excimer or molecular fluorine amplifier or oscillator chambers. Other light source designs are possible.

[0030]

[48] ​​Referring again to FIG. 1A, the EUV light source 20 may also include a target material delivery system 24 for delivering portions (e.g., droplets) of the target material into the EUV vessel 26 to an irradiation region 28 where the droplets 102A, 102B interact with one or more light pulses 23, e.g., one or more pre-pulses followed by one or more irradiation pulses, to ultimately generate a plasma and a corresponding emission of EUV light 34. Unused or unirradiated droplets 102C are collected in a target material catch 200. The target material may include, but is not necessarily limited to, materials including tin, lithium, xenon, and the like, or combinations thereof. For example, the EUV emitting elements, such as tin, lithium, xenon, and the like, may be in the form of liquid droplets and / or solid particles contained within the liquid droplets 102A, 102B, or in other forms as described elsewhere herein.

[0031]

[49] For example, elemental tin is known as pure tin, SnBr 4 , SnBr 2 , SnH 4 The target material may be used as a tin compound such as tin, tin-gallium alloy, tin-indium alloy, tin-indium-gallium alloy, or a combination thereof. Depending on the material used, the target material may be heated to room temperature or near room temperature (e.g., tin alloy, SnBr 4 ), high temperatures (e.g., pure tin), or below room temperature (e.g., SnH 4 ) and, in some cases, SnBr 4 Further details regarding the use of these materials in LPP EUV light sources are provided in commonly owned U.S. Patent No. 7,465,946, entitled "ALTERNATIVE FUELS FOR EUV LIGHT SOURCE," filed April 17, 2006, and issued December 16, 2008, the contents of which are incorporated herein by reference.

[0032]

[50] Still referring to FIG. 1A, EUV light source 20 includes EUV collector 30. EUV collector 30 is a near-normal incidence EUV collector having a reflective surface in the form of a prolate spheroid (i.e., an ellipse rotated about its long axis). The actual shape and geometry may of course vary depending on the size of the chamber and the location of the focal spot. EUV collector 30, in one or more embodiments, may include a graded multi-layer coating. The graded multi-layer coating may include alternating layers of molybdenum and silicon, and, optionally, one or more high temperature diffusion barrier layers, smoothing layers, capping layers, and / or etch stop layers.

[0033]

[51] The EUV collector 30 also includes an aperture 32 that allows the light pulses 23 generated by the light pulse generating system 22 to pass through to the illumination region 28. The EUV collector 30 may be a prolate spheroid mirror having a first focal point 31 at or near the illumination region 28 and an intermediate focal point 40. The EUV light 34 is output from the EUV light source 20 at or near the intermediate focal point 40 and input to a downstream device 42 that uses the EUV light 34. By way of example, the downstream device 42 that receives the EUV light 34 may be an integrated circuit lithography tool (e.g., a scanner).

[0034]

[52] It should be appreciated that other optical components can be used in place of a prolate spheroid mirror, e.g., EUV collector 30, to collect and direct EUV light 34 to intermediate focus 40 for subsequent delivery to a device that uses the EUV light. By way of example, EUV collector 30 can be a parabola rotated about its long axis. Alternatively, EUV collector 30 can be configured to deliver a beam having a ring-shaped cross section to intermediate focus 40 (see, e.g., commonly owned U.S. Patent No. 7,843,632, filed Aug. 16, 2006, and issued Nov. 30, 2010, entitled "EUV OPTICS," the contents of which are incorporated herein by reference).

[0035]

[53] The EUV light source 20 may also include an EUV controller 60. The EUV controller 60 may include an ignition control system 65 for activating one or more lamps and / or laser devices in the light pulse generating system 22 to thereby generate light pulses 23 for delivery to the chamber 26.

[0036]

[54] The EUV light source 20 may also include a target material position detection system including one or more target material imagers 70. The target material imager 70 may capture images using a CCD or other imaging technology and / or backlight strobe illumination and / or light curtains that provide an output indicative of the position and / or timing of one or more target material droplets 102A, 102B relative to the illumination region 28. The imager 70 is coupled to a target material position detection feedback system 62 to which it outputs target material position and timing data. The target material position detection feedback system 62 may calculate the position and trajectory of the target material, from which a target material position error may be calculated. The target material position error may be calculated for each portion of the target material or on an average basis (e.g., for each droplet or for the average droplet data). The target material position error may then be provided as an input to the EUV controller 60. The EUV controller 60 can provide position, orientation, and / or timing correction signals to the light pulse generating system 22 to control the source timing circuitry and / or control the beam position shaping system to change the trajectory and / or focusing power or focus of the light pulses 23 delivered to the irradiation region 28 within the chamber 26.

[0037]

[55] EUV light source 20 may also include one or more EUV metrology instruments for measuring various characteristics of the EUV light generated by light source 20. These characteristics may include, for example, intensity (e.g., total intensity or intensity within a particular spectral band), spectral bandwidth, polarization, beam position, pointing, etc. In the case of EUV light source 20, the instrument(s) may be configured to operate while a downstream tool, e.g., a photolithography scanner, is online, e.g., by sampling a portion of the EUV output using a pick-off mirror or by sampling “uncollected” EUV light, and / or may operate while a downstream tool, e.g., a photolithography scanner, is offline, e.g., by measuring the entire EUV output of EUV light source 20.

[0038]

[56] The EUV light source 20 may also include a target material control system 90 operable in response to signals from the EUV controller 60 (which, in some embodiments, may include the target material position error described above or some quantity derived therefrom) to, for example, alter the release point of the target material from the target material dispenser 92 and / or alter the timing of target material formation to compensate for position errors in the target material droplets 102A, 102B reaching the desired irradiation area 28 and / or to synchronize the generation of the target material droplets 102A, 102B with the light pulse generation system 22.

[0039]

[57] Additional details and alternatives for the EUV light source 20 are also described in commonly owned U.S. Patent No. 8,575,575, entitled "System, Method and Apparatus for Laser Produced Plasma Extreme Ultraviolet Chamber with Hot Walls and Cold Collector Mirror," filed March 16, 2010, issued November 5, 2013, and incorporated herein by reference in its entirety. U.S. Patent No. 8,575,575 provides examples in which the EUV collector 30 and other internal surfaces, such as the vanes, are cooled to a temperature below the melting point of the tin deposit formed on the surface of the EUV collector, since in some examples the tin deposit in solid form is more easily converted to a volatile tin compound.

[0040]

[58] Additional details and alternative examples of the EUV light source 20 are also described in commonly owned U.S. Patent No. 8,653,491, entitled "System, Method and Apparatus for Aligning and Synchronizing Target Material for Optimum Extreme Ultraviolet Light Output," filed March 16, 2010, issued February 18, 2014, and incorporated herein by reference in its entirety. U.S. Patent No. 8,653,491 provides examples for more precisely targeting the target material to improve the amount of EUV emitting plasma.

[0041]

[59] FIG. 1B illustrates a central vessel baffle assembly 150 in an EUV vessel 26 according to embodiments of the disclosed subject matter. The baffle assembly 150 is located in a central vessel region 155′ of the EUV vessel 26. The secondary region 155 of the EUV vessel 26 is divided into two parts, a central vessel region 155′ and a rear vessel region 155″. The central vessel region 155′ starts from the irradiation region 28 and extends towards the outlet 40A of the EUV vessel 26. The rear vessel region 155″ extends between the central vessel region 155′ and the outlet 40A of the EUV vessel 26. The central vessel region 155′ and the rear vessel region 155″ do not have a specific length, and thus the central vessel region 155′ can include substantially all of the secondary region 155 of the EUV vessel 26 in some embodiments.

[0042]

[60] The baffle assembly 150 includes a series of passages and structures that receive, decelerate, and capture a portion of the particulates 153 created when the target material is irradiated at the irradiation region 28. The baffle assembly 150 may be formed from a series of vanes or other structures and porous materials that extend from the irradiation region 28 and the EUV collector 30 to the location of the intermediate focus 40 or any portion of the secondary region 155 of the EUV vessel 26. Although the baffle assembly 150 may extend from the irradiation region 28 and the EUV collector 30 to the intermediate focus 40, the baffle assembly does not prevent or otherwise impede the passage of the EUV light 34 from the EUV collector 30 through the three-dimensional cone-shaped transmission region 152 to the intermediate focus 40.

[0043]

[61] The passages in the baffle assembly 150 begin at the edges 154A, 154B of the transmissive region 152, and the passages in the baffle assembly 150 extend to the inner surface 156 of the EUV vessel 26. The baffle assembly 150 may include a series of concentric baffles that surround the transmissive region 152 but do not project into it. The baffle assembly 150 extends substantially from the edges 154A, 154B of the transmissive region 152 to the inner surface 156 of the EUV vessel 26.

[0044]

[62] Although shown in a horizontal configuration, it should be noted that in some embodiments, the EUV vessel 26 is configured in a generally vertical orientation such that the baffle assembly 150 and the outlet 40A of the EUV vessel are directed substantially directly above the collector 30. As a result, target material deposits that form on the baffle assembly 150 may become dislodged and unintentionally collect on the collector 30.

[0045]

[63] Figure 1C is a schematic diagram of an EUV collector 30 including target material debris deposits 161A-D and 162 according to embodiments of the disclosed subject matter. The target material debris deposits 161A-D and 162 may exist in many forms. By way of example, relatively small particles 161A discernible to the naked eye may deposit on the surface of the collector 30. Larger deposits 161B, 161D may include multiple small particles that solidify or otherwise accumulate and / or aggregate into larger deposits and / or target material debris deposits that initially formed on the baffle assembly 150, were released from the baffle assembly, and then deposited on the collector 30. An even larger target material debris deposit 161C may also form on the collector 30 for various reasons. In addition to the target material debris deposits 161A-D described above, a very fine layer of target material debris deposit 162 may coat substantially the entire surface of the collector 30 and other surfaces inside the EUV vessel 26. The very fine layer target material debris deposit 162 may be comprised of substantially microscopic target material debris that may resemble a substantially uniform dust coating on the surface of the collector 30 .

[0046]

[64] FIG. 1D is a schematic diagram of a portion of a baffle assembly 150 according to embodiments of the disclosed subject matter. The baffle assembly 150 includes a number of separate vanes 151A, 151B. The vanes 151A, 151B are separated from one another by variable distances as shown. Furthermore, the vanes are formed at variable angles as shown due to differences between vanes 151A and 151B. Target material debris deposits 171A-171C may be formed at various locations on the number of separate vanes 151A, 151B. By way of example, the target material deposit 171A may be formed near the region of the intermediate focus 40 of the EUV vessel 26. Similarly, the target material debris deposits 171B and 171C may be formed along the outer edges of the vanes 151A, 151B somewhat closer to the inner surface 156 of the EUV vessel 26. As described above, target material debris piles 171A-171C may initially form on the baffle assembly 150 and then become dislodged from the baffle assembly for various reasons and collect on the surface of collector 30.

[0047]

[65] The various target material debris deposits 161A-161D, 171A-171C will ultimately interfere with the performance of the EUV vessel 26 in various ways and must be removed at some point. One approach to removing the target material debris deposits is to interrupt the EUV generation and disassemble the EUV vessel 26 to clean each of the individual parts of the EUV vessel, such as the collector 30, the baffle assembly 150, and other interior surfaces 156. However, interrupting the generation of EUV in the EUV vessel 26 would interrupt the EUV lithography process that is consuming the EUV generated in the EUV vessel, effectively stopping production. A more effective EUV vessel cleaning process is needed. Various forms of in situ hydrogen radical generation provide a more effective and timely cleaning process for removing the various target material debris deposits 161A-161D, 171A-171C from the EUV vessel 26 without interrupting the generation of EUV light in the EUV vessel.

[0048]

[66] FIG. 2 is a simplified schematic diagram of an EUV light source 200 including one or more in situ hydrogen radical sources 201, 201', 201" in accordance with embodiments of the disclosed subject matter. The EUV light source 200 includes one or more in situ hydrogen radical sources 201, 201', 201" that can be positioned at one or more locations within the EUV vessel 26. The in situ hydrogen radical source 201 is positioned near the periphery of the collector 30. The central in situ hydrogen radical source 201' is positioned near the central aperture 32 of the collector 30. The baffled in situ hydrogen radical source 201" is positioned near a baffle assembly of the EUV vessel 26. It should be noted that the EUV vessel 26 can include as few as one of the in situ hydrogen radical sources 201, 201', 201", or as many as can be physically positioned within the EUV vessel. The in situ hydrogen radical sources 201, 201', 201" can be one or more of different types and configurations of in situ hydrogen radical sources, as described in more detail below.

[0049]

[67] A hydrogen gas source 290 is coupled to each of the in situ hydrogen radical sources 201, 201', 201". Optionally, a carrier gas source 291 may be coupled to each of the in situ hydrogen radical sources 201, 201', 201". As described in more detail below, one or more signal sources 212 may be coupled to each of the in situ hydrogen radical sources 201, 201', 201". The in situ hydrogen radical sources 201, 201', 201" may be positioned at substantially symmetric or asymmetric locations within the EUV vessel 26.

[0050]

[68] Figure 3A is a detailed cross-sectional view of a portion of a collector 30 and an in-situ hydrogen radical source 201 according to embodiments of the disclosed subject matter. Figure 3B is a simplified schematic diagram of a cross-sectional view of a collector 30 and an in-situ hydrogen radical source 201 according to embodiments of the disclosed subject matter. Collector 30 has a collector surface 30A and a collector rim 30B. Collector 30 also includes a central aperture 32. A hydrogen radical source 201 is disposed adjacent to collector 30. In the illustrated embodiment, the hydrogen radical source 201 is disposed directly adjacent to the rim 30B of collector 30.

[0051]

[69] The hydrogen radical source 201 includes a radical generator 202, an outlet channel 203 leading beyond a rim channel 204, and an outlet 205. The radical generator 202 is coupled to a signal source 212. The hydrogen radical source 201 is coupled to a hydrogen source, not shown. The hydrogen source can be a source of hydrogen gas or other hydrogen-containing source material, such as a hydrogen-containing gas or a mixture of hydrogen-containing gases. The hydrogen source can also include a mixing device for mixing the hydrogen-containing gas with an inert carrier gas 208, such as argon, helium, nitrogen, and other substantially inert get carrier gases. In other embodiments, the inert carrier gas 208 can be directly injected into the hydrogen radical source 201.

[0052]

[70] H + and / or H - Hydrogen radical H containing ions *The hydrogen radicals are created by injecting hydrogen into the hydrogen radical source 201 and exciting the radical generator 202. The hydrogen radicals then flow through the outlet channel 203, through the rim channel 204, and out the outlet 205 proximate to the surface 30A of the collector 30. An inert carrier gas can be used to transport the hydrogen radicals from the hydrogen radical source 201 to the surface 30A of the collector 30. The hydrogen radicals can then react with the target material debris deposits 171A, 162 disposed on the surface 30A of the collector 30 to create volatile tin compounds. The volatile tin compounds can then be purged from the EUV vessel 26 through the purge outlet 296 (shown in FIG. 2) using a purge gas source 295 (shown in FIG. 2).

[0053]

[71] Referring to FIG. 3B, the hydrogen radical source 201 can be a capacitively coupled hydrogen plasma chamber having a wall 201A coupled to a first potential and a radical generator 202 coupled to a second potential. As shown, the wall 201A is grounded and the radical generator 202 is coupled to a signal source 210. However, it should be understood that the wall 201A can be coupled to a signal source 212 and the radical generator 202 can be grounded or coupled to a second signal source. In one embodiment, the signal source 212 can be an RF signal source having a frequency in the range of tens of kHz to about 10 GHz. The signal source 212 excites hydrogen present in the hydrogen radical source 201 to convert the hydrogen into hydrogen radicals H * A hydrogen plasma 202A can be generated that splits into

[0054]

[72] Figure 4 is a simplified schematic diagram of a cross-sectional view of a collector 30 and an alternative in situ hydrogen radical source 221 according to embodiments of the disclosed subject matter. The alternative in situ hydrogen radical source 221 is somewhat similar to the in situ hydrogen radical source 201, but includes a ceramic insulator 220 to isolate the walls 201A and radical generator 211 of the alternative in situ hydrogen radical source 221 from the plasma 202A generated therein.

[0055]

[73] Figure 5 is a simplified diagram of a collector 30 having an in-situ hydrogen radical source 231 that substantially surrounds the outer periphery of the collector, in accordance with embodiments of the disclosed subject matter. The in-situ hydrogen radical source 231 is an annular chamber disposed around the outer periphery of the collector 30. The in-situ hydrogen radical source 231 has a cross section substantially similar to the in-situ hydrogen radical source 201 or 221 as described above. The in-situ hydrogen radical source 231 generates hydrogen radicals, H * The collector 30 has outlets 205A around its periphery so that the is generated and output substantially evenly around the periphery of the collector.

[0056]

[74] Figure 6 is a simplified diagram of a collector 30 having multiple in situ hydrogen radical sources 201 substantially evenly distributed and positioned around the periphery of the collector, in accordance with embodiments of the disclosed subject matter. Each of the in situ hydrogen radical sources 201 generates hydrogen radicals H * The in situ hydrogen radical sources 201 include outlets 205 such that the in situ hydrogen radical sources 201 are output around the periphery of the collector 30. Each of the in situ hydrogen radical sources 201 can be any one or more of the in situ hydrogen radical sources described herein. In one embodiment, each of the hydrogen radical sources 201 distributed around the periphery of the collector 30 is the same type of hydrogen radical source. In other embodiments, the hydrogen radical sources distributed around the periphery of the collector 30 include more than one type of hydrogen radical source.

[0057]

[75] Figure 7 is a simplified schematic diagram of a cross-sectional view of a collector 30 and a plurality of in-situ hydrogen radical sources 201 according to embodiments of the disclosed subject matter. One or more of the plurality of in-situ hydrogen radical sources 201 are disposed around the periphery and along the edge 30B of the collector 30. In addition to the in-situ hydrogen radical sources 201 disposed around the periphery of the collector 30, the hydrogen radicals H generated therein are *One or more central in-situ hydrogen radical sources 271 are disposed in close proximity to the central aperture 32 so that the hydrogen radicals H generated in the central in-situ hydrogen radical source 271 are output through the central aperture of the collector. * provides hydrogen radicals in close proximity to the target material debris deposited on the collector 30 and near the central aperture 32. It should be noted that although the central in situ hydrogen radical sources 271 are shown as being similar to the hydrogen radical source 201 described above, each of the central in situ hydrogen radical sources 271 can be any type of hydrogen radical source described herein.

[0058]

[76] Each of the central in situ hydrogen radical sources 271 has a respective signal source 212A and 212B, and the in situ hydrogen radical source 201 has a respective signal source 212. Each signal source 212, 212A, 212B can be the same or different signal sources with the same or different frequency, power, duty cycle, or amplitude such that each of the in situ hydrogen radical sources 201, 271 can be individually controlled to generate an amount of hydrogen radicals as needed for each local surface area on which target material debris has accumulated. As an example, if a large amount of target material debris has accumulated on the surface area of ​​the collector 30 immediately adjacent the aperture 32, and a relatively small amount of target material debris has accumulated in an area near the periphery of the collector, the required amount of hydrogen radicals H * is the amount of hydrogen radicals H required near the periphery to remove the respective amount of target material debris local to each outlet of the in situ hydrogen radical source 201, 271. * will be greater than the amount of

[0059]

[77] Figure 8 is a simplified schematic side view of an induced hydrogen radical generator 800 according to embodiments of the disclosed subject matter. Figure 9 is a simplified schematic top view of an induced hydrogen radical generator 800 according to embodiments of the disclosed subject matter. The induced hydrogen radical generator 800 includes a plurality of hydrogen nozzles 802 disposed around the periphery of the collector 30. An induction coil 804 is disposed between the hydrogen nozzles and the rim 30B of the collector 30.

[0060]

[78] The induction coil 804 has a first end coupled to the signal source 212C. The induction coil 804 has a second end coupled to ground. Although the induction coil 804 is shown making only one substantial loop around the periphery of the collector 30, it should be noted that this is shown to simplify the description of the induction coil and that the induction coil may include one or more loops around the periphery of the collector.

[0061]

[79] Signal source 212C outputs an induction signal of suitable frequency, amplitude, and duty cycle. When the induction signal passes through induction coil 804, a magnetic field is induced at the center of the coil, as shown in FIG. 9. A hydrogen nozzle 802 for injecting hydrogen into the center of the coil allows the creation of hydrogen plasma 810. The hydrogen plasma produces hydrogen radicals H * where hydrogen radicals H * can interact with any target material deposits that may be present.

[0062]

[80] Figure 10 is a simplified schematic side view of an induced hydrogen radical generator 1000 according to embodiments of the disclosed subject matter. The induced hydrogen radical generator 1000 differs from the induced hydrogen radical generator 800 described in Figures 8 and 9 in that the induction coil 1004 is located outside the sidewall 1008 of the EUV vessel 26. The sidewall 1008 includes a ceramic window 1007 through which the induction coil can induce a magnetic field over the surface 30A of the collector 30. As described above, the hydrogen nozzle 802 injects hydrogen into the magnetic field generated by the induction coil 1004 to generate the required hydrogen radicals H * A hydrogen plasma 810 is created that generates

[0063]

[81] Figure 11 is a simplified schematic side view of a capacitive hydrogen radical generator 1100 according to embodiments of the disclosed subject matter. The capacitive hydrogen radical generator 1100 uses a conductive layer 1120 of the collector 30 as a first electrode and a wall 1008 of the EUV vessel 26 as a second electrode. The collector 30 includes multiple layers 1120, 1122, 1124, 1126. One of these layers is the conductive layer 1120. The conductive layer 1120 can be formed from any suitable conductive material, including copper, aluminum, steel, stainless steel, and compounds and alloys containing copper, aluminum, steel, and stainless steel. The conductive layer 1120 can also include heating and cooling devices and subsystems for managing the temperature of the collector 30. In one example, the conductive layer 1120 includes a resistive heater and / or cooling channels for passing a cooling fluid, such as a gas or liquid coolant. The conductive layer 1120 can also provide physical structural support and attachment points for the collector 30.

[0064]

[82] A silicon, glass, or quartz layer 1122 is supported by the conductive layer 1120. A reflective layer 1124 is supported on the silicon, glass, or quartz layer 1122. The reflective layer 1124 performs the reflective function of the collector 30. An optional protective layer 1126 may be formed on the reflective layer 1124. It should be understood that the thicknesses of the various layers 1120, 1122, 1124, and 1126 are not precisely shown in the detailed view of FIG.

[0065]

[83] In operation, when a signal is applied to the conductive layer 1120 from the signal source 212C, the signal is capacitively coupled to hydrogen gas injected from the hydrogen nozzle 1106 to generate hydrogen plasma 1110, which generates hydrogen radicals H * occurs.

[0066]

[84] Figure 12 is a simplified schematic side view of a capacitive hydrogen radical generator 1200 according to embodiments of the disclosed subject matter. The hydrogen radical source 221 can be a capacitively coupled hydrogen plasma chamber having a wall 201A coupled to a first potential and a radical generator 211 coupled to a second potential. As shown, the wall 201A is grounded and the radical generator 202 is coupled to a signal source 212. However, it should be understood that the wall 201A can be coupled to the signal source 212 and the radical generator 211 can be grounded or coupled to a second signal source (not shown). In one embodiment, the signal source 212 can be an RF signal source having a frequency in the range of tens of kHz to about 10 GHz. The signal source 212 excites hydrogen present in the hydrogen radical source 221 to convert the hydrogen into hydrogen radicals H * A hydrogen plasma 202A can be generated that splits into

[0067]

[85] The capacitive hydrogen radical generator 1200 also uses the conductive layer 1120 of the collector 30 as a third electrode coupled to a second signal source 1212. The second signal source 1212 can generate a signal in the range from DC (0 Hz) to about several tens of MHz. In one embodiment, the second signal source 1212 outputs a signal from 0 Hz to about 13 MHz. The second signal source 1212 generates hydrogen radicals H * , which attracts hydrogen radicals H near the surface 30A and the target material debris deposits thereon. * can be used to increase the concentration of hydrogen radicals H near the surface 30A. * Increasing the concentration of SnH 4 The conversion of tin to volatile tin compounds such as tin oxide increases.

[0068]

[86] FIG. 13 is a simplified schematic side view of an EUV vessel 26 including a capacitive hydrogen radical source 201" disposed in or near a baffle 150 in accordance with embodiments of the disclosed subject matter. The hydrogen radical source 201" includes a first electrode 1302 and a second electrode 1304. In some embodiments, the first electrode 1302 is grounded. In some embodiments, the second electrode 1304 is coupled to a signal source 1312. Alternatively, the first electrode 1302 can be coupled to the signal source 1312 and the second electrode 1304 can be coupled to ground. Alternatively, instead of coupling one of the electrodes 1302, 1304 to ground, that electrode can be coupled to a second signal source, not shown. The second electrode 1304 can be insulated from a sidewall 1008 of the EUV vessel 26 by an optional insulating layer 1306.

[0069]

[87] When hydrogen is injected into the hydrogen radical source 201″ and an appropriate signal is applied to the electrodes 1302, 1304, hydrogen radicals H * Next, hydrogen radicals H * may react with the target material debris depositing on the baffle 150 to produce volatile by-products that can be exhausted or purged from the EUV vessel 26.

[0070]

[88] Figure 14 is a flow chart diagram illustrating method operations 1400 performed in generating hydrogen radicals in situ within the EUV vessel 26, according to embodiments of the disclosed subject matter. It should be understood that the operations illustrated herein are by way of example, and that some operations may have sub-operations, and in other cases, certain operations described herein may not be included in the illustrated operations. With this in mind, the method and operations 1400 will now be described.

[0071]

[89] In operation 1405, hydrogen radicals are generated in situ in the EUV chamber proximate to the target material debris deposition. * is generated by the various hydrogen radical sources described above. Several different hydrogen radical sources are described above, and more than one hydrogen radical source may be included within the EUV vessel 26, which may be selectively activated to remove particular target material debris deposits proximate to the activated hydrogen radical source or sources. Each hydrogen radical source produces a variable amount of hydrogen radicals, H * Note that the inputs can be independently operated at different operating parameters to generate

[0072]

[90] In operation 1410, hydrogen radicals H * The volatile compounds combine with the target material debris pile to convert the target material debris pile into volatile compounds. In operation 1415, the volatile compounds are removed from the EUV container 26. The volatile compounds may be removed from the EUV container 26 by purging or evacuating the volatile compounds. It should be noted that operations 1405-1415 may be performed while the EUV container 26 is producing EUV radiation.

[0073]

[91] In one embodiment, the in situ cleaning process includes generating and injecting hydrogen radicals near the aperture 32 at a flow rate of about 90 slm, and generating and injecting hydrogen radicals near the periphery of the EUV collector 30 at a flow rate of about 90 slm while maintaining a pressure of about 1.3 Torr, and the signal sources 212, 212A, 212B, 212C, 1212 provide RF signals between about several kHz and several hundred MHz at a power of about 1 kW to several kW depending on the desired cleaning rate. It should be understood that these are merely examples of flow rates, RF frequencies, and RF powers, and that smaller or larger flow rates, RF frequencies, and RF powers, as well as combinations thereof, can be used. It should also be understood that the generation and injection of hydrogen radicals can be at different flow rates, RF frequencies, and RF powers in one or more localized portions of the periphery of the EUV collector 30 and aperture 32 as needed to address additional target material debris proximate to the respective outlets of the respective hydrogen radical sources.

[0074]

[92] Figure 15 is a flow chart diagram illustrating method operations 1500 performed in generating EUV light while simultaneously removing target material debris buildup within EUV vessel 26, according to embodiments of the disclosed subject matter. It should be understood that the operations illustrated herein are exemplary, and that some operations may have sub-operations, and in other cases certain operations described herein may not be included in the illustrated operations. With this in mind, the method and operations 1500 will now be described.

[0075]

[93] In operation 1505, a source laser is directed at a portion of a target material within the EUV vessel 26.

[0076]

[94] In operation 1510, a plasma is generated when the source laser interacts with the target material in the EUV vessel 26. When the source laser interacts with the target material in the EUV vessel, a first portion of the target material is converted to plasma and a second portion of the target material is disposed of as target material debris.

[0077]

[95] In operation 1515, EUV light emitted from the plasma is collected in collector 30. In operation 1520, a second portion of the target material is settled on various interior surfaces of EUV vessel 26.

[0078]

[96] In operation 1525, if additional EUV light needs to be generated, then this method operation continues as described above to operation 1505. If additional EUV light does not need to be generated, then this method operation may end.

[0079]

[97] Simultaneously with operation 1505, operation 1507 generates hydrogen radicals H in situ in the EUV chamber 26. * The hydrogen radicals are generated in one or more hydrogen radical sources disposed within the EUV vessel 26.

[0080]

[98] At operation 1512, the hydrogen radical H * interacts with the target material debris deposit to form volatile compounds. Typically, as described above, the target material contains tin and hydrogen radicals H * The volatile compound created by the interaction of SnH 4 It should be appreciated that operation 1512 may create any suitable volatile compound that contains at least a portion of the target material debris pile.

[0081]

[99] In operation 1517, the volatile compounds created in operation 1512 are removed from the EUV vessel 26. The volatile compounds may be removed by purging or evacuating the EUV vessel 26, or a combination thereof.

[0082]

[0100] In operation 1522, if additional target material debris deposits need to be removed, then method operations continue to operation 1507 above. If additional target material debris deposits do not need to be removed from the EUV vessel 26, then method operations may end. Note that the target material debris deposit removal in operations 1507-1522 may be performed simultaneously with the generation of EUV in operations 1505-1525 in the EUV vessel 26. In other embodiments, the target material debris deposit removal in operations 1507-1522 may be performed overlapping with or alternative to the generation of EUV in operations 1505-1525.

[0083]

[0101] In one embodiment, the in situ cleaning process includes generating and injecting hydrogen radicals at various locations around the EUV vessel at a flow rate of about 90 slm while maintaining a pressure of about 1.3 Torr, and the signal source 1312 provides an RF signal between about several kHz and several hundred MHz at a power of about 1 kW to several kW depending on the desired cleaning rate. It should be understood that these are merely example flow rates, RF frequencies, and RF powers, and that smaller or larger flow rates, RF frequencies, and RF powers, as well as combinations thereof, can be used. It should also be understood that the generation and injection of hydrogen radicals can be at different flow rates, RF frequencies, and RF powers in one or more localized portions of the EUV vessel as needed to address additional target material debris proximate to the respective outlets of the respective hydrogen radical sources disposed around the inside of the EUV vessel.

[0084]

[0102] With the above embodiments in mind, it should be understood that the invention can employ various computer-implemented operations involving data stored in computer systems. These operations require physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. Further, the manipulations performed are often referred to in terms, such as producing, identifying, determining, or comparing.

[0085]

[0103] Any of the operations described herein and forming part of the invention are useful machine operations. The invention also relates to a device or apparatus for performing these operations. The apparatus can be specially constructed for the required purpose, such as a special purpose computer. When defined as a special purpose computer, the computer can also perform other processes, program execution, or routines that are not part of the special purpose, while still being operable for the special purpose. Alternatively, these operations can be processed by a general purpose computer selectively activated or configured by one or more computer programs stored in a computer memory, cache, or obtained over a network. If the data is obtained over a network, the data can be processed by other computers on the network, such as a cloud of computing resources.

[0086]

[0104] Embodiments of the present invention may also be defined as a machine that transforms data from one state to another. The transformed data may be stored in a storage device and then manipulated by a processor, which thus transforms the data from one thing to another. Furthermore, the above methods may be processed by one or more machines or processors that may be connected by a network. Each machine may transform data from one state or thing to another, process data, store data in a storage device, transmit data over a network, display the results, or communicate the results to other machines.

[0087]

[0105] The present invention can also be embodied as computer readable code on a computer readable medium. A computer readable medium is any data storage device that can store data which can then be read by a computer system. Examples of computer readable media include hard drives, network attached storage (NAS), read only memory, random access memory, CD-ROM, CD-R, CD-RW, DVD, flash, magnetic tape, and other optical and non-optical data storage devices. The computer readable medium can also be distributed by network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

[0088]

[0106] It will be further appreciated that the instructions represented by the acts in the above diagrams need not be executed in the order illustrated, and not all of the operations represented by the acts may be necessary to practice the invention. Additionally, the processes described in any of the above diagrams may be implemented in software stored in any one or combination of RAM, ROM, or a hard disk drive.

[0089]

[0107] Although the above invention has been described in some detail for clarity of understanding, it will become apparent that certain changes and modifications can be practiced within the scope of the appended claims. Thus, the embodiments of the present invention are to be considered as illustrative and not restrictive, and the present invention is not to be limited to the details set forth herein, but may be modified within the scope of the appended claims and their equivalents.

Claims

1. an EUV vessel including an EUV vessel purge gas inlet coupled to a purge gas source capable of introducing a quantity of purge gas into the EUV vessel; an EUV collector disposed within the EUV vessel, the EUV collector including a reflective surface; a target material source capable of inputting a quantity of target material into the EUV vessel, a first portion of the quantity of target material being disposed on at least a portion of the reflective surface of the EUV collector as a first target material debris deposit; a first hydrogen radical source disposed within the EUV vessel, a first hydrogen radical source outlet disposed proximate the reflective surface of the EUV collector; a first hydrogen source inlet coupled to a hydrogen source; a first hydrogen source electrode coupled to a first signal source; a second hydrogen source electrode coupled to a second signal source; a first hydrogen radical source capable of generating a first amount of hydrogen radicals and inputting the first amount of hydrogen radicals from the first hydrogen radical source outlet, the first amount of hydrogen radicals capable of combining with the first target material debris pile to form a first amount of volatile compounds containing at least a portion of the first target material debris pile; an EUV container purge outlet capable of venting the first amount of the volatile compound from the EUV container; 2. An EUV light source comprising:

2. The EUV light source of claim 1 , wherein the first hydrogen radical source comprises a hydrogen plasma chamber.

3. The EUV light source of claim 2 , wherein the hydrogen plasma chamber is a capacitively coupled hydrogen plasma chamber.

4. The EUV light source of claim 3 , wherein the capacitively coupled hydrogen plasma chamber includes a third hydrogen source electrode coupled to a third signal source.

5. The EUV light source of claim 4 , wherein the third hydrogen source electrode comprises at least a portion of a conductive layer of the EUV collector.

6. The EUV light source of claim 2 , wherein the hydrogen plasma chamber is an inductively coupled hydrogen plasma chamber.

7. The EUV light source of claim 1 , wherein the first hydrogen radical source outlets are disposed around a periphery of the EUV collector.

8. The EUV light source of claim 1 , wherein the first hydrogen radical source outlet is located near a central aperture of the EUV collector.

9. 10. The EUV light source of claim 1, wherein generating the first amount of hydrogen radicals also includes preventing oxygen-containing species from entering the EUV enclosure.

10. The EUV light source of claim 1 , wherein the first hydrogen source electrode is included in the EUV collector.

11. 2. The EUV light source of claim 1, wherein the first hydrogen radical source has a substantially annular shape and the first hydrogen radical source outlet is located immediately adjacent to an outer periphery of the EUV collector.

12. A plurality of EUV container inner surfaces included in the EUV container, the plurality of EUV container inner surfaces including a plurality of baffles; a second portion of the quantity of target material disposed on at least a portion of the plurality of EUV container inner surfaces as a second target material debris pile; a second hydrogen radical source disposed within the EUV vessel, a second hydrogen radical source outlet disposed proximate at least one of said plurality of baffles; a second hydrogen source inlet coupled to the hydrogen source; a third hydrogen source electrode coupled to a third signal source; a fourth hydrogen source electrode coupled to a fourth signal source; a second hydrogen radical source capable of generating a second amount of hydrogen radicals and inputting the second amount of hydrogen radicals from the second hydrogen radical source outlet, the second amount of hydrogen radicals capable of combining with the second target material debris pile to form a second amount of the volatile compound containing at least a portion of the second target material debris pile; the EUV container purge outlet capable of venting the second amount of the volatile compound from the EUV container; The EUV light source of claim 1 further comprising:

13. 1. An EUV container, comprising: an EUV vessel purge gas inlet coupled to a purge gas source capable of introducing a quantity of purge gas into the EUV vessel; A plurality of EUV container inner surfaces; an EUV container comprising: an EUV collector disposed within the EUV vessel, the EUV collector including a reflective surface; a target material source operable to input a quantity of target material into the EUV vessel, a first portion of the quantity of target material being disposed on at least a portion of the reflective surface of the EUV collector as a first target material debris deposit and a second portion of the quantity of target material being disposed on at least a portion of the plurality of inner surfaces as a second target material debris deposit; a first hydrogen plasma chamber disposed within the EUV vessel, a first hydrogen radical source outlet disposed proximate an outer periphery of the reflective surface of the EUV collector; a first hydrogen source inlet coupled to a hydrogen source; at least one first hydrogen source electrode coupled to a first signal source; a first hydrogen plasma chamber capable of generating a first amount of hydrogen radicals and inputting the first amount of hydrogen radicals from the first hydrogen radical source outlet, the first amount of hydrogen radicals capable of combining with the first target material debris pile to form a first amount of volatile compounds containing at least a portion of the first target material debris pile; a second hydrogen plasma chamber disposed within the EUV vessel, a second hydrogen radical source outlet disposed proximate at least one of the plurality of EUV vessel inner surfaces; a second hydrogen source inlet coupled to the hydrogen source; at least one second hydrogen source electrode coupled to a second signal source; a second hydrogen plasma chamber capable of generating a second amount of hydrogen radicals and inputting the second amount of hydrogen radicals from the second hydrogen radical source outlet, the second amount of hydrogen radicals capable of combining with the second target material debris pile to form a second amount of the volatile compound containing at least a portion of the second target material debris pile; an EUV container purge outlet capable of venting the first amount of the volatile gas and the second amount of the volatile compound from the EUV container; 2. An EUV light source comprising:

14. 1. A method of cleaning a target material debris buildup in an EUV light source while simultaneously generating EUV light in the EUV light source, comprising: generating a quantity of hydrogen radicals within an EUV vessel of the EUV light source; outputting the generated amount of hydrogen radicals proximate to the target material deposition on an inner surface of the EUV vessel; forming a first amount of a volatile compound containing at least a portion of the first portion of the target material deposit; introducing a quantity of purge gas into the EUV vessel; purging the first amount of volatile compounds from the EUV container, the first amount of volatile compounds being purged through an EUV container purge outlet; A method comprising:

15. The method of claim 14 , wherein the first hydrogen radical source comprises a hydrogen plasma chamber.

16. The method of claim 15 , wherein the hydrogen plasma chamber is a capacitively coupled hydrogen plasma chamber.

17. The method of claim 15 , wherein the hydrogen plasma chamber is an inductively coupled hydrogen plasma chamber.

18. The method of claim 14 , wherein the first hydrogen radical source outlets are positioned around the periphery of the EUV collector.

19. The method of claim 14 , wherein the first hydrogen radical source outlet is located near a central aperture of the EUV collector.

20. 10. The EUV light source of claim 1, further comprising a central aperture hydrogen radical source having a central aperture hydrogen radical source outlet disposed near a central aperture of the EUV collector, the first hydrogen radical source outlet being disposed immediately adjacent an outer periphery of the EUV collector.

21. 21. The EUV light source of claim 20, wherein at least one of the first hydrogen radical source or the central aperture hydrogen radical source is an inductively coupled hydrogen plasma chamber.

22. 21. The EUV light source of claim 20, wherein the first hydrogen radical source and the central aperture hydrogen radical source are inductively coupled hydrogen plasma chambers.

Images