EUV source container heating gas delivery device and method

Abstract

A system for generating extreme ultraviolet (EUV) radiation includes a source vessel having an interior volume, a source laser configured to generate light that enters the interior volume in an incident light direction along an optical axis to provide energy to a target to cause generation of EUV within the interior volume, and a heated gas delivery device (336) configured to deliver heated gas to the source vessel. A heated gas delivery device is within the interior volume, configured to deliver a heated gas into the interior volume, and positioned on and extending along the optical axis, the heated gas delivery device has an outlet to distribute heated gas into the interior volume and one or more inlet openings to receive light from the source laser to heat the heated gas delivery device. A method for providing EUV radiation is also disclosed.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Application No. 63 / 514,455, filed July 19, 2023, entitled “EUV SOURCE VESSEL HEATEDGAS DELIVERY APPARATUS AND METHOD,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to an extreme ultraviolet (“EUV”) source container having means for transferring heated gas into the source container, and to a method for transferring heated gas into the source container. Background Technology

[0003] Extreme ultraviolet (“EUV”) light (i.e., electromagnetic radiation with wavelengths of about 50 nm or less (sometimes also called soft X-rays), including radiation with wavelengths of about 13.5 nm) can be used in photolithography processes to create extremely small features in or on substrates such as silicon wafers. Methods for generating EUV light involve converting a target material into a plasma state. The target material includes at least one element, such as xenon, lithium, or tin, which has one or more emission lines in the EUV portion of the electromagnetic spectrum. The target material can be solid, liquid, or gas. In one such method (often called laser-produced plasma (“LPP”), the desired plasma can be generated using a “source” laser (typically a CO2 laser emitting infrared light at or around 10,600 nanometers (nm)) to irradiate a target containing one or more EUV line-emitting elements with one or more light pulses. The plasma is typically generated in a sealed “source container” (which is typically a vacuum chamber).

[0004] Generating plasma from target material within a source container generates vapor, ions, particles, and other debris that deposit on and contaminate surfaces within the source container, including optical surfaces. Therefore, it is necessary to remove one or more residual target materials from the source container to reduce or eliminate surface contamination. This requirement is typically met, at least in part, by using a gas flow introduced into the source container and then removed from it along with one or more residual target materials. Summary of the Invention

[0005] In some general aspects, a system for generating extreme ultraviolet (EUV) radiation is provided, the system comprising a source container, a source laser, and a heating gas delivery device, the source container having an internal volume, the source laser being configured to generate light entering the internal volume along an optical axis in the direction of incident light to provide energy to a target, thereby causing EUV generation within the internal volume, the heating gas delivery device being disposed within the internal volume and configured to deliver heating gas into the internal volume, the heating gas delivery device being positioned on and extending along the optical axis, the heating gas delivery device having an outlet for dispensing heating gas into the internal volume and one or more inlet openings for receiving light from the source laser to heat the heating gas delivery device.

[0006] The implementation may include one or more of the following features. The heated gas transfer device may also include an inner surface having a reflectivity equal to or less than 0.9 for light from the source laser, to absorb at least some of the light received from the source laser through one or more inlet openings. The heated gas transfer device may also include a tapered inner surface for receiving, partially reflecting once or multiple times, and at least partially absorbing light received from the source laser through one or more inlet openings. The tapered inner surface may be or may include a conical inner surface.

[0007] The system may also include a heating gas source connected to the heating gas transfer device to transfer heating gas to the heating gas transfer device. The heating gas source may be located outside the internal volume.

[0008] The heated gas transfer device may also include a gas conduit connected to an outlet. The heated gas transfer device may also include a heating element configured to heat the heated gas transfer device and / or the gas transferred by the heated gas transfer device.

[0009] The system may also include a collector configured to reflect EUV light generated at or near the collector's primary focal point to the collector's intermediate focal point. The collector has an optical axis substantially coincident with the optical axis and a through-hole along the optical axis, the through-hole being configured to allow light to enter an internal volume such that most or all of the EUV light reflected from the collector (1) travels from the collector to the intermediate focal point within the volume of a first approximate cone and (2) outside the volume of a second approximate cone. The first approximate cone has its base at the periphery of the collector and its apex at the intermediate focal point, while the second approximate cone has its base at the through-hole and its apex at the intermediate focal point. A heating gas transfer device is disposed within the second approximate cone along the optical axis. The heating gas transfer device may have a conical outer surface that, when the heating gas transfer device is at operating temperature, is spaced apart from the surface of the second approximate cone such that the outer surface does not impact the second approximate cone during operation.

[0010] The heating gas transfer device can extend along the optical axis by a distance ranging from 90 to 110 cm. The heating gas transfer device can also extend along the optical axis by a distance ranging from 50% to 70% of the distance from the principal focal point to the intermediate focal point along the optical axis. At least some of the outlets of the heating gas transfer device can be positioned within the conical outer surface of the heating gas transfer device, the conical outer surface narrowing along the optical axis and extending away from the direction of incident light.

[0011] In some additional general aspects, a method for providing extreme ultraviolet (EUV) radiation is provided, the method comprising: radiating a target with light from a source laser within an internal volume of a source container to generate EUV-generating plasma; generating reflected EUV light within the internal volume by reflecting EUV light from the plasma along a reflected EUV path; receiving light from the source laser into a heated gas transfer device to heat the heated gas transfer device; and transferring heated gas from the heated gas transfer device into the internal volume of the source container along a reflected EUV path.

[0012] The implementation may include one or more of the following features: One side of the heating gas transfer device may include an outlet. The heating gas transfer device may include or may have a tapered shape that narrows in the direction toward the intermediate focal point of the collector. The heating gas transfer device may extend a distance in the range of 90 cm to 110 cm in a direction parallel to the optical axis of the source laser. The heating gas transfer device extends 50% to 70% of the distance from the main focal point to the intermediate focal point of the collector in a direction parallel to the optical axis of the source laser.

[0013] Details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the specification, drawings, and claims. Attached Figure Description

[0014] Figure 1A This is a schematic diagram of cross-sections of an extreme ultraviolet (EUV) light source.

[0015] Figure 1B yes Figure 1A A schematic diagram of the cross-section of an EUV light source, which is rotated 90 degrees around the z-axis and rotated so that gravity is represented downwards in the plane of the page.

[0016] Figure 2 This is a block diagram of an EUV source used in conjunction with a photolithography exposure apparatus.

[0017] Figure 3A It can be located in Figure 1A or Figure 1B A perspective view of the implementation of the heating gas transfer device in an EUV light source.

[0018] Figure 3B It is relative to Figure 3A The view is rotated 90 degrees around the z-axis. Figure 3A A perspective view of a heating gas transfer device.

[0019] Figure 3C It is along Figure 3A The line cut from 3C to 3C Figure 3B Cross-sectional view of the heating gas transfer device.

[0020] Figure 4 It is another implementation of a heated gas transfer device similar to Figure 3C Cross-sectional view.

[0021] Figure 5 This is a schematic cross-sectional view of the collector and the heating gas transfer device.

[0022] Figure 6 It is used for operations including such Figure 1A , Figure 1B , Figure 3A , Figure 3B , Figure 4 , Figure 5 or Figure 6 A flowchart of the process of the light source in the heating gas transfer device. Detailed Implementation

[0023] Figure 1A This is a simplified schematic cross-sectional view of some components used in the implementation of the EUV light source 110. As shown on the reference coordinate axes, Figure 1AThe cross-section of the EUV light source 110 is taken in the xz plane, where x is positive upwards in the page plane and z is positive to the right in the page plane, and the z axis is aligned with the optical axis A of the source laser 112, which will be described below.

[0024] like Figure 1A As shown, the EUV source 110 includes a source laser 112 for generating a beam 113 of light pulses (e.g., laser pulses) and delivering the beam 113 from the source laser 112 into the internal volume 114 of the source container 111 to individually irradiate a target 115 at or near the irradiation station 116. The target 115 travels downward (in the negative x direction) from the target delivery system 117a to the irradiation station 116 in the page plane. The source container 111 has an inner surface 156 surrounding the internal volume 114.

[0025] like Figure 1A As shown, the EUV source 110 includes a target delivery system 117a that delivers a target 115 into the interior 114 of the source container 111, reaching the radiation station 116. At the radiation station 116, the target 115 individually interacts with one or more light pulses (of beam 113) to generate a plasma 118, which produces EUV light 119 (represented in the figure by the boundary ray indicated by reference numeral 119). The radiation from the plasma 118, the position of the target 115, and other data can be monitored by one or more measurement devices 150, and the information collected by the one or more measurement devices 150 can be used for the control and operation of the EUV source 110.

[0026] Target 115 can be transmitted along at least a portion of its path through target shield 115s. Shield 115s can be in the form of a tube (which may have apertures for measurement) or other shielding structures that shield or partially shield the incoming target 115 from the influence of gases and other materials in the internal volume 114 of source container 111, so that the trajectory of target 115 is not excessively disturbed by such gases or other materials. Unused targets in target 115 (such as targets not converted into plasma 118) can be trapped in target trap 117b.

[0027] Target 115 is or includes EUV emission target materials, such as, but not limited to, tin, lithium, xenon, or combinations thereof. Target 115 may be in the form of droplets, or alternatively, may be solid particles or solid particles contained within droplets. For example, elemental tin may be presented as a target in the following forms: pure tin; tin compounds, such as SnBr4, SnBr2, SnH4; tin alloys, such as tin-gallium alloys, tin-indium alloys; or tin-indium-gallium alloys; or combinations thereof.

[0028] EUV light source 110 may also include a collector 120 that redirects EUV light 119 into redirected EUV light 124. The collector 120 may be a near-normal incident collector mirror having an optical axis coinciding with the optical axis A and a reflecting surface 121. The reflecting surface 121 may be in the form of a prolate spheroid (i.e., an ellipse about its major axis), such that the collector 120 has a first or principal focus 122 within or near the radiant position 116 and a second focus at a so-called intermediate focus 123, the optical axis of which is defined as a line extending along the optical axis A between them. Thus, the source container 111 of the EUV light source 110 at least partially surrounds a volume 114 within which EUV light 119 is redirected (reflected) by the collector 120 along axis A from the principal focus 122 to the intermediate focus 123 into EUV light 124 when the EUV light source 110 and source container 111 are in use. The reflected EUV light 124 from collector 120 can be output from EUV source 110 at intermediate focal point 123 and input to apparatus utilizing EUV light 124, such as photolithography exposure apparatus (e.g., Figure 2 (As shown). The collector 120 is formed with a through-hole 125 through the collector 120 to allow the pulse beam 113 generated by the source laser 112 to pass through the through-hole 125 and reach the radiation station 116. The through-hole 125 creates a shadow or large gap 154 ​​along the optical axis A in the reflected EUV light 124 from the collector 120.

[0029] To reflect EUV light 119, the collector 120 may be in the form of a multilayer mirror (MLM), with the reflective surface 121 having a hierarchical multilayer coating having alternating layers of molybdenum and silicon, and in some cases, one or more high-temperature diffusion blocking layers, smoothing layers, capping layers, and / or etch-stopping layers. Other surface shapes besides an elongated ellipsoid may also be used for the reflective surface 121. For example, the reflective surface 121 may alternatively be in the form of a parabola rotating about its major axis. In implementations, the reflective surface 121 may be configured to deliver an EUV beam 124 with an annular or other cross-section at the intermediate focus 123. In other implementations, the reflective surface 121 may utilize coatings and layers other than those described above.

[0030] The cost of manufacturing collector 120 may be high. The efficiency and power of the light produced by EUV light source 110 depend on the quality of the reflective surface 121 of collector 120. For these and other reasons, it is desirable to protect collector 120 from damage to its reflective surface 121.

[0031] However, collector 120 must be placed within source container 111 within volume 114 and close to plasma 118 in order to collect and redirect EUV light 119. Structures within source container 111 (including collector 120) may be exposed to high-energy ions and / or particles, as well as target material or vapors containing target material. Particles of target material and high-energy ions and vapors (essentially debris or byproducts of light-based vaporization or ablation processes) can contaminate the exposed reflective surface 121 of the collector. Particles of target material and high-energy ions and vapors can also cause physical damage and localized heating to the reflective surface 121 of collector 120.

[0032] like Figure 1A As shown, the EUV light source 110 may include a focusing unit 126, which includes one or more optical elements (not shown) for focusing the beam 113 onto a focal spot or beam waist at or near the radiation station 116.

[0033] Figure 2 This shows an EUV light source 210 with a photolithography exposure apparatus 271 (e.g., Figure 1A The diagram illustrates the implementation of an EUV light source 110 or another EUV light source. A photolithography exposure apparatus 271 receives EUV light 224 generated by the EUV light source 210 and reflects it in one or more illumination mirrors 272 to illuminate a reflective pattern or mask 273. The EUV light reflected from the pattern or mask 273 is further reflected and reduced by one or more reduction mirrors 274 and radiated onto a substrate or wafer 275 (or onto one or more photosensitive layers on the substrate or wafer 275, not shown) to allow the formation of a patterned structure in or on the substrate or wafer 275.

[0034] refer to Figure 1A and Figure 2 The optical elements and sensors within the photolithography exposure apparatus 271, as well as the photosensitive layer on the substrate or wafer 275, are typically sensitive to many types, or even any type, of radiation. Therefore, especially considering the influence of radiation... Figure 1A The high power level generated by the source laser 112 is important to prevent any part of the pulse beam 113 from (including) the source laser 112. Figure 1A The beam 113e shown (corresponding to the portion of beam 113 that extends beyond the radiation station 116) reaches the intermediate focus 123 and potentially enters a photolithography exposure apparatus, such as photolithography exposure apparatus 271.

[0035] Therefore, such as Figure 1AAs shown, beam-blocking elements such as the shielding rod 127 of this disclosure can be used. The shielding rod 127 may include a base 128, a shaft 129 extending from the base 128, and a head 130 supported on the shaft 129. In use of the shielding rod 127, as shown, the head 130 is positioned on axis A such that the optical axis (and optic axis) A intersects with the head 130. Furthermore, the position and size of the head 130 can be configured to accommodate shadows or large gaps 154 in the reflected EUV light 124 from the collector 120. For example, the head 130 may have a cross-section perpendicular to the optical axis A, which is circular and centered on the optical axis A, and matches the shadow or large gap 154. This geometry prevents the head 130 from blocking any EUV light 124 or any significant portion thereof reflected from the collector 120 and directed toward the photolithography exposure apparatus 121, while effectively protecting the intermediate focus 123 from direct irradiation by the pulsed beam 113 of the source laser 112. In other words (regarding its positioning in the shadow or gap 154), the head 130 is positioned such that direct EUV light 119 from the main focus 122 is little or not reflected by the collector 120 to reach the head 130 as EUV light 124.

[0036] In the source container using the target shield 115s, as shown, the axis 129 of the shielding rod 127 can be aligned with the shield 115s, meaning it can be positioned as close as possible to the shadow cast by the shield 115s in the reflected EUV light 124. In other words, when viewed from the main focal point 122 of the collector 120, the image of the axis 129 in the reflection from the collector surface 121 can be aligned with the image of the shield 115s. In some implementations, the axis 129 can be completely hidden in the shadow of the shield 115s, just as when viewed from the main focal point 122 of the collector 120, the image of the axis 129 in the reflection from the collector surface 121 is hidden by the image of the shield 115s. This arrangement reduces or eliminates the reflected EUV light 124 that is blocked from leaving the EUV source 110 by the axis 129.

[0037] The heating gas transfer device 136 may be attached to the head 130 of the shielding rod 127 (or, as shown and described below, form a single piece therewith). As shown below, the head 130 of the shielding rod 127 may be attached to or form a single piece therewith. A gas supply channel 131 connects to the base 128 of the shielding rod 127 and the shaft 129, as well as a gas source 131a, such as hydrogen (H2) 132, to allow the shielding rod 127 to supply heating gas to the internal volume 114 of the source container via the heating gas supply device 136, indicated by arrow HG. The heating gas, indicated by arrow HG, is heated by light received in the heating gas transfer device 136, as shown below. Source laser and EUV light received on the outer surface of the heating gas transfer device 136 will generate some additional heating. Optionally, additional heating may be provided, such as through a heater 131h at or near the gas source 131a and / or gas supply channel 131, as shown, or through resistance heating in the shielding rod 127 and / or shielding rod head 130 or the heated gas transfer device 136, as further described below.

[0038] Figure 1B Figure 1 shows a simplified schematic cross-sectional view of the EUV source 110, rotated 90 degrees about the z-axis to show a cross-section in the yz plane (as shown by the reference coordinate axis), and rotated so that gravity is downward in the page plane. When in use, the EUV source 110 can be tilted relative to gravity as shown, but other orientations are also possible. In this view, the shaft 129 and base 128 of the shielding rod 127 are positioned inside the page behind the head 130. Also in this view, the exhaust port 133 and the associated exhaust opening 155 are visible. As shown, the exhaust port 133 is a structure extending from and defining the exhaust opening 155 from the source container 111, which is in fluid communication with and extends from the interior 114 of the source container 111. Gases and entrained ions, vapors, and debris can be discharged from the source container 111 through the exhaust opening 155 of the exhaust port 133 by one or more vacuum pumps (not shown). Measured along optical axis A, exhaust opening 155 is positioned between collector 120 and head 130.

[0039] like Figure 1B As shown in the implementation, the heated gas delivery device 136 and the head 130 of the shielding rod 127 form a unit. Therefore, in this implementation, the heated gas delivery device 136 includes a surface or “exposed surface” 134 exposed to the main focus 122. The exposed surface 134 may be or may include inclined surfaces 134s, which represent surfaces not perpendicular to axis A, and may generally face the direction of the exhaust opening 155 of the exhaust port 133 and / or the direction of the portion 135 of the inner surface 156 of the source container 111 at the intermediate focusing side of the exhaust opening 155.

[0040] Various gas flows that can be used for the EUV source 110 are indicated by outlined arrows in the figure. Gas flows with pressures ranging from about 50 to about 300 Pascals (Pa), such as hydrogen (H2) flows, can be used as buffer gases for debris and / or vapor control within the source container 111. Considering the need for a vacuum within the interior 114 of the source container 111 to avoid excessive absorption of EUV light 119, 124 by gas molecules, it would be difficult to adequately protect the collector 120 from target material debris and vapor emitted from the irradiation station 116 without the use of such a gas flow. Hydrogen (H2) is relatively transparent to EUV light at a wavelength of about 13.5 nm and is therefore generally superior to other candidate gases, such as helium, argon, and other gases that exhibit higher absorption at about 13.5 nm.

[0041] H2 gas can be introduced into source container 111 to slow down and guide the radiation from radiant station 116 and target 115, as well as the high-energy fragments (ions, atoms, and clusters) of target material generated by the resulting plasma 118. The fragments are slowed down after colliding with gas molecules. The H2 gas flow CF at the central aperture 125 of collector 120 can be used for this purpose. Sometimes referred to as a “cone flow” CF, the flow CF can be guided from the central aperture 125 of collector 120 to radiant station 116, which repeatedly generates plasma 118, by a pipe or nozzle 137, etc. This direction is opposite to the trajectory of the fragments from radiant station 116 toward collector 120, and thus the cone flow CF is used to reduce damage to collector 120 caused by the vapor deposition, injection, and deposition of sputtered target material.

[0042] An airflow, typically referred to as umbrella flow 139, can be guided along the surface of collector 120 (from an outlet not shown). A so-called nozzle flow can be provided in the region of source container 111 closest to collector 120, where gas flows through multiple parallel orifices, such as nozzle flow S1 and nozzle flow S2, typically perpendicular to the surface to be protected. In additional regions, such as the area near intermediate focus 123, protective airflows parallel to or having a flow component parallel to the surface to be protected can be introduced through orifices pointing in a direction having a component along or parallel to the surface to be protected. For example, airflows such as F1, F2, F3, and F4 can be introduced to protect the inner surface 156 of source container 111 in the area near intermediate focus 123.

[0043] An airflow commonly referred to as a dynamic airlock (“DGL”) is one or more airflows used to prevent any material from leaving the EUV source 110 in the area of ​​the intermediate focus 123. A DGL can generate an airflow from the area of ​​the intermediate focus 123 toward the radiation station 116, such as a DGL flow 138, which may also be referred to as an “intermediate focus protection” airflow 138.

[0044] The conical flow CF, umbrella-shaped flow 139, and nozzle-shaped flows S1 and S2 (and optional other flows not shown) can form and maintain a stable debris-containing guide flow 140 exiting from collector 120. The solid curve in Figure 1C illustrates an example boundary of the debris-containing guide flow 140. This guide flow 140 helps to contain and carry material away from collector 120, including vapors, ions, and micron and nanoparticles generated by target 115 during plasma generation 118.

[0045] The reverse flow 141, moving from the central focus 123 toward the collector 120, is primarily formed by the DGL flow 138, heated gas from the heated gas transfer device 136 (arrow HG), and other flows such as streams (“curtain” flows) F1, F2, F3, and F4 (and optional other flows not shown). The curved boundary line 141b, together with the inner surface 156 of the container 111 in the upper part of the figure, represents an example boundary of the reverse flow 141. Heated gas (arrow 143) may also flow from the exposed surface 134 or the exposed inclined surface 134s.

[0046] Given the low pressure used within source container 111, the pressure difference at exhaust opening 155 of exhaust port 133 is not significant. However, the small pressure difference generated at exhaust opening 155 by vacuum pumping exhaust port 133, and the flow momentum balance between the guided flow 140 and the reverse flow 141 at the confluence region 142 of the two flows 140, 141 (where confluence region 142 is close to exhaust opening 155), can generate a stable guided flow that carries and contains target material byproducts into exhaust opening 155, while the target material byproducts essentially do not contact any inner surface of source container 111.

[0047] When using tin or tin-containing targets 115, using hydrogen (such as in a cone flow CF) with such targets 115 can lead to another potential source of contamination in the source container 111. This is because molten tin is ejected or “splashed” from the surface of the container that is coated or to be coated with molten tin when hydrogen bubbles form and grow in or under the molten tin and then burst.

[0048] One method to prevent tin splattering is to prevent molten target material from accumulating on the surface of the source container 110, i.e., keeping the surface below or well below the melting point of the target material, which is approximately 232°C for tin. For example, some portions of the inner surface 156 of the source container 111 can be maintained at temperatures below 232°C, such as 50°C to 110°C or 50°C to 100°C. Any tin deposited on such a surface remains solid, preventing or resisting splattering.

[0049] While reducing splashing, using a "cool" surface also lowers the temperature and increases the density of the gas in the internal volume 114 of container 111. The higher gas density within the internal volume 114 increases the absorption of EUV light, particularly in the generally cooler "upper" region (facing away from the collector 120) that reflects light through the internal volume 114. Figure 1B Reflected EUV light 124 (at the top of the page) Figure 1A ).

[0050] Transferring the heated gas, indicated by arrow HG, from one or more sides of the heated gas transfer device 136 into the internal volume 114 of the container 111, and optionally from the exposed surfaces 134, 134s, can help provide a region 144 (shown by the small dashed boundary) of low-density gas, through which a large portion of the EUV light 124 traveling from the collector 120 to the intermediate focal point 123 can pass. In practice, there is typically no clear boundary between the heated and unheated gas within the internal volume 114; instead, a higher temperature gradient may exist near the heated gas transfer device and the flow indicated by arrow HG. Therefore, Figure 1B The small dashed boundary in region 144 represents an example region with relatively high temperature and low density gas. Therefore, the lower density gas in region 144 reduces the absorption of EUV light 124, which allows for an increase in the brightness of the EUV light generated by EUV source 110 (output EUV light 124), thereby improving the brightness of EUV source 110 and downstream devices (such as lithography device 217). Figure 2 The performance and operating economy of the heated gas transfer device 136 are considered. If desired, the heated gas transfer device 136 can also be used within a container with a "hot" inner surface to obtain similar benefits from the dense gas in the area surrounding the heated gas transfer device 136. The heated gas transfer device 136 may comprise or be formed of a high-temperature metal, such as molybdenum, tungsten, rhenium, and their alloys. Ceramic materials with relatively good electrical conductivity and formability, such as aluminum nitride, may also be used.

[0051] Figure 3A It can be located in Figure 1A or Figure 1B A perspective view of the implementation of the heating gas transfer device 336, which is used as a heating gas transfer device 136 in the EUV light source 110. The view shows... Figure 1B The view of the heating gas transfer device 136 (or shielding rod head 130) corresponds to the heating gas transfer device 336 (or shielding rod head 330), but the z-axis is in Figure 3A To the right in the page plane. Figure 3B The heating gas transfer device 336 and the shielding rod head 330 are relative to Figure 3AA perspective view rotated 90 degrees around the z-axis makes the shielding rod 327 visible as a whole, including the axis 329 and the bottom surface 328 in addition to the head 330. The axis 329 includes facets 352a and 352c (and corresponding facets on the invisible side), such that the axis 329 tapers or narrows in the positive z-axis direction and the negative z-axis direction. Figure 3C It is along Figure 3A The line shown is cut off at 3C-3C. Figure 3A and Figure 3B Cross-sectional view of the heating gas transfer device 336 and the shielding rod 327.

[0052] like Figure 3A , Figure 3B and Figure 3C As shown, the heating gas transfer device 336 (also serving as the head 330 of the shielding rod 327) has a gradually tapering shape in the positive z-direction or (in the...) Figure 1A and Figure 1B The light source (in the middle) tapers gradually along the optical axis A toward the central focal point 123, until it reaches a tip 336t. The outlet 336o in the side surface 336s (the gradually tapered surface) can be used to transfer heated gas into the internal volume of the light source container, such as... Figure 1A and Figure 1B The internal volume 114 of the container 111 of the light source 110. The outlet 336o can be in the form of a circular or near-circular hole, as shown, but can also take other forms, such as a slit and other shapes. The tip 336t can be closed, that is, it can have no outlet. The surface or "exposed surface" 334 is positioned at the negative z-axis extreme of the heated gas transfer device 336 (or Figure 1A and Figure 1B The exposed surface 334 may be or may include an inclined surface 334s, which means not perpendicular to (the principal focus 122). Figure 1A and Figure 1B The surface of axis A.

[0053] like Figure 3B and Figure 3C As further shown, the exposed surface 334 may include one or more inlet openings 336io. When in use, the openings 336io may be accessible from the source laser 112 ( Figure 1A , Figure 1B ) of bundle 113e ( Figure 1A and Figure 3C ) radiation, and can radiate internally RADi ( Figure 3CA portion of the light beam 113e is introduced into the interior 336i of the heated gas transfer device 336 in the form of RADi. The internal RADi radiation radiates the inner surface 336is of the heated gas transfer device 336 to heat the heated gas transfer device 336, and thereby heats the gas, such as hydrogen (H2), transferred by or through the heated gas transfer device 336 to produce heated gas (HG). The inner surface 336 is a gradually tapering inner surface for receiving, absorbing, and partially reflecting the RADi radiation once or multiple times within the interior 336i. In this implementation, the inlet opening 336io in the exposed surface 334 also serves as a gas outlet (flowing out of...) Figures 3A-3C (not shown in the image), and in this implementation, it can take the form of a concentric ring outlet 348c and a hole 348h ( Figure 3B In this implementation, the inner surface 336 irradiated by internal radiation RADi is also the shielding rod head of the inner surface of the gas conduit 347, which extends along and within the shaft 329, and along and within the heated gas delivery device 336 or head 330. Figure 3C ).

[0054] like Figure 3C As shown, the shaft 329 of the shielding rod 330 may optionally include a resistance heating element RHE positioned along the gas conduit 347 to add heat to the passing gas. Unstable heating elements may be additionally or alternatively included in the heated gas delivery device or head 336, 330. A coating or other surface modification 336isc may be included on the inner surface 336is or a portion thereof to reduce the reflectivity of the inner surface such that the reflection of internal radiation RADi is less than the reflection of the unmodified portion of the inner surface 336is. For example, if the reflectivity of the unmodified or uncoated inner surface is greater than 0.9, a coating or other surface modification 336isc may be used to make the reflectivity equal to or less than 0.9. An internal reflectivity equal to or less than 0.9 and the gradually tapering shape of the interior 336i of the heated gas delivery device 336 in the positive z-axis direction (a shape that facilitates multiple reflections within the interior 336i) both contribute to capturing energy from the internal radiation RADi to heat the heated gas delivery device 336.

[0055] Figure 4 It is similar to Figure 3C A cross-sectional view showing another implementation of a heating gas transfer device 436 included as part of a shielding rod 427, the shielding rod having a shaft 429, a bottom surface 428, and a head 430, the head also being the heating gas transfer device 436. Figure 3C Similarly, such as Figure 4 As shown, the heating gas transfer device 436 has a gradually tapering shape, either in the positive z-direction or (in the z-direction). Figure 1A and Figure 1B(In the middle) it gradually tapers along the optical axis A toward the central focal point 123, until the tip 436t ( Figure 4 The outlet 436o in the side surface 436s (the gradually tapering surface) can be used to transfer heated gas into the internal volume of the light source container, such as... Figure 1A and Figure 1B The internal volume 114 of the container 111 of the light source 110. The tip 436t can be closed, that is, it can have no outlet. The surface or "exposed surface" 434 is positioned at the negative z-axis extreme of the heating gas transfer device 436 (or Figure 1A and Figure 1B The exposed surface 434 may be or may include an inclined surface 434s, which means not perpendicular to (the principal focus 122). Figure 1A and Figure 1B The surface of axis A.

[0056] like Figure 4 As further shown, the exposed surface 434 may include one or more inlet openings 436io, one of which is in Figure 4 The cross-section is shown. When in use, the opening 436io can be made from the source laser 112 ( Figure 1A , Figure 1B ) of bundle 113e ( Figure 1A and Figure 4 ) radiation, and can radiate internally RADi ( Figure 4 A portion of the light beam 113e is introduced into the interior 436i of the heated gas transfer device 436 in the form of RADi radiation. The internal radiation RADi radiates the inner surface 436is of the heated gas transfer device 436 to heat the heated gas transfer device 436, and in turn heats the gas transferred by or through the heated gas transfer device 436, thereby generating heated gas HG. In this implementation, one or more inlet openings 436io in the exposed surface 434 are not used as gas outlets. If it is not desired that gas will flow out from the exposed surface 434 (by Figure 4 (An alternative represented by the closed end CE of the gas sub-conduit 447o at the lower end of the exposed surface 434), or if it is desired that gas flows out from the exposed surface 434, but a baffle BF is used to significantly limit or prevent the radiation of beam 113e from reaching the gas conduit or sub-conduit 447p. Figure 4 If the upper end of the exposure surface 434 represents an alternative method, then this implementation can be useful.

[0057] In this implementation, beam 113e can enter one or more internal regions, such as internal region 436i, through one or more associated inlet openings 436io, which allow some light from beam 113e to enter (one or more) internal regions 436i, thereby generating internal radiation RADi. As described above, (one or more) internal regions 436i are not part of the gas conduits within the heated gas delivery device or heads 436, 430. Instead, one or more gas sub-conduits 447o, 447p are supplied from gas conduit 447 positioned within and along shaft 427. Gas sub-conduits 447o, 447p can be opposite sides of a single annular conduit extending along the interior of the outer surface 436s, or can be fluidly connected via one or more annular or semi-annular feed channels, for example, via a single annular or semi-annular feed channel positioned at or near conduit 447 within the heated gas delivery device or heads 436, 430 (not shown).

[0058] Internal radiation RADi irradiates the inner surface of the heating gas transfer device 436, which is in the form of the inner surface 436is of the inner region 436i, thereby heating the heating gas transfer device 436 and heating the gas transferred by or through the heating gas transfer device 436 to generate heated gas HG. A coating or other surface modification 436isc may be included on the inner surface 436is or a portion thereof to reduce the reflectivity of the inner surface, such that the reflection of the internal radiation RADi is less than the reflection of the unmodified portion of the inner surface 436is. For example, if the reflectivity of the unmodified or uncoated inner surface is greater than 0.9, a coating or other surface modification 436isc may be used to make the reflectivity equal to or less than 0.9. An internal reflectivity equal to or less than 0.9 and the gradually tapering shape of the inner region 436i of the heating gas transfer device 436 in the positive z-axis direction (a shape that helps to generate multiple reflections within the inner region 436i) both help to capture energy from the internal radiation RADi to heat the heating gas transfer device 436.

[0059] Figure 5 This includes collector 520 (such as...) Figure 1A and Figure 1B The collector 120) and the heated gas transfer device 536 (such as the collector 120) and the heated gas transfer device 536 Figure 1A and Figure 1B Heating gas transfer device 136 Figures 3A-3C 336, and Figure 4 A cross-sectional view of (436). Some beneficial aspects of the gas heating gas transfer apparatus and method disclosed herein may be partially referred to. Figure 5 To explain.

[0060] The outer and inner peripheries of collector 520 or collector surface 521 define the outer edge or edge ray of the reflected EUV light 524 from the plasma 518 at or near the main focal point 522 of collector 520 reflected in collector surface 521. The EUV light 524 reflected from collector 520 is substantially entirely confined within a first cone, defined by the outer edge of collector 520 or collector reflecting surface 521 as its base and the intermediate focal point 523 as its apex. This first cone may be referred to as a first approximate cone, or may be considered a first slightly truncated cone, since the intermediate focal point effectively covers an area and is therefore not a single point. Figure 5 In the diagram, the cross-section of the first approximate cone is represented by a triangle with vertices A1, B, and C. Similarly, the EUV light 524 reflected from the collector 520 is substantially confined outside the second cone, the second approximate cone, or the second truncated cone. The second approximate cone is defined by the periphery of the through-hole 525 or the inner edge of the collector reflecting surface 521 as its base and the central focal point 523 as its vertex. Figure 5 In the diagram, the cross-section of the second approximate cone is represented by a triangle with vertices A1, D, and E. The second approximate cone corresponds to the section along... Figure 1A The "shadow or huge gap 154" of the optical axis A.

[0061] Although essentially confined there, the intensity of the reflected EUV light 524 from collector 520 is not uniformly distributed within the volume between the first and second cones. To illustrate this, as... Figure 5 As shown, the angles given by BFG and DFG are equal, and therefore essentially direct the EUV light 524, which is leaving the principal focus 522, toward... Figure 5 The left side of collector 520 in the plane is equally divided. However, as shown, the radiation traveling within the BFG angle diffuses more on surface 521 of collector 520 compared to the radiation traveling within the DFG angle. Therefore, after reflection in collector 520, approximately half of the nominal value of the radiation (EUV light 524) from collector 520 is... Figure 5 One half travels within the gray highlighted area, while the other half travels outside the gray highlighted area. Therefore, the gray highlighted area is the concentrated area CR, and the EUV light 524 in the concentrated area CR is more concentrated than the EUV light 524 radially outside the concentrated area CR.

[0062] This concentration effect tends to be enhanced by the properties of the surface 521 of the collector 520. EUV light 524 reflected at a lower angle of incidence (closer to perpendicular to the surface 521, as within the concentration region CR) tends to be reflected more completely (with higher reflectivity) than UV light 524 reflected at a higher angle of incidence (as outside the concentration region CR). Therefore, more than half of the light traveling from the collector 520 to the intermediate focal point 523 typically travels within the relatively radially narrow concentration region CR. By introducing the heated gas HG directly into the concentration region CR (and from there into the surrounding area), gas absorption losses in the concentration region CR are particularly strongly reduced, and the brightness of a given EUV light source 110 can be increased, such as by 1%, 2%, 3%, or 4% or more. To directly transfer the heating gas to the concentrated region CR without impacting the CR and thus not interfering with the transmission of EUV light 524, the outer surface of the heating gas transfer device 536 may be conical, and when the heating gas transfer device 536 is at operating temperature, it may be spaced apart from the surface of the second approximate cone, so that the outer surface of the heating gas transfer device 536 does not encroach on the second approximate cone during operation. For example, the operating temperature of the heating gas transfer device 536 (and heating gas transfer devices 336 and 436) may be in the range of 400°C to 2000°C, 400°C to 1200°C, or 400°C and 800°C. The heating gas transfer device may extend along axis A for a distance ranging from 90 cm to 110 cm or from 95 cm to 105 cm. Alternatively or additionally, the heating gas transfer device may extend along axis A for a distance ranging from 50% to 70% or 55% to 65% of the distance from the main focal point 522 to the intermediate focal point 523. The tip of the heating gas transfer device 536 can extend from the central focal point 523 within 10cm to 25cm, or 10cm to 20cm, or 10cm to 15cm.

[0063] Figure 6 This is a flowchart of method P600 for operating an EUV light source (such as EUV light source 110) according to this disclosure. Figure 6 As shown, method P600 includes an EUV light source 110 ( Figure 1A , Figure 1B ) internal volume 114 ( Figure 1A , Figure 1B Inside, using a self-generated laser ( Figure 1A 112) of light (such as Figure 1A (beam 113) radiating targets (such as) Figure 1A Target 115) to generate EUV emission plasma ( Figure 1A , Figure 1B 118; Figure 5 518)(S10); in internal volume ( Figure 1A , Figure 1B Within 114), along the path of reflected EUV light from the collector ( Figure 1A , Figure 1B 120; Figure 5 The 520) reflection comes from the plasma ( Figure 1A , Figure 1B 118; Figure 5 EUV light (518) Figure 1A , Figure 1B 124; Figure 5 (524)(S20); from the source laser ( Figure 1A 112) of light (such as Figure 1A The beam 113) receives the heated gas transfer device ( Figure 1A , Figure 1B 136; Figures 3A-3C 336; Figure 4 436; Figure 5 (536) refers to the heating gas transfer device ( Figure 1A , Figure 1B 136; Figures 3A-3C 336; Figure 4 436; Figure 5 (S30) heating of 536); and heating of the gas ( Figure 1A , Figure 1B , Figure 3C , Figure 4 and Figure 5 HG) along the reflected EUV light ( Figure 1A , Figure 1B 124; Figure 5 The 524 path from the heating gas transfer device ( Figure 1A , Figure 1B 136; Figures 3A-3C 336; Figure 4 436; Figure 5 536) is transferred to the internal volume ( Figure 1A , Figure 1B (114)

[0064] These implementations can be further described in the following numbered clauses: 1. A system for generating extreme ultraviolet (EUV) radiation, the system comprising: a source container having an internal volume; a source laser configured to generate light entering the internal volume along an optical axis in an incident direction to provide energy to a target, thereby causing EUV generation within the internal volume; and a heating gas delivery device disposed within the internal volume and configured to deliver heating gas into the internal volume, the heating gas delivery device being positioned on and extending along the optical axis, the heating gas delivery device having an outlet for distributing the heating gas into the internal volume and one or more inlet openings for receiving light from the source laser to heat the heating gas delivery device. 2. The system according to Clause 1, wherein the heated gas delivery device further comprises an inner surface having a reflectivity to the light equal to or less than 0.9, for absorbing at least some of the light received from the source laser through the one or more inlet openings. 3. The system according to Clause 1, wherein the heated gas delivery device further comprises a gradually tapering inner surface for receiving, partially reflecting once or multiple times, and at least partially absorbing the light received from the source laser through the one or more inlet openings. 4. The system according to Clause 3, wherein the tapered inner surface includes a tapered inner surface. 5. The system according to Clause 1 further includes a heating gas source connected to the heating gas transfer device to transfer the heating gas to the heating gas transfer device. 6. The system according to Clause 5, wherein the heating gas source is located outside the internal volume. 7. The system according to Clause 1, wherein the heating gas delivery device further includes a gas conduit connected to the outlet. 8. The system according to Clause 1, wherein the heated gas transfer device further includes a heating element configured to heat the heated gas transfer device and / or the gas transferred by the heated gas transfer device. 9. The system according to Clause 1 further includes a collector configured to reflect EUV light generated at or near the primary focal point of the collector to an intermediate focal point of the collector, the collector having an optical axis substantially coincident with the optical axis and a through-hole along the optical axis, the through-hole being configured to allow the light to enter the internal volume such that most or all of the EUV light reflected from the collector travels from the collector to the intermediate focal point within a first approximate cone and outside a second approximate cone, the first approximate cone having a base at the periphery of the collector and an apex at the intermediate focal point, the second approximate cone having a base at the through-hole and an apex at the intermediate focal point, and wherein the heating gas delivery device is disposed within the second approximate cone along the optical axis. 10. The system according to Clause 9, wherein the heating gas transfer device has a conical outer surface that, when the heating gas transfer device is at the operating temperature, is spaced apart from the surface of the second approximate cone such that the outer surface does not impact the second approximate cone during operation. 11. The system according to Clause 9, wherein the heating gas delivery device extends along the optical axis by a distance in the range of 90 to 110 centimeters. 12. The system according to Clause 9, wherein the heating gas delivery device extends along the optical axis by a distance in the range of 50% to 70% of the distance along the optical axis from the principal focal point to the intermediate focal point. 13. The system according to Clause 1, wherein at least some of the outlets of the heating gas transfer device are positioned in the conical outer surface of the heating gas transfer device, the conical outer surface narrowing in the direction along the optical axis and extending away from the direction of the incident light. 14. The system according to Clause 13, wherein the heating gas delivery device extends along the optical axis by a distance in the range of 90 to 110 centimeters. 15. The system according to Clause 13, wherein the heating gas delivery device extends along the optical axis by a distance in the range of 50% to 70% of the distance along the optical axis from the principal focal point to the intermediate focal point. 16. The system according to Clause 13, wherein the tip of the heated gas delivery device extends within 10 to 15 centimeters of the central focal point of the collector. 17. A method for providing extreme ultraviolet (EUV) radiation, the method comprising: irradiating a target with light from a source laser within an internal volume of a source container to generate EUV-generating plasma; generating reflected EUV light within the internal volume by reflecting EUV light from the plasma along a reflected EUV path; receiving light from the source laser into a heated gas transfer device to heat the heated gas transfer device; and transferring heated gas from the heated gas transfer device into the internal volume of the source container along the reflected EUV path. 18. The method according to Clause 17, wherein one side of the heating gas transfer device includes an outlet. 19. The method according to Clause 18, wherein the heated gas delivery device comprises a tapered shape that narrows in the direction toward the central focal point of the collector. 20. The method according to Clause 19, wherein the heating gas delivery device extends in a direction parallel to the optical axis of the source laser for a distance ranging from 90 cm to 110 cm. 21. The method according to Clause 19, wherein the heating gas delivery device extends in a direction parallel to the optical axis of the source laser for 50% to 70% of the distance from the main focal point to the intermediate focal point of the collector.

[0065] The above-described implementations and other implementations are within the scope of the appended claims.

Claims

1. A system for generating radiation, the system comprising: a source vessel having an interior volume; a source laser configured to generate light that enters the interior volume in an incident light direction along an optical axis to provide energy to a target to cause generation of EUV within the interior volume; and a heated gas delivery device disposed within the interior volume and configured to deliver heated gas into the interior volume, the heated gas delivery device positioned on and extending along the optical axis, the heated gas delivery device having one or more inlet openings to receive light from the source laser to heat the heated gas delivery device and an outlet to dispense the heated gas into the interior volume.

2. The system of claim 1, wherein the heated gas delivery device further comprises an interior surface having a reflectivity of equal to or less than 0.9 for the light to absorb at least some of the light received from the source laser through the one or more inlet openings.

3. The system of claim 1, wherein the heated gas delivery device further comprises a tapered interior surface to receive, partially reflect one or more times, and at least partially absorb the light received from the source laser through the one or more inlet openings.

4. The system of claim 3, wherein the tapered interior surface comprises a conical interior surface.

5. The system of claim 1, further comprising a heated gas source connected to the heated gas delivery device to deliver the heated gas to the heated gas delivery device.

6. The system of claim 5, wherein the heated gas source is positioned outside the interior volume.

7. The system of claim 1, wherein the heated gas delivery device further comprises a gas conduit connected to the outlet.

8. The system of claim 1, wherein the heated gas delivery device further comprises a heating element configured to heat the heated gas delivery device and / or gas delivered by the heated gas delivery device.

9. The system of claim 1, further comprising a collector configured to reflect EUV light generated at or near a primary focal point of the collector to an intermediate focal point of the collector, the collector having an optical axis substantially coincident with the optical axis and a through hole along the optical axis, the through hole configured to allow the light to enter the interior volume such that most or all of the EUV light reflected from the collector to the intermediate focal point is inside a first approximate cone having a periphery of the collector as a base and the intermediate focal point as an apex and outside a second approximate cone having the through hole as a base and the intermediate focal point as an apex, and wherein the heated gas delivery device is disposed along the optical axis within the second approximate cone.

10. The system of claim 9, wherein the heated gas delivery device has a tapered outer surface that is spaced apart from a surface of the second approximate cone when the heated gas delivery device is at an operating temperature such that the outer surface does not impinge the second approximate cone when in operation.

11. The system of claim 9, wherein the heated gas delivery device extends along the optical axis a distance in a range of 90 to 110 centimeters.

12. The system of claim 9, wherein the heated gas delivery device extends along the optical axis a distance in a range of 50% to 70% of a distance along the optical axis from the primary focus to the intermediate focus.

13. The system of claim 1, wherein at least some of the outlets of the heated gas delivery device are positioned in a tapered outer surface of the heated gas delivery device that narrows in a direction along the optical axis and extends away from the direction of the incident light.

14. The system of claim 13, wherein the heated gas delivery device extends along the optical axis a distance in a range of 90 to 110 centimeters.

15. The system of claim 13, wherein the heated gas delivery device extends along the optical axis a distance in a range of 50% to 70% of a distance along the optical axis from the primary focus to the intermediate focus.

16. The system of claim 13, wherein a tip of the heated gas delivery device extends within 10 to 15 centimeters of an intermediate focus of the collector.

17. A method for providing extreme ultraviolet (EUV) radiation, the method comprising: radiating a target within an interior volume of a source vessel with light from a source laser to generate an EUV generating plasma; generating reflected EUV light within the interior volume by reflecting EUV light from the plasma along a reflected EUV path; receiving light from the source laser into a heated gas delivery device to heat the heated gas delivery device; and delivering heated gas along the reflected EUV path from the heated gas delivery device into the interior volume of the source vessel.

18. The method of claim 17, wherein a side of the heated gas delivery device includes outlets and the heated gas delivery device includes a tapered shape that narrows in a direction toward an intermediate focus of the collector.

19. The method of claim 18, wherein the heated gas delivery device extends a distance in a direction parallel to an optical axis of the source laser in a range of 90 centimeters to 110 centimeters.

20. The method of claim 18, wherein the heated gas delivery device extends a distance in a direction parallel to an optical axis of the source laser of 50% to 70% of a distance from a primary focus to an intermediate focus of the collector.

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