Inhibitor substances for optical systems

Abstract

An extreme ultraviolet (EUV) light source includes a vessel configured to receive a target material that emits EUV light when in a plasma state, a delivery system configured to deliver radicals to an interior of the vessel, an object in the interior of the vessel, and an inhibitor species. In operational use, the object accumulates debris comprising the target material, the radicals react with at least some of the debris to remove the debris from the object, and the inhibitor species inhibits recombination of the radicals on the object.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Application No. 62 / 941,518, filed November 27, 2019, entitled “INHIBITOR SUBSTANCE FOR ANOPTICAL SYSTEM,” which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to inhibitory substances for use in optical systems. The optical system may be, for example, an extreme ultraviolet (EUV) light source. Background Technology

[0004] Debris may accumulate on objects in an optical system. In some cases, debris can be removed by reacting it with free radicals. The optical system can be an EUV light source. EUV light can be, for example, electromagnetic radiation (sometimes called soft X-rays) with wavelengths of 100 nanometers (nm) or smaller, and light with wavelengths of, for example, 20 nm or smaller, between 5 and 20 nm, or between 13 and 14 nm, can be used in photolithography processes to create extremely small features in a substrate, such as a silicon wafer, by initiating polymerization in a resist layer. Methods for generating EUV light include, but are not limited to, converting materials containing elements such as xenon, lithium, or tin into emission lines in the EUV range in a plasma state. In one such method, commonly referred to as laser-generating plasma (LPP), the desired plasma can be generated by irradiating a target material with an amplified beam, which may be called a driving laser, for example, in the form of droplets, plates, strips, streams, or clusters of material. For this process, the plasma is typically generated in a sealed container (e.g., a vacuum chamber) and monitored using various types of metrological equipment. Summary of the Invention

[0005] In one general aspect, an extreme ultraviolet (EUV) light source includes: a container configured to receive target material that emits EUV light when in a plasma state; a delivery system configured to deliver free radicals into the interior of the container; an object within the interior of the container; and an inhibitory substance. In operational use, the accumulation of debris including target material occurs, the free radicals react with at least some of the debris to remove the debris from the object, and the inhibitory substance inhibits the recombination of free radicals on the object.

[0006] The implementation may include one or more of the following features.

[0007] Inhibitors can include solid-phase inhibitors. Solid-phase inhibitors can be part of an object inside a container. Solid-phase inhibitors can be distributed throughout the object. Solid-phase inhibitors can be on the surface of the object. Inhibitors can occupy catalytic sites on the surface. Solid-phase inhibitors can extend into the bulk region of the object. Solid-phase inhibitors can extend from the surface into the bulk region of the object by no more than about 1 micrometer (μm). The object can include optical elements. The object can include reflective optical elements. The object can include the metal inner wall of the container. The inner wall can include stainless steel, molybdenum, nickel phosphorus, copper, or aluminum. Free radicals can include hydrogen free radicals; the target material can include tin; and the inhibitor can include arsenic, antimony, bismuth, sulfur, selenium, tellurium, beryllium, or cyanide. Inhibitors can also include gaseous inhibitors.

[0008] In some implementations, the inhibitor is a gas-phase inhibitor. Gas-phase inhibitors may include hydrogen sulfide or arsenic.

[0009] The delivery system can also be configured to deliver gaseous inhibitory substances into the interior of the container. The delivery system can also be configured to deliver gaseous inhibitory substances to an object. The gaseous inhibitor can bind to catalytic sites on the surface of the object.

[0010] The object may include a coating on its outer surface, and the inhibitory substance may be contained within the coating. The coating may include an oxide coating or a nitride coating. The coating may include titanium nitride, zirconium nitride, zirconium oxide, aluminum oxide, hafnium oxide, or yttrium oxide.

[0011] In another general aspect, an object in an optical system is exposed to debris, the debris and the object each comprising a corresponding material on which free radicals recombine and / or react; and free radicals are provided to the object to remove at least some of the debris from the object. An inhibitory substance is present simultaneously with the provision of free radicals to the object, and the inhibitory substance inhibits recombination between free radicals on the object, thereby increasing the reaction between the debris and the free radicals.

[0012] The implementation may include one or more of the following features.

[0013] The inhibitory substance can be a solid-phase inhibitory substance added to the object before it is placed in the optical system. Adding an inhibitory substance to an object can include: doping the object with the inhibitory substance, causing the object to react with the inhibitory substance, or bombarding the object with the inhibitory substance.

[0014] The inhibitor can be a gas-phase inhibitor, and the gas-phase inhibitor can be provided to the object. Gas-phase inhibitors can also be provided to the object along with free radicals. Inhibitors can also include solid-phase inhibitors, and solid-phase inhibitors can be added to the object before it is placed in the optical system.

[0015] The optical system may include an extreme ultraviolet (EUV) light source, and the debris may include target material that emits EUV light when in a plasma state.

[0016] In another general aspect, an apparatus for an optical system includes: a host material comprising at least one surface on which free radicals recombine; and a solid-phase inhibitory substance at the at least one surface, the inhibitory substance being configured to inhibit recombination between free radicals at the surface of the material.

[0017] The implementation may include one or more of the following features.

[0018] Solid-phase inhibitors can be extended into the host material.

[0019] Solid-phase inhibitors can be distributed across at least one surface.

[0020] Optical systems may include extreme ultraviolet (EUV) light sources.

[0021] At least one surface may be a coating on the host material. The coating may include an oxide coating or a nitride coating. The coating may also include titanium nitride, zirconium nitride, zirconium oxide, aluminum oxide, hafnium oxide, or yttrium oxide.

[0022] Implementations of any of the above techniques may include EUV light sources, objects containing inhibitory substances, gases containing inhibitory substances, systems, methods, processes, apparatus, or devices. Details of one or more implementations are set forth in the accompanying drawings and the following description. Other features will be apparent from the specification, drawings, and claims. Attached Figure Description

[0023] Figure 1 This is a block diagram of an extreme ultraviolet (EUV) light source.

[0024] Figure 2A It is a three-dimensional view of the object's exterior.

[0025] Figure 2B yes Figure 2A A side cross-sectional view of the object.

[0026] Figures 3 to 6 These are side cross-sectional views of various objects.

[0027] Figure 7 An example graph of EUV light transmittance as a function of the partial pressure of the gas-phase inhibitory substance is shown.

[0028] Figure 8 This is a flowchart of the process for removing debris from an EUV light source.

[0029] Figure 9 This is a block diagram of another EUV light source.

[0030] Figure 10 This is a block diagram of yet another EUV light source. Detailed Implementation

[0031] refer to Figure 1 A block diagram of an extreme ultraviolet (EUV) light source 100 is shown. The light source 100 includes a container 109, a target supply system 140, a delivery system 130, and an inhibitor substance 155 (shown as a triangle). The inhibitor substance 155 promotes the removal of debris 122 (shown as a star) from the object inside the container 109 101, thereby improving the overall performance of the light source 100. The inhibitor substance 155 inhibits the reaction between free radicals 135 (shown as hollow circles) and substances other than debris 122. For example, the inhibitor substance 155 prevents the reaction between free radicals 135 and materials other than debris 122 on the surface of the object, or reduces the reaction rate between free radicals 135 and materials other than debris 122 on the surface of the object. The presence of the inhibitor substance 155 allows for a higher concentration of free radicals 135 to be used in combination with debris 122. As a result, free radicals 135 remove debris 122 from the object at a higher rate, more efficiently, and / or more completely.

[0032] In operation, the target supply system 140 delivers a stream 121 of the target to the interior 101. The interaction between the beam 106 at the plasma generation site 123 and the target material in the target 121p (which is one of the targets in the stream 121) generates a plasma 196 emitting EUV light 197. The target 121p comprises target material, which is any material having an emission line in the EUV range in the plasma state. The target material can be, for example, tin, lithium, or xenon. Other materials can be used as target materials. For example, elemental tin can be used as pure tin (Sn); as tin compounds, such as SnBr4, SnBr2, SnH4; as tin alloys, such as tin-gallium alloys, tin-indium alloys, tin-indium-gallium alloys, or any combination of these alloys.

[0033] Debris 122 is any material capable of accumulating on an exposed surface of an object within the interior 101. For example, debris could be dust and / or metal particles emitted from plasma 196 and / or target 121p. The exposed surface can be on any object within the interior 101. For example, the exposed surface could be surface 181, a reflective optical surface of optical element 104 that interacts with the reflection of beam 106 and plasma 196, and guides EUV light 197 to lithography tool 199. The exposed surface could be an inner wall 103 exposed to plasma 196 and / or reflection of beam 106. The inner wall 103 could be a metallic material, such as, for example, stainless steel, molybdenum, nickel phosphorus, copper, or aluminum. The exposed surface could be an orifice through which gas is supplied to or removed from the interior 101.

[0034] Regardless of the nature of the object, the accumulation of debris 122 can negatively impact the performance of both the object and the light source 100. For example, the presence of debris 122 on the reflective surface 181 may reduce the amount of EUV light 197 reflected by the surface 181, thereby resulting in less EUV light 197 being delivered to the lithography tool 199. In another example, the presence of debris 122 at the aperture may impede the ability to supply gas to or remove gas from the interior 101.

[0035] To reduce or eliminate the accumulation of debris 122, the delivery system 130 delivers free radicals 135 (such as...) Figure 1 (As shown in the circle) is transported to the interior 101. Free radical 135 is an atom, molecule, and / or ion having unpaired valence electrons. Free radical 135 reacts with or combines with debris 122, thereby removing debris 122 from the object. For example, in an implementation where the target material and debris 122 are tin (Sn) and free radical 135 is a hydrogen (H) radical, the reaction between hydrogen free radical 135 and tin debris 122 is:

[0036]

[0037] In this example, a tin (Sn) debris 122 molecule reacts with four hydrogen (H) radicals 135 to form stanane (SnH4) gas. Stanane is a gas desorbed from the surface 181 of the object and expelled from the container 109. The higher the concentration of hydrogen radicals (H), the higher the etching or removal rate of the tin debris 122. However, because radicals 135 are highly reactive, there is a possibility that radicals 135 will combine with something other than debris 122 before having the opportunity to combine with it. For example, in the absence of an inhibitory substance 155, some of the radicals 135 can recombine with other radicals of radicals 135 on the surface 181. Once radicals 135 combine with another substance, they cannot combine with the debris 122 accumulated on the surface 181. In other words, if radicals 135 combine with something other than debris 122, the concentration of radicals 135 available for combination with debris 122 on the surface 181 decreases. To increase the concentration of free radicals 135 available for combination with debris 122, the light source 100 includes an inhibitory substance 155 within its interior 101. The inhibitory substance 155 inhibits or prevents the recombination of free radicals 135 with substances other than debris 122, thereby increasing the concentration of free radicals 135 available for combination with debris 122. Thus, free radicals 135 can remove debris 122 from the surface 181 more completely and at a faster rate and with greater efficiency.

[0038] Inhibitor 155 is any type of material that inhibits the combination of free radical 135 with substances other than debris 122. Inhibitor 155 can be, for example, arsenic, antimony, bismuth, sulfur, selenium, tellurium, beryllium, or cyanide. Inhibitor 155 can be a compound comprising more than one type of material combined with arsenic, antimony, bismuth, sulfur, selenium, tellurium, beryllium, or cyanide.

[0039] The inhibitory substance 155 can be a solid phase and / or a gas phase. In the implementation where the inhibitory substance 155 is a solid phase, the inhibitory substance 155 is on the surface 181 of the object and / or in the main region of the object. Figure 2B , Figure 3 and Figure 4 An example of a solid-phase inhibitor is shown. Figure 5 Examples of gas-phase inhibitory substances are shown. Furthermore, in some implementations, such as... Figure 1 , Figure 6 and Figure 9 The diagram shows the use of solid-phase inhibitors and gas-phase inhibitors.

[0040] Delivery system 130 includes a gas supply system 133. Gas supply system 133 includes a chamber 137 containing a fluid (such as a gas) of free radicals 135 delivered to interior 101. Delivery system 130 delivers free radicals 135 to container 109 via conduit 134. Conduit 134 is a tube or other hollow structure capable of transporting free radicals 135. For example, conduit 134 may be a tube with an inner wall coated or lined with a material that is substantially non-reactive to free radicals 135. Conduit 134 is coupled to container 109 at port 131. Port 131 is fluid-tightened to maintain a vacuum environment within interior 101.

[0041] The gas supply system 133 may include multiple chambers (chamber 137 and another chamber 138) that are not fluidly coupled to each other, but are each configured to be fluidly coupled to the conduit 134 such that gas in either chamber 137 or 138, or gas in both chambers 137 and 138, can be delivered to the interior 101. For example, in an implementation where the inhibitor 155 is a gaseous inhibitor, chamber 137 includes a free radical 135, and chamber 138 includes the inhibitor 155 in the gaseous phase. The gaseous inhibitor 155 may be, for example, hydrogen sulfide (H2S) gas, arsenic (As) gas, or a precursor gas (such as hydrogen arsine (AsH3)).

[0042] The gas supply system 133 also includes a gas management system 139. The gas management system 139 includes means, components, and / or systems configured to direct free radicals 135 and / or gas phase inhibitors 155 to the interior 101. For example, the gas management system 139 may include pumps, flow control devices (such as valves and / or fluid switches), openings through which free radicals 135 flow, and / or nozzles.

[0043] The EUV light source 100 also includes a control system 160, which manages the operation of the delivery system 130, the gas management system 139, and / or the gas supply system 133. For example, the control system 160 can control the flow rate of free radical 135 or inhibitory substance 155 (when in gaseous form) by controlling valves and / or pumps within the gas management system 139. The control system 160 can also be coupled to other systems and components of the EUV light source 100, such as the target supply system 140.

[0044] The control system 160 includes an electronic processing module 161, an electronic storage device 162, and an I / O interface 163. The electronic processing module 161 includes one or more processors (such as general-purpose or special-purpose microprocessors) suitable for executing computer programs, as well as any one or more processors of any kind of digital computer. Typically, the electronic processor receives instructions and data from read-only memory, random access memory (RAM), or both. The electronic processing module 161 can be any suitable type of electronic processor.

[0045] Electronic storage device 162 may be volatile memory (e.g., RAM) or non-volatile memory. In some implementations, electronic storage device 162 includes both non-volatile and volatile portions or components. Electronic storage device 162 may store data and information used in the operation of control system 160. For example, electronic storage device 162 may store information about the operation of delivery system 130. For example, in some implementations, electronic storage device 162 stores the flow rate at which inhibitory substance 155 (when implemented in the gas phase) should flow into interior 101.

[0046] The electronic storage device 162 also stores instructions, such as one or more computer programs, which, when executed, cause the electronic processing module 161 to communicate with the components in the delivery system 130. For example, the electronic storage device 162 may also store instructions that cause the gas management system 139 to control the partial pressure of the inhibitory substance 155 in the interior 101 (when the inhibitory substance 155 is implemented as a gas-phase inhibitor).

[0047] I / O interface 163 is any type of interface that allows control system 160 to receive or send information or data. For example, I / O interface 163 may be a keyboard, mouse, or other computer peripherals that enable an operator to operate and / or program control system 160. I / O interface 163 may include devices that generate perceptible alarms, such as lights or speakers. Furthermore, I / O interface 163 may include communication interfaces, such as a universal serial port (USB), network connection, or any other interface that allows communication with control system 160.

[0048] refer to Figure 2A This shows a three-dimensional view of the exterior of object 280. Object 280 includes solid-phase inhibitor substance 255 ( Figure 2B Inhibitor 255 is inhibitor 155. Figure 1 The implementation of ). Figure 2B It is along Figure 2A The image shows a side cross-section of object 280 taken by line B-B'. Object 280 can be an optical element, such as a reflective optical element 104 (e.g., Figure 1 (as shown) or any other structure within 101. For example, object 280 could be an inner wall 103 (such as...). Figure 1 (As shown).

[0049] Object 280 is a three-dimensional solid structure comprising outer surfaces 281a, 281b, and 281c. Outer surfaces 281a and 281c are substantially flat and generally extend in the XY plane. Outer surface 281b is cylindrical in shape and extends in the Z direction. In other implementations, object 280 may have other shapes. For example, surface 281a may be a curved, concave surface. Figure 2B In the example, surface 281a is oriented toward the source of debris 122. For example, object 280 can be used as a reflective optical element 104 having an outer surface 281a facing the plasma generation site 123. Figure 1 Therefore, although debris 122 can accumulate on any of the surfaces 281a, 281b, 281c, in the example discussed below, debris 122 mainly accumulates on surface 281a.

[0050] Surfaces 281a, 281b, and 281c are adjacent to the body region 282. The body region 282 is the solid interior of the object 280. The body region 282 is defined by the outer surfaces 281a, 281b, and 281c (and any other surfaces forming the exterior of the object 280). The object 280 may be made of a metallic material (such as, for example, stainless steel, molybdenum, nickel phosphorus, copper, or aluminum). The object 280 may be made of a non-metallic material or a material that includes materials other than metals. For example, the object 280 may include a ceramic material. The body region 282 and surfaces 281a, 281b, and 281c may be the same material or may be different materials. For example, surface 281a may be a coating that reflects EUV light and includes an inhibitory substance 255, while the body region 282 may be a metallic material. The inhibitory substance 255 may be added to various coatings (such as, for example, oxide coatings and nitride coatings). To provide a more specific example, inhibitor 255 may be added to any of titanium nitride, zirconium nitride, zirconium oxide, aluminum oxide, titanium oxide, hafnium oxide, and yttrium oxide. A coating having inhibitor 255 may be used as a coating on the body region 282. In these examples, the coating having inhibitor 255 forms surfaces 281a, 281b, and / or 281c.

[0051] exist Figure 2BIn the example, the inhibitor 255 is distributed in the body region 282 and on the surface 281a. The inhibitor 255 may be uniformly distributed throughout the object 280, or the concentration of the inhibitor 255 in some portions of the object 280 may be higher than the concentration in other portions. For example, the object 280 may be manufactured such that the concentration of the inhibitor 255 at the outer surface 281a is greater than the concentration of the inhibitor 255 at any of the other outer surfaces 281b, 281c or in the body region 282.

[0052] The inhibitor 255 can be introduced into the object 280 by, for example, by doping the object 280 with the inhibitor 255, inducing a chemical reaction between the inhibitor 255 and the object 280, performing chemical vapor deposition of the inhibitor 255 onto the object 280, or by bombarding the object 280 with ions of the inhibitor 255. In these implementations, the process of introducing the inhibitor 255 into the object 280 makes the inhibitor 255 part of the object 280. For example, the object 280 can be made of a crystalline material, and the chemical doping process forms a lattice of the inhibitor 255 in the base crystalline material. The inhibitor 255 can be in a non-solid form during the introduction process. However, the inhibitor 255 is in a solid form after being introduced into the object 280.

[0053] Free radical 135 combines with debris 122 to remove debris 122 from surface 281a of object 280. Figure 2B In the diagram, the removal or desorption of debris 122 from surface 281a is shown as a star-shaped object attached to a circle with a dashed arrow. Inhibitor substance 255 is present at or near surface 218a and inhibits or prevents free radical 135 from reacting with other free radicals and / or with other materials at surface 281a. Therefore, the presence of the inhibitor substance increases the ability of free radical 135 to recombine with debris 122 at surface 281a and promotes the removal of debris 122 from the surface.

[0054] Reference Figure 3 The image shows a side cross-sectional view of object 380. This object includes a solid-phase inhibitor substance 355. Inhibitor substance 355 is an inhibitor substance 155 (…). Figure 1 The implementation of ). Object 380 has the same characteristics as object 280 ( Figure 2A The object 380 has essentially the same external shape. It can be an optical element, such as a reflective optical element 104 (e.g., Figure 1 (as shown) or any other structure within 101.

[0055] Object 380 includes outer surfaces 381a, 381b, and 381c. Outer surfaces 381a and 381c are substantially flat and extend in the XY plane. Outer surface 381b is cylindrical in shape and extends in the Z direction. Figure 3 In the example, surface 381a is oriented toward the source of debris 122, such that debris 122 mainly accumulates on surface 381a. Surfaces 381a, 381b, and 381c are adjacent to the main region 382.

[0056] exist Figure 3 In the example, inhibitory substance 355 is distributed in surface region 383 and / or on surface 381a. Surface region 383 is adjacent to surface 381a and extends from surface 381a into body region 382 in the -Z direction. In some implementations, the extension of surface region 383 into body region 382 does not exceed a few micrometers. For example, surface region 383 may extend into body region 382 by about 1 or about 5 micrometers (μm). Inhibitory substance 355 may be uniformly distributed in surface region 383, or the concentration of inhibitory substance 355 in some portions of surface region 383 may be higher than the concentration in other portions. Surface region 383 may be or may include a coating containing inhibitory substance 355. Inhibitory substance 355 may be added to various coatings, such as, for example, oxide coatings and nitride coatings. To provide a more specific example, inhibitory substance 355 may be added to any of titanium nitride, zirconium nitride, zirconium oxide, aluminum oxide, titanium oxide, hafnium oxide, and yttrium oxide.

[0057] As described above, free radicals 135 in surface region 383 combine with debris 122 to remove debris 122 from surface 381a of object 380. The removal or desorption of debris 122 from surface 381a... Figure 3 The star shape attached to the circle is shown with a dashed arrow. Inhibitor substance 355 occupies surface region 383 and inhibits or prevents free radical 135 from reacting with other free radicals and / or other materials at surface 381a. Therefore, the presence of the inhibitor substance increases the ability of free radical 135 to recombine with debris 122 at surface 381a and promotes the removal of debris 122 from the surface.

[0058] Reference Figure 4 The diagram shows a side cross-sectional view of object 480. Object 480 has the same characteristics as object 280. Figure 2A The object 480 has essentially the same external shape. It can be an optical element, such as a reflective optical element 104 (e.g., Figure 1 (as shown) or any other structure within 101.

[0059] Object 480 includes outer surfaces 481a, 481b, and 481c. Outer surface 481b is cylindrical in shape and extends in the Z direction. In the example discussed below, surface 481a is oriented toward the source of debris 122, such that debris 122 primarily accumulates on surface 481a. Surfaces 481a, 481b, and 481c are adjacent to a main body region 482. The main body region 482 is made of a solid-phase material. Outer surfaces 481a and 481c are substantially flat and extend in the XY plane.

[0060] Inhibitor 455 is distributed in catalytic sites 484 on surface 481a. Catalytic sites 484 are also referred to as active sites 484. A catalytic site (or active site) is a region where a substance binds and undergoes a chemical reaction. In the absence of inhibitor 455, free radical 135 recombines with other free radicals or other materials in free radical 135 at catalytic sites 484. However, object 480 includes inhibitor 455 in catalytic sites 484. By including inhibitor 455 in catalytic sites 484, the reaction of free radical 135 with substances other than debris 122 is reduced or eliminated. Therefore, more free radical 135 is available to react with debris 122, and more debris in debris 122 is removed.

[0061] Reference Figure 5 A side cross-sectional view of object 580 is shown. Figure 5 In the example, gas-phase inhibitor 555 is used to inhibit the reaction between free radical 135 and substances other than debris 122. Gas-phase inhibitor 555 is inhibitor 155 ( Figure 1 The implementation of ). Object 580 has the same characteristics as object 280 ( Figure 2A The object 580 has essentially the same external shape. It can be an optical element, such as a reflective optical element 104 (e.g., Figure 1 (as shown) or any other structure within 101. Object 580 includes outer surfaces 581a, 581b, and 581c. Outer surfaces 581a and 581c are substantially flat and extend in the XY plane. Outer surface 581b is cylindrical in shape and extends in the Z direction. Surfaces 581a, 581b, and 581c are adjacent to the body region 582.

[0062] exist Figure 5 In the example, debris 122 accumulates on surface 581a. Debris is removed from surface 581a using inhibitory substance 555 (in the gas phase). Surface 581a is oriented toward the source of debris 122, such that debris 122 mainly accumulates on surface 581a.

[0063] Inhibitor substance 555 can be delivered through delivery system 130 ( Figure 1The gas is directed to object 580. In some implementations, the gas management system 139 controls the flow of the inhibitory substance 555 into the interior 101 such that the inhibitory substance 555 has a uniform flow pattern (e.g., velocity, temperature, and direction) across surface 581a. In some implementations, the gas management system 139 controls the flow of the inhibitory substance 555 such that the flow pattern across surface 581a is non-uniform.

[0064] Free radical 135 combines with debris 122 to remove debris 122 from surface 581a of object 580. The removal or desorption of debris 122 from surface 581a... Figure 5 The star shape attached to the circle is shown with a dashed arrow. The recombination of free radical 135 with substances other than debris 122 is suppressed by gas-phase inhibitor substance 555, and the concentration of free radical 135 available for recombination with debris 122 increases. Therefore, the higher portions of debris 122 on surface 581a are removed.

[0065] Reference Figure 6 The diagram shows a side cross-sectional view of object 680. Object 680 includes a solid-phase inhibitor substance 655s (such as...). Figure 6 (as shown by the equilateral triangle in the image) and exposed to 655g of gaseous inhibitory substance (such as...) Figure 6 (As shown in the inverted triangle in the image). In other words, Figure 6 An example is shown in which both gas-phase inhibitors and solid-phase inhibitors are used.

[0066] Object 680 has the same characteristics as object 280 ( Figure 2A The object 680 has essentially the same external shape. It can be an optical element, such as a reflective optical element 104 (e.g., Figure 1 (As shown) or any other structure within 101. Object 680 includes outer surfaces 681a, 681b, and 681c. Outer surfaces 681a and 681c are substantially flat and extend in the XY plane. Outer surface 681b is cylindrical in shape and extends in the Z direction. Figure 6 In the example, surface 681a is oriented toward the source of debris 122, such that debris 122 mainly accumulates on surface 681a. Surfaces 681a, 681b, and 681c are adjacent to the main region 682.

[0067] The inhibitor 655s, acting as a solid-phase inhibitor, is distributed in the main region 682 and on the surface 681a. The solid-phase inhibitor 655s can be uniformly distributed throughout the object 680, or the concentration of the solid-phase inhibitor 655s in some parts of the object 680 can be higher than the concentration in other parts. The gaseous inhibitor 655g is transported by the delivery system 130 (…). Figure 1 ) Surface 681a of guide object 680.

[0068] Free radical 135 combines with debris 122 to remove debris 122 from surface 681a of object 680. The removal or desorption of debris 122 from surface 681a... Figure 6 The star shape attached to the circle is shown with a dashed arrow. The recombination of free radical 135 with substances other than debris 122 is suppressed by gas-phase and solid-phase inhibitory substances 655, and the concentration of free radical 135 available for recombination with debris 122 increases. Therefore, the higher portions of debris 122 on surface 681a are removed.

[0069] In the realization of inhibitory substances in the gas phase, the inhibitory substances are selected or adjusted to minimize their impact on the transmission of EUV light. Figure 7 Graph 700 shows the percentage of EUV light transmitted as a function of the partial pressure of the gas-phase inhibitory substance inside the vacuum chamber of the EUV light source. Figure 7 The data shown is simulated data. Figure 7 In the example shown, the inhibitor is hydrogen sulfide (H2S) gas. The hydrogen pressure is 1.8 mbar, and the H2S temperature is 200°C. The transmittance percentage shown in graph 700 is the transmittance percentage over a 1-meter path length. If all EUV light is transmitted, the transmittance percentage is 100%. If no EUV light is transmitted, the transmittance percentage is 0%.

[0070] Before the inhibitor is introduced into the vacuum chamber, its partial pressure is zero. In the example shown in graph 700, the EUV light transmittance is approximately 87% before the inhibitor is introduced. When the gaseous inhibitor is present in the vacuum chamber at a partial pressure of 0.02 mbar, the EUV light transmittance is approximately 84%. When the gaseous inhibitor is present in the vacuum chamber at a partial pressure of 0.1 mbar, the EUV light transmittance is approximately 74%. For pressures less than approximately 0.06 mbar, the EUV light transmittance decreases by approximately 6% or less. Therefore, H2S gaseous inhibitors can be added in trace amounts without significantly affecting EUV light transmittance. For example, when the partial pressure of hydrogen sulfide (H2S) inhibitor 155 is less than approximately 6 mbar, the EUV light transmittance decreases by 6% or less.

[0071] refer to Figure 8 The flowchart of process 800 is shown. Process 800 can be used to remove debris from optical components in an EUV light source.

[0072] The object in the optical system is exposed to debris (810). Debris 122 accumulates on the object. In the example discussed below, the optical system is an EUV light source 100 ( Figure 1The object can be an optical element, such as a reflective optical element 104 (e.g., Figure 1 and Figure 9 (as shown), any other structure or object 280 inside 101 of container 109. Figure 2A and Figure 2B As shown), object 380 (e.g.) Figure 3 As shown), object 480 (e.g.) Figure 4 As shown), object 580 (e.g.) Figure 5 (as shown) or object 680 (e.g.) Figure 6 (As shown).

[0073] Free radical 135 is directed to object (820). This object is made of object material. Debris 122 is made of debris material. Object material can be, for example, a metallic material, such as stainless steel, molybdenum, nickel phosphorus, copper, or aluminum. Object material can be a non-metallic material, such as a dielectric coating. Debris material can include, for example, tin, dust, or particles of any type of target material. Free radical 135 is capable of reacting with or combining with both object material and debris material. In other words, free radical 135 can combine with either object material or debris material. However, when free radical 135 combines with debris material, debris 122 is removed. As described above, inhibitory substance 155 reduces or eliminates the reaction of free radical 135 with materials other than debris 122. To facilitate the removal of debris 122, free radical 135 is directed to the object in the presence of inhibitory substance 155.

[0074] In some implementations, inhibitory substance 155 is a solid-phase inhibitory substance added to the object before it is exposed to the EUV light source 100. For example, the object could be object 280 ( Figure 2A and Figure 2B As described above, the inhibitor 255 is introduced into the object 280 by, for example, doping the object 280 with the inhibitor 255 to induce a chemical reaction between the inhibitor 255 and the object 280, thereby performing chemical vapor deposition of the inhibitor 255 onto the object 280, or by introducing the inhibitor 255 into the object 280 by bombarding the object 280 with ions of the inhibitor 155. The addition of the solid-phase inhibitor occurs before the object 280 is mounted in the container 109.

[0075] In other implementations, inhibitory substance 155 is a gaseous inhibitory substance provided to an object having free radical 135. For example, and also referencing Figure 5 The inhibitor substance 555 can be directed to the object 580 by the delivery system 130, and the free radical 135 is also directed to the object 580 by the delivery system 130, so that the inhibitor substance 555 and the free radical 135 coexist at the object 580.

[0076] In another implementation, the inhibitory substance 155 includes a solid-phase inhibitory substance added to the object before it is installed in the EUV light source 100 and a gas-phase inhibitory substance supplied to the object while it is being used in the EUV light source 100. For example, the object may be as follows: Figure 6 The object shown is 680.

[0077] refer to Figure 9 A block diagram of another EUV light source 900 is shown. The EUV light source 900 is similar to the EUV light source 100. Figure 1 Similar to the EUV light source 900, except that the EUV light source includes a gas-phase inhibitor delivery system 950 separate from the free radical delivery system 930. In the EUV light source 900, the control system 160 is coupled to both the gas-phase inhibitor delivery system 950 and the free radical delivery system 930. In the light source 900, the inhibitory substance 955 includes solid-phase inhibitory substances 955s (in... Figure 9 (shown as an equilateral triangle) and 955g of gas-phase inhibitory substance (in) Figure 9 (It is shown as an inverted triangle in the middle).

[0078] The radical delivery system 930 includes a radical gas supply system 933. The radical gas supply system 933 includes a chamber 937 containing a fluid (such as a gas) containing radicals 135. The radical delivery system 930 delivers radicals 135 to an interior 101 via a fluid conduit 934. The fluid conduit 934 is coupled to a container 109 at a port 931. The port 931 is fluid-tight, allowing a vacuum environment to be maintained within the interior 101. The radical gas supply system 933 also includes a radical gas management system 939. The radical gas management system 939 includes flow control devices such as pumps and valves.

[0079] The inhibitor delivery system 950 includes an inhibitor gas supply system 953. The inhibitor gas supply system 953 includes a chamber 957 containing 955g of gaseous inhibitory substance. The inhibitor delivery system 950 delivers the gaseous inhibitory substance 955g to the interior 101 via a fluid conduit 954. The fluid conduit 954 is coupled to the container 109 at a port 951. The port 951 is fluid-tight, allowing a vacuum environment to be maintained within the interior 101. The inhibitor gas supply system 953 also includes an inhibitor gas management system 959. The free radical gas management system 959 includes flow control devices, such as pumps and valves.

[0080] Control system 160 manages the operation of free radical delivery system 930, inhibitor delivery system 950, free radical gas management system 939, inhibitor gas management system 959, free radical gas supply system 933, and / or inhibitor gas supply system 953. For example, control system 160 can control the flow rates of free radical 135 and gaseous inhibitor 955g by controlling valves and / or pumps in free radical gas management system 939 and inhibitor gas management system 959, respectively. Control system 160 can also be coupled to other systems and components of EUV source 900, such as target supply system 140.

[0081] refer to Figure 10 This illustrates the implementation of the LPPEUV light source 1000. The LPPEUV light source 1000 is an EUV light source 100 ( Figure 1 The implementation of the LPPEUV light source 1000 includes one or more of the aforementioned inhibitory substances in the gas phase, solid phase, or both, within the vacuum chamber 1030 of the vacuum chamber 1030. As described above, the inhibitory substances (in the gas phase, solid phase, or both) in the interior 1007 prevent the reaction between free radicals 135 and materials other than debris 122 on the surface of the object, resulting in a higher concentration of free radicals 135 that can be used to combine with debris 122 and more effectively remove debris 122 from the object.

[0082] The LPPEUV light source 1000 is formed by irradiating the target mixture 1014 at the plasma formation region 1005 with an amplified beam 1010 traveling along a beam path toward the target mixture 1014. (Regarding...) Figure 1 The target material in the target of the discussed flow 121 may be or includes a target mixture 1014. The plasma formation region 1005 is located within the interior 1007 of the vacuum chamber 1030. When the amplified beam 1010 strikes the target mixture 1014, the target material within the target mixture 1014 is converted into a plasma state having emission lines in the EUV range. The resulting plasma possesses certain characteristics depending on the composition of the target material within the target mixture 1014. These characteristics may include the wavelength of the EUV light generated by the plasma and the type and amount of debris released from the plasma.

[0083] The light source 1000 includes a driving laser system 1015 that generates an amplified beam 1010 due to population inversion within one or more gain media of the laser system 1015. The light source 1000 includes a beam transport system between the laser system 1015 and a plasma formation region 1005, the beam transport system including a beam transport system 1020 and a focusing assembly 1022. The beam transport system 1020 receives the amplified beam 1010 from the laser system 1015, manipulates and modifies the amplified beam 1010 as needed, and outputs the amplified beam 1010 to the focusing assembly 1022. The focusing assembly 1022 receives the amplified beam 1010 and focuses the beam 1010 onto the plasma formation region 1005.

[0084] In some implementations, laser system 1015 may include one or more optical amplifiers, lasers, and / or lamps for providing one or more master pulses, and in some cases, one or more pre-pulses. Each optical amplifier includes a gain medium capable of optically amplifying the desired wavelength at high gain, an excitation source, and internal optics. The optical amplifier may or may not have a laser mirror or other feedback device forming a laser cavity. Therefore, even without a laser cavity, laser system 1015 produces an amplified beam 1010 due to population inversion in the gain medium of the laser amplifier. Furthermore, if a laser cavity is present to provide sufficient feedback to laser system 1015, laser system 1015 can produce an amplified beam 1010 as a coherent laser beam. The term "amplified beam" encompasses one or more of the following: light from laser system 1015 that is amplified but not necessarily coherently oscillating; light from laser system 1015 that is amplified and is also coherently oscillating.

[0085] The optical amplifier in laser system 1015 may include a filling gas, including CO2, as the gain medium, and may amplify light with wavelengths between approximately 9100 nm and approximately 11000 nm, particularly approximately 10600 nm, with a gain of greater than or equal to 900 times. Suitable amplifiers and lasers used in laser system 1015 may include pulsed laser devices, such as pulsed gas discharge CO2 laser devices that generate radiation at approximately 9300 nm or approximately 10600 nm, for example, with DC or RF excitation, operating at relatively high power (e.g., 10 kW or higher) and high pulse repetition rates (e.g., 40 kHz or higher). The pulse repetition rate may be, for example, 50 kHz. The optical amplifier in laser system 1015 may also include a cooling system, such as water, which may be used when laser system 1015 is operated at higher power.

[0086] The light source 1000 includes a collector mirror 1035 with an aperture 1040 to allow the amplified light beam 1010 to pass through and reach the plasma formation region 1005. The collector mirror 1035 may be, for example, an ellipsoidal mirror having a primary focal point at the plasma formation region 1005 and a secondary focal point (also referred to as an intermediate focal point) at an intermediate position 1045, from which EUV light can be output from the light source 1000 and input to, for example, an integrated circuit lithography tool (not shown). The light source 1000 may also include a hollow conical shroud 1050 (e.g., a gas cone) with an open end, tapering from the collector mirror 1035 toward the plasma formation region 1005 to reduce the amount of plasma-generating debris entering the focusing assembly 1022 and / or the beam transport system 1020, while allowing the amplified light beam 1010 to reach the plasma formation region 1005. For this purpose, an airflow can be provided within the shroud oriented toward the plasma formation region 1005.

[0087] The light source 1000 may also include a main controller 1055 connected to the droplet position detection feedback system 1056, the laser control system 1057, and the beam control system 1058. The light source 1000 may include one or more target or droplet imagers 1060, which provide an output representing, for example, the position of a droplet relative to the plasma formation region 1005, and provide this output to the droplet position detection feedback system 1056. The droplet position detection feedback system 1056 can, for example, calculate the droplet position and trajectory, and based on this trajectory, calculate the droplet position error droplet by droplet or on average. Therefore, the droplet position detection feedback system 1056 provides the droplet position error as input to the main controller 1055. Therefore, the main controller 1055 can, for example, provide laser position, direction, and timing correction signals to the laser control system 1057, which can be used, for example, to control the laser timing circuit, and / or provide laser position, direction, and timing correction signals to the beam control system 1058 to control the shaping and amplified beam position of the beam transport system 1020, so as to change the position and / or focal length of the beam within the chamber 1030.

[0088] The supply system 1025 includes a target material delivery control system 1026, which, in response to a signal from the main controller 1055, is operable to, for example, modify the release point of droplets released by the target material supply device 1027 to correct for errors in the arrival of droplets in the desired plasma formation region 1005.

[0089] Additionally, the light source 1000 may include light source detectors 1065 and 1070 for measuring one or more EUV light parameters, including but not limited to pulse energy, energy distribution as a function of wavelength, energy within a specific wavelength band, energy outside a specific wavelength band, and the angular distribution of EUV intensity and / or average power. Light source detector 1065 generates a feedback signal used by the main controller 1055. The feedback signal may, for example, indicate errors in parameters such as the timing and focusing of laser pulses to properly intercept droplets at the correct position and time for effective and efficient EUV light generation.

[0090] The light source 1000 may also include a guide laser 1075, which can be used to align various segments of the light source 1000 or to facilitate the manipulation of the amplified beam 1010 to the plasma formation region 1005. In conjunction with the guide laser 1075, the light source 1000 includes a measurement system 1024 disposed within a focusing assembly 1022 to sample portions of the light from the guide laser 1075 and the amplified beam 1010. In other implementations, the measurement system 1024 is disposed within a beam transport system 1020. The measurement system 1024 may include optical elements for sampling or redirecting subsets of the light, such optical elements being made of any material capable of handling the power of the guide laser beam and the amplified beam 1010. The beam analysis system is formed by the measurement system 1024 and the main controller 1055, because the main controller 1055 analyzes the sampled light from the guide laser 1075 and uses the information to adjust the components within the focusing assembly 1022 via the beam control system 1058.

[0091] Therefore, in summary, the light source 1000 generates an amplified light beam 1010, which is guided along a beam path to irradiate the target mixture 1014 at the plasma formation region 1005, thereby converting the target material within the mixture 1014 into a plasma that emits light in the EUV range. The amplified light beam 1010 operates at a specific wavelength (also referred to as the driving laser wavelength) determined based on the design and properties of the laser system 1015. Alternatively, the amplified light beam 1010 can be a laser beam when the target material provides sufficient feedback back to the laser system 1015 to generate coherent laser light, or if the driving laser system 1015 includes appropriate optical feedback to form a laser cavity.

[0092] Other aspects of the invention are set forth in the following numbered clauses.

[0093] 1. An extreme ultraviolet (EUV) light source, comprising:

[0094] The container is configured to receive target material that emits EUV light when it is in a plasma state;

[0095] A delivery system is configured to deliver free radicals into the interior of a container;

[0096] Objects inside the container; and

[0097] An inhibitory substance, wherein, during operational use, a mass of debris, including target material, reacts with at least some of the debris with free radicals to remove the debris from the mass, and the inhibitory substance inhibits the recombination of free radicals on the mass.

[0098] 2. EUV light source according to Clause 1, wherein the inhibitory substance includes solid-phase inhibitory substances.

[0099] 3. An EUV light source according to Clause 2, wherein the solid-phase inhibitor is part of the object inside the container.

[0100] 4. An EUV light source according to Clause 3, wherein the solid-phase inhibitory substance is distributed throughout the object.

[0101] 5. An EUV light source according to Clause 2, wherein a solid-phase inhibitory substance is on the surface of the object.

[0102] 6. An EUV light source according to Clause 5, wherein the inhibitory substance occupies catalytic sites on the surface.

[0103] 7. An EUV light source according to Clause 5, wherein the solid-phase inhibitor material extends into the main body region of the object.

[0104] 8. An EUV light source according to Clause 7, wherein the solid-phase inhibitor extends from the surface into the bulk region of the object in an amount not exceeding about 1 micrometer (μm).

[0105] 9. An EUV light source according to Clause 2, wherein the object includes optical elements.

[0106] 10. An EUV light source according to Clause 9, wherein the object includes reflective optical elements.

[0107] 11. An EUV light source according to Clause 2, wherein the object includes the metal inner wall of the container.

[0108] 12. An EUV light source according to Clause 11, wherein the inner wall comprises stainless steel, molybdenum, nickel phosphorus, copper or aluminum.

[0109] 13. An EUV light source according to Clause 2, wherein the free radicals include hydrogen free radicals; the target material includes tin; and the inhibitory substance includes arsenic, antimony, bismuth, sulfur, selenium, tellurium, beryllium, or cyanide.

[0110] 14. EUV light sources according to Clause 2, wherein the inhibitory substances also include gas-phase inhibitory substances.

[0111] 15. An EUV light source according to Clause 1, wherein the inhibitory substance includes a gas-phase inhibitory substance.

[0112] 16. An EUV light source according to Clause 1, wherein the delivery system is further configured to deliver a gaseous inhibitory substance into the interior of the container.

[0113] 17. An EUV light source according to Clause 16, wherein the delivery system is configured to deliver a gas-phase inhibitory substance to an object.

[0114] 18. An EUV light source according to Clause 17, wherein a gas-phase inhibitor binds to catalytic sites on the surface of an object.

[0115] 19. EUV light source according to Clause 15, wherein the gas phase inhibitor includes hydrogen sulfide or arsenic.

[0116] 20. An EUV light source according to Clause 1, wherein the object comprises a coating on an outer surface and an inhibitory substance is contained within the coating.

[0117] 21. An EUV light source according to Clause 20, wherein the coating includes an oxide coating or a nitride coating.

[0118] 22. An EUV light source according to Clause 21, wherein the coating comprises titanium nitride, zirconium nitride, zirconium oxide, aluminum oxide, titanium oxide, hafnium oxide or yttrium oxide.

[0119] 23. A method comprising:

[0120] Exposing an object in an optical system to debris, where both the debris and the object comprise corresponding materials on which free radicals recombine and / or react; and

[0121] A free radical is provided to an object to remove at least some debris from the object, wherein an inhibitory substance is present at the same time the free radical is provided to the object, and the inhibitory substance inhibits recombination between free radicals on the object, thereby increasing the reaction between debris and free radicals.

[0122] 24. The method according to Clause 23, wherein the inhibitory substance is a solid-phase inhibitory substance added to the object before it is placed in the optical system.

[0123] 25. The method according to Clause 24, wherein adding an inhibitory substance to an object comprises: doping the object with the inhibitory substance, causing the object to react with the inhibitory substance, or bombarding the object with the inhibitory substance.

[0124] 26. The method according to Clause 23, wherein the inhibitory substance is a gaseous inhibitory substance, and the method further comprises: providing the gaseous inhibitory substance to the object.

[0125] 27. The method according to Clause 26, wherein the gas-phase inhibitor is provided to the object together with the free radical.

[0126] 28. The method according to Clause 27, wherein the inhibitory substance further includes a solid-phase inhibitory substance, and the solid-phase inhibitory substance is added to the object before the object is in the optical system.

[0127] 29. The method according to Clause 23, wherein the optical system includes an extreme ultraviolet (EUV) light source, and the debris includes target material that emits EUV light when in a plasma state.

[0128] 30. An apparatus for an optical system, the apparatus comprising:

[0129] The host material includes at least one surface, which is a surface where free radicals recombine; and

[0130] A solid-phase inhibitory substance, wherein at at least one surface, the inhibitory substance is configured to inhibit recombination between free radicals at the surface of the material.

[0131] 31. The device according to Clause 30, wherein the solid-phase inhibitory substance extends into the host material.

[0132] 32. The device according to Clause 30, wherein a solid-phase inhibitory substance is distributed on at least one surface.

[0133] 33. The device pursuant to Clause 30, wherein the optical system includes an extreme ultraviolet (EUV) light source.

[0134] 34. The equipment pursuant to Clause 30, wherein at least one surface is a coating on the body material.

[0135] 35. Equipment pursuant to Clause 34, wherein the coating comprises an oxide coating or a nitride coating.

[0136] 36. Equipment pursuant to Clause 35, wherein the coating comprises titanium nitride, zirconium nitride, zirconium oxide, aluminum oxide, titanium oxide, hafnium oxide, or yttrium oxide.

[0137] Other implementations are within the scope of the claims.

Claims

1. An extreme ultraviolet (EUV) light source, comprising: A container is configured to receive target material that emits EUV light when in a plasma state; A delivery system is configured to deliver free radicals into the interior of the container; The object is inside the container; as well as An inhibitory substance, wherein, in operational use, the object accumulates debris, the debris comprising the target material, the free radicals react with at least some of the debris to remove the debris from the object, and the inhibitory substance inhibits the recombination of the free radicals on the object. The inhibitory substances mentioned above include gas-phase inhibitory substances.

2. The EUV light source according to claim 1, wherein the inhibitory substance further includes a solid-phase inhibitory substance.

3. The EUV light source according to claim 2, wherein the solid-phase inhibitor is part of the object inside the container.

4. The EUV light source according to claim 3, wherein the solid-phase inhibitor is distributed throughout the object.

5. The EUV light source according to claim 2, wherein the solid-phase inhibitor material is on the surface of the object.

6. The EUV light source according to claim 5, wherein the inhibitory substance occupies catalytic sites on the surface.

7. The EUV light source according to claim 5, wherein the solid-phase inhibitor extends into the body region of the object.

8. The EUV light source of claim 7, wherein the solid-phase inhibitor extends from the surface into the main region of the object by no more than about 1 micrometer (μm).

9. The EUV light source according to claim 2, wherein the object includes optical elements.

10. The EUV light source of claim 9, wherein the object comprises a reflective optical element.

11. The EUV light source of claim 2, wherein the object comprises the metal inner wall of the container.

12. The EUV light source according to claim 11, wherein the inner wall comprises stainless steel, molybdenum, nickel phosphorus, copper or aluminum.

13. The EUV light source according to claim 1, wherein the free radicals include hydrogen free radicals; the target material includes tin; and the inhibitory substance includes arsenic, antimony, bismuth, sulfur, selenium, tellurium, beryllium, or cyanide.

14. The EUV light source of claim 1, wherein the delivery system is further configured to deliver the gas-phase inhibitory substance into the interior of the container.

15. The EUV light source of claim 14, wherein the delivery system is configured to deliver the gas-phase inhibitory substance to the object.

16. The EUV light source of claim 15, wherein the gas phase inhibitor binds to catalytic sites on the surface of the object.

17. The EUV light source according to claim 1, wherein the gas phase inhibitor comprises hydrogen sulfide or arsenic.

18. The EUV light source of claim 2, wherein the object comprises a coating on its outer surface, and the inhibitory substance is contained within the coating.

19. The EUV light source according to claim 18, wherein the coating comprises an oxide coating or a nitride coating.

20. The EUV light source according to claim 19, wherein the coating comprises titanium nitride, zirconium nitride, zirconium oxide, aluminum oxide, titanium oxide, hafnium oxide, or yttrium oxide.

21. A method comprising: Exposing an object in an optical system to debris, the debris and the object each comprising a corresponding material on which free radicals recombine and / or react; as well as Free radicals are provided to the object to remove at least some of the debris from the object, wherein an inhibitory substance is present simultaneously with the provision of the free radicals to the object, and the inhibitory substance inhibits recombination between the free radicals on the object, thereby increasing the reaction between the debris and the free radicals. The inhibitory substance includes a gas-phase inhibitory substance, and the method further includes providing the gas-phase inhibitory substance to the object.

22. The method of claim 21, wherein the inhibitory substance further comprises a solid-phase inhibitory substance added to the object before the object is placed in the optical system.

23. The method of claim 22, wherein adding the inhibitory substance to the object comprises: The object is doped with the inhibitory substance to cause the object to react with the inhibitory substance, or the object is bombarded with the inhibitory substance.

24. The method of claim 21, wherein the gas-phase inhibitor is provided to the object together with the free radical.

25. The method of claim 24, wherein the inhibitory substance further comprises a solid-phase inhibitory substance, and the solid-phase inhibitory substance is added to the object before the object is placed in the optical system.

26. The method of claim 21, wherein the optical system comprises an extreme ultraviolet (EUV) light source, and the debris comprises a target material that emits EUV light when in a plasma state.

27. An apparatus for an optical system, the apparatus comprising: The main material includes at least one surface, said at least one surface being a surface where free radicals recombine; as well as An inhibitory substance, at said at least one surface, is configured to inhibit recombination between said free radicals at the surface of the material. The inhibitory substances include solid-phase inhibitory substances and gas-phase inhibitory substances.

28. The device of claim 27, wherein the solid-phase inhibitor extends into the host material.

29. The device of claim 27, wherein the solid-phase inhibitor is distributed throughout the at least one surface.

30. The device of claim 27, wherein the optical system comprises an extreme ultraviolet (EUV) light source.

31. The device of claim 27, wherein the at least one surface comprises a coating on the body material.

32. The device of claim 31, wherein the coating comprises an oxide coating or a nitride coating.

33. The device of claim 32, wherein the coating comprises titanium nitride, zirconium nitride, zirconium oxide, aluminum oxide, titanium oxide, hafnium oxide, or yttrium oxide.

Images