JP2021517662A - Spatial modulation of light beam - Google Patents

Abstract

The system is a spatially modulated device configured to interact with the light beam to create a modified light beam, which is non-uniform along the direction perpendicular to the direction of propagation of the modified light beam. A spatially modulated device comprising a spatial pattern of light with intensity, the spatial pattern of light comprising one or more components of light, and a target feeding system configured to provide a target to a target region, the target. Includes a target supply system that includes a target material that emits EUV light when in a plasma state. The target region overlaps the beam path such that at least some of the components of one or more light in the modified beam interact with a portion of the target. [Selection diagram] Fig. 1

Description

Cross-reference of related applications
[0001] The present application claims priority to US application No. 62 / 651,928 filed April 3, 2018, which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to techniques for spatially modulating a light beam. This technique can be used, for example, in extreme ultraviolet (EUV) light sources. The light beam can be, for example, a light beam that illuminates the target material or fuel material.

[0003] Extreme ultraviolet (EUV) light, eg, electromagnetic radiation (sometimes including light having a wavelength of 100 nanometers (nm) or less and having a wavelength of, for example, 20 nm or less, between 5 and 20 nm, or between 13 and 14 nm. , Also called soft X-rays) can be used in a photolithography process to initiate polymerization in a resist layer to produce extremely small features in a substrate, such as a silicon wafer.

[0004] Methods for producing EUV light include, but are not limited to, converting the target material into a plasma that emits EUV light. Target materials include elements with emission lines within the EUV range, such as xenon, lithium, or tin. In one of these methods, an amplified light beam, which can be called a drive laser, can be used to irradiate a target containing the target material to generate the required plasma, often called a laser-generated plasma (“LPP”). .. For this process, the plasma is typically generated in a closed container, eg, a vacuum chamber, and monitored using various types of metrology equipment. The target material can be in the form of droplets, plates, tapes, streams, or clusters.

[0005] In one general aspect, the system is a spatially modulated device configured to interact with the light beam to create a modified light beam, which is the direction of propagation of the modified light beam. A spatially modulated device that contains a spatial pattern of light with non-uniform intensity along the direction perpendicular to, and the spatial pattern of light contains one or more components of light, and is configured to provide a target to the target region. A targeted supply system, wherein the target comprises a target material that emits EUV light when in a plasma state. The target region overlaps the beam path such that at least some of the components of one or more light in the modified beam interact with a portion of the target.

[0006] Examples can include one or more of the following mechanisms: The spatial modulation device can be a diffractive optical element. The diffractive optical system can be a spatial light modulator (SLM), adaptive optics, reticle, and / or lattice. The spatial modulation device can be a refraction optical element. Refractive optics can be lenses, small lens arrays, and / or reticle.

[0007] The spatial pattern of light can include two or more light components, each of which has substantially the same intensity. The spatial pattern of light can include two or more light components arranged in a linear grid. The spatial modulation device can include at least one Daman grid.

[0008] The spatial modulation device can also be configured to interact with the second light beam to create a second modified light beam, the second modified light beam of the second modified light beam. It contains a second light spatial pattern having non-uniform intensity along the direction perpendicular to the propagation direction, and the second light spatial pattern contains one or more second light components.

[0009] In some embodiments, the system has a first light generator configured to emit a light beam and a second light generator configured to emit a second light beam. Also includes modules.

[0010] In another general embodiment, the method of forming a target for an extreme ultraviolet (EUV) light source is to direct the light beam onto the beam path and on the beam path to form a modified light beam. By interacting a light beam with a spatially modulated device positioned in, the modified light beam contains a spatial pattern of light with non-uniform intensity along the direction perpendicular to the direction of propagation of the modified light beam. The spatial pattern of light is the interaction of a light beam containing one or more components of light, and the interaction of a modified light beam with a target containing a target material that emits EUV light when in a plasma state. including. At least some of the light components of one or more of the spatial patterns interact with a region of the target to modify the properties of that region of the target.

[0011] Examples can include one or more of the following mechanisms: The property can be a density, and in these examples, modifying the property involves reducing the density. The property can be the surface area of the target, and in these examples, modifying the property of any part of the target involves increasing the surface area of the entire target. The amount of increase in surface area can be related to the number of light components in the modified light beam.

[0012] The spatial pattern of light can include two or more components of light. All light components can have the same intensity. The light component can be placed in the grid, and the target region that interacts directly with the light component can be placed in the grid. The light components are spatially separated and spatially discrete so that some of the targets between any two light components do not interact with any of the components in the modified light beam. It is possible to be.

In some embodiments, the method further comprises interacting the modified beam with the focus assembly before the modified light beam interacts with the target.

[0013] In some embodiments, the method further comprises interacting the initial target with a second light beam to form a modified target, the modified target being the initial target in the first direction. It has a larger range, a smaller range in the second direction than the initial target, and the first and second directions are orthogonal to each other. In these examples, interacting the modified light beam with a target containing a target material that emits EUV light when in a plasma state comprises interacting the modified light beam with the modified target. Each of the above light components interacts with a region of the modified target to modify the properties of that region of the modified target. Further, in some embodiments, after the modified light beam interacts with the modified target, the modified target interacts with a third light beam, which is at least the target material in the modified target. It has enough energy to convert some into plasma that emits EUV light.

The method can also include interacting the target with a modified light beam and then interacting with another light beam, the other light beam being within the second modified target. It has enough energy to convert at least a portion of the target material into a plasma that emits EUV light. The light beam and other light beams can be connected in time and can be part of a single pulse of light. Properties can include conversion efficiencies with respect to the amount of EUV light emitted and the energy of other light beams, and modifying the properties of some of the targets increases the conversion efficiencies associated with the entire target. including.

[0015] Interacting a modified light beam with a target containing a target material that emits EUV light when in a plasma state comprises interacting the modified light beam with a target having a substantially spherical shape. Can be done.

An embodiment of any of the above techniques can include an EUV light source, a system for an EUV light source, a non-temporary electronic storage medium, a method, a process, a device, or an apparatus. Details of one or more embodiments are shown in the accompanying drawings and the description below. Other mechanisms will be apparent from the description and drawings, and from the claims.

[0017] It is a block diagram which shows an example of an EUV light source. [0018] It is a graph which plotted the intensity of an example of an optical beam as a function of the position along the direction perpendicular to the direction of propagation before spatial modulation. [0019] It is a graph which plotted the intensity of the light beam of FIG. 1B as a function of the position along the direction perpendicular to the direction of propagation after spatial modulation. [0020] FIG. 2 is a block diagram showing an example of a target interacting with the light beam of FIG. 1C. [0021] It is a block diagram which shows another example of the EUV light source. [0022] FIG. 2 is a block diagram showing another example of a target. [0023] FIG. 5 is a graph plotting the intensity of another example of a light beam as a function of position along a direction perpendicular to the direction of propagation after spatial modulation. [0024] It is a block diagram which shows an example of a correction target. [0025] It is a figure which shows the example of the light pattern in a target area. [0025] It is a figure which shows the example of the light pattern in a target area. [0025] It is a figure which shows the example of the light pattern in a target area. [0026] FIG. 3 is a block diagram showing an additional example of an EUV light source. [0026] FIG. 3 is a block diagram showing an additional example of an EUV light source. [0026] FIG. 3 is a block diagram showing an additional example of an EUV light source. [0026] FIG. 3 is a block diagram showing an additional example of an EUV light source. [0027] It is a figure which shows the target area with time. [0028] FIG. 6 shows the intensity of light in the target region of FIG. 7 over the time scale of FIG. [0029] It is a block diagram which shows an example of a lithography apparatus. [0030] It is a block diagram which shows an example of the EUV lithography system. [0031] It is a block diagram which shows an example of an EUV light source.

[0032] Disclose a technique for spatially modulating a light beam. The spatially modulated light beam is used to irradiate the target material or fuel material.

[0033] With reference to FIG. 1A, a side view of the extreme ultraviolet (EUV) light source 100 is shown. The EUV light source 100 includes a light generation module 105 that emits a light beam 106 onto a beam path 107 and towards a spatial modulation device 120 that includes a modulation element 122. The interaction between the modulation element 122 and the light beam 106 forms the modified light beam 132. The modified light beam 132 interacts with the target 140 in the target region 142. The light beam 106 can be a pulsed light beam containing pulses of light that are temporally separated from each other. In these examples, the modified light beam 132 is also a pulsed light beam.

[0034] Target 140 includes a target material or fuel material that emits EUV light in a plasma state. The target material contains the target material and may also contain impurities such as non-target particles. The target substance is a substance that is converted into a plasma state having a emission line in the EUV range. The target material can be, for example, water, tin, lithium, xenon, or any material that has a emission line within the EUV range when converted to a plasma state. For example, the target material may be a tin compound such as pure tin (Sn), such as SnBr ₄ , SnBr ₂ , SnH ₄ , a tin alloy, such as a tin gallium alloy, a tin indium alloy, a tin indium gallium alloy, or any combination of these alloys. As a usable element, tin can be used. In the absence of impurities, the target material contains only the target material.

The target 140 can take any form of conductivity with respect to the product of the plasma emitting EUV light. The target 140 is, for example, a liquid or molten metal droplet, a part of a liquid stream, a solid particle or cluster, a solid particle contained in the droplet, a foam of a target material, or a solid particle contained in a part of the liquid stream. Can be. The target 140 can take other forms. For example, the target 140 can be a continuous division of molten metal in a substantially disc shape. The target 140 can be a collection of particles that substantially occupy a disc-shaped volume or a hemispherical volume. Target 140 is a continuous segment of target material that has no gaps or voids, mist of nanoparticles or microparticles, or cloud of atomic vapors.

[0036] The technique relates to spatially modulating the light beam 106 before the light beam interacts with the target 140. Spatial modulation of the light beam 106 can lead to improved conversion efficiency (CE) and / or reduced debris generation, as discussed below.

[0037] Modulation element 122 is an optical element capable of spatially modulating the light beam 106 to form the modified light beam 132. The modulation element 122 can be a diffractive optical element having an arbitrary structure capable of modulating the light beam 106 by diffraction. Diffractive optics are, for example, lattices, spatial light modulators (SLMs), acousto-optic modulators (AOMs), acousto-optic deflectors (AODs), apertures arranged in a plane to create a particular diffraction pattern, or It can be a set of diffractions and / or reticle. The modulation element 122 can be a refraction optic such as a two-dimensional array of lenses or another lens arrangement, a phase plate, a deformable mirror, and / or a refraction reticle. Modulation element 122 can include a plurality of instances of a particular type of modulation element or a collection of various different modulation elements. In these examples, more complex spatial modulation can be achieved by combining the effects of multiple modulation elements. For example, two identical diffraction gratings are placed in series on the beam path 107 to center the beam path 107 with respect to each other in order to form a more complex diffraction pattern corresponding to the more complex spatial modulation of the light beam 106. It is possible to rotate to. In some embodiments, the modulation element 122 comprises both refraction and diffraction optics. Further, the modulation element 122 can be any kind of adaptive optics system such as a deformable mirror.

[0038] Further, the modulation element 122 can be static or dynamic. The static modulation element is such that the structure of the modulation element 122 is fixed at the time of manufacture of the modulation element 122 and is not changed after the modulation element 122 is formed. The dynamic modulation element is capable of modifying or adjusting the spatial modulation provided by the interaction between the light beam 106 and the modulation element 122 during the useful life of the modulation element 122. For example, the spatial modulation provided by the AOM on the incident light beam depends on the characteristics of the acoustic wave propagating in the medium (such as quartz) through which the incident light beam passes. Therefore, it is also possible to change the modulation characteristics provided by the AOM by changing the amplitude and / or period of the acoustic wave. Therefore, AOM can be regarded as a dynamic modulation element. SLM can also be used as a dynamic modulation element. Deformable mirrors or any other type of adaptive optics can also be used as dynamic modulation elements. On the other hand, small lens arrays and blazed gratings made from traditional or conventional refraction and / or reflective materials, whose optical and mechanical properties are not intended to be changeable by the end user, This is an example of a static modulation element.

[0039] Due to spatial modulation, the spatial profile of the modified light beam 132 is different from the spatial profile of the optical beam 106. The spatial profile of a light beam is a characteristic (eg, intensity and / or phase) of the light beam as a function of position along a direction in a plane perpendicular to the propagation direction. Therefore, the modified light beam 132 can have a different intensity and / or phase profile than the light beam 106. The profile characteristics of the modified light beam 132 depend on the characteristics and / or arrangement of the modulation element 122. For example, in an embodiment where the modulation element 122 is a grating, the angle at which the diffraction order propagates away from the modulation element 122 (and thus the position of the diffraction order in the target region 142) is the spacing between the grooves on the diffraction element. Depends on.

[0040] In the example of FIG. 1A, the light beam 106 and the modified light beam 132 propagate generally along the Z direction. FIG. 1B is a graph in which the intensity of the light beam 106 is plotted (in arbitrary units) as a function of the position along the direction X perpendicular to the direction Z. FIG. 1C is a graph in which the intensity of the modified light beam 132 is plotted (in arbitrary units) as a function of position along direction X in the target region 142. In the example of FIGS. 1A to 1C, the intensity profile of the light beam 106 is substantially Gaussian. The intensity profile of the modified light beam 132 differs from the intensity profile of the light beam 106 due to the interaction between the light beam 106 and the modulation element 122. The intensity profile shown in FIG. 1C is along a single line in the XY plane. The intensity profile of the modified light beam 132 in the XY plane at the other lines along the X direction can be the same as or different from the intensity profile shown in FIG. 1C. In other words, the spatial profile of the modified light beam 132 is variable along the X direction, along the Y direction, or along both the X and Y directions.

[0041] The nature of the spatial profile of the modified light beam 132 depends on the configuration of the modulation element 122. For example, in the modified light beam 132, as in the example shown in FIG. 1C, the intensity of the modified light beam 132 continuously fluctuates as a function of the position in the XY plane and without a region containing no light. Can have a profile to do. In some embodiments, the modified light beam 132 is formed of discrete components separated from each other so that the profile of the modified light beam 132 includes a region that is substantially free of light. An example of such a modified light beam is shown in FIG. 2C. In any case, the profile of the modified light beam 132 is different from the profile of the light beam 106 due to the interaction between the modulation element 122 and the light beam 106.

[0042] The modified light beam 132 illuminates the target 140. The intensity profile of the modified light beam 132 shown in FIG. 1C interacts with the target 140 at line CC'(FIG. 1D). Since the spatial profile of the modified light beam 132 is different from the profile of the light beam 106, the modified light beam 132 interacts with the target 140 in a different manner than the light beam 106. For example, the modified light beam 132 provides more light relative to the portions 140a and 140c near the outer edge of the target 140 than the portion 140b near the center of the target 140 as compared to the light beam 106.

[0043] As discussed below, the modulation element 122 can be used to adjust the spatial profile of the light interacting with the target 140 to consume more target material within the target 140. .. This in turn increases the amount of EUV light produced from the interaction between the modified light beam 132 and the target 140 and / or, as a result, emits EUV light from the target material within the target 140. The target 140 will be prepared more effectively before interacting with another light beam that transforms into plasma. Further, by increasing the amount of target material consumed, the use of the modified light beam 132 also reduces the debris produced by the interaction between the target 140 and the light beam.

[0044] Further, the modulation element 122 can be configured such that the modified light beam 132 has a profile that is optimized based on known, hypothesized, or estimated target characteristics. For example, the target 140 may be known to contain more target material near the lower edge of the target 140 than near the center or upper edge. For such targets, the modulation element 122 can be configured to generate a modified light beam with a spatial profile as shown in FIG. 1C.

In the example of FIG. 1A, only a single light beam 106 is shown. However, the light source 100 can use a plurality of light beams, each of which can interact with a differently shaped target 140. For example, the light source 100 modifies one or more properties of the target 140 by shaping, changing the density, or otherwise (without necessarily producing a plasma that emits EUV light). A "prepulse" light beam can be used to generate a modified or intermediate target. These examples can also use a "main pulse" light beam that has sufficient energy to convert the target material in the modified or intermediate target into a plasma that emits EUV light. FIGS. 3, 4, and 6 show an example of the EUV light source 100 using a plurality of pulsed light beams. Any or all of the light beams used within the EUV light source 100 can interact with the modulation element 122 to modify the spatial profile of the light beam. In an embodiment where the light source 100 uses a plurality of light beams, the light source 100 can include more spatial modulation devices 120. For example, in these examples, the light source 100 can include a separate spatial modulation device 120 positioned to interact with each of the plurality of light beams.

[0046] With reference to FIG. 2A, a side view of the EUV light source 200 is shown. The EUV light source 200 is an example of an embodiment of the EUV light source 100 (FIG. 1A).

The EUV light source 200 includes a modulation device 220. The modulation device 220 includes a modulation element 222 that spatially modulates the light beam 106 to generate a modified light beam 232, each containing a component 233 (FIG. 2B) that is also a light beam. Component 233 is separated from each other such that a light-free (or significantly light-reduced) region is between each component and its neighbors. The modified light beam 233 contains many individual components, and the individual components are collectively referred to as component 233. Components 233a, 233b, 233c, 233d, 233e are shown in FIG. 2A. The modulation element 222 can be a diffraction grating. In these examples, each component 233a, 233b, 233c, 233d, 233e is a diffraction order. Component 233c can be of zero order not diffracted by the modulation element 222. In these examples, component 233c generally propagates in the same direction as the light beam 106. In the example of FIG. 2A, each of the components 233a, 233b, 233c, 233d, 233e propagates away from the grating and in different directions.

[0048] The modified light beam 232 also includes other components that use the components 233a, 233b, 233c, 233d, and 233e to form a two-dimensional lattice pattern in the XY plane in the target region 242. FIG. 2B shows a target region 242 in the XY plane. In FIG. 2B, the black circles represent the component 233 within the target region 242. In the example of FIG. 2B, all of the components 233 interact with their respective parts of the target 140. The element labeled 243 represents the portion that interacts with component 233a. For simplicity, only one portion 243 is marked in FIG. 2B. However, the other component 233 interacts with other parts of the target 140. Part 243 is shown as a circular region on the target 140. However, the interaction between component 233a and target 140 can affect parts of target 140 other than those labeled as 243 in FIG. 2B, where portion 243 is not necessarily a circular region.

FIG. 2C is a graph plotting the intensities of the components 233a to 233e of the modified light beam 232 as a function of the position along the direction X. In the example of FIG. 2C, the intensities of the components 233a to 233e vary. In another embodiment, the modulation element 222 is a diffraction element that produces diffraction orders of equal intensity. For example, in these examples, the modulation element 222 can be a Daman grid.

[0050] The interaction between component 233 and target 140 produces modified target 245 (FIG. 2D). The modified target 245 has a modified region 244 formed by interacting component 233 with target 140. For simplicity, only the interaction between the target material and component 233a within portion 243 is considered and only one modified region 244 is marked. However, the other component 233 interacts in a manner similar to the target material in other parts of the target 140 to form other modified regions. FIG. 2D shows the other modified regions as dashed circular regions.

The interaction between the target material and component 233a within portion 243 alters the physical characteristics of portion 243. For example, the interaction can change the geometric distribution of the portion 243 by removing a portion of the target material from the portion 243, thereby forming a concave region. In this example, the correction region 244 is a concave region. The concave region is the region without the target material. The concave region can be a void. The target material can be removed, for example, by excision, emission, and / or conversion to a plasma that emits no EUV light or emits minimal EUV light. The concave region can be a hole, pocket, or opening within the correction target 245. The concave region can pass through the correction target 245. Further, the concave region can have any shape. For example, the concave region can be a conical or rectangular slit that extends into the correction target 245 but does not penetrate the correction target 245. The characteristics of the concave region (eg, shape, depth, and cross section) depend on the strength and diameter of component 233a and also on the properties of the target material within portion 243. The interaction between component 233a and portion 243 can alter the characteristics of portion 243 in other ways. For example, the interaction can reduce the density of the portion 243. In this example, the modified region 244 is a reduced density region that can contain the target material.

[0052] As discussed above, only one modification region 244 is marked in FIG. 2D, but other modification regions are formed to generate the modification target 245. The various modification areas on the modification target 245 can have different characteristics from each other.

[0053] Regardless of how the interaction alters a particular feature of portion 243 (and other unmarked portions), the interaction between component 233 and target 140 causes EUV light. It forms a modified target 245 that is easily converted by the emitted plasma. For example, forming a concave region results in a modified target 245 having a larger surface area than the target 140. The larger surface area corresponds to the larger amount of target material exposed to the incident light beam, thereby converting more target material into plasma emitting EUV light.

The two-dimensional lattice pattern formed by the component 233 in FIG. 2B is just one possible pattern that can be formed within the target region 242. Other patterns can be generated depending on the configuration and characteristics of the modulation element 222. 2E to 2G show examples of components of other patterns. FIG. 2E contains concentric component 233_E separated by a light-free region. Component 233_E can be formed, for example, in an embodiment where the modulation element 222 is a circular aperture. FIG. 2F shows component 233_F arranged in a one-dimensional array. In the example of FIG. 2F, component 233F has a rectangular cross section. FIG. 2G shows yet another example of the arrangement of component 233_G. Component 233_G is represented as a black circle. FIG. 2G shows the target region 142 in the XY and XY planes. In the example of FIG. 2G, component 233_G generally propagates along the Z and −X directions. Thus, component 233_G reaches the target region 142 from multiple directions and interacts with the target 140 on surfaces in the XY and XY planes.

[0055] FIG. 3 is a block diagram of the EUV light source 300. The EUV light source 300 is an example of an embodiment of the light source 100 of FIG. 1A. The EUV light source 300 includes a first light generation module 305a and a second light generation module 305b. The light generation module 305a emits a first light beam 306a onto the beam path 307a, and the light generation module 305b emits a second light beam 306b onto the beam path 307b. The first light beam 306a is used to form the modified light beam 332a. The modified light beam 332a interacts with the target 340 to form the modified target 345, but generally does not form a plasma that emits EUV light (or forms a plasma that emits only a small amount or a very small amount of EUV light. ). The first light beam 306a can be referred to as a "prepulse" light beam. The second light beam 306b is a light beam having sufficient energy to convert the target material in the modified target 345 into a plasma that emits EUV light 399. The second light beam 306b can be referred to as a "main pulse" light beam or a heated light beam. For certain pairs of prepulse and mainpulse, where the prepulse forms the correction target 345 and the main pulse converts the correction target 345 into a plasma that emits EUV light, so that the prepulse occurs before the main pulse. The first light generation module 305a and / or the second light generation module 305b is controlled.

The light generation module 305b can be, for example, a carbon dioxide (CO ₂ ) laser, and the wavelength of the second light beam 306b can be, for example, 10.59 microns (μm). The first light generation module 305a can be a solid-state laser such as an erbium-doped fiber (Er: glass) laser or a Q-switched Nd: YAG laser. In these examples, the wavelength of the first light beam 306a can be, for example, 1.06 μm. In some embodiments, the first light generator module 305a and the second light generator module 305b are the same type of light source. For example, both the first and second light generation modules 305a and 305b can be CO ₂ lasers. In these examples, the first and second light beams 306a, 306b can have the same spectral components. For example, the first and second light beams 306a, 306b can have 10.59 μm. In a further example, both the first and second light generation modules 305a and 305b can be solid-state lasers. In these examples, both the first and second light beams 306a, 206b can have a wavelength of, for example, 1.06 μm.

[0057] In some embodiments, the same type of light source is used for the first and second light generation modules 305a, 305b, but the spectral components of the first and second light beams 306a, 306b are different. .. For example, the first and second light generation modules 305a, 305b can be implemented as a single module containing two _{CO 2 seed laser subsystems and one amplifier.} One of the seed laser subsystems produces a first light beam 306a at a wavelength of 10.26 μm, for example, and the other seed laser subsystem produces a second light beam 306b at a wavelength of 10.59 μm, for example. Generate. These two wavelengths can originate from different lines of the _{CO 2 laser.}

[0058] Further, wavelengths other than those shown above can be used. For example, either or both of the first light beam 306a and the second light beam 306b can have a wavelength of less than 1 μm. The use of relatively short wavelengths (such as wavelengths less than 1 μm) can be advantageous in some environments. For example, relatively short wavelengths allow for smaller focal sizes and can improve control of beam shaping.

[0059] The first light beam 306a interacts with the modulation element 322 to generate the modified light beam 332a. The modulation element 322 is any optical component or set of components capable of spatially modulating the first light beam 306a. The modified light beam 332a has a different spatial profile than the first light beam 306a. The spatial profile of the modified light beam 332a depends on the configuration of the modulation element 322. The modified light beam 332a can have a spatial profile that varies continuously as a function of position (eg, as shown in FIG. 1C), or the modified light beam 332a (eg, FIG. 2B and FIG. It can contain components of light that are separated by light-free regions (as shown in FIG. 2G from 2E). In an embodiment in which the spatial profile continuously fluctuates as a function of position, the components are not discrete and can be considered as any part of the spatial profile.

[0060] The EUV light source 300 also includes a beam combiner 324 positioned to guide the modified light beam 332a and the second light beam 306b towards the beam transmission system 325. The beam combiner 324 is an arbitrary optical element or a set of optical elements capable of interacting with the modified light beam 332a and the second light beam 306b. For example, the beam combiner 324 can include one or more mirrors and / or one or more beam splitters, some of which direct the modified light beam 332a towards the beam transmission system 325. Positioned, the others are positioned to guide the second beam 306b towards the beam transmission system 325. In the embodiment in which the modified light beam 332a and the second light beam 306b have different spectral components, the beam combiner 324 transmits the wavelength in the second light beam 306b and reflects the wavelength in the modified light beam 332a. It can be a dichroic element (such as a dichroic beam splitter) configured in. In the example of FIG. 3, the beam combiner 324 guides the modified light beam 332a and the second light beam 306b toward the beam transmission system 325 on the spatially separated beam path.

[0061] The beam transmission system 325 also includes a focus system 326. The focus system 326 includes any combination of optics arranged to focus the modified light beam 332a and the second light beam 306b. For example, the focus system 326 can include a lens and / or a mirror. The modified light beam 332a is focused on or near the initial target region 342a, and the second light beam 306b is focused on or near the modified target region 342b. In the example shown in FIG. 3, the focus system 326 focuses the modified light beam 332a and the second light beam 306b even if they do not follow the same beam path through the focus system 326. .. However, in some embodiments, the optical element that focuses the modified light beam 332a is separated from the optical element that focuses the second light beam 306b. For example, when the spectral component of the modified light beam 306a is different from the spectral component of the second light beam 306b, a separate optical component can be used.

[0062] The initial target region 342a receives the target 340 from the target material supply system 350. In the example of FIG. 3, the target 340 is a spherical droplet of molten metal. The components in the modified light beam 332a interact with the target 340 to form the modified target 345. The interaction between the modified light beam 332a and the target 340 alters one or more properties of the target 340. For example, the modified target 345 can have a concave region and / or a reduced density region as discussed with respect to the modified target 245 in FIG. 2D. The modified target 345 travels to the modified target region 342b and interacts with the second light beam 306b. The interaction with the second light beam 306b converts at least a portion of the target material in the modified target 345 into a plasma that emits EUV light 399.

[0063] FIG. 4 is a block diagram of the EUV light source 400. The EUV light source 400 is another example of the example of the EUV light source 100. The EUV light source 400 is similar to the EUV light source 300, except that the EUV light source 400 uses two "prepulse" light beams to generate the modified target 445.

[0064] The EUV light source 400 includes light generation modules 405a, 405b, and 405c. The light generation module 405a emits a first light beam 406a. The light generation module 405b emits a second light beam 406b. The light generation module 405c emits a third light beam 406c. The light generation module 405c can be, for example, a CO ₂ laser. The light beams 405a, 405b, 405c can all have the same spectral component, or at least one of the light beams 405a, 405b, 405c can be different from the other light beams. The light beams 405a and 405b can be two different emission lines _{of the CO 2 laser.} The emission line of the CO ₂ laser includes light at, for example, 9.4 μm, 10.26 μm, and 10.59 μm. In some embodiments, either the light beam 405a or the light beam 405b is a beam formed by the emission lines _{of a CO 2 laser at 10.26 μm.} In these examples, the other of the light beams 405a and 405b is a beam having a wavelength of 1.06 μm produced by a solid-state laser (eg, such as a Q-switched Nd: YAG laser). In another embodiment, both the light beam 405a and the light beam 405b are generated by a solid-state laser.

[0065] The first and second light beams 406a, 406b change one or more physical characteristics of the target 440 in order to generate the modified target 445. In the embodiment shown in FIG. 4, the first light beam 406a interacts with the target 440 to spatially expand the target 440 and form an intermediate target 447. The intermediate target 447 can be a molten metal disc shape division having a larger range than the target 440 along the X axis (including the X direction and the −X direction opposite to the X direction). In addition, the intermediate target 447 has a smaller range than the target 440 along the Z axis. The intermediate target 447 moves in the X direction.

The EUV light source 400 also includes a modulation element 422 positioned to interact with the second light beam 406b. The modulation element 422 is an arbitrary optical element or a set of elements capable of spatially modulating the second light beam 406b. For example, the modulation element 422 can be similar to the modulation element 122 discussed with respect to FIG. 1A or the modulation element 222 discussed with respect to FIG. 2A. The interaction between the modulation element 422 and the second light beam 406b produces a modified light beam 432b. The modified light beam 432b has a different spatial profile than the second light beam 406b. The modified light beam 432b and the first light beam 406a are guided toward the focus system 425a by the beam combiner 424. The beam combiner 424 can be any optical element or set of optical elements capable of guiding the modified light beam 432b and the first light beam 406a toward the focus system 425a. The focus system 425a focuses the first light beam 406a at or near the target region 442a that receives the target 440 from the target supply system 450, and also receives the intermediate target 447 from the target region 442a at or near the target region 442b. Then, the correction light beam 432b is focused.

The intermediate target 447 and the modified light beam 432b interact in the target region 442b to form the modified target 445. In the illustrated example, the interaction between the modified light beam 432b and the intermediate target 447 forms a concave region 444 on the modified target 445. After interacting with the modified light beam 432b, the modified target 445 moves into the target region 442c that receives the third light beam 406c. The third light beam 406c is focused by the focus system 426c and has sufficient energy to convert at least a portion of the target material in the modified target 445 into a plasma that emits EUV light. The concave region 444 can convert more target material in the modified target 445 into plasma. Therefore, the interaction between the modified target 445 and the third light beam 406c produces more EUV light and less debris when compared to a target without concave region 444 (such as target 440 or intermediate target 447). can do.

FIG. 5 is a block diagram of the EUV light source 500. The EUV light source 500 is another example of the embodiment of the EUV light source 100 of FIG. 1A. In the EUV light source 500, a single light beam is used to generate the modified target 545 and to form a plasma emitting EUV light from the modified target 545.

[0069] The EUV light source 500 includes a light generation module 505. The light generation module 505 can be, for example, a CO ₂ laser. The light generation module 505 emits a light beam 506 onto the beam path 507 towards the modulation device 520. The modulation device 520 includes a modulation element 522. Modulation element 522 is any optical element capable of spatially modulating the light beam 506 to components that do not all have the same intensity. The modulation element 522 can be similar to the modulation element 222 (FIG. 2A). The interaction between the modulation element 522 and the light beam 506 modulates the light beam 506 to produce components 533a-533g. The components 533a-533g are separated from each other by a light-free region.

[0070] Components 533a to 533g propagate away from the modulation element 522 in different directions. Components 533e-533g propagate toward the beam dump 528 and do not exit the modulation device 520. The components 533a to 533c propagate toward the target region 542a that receives the target 540. The target 540 can be a spherical droplet provided by a target material supply system such as the system 450 of FIG. 4, or the target 540 is generated by prior interaction with another light beam ( It can be an intermediate target (such as the intermediate target 447 in FIG. 4). Components 533a-533c have sufficient intensity to modify the properties of the target 540 without producing a plasma that emits EUV light. Therefore, regardless of the shape of target 540, the interaction between components 533a-533c produces modified target 545. In the example of FIG. 5, three concave regions 544 are shown. Each concave region 544 is formed from the interaction between one of the components 533a-533c and the target 540.

Component 533d propagates towards the focus system 525. The focus system 525 focuses component 533d at or near the modified target region 542b that receives the modified target 545. The focus system 525 also includes a light delay 529 that causes the component 533d to reach the modified target region 542b at a time after the components 533a-533c and when the modified target 545 is within the modified target region 542b. The optical delay 529 can be, for example, an arrangement that includes a plurality of reflective elements (such as mirrors) that fold the component 533d into many paths within a relatively compact volume. Such an optical delay 529 can advance component 533d an additional hundreds of meters so that a delay of hundreds of nanoseconds can be achieved.

[0072] Component 533d has greater intensity than components 533a-533c, and component 533d is sufficient to convert at least a portion of the target material within the modified target 545 into a plasma that emits EUV light. Have energy. For example, the total energy of the component can be about 2 kW (kW), while the energy within component 533d can be greater than 100 kW.

FIG. 6 is a block diagram of the EUV light source 600. The EUV light source 600 is another example of the example of the EUV light source 100. The EUV light source 600 is an EUV light source 300 (FIG. 6), except that the EUV light source 600 includes a modulation device 620 that spatially modulates a portion of the second light beam 306b instead of modulating the first light beam 306a. It is the same as 3). In the embodiment shown in FIG. 6, the target region 642 receives the target 640 from the target material supply 350. FIG. 7 shows the target region 642 over time. FIG. 8 shows the intensity of light within the target region 642 over the time scale of FIG.

[0074] The beam combiner 324 guides the first light beam 306a toward the target 640. The interaction between the first light beam 306a and the target 640 forms an intermediate target 647. The second light beam 306b passes through the beam combiner 324 and interacts with the modulation device 620 to form a single light pulse 604. The modulation device 620 includes a time modulation device 662 and a spatial modulation element 622. The spatial modulation element 622 is a dynamic modulation element that can be controlled by the controller 660. The time modulation device 662 can also be controlled by the controller 660. Controller 660 can include an electronic processor and electronic memory or storage. The electronic processor can store instructions that command the processor to perform an action, perhaps as a computer program. For example, when the electronic processor is provided by the controller 660 to the modulation device 620, the modulation element 622, and / or the time modulation device 662, the electronic processor performs a specific action on the modulation device 620, the modulation element 622, and / or the time modulation device 662. It can generate a signal to execute.

[0075] The time modulation device 662 is an arbitrary optical element capable of controlling the time profile (intensity as a function of time) of the second light beam 306b. For example, the time modulation device 662 can be an electro-optical modulator (EOM). The time modulation device 662 is controlled to form a light pulse 604, which includes a pedestal 608 and a heating portion 609 from a second light beam 605b. The pedestal 608 and the heated portion 609 are shown in FIG. The pedestal 608 is temporally connected to the heating portion 609 so that the pedestal 608 and the heating portion 609 are part of a single light pulse 604 (FIGS. 6 and 8).

The time profile of the pedestal 608 can have any shape. For example, the intensity of the pedestal 608 can be increased and decreased over time so that the pedestal 608 has a somewhat similar shape to the pulse. The example of FIG. 8 shows an example of such a pedestal. In another example, the intensity of the pedestal 608 can increase and decrease over time without having a pulse-like profile. In yet another example, the pedestal 608 can have a monotonically increasing intensity until the heating portion 609 begins. Regardless of the shape of the pedestal 608, the pedestal 608 and the heating portion 609 both form a single pulse 604. That is, there is no light-free region between the beginning of pulse 604 and the end of pulse 604.

[0077] The spatial modulation element 622 is controlled so that only the pedestal 608 is spatially modulated. Therefore, the spatial profile of the pedestal 608 is modified. In some embodiments, the pedestal focal size in the xy plane is modulated to achieve different intensities. For example, the focal size can be modulated to heat the outer edge of the target before heating the material placed closer to the center of the target.

As shown in FIGS. 7 and 8, the pedestal 608 reaches the target region 642 before the heated portion 609. The spatially modulated pedestal 608 interacts with the intermediate target 647 to form the modified target 645. The heated portion 609 reaches the target region 642 after the pedestal 608. The heated portion 609 has much greater intensity than the pedestal 608 and is capable of converting the target material in the modified target 645 into a plasma that emits EUV light 399. The EUV light source 600 uses two separate pulses, a first light beam 306a and a second light beam 306b. However, the second light beam 306b is such that the second light beam 306b generates a pulse 608, which modifies the intermediate target 647 and converts the modified target 645 into a plasma that emits EUV light 399. It is affected by the modulation device 620.

[0079] FIGS. 9 and 10 consider an example of the EUV photolithography system 900. EUV light generated by any of the EUV light sources 100, 200, 300, 400, 500, and 600 can be used with the photolithography system 900. Further, a system including any of EUV light sources 100, 200, 300, 400, 500, and 600 can also include a photolithography system such as the photolithography system 900. FIG. 11 considers an example of an EUV light source. EUV light sources 100, 200, 300, 400, 500, and 600 can include additional components and systems as discussed with respect to FIGS. 10 and 11. For example, EUV light sources 100, 200, 300, 400, 500, and 600 include vacuum chambers such as the vacuum chamber 1130 discussed with respect to FIG.

[0080] FIG. 9 schematically shows a lithography apparatus 900 including a source collector module SO according to an embodiment. Lithography apparatus 900 includes:
An illumination system (illuminator) IL configured to regulate radiation beam B (eg EUV radiation), and
A support structure (eg, mask table) MT constructed to support a patterning device (eg, mask or reticle) MA and connected to a first positioner PM configured to accurately position the patterning device according to specific parameters. When,
A substrate table (eg wafer table) WT configured to hold a substrate (eg, resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate according to specific parameters.
It includes a projection system (for example, a refraction projection lens system) PS configured to project a pattern applied to the radiation beam B by the patterning device MA onto a target portion C (for example, including one or more dies) of the substrate W. ..

Lighting systems are refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components for inducing, shaping, or controlling radiation, or any of them. It can include various types of optical components such as combinations.

The support structure MT holds the patterning device MA in a manner depending on conditions such as the orientation of the patterning device, the design of the lithography apparatus, for example, whether or not the patterning device is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be, for example, a frame or table, and may be fixed or movable as required. The support structure can ensure that the patterning device is in the desired position with respect to, for example, a projection system.

[0083] As used herein, the term "patterning device" is intended to refer to any device that can be used to pattern the cross section of a radiated beam, such as to generate a pattern on a target portion of a substrate. It should be interpreted in a broad sense. The pattern imparted to the radiated beam may correspond to a particular functional layer of the device generated in a target portion such as an integrated circuit.

The patterning device may be transparent or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, including mask types such as binary masks, alternating phase shift masks, attenuated phase shift masks, and various hybrid mask types. Is done. As an example of a programmable mirror array, a matrix array of small mirrors is used, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirror imparts a pattern to the radiated beam reflected by the mirror matrix.

[0085] A projection system PS, such as the illumination system IL, is refracted, reflected, magnetic, electromagnetic, electrostatic, or other type of optics, if suitable for the exposure radiation used or for other factors such as the use of vacuum. It can include various types of optical components, such as components, or any combination thereof. It may be desirable to use a vacuum for EUV radiation, as other gases can absorb so much radiation.

[0086] As shown herein, the device is of the reflective type (eg, using a reflective mask). The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and / or two or more patterning device tables). In such a "multi-stage" machine, the preliminary steps may be performed on one or more tables while additional tables are used in parallel or one or more other tables are used for exposure. Can be done.

[0087] With reference to FIG. 9, the illuminator IL receives an extreme ultraviolet radiation beam from the source collector module SO. The method for producing EUV light is not necessarily limited, but converting a material having at least one element with one or more emission lines within the EUV range, such as xenon, lithium, or tin, into a plasma state. include. In one of these methods, the essential plasma, often referred to as the laser-generated plasma (“LPP”), is obtained by irradiating a fuel, such as a droplet, stream, or cluster of a material with essential ray emitting elements, with a laser beam. It can be generated. The source collector module SO, not shown in FIG. 9, can be part of an EUV emission system that includes a laser to provide a laser beam that excites fuel. The resulting plasma emits radiation, such as EUV radiation, which is collected using a radiation collector and processed within the source collector module. For example, when a carbon dioxide (CO ₂ ) laser is used to provide a laser beam for fuel excitation, the laser and source collector modules can be separate entities.

[0088] In these cases, the laser is not considered to form part of a lithographic device, and the emitted beam is sourced from the laser using, for example, a beam delivery system that includes a suitable induction mirror and / or beam expander. It is passed to the collector module. In other cases, for example, when the source is a discharge-generating plasma EUV generator, often referred to as a DPP source, the source can be an integral part of the source collector module.

[0089] The illuminator IL may include an adjuster for adjusting the angular intensity distribution of the radiated beam. In general, the outer and / or inner radial range of the intensity distribution on the pupil plane of the illuminator (commonly referred to as σ-outer and σ-inner, respectively) can be adjusted. In addition, the illuminator IL can include various other components such as faceted field and pupil mirror devices. The illuminator IL may be used to adjust the radiated beam to obtain the desired uniformity and intensity distribution over its cross section.

[0090] The radiated beam B is incident on the patterning device (eg, mask) MA held on the support structure (eg, mask table) MT and is patterned by the patterning device. After being reflected from the patterning device (eg, mask) MA, the radiating beam B passes through the projection system PS, which focuses the beam on the target portion C of the substrate W. Using a second positioner PW and position sensor PS2 (eg, an interferometer device, linear encoder or capacitance sensor), the substrate table WT may, for example, place a different target portion C in the path of the radiation beam B. Can be moved accurately to. Similarly, the first positioner PM and another position sensor PS1 can be used to accurately position the patterning device (eg, mask) MA with respect to the path of the radiated beam B. The patterning device (for example, mask) MA and the substrate W can be aligned using the patterning device alignment marks M1 and M2 and the substrate alignment marks P1 and P2.

The illustrated lithography apparatus can be used in at least one of the following modes.
1. 1. In step mode, the support structure (eg, mask table) MT and substrate table WT are basically kept stationary, while the entire pattern applied to the radiated beam is projected onto the target portion C in one go (ie,). Single static exposure). The substrate table WT is then moved in the X and / or Y directions so that another target portion C can be exposed.
2. In scan mode, the support structure (eg, mask table) MT and substrate table WT are scanned synchronously (ie, single dynamic exposure) while the pattern given to the radiated beam is projected onto the target portion C. The velocity and orientation of the substrate table WT relative to the support structure (eg, mask table) MT can be determined by the (reduced) magnification and image inversion characteristics of the projection system PS.
3. 3. In another mode, the support structure (eg, mask table) MT holds a programmable patterning device and is essentially kept stationary, moving or scanning the substrate table WT while targeting the pattern given to the radiated beam. Project to C. In this mode, pulse sources are commonly used to update the programmable patterning device as needed each time the substrate table WT is moved or between successive emission pulses during a scan. This mode of operation is readily available for maskless lithography using programmable patterning devices such as the types of programmable mirror arrays mentioned above.

[0092] Combinations and / or modifications of the mode of use described above, or completely different modes of use are also available.

FIG. 10 shows in more detail an embodiment of a lithography apparatus 900 including a source collector module SO, a lighting system IL, and a projection system PS. The source collector module SO is configured and arranged so that the vacuum environment can be maintained within the closed structure 1020 of the source collector module SO. Systems IL and PS are likewise contained within their own vacuum environment. The EUV emission plasma 2 can be formed by a laser-generated LPP plasma source. The function of the source collector module SO is to transport the EUV radiation beam 20 from the plasma 2 so that it is focused within the virtual light source point. Virtual light source points are commonly referred to as intermediate focal points (IFs), and source collector modules are arranged such that the intermediate focal points (IFs) are located at or near aperture 1021 within the closed structure 1020. The virtual light source point IF is an image of the radiated emission plasma 2.

[0094] From aperture 1021 at the midfocal IF, radiation traverses the illumination system IL, which in this example includes a faceted field mirror device 22 and a faceted pupil mirror device 24. These devices were arranged in the patterning device MA to provide the desired angular distribution of the radiant beam 21 and in the patterning device MA to provide the desired uniformity of radiant intensity (indicated by reference number 1060). Form a so-called "fly-eye" illuminator. When the beam 21 is reflected in the patterning device MA held by the support structure (mask table) MT, the patterned beam 26 is formed and the patterned beam 26 is passed through the reflective elements 28, 30 by the substrate table WT. The image is formed on the substrate W held by the projection system PS. While the substrate table WT and the patterning device table MT perform synchronous movements to scan the pattern on the patterning device MA through the slits of illumination to expose the target portion C on the substrate W. A pulse of radiation is generated.

[0095] Each system IL and PS is placed in a unique vacuum or near vacuum environment defined by a closed structure similar to the closed structure 1020. In general, more elements can be present within the lighting system IL and the projection system PS, as shown in the figure. In addition, there can be more mirrors shown in the figure. For example, in the lighting system IL and / or the projection system PS, there can be 1 to 6 additional reflective elements in addition to those shown in FIG.

[0096] Considering the source collector module SO in more detail, the laser energy source including the laser 1023 is arranged to store the laser energy 1024 in the fuel containing the target material. The target material can be any material that emits EUV radiation in the plasma state, such as xenon (Xe), tin (Sn), or lithium (Li). Plasma 2 is a plasma that is highly ionized using an electron temperature of several tens of electron volts (eV). Higher energy EUV radiation can be generated using other fuel materials such as terbium (Tb) and gadolinium (Gd). The energy radiation generated during the deexcitation and recombination of these ions is emitted from the plasma, focused by the near normal incident collector 3 and focused on the aperture 1021. Plasma 2 and aperture 1021 are located at the first and second focal points of collector CO, respectively.

[0097] The collector 3 shown in FIG. 10 is a single curved mirror, but the collector can take other forms. For example, the collector can be a Schwarzschild collector with two radiation collection surfaces. In one embodiment, the collector can be a glazed incident collector with a plurality of substantially cylindrical reflectors nested together.

[0098] A droplet generator 1026 is arranged within the enclosure 1020 to ignite a high frequency stream 1028 of droplets towards a desired location of plasma 2, for example to carry fuel, which is liquid tin. .. During operation, the laser energy 1024 is conveyed in synchronization with the operation of the droplet generator 1026 in order to convey the impulse of radiation so that each fuel droplet is directed into the plasma 2. The transport frequency of the droplet can be several kilohertz, for example 50 kHz. In practice, the laser energy 1024 is delivered within at least two pulses, and the energy-limited prepulse is delivered to the droplets before reaching the plasma location to vaporize the fuel material into a small cloud, and then the laser. The main pulse of energy 1024 is transported to the cloud at the desired location to generate the plasma 2. A trap 1030 is provided on the opposite side of the closed structure 1020 to capture fuel that is not directed to the plasma for any reason.

[0099] The droplet generator 1026 comprises a reservoir 1001 containing a fuel liquid (eg, molten tin) as well as a filter 1069 and a nozzle 1002. Nozzle 1002 is configured to eject a droplet of fuel liquid towards the plasma 2 formation location. The fuel liquid droplets can be ejected from the nozzle 1002 by a combination of the pressure in the reservoir 1001 and the vibration applied to the nozzle by a piezo actuator (not shown).

As will be appreciated by those skilled in the art, reference axes X, Y, and Z can be defined to measure and describe the geometry and behavior of the device, its various components, and the emitted beams 20, 21, 26. Is. Local reference frames for the X, Y, and Z axes can be defined in each part of the device. In the example of FIG. 10, in a broad sense, the Z axis coincides with the direction of the optical axis O at a given point in the system, and is generally perpendicular to the plane of the patterning device (reticle) MA and perpendicular to the plane of the substrate W. Is. In the source collector module, the X-axis is broadly aligned with the direction of the fuel stream 1028 and the Y-axis is perpendicular to it, indicating away from the page as shown in FIG. On the other hand, in the vicinity of the support structure MT holding the reticle MA, the X-axis generally intersects the scanning direction aligned with the Y-axis. For convenience, in this area of the schematic of FIG. 10, the X-axis directs the page to leave, as shown again. These designations are customary in the art and are adopted herein for convenience. In principle, any reference frame can be selected to illustrate the device and its behavior.

[0101] In general, within a typical device, there are a number of additional components used in the operation of the source collector module and the lithography device 900, which are not shown here. These include, for example, arrangements to reduce or mitigate the effects of contamination in a closed vacuum to prevent the deposition of fuel material that impairs or impairs the performance of the collector 3 and other optical systems. Other mechanisms that exist but are not described in detail are all sensors, controllers, and actuators that are involved in controlling the various components and subsystems of lithography equipment 900.

[0102] With reference to FIG. 11, an example of the LPP EUV optical source 1100 is shown. The optical source 1100 can be used as a source collector module SO in the lithography apparatus 900. Further, the light generation module 105 of FIGS. 1A and 2A, the light generation module 505 of FIG. 5, the light generation module 305b of FIG. 3, or the light generation module 405b of FIG. 4 can be a part of the drive laser 1115. .. The drive laser 1115 can be used as the laser 1023 (FIG. 10).

[0103] The LPP EUV optical source 1100 is formed by irradiating the target mixing 1114 at the plasma forming location 1105 with an amplified optical beam 1110 traveling along the beam path towards the target mixing 1114. The plasma forming location 1105 is located inside 1107 of the vacuum chamber 1130. When the amplified optical beam 1110 hits the target mixing 1114, the target material in the target mixing 1114 is transformed into a plasma state with elements with emission lines in the EUV range. The plasma produced has certain characteristics that depend on the composition of the target material in the target mixture 1114. These features can include the wavelength of EUV light produced by the plasma and the type and amount of debris released from the plasma.

[0104] Optical source 1100 transports and controls a target mixture 1114 in the form of droplets, liquid streams, solid particles or clusters, solid particles contained within the droplets, or solid particles contained within the liquid stream. Also includes a supply system 1125 that guides and guides. Target mixing 1114 includes target materials, such as water, tin, lithium, xenon, or any material that has a emission line within the EUV range when converted to a plasma state. For example, the element tin can be a tin compound such as pure tin (Sn), such as SnBr ₄ , SnBr ₂ , SnH ₄ , tin alloys such as tin gallium alloys, tin indium alloys, tin indium gallium alloys, or any of these alloys. It can be used as a combination. Target mixing 1114 may also contain impurities such as non-target particles. Therefore, in the absence of impurities, the target mixture 1114 is composed only of the target material. The target mixing 1114 is transported by the supply system 1125 to the interior 1107 of chamber 1130 and the plasma forming location 1105.

[0105] The optical source 1100 includes a drive laser system 1115 that produces an amplified optical beam 1110 due to the population inversion of the laser system 1115 in the gain medium. The optical source 1100 includes a beam delivery system between the laser system 1115 and the plasma forming location 1105, and the beam delivery system includes a beam transmission system 1120 and a focus assembly 1122. The beam transmission system 1120 receives the amplified optical beam 1110 from the laser system 1115, steers and modifies the amplified optical beam 1110 as needed, and outputs the amplified optical beam 1110 to the focus assembly 1122. Focus assembly 1122 receives the amplified optical beam 1110 and focuses the beam 1110 on the plasma forming location 1105.

[0106] In some embodiments, the laser system 1115 is one or more optical amplifiers, lasers, and / or for providing one or more main pulses and, in some cases, one or more prepulses. Can include lamps. Each optical amplifier includes a gain medium, an excitation source, and an internal optical system capable of optically amplifying a desired wavelength with high gain. Optical amplifiers may or may not have a laser mirror or other feedback device that forms a laser cavity. Therefore, the laser system 1115 produces the amplified optical beam 1110 due to the population inversion in the gain medium of the laser amplifier, even in the absence of the laser cavity. Further, the laser system 1115 can generate an amplified optical beam 1110 which is a coherent laser beam in order to provide sufficient feedback to the laser system 1115 in the presence of the laser cavity. The term "amplified optical beam" refers to one or more of light from a laser system 1115 that is simply amplified but not necessarily coherent laser oscillation, and light from a laser system 1115 that is amplified but also coherent laser oscillation. Including.

[0107] The optical amplifier in the laser system 1115 _{can include a filling gas containing CO 2} as a gain medium and is greater than or equal to 800 times greater than or equal to between about 9100 nm and about 11000 nm, and especially at wavelengths of about 10600 nm. The gain can amplify the light. Amplifiers and lasers suitable for use within the laser system 1115 generate radiation at about 9300 nm or about 10600 nm, for example using DC or RF excitation, and at relatively high powers, such as 10 kW or more, and. For example, a pulsed laser device operating at a high pulse repetition rate of 40 kHz or higher, such as a pulsed gas discharge CO ₂ laser device, can be included. The number of pulse repetitions can be, for example, 50 kHz. The optical amplifier in the laser system 1115 may also include a cooling system such as water that can be used when operating the laser system 1115 at higher powers.

[0108] Optical source 1100 includes a collector mirror 1135 having an aperture 1140 to allow the amplified optical beam 1110 to pass through and reach the plasma forming location 1105. The collector mirror 1135 can be, for example, an elliptical mirror having a primary focus at the plasma forming location 1105 and a secondary focus at the intermediate location 1145 (also called the intermediate focus), and EUV light can be output from the optical source 1100. For example, it can be input to an integrated circuit lithography tool (not shown). The optical source 1100 forms plasma from the collector mirror 1135 in order to reduce the amount of plasma generating debris entering the focus assembly 1122 and / or the beam transmission system 1120 while the amplified optical beam 1110 can reach the plasma forming location 1105. It can also include an open-ended hollow cone shroud 1150 (eg, a gas cone) that tapers towards location 1105. For this, a gas stream guided towards the plasma forming location 1105 can be provided in the shroud.

The optical source 1100 may also include a main controller 1155 connected to a droplet position detection feedback system 1156, a laser control system 1157, and a beam control system 1158. The optical source 1100 may include one or more targets or droplet imagers 1160 that provide, for example, an output indicating the position of the droplet relative to the plasma forming location 1105 and provide this output to the droplet position detection feedback system 1156. The droplet position detection feedback system 1156 can calculate, for example, the position and orbit of the droplet, which allows it to calculate the droplet position error either by droplet or by average. be. In this way, the droplet position detection feedback system 1156 provides a droplet position error as an input to the main controller 1155. Thus, the main controller 1155 can be used, for example, in a laser control system 1157 that can be used to control a laser timing circuit, and / or a beam transmission system to change the location and / or focusing power of the beam optics within the chamber 1130. It is possible to provide the laser position, direction, and timing correction signals to the beam control system 1158 for controlling the amplified optical beam position and shape of the 1120.

[0110] When the supply system 1125 is released by the target material supply device 1127 in response to a signal from the main controller 1155 to correct an error in the droplet that reaches the desired plasma formation location 1105. Includes a target material delivery control system 1126 that can operate to correct the release point of the droplet.

[0111] In addition, the optical source 1100 is of pulse energy, energy distribution as a function of wavelength, energy within a specific band of wavelength, energy outside a specific band of wavelength, and EUV intensity and / or average output. Optical source detectors 1165 and 1170 can be included to measure one or more EUV light parameters, including but not limited to an angular distribution. The optical source detector 1165 generates a feedback signal for use by the main controller 1155. The feedback signal can indicate errors in parameters such as the timing and focus of the laser pulse to properly block the droplets at the correct location and time for effective and efficient EUV light generation.

[0112] The optical source 1100 includes a guide laser 1175 that can be used to align various sections of the optical source 1100 or to assist in steering the amplified optical beam 1110 to the plasma forming location 1105. You can also. In connection with the guide laser 1175, the optical source 1100 includes a metrology system 1124 located within the focus assembly 1122 to sample a portion of the light from the guide laser 1175 and the amplified optical beam 1110. In another embodiment, the metrology system 1124 is located within the beam transmission system 1120. The metrology system 1124 can include optics that sample or redirect a subset of light, such optics being constructed of any material that can withstand the output of the guide laser beam and the amplified optical beam 1110. .. The main controller 1155 analyzes the light sampled from the guide laser 1175 and uses this information to tune the components in the focus assembly 1122 via the beam control system 1158 from the metrology system 1124 and the main controller 1155. , A beam analysis system is formed.

[0113] Thus, in summary, the optical source 1100 has a beam path to irradiate the target mixture 1114 at the plasma forming location 1105 in order to convert the target material in the mixture 1114 into a plasma emitting light within the EUV range. Generates an amplified optical beam 1110 guided along. The amplified optical beam 1110 operates at a specific wavelength (also referred to as a drive laser wavelength), which is determined based on the design and characteristics of the laser system 1115. In addition, the amplified optical beam 1110 is suitable for optics when the target material provides sufficient feedback within the laser system 1115 to generate coherent laser light or for the drive laser system 1115 to form a laser cavity. It can be a laser beam if it includes feedback.

[0114] Other examples are within the scope of the claims. The modulation elements discussed above can be implemented to generate any type of pattern on the target. For example, the modulation element 222 can generate components in a pattern different from that shown in the example of FIG. 2A. In some embodiments, the modulation element 222 is implemented such that all components are on one side of the zero order. Further, the modulation element 522 can be implemented in such a manner that all components other than the component 533d propagate toward the target region 542a and do not require a beam dump 528.

[0115] Other aspects of the invention are set forth in the numbered clauses below.
1. 1. It ’s a system,
A spatial modulation device configured to interact with a light beam to create a modified light beam, the modified light beam having non-uniform intensity along the direction perpendicular to the direction of propagation of the modified light beam. Spatial modulation devices and spatial modulation devices that include a spatial pattern of light, the spatial pattern of light containing one or more components of light.
A target supply system configured to provide a target to a target region, the target containing a target material that emits EUV light when in a plasma state, the target region being one or more lights in a modified beam. With a target supply system, which overlaps the beam path so that at least some of the components of the
The system.
2. The system according to Clause 1, wherein the spatial modulation device comprises a diffractive optical element.
3. 3. The system according to Clause 2, wherein the diffractive optical system comprises a spatial light modulator (SLM), adaptive optics, reticle, and / or lattice.
4. The system according to Clause 1, wherein the spatial modulation device comprises a refracting optical element.
5. The system according to clause 4, wherein the spatial modulation device comprises a lens, a small lens array, and / or a reticle.
6. The system according to Clause 1, wherein the spatial pattern of light comprises two or more light components, each of which has substantially the same intensity.
7. The system according to Clause 1, wherein the spatial pattern of light comprises two or more light components arranged in a linear grid.
8. The system according to Clause 2, wherein the spatial modulation device comprises at least one Daman grid.
9. A first light generation module configured to emit a light beam, and
A second light generation module, configured to emit a second light beam,
The system described in Clause 1, further comprising.
10. The spatial modulation device is further configured to interact with the second light beam to create a second modified light beam, the second modified light beam being perpendicular to the direction of propagation of the second modified light beam. The system according to clause 1, wherein the spatial pattern of the second light comprises a second light spatial pattern having non-uniform intensity along the same direction, the spatial pattern of the second light comprising one or more components of the second light.
11. A method of forming a target for extreme ultraviolet (EUV) light sources,
Guiding the light beam on the beam path and
By interacting a light beam with a spatial modulation device positioned on the beam path to form a modified light beam, the modified light beam is non-uniform along the direction perpendicular to the direction of propagation of the modified light beam. Interacting light beams with one or more light components, including a spatial pattern of light with high intensity.
The interaction of a modified light beam with a target containing a target material that emits EUV light when in a plasma state, at least some of the light components of one or more of the spatial patterns are in the area of the target. Interacting with the modified light beam, which modifies the characteristics of that region of the target,
A method of forming a target for extreme ultraviolet (EUV) light sources, including.
12. The method of clause 11, wherein the property comprises density, and modifying the property comprises reducing the density.
13. The method of clause 11, wherein the spatial pattern of light comprises two or more components of light.
14. The method of clause 13, wherein all light components have the same intensity.
15. 13. The method of clause 13, wherein the components of light are arranged in a grid and regions of the target that interact directly with the components of light are arranged in a grid.
16. 12. The method of clause 11, further comprising interacting the modified beam with the focus assembly before the modified light beam interacts with the target.
17. The components of the light are spatially separated and spatially discrete so that some of the targets between any two components of the light do not interact with any of the components in the modified light beam, according to Clause 13. The method described.
18. By interacting the initial target with the second light beam to form the modified target, the modified target has a larger range in the first direction than the initial target and in the second direction. Interacting the initial target with the second light beam, which has a smaller range than the initial target and the first and second directions are orthogonal to each other.
Interacting a modified light beam with a target comprising a target material that emits EUV light when in a plasma state involves interacting with the modified light beam with a modified target of one or more components of light. Each interacts with a region of the modified target to modify the properties of that region of the modified target, interacting with the modified light beam and interacting with the target.
The method according to clause 11, further comprising.
19. Further comprising interacting the modified light beam with the modified target and then interacting with the modified target with a third light beam, the third light beam provides at least a portion of the target material within the modified target with EUV. 18. The method of clause 18, which has sufficient energy to convert it into a plasma that emits light.
20. Further comprising interacting the target with another light beam after interacting with the modified light beam, the other light beams provide at least a portion of the target material in the second modified target with EUV light. 11. The method of clause 11, which has sufficient energy to convert the plasma to emit.
21. Properties include conversion efficiencies with respect to the amount of EUV light emitted and the energy of other light beams, and modifying the properties of some of the targets involves increasing the conversion efficiencies associated with the entire target. The method described in Clause 20.
22. The method of clause 20, wherein the light beam and other light beams are temporally connected and are part of a single pulse of light.
23. The method of clause 11, wherein the properties include the surface area of the target, and modifying the properties of any part of the target comprises increasing the surface area of the entire target.
24. The method of clause 23, wherein the amount of increase in surface area is related to the number of light components in the modified light beam.
25. Interacting a modified light beam with a target comprising a target material that emits EUV light when in a plasma state comprises interacting the modified light beam with a target having a substantially spherical shape. The method described in.

[0116] Other examples are within the scope of the following claims.

Claims (25)

It ’s a system,
A spatial modulation device configured to interact with a light beam to create a modified light beam, the modified light beam having non-uniform intensity along a direction perpendicular to the direction of propagation of the modified light beam. A spatial modulation device and a spatial modulation device comprising one or more light components.
A target supply system configured to provide a target to a target region, wherein the target comprises a target material that emits EUV light when in a plasma state, the target region being the 1 in the modified beam. A target supply system that overlaps the beam path so that at least some of the components of one or more lights interact with some of the targets.
The system. The system according to claim 1, wherein the spatial modulation device includes a diffractive optical element. The system of claim 2, wherein the diffractive optical system comprises a spatial light modulator (SLM), adaptive optics, reticle, and / or lattice. The system according to claim 1, wherein the spatial modulation device includes a refraction optical element. The system of claim 4, wherein the spatial modulation device comprises a lens, a small lens array, and / or a reticle. The system of claim 1, wherein the spatial pattern of light comprises two or more light components, each of which has substantially the same intensity. The system of claim 1, wherein the spatial pattern of light comprises two or more light components arranged in a linear grid. The system of claim 2, wherein the spatial modulation device comprises at least one Daman grid. A first light generation module configured to emit the light beam, and
A second light generation module, configured to emit a second light beam,
The system according to claim 1, further comprising. The spatial modulation device is further configured to interact with a second light beam to create a second modified light beam, which is the propagation of the second modified light beam. The first aspect of claim 1 comprises a second light spatial pattern having non-uniform intensity along a direction perpendicular to the direction, wherein the second light spatial pattern comprises one or more second light components. Described system. A method of forming a target for extreme ultraviolet (EUV) light sources,
Guiding the light beam on the beam path and
By interacting the light beam with a spatial modulation device positioned on the beam path to form a modified light beam, the modified light beam is directed in the direction perpendicular to the direction of propagation of the modified light beam. Interacting light beams that include a spatial pattern of light with non-uniform intensity along the light, wherein the spatial pattern of light contains one or more components of light.
The interaction of the modified light beam with a target containing a target material that emits EUV light when in a plasma state, wherein at least some of the light components of one or more of the spatial patterns are said to be said. Interacting a modified light beam, which interacts with a region of the target to modify the properties of that region of the target,
A method of forming a target for extreme ultraviolet (EUV) light sources, including. The method of claim 11, wherein the property comprises a density, and modifying the property comprises reducing the density. 11. The method of claim 11, wherein the spatial pattern of light comprises two or more light components. 13. The method of claim 13, wherein all said light components have the same intensity. 13. The method of claim 13, wherein the light component is arranged in a grid and the region of the target that interacts directly with the light component is placed in the grid. 11. The method of claim 11, further comprising interacting with the focus assembly before the modified light beam interacts with the target. The light components are spatially separated and spatially discrete so that a portion of the target between any two light components does not interact with any of the components in the modified light beam. , The method according to claim 13. By interacting the initial target with the second light beam in order to form the modified target, the modified target has a larger range than the initial target in the first direction and is a second. Interacting the initial target with the second light beam, which has a smaller range in the direction than the initial target and the first and second directions are orthogonal to each other.
Interacting the modified light beam with a target comprising a target material that emits EUV light when in a plasma state comprises interacting the modified light beam with the modified target, said one or more. Each of the components of light interacts with a region of the modified target to modify the properties of that region of the modified target, interacting with the modified light beam and interacting with the target.
11. The method of claim 11. Further comprising interacting the modified light beam with the modified target and then interacting with the modified target with a third light beam, wherein the third light beam is of the target material in the modified target. 18. The method of claim 18, which has sufficient energy to convert at least a portion of the plasma to emit EUV light. Further comprising interacting the target with the modified light beam and then interacting the target with another light beam, wherein the other light beam is at least one of the target materials in the second modified target. 11. The method of claim 11, which has sufficient energy to convert a portion into the plasma that emits EUV light. The property includes the amount of EUV light emitted and the conversion efficiency of the other light beam with respect to the energy, and modifying the property of a portion of the target is the conversion efficiency associated with the entire target. 20. The method of claim 20, comprising raising. 20. The method of claim 20, wherein the light beam and the other light beams are temporally connected and are part of a single pulse of light. 11. The method of claim 11, wherein the property comprises the surface area of the target, and modifying the property of any portion of the target comprises increasing the surface area of the entire target. 23. The method of claim 23, wherein the amount of increase in surface area is related to the number of light components in the modified light beam. Interacting the modified light beam with a target comprising a target material that emits EUV light when in a plasma state comprises interacting the modified light beam with a target having a substantially spherical shape. The method according to claim 11.

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