Patterned X-ray emission target

Abstract

The present invention provides improved patterned X-ray emitting targets, X-ray sources including patterned X-ray emitting targets, X-ray reflection and scattering measurement (XRS) systems utilizing such X-ray emitting targets, as well as X-ray photoelectron spectroscopy (XPS) systems and X-ray fluorescence analysis (XRF) systems.

Description

Technical Field

[0001] (Related Applications) Reference is made to U.S. Patent No. 9,588,066 and U.S. Patent Publication No. 2017 / 0160081, owned by the assignee of this invention, the disclosures of which are incorporated herein by reference in their entirety. This application relates to patterned X-ray emitting targets, X-ray sources including the patterned X-ray emitting targets, and X-ray reflectance scatterometry (XRS) systems, X-ray photoelectron spectroscopy (XPS) systems, and X-ray fluorescence (XRF) systems that use such X-ray emitting targets.

Background Art

[0002] Various types of patterned X-ray emitting targets, X-ray sources including the patterned X-ray emitting targets, and X-ray reflectance scatterometry (XRS) systems, X-ray photoelectron spectroscopy (XPS) systems, and X-ray fluorescence (XRF) systems that use such X-ray emitting targets are known.

Disclosure of the Invention

[0003] This invention provides improved patterned X-ray emitting targets, X-ray sources including the patterned X-ray emitting targets, and X-ray reflectance scatterometry (XRS) systems, X-ray photoelectron spectroscopy (XPS) systems, and X-ray fluorescence (XRF) systems that use such X-ray emitting targets.

[0004] This invention will be more fully understood from the following detailed description in conjunction with the drawings.

Brief Description of the Drawings

[0005]

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Examples

[0006] Referring to FIGS. 1 and 2, FIGS. 1 and 2 are a simplified diagram and a cross-sectional view, respectively, of a patterned X-ray target 100 constructed and operating in accordance with a preferred embodiment of the present invention.

[0007] The patterned X-ray target 100 preferably includes a patterned X-ray impermeable mask 102, which is typically formed of gold and has one or more openings (apertures) 104 that define at least one X-ray passage window. The mask 102 is preferably made of gold having a thickness of about 1 μm. It should be understood that the mask 102 can be made thinner according to the desired blocking rate, and can also be made thicker, such as having a maximum thickness of 2 μm.

[0008] Below the mask 102, an active layer 106, such as a layer of aluminum (Al) having a thickness of preferably about 2 μm, is provided. Alternatively, tungsten (W), tantalum (Ta), magnesium (Mg), or other suitable materials can be selected as the active layer 106.

[0009] Below the active layer 106, a diamond substrate 110 is bonded via a plurality of intermediate layers 108. The plurality of intermediate layers 108 provide a graded transition between the pure metal of the active layer 106 and the carbon diamond crystalline structure of the diamond substrate 110. The intermediate layer 108 facilitates the transition between two different materials, thereby improving the bond between the two materials. Various adoptable structures and compositions of the intermediate layer 108 are described in U.S. Patent No. 7,359,487, the disclosure of which is incorporated herein by reference.

[0010] The diamond substrate 110 preferably has a thickness of 0.5 mm and is located below the intermediate layer 108.

[0011] The properties of the diamond substrate 110 can be changed in several ways. In some situations, it may be desirable to dope the diamond with boron (while reducing the thermal conductivity but increasing the electrical conductivity), thereby allowing the dissipation of charge from the electron beam used to excite X-ray emission. In other situations, the thermal conductivity can be increased by optimizing the impurities, crystal grain size (particle size), grain boundaries, or surface roughness of the diamond.

[0012] Below the diamond substrate 110, a heat sink 114 is bonded via an additional plurality of intermediate layers 112. The intermediate layer 112 can be selected from the group consisting of titanium, chromium, nickel, gold, silver, aluminum, copper, any alloy thereof, and any combination thereof.

[0013] Alternatively, the diamond substrate 110 may be bonded to the heat sink 114 by soldering using one or more intermediate solder layers. The one or more solder layers can be made of a low melting point material that does not cause undue oxidation of the ionizing radiation forming layer when heated to the soldering temperature. The heat sink 114 is preferably composed of a high thermal conductivity material such as beryllium oxide (BeO), tungsten, silicon carbide, aluminum nitride, copper, aluminum, silver, cemented diamond (ScD), and any combination thereof.

[0014] The one or more openings can be of any shape / dimension, such as spot-shaped or strip-shaped (linear, curved, etc.), and define any desired pattern (1D, 2D, periodic, random, etc.). In the case of a strip-shaped opening (trench) (elongated groove), the mask can block an electron beam and / or excited X-rays along only one axis (1D). Such a configuration can be useful, for example, in case grazing angles of X-Ray incidence or when further shaping of the X-rays achieved by directing optics (slits, focusing elements, etc.) is required. The patterned X-ray target 100 and / or the electron beam can be moved continuously or stepwise along one or two axes, for example, along a strip-shaped opening.

[0015] Referring to FIGS. 3 and 4, FIGS. 3 and 4 are a schematic view and a cross-sectional view, respectively, of a patterned X-ray target 200 constructed and operating in accordance with a preferred embodiment of the present invention.

[0016] The patterned X-ray target 200 preferably comprises a patterned X-ray opaque mask 202, which is typically formed of gold and has one or more openings (apertures) 204 that define X-ray passing window(s). The mask 202 preferably has a thickness in the range of about 0.1 μm to 0.2 μm. It should be understood that the mask 202 should not be too thick to avoid “geometrical” obstruction that may occur to the grazing angle exit photons.

[0017] Under the mask 202, a diamond substrate 210 having a thickness of typically 0.5 mm is bonded via a plurality of intermediate layers 208. In this embodiment, the diamond substrate 210 functions as an active layer.

[0018] The properties of the diamond substrate 210 can be changed in several ways. In some situations, it may be desirable to dope the diamond with boron to increase the electrical conductivity (while reducing the thermal conductivity), for example, to dissipate charge from an electron beam used to excite X-ray emission. In other situations, the thermal conductivity can be increased by optimizing the impurities, crystal grain size (particle size), grain boundaries or surface roughness of the diamond.

[0019] The plurality of intermediate layers 208 provide a gradual transition between the carbon diamond crystal structure of the diamond substrate 210 and the pure metal of the mask 202. The intermediate layer 208 facilitates the transition between two different materials, thereby improving the bond between the two materials. The disclosure of U.S. Patent No. 7,359,487, which describes the structure of the intermediate layer 208, is incorporated herein by reference.

[0020] Below the diamond substrate 210, a heat sink 214 is coupled via a plurality of additional intermediate layers 212. The intermediate layer 212 can be selected from the group consisting of titanium, chromium, nickel, gold, silver, aluminum, copper, any alloy thereof, and any combination thereof.

[0021] Alternatively, the diamond substrate 210 may be bonded to the heat sink 214 by soldering using one or more intermediate solder layers. The one or more solder layers can be made of a low melting point material that does not cause excessive oxidation of the ionization radiation forming layer when heated to the soldering temperature. The heat sink 214 is preferably composed of a high thermal conductivity material such as beryllium oxide (BeO), tungsten, silicon carbide, aluminum nitride, copper, aluminum, silver, cemented diamond (ScD), and any combination thereof.

[0022] The one or more openings can be of any shape / dimension, such as spot-shaped or strip-shaped (linear, straight, etc.), and define any desired pattern (1D, 2D, periodic, random, etc.). In the case of a strip-shaped opening (trench), the mask can block an electron beam or excited X-rays along only one axis (1D). Such a configuration can be useful, for example, when the X-ray incident angle is grazing or when further shaping of the X-rays is required by a directional optical system (slit, edge, focusing element, etc.).

[0023] Referring to FIG. 4, the intermediate layer 208 is preferably opened so as to be aligned with one or more openings 204.

[0024] Referring to FIG. 5, FIG. 5 is a simplified schematic diagram of an X-ray inspection system using a patterned X-ray target according to an embodiment of the present invention.

[0025] Referring to FIG. 5, an electron beam 306 is provided by an electron beam gun 310. The electron beam 306 impinges on the surface of an X-ray target 316, preferably an X-ray target of the type described above and shown in FIGS. 1-4, thereby generating ionizing radiation 318, preferably X-rays. The ionizing radiation 318 can be used for any suitable purpose.

[0026] In the illustrated embodiment, the ionizing radiation 318 impinges on a monochromator 320, such as a Bragg crystal monochromator, and preferably the ionizing radiation 327 reflected from the monochromator 320 impinges on a sample 330 disposed on a sample holder 332, more particularly on a target sample surface 334 to be inspected. The reflected ionizing radiation 327, such as X-rays, is reflectable, i.e., scattered by impinging on the sample 330. In addition or alternatively, such impingement may result in the generation of photoelectrons. A suitable detector 340 detects the reflected radiation 342. In one embodiment, the data generated by the detector 340 is transmitted to a computer 350 and further processed to generate useful information and / or an image.

[0027] Referring to FIG. 6, FIG. 6 is a schematic diagram of an X-ray measurement system 700 for XPS or XRF using an X-ray target according to an embodiment of the present invention.

[0028] Referring to FIG. 6, the X-ray measurement system 700 includes an electron beam source 702 that generates an electron beam 704. The electron beam 704 impinges on an X-ray target 706, preferably an X-ray target of the type described above and shown in FIGS. 1-4, thereby generating an X-ray beam 708. A monochromator 709 receives the X-ray beam 708 and generates a monochromatic X-ray beam 710. By using a sample holder 712, a sample 713 can be disposed in the path of the monochromatic X-ray beam 710.

[0029] An XPS detector 714 can be provided for the XPS signal 715 generated by the collision of the monochromatic X-ray beam 710 with the sample 714. Alternatively or in addition, an XRF detector 716 may be provided for the XRF signal 718 generated by the collision of the monochromatic X-ray beam 710 with the sample 714.

[0030] The XRF signal 718 and the XPS signal 715 can be detected simultaneously or almost simultaneously, representing a single sampling event. The XPS signal 715 and the XRF signal 718 result from the detection of photoelectrons and fluorescent X-rays, respectively. In addition, a flux detector 721' may be provided to determine the estimated flux of the monochromatic X-ray beam 710. In one embodiment, the flux detector 721' is arranged in the sample holder 712 as shown in FIG. 6. In other embodiments, the X-ray flux detector 721 is arranged near the monochromator 709 so as to partially intersect a small portion of the primary X-rays of the X-ray beam 708, and the X-ray flux is monitored when the sample holder 712 is arranged at the analysis location.

[0031] The computing system 728 preferably includes a user interface 720, a computing engine 722, and a memory 724. The computing system 728 can be configured to process the XPS signal 715 output by the XPS detector 714 and / or the XRF signal 718 output by the XRF detector 716. The computing system 728 can also be configured to monitor the primary X-ray flux measured by the flux detector 721 or 721'. In one embodiment of the present invention, the computing system 728 operates to normalize the XPS signal 715 detected by the XPS detector 714 and the XRF signal 718 detected by the XRF detector 716 according to the X-ray flux measured by the flux detector 721 or 721'.

[0032] Referring to FIG. 7, FIG. 7 is a schematic diagram of an XRS and / or XRD X-ray measurement system 800 that uses the X-ray target of an embodiment of the present invention and operates to provide X-ray reflectance scatterometry.

[0033] Referring to FIG. 7, the X-ray measurement system 800 includes an electron beam source 802 that generates an electron beam 804. The electron beam 804 impinges on an X-ray target 806, preferably an X-ray target of the type described above and shown in FIGS. 1-4, thereby generating an X-ray beam 808 having an energy preferably of about 1 keV or less. A monochromator 810 receives the X-ray beam 808 and generates a monochromatic X-ray beam 812. A magnetic electron suppression device 813 is provided between the X-ray target 806 and the monochromator 810.

[0034] Preferably by a sample holder 814, a sample 816, preferably having a periodic structure, is placed in the path of the monochromatic X-ray beam 812. The monochromator 810 also operates to focus the X-ray beam 808 and provide a focused monochromatic X-ray beam 812 to the sample holder 814. A detector 818 receives at least a portion of the X-ray beam 819 scattered from the sample 816.

[0035] In the illustrated embodiment, the X-ray target 806 is designed to generate low-energy X-rays, but for higher-energy XRF, the diamond substrate 212 may include molybdenum (Mo) or rhodium (Rh) in addition to carbon.

[0036] It will be apparent to those skilled in the art that the present invention is not limited to what has been particularly shown and described above. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described above that are not in the prior art, as well as modifications and variations thereof.

Claims

1. An X-ray measurement system comprising an X-ray source configured to generate an X-ray beam, the X-ray source including an electron gun configured to generate an electron beam and a patterned X-ray emission target, the patterned X-ray emission target including a gold X-ray block mask having one or more openings, one or more structural elements including an X-ray generation structural element positioned below the X-ray block mask, the one or more structural elements including a top structural element, the X-ray generation structural element being configured to (a) receive electrons of the electron beam passing through one or more openings of the X-ray block mask and (b) generate the X-ray beam and emit the X-ray beam from one or more openings of the X-ray block mask, a sample holder configured to position a sample having a periodic structure, a monochromator positioned between the X-ray source and the sample holder, the monochromator configured to direct the X-ray beam from the X-ray source toward the monochromator and then toward the sample holder, and a detector configured to collect at least a portion of the X-ray beam scattered by the sample. The X-ray measurement system.

2. The X-ray measurement system according to claim 1, wherein at least one of the electron beam and the patterned X-ray emission target moves continuously or stepwise along an axis.

3. The X-ray measurement system according to claim 1, wherein the one or more openings have an arbitrary shape / dimension and an arbitrary desired pattern is defined.

4. The X-ray measurement system according to claim 1, wherein the X-ray generation structural element includes a boron-doped diamond substrate.

5. The X-ray measurement system according to claim 1, wherein the X-ray generation structural element is selected from an X-ray emission layer formed on at least one surface of an X-ray generation substrate or a thermally conductive substrate.

6. The X-ray measurement system according to claim 1, wherein the X-ray generation structural element includes a heat sink, and the heat sink is made of a thermally conductive material selected from beryllium oxide (BeO), tungsten, silicon carbide, aluminum nitride, copper, aluminum, silver, and cemented diamond (ScD).

7. The X-ray measurement system according to claim 1, wherein the thickness of the X-ray block mask is in the range of 0.1 μm to 0.2 μm. ​

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