Large scale monochromator

Abstract

X-ray optics that includes a monochromator that includes a substrate having a curved surface and an array of reflecting elements that is supported by the curved surface, the array spans a sagittal angular range that exceeds forty degrees.

Description

LARGE SCALE MONOCHROMATORCROSS REFERENCE

[0001] This application claims priority from US provisional patent serial number 63 / 637,358 filing date April 22, 2024, which is incorporated herein in its entirety.BACKGROUND

[0002] There is a growing need to improve evaluation of samples.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0004] FIG. 1 illustrates an example of a sample and x-ray optics that includes a monochromator and an x-ray source;

[0005] FIG. 2 illustrates an example of a sample and x-ray optics that includes a monochromator and an x-ray source;

[0006] FIG. 3 illustrates an example of a sample and x-ray optics that includes a monochromator and an x-ray source;

[0007] FIG. 4 illustrates an example of a sample and x-ray optics that includes a monochromator and an x-ray source; and

[0008] FIG. 5 illustrates an example of a method.DETAILED DESCRIPTION OF THE DRAWINGS

[0009] The term "about" indicated an allowed deviation of 5, 10, 15 percent or 2, 3, 4, 5, 6, 8 degrees.

[0010] Any reference to any term out of curved, ellipsoid, toroidal or spherical should be applied mutatis to any other term out of curved, ellipsoid, toroidal or spherical. For example - the substrate has a curved surface that may be part of a virtual ellipsoid or may be a part of a virtual toroidal or may be a part of a virtual sphere.

[0011] According to an embodiment there is provided an x-ray optics that includes a monochromator that includes a substrate having a curved surface; and an array of reflecting elements that is supported by the curved surface, the array spans a sagittal angular range that exceeds forty degrees.

[0012] According to an embodiment, the reflecting elements are platelets or multilayer reflectors or a combination of platelets and multilayer reflectors.

[0013] According to an embodiment, the array spans a sagittal angular range that exceeds forty or forty five or fifty or fifty five or sixty or sixty five degrees.

[0014] According to an embodiment, the x-ray optics consists the monochromator.

[0015] According to an embodiment, the array includes three columns and three rows by three platelets.

[0016] According to an embodiment, the array spans a non-dispersive angular range of about 12 degrees.

[0017] According to an embodiment, the array spans along a dispersive direction along a dispersive angular range that is about twelve degrees.

[0018] According to an embodiment, sagittal angular range is about sixty four degrees.

[0019] According to an embodiment, the platelets are multi-layered platelets.

[0020] According to an embodiment, the x-ray optics includes an x-ray source and an analyzer spectrometer.

[0021] According to an embodiment, the monochromator is configured to receive an x- ray beam from the x-ray source and direct a monochromated x-ray towards a sample at a glancing angle of about 54.7 degrees relative to an optical axis of the analyzer spectrometer.

[0022] According to an embodiment, the monochromator is configured to receive an x- ray beam from the x-ray source and direct a monochromated x-ray towards a sample at a glancing angle that does not exceed 54.7 degrees relative to an axis of the spectrometer analyzer.

[0023] According to an embodiment, the monochromator, the x-ray source and the spectrometer analyzer are all positioned on a same side of the sample.

[0024] According to an embodiment, a longitudinal axis of the substrate is parallel to the sample. See, for example, figure 2.

[0025] According to an embodiment, a longitudinal axis of the substrate is oriented to the sample. See, for example, figure 4.

[0026] According to an embodiment, the curved surface is a part of a virtual ellipsoid having a z-axis semi-axis of about thirty nine millimeter and an x-ray source to sample distance that ranges array spans between about twenty millimeters and about twenty five millimeters.

[0027] According to an embodiment, the curved surface is a part of a virtual ellipsoid having a z-axis semi-axis of about thirty nine millimeter and an x-ray source to sample distance that ranges array spans between about sixty millimeters and about seventy five millimeters.

[0028] According to an embodiment, the curved surface is a part of a virtual ellipsoid having a z-axis semi-axis of about thirty nine millimeter and an x-ray source to sample distance is about seventy eight millimeters.

[0029] According to an embodiment, the reflecting elements are platelets and wherein the platelets are crystal platelets that form one or more Bragg reflectors.

[0030] According to an embodiment, the reflecting elements are platelets and wherein the platelets are covered with multilayers that form one or more Bragg reflectors.

[0031] According to an embodiment, the reflecting elements are platelets, and wherein the platelets are made of a material selected of a group consisting of Silicon, Borosilicate glasses, Fused Silica, Sapphire, Calcium Fluoride, or Magnesium Fluoride.

[0032] According to an embodiment, the reflecting elements are platelets, and wherein the platelets have a surface roughness of less than 5 Angstroms.

[0033] According to an embodiment, the reflecting elements are multilayer reflectors - see for example multilayer reflectors 24.

[0034] According to an embodiment, the reflecting elements includes multilayer reflectors formed on platelets - see figure 1 - multilayer reflectors 24 formed on platelets 25.

[0035] There is provided an increase of the primary monochromatic x-ray flux for XPS / XRF HVM near-line / inline metrology to increase metrology throughput for critical applications.

[0036] Metrology for HVM for semiconductor process control using X-ray with energies in 1 - 10 keV or above.

[0037] Metrology for semiconductor process control to carefully control the film composition and thickness, dopant level, impurities, critical dimensions, nanostructures, surface roughness and potential defect levels in order to optimize the semiconductor manufacturing process. This includes but not limited to XPS and XRF

[0038] Advanced semiconductor metrology requires a small spot size (50 um or less) with no more than a couple of percent scatter outside the measurement spot (dependingon X-ray wavelength). Any X-ray outside the measurement area leads to signal contamination from structures outside the intended measurement box.

[0039] Reliable, high throughput is required for XPS, XFR metrology for inline semiconductor manufacturing process. To enable HVM metrology using XPS and or XRF, high quality large area monochromators are required.

[0040] Lab- based XPS instruments employ x-ray monochromators with toroidal or ellipsoidal figure (i.e., AlKa monochromators with Quartz 100 crystals) with relatively small crystal area to provide a narrow monochromatic x-ray band width for high resolution photoelectron spectroscopy. The monochromators in general provide x-ray collection angles of <~10degrees in the non-dispersive and <~ 40degrees in the non- dispersive direction. Primary x-ray flux is usually generated from an anode material irradiated by an electron beam. The permissible e-beam power is limited to the damage threshold of the anode, setting the upper limit of achievable non-monochromatic x-ray flux. The angular acceptance of the monochromator is thus critical and presently limits the achievable monochromatic x-ray flux for micro-focused x-ray beams at the analysis area (conjugate point of the monochromator toroid / ellipsoid). This in turn generally results in long acquisition times to achieve high precision XPS metrology which is incompatible with HVM metrology

[0041] To overcome the limitation of the micro-focused x-ray flux delivered to the wafer analysis point, the monochromator active area is increased by adding crystal platelets in the sagittal direction of the monochromator substrate. One example (and not limited) of a specific implementation is increasing the number of crystal platelets from 3x2 to 3x3 (dispersive / non-dispersive). This results in an increase of the active area of the monochromator in the specific implementation from -12° x42° to -12° x64°, i.e., an estimated increase in micro-focused x-ray flux of 1.5x. The specific implementation does not change the energy width of the monochromatic x-ray beam.

[0042] The actual implementation will permit a monochromatic x-ray flux and thus t- put increase at nominal precision of >1.5x due to the geometry limitation of the system to provide high sensitivity XPS analysis, i.e., a spectrometer configuration collectingphotoelectrons normal to the wafer surface. In addition, the non-monochromatic x-ray source must be located above the wafer surface for HVM in-line metrology.

[0043] The manufacturing process requires a high-precision substrate, including associated metrology, as well as crystal platelet alignment errors <+ / -3uradians to achieve a maximum spot blur of <~ 2.5 microns.

[0044] The technological realization of the system, the monochromator location may be arranged at the “magic angle” for XPS of 54.7° or alternatively at a less glancing angle. The latter would result in an effective relative increase of XPS species with asymmetry parameter beta <2.0 although the overall change in atomic sensitivity factor (ASF) would be <~5% in favor of these species. For accurate calibration purposes of the ASFs, the less glancing portion of the monochromator may be blocked via a removable aperture strip.

[0045] One major advantage is that this technology enables x-ray monochromators with large numerical aperture with high focusing efficiency. Easier to fabricate and lower cost. For example, increasing the number of crystal platelets from 3x3 to 3x6 (dispersive / non-dispersive) will give of ~1.5x for the same non-monochromatic primary x-ray flux. This in turn will enable a metrology throughput enhancement of 1.5x which is of highest relevance for HVM metrology.

[0046] The possibility of enhancing photoelectron species with beta <2 is expected to slightly improve the metrology precision for buried SiCh layers underneath (for example) HfCb as well.

[0047] Ellipsoid, Toroidal, or other types of substrates that can be for focusing soft X- rays having energies from 1.0 keV to 10 keV. Substrates with Clear Aperture area of 140mm X 48mm and larger.

[0048] Ellipsoid, Toroidal, or other types of substrates made from Silicon, Borosilicate glasses, Fused Silica, Sapphire, Calcium Fluoride, Magnesium Fluoride or other suitable materials.

[0049] Thin platelets with surface roughness of less than 5 A while retaining slope and figure errors using a wide range of materials can be used such as, such as Quartz,Germanium, Silicon, LiF422 or other crystals that can be bonded to be conformal to the optical substrate.

[0050] A monochromator with a thin platelet crystal or a plurality of thin platelet crystals arranged in an adjacent array configuration on a substrate to occupy the optical field of view of interest a. Platelets are thin down to 120 um or less to be able to bend and be optically bonded conformal to the substrate. b. Platelets are polished to 0.5 nm or less to be able to be optically bonded c. Substrate ellipsoidal or toroidal are polished to 0.5 nm or less d. The polished side of the platelets are bonded to the polished face of the substrate.

[0051] For the higher energy soft x-rays (~ above 1.0 keV), crystals can be used as Bragg reflectors. a. For example, the most common x-ray energy utilized in XPS is AlKa (1486.7eV) which is typically transported and focused onto a wafer surface via a monochromator. A substrate with a curved surface (for example ellipsoidal or toroidal or spherical) populated with quartz (100) crystal platelets provides point-to point focus of the target emission to the sample surface with an energy bandwidth ~0.5eV. The advantage of these systems is that monochromators with large angular acceptance and thus high transport efficiency can be manufactured. A monochromator focusing system of this type may also transport when optimized for the 1storder Bragg diffraction for AlKa can also focus discrete higher order diffraction orders (energies) according to nk=2d sin(0) (d is the crystal lattice spacing) to the wafer surface. However, the coverage of focusable energies is discrete by nature and intermediate energies other than nZ. equivalent can by design not be transported to the sampling area. Lower x-ray energies are not accessible or focusable at the sample surface with such a monochromator and would require a larger 2d lattice spacing, i.e., Multilayer to be applied to platelets or directly to the substrate.

[0052] The platelet can be fabricated from a crystalline material to allow Bragg reflection from the undeformed crystal planes near the reflecting surface. The thinplatelets can be a material such as Silicon, Borosilicate glasses, Fused Silica, Sapphire, Calcium Fluoride, Magnesium Fluoride or Crystals such as Quartz, Germanium, YB66 or other crystals or any suitable material that can be bonded to be conformal to the optical substrate.

[0053] A monochromator composed of a thin platelet crystal, or a plurality of thin platelet crystals arranged in an adjacent array configuration on a substrate. The number of platelets can be 3x3 or a plurality of thin platelets to cover the optical field of view of interest.

[0054] Platelets can be optically bonded to substrates via multiple methods such as Adhesives, UV activated adhesives, techniques used silicon-to silicon bonding or optical bonding. However, the preferred method is optical bonding. One major disadvantage to other techniques is they cannot be adjusted after bonding.

[0055] Platelets and substrates cleaned by Argon Plasma, oxygen plasma cleaning or UVO cleaning prior to the optically bonding step.

[0056] Figure 1 illustrates an example of x-ray optics 10 and sample 50. The x-ray optics includes a x-ray source such as an anode that is configured to convert electron beam 61 to a x-ray beam 62 that impinges on monochromator 20 to provide monochromated x-ray beam 63 that impinges on sample 50. Monochromator 20 is illustrated as having an array 23 of 3X3 reflecting elements such as platelets 25(1)- 25(9), and substrate 21.

[0057] The base of the substrate has a height of about 219 millimeter, a width of about 58 millimeter and a depth (at the top and bottom of the substrate) of about 64 millimeters. Other dimensions may be provided. The alignment tolerance of the reflecting elements of the array may be, for a spot having a maximal blur of about 2.5 microns - alpha and beta values (angular deviations along two axes) that do not exceed 6 microradians. Othe alignment tolerances may be provided.

[0058] Referring to figures 2-4 - figures 2 and 3 illustrate front views while figure 4 illustrates a side view of x-ray optics of figure 2 and analyzer spectrometer 70 configured to receive electrons 64 emitted from the sample. .

[0059] Figures 2-4 illustrate examples of increased x-ray source distance depends on the design parameter c of the ellipsoid and the x-ray specific Bragg angle. For AlKa (1486.7eV), the Bragg angle is -78.38 degrees and 11.6 degrees with respect to the normal to the crystal, assuming Quartz (100). The aim for XPS measurements is to have a source-to analyzer angle of around 54.7 degrees (the “magic angle” for XPS).For example, and assuming c~39mm, the arrangement in figure 3 allows for a source (anode) to wafer distance and a c~39mm of about 20-25mm, which is mainly driven by distortion of the focus on the wafer due to this elevation, as well as the glancing angle of x-rays with respect to the wafer (some 10 degrees at the extreme). The arrangement in Figure 2 - again providing an x-ray-analyzer angle of 54.7 degrees - on the other hand provides a smaller convergence angle of x-rays with respect to the wafer surface at an average angle of -35.3 + / - -6 degrees. The anode (source) distance to the wafer is now increased to around 78mm as determined by the substrate geometry, as well as the crystal 2d spacing.

[0060] It should be noted that when the energy of the x-ray is below leV (for example when the x-ray is generated from essentially Carbon (277eV or wavelength -44.8A) - then crystals may not be used and multilayer diffractors are used - especially a two dimensional array of multilayer diffractors having spacing slightly larger than 44.8 A - say 45.9A, which would then amount to approximately the same Bragg angle as Quartz (100) for AlKa. In this case, the near identical substrate geometry could be used- if so desired. The multilayer diffractors could be deposited on ultra-smooth («5A) platelets or directly on the substrate and being optically bonded.

[0061] According to an emblement, the platelets are attached to the substrate and the multilayer deposited onto the platelets.

[0062] According to an embodiment, with substrate surface roughness («5A), the multilayer could be directly deposited onto the substrate.

[0063] Figure 5 illustrates an example of method 100 for evaluating a sample.

[0064] Method 100 includes step 110 of receiving an x-ray beam, by a monochromator.

[0065] According to an embodiment, step 110 is followed by step 120 of emitting, by the monochromator a monochromated x-ray beam towards a sample. The monochromator includes a substrate having a curved surface; and an array of reflecting elements that is supported by the curved surface, the array spans a sagittal angular range that exceeds forty degrees.

[0066] According to an embodiment, step 120 is followed by step 130 of detecting, by an analyzer spectrometer, electrons emitted from the sample due to an impingement of the monochromated x-ray beam on the sample.

[0067] In the foregoing detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

[0068] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings.

[0069] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

[0070] Because the illustrated embodiments of the present invention may for the most part, be implemented using electrooptic components known to those skilled in the art, details will not be explained in any greater extent than that considered necessary as illustrated above, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention.

[0071] Any reference in the specification to a method should be applied mutatis mutandis to a system capable of executing the method.

[0072] Any reference in the specification to a system should be applied mutatis mutandis to a method that may be executed by the system.

[0073] In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident thatvarious modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended claims.

[0074] Any reference to “comprising” or “Having” or “including” should be applied, mutatis mutandis to “consisting of’ and / or should be applied, mutatis mutandis to “consisting essentially of’.

[0075] Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein.

[0076] Any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality may be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected," or "operably coupled," to each other to achieve the desired functionality.

[0077] Furthermore, those skilled in the art will recognize that boundaries between the above-described operations merely illustrative. The multiple operations may be combined into a single operation, a single operation may be distributed in additional operations and operations may be executed at least partially overlapping in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments.

[0078] Also, for example, in one embodiment, the illustrated examples may be implemented as circuitry located on a single integrated circuit or within a same device. Alternatively, the examples may be implemented as any number of separate integrated circuits or separate devices interconnected with each other in a suitable manner.

[0079] However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.

[0080] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other elements or steps then those listed in a claim. Furthermore, the terms “a” or“an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an." The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first" and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.

[0081] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

Claims

WE CLAIM1. X-ray optics, comprising: a monochromator that comprises: a substrate having a curved surface; and an array of reflecting elements that is supported by the curved surface, the array spans a sagittal angular range that exceeds forty degrees.

2. The x-ray optics according to claim 1, wherein the reflecting elements are platelets.

3. The x-ray optics according to claim 1, wherein the array spans a sagittal angular range that exceeds sixty degrees.

4. The x-ray optics according to claim 1, wherein the x-ray optics consists of the monochromator.

5. The x-ray optics according to claim 1, wherein the reflecting elements are platelets and wherein the array comprises three columns and three rows by three platelets.

6. The x-ray optics according to claim 1, wherein the array spans a non-dispersive angular range of about 12 degrees.

7. The x-ray optics according to claim 1, wherein the array spans along a dispersive direction along a dispersive angular range that is about twelve degrees.

8. The x-ray optics according to claim 4, wherein sagittal angular range is about sixty four degrees.

9. The x-ray optics according to claim 1, wherein the platelets are multi-layered platelets.

10. The x-ray optics according to claim 1, comprising an x-ray source and an analyzer spectrometer.

11. The x-ray optics according to claim 10, wherein the monochromator is configured to receive an x-ray beam from the x-ray source and direct a monochromated x-ray towards a sample at a glancing angle of about 54.7 degrees relative to an optical axis of the analyzer spectrometer.

12. The x-ray optics according to claim 10, wherein the monochromator is configured to receive an x-ray beam from the x-ray source and direct a monochromated x-ray towards a sample at a glancing angle that does not exceed 54.7 degrees relative to an axis of the spectrometer analyzer.

13. The x-ray optics according to claim 10, wherein the monochromator, the x-ray source and the spectrometer analyzer are all positioned on a same side of the sample.

14. The x-ray optics according to claim 10, wherein a longitudinal axis of the substrate is parallel to the sample.

15. The x-ray optics according to claim 10, wherein a longitudinal axis of the substrate is oriented to the sample.

16. The x-ray optics according to claim 10, wherein the curved surface is a part of a virtual ellipsoid having a z-axis semi-axis of about thirty nine millimeter and an x-ray source to sample distance that ranges array spans between about twenty millimeters and about twenty five millimeters.

17. The x-ray optics according to claim 10, wherein the curved surface is a part of a virtual ellipsoid having a z-axis semi-axis of about thirty nine millimeter and an x-ray source to sample distance that ranges array spans between about sixty millimeters and about seventy five millimeters.

18. The x-ray optics according to claim 10, wherein the curved surface is a part of a virtual ellipsoid having a z-axis semi-axis of about thirty nine millimeter and an x-ray source to sample distance is about seventy eight millimeters.

19. The x-ray optics according to claim 1, wherein the reflecting elements are platelets and wherein the platelets are crystal platelets that form one or more Bragg reflectors.

20. The x-ray optics according to claim 1, wherein the reflecting elements are platelets and wherein the platelets are covered with multilayers that form one or more Bragg reflectors.

21. The x-ray optics according to claim 1, wherein the reflecting elements are platelets, and wherein the platelets are made of a material selected of a group consisting of Silicon, Borosilicate glasses, Fused Silica, Sapphire, Calcium Fluoride, or Magnesium Fluoride.

22. The x-ray optics according to claim 1, wherein the reflecting elements are platelets, and wherein the platelets have a surface roughness of less than 5 Angstroms.

23. The x-ray optics according to claim 1, wherein the reflecting elements are multilayer reflectors .

24. The x-ray optics according to claim 1, wherein the reflecting elements comprise multilayer reflectors formed on platelets.

25. The x-ray optics according to claim 1, wherein the curved surface is a part of a virtual ellipsoid.

26. The x-ray optics according to claim 1, wherein the curved surface is a part of a virtual toroidal.

27. The x-ray optics according to claim 1, wherein the curved surface is a part of a virtual sphere.

28. A method for evaluating a sample, the method comprises: receiving an x-ray beam by a monochromator; and emitting, by the monochromator a monochromated x-ray beam towards a sample; wherein the monochromator comprises a substrate having a curved surface; and an array of reflecting elements that is supported by the curved surface, the array spans a sagittal angular range that exceeds forty degrees.

29. The method according to claim 28, comprising detecting, by an analyzer spectrometer, electrons emitted from the sample due to an impingement of the monochromated x-ray beam on the sample.

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