WO2004012236A2 - Element optique a rayons x a reflectivite et flux eleves et son procede de fabrication faisant intervenir des techniques de depot de couche atomique - Google Patents

Element optique a rayons x a reflectivite et flux eleves et son procede de fabrication faisant intervenir des techniques de depot de couche atomique Download PDF

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WO2004012236A2
WO2004012236A2 PCT/US2003/023753 US0323753W WO2004012236A2 WO 2004012236 A2 WO2004012236 A2 WO 2004012236A2 US 0323753 W US0323753 W US 0323753W WO 2004012236 A2 WO2004012236 A2 WO 2004012236A2
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spacing
bilayer
electron density
bore
substrate
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PCT/US2003/023753
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WO2004012236A3 (fr
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Stephen John Henderson
Steven M. George
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Stephen John Henderson
George Steven M
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Publication of WO2004012236A3 publication Critical patent/WO2004012236A3/fr

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70058—Mask illumination systems
    • G03F7/7015—Details of optical elements
    • G03F7/70166—Capillary or channel elements, e.g. nested extreme ultraviolet [EUV] mirrors or shells, optical fibers or light guides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/06—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diffraction, refraction or reflection, e.g. monochromators
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K2201/00—Arrangements for handling radiation or particles
    • G21K2201/06—Arrangements for handling radiation or particles using diffractive, refractive or reflecting elements
    • G21K2201/067—Construction details

Definitions

  • the present invention relates to x-ray optic elements that provide high reflectivity and therefore high flux.
  • X-rays are used in various analytical methods, such as SAXS (small angle x- ray scattering), WAXS (wide angle x-ray scattering) and XRF (X-ray fluorescent analysis).
  • Laboratory X-ray sources are point or line sources that emit X-rays in diverging directions, so the intensity naturally decreases away from the source according to the familiar inverse square law. Narrow, intense beams are needed for these analytical methods. It is very useful to provide some optic by which the X-ray beam is focused. By focusing the beam, the X-ray flux reaching the target can be increased by several orders of magnitude.
  • the currently most effective X-ray focusing devices are crossed or confocal (so- called) Gobel mirrors.
  • the reflective surfaces of Gobel mirrors are specially designed to increase X-ray flux to the sample by minimizing destructive interference between the reflected X-rays for specific incident angles.
  • the reflective surface of a Gobel mirror is made up of multiple bilayer pairs of materials.
  • the bilayer pairs are very thin, typically on the order of about 10-200 Angstroms.
  • Each bilayer pair consists of a reflective layer and a spacing layer, which are of two different materials.
  • the reflective layer is a relatively high electron density material that reflects a small proportion of incident X-rays.
  • the high electron density material is typically a relatively heavy metal or a material containing a relatively heavy metal.
  • each bilayer reflects only a small proportion of the incident X-rays
  • multiple bilayer pairs are used so that more X-rays are reflected and the overall x- ray flux reaching the sample is increased.
  • This d- spacing (sometimes referred to as the "Bragg" spacing) is the sum of one spacing layer and one reflective layer.
  • This spacing layer is of a lower electron density material that is relatively transparent to the X-rays and acts mainly to space the high electron density layers at the proper distance apart so as to satisfy the Bragg equation.
  • the two most common wavelengths produced in laboratory x-ray sources are 1.54 Angstrom from copper sources and 0.71 Angstrom from molybdenum sources, which are referred to as “characteristic" wavelengths for laboratory sources.
  • Synchrotron X-ray sources are "white” sources, meaning that a broad range of wavelengths are present in similar amount, so any wavelength value can be used in the design of the optic of this invention.
  • the Bragg equation should be satisfied for X-rays reflecting from the entire reflective surface of the optic. Because the angle of incidence ( ⁇ ) varies at varying distances from the X-ray source, the d-spacing should vary as well to preserve the Bragg equation. For most mirror geometries, 0 decreases as one moves further from the X-ray source, so the required d-spacing correspondingly increases with increasing distance from the source. The spacing of the bilayers should in these cases increase continuously along its length. Bilayer pairs having spacings that vary in this manner are said to be "graded". The design of graded bilayer pairs is discussed in detail in U. S. Patent No. 6,226,349, incorporated herein by reference.
  • Atomic layer deposition yields atomic layer controlled thin film growth and produces extremely conformal thin films.
  • An atomic layer deposition method for preparing the bilayer pairs on a flat substrate i.e., an open geometry
  • U. S. Patent No. 5,945,204 is described in U. S. Patent No. 5,945,204 and in H. Kumagai et al., App. Phys. Lett. 70, 2338 (1997) and M. Ish ⁇ et al., J. Crystal Growth 180, 15 (1997).
  • Monocapillary optics consisting of a tube or capillary that is internally profiled in either an elliptical or parabolic shape, are an alternative to Gobel mirrors:
  • Such optical systems are available from, for example, Australian X-ray Crystallography Optics PTY, Ltd. (AXCO) and the Cornell High Energy Synchrotron Sources (CHESS) facility at Cornell University. These systems have the theoretical advantage that they can be located closely to the X-ray source, thereby intercepting a larger solid angle of the source beam and increasing the X-ray flux to the target.
  • These monocapillary tubes are prepared by drawing or pulling heated glass capillaries. However, bilayer pairs have not previously been formed on the internal surfaces of these capillaries.
  • films including bilayer pairs
  • films can be deposited on a tapered mandrel and the mandrel can subsequently be removed to leave a free-standing tube.
  • the process is said to provide capillary optics having bilayer pairs on the internal reflecting surface.
  • this process is very expensive and requires the removal of the mandrel from the completed capillary. This tends to damage the bilayer pairs and impairs performance.
  • Figure 1 is a side view, partly in section, of an X-ray focusing device of the invention.
  • Figure 2 is a schematic illustration of an embodiment of the process of the invention.
  • Figure 3 is a cross-section showing bilayer pairs suitable for forming an X-ray reflecting device of the invention.
  • Figure 4 is a graph showing the measured x-ray reflectivity for a 64 bilayer pair of a W/AI2O3 multilayer with a total thickness of ⁇ 2000 Angstroms.
  • this invention is a method of making an X-ray focusing device having multiple bilayer pairs having a predetermined spacing and each bilayer pair including a reflecting layer and a spacing layer, comprising depositing alternating reflecting layers of a relatively high electron density metal and spacing layers of a relatively low electron density material onto a reflective surface of a substrate via an atomic layer deposition process. This process permits very fine control over the thicknesses of both the metal layers and the spacing layers. This aspect of the invention permits one to produce X-ray optics with metal reflecting layers that provide good X-ray flux to the target as well as a monochromatic beam.
  • this invention is a process of making an X-ray focusing device having multiple bilayer pairs having a predetermined spacing and each bilayer pair including a reflecting layer and a spacing layer, comprising depositing alternating reflecting layers of a relatively high electron density metal and spacing layers of a relatively low electron density material onto a reflective surface of a substrate via an atomic layer deposition process, such that the spacing of the bilayer pairs is graded.
  • This method permits the formation of focusing devices having bilayer pairs in which each layer of the pair has a controllable, predetermined thickness at substantially all points on the reflecting surface.
  • the individual layers have excellent surface smoothness and sharp layer boundaries.
  • this invention is a method of making a tubular X-ray focusing device, comprising depositing multiple bilayers onto an internal surface of a tubular substrate via an atomic layer deposition process, wherein the substrate has an eULiptically or parabolically tapered longitudinal bore with a circular cross-section, the bore being shaped such that a beam entering an entrance end of the bore is reflected to form an elliptically or parabohcally focused beam exiting an exit end of the bore.
  • ⁇ is the angle of incidence of the X-rays at a point on the reflective surface of the focusing device
  • d is the bilayer spacing at such point
  • n is an integer.
  • the bilayers are preferably graded as in the previous aspect.
  • this invention is an X-ray focusing device, comprising a substrate tube having an elliptically or parabohcally tapered longitudinal bore with a substantially circular cross-section, the bore being shaped such that a beam entering an entrance end of the bore from a point source is reflected to form an elliptically- or parabolically-focused beam exiting an exit end of the bore, wherein the longitudinal bore has on its internal surfaces multiple bilayer pairs of ALD-applied materials.
  • the bilayer pair spacing is chosen to satisfy the Bragg equation, as. before, with respect to at least one X-ray having a specific wavelength ⁇ , and is graded as discussed with respect to other aspects above.
  • the tubular focusing device of the invention allows for excellent beam focusing and thus high flux of X-ray beams.
  • the tubular configuration allows the device to be located close to the source of the beam.
  • the tubular device can intercept a large solid angle of the source beam, thereby providing high flux to the target.
  • the focusing device does not use very shallow angles of incidence, as is the case with conventional capillary devices based on critical external reflection, so flux is much higher.
  • highly monochromatic beams can be produced.
  • the spacing of the bilayer pairs is graded along the internal surface of the tube.
  • bilayer pairs are deposited onto a substrate via an atomic layer deposition (ALD) process (also known as atomic layer epitaxy, or "ALE").
  • ALD atomic layer deposition
  • ALE atomic layer epitaxy
  • Each bilayer pair consists of a reflective layer and a spacing layer.
  • the reflective and spacing layers thus alternate, with spacing of the reflective layers being determined by the thickness of the reflective layers themselves and the thickness of the intervening spacing layer.
  • the number of bilayer pairs can be applied in any number, but in practice, standard multilayer theory sets this number for optimum flux based on the x-ray absorption in the spacing and reflecting layers, typically at 50-200 bilayer pairs.
  • the d-spacing, and therefore the thickness of the bilayer pair must be determined uniquely for each device, taking into account the source and the geometry of the system, including the size and geometrical type of the mirror, the distance from the mirror to the source, and the distance from the mirror to the target (either detector or sample).
  • the d-spacing will be of the order of about 10 to about 200 Angstroms.
  • the thickness of the reflecting layer is normally about 15- 40% of the d-spacing, and the thickness of the spacing layer is normally about 60- 85% of the d-spacing, as determined by standard multilayer theory.
  • the geometry of the mirror is usually such that the angle of incidence ( ⁇ ) is not constant for all locations on the reflective surface of the mirror. Accordingly, the required d-spacing is not the same for all locations on the reflective surface of the mirror.
  • a tubular focusing device four inches long located at a distance of four inches from an X-ray point source and having an inner diameter of 0.476 inches at the inlet increasing elliptically to 0.619 inches at the outlet would require a d-spacing of approximately 18 Angstroms at the inlet and 36 Angstroms at the outlet, for a 1.54 Angstrom CuK ⁇ X-ray source.
  • the d-spacings at intermediate positions in the tube will have intermediate values.
  • the precise curvature and dimensions of the focusing device are determined by the choice of elliptical or parabolic styles, the position of the optic, and the locations of the source and target.
  • the geometry of the mirror is not particularly critical to the invention, if the reflective surface of the substrate will focus and monochromate incoming beams as desired.
  • the reflective surface of the device is formed to focus the beams from a point source to either another specific point in space (i.e., elliptical focusing), or to form parallel beams (i.e., parabolic focusing).
  • Tubular substrates that form parallel beams are parabolic in longitudinal cross-section (truncated at both ends), and circular in transverse cross-section.
  • a point source located at the focus of the parabola is reflected to form a parallel, monochromatic beam.
  • Tubular substrates that form point-focused beams are elliptical in longitudinal cross-section (truncated at both ends), and circular in transverse cross-section.
  • a point source located at one focus of the ellipse is reflected to form a monochromatic beam directed to the other focus of the ellipse.
  • FIG. 1 A schematic of a tubular focusing device capable of elliptical (point) focusing is illustrated in Figure 1.
  • X-ray beams 24, 26 and 28 are generated at point source 21 and directed into entrance 30 of tube 22 (shown in section).
  • beams 24, 26 and 28 reflect from interior surface 27 of tube 22 and are directed through exit 29 to a target or detector at point 23.
  • the angle of incidence of a reflected beam is equal to the angle of reflection.
  • These angles are indicated as ⁇ i and ⁇ 2 for beams 24 and 26, respectively.
  • the longitudinal cross-sectional shape of interior surface 27 is that of an ellipse that is truncated at both ends, with the foci of the ellipse being located at point source 21 and target 23.
  • Interior surface 27 is circular in transverse cross-section at every point along its longitudinal axis, so that x-rays hitting any portion of interior reflective surface 27 (or at least a substantial portion of such X- rays) are monochromated and reflected toward point 23.
  • Interior surface 27 has a plurahty of bilayer pairs as described herein.
  • Plug 31 occupies the center of opening 28. It is positioned and sized such that X-rays that enter tube 22 at an angle such that they will not reflect from interior surface 27 are blocked. This prevents unreflected X-rays from interfering with the desired monochromated, focused X-rays that reflect from interior surface 27 toward target 23.
  • the effect of the geometry illustrated by Figure 1 is to produce an el ptically focused (i.e., point-to-point) beam. A parallel beam is produced if the interior reflective surface of the tube is instead longitudinally parabolic in shape.
  • Plug 31 is a means of preventing unfocused, non-monochromated beams from reaching the target. It can be replaced, for example, with a smaller diameter optic as described herein, that is nested within the larger tube and which in turn has a much smaller plug. Such a smaller diameter optic can intersect X-rays that would otherwise not pass through the larger tube due to being blocked by plug 31, monochromating them and focusing them at the intended target, in the same manner as does the larger tube. The effect is to further increase the flux of X-rays to the target.
  • the smaller inner optic would have larger d-spacings on its bilayer pairs in order to compensate for the smaller incident angles on its surface.
  • Tubular focusing devices made in accordance with the invention have a diameter ranging from very small to about 10-40 millimeters.
  • the focusing device of the invention is particularly suitable for focusing so- called "hard" X-rays having an energy of >2.0 keV (corresponding to wavelengths of ⁇ 6 Angstrom). These hard X-rays can be produced by electron beam interaction with metal targets.
  • the two most common wavelengths produced in laboratory X-ray sources are 1.54 Angstroms (8 keV) from copper sources and 0.71 Angstrom (16 keV) from molybdenum sources.
  • the composition of the reflective layer is such that (1) the reflective layer has a relatively high electron density and (2) the reflective layer can be deposited via an ALD process to form a smooth layer adherent to an adjacent spacing layer.
  • the chemical precursors used to make the reflective layer should wet the surface of the spacing layer so that a smooth, adherent reflective layer can be formed.
  • Relatively high electron density materials are typically metals having an atomic number of 25 or greater, particularly 40 or greater, or compounds of such metals, preferably an oxide, nitride or carbide thereof, as discussed in more detail below.
  • the composition of suitable spacing layers for X-ray mirrors is such that (1) the spacing layer is relatively transparent to the "hard" X-rays (of the wavelength for which the mirror is to be used) and (2) the spacing layer can be deposited via an ALD process.
  • Suitable spacing layers include compounds of metals and/or nonmetals having an atomic number below 25, preferably 14 or below. Better performance is usually achieved as the electron density difference of the reflective and spacing layers increases.
  • a difference of atomic number of 15 or more, preferably at least 30 or more, between the metal component of the reflective layer and the highest atomic number element of the spacing layer is particularly suitable. For purposes of comparing atomic numbers, impurities or trace materials consisting of less than 5% by weight of the layer are ignored.
  • Metal/AbOa reflective/spacing layer pairs are particularly useful for reflecting "hard" X-rays.
  • a system of particular interest is a W/AI2O3 system of bilayer pairs.
  • the bilayer pairs are deposited via an ALD technique.
  • Atomic layer controlled growth techniques permit the deposition layers of up to about 3 Angstroms in thickness per reaction cycle, and thus provide a means of extremely fine control over layer thickness.
  • each reflective layer and each spacing layer is formed in a series of two or more self-limited reactions, which in most instances can be repeated to sequentially deposit additional material until the layer achieves a desired thickness.
  • a general description of the ALD process is given in S.M. George et al., "Surface Chemistry for Atomic Layer Growth", J. Phys. Chem. 100, 13121 (1996), incorporated herein by reference.
  • Each set of reactions will generally deposit a film having a thickness approximately equal to a monolayer of the material.
  • a second series of reactions is conducted to deposit the next layer. As before, this second series of reactions may be repeated as necessary until the layer achieves the desired thickness. In this way, alternating spacing and reflective layers, each of a predetermined thickness (as specified by application of the Bragg equation), are produced.
  • the reactants are introduced sequentially in the gas phase. As the reactants are often solids or liquids at room temperature and O 2004/012236
  • the reactants are materials either that are gasses under standard conditions, or which can be volatilized under moderate temperature conditions (preferably at 1000K or below).
  • Preferred reactants have vapor pressures of at least 10 torr or greater at a temperature of 300K.
  • the reactions are generally performed at elevated temperatures, preferably from about 400-1000K, except in cases where the reaction is catalyzed, in which case lower temperatures are sometimes useful so long as the reactants remain in the form of a gas.
  • the substrate is generally held in a chamber that can be evacuated to low pressures.
  • Each reactant is introduced sequentially into the reaction zone, typically together with an inert carrier gas.
  • the reactant reacts at the surface of the substrate to form a thin surface film, as discussed before.
  • the reaction by-products and unreacted reagents are removed before conducting the next reaction. This can be done, for example, by subjecting the substrate to a high vacuum, such as about 10 5 torr or lower, after each reaction step.
  • Another method of accomphshing this is to sweep the substrate with an inert purge gas between the reaction steps.
  • This purge gas can also act as a carrier for the reagents.
  • the next reactant is introduced, where it reacts at the surface of the substrate.
  • the reaction sequence can be repeated as needed to build layers of the desired thickness.
  • the ALD process is not a "line-of-sight" method of depositing the multiple bilayers. Instead, the reactants diffuse isotropically to fill the available space. The reactants cover all surfaces of the substrate, even those surfaces which are not in the direct path of the precursors as they are brought into the reaction chamber and removed. Further, as the reactions are seK-limiting, and the precursors form only monolayer films on the substrate surface during each exposure, the resulting film that is deposited per reaction cycle is highly uniform in thickness. This permits the formation of high quality bilayers on surfaces of substrates having a wide range of geometries.
  • the ALD technique readily facilitates variations in the thickness of the bilayers (and/or their constituent layers) by selectively controlling the number of repetitions of the reaction that occur at various locations on the surface of the substrate. Areas in which thicker bilayers are needed are exposed to a greater number of repetitions of the reaction(s).
  • Layers of variable thickness can be created inside the bore of a tube, for example, by introducing the reactants through a smaller capillary that is inserted into the bore.
  • the capillary can be inserted into either the entrance or exit opening of the bore.
  • areas downstream of the capillary opening are subjected to a larger number of reaction sequences to form a progressively thicker layer.
  • measures are required to prevent the reactants from flowing backwards. This can be accomplished by damming the tube upstream of the capillary opening, but more preferably is done with a positive flow of a viscous flow carrier gas.
  • the direction of flow of the carrier gas is the direction in which the capillary is progressively inserted.
  • the carrier preferably is introduced under laminar flow conditions to avoid turbulence and eddy currents.
  • bilayer pair 37 consisting of reflective layer 36 and spacing layer 35 is deposited, onto, the bore of tube 31.
  • the thickness of layers 35 and 36 and the geometry of the bore of tube 31 are exaggerated, for purposes of illustration.
  • the reactants that are used to form the reflective and spacing layers are introduced into tube 31 through capillary 32, which is inserted into tube 31 through opening 33.
  • a viscous flow carrier gas is flowed through tube 31 as reactants are discharged from capillary 32, in the direction indicated by arrows 39.
  • the flow rate of the viscous flow carrier gas is sufficient to sweep the reactants exiting capillary 32 in the general directions indicated by arrows 38, thereby preventing the reactants from moving upstream of capillary tip 40 (i.e., back toward opening 33).
  • the reactant gases emitted from capillary 32 have to diffuse laterally to reach the walls of tube 31. This diffusion process will lead to some variation of the reactant exposure versus distance from capillary tip 40.
  • Conditions are generally selected (in particular flow rates of the viscous flow carrier gas) so that the lateral diffusion is rapid enough that the variation of the reactant exposures versus distance from capillary tip 40 is minimal.
  • the viscous flow carrier gas has a very rapid velocity
  • the entrainment process together with the diffusion of the reactant gases can produce a large variation of the reactant exposure versus distance from tip 40 of capillary 32.
  • This effect can also be used to form graded layers. In that case, the individual reactions would reach completion where the reactant exposures are the largest and would not reach completion where the reactant exposures are smaller. Since smaller reactant exposures would lead to lower film growth rates, a continuous tapering of the d- spacing can be achieved by controlling the viscous flow carrier gas velocity in the monocapillary tube. Control of the layer thicknesses is more difficult using this method alone.
  • This method can be used in conjunction with the movement of the capillary tube described above to help form smoother gradations in the thickness of the deposited layers. This smoothing helps reduce or eliminate discontinuities in the d-spacing that can be detrimental to the performance of the mirror.
  • the converse procedure works to the same effect.
  • the capillary can be progressively retracted from the tube as the reaction sequences are repeated.
  • means such as a viscous flow carrier gas (in this case flowing in a direction opposite to the capillary movement) are used to prevent the reactants from flowing back upstream of the capillary tip.
  • the movement of the capillary allows different number of ALD reactant cycles to be applied to the tube at different locations. In this case, thinner layers are formed as one progresses down the bore in the direction of the retracting smaller tube.
  • Mirror surfaces of other geometries can be coated with graded multiple bilayers using variations of the same principles described above. Different functional forms for the variation in the d-spacing can be created depending on the exact movement of the capillary versus time and the viscous flow carrier gas velocity.
  • the ALD process begins by introducing some functional group on the exposed surface, such as an M-H, M-O-H or M-N-H group, where M represents an atom of a metal or semi-metal.
  • the substrate should be treated before initiating the reaction sequence to remove volatile materials that may be absorbed onto the surface. This is readily done by exposing the substrate to elevated temperatures and/or vacuum.
  • a precursor reaction may be performed to introduce desirable functional groups onto the surface of the substrate.
  • a specific reaction scheme described therein involves sequential reactions of a substrate surface with a metal halide followed by a metal halide reducing agent.
  • the metal of the metal halide is preferably a transition metal or a semimetallic element, including tungsten, rhenium, molybdenum, antimony, selenium, tellurium, platinum, ruthenium and iridium.
  • the halide is preferably fluoride.
  • the reducing agent is suitably a silylating agent such as silane, disilane, trisilane and mixtures thereof. Other suitable reducing agents are boron hydrides such as diborane.
  • M is a surface metal or semimetal.
  • the asterisk (*) indicates the species that resides at the surface of the substrate or deposited film.
  • Another binary reaction scheme suitable for depositing a metal (M 2 ) film on a substrate having surface hydroxyl or amine groups can be represented as:
  • R refers to an organic Mgand such as alkyl, alkylamino or acetylacetonate species
  • Z represents oxygen or nitrogen
  • X is a displaceable nucleophilic group.
  • the asterisk (*) refers to the species residing at the surface.
  • the spacing layers for X-ray mirrors are suitably oxides, carbides or nitrides of metals or semimetals, preferably metals or semimetals having a valence of 3 or 4 and an atomic number of less than 25, preferably 14 or below.
  • Other suitable spacing lawyers include single-element species with low atomic number such as silicon or carbon.
  • suitable materials for spacing layers which can be deposited via an ALD technique, include alumina (AI2O3), silica (Si ⁇ 2), titanium oxide (Ti ⁇ 2), boron nitride (BN), aluminum nitride (AIN) and silicon nitride (Si3N ).
  • Single element spacing layers such as silicon can also be deposited by an A T) technique using hydrogen radicals.
  • spacing layers are selected not only for their transparency to X-rays, but in addition for their ability to adhere to the reflective layer and form smooth, sharp layer boundaries. Spacing layers made from amorphous materials tend to form smoother layer boundaries. Thus, in any particular case, the composition of the spacing layer is typically selected in conjunction with that of the reflective layer to obtain the optimum reflectivity.
  • Oxide spacing layers can be prepared on an underlying substrate or layer having surface hydroxyl or amine groups using a binary (AB) reaction sequence as follows.
  • the asterisk (*) indicates the species that resides at the surface, and Z represents oxygen or nitrogen.
  • M 1 is an atom of the metal (or semimetal such as silicon), particularly one having a valence of 3 or 4, and X is a displaceable nucleophihc group.
  • the reactions shown below are not balanced, and are only intended to show the reactions at the surface (i.e., not inter- or intralayer reactions).
  • reaction A3 reagent M x Xn reacts with the M*-Z— H groups on the surface to create a new surface group having the form — M*-Xn- ⁇ .
  • M 1 is bonded through one or more Z (nitrogen or oxygen) atoms.
  • the -M 1 — Xn-i group represents a site that can react with water in reaction B3 to regenerate one or more hydroxyl groups.
  • the hydroxyl groups formed in reaction B3 can serve as functional groups through which reactions A3 and B3 can be repeated, each time adding a new layer of M 1 atoms.
  • hydroxyl groups can be eliminated as water, forming M D-M 1 bonds within or between layers.
  • This condensation reaction can be promoted if desired by, for example, annealing at elevated temperatures and/or reduced pressures.
  • a preferred spacing layer material for X-ray mirrors in the hard X-ray region is alumina.
  • An example of an overall reaction for depositing an alumina coating is 2A1(CH3)3 + 3 H2O -> AI2O3 + 6 CH 4 . This overall reaction can be spht into a sequence of reactions represented as:
  • Analogous reaction sequences can be performed to produce nitride and sulfide coatings.
  • An illustrative reaction sequence for producing a nitride coating is:
  • Ammonia can be ehminated to form M tf-M 1 bonds within or between layers. This reaction can be promoted if desired by, for example, annealing at elevated temperatures and/or reduced pressures.
  • a suitable binary reaction scheme for depositing an inorganic nitride coating, such as Si ⁇ i is described in J. W. Klaus et al, Surf. Sci, 418, L14 (1998), incorporated herein by reference.
  • An illustrative reaction sequence for producing a sulfide coating is: . .
  • Hydrogen sulfide can be ehminated to form M 1 -S-M 1 bonds within or between layers. As before, this reaction can be promoted by annealing at elevated temperatures and/or reduced, pressures.
  • a suitable binary reaction scheme for depositing an inorganic phosphide coating, such as AIP, is described in M. Ish ⁇ et al, Crystal. Growth 180, 15 (1997), incorporated herein by reference.
  • suitable replaceable nucleophihc groups will vary somewhat with M 1 , but include, for example, fluoride, chloride, bromide, alkoxy, alkyl, acetylacetonate, and the like.
  • Specific compounds having the structure M ⁇ that are of particular interest are sihcon tetrachloride, tetramethylorthosUicate (Si(OCH3) 4 ), tetraethyl-orthosilicate (Si(OC2Hs)4), trimethyl aluminum (A1(CH3)3), triethyl aluminum (A1(C H5)3), other trialkyl aluminum compounds, and the like.
  • Ci and C2 represent catalysts for the A7b and B7b reactions, and may be the same or different.
  • Each R represents a functional group (which may be the same or different), and M and M 1 are as defined before, and can be the same or different.
  • Reactions A7a and A7b together constitute the first part of a binary reaction sequence, and reactions B7a and B7b together constitute the second half of the binary reaction sequence.
  • An example of such a catalyzed binary reaction sequence is:
  • vibrational spectroscopic studies can be performed using Fourier transform infrared techniques.
  • the deposited coatings can be examined using spectroscopic elhpsometry or X-ray reflectivity.
  • Atomic force microscopy studies can be used to characterize the roughness of the coating relative to that of the surface of the substrate.
  • Depth-profiling X-ray photoelectron spectroscopy can be used to determine the elemental composition and chemical state of the atoms in the film.
  • X-ray diffraction can ascertain the crystallographic structure of the coating.
  • ALD-deposited layers tends to be relatively uniform per AB reaction cycle, so that layer thickness is usually predictable from the number of cycles that are repeated.
  • AI2O3 is typically deposited via ALD at a growth rate of 1.1-1.2 Angstroms per reaction cycle at 180°C.
  • tungsten is deposited at a growth rate of about 2.5 Angstroms per reaction cycle at 180°C.
  • the deposited spacing or reflective layer may be polycrystaUine.
  • This polycrystalline structure may cause some interfacial roughness between adjacent layers.
  • an impurity may be introduced during the formation of polycrystalline layers in order to suppress the crystalhnity somewhat and produce a smoother interface.
  • carbon can be added in -the form of a gaseous hydrocarbon (such as ethylene) during the ALD process for forming metals such as tungsten. The hydrocarbon will decompose under the conditions of the ALD process to add carbon impurities. .
  • Example 1 is provided to illustrate the invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated. Example 1
  • FIG. 3 is a cross-sectional transmission electron microscope (TEM) image of the resulting structure prepared in accordance with this example.
  • Alternating reflective layers 61 (W, tungsten) and spacing layers 62 (AI2O3, alumina) are shown as deposited onto a silicon [Si(100) ⁇ substrate 63.
  • This superlattice is composed of four AI2O3 W bilayers 64. Each individual layer is deposited using a sufficient number of AB cycles to form individual AI2O3 and W layers approximately 125 A thick.
  • the layers in this example are somewhat thicker than would generally be useful to focus X-rays.
  • the greater layer thicknesses are selected in this Example to allow for good TEM imaging of the multilayer structure, so that layer uniformity and thickness control are more easily illustrated.
  • the AI2O3 layers 62 are grown using a t ⁇ -t2-t3-t 4 sequence of 1-5-1-5 where ti is the TMA reactant pulse time, t 2 is the subsequent purge time, t3 is the H2O reactant pulse time and t 4 is the subsequent purge time. The times are all in seconds.
  • the AI2O3 layers 62 are each deposited using 111 such TMA/H2O AB cycles at 177 °C.
  • FIG. 3 there is an interfacial oxide layer 66 of ⁇ 15 A at the interface between the Si(100) substrate 63 and the first AI2O3 layer 62.
  • This Si ⁇ 2 layer results from the partial oxidation of the sihcon substrate.
  • the tungsten layers 61 are deposited using a t ⁇ -t2-t3-t 4 sequence of 10-5-1-5 where ti is the Si2H ⁇ reactant pulse time, t2 is the subsequent purge time, t3 is the WF ⁇ reactant pulse time and t 4 is the subsequent purge time.
  • the tungsten layers 61 are each deposited using 32 Si2H6/ F6 AB cycles at 177°C. Fewer AB cycles are required to deposit the tungsten layers because each W ALD AB cycle has a much larger growth rate (about 2.5 Angstroms/cycle) than the AI2O3 ALD AB cycle (1.1-1.2 Angstroms/cycle) .
  • Figure 3 illustrates how the AI2O3 layers 62 and W layers 61 can be produced controllably and reproducibly.
  • the interface between the top of each AI2O3 layer and the next tungsten layer is extremely smooth in each instance because the AI2O3 layers are amorphous and nearly atomically smooth.
  • the interface between the top of each tungsten layer and the succeeding AI2O3 layer displays some greater roughness because the tungsten layers are polycrystalline. Depositing the AI2O3 layer atop the underlying tungsten layer results in some smoothing of this roughness, as shown in Figure 3.
  • the bilayer spacing is the sum of the thickness of each bilayer pair, i.e., the sum of the thickness of a tungsten layer 61 and an adjacent alumina layer 62.
  • X-ray diffraction measurements indicate that the tungsten layers are polycrystalline and alumina layers are amorphous.
  • the polycrystalline grains are consistent with an ⁇ -W which has a body-centered cubic structure.
  • the x-ray diffraction peaks are very broad as expected for extremely small polycrystalline grains.
  • Depth-profiling secondary ion mass spectrometry (SIMS) measurements further confirm the chemical identity of these W and AI2O3 layers. In agreement with the TEM image, an extremely sharp interface is observed at each W/AI2O3 interface.
  • SIMS depth-profiling secondary ion mass spectrometry
  • ALD methods as generally described in Example 1 are used to deposit 64 AI2O3/W bilayer pairs onto a sihcon substrate.
  • the 64 pairs have a total film thickness of approximately 2000 Angstroms.
  • the d-spacing for each bilayer is approximately 30 Angstroms;
  • Each W and AI2O3 layer has a thickness of approximately 15 Angstroms.
  • X-ray reflectivity measurements are performed with samples that are overfilled by the x-ray beam at close to grazing incidence.
  • Very pronounced Brag peaks, or so-called “satellite” peaks are observed from the AI2O3 W multilayer.
  • These pronounced Bragg peaks or so-called “satellite” peaks are displayed in Figure 4.
  • the reflected X-ray intensity is plotted against incident angle for a 1.54 Angstrom CuK ⁇ X-ray beam.
  • the sample is aligned parallel to the incident x- ray beam and the sample blocks one-half of the incident intensity.
  • the x-ray intensity initially drops because of geometric factors related to the beam overfilling the sample.
  • the critical angle at ⁇ 0.4° the x-rays begin to penetrate the sample and the x-ray intensity then decreases inversely with ⁇ 4 .
  • the Bragg peak or so-called "satellite” peak is observed at ⁇ 1.5°.
  • the x-ray intensity for this peak is large and nearly approaches the intensity for total external reflection. Since the entire beam is reflected for total external reflection, this reflectivity is on the order, but somewhat less, than unity.

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Abstract

L'invention se rapporte à un procédé de formation de bicouches multiples sur un substrat utilisant un procédé de dépôt de couche atomique. La couche réfléchissante de la paire de bicouches peut être un métal à haute densité d'électrons et la couche d'espacement de la paire de bicouches peut être une matière à faible densité d'électrons. Du fait que le dépôt de couche atomique peut déposer des films enrobants et à coche atomique contrôlée, on peut déposer de multiples bicouches sur les surfaces internes de tubes monocapillaires. En appliquant une bicouche multiple superposée, on peut obtenir des éléments optiques à réflectivité et flux plus élevés que ceux utilisant une réflexion externe totale. Le dépôt d'une bicouche multiple superposée sur un tube conique elliptique ou parabolique donne lieu à une sortie focalisée ou collimatée provenant d'une entrée source ponctuelle. L'invention se rapporte également à différentes techniques de dépôt de couche atomique permettant d'obtenir des dispositifs de focalisation à rayons X de qualité présentant une bicouche multiple superposée, plus précisément pour des rayons X « durs ».
PCT/US2003/023753 2002-07-30 2003-07-30 Element optique a rayons x a reflectivite et flux eleves et son procede de fabrication faisant intervenir des techniques de depot de couche atomique WO2004012236A2 (fr)

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US9360603B2 (en) 2009-10-26 2016-06-07 Max-Planck-Gesellschaft Zur Forderung Der Wissenschaften E.V. Method and apparatus for producing a Fresnel zone plate
US9859028B2 (en) 2012-03-08 2018-01-02 Max-Planck-Gesellschaft Zur Foerderung Der Wissenschaften E.V. Method of producing a Fresnel Zone Plate for applications in high energy radiation
EP3282294A1 (fr) * 2016-08-12 2018-02-14 Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. Réseau de plaques à zones de fresnel haute résolution à matériau plein et son procédé de fabrication

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US4764398A (en) * 1985-04-02 1988-08-16 Ramot University Authority For Applied Research And Industrial Development Ltd. Method of depositing coatings on the inner surface of a tube by chemical vapor deposition
US5458084A (en) * 1992-04-16 1995-10-17 Moxtek, Inc. X-ray wave diffraction optics constructed by atomic layer epitaxy
US5945204A (en) * 1995-01-19 1999-08-31 Ridagaku Kenkyusho Multilayer film structure for soft X-ray optical elements
US5768339A (en) * 1995-10-13 1998-06-16 O'hara; David B. Collimator for x-ray spectroscopy
US5772903A (en) * 1996-09-27 1998-06-30 Hirsch; Gregory Tapered capillary optics
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Publication number Priority date Publication date Assignee Title
US9360603B2 (en) 2009-10-26 2016-06-07 Max-Planck-Gesellschaft Zur Forderung Der Wissenschaften E.V. Method and apparatus for producing a Fresnel zone plate
EP2504725B1 (fr) * 2009-10-26 2017-06-21 Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. Procédé et dispositif pour fabriquer une plaque à zones de fresnel
US9859028B2 (en) 2012-03-08 2018-01-02 Max-Planck-Gesellschaft Zur Foerderung Der Wissenschaften E.V. Method of producing a Fresnel Zone Plate for applications in high energy radiation
EP3282294A1 (fr) * 2016-08-12 2018-02-14 Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. Réseau de plaques à zones de fresnel haute résolution à matériau plein et son procédé de fabrication
WO2018029348A1 (fr) * 2016-08-12 2018-02-15 MAX-PLANCK-Gesellschaft zur Förderung der Wissenschaften e.V. Réseau de plaques à zone de fresnel en matériau plein haute résolution et son procédé de fabrication

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