Microstructures for selective transmission of electromagnetic radiation

Abstract

A method (100) for manufacturing a microstructure for selective transmission of electromagnetic radiation comprises the steps of: a) irradiating (110) one or more regions of a substrate (14) according to a predefined geometry of the microstructure with a first laser radiation (12) to cause a structural modification of a material in the irradiated one or more regions, the one or more regions are irradiated such that once the substrate is subjected to etching, the etching occurs at a higher rate at the one or more regions that are irradiated than at regions that are not irradiated; b) performing (120) the etching to form a plurality of first openings (16) in the substrate having the predefined geometry of the microstructures; c) filling (130) the first opening (16) with at least one radiation opaque material (18) having a desired radiation attenuation spectrum to form a radiation absorbing diaphragm wall structure of the microstructure; and d) irradiating (140) one or more non-irradiated regions according to the predefined geometry of the microstructure with a second laser radiation, and performing an etching to form a plurality of second openings (20) between the plurality of first openings, where the second openings (20) are not filled with any radiation opaque material, and where the second openings (20) are not filled with any radiation opaque material. Thereby the second opening is radiation transparent. The proposed method can cope with increased requirements for mass, area uniformity, robustness and / or cost reduction, which is required to achieve new medical imaging methods (e.g., spectral X-ray imaging and phase contrast imaging).

Description

Technical Field

[0001] The present invention relates to a method and a system for producing a microstructure for selectively transmitting electromagnetic radiation, a microstructure obtained by the method and an imaging component comprising the microstructure. Background Art

[0002] WO2021239302A1 describes a method for introducing a recess in the form of a notch into a substrate by partially reducing the material thickness. Spatial beam forming of a laser beam along the beam axis causes modifications in the substrate, so that the recess is subsequently created by the action of an etching medium.

[0003] US5231654A describes a collimator for an imaging system. The collimator can be fabricated by forming a mask on a photosensitive collimator substrate, exposing the photosensitive substrate to a beam traveling along a path corresponding to the direct path of radiation from a radiation source to detector elements in an assembled array, etching the collimator substrate to form channels therein along the exposed areas of the substrate, and coating the substrate with a radiation absorbing material.

[0004] CN109507828A relates to a method for manufacturing a display device capable of producing a display device having an anti-ejection function and capable of displaying a display screen.

[0005] US2022 / 077270A1 describes a display device comprising: a base substrate comprising a rigid material; a plurality of pixels arranged on a display area of ​​the base substrate; a vertical conductive member arranged to pass through the display area of ​​the base substrate; a first transfer wiring electrically contacting the vertical conductive member and extending in a horizontal direction; and a lower panel driver arranged below the base substrate and electrically connected to the vertical conductive member.

[0006] US 2021 / 065923 A1 relates to a grating for X-ray phase contrast and / or dark field imaging. It describes forming a photoresist layer on the surface of a substrate. Using a mask representing the desired grating structure, the photoresist layer is irradiated with radiation.

[0007] JP2002318283A aims to provide a two-dimensional array radiation detector that removes two-dimensional scattered X-rays. Using a photomask, a flat-plate photosensitive glass is exposed to an ultraviolet light source at a pitch (n) times the pixel pitch of the X-ray detection portion to undergo heat treatment for crystallization. After further exposure, etching is performed to form grating grooves in the direction of X-ray incidence. The grooves are then filled with X-ray absorbers to produce a grid having a two-dimensional top surface longitudinal groove shield and a top surface transverse groove shield on the top surface, and a two-dimensional reverse surface longitudinal groove shield and a reverse surface transverse groove shield on the reverse surface.

[0008] US5389473A describes a method for producing an X-ray grid, according to which a panel or plate of photosensitive material is exposed through a mask, then developed to produce a hidden image, and etched, wherein, according to a novel feature of the invention, the photosensitive material is a photosensitive glass with a solubility difference of not less than 25, and the exposure is carried out using radiation with a wavelength shorter than that of ultraviolet radiation, for example by X-ray radiation or gamma radiation.

[0009] Medical X-ray and gamma-ray imaging systems often employ imaging components that include high-aspect ratio microstructures that absorb a portion of the high-energy photons used to create the image. Typical examples are: (1) X-ray anti-scatter grids (ASGs), which partially remove X-rays scattered by the patient's anatomy from the primary X-ray beam in order to enhance the contrast of the imaged tissue; and (2) X-ray absorption gratings, which generate contrast caused by the attenuation, phase shift, and small-angle scattering properties of the imaged object. These large-area components often include fine, high-aspect-ratio radiation-absorbing high-Z material structures (e.g., Pb, W, Au, etc.) embedded in a matrix of poorly radiation-absorbing low-Z materials (e.g., carbon, fiber, aluminum, etc.).

[0010] Continuous improvements in current imaging technologies for interventional applications and image-guided radiation therapy, such as 3D imaging (e.g., cone-beam computed tomography (CBCT)), and the emergence of new clinical X-ray applications (e.g., spectral X-ray imaging and phase contrast imaging (PCI)), place stricter demands on the quality, areal uniformity, manufacturing robustness, and cost of these components.

[0011] Unfortunately, current fabrication methods for ASGs and gratings are not expected to meet these future demands. Furthermore, these methods may not be robust and flexible enough to fabricate a wide variety of custom imaging components. Summary of the Invention

[0012] It is an object of the present invention to provide an improved method of manufacturing microstructures for selective transmission of electromagnetic radiation, such as microstructured imaging elements in X-ray and gamma-ray imaging.

[0013] The invention is defined by the independent claims. Advantageous embodiments are defined in the dependent claims. It should be noted that the aspects of the invention described below also apply to the method and system for producing a microstructure for selective transmission of electromagnetic radiation, the microstructure obtained by the method, and the imaging component.

[0014] According to a first aspect of the present invention, there is provided a method for manufacturing a microstructure for selectively transmitting electromagnetic radiation, the method comprising the following steps:

[0015] a) irradiating one or more areas of the substrate according to the predefined geometry of the microstructure with a first laser radiation to cause a structural modification of the material in the irradiated one or more areas, such that once the substrate is subjected to etching, the etching occurs at a higher rate at the irradiated one or more areas than in non-irradiated areas;

[0016] b) performing the etching to form a plurality of first openings having the predefined geometry of the microstructure in the substrate;

[0017] c) filling said first opening with at least one radiation opaque material having a desired radiation attenuation spectrum to form a radiation absorbing membrane wall structure of said microstructure; and

[0018] d) irradiating one or more unirradiated areas according to the predefined geometry of the microstructure with a second laser radiation and performing etching to form a plurality of second openings between the plurality of first openings, wherein the second openings are not filled with any radiation-opaque material, whereby the second openings are radiation transparent.

[0019] The present disclosure proposes a new scalable process technology platform for fabricating microstructured components (e.g., high-aspect ratio microstructured imaging components) for X-ray and gamma-ray imaging. Laser microfabrication is used to create focused high-aspect ratio trenches in a substrate (e.g., a transparent, large, low-Z substrate (e.g., glass)), and then fill these trenches with a radiation energy absorbing material such as a high-Z material (e.g., tungsten).

[0020] The large laser beam writing flexibility can enable the generation of high aspect ratio microstructures with different heights, wall thicknesses, aspect ratios, pixel shapes, pixel spacing, etc. across the substrate. Etching is preferably performed by subjecting the substrate to wet chemical etching (e.g., using KOH or HF-based solutions). However, other forms of etching are also contemplated (e.g., plasma etching, etching using gases such as fluorine-containing gases, etc.).

[0021] Examples of microstructures include, among others, an ASG having a high grid ratio at the center and a lower grid ratio toward the periphery, or a bow-tie filter constructed by a patterned structure having an X-ray absorptivity that gradually increases from its center toward the periphery. Thus, the proposed method for manufacturing these components can address the increasing demands for quality, area uniformity, robustness, and / or cost reduction required to realize new medical imaging methods (e.g., spectral X-ray imaging and phase contrast imaging).

[0022] Step d) of the method increases the transmission of primary radiation (e.g., X-rays) through a radiation-transmitting selective microstructure (e.g., an ASG). Second openings are formed in the (glass or plastic) substrate, and these second openings are not filled with a radiation-opaque material. In this way, the primary transmission of radiation through the openings between the filled walls in the first openings is increased compared to the radiation-absorbing walls and compared to portions of the substrate without the second openings.

[0023] A plurality of radiation-absorbing walls form a microstructure (e.g., a one-dimensional or two-dimensional grid or grating). Because the laser-fabricated grooves are filled with a radiation-opaque material, dense and high-aspect-ratio radiation-absorbing walls can be created. Second openings are located between the radiation-absorbing walls (e.g., in the pixels of the grid). The second openings have the opposite function compared to the filled first openings. The second openings are effectively transparent to radiation, allowing radiation to pass through with no attenuation or with low attenuation. The effect of the second openings can be achieved by not filling these openings with any material, because the radiation passes through less substrate material than in areas without secondary openings. However, to improve stability, it is also conceivable that the second openings are filled with another radiation-transparent material that has greater transparency to electromagnetic radiation than the substrate. Such transparent materials can include optical and porous materials. An example of a material that has greater transparency to electromagnetic radiation than the substrate can be an aerosol (e.g., a polymer-reinforced aerosol).

[0024] The quality improvement of a radiation-transmitting selective microstructure (e.g., an anti-scatter grid for imaging) can be defined by its ability to remove / absorb scattered photons while transmitting as many primary photons as possible. Thus, the performance of a radiation-transmitting selective structure is improved by having first openings filled with a radiation-opaque material to create dense, radiation-absorbing walls with a high aspect ratio, and second openings between the walls that provide high primary transmission.

[0025] This will be discussed below and in particular with regard to Figure 1 and Figure 2 The example shown is explained in detail.

[0026] A radiation opaque material is a material that does not actually or at least partially allow radiation (e.g., X-ray radiation) to pass through the material. The radiation opaque material may include a high-Z material. A high-Z material is a material (element) with a high atomic number Z that provides good absorption of X-ray and gamma-ray radiation, which is beneficial, for example, for absorbing scattered radiation through the grid. The high-Z material is preferably a metal. The high-Z material may be tungsten (Wolfram, W, atomic number 74). Other examples of high-Z materials include molybdenum (Mo, atomic number 42), tantalum (Ta, atomic number 73), niobium (Nb, atomic number 41), lead (Pb, atomic number 82), bismuth (Bi, atomic number 83), rhenium (Re, atomic number 75), silver (Ag, atomic number 47), and gold (Au, atomic number 79). The high-Z material preferably has an atomic number Z greater than 40, more preferably greater than 70. The radiation opaque material may alternatively or additionally or in combination comprise an alloy comprising at least one high-Z material.

[0027] According to an embodiment of the present invention, a ratio of depth to width of one or more of the first openings is greater than or equal to 10, optionally greater than or equal to 100.

[0028] Medical X-ray and gamma-ray imaging systems often employ imaging components that include high-aspect-ratio microstructures that absorb a portion of the high-energy photons used to create the image. Examples are X-ray anti-scatter grids, absorption gratings, collimators, bow-tie filters, and energy filters.

[0029] Therefore, the methods described herein can provide a scalable process technology platform to fabricate a variety of high-aspect-ratio microstructured imaging features in X-ray and gamma-ray imaging.

[0030] According to an embodiment of the present invention, the substrate includes a glass material or a plastic material.

[0031] According to an embodiment of the invention, at least one of the first laser radiation and the second laser radiation is generated by a focused pulsed femtosecond laser.

[0032] Femtosecond laser micromachining technology has demonstrated the manufacturability of various monolithic integrated devices (e.g., optofluidic devices, optomechanical devices, and photonic devices). Since glass (e.g., fused quartz), polymers, dielectrics, or crystals are commonly used as transparent substrate materials, the laser beam can be focused almost anywhere inside the substrate material, and energy can be deposited almost anywhere in the volume. Energy deposition causes structural modifications to the material, causing subsequent etching to occur at a much higher rate at exposed areas than at non-exposed areas. This locally enhanced etching sensitivity (etching selectivity) depends on various femtosecond laser parameters (e.g., pulse duration, pulse energy, and repetition rate).

[0033] According to an embodiment of the present invention, the method further comprises: bending the substrate in one or two dimensions to shape the substrate according to a desired curvature.

[0034] Some X-ray imaging systems (e.g., standard CT, curved CBCT) may include an ASG or grating that is curved rather than flat. In this case, microfabrication of the desired membrane wall structure can still occur on a thin, flat substrate, which can then be slightly curved in one or two dimensions (e.g., using a mold at elevated temperature) to meet the desired curvature.

[0035] According to an embodiment of the invention, the first openings are angled towards a common focus.

[0036] In many X-ray imaging applications, focusing ASGs and gratings are used where the grooves are angled towards a common focal point in the X-ray source.

[0037] This laser-based structuring method as described herein can enable accurate positioning of angled membrane wall structures across the entire substrate. This will be discussed below and in particular with respect to Figure 1 and Figure 2 The example shown is explained in detail.

[0038] According to an embodiment of the present invention, in step c), the first opening is filled with at least two materials, and the at least two materials have different radiation attenuation spectra.

[0039] High aspect ratio material structures may enable modulation of the spatial energy of an incident X-ray beam by applying different X-ray absorbing materials in the septum walls.

[0040] According to an embodiment of the present invention, the electromagnetic radiation includes at least one of gamma radiation or X-ray radiation.

[0041] Examples of medical imaging systems that can benefit from microstructures can include, but are not limited to, X-ray equipment (e.g., mammography equipment), computed tomography (CT) scanners, single photon emission computed tomography (SPECT) equipment, and positron emission tomography (PET) scanners.

[0042] According to a second aspect of the present invention, there is provided a microstructure for selective transmission of electromagnetic radiation obtainable by a method according to the first aspect and any associated examples.

[0043] Figure 3 An example of a microstructure is illustrated.

[0044] According to a third aspect of the present invention, there is provided an imaging component including a microstructure.

[0045] Examples of imaging components include microstructure imaging components in X-ray and gamma-ray imaging, such as X-ray anti-scatter grids, absorption gratings, collimators, bow-tie filters, and energy filters, among others. Figure 5 An example of an imaging component is shown.

[0046] According to an embodiment of the present invention, the imaging component includes a plurality of stacked microstructures.

[0047] Compared to many currently used assembly processes, the laser-based structuring method described herein can enable more accurate positioning of (angled) membrane wall structures across a substrate. The (angled) membrane wall structures can be accurately placed relative to existing reference points and / or additionally manufactured alignment marks on the substrate. This alignment feature can be used to fabricate stacked microstructures. The membrane wall structures can be angled toward a common focal point.

[0048] According to an embodiment of the present invention, the imaging component includes one or more of the following:

[0049] X-ray or gamma-ray filters;

[0050] Components with X-ray or gamma-ray shielding function;

[0051] X-ray or gamma-ray collimators;

[0052] anti-scatter equipment; and

[0053] X-ray or gamma-ray grating.

[0054] According to an embodiment of the present invention, the imaging component includes: the microstructure in the form of an anti-scatter device, and an X-ray detector, wherein the diaphragm wall structure of the anti-scatter device is aligned with and overlaps with the dead zone area between multiple detection elements of the X-ray detector.

[0055] This will be discussed below and in particular with regard to Figure 4 and Figure 5 The example shown is used to explain.

[0056] According to a fourth aspect of the present invention, there is provided a system for manufacturing a microstructure for selectively transmitting electromagnetic radiation using the method according to the first aspect of the present invention. The system may include:

[0057] Optical laser systems;

[0058] Etching system;

[0059] material deposition systems; and

[0060] A control system comprising one or more controllers, wherein the control system is configured to:

[0061] controlling the optical laser system to irradiate one or more regions of the substrate according to the predefined geometry of the microstructure with a first laser radiation to cause structural modification of the material in the one or more irradiated regions such that, upon subjecting the substrate to etching, the etching occurs at a higher rate at the one or more irradiated regions than at non-irradiated regions;

[0062] controlling the etching system to perform the etching to form a plurality of first openings having the predefined geometry of the microstructure in the substrate;

[0063] controlling the material deposition system to fill the first opening with at least one radiation opaque material having a desired radiation attenuation spectrum to form a radiation absorbing membrane wall structure of the microstructure;

[0064] controlling the optical laser system to irradiate one or more unirradiated areas according to the predefined geometry of the microstructure with a second laser radiation, and controlling the etching system to perform etching to form a plurality of second openings between the plurality of first openings, and

[0065] The material deposition system is controlled to not fill the second opening with any radiation opaque material, whereby the second opening is radiation transparent.

[0066] This will be discussed below and in particular with regard to Figure 6 The example shown is used to explain.

[0067] According to another aspect, there is provided a computer program comprising instructions for causing a system according to the fourth aspect to perform the steps of the method according to the first aspect and any associated examples.

[0068] According to another aspect, a computer readable medium having a computer program stored thereon is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which:

[0070] Figure 1 A flow chart describing a method for fabricating a microstructure for selectively transmitting electromagnetic radiation is illustrated.

[0071] Figure 2 An example of a manufacturing process is illustrated.

[0072] Figure 3 An example of a microstructure is illustrated.

[0073] Figure 4 Further examples of microstructures are illustrated.

[0074] Figure 5 An example of an imaging component is illustrated.

[0075] Figure 6 An example of a system for fabricating a microstructure for selectively transmitting electromagnetic radiation is illustrated.

[0076] It should be noted that the drawings are purely diagrammatic and not drawn to scale. In the drawings, elements corresponding to elements already described may have the same reference numerals. Regardless of whether or not indicated as non-limiting, examples, embodiments, or optional features should not be construed as limiting the claimed invention. DETAILED DESCRIPTION

[0077] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. However, the present invention can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. It is intended that these embodiments be provided to make this disclosure more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art. Those of ordinary skill in the art will recognize that the following description of the embodiments of the present invention is illustrative and is not intended to be limiting in any way. Other embodiments of the present invention will readily occur to those skilled in the art having the benefit of this disclosure. Identical reference numerals refer to identical elements throughout.

[0078] Although the following detailed description contains many details for the purpose of illustration, those skilled in the art will appreciate that many variations and modifications of the following details are also within the scope of the present invention. Therefore, the following embodiments of the present invention are set forth without losing the generality of the claimed invention and without imposing limitations on the claimed invention.

[0079] Figure 1A flow chart describing a method 100 for fabricating a microstructure for selectively transmitting electromagnetic radiation is shown. The microstructure can be suitable for use in high aspect ratio microstructured imaging components in X-ray (e.g., X-ray, CBCT, CT) and gamma ray (e.g., SPECT, PET) imaging, such as X-ray anti-scatter grids, absorption gratings, collimators, bow-tie filters, and energy filters. Figure 2 Describe the following steps.

[0080] In step 110 (i.e., step a)), first laser radiation 12 is irradiated to one or more regions (e.g., of the substrate 14 according to a predefined geometry of the microstructure) to cause structural modification of the material in the irradiated region or regions such that subsequent etching (in a preferred embodiment, wet chemical etching) occurs at a higher rate at the irradiated region or regions than at non-irradiated regions.

[0081] The substrate can be made of a material that is transparent or at least partially transparent to the first laser radiation. For example, glass (e.g., fused silica), polymers, dielectrics, or crystals can be used as transparent substrate materials, since the laser beam can be focused anywhere inside the material and energy can be deposited anywhere in the volume.

[0082] Due to the nonlinear nature of ultrafast laser-matter interactions, relatively low laser energy is locally absorbed whenever the laser spot is focused. The nonlinear absorption of laser energy enables the use of moderate average laser powers, but huge instantaneous powers are reached locally during laser exposure. It is even possible to manufacture features that are smaller than the wavelength of the laser itself (e.g., 1030 nm). As an example, the first laser radiation can be generated by a focused pulsed femtosecond laser. The "fly-print" process using femtosecond laser micromachining technology as a subtractive 3D printing technology is able to create narrow deep channels in glass with very high trench aspect ratios (TAR>100) (which are comparable to or higher than trench aspect ratios obtained using competing processes such as reactive ion etching (RIE)).

[0083] Energy deposition causes structural modifications in the material so that subsequent wet chemical etching occurs at a much higher rate at the exposed area(s) than at the non-exposed area(s). This locally enhanced sensitivity to wet chemical etching (etch selectivity) depends on various laser parameters (e.g., pulse duration, pulse energy, and repetition rate).

[0084] Examples of predefined geometries for microstructures include, inter alia, one-dimensional (1D) designs, two-dimensional (2D) designs (e.g., rectangular or hexagonal pixels), and custom grid designs (e.g., 1D, 2 ... 1 / 2D). The predefined geometry of the microstructures may include information such as height, wall thickness, aspect ratio, pixel shape, pixel pitch, etc. across the substrate.

[0085] In step 120 (ie, step b)), a wet chemical etch is performed to form a plurality of first openings 16 having a predefined geometry of the microstructure in the substrate 14 .

[0086] like Figure 2 As shown, the laser exposure can be controlled in such a way that the first opening 16 does not extend completely to the other side of the substrate 14. A thin solid layer of the substrate remains as a supporting base substrate for the complete system of the first opening 16.

[0087] In some examples, the optical laser system that generates the first laser radiation can be designed and programmed to write a specified structure (e.g., an array) of first openings 16 characterized by a very small, continuous increase in groove angle from the center toward the periphery of substrate 14. The optical laser system can also account for differences in refractive index at the air-glass interface and the increasing optical path length of first openings 16 toward the periphery of substrate 14. Figure 2 An example of an angled first opening is shown.

[0088] In step 130 (ie, step c)), the plurality of first openings 16 are filled with at least one material 18 having a desired radiation attenuation spectrum to form a microstructured membrane wall structure.

[0089] Materials with a desired radiation attenuation spectrum include, in particular, radio-opaque or partially radio-opaque materials. When using microstructures for various radiation energies, whether a material can be considered radio-opaque or effectively radio-opaque depends on the application and the structure dimensions (e.g., the thickness of the radiation-absorbing walls). In mammography applications, X-ray energies of approximately 20 keV are used. At these energies, copper can be considered effectively radio-opaque, meaning that microstructure walls that meet certain geometric parameters (e.g., wall thickness (e.g., 20 μm), channel height (e.g., 2 mm), etc.) absorb the desired radiation species selectively, resulting in a significant improvement in radiation detection quality parameters. Quality parameters can include the ratio of scattered radiation to primary radiation (SPR), the signal-to-noise ratio (SNR), etc. For CT applications in the 80 keV range, for example, molybdenum (Mo) or other refractory materials (e.g., tungsten (W)) can be considered effectively radio-opaque, but other materials (e.g., copper, aluminum, or tin) can also be effectively radio-opaque if the structure is manufactured with appropriate thicknesses.

[0090] At least one material of interest in X-ray imaging may include a material with a high Z value. This is particularly attractive if absorption through a thin layer of material (e.g., an anti-scatter mesh wall) is significantly higher than that of the imaged object and allows for strong beam absorption of X-ray radiation having a typical energy spectrum used in medical imaging. Examples of materials with a high Z value may include one or more of: tungsten, molybdenum, lead, bismuth, silver, gold, tantalum, tin, and low melting temperature solders (e.g., Bi58Sn42, etc.).

[0091] A variety of techniques can be used to fill the plurality of first openings 16 with at least one material 18. One method involves depositing a suitable conductive layer within the first openings 16 by atomic layer deposition, followed by conformal gold electroplating. Another method involves depositing an absorbent fill in the form of small tungsten particles into the first openings. After filling, a thin capping layer can be deposited on the substrate to prevent material loss from the trenches during subsequent processing.

[0092] exist Figure 2 In the example shown, the first opening 16 is filled with a single material. However, it will be appreciated that in some embodiments, multiple first openings can be filled with at least two materials having different radiation attenuation spectra. High aspect ratio material structures can not only adjust the spatial intensity of the incident X-ray beam, but also adjust its spatial energy by using different X-ray absorbing materials in the diaphragm wall. For example, a dedicated energy filter can be implemented by filling the trench with two materials having significantly different X-ray attenuation spectra (e.g., gold / tin, molybdenum / tungsten, copper / aluminum).

[0093] Figure 1 Also shown is step 140 (i.e., step d)), in which a second laser radiation is irradiated onto one or more unirradiated areas according to a predefined geometry of the microstructure, and wet chemical etching is performed to form a plurality of second openings 20 between the plurality of first openings 16. The first laser radiation and the second laser radiation may represent different sequences of laser exposure. This step may be used, for example, to increase the transmission of primary X-rays through the ASG.

[0094] Similarly, the laser exposure can be controlled in such a way that the second opening 20 does not extend completely to the other side of the substrate 14. A thin solid layer of substrate remains as a supporting base substrate for the complete system of the second opening 16.

[0095] exist Figure 2 In the example shown, both the first opening 16 and the second opening are at the top of the substrate 14. In some other examples (not shown), the first opening 16 can be at the top of the substrate and the second opening 20 at the bottom of the substrate 14. Such an inverted design can be manufactured by inverting the substrate in an optical laser system or by performing laser exposure from the opposite side.

[0096] It will be appreciated that the above operations can be performed in any suitable order (e.g., serially, simultaneously, or a combination thereof). In some examples, step d) can be performed after step c). In some examples, the first opening and the second opening can be created in the same step. Thus, the process would be as follows: a) → a combination of b) and d) → c). The claims should be interpreted to cover any order of method steps that makes sense.

[0097] Figure 3 An example of a microstructure 10 that can be obtained by the method described herein is shown. In the illustrated example, the microstructure 10 can be a focusing ASG or grating, wherein each X-ray absorbing diaphragm wall is accurately directed toward the focal spot of the X-ray source in order to maximize the transmission of primary X-rays toward the X-ray detector. As an example, the microstructure 10 can have a diameter of 20×20 cm. 2 Up to 50×50cm 2 The dimensions (d) are in the range between , the pixel pitch (p) is in the range between 3 μm and 1000 μm, the groove height (h) is in the range between 0.1 mm and 30 mm, the groove thickness (t) is in the range between 3 μm and 50 μm, and the focal length (f) is in the range between 50 cm and 400 cm.

[0098] In some cases, an X-ray imaging system (e.g., standard CT, curved CBCT, etc.) may not require a flat ASG or grating, but rather a curved ASG or grating. In this case, microfabrication of the desired membrane wall structure can still occur on a thin, flat substrate, which is then slightly bent in one or two dimensions (e.g., using a mold at elevated temperature) to meet the desired curvature. The curved substrate can be maintained in its original curved shape by securing it in a pre-shaped metal frame.

[0099] Compared to most currently used ASG assembly processes, the laser-based structuring method described herein can enable more localization of membrane wall structures (e.g., Figure 3 Angled diaphragm wall structures are shown. These diaphragm wall structures can be accurately placed relative to existing reference points and / or additionally fabricated alignment marks on the substrate.

[0100] In some examples, alignment features can be used to create multi-layer microstructured components having stacked microstructures. Figure 4 A schematic diagram of a fabrication process based on two microstructures 10 (eg, Figure 410a and 10b). In the illustrated example, the membrane walls of microstructure 10b are aligned with the membrane walls of microstructure 10a to create a focused ASG and grating, wherein the grooves are angled toward a common focal spot in the X-ray source. Figure 4 A two-layer microstructured component is shown by way of example in , but it will be appreciated that a multi-layer microstructured component can be created based on three or more stacked microstructures 10 .

[0101] In some examples, the alignment features can be used to integrate microstructure 10 with other devices to create new functionality. Figure 5 An example of an imaging component 40 is shown, which is an integration of a microstructure 10 and an X-ray detector 30. In the illustrated example, the microstructure 10 is an ASG that is directly coupled on top of the X-ray detector 30 to create an enhanced fill factor of the pixel area inside the X-ray detector 30. The X-ray detector 30 of the illustrated example includes an X-ray sensor 32 and a CsI scintillator 34. The X-ray sensor 32 includes an array of photodiodes 36 that can be connected to data lines (not shown) on a thin glass or foil substrate via TFT switches. The CsI scintillator 34 is exposed to X-rays. In this case, X-ray sensitivity can be enhanced because the diaphragm walls of the ASG are fully aligned and overlap with the dead zone areas between active pixels. Similarly, anti-scatter devices can be intelligently integrated in multi-layer detectors.

[0102] Although not shown, further examples of the imaging component including the microstructure include, among others, an X-ray or gamma-ray filter, a component having an X-ray or gamma-ray shielding function, an X-ray or gamma-ray collimator, and an X-ray or gamma-ray grating.

[0103] The method described herein can improve the performance of ASGs. For example, it can realize 2D ASGs with improved anti-scattering performance. The method can also enable robust ASG manufacturing processes, for example, for robust manufacturing of large-area ASGs or other microstructures. Furthermore, the method can enable lead-free manufacturing of microstructures for selective transmission of electromagnetic radiation.

[0104] Figure 6 An example of a system 200 for fabricating a microstructure for selectively transmitting electromagnetic radiation is illustrated. The system 200 includes an optical laser system 210, a chemical etching system 220, a material deposition system 230, and a control system 240.

[0105] The control system 240 may include one or more controllers. The term "controller" is generally used to describe various devices related to the operation of a streaming probe device, system or method. The controller can be implemented in a variety of ways (e.g., using dedicated hardware) to perform the various functions discussed herein. The controller can be implemented with or without a processor, and can also be implemented as a combination of dedicated hardware that performs some functions and a processor (e.g., one or more programmed microprocessors and associated circuits) that performs other functions. Examples of controller components that can be used in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs) and field programmable gate arrays (FPGAs). These and other aspects of the present invention will become apparent from the embodiments described below, and these and other aspects of the present invention will be explained with reference to the embodiments described below.

[0106] The control system 240 is configured to control the optical laser system 210 to irradiate one or more regions of the substrate according to a predefined geometry of the microstructure with the first laser radiation to cause structural modification of the material in the irradiated one or more regions, so that wet chemical etching occurs at a higher rate at the irradiated one or more regions than at non-irradiated regions.

[0107] Control system 240 is configured to control chemical etching system 220 to perform wet chemical etching to form a plurality of first openings in the substrate having a predefined microstructure geometry. One method involves depositing a suitable conductive layer within the first openings via atomic layer deposition, followed by conformal gold electroplating. Another method involves depositing an absorber fill in the form of small tungsten particles into the first openings. Following filling, a thin capping layer can be deposited on the substrate to prevent material loss from the trenches during subsequent processing.

[0108] The control system 240 is configured to control the material deposition system 230 to fill the plurality of first openings with at least one material having a desired radiation attenuation spectrum to form a microstructured membrane wall structure.

[0109] The control system 240 is configured to control the optical laser system 210 to irradiate one or more unirradiated areas according to a predefined geometry of the microstructure with the second laser radiation, and control the chemical etching system 220 to perform wet chemical etching to form a plurality of second openings between the plurality of first openings. The second openings are not filled with any radiation-opaque material, so that the second openings remain radiation transparent.

[0110] In a further exemplary embodiment of the present invention, a computer program is provided, characterized in that it is adapted to execute the method steps of the method according to one of the preceding embodiments on a suitable system.

[0111] Thus, the computer program may be stored on a computer unit, which may also be part of an embodiment of the present invention. The computer unit may be adapted to perform or cause the steps of the method to be performed. Furthermore, the computer unit may be adapted to operate components of the apparatus described above. The computer unit may be adapted to operate automatically and / or execute user commands. The computer program may be loaded into a working memory of a data processor. Thus, the data processor may be equipped to perform the method of the present invention.

[0112] This exemplary embodiment of the invention covers both a computer program that right from the beginning uses the invention and a computer program that by means of an up-date turns an existing program into a program that uses the invention.

[0113] The computer program may be able to provide all necessary steps to implement the flow of the exemplary embodiments of the method as described above.

[0114] According to a further exemplary embodiment of the present invention, a computer-readable medium such as a CD-ROM is proposed, wherein the computer-readable medium has stored thereon the computer program which has been described in the preceding sections.

[0115] The computer program may be stored and / or distributed on a suitable medium, such as an optical storage medium or solid-state medium provided together with or as part of other hardware, but may alternatively be distributed in other forms, such as via the Internet or other wired or wireless telecommunications systems.

[0116] However, the computer program may also be presented over a network like the World Wide Web and can be downloaded into the working memory of a data processor from such a network.

[0117] According to a further exemplary embodiment of the present invention, a medium for making a computer program available for downloading is provided, the computer program being arranged to perform a method according to one of the aforementioned embodiments of the present invention.

[0118] It should be noted that embodiments of the present invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method claims, while other embodiments are described with reference to apparatus claims. However, a person skilled in the art will understand from the above and following descriptions that, unless otherwise stated, any combination of features relating to different subject matters, in addition to any combination of features belonging to one type of subject matter, is also considered to be disclosed with this application. However, all features can be combined to provide synergistic effects that are greater than the sum of the features.

[0119] Although the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary rather than restrictive. The present invention is not limited to the disclosed embodiments. Other variations of the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention from a study of the drawings, the disclosure, and the appended claims.

[0120] In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may perform the functions of several items recited in the claims. Measures recited in mutually different dependent claims may be advantageously combined. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A method (100) for producing a microstructure for selectively transmitting electromagnetic radiation, the method comprising the following steps: a) irradiating (110) one or more regions of a substrate (14) according to a predefined geometry of the microstructure with a first laser radiation (12) to induce a structural modification of the material in the irradiated one or more regions such that, upon subjecting the substrate to etching, the etching occurs at a higher rate at the irradiated one or more regions than at non-irradiated regions; b) performing (120) said etching to form a plurality of first openings (16) having said predefined geometry of said microstructure in said substrate; c) filling (130) the first opening (16) with at least one radiation opaque material (18) having a desired radiation attenuation spectrum to form a radiation absorbing membrane wall structure of the microstructure; as well as d) irradiating (140) one or more non-irradiated areas according to the predefined geometry of the microstructure with a second laser radiation, and performing etching to form a plurality of second openings (20) between the plurality of first openings (16), wherein the second openings (20) are not filled with any radiation-opaque material, whereby the second openings are radiation-transparent.

2. The method according to claim 1, in, The ratio of the depth to the width of one or more of the first openings (16) is greater than or equal to 10, optionally greater than or equal to 100.

3. The method according to any one of the preceding claims, in, The substrate (14) comprises glass material or plastic material.

4. The method according to any one of the preceding claims, in, At least one of the first laser radiation and the second laser radiation is generated by a pulsed femtosecond laser.

5. The method according to any one of the preceding claims, further comprising: The substrate (14) is bent in one or two dimensions to shape the substrate according to a desired curvature.

6. The method according to any one of the preceding claims, in, The first openings (16) are angled towards a common focal point.

7. The method according to any one of the preceding claims, in, In step c), the first opening (16) is filled with at least two materials having different radiation attenuation spectra.

8. The method according to any one of the preceding claims, in, The electromagnetic radiation includes at least one of gamma radiation or X-ray radiation.

9. A microstructure (10) for selective transmission of electromagnetic radiation obtainable by a method according to any one of the preceding claims, wherein The microstructure comprises a radiation absorbing membrane wall structure formed by a plurality of first openings (16) filled with at least one radiation opaque material (18), and wherein the microstructure comprises a plurality of second openings (20) between the plurality of first openings (16), wherein the second openings are not filled with any radiation opaque material, whereby the second openings are radiation transparent.

10. An imaging component (40) comprising the microstructure (10) according to claim 9.

11. The imaging component according to claim 10, in, The imaging component (40) includes a plurality of stacked microstructures.

12. The imaging component according to claim 10 or claim 11, in, The imaging component includes one or more of the following: X-ray or gamma-ray filters; Components with X-ray or gamma-ray shielding function; X-ray or gamma-ray collimators; Anti-scatter equipment; as well as X-ray or gamma-ray grating.

13. The imaging component according to claim 9 or claim 10, in, The imaging component comprises the microstructure in the form of an anti-scatter device, and an X-ray detector, wherein a membrane wall structure of the anti-scatter device is aligned with and overlaps a dead zone region between a plurality of detection elements of the X-ray detector.

14. A system (200) for manufacturing a microstructure for selectively transmitting electromagnetic radiation, the system being configured to perform the method according to any one of claims 1 to 8.

15. The system according to claim 14, comprising: Optical laser system (210); Etching system (220); a material deposition system (230); as well as A control system (240) comprising one or more controllers, wherein the control system is configured to: controlling the optical laser system to irradiate one or more regions of the substrate according to the predefined geometry of the microstructure with a first laser radiation to cause structural modification of the material in the one or more irradiated regions such that, upon subjecting the substrate to etching, the etching occurs at a higher rate at the one or more irradiated regions than at non-irradiated regions; controlling the etching system to perform the etching to form a plurality of first openings having the predefined geometry of the microstructure in the substrate; controlling the material deposition system to fill the first opening with at least one radiation opaque material having a desired radiation attenuation spectrum to form a radiation absorbing membrane wall structure of the microstructure; controlling the optical laser system to irradiate one or more unirradiated areas according to the predefined geometry of the microstructure with a second laser radiation, and controlling the etching system to perform etching to form a plurality of second openings between the plurality of first openings; and The material deposition system is controlled to not fill the second opening with any radiation opaque material, whereby the second opening is radiation transparent.

16. A computer program for controlling a system according to claim 14 or 15, said computer program, when executed by said system, causing said system to perform the steps of the method according to any one of claims 1 to 8.

17. A computer readable medium having stored thereon the computer program according to claim 16.

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