JP7066739B2 - Talbot X-ray microscope - Google Patents

Description

Mutual reference to related applications This patent application is filed on April 15, 2017, under the title of "TALBOT X-RAY MICROSCOPE", US Provisional Patent Application No. 62 / 485, 916. "X-RAY METHOD FOR MEASUREMENT, CHARACTERIZATION, AND ANALYSIS OF PERIODIC STRUCTURES" filed on May 15, 2015, claiming priority interests. This is a partial continuation application of US Patent Application No. 14 / 712,917 entitled. US Patent Application No. 14 / 712,917 is the US Patent Application No. 14 / entitled "X-RAY INTERFEROMETRIC IMAGING SYSTEM" filed on April 29, 2015. This is a partial continuation application of No. 700,137. US Patent Application No. 14 / 700,137 is the US Patent Application No. 14 / entitled "X-RAY INTERFEROMETRIC IMAGING SYSTEM" filed on October 29, 2014. This is a partial continuation application for Nos. 527 and 523 (currently extinguished). US Patent Application No. 14 / 527,523 is the US Provisional Patent Application No. 1 entitled "X-ray Phase Contrast Imaging System" filed on October 31, 2013. No. 61 / 898,019, entitled "An X-ray Source Consisting of an Array of Fine Sub-Sources" filed on November 7, 2013. US Provisional Patent Application No. 61 / 901,361, and US Provisional Patent Application No. entitled "Two Dimensional Phase Contrast Imaging Amplifier" filed on April 17, 2014. Claiming the interests of No. 61 / 981,098, all of these disclosures are incorporated herein by reference in their entirety.

In addition, the present application is U.S. Provisional Patent Application No. 62 / 429,587 and entitled "METHOD FOR X-RAY MICROSCOPY" filed on December 2, 2016. US provisional patent application number 62/429,760 entitled "X-RAY MEASUREMENT TECHNIQUES USING MULTIPLE MICRO-BEAMS" filed on December 3, 2016. Claiming the interests of the issue, both of which are incorporated herein by reference in their entirety.

Background a. Fields of Invention The art relates to interferometer systems that use X-rays, especially interferometer measurements that illuminate an object using a periodic microbeam system to determine the various structural and chemical properties of this object. Regarding characterization and analysis systems.

b. Description of Prior Art Prior art X-ray microscopes are generally limited by the resolution of X-ray optics (eg, zone plates) and / or the resolution of the detector pixel size. Some commercially available X-ray microscopy systems have a resolution of less than 100 nm, but such systems have a very limited field of view, and high-resolution X-ray microscopy with a large field of view has a resolution greater than 1 micron. It is difficult to generate an image in a small state.

Traditionally, the prior art Talbot system has been used for low resolution imaging. What is needed is a microscope system that utilizes Talbot fringes for high-resolution imaging with improved throughput.

Overview The technique outlined here is an X-ray microscopy technique that uses an array of microbeams with a microscale or nanoscale beam intensity profile to selectively irradiate a microscale or nanoscale region of an object. Includes a system for. The array detector is positioned so that each pixel of this detector detects only the X-rays corresponding to a single microbeam, thereby illuminating certain limited microscale or nanoscale regions. Can identify the signal generated by the X-ray detector. This enables highly efficient and large microscopic microscopy using a large pixel detector without compromising spatial resolution.

In embodiments, a microscale or nanoscale beam may be provided by producing a set of Talbot fringes, the set of Talbot fringes corresponding to a beam with an antinode of the interference pattern. Create a set of fine X-ray microbeams. In some embodiments, the array of microbeams or nanobeams may be provided by an array of conventional X-ray sources and X-ray imaging elements (eg, X-ray lenses).

In embodiments, both the detector and the object are placed within the same waist or "depth of focus" range of a set of Talbot-building fringes (antinodes). In some embodiments, the detector is installed in any subsequent set of antinodes downstream (a fraction of the Talbot distance apart). In some embodiments, the object is positioned on a mount that allows translation in the x and y directions perpendicular to the propagation direction of the X-ray beam and is "scanned" transmission on a microscope scale. Images can be constructed. In some embodiments, the object is positioned on a mount that allows rotation about an axis perpendicular to the direction of propagation of the X-ray beam to collect microscope-scale data in a laminography or tomography image. Can be used for reconstruction.

An additional masking layer may be inserted in the beam path to block a selected number of microbeams, which allows a detector with a larger pixel size to be used with the remaining microbeams. Further, by using the masking layer, the detector with improved detection efficiency can be used in the remaining microbeam. Such a masking layer may be placed in front of the object under investigation, may be placed between the object and the detector, or may be designed as part of the detector structure itself.

It is a figure which shows the conventional example of the Talbot interference fringe pattern for a 1: 1 duty cycle absorption lattice. It is a figure which shows the detail from the pattern of FIG. 1A which shows an anti-node as a "depth of focus" range. It is a figure which shows the conventional example of the divergence Talbot interference fringe pattern for a 1: 1 duty cycle π / 2 phase shift lattice. It is a figure which shows the conventional example of the divergence Talbot interference fringe pattern for a 1: 1 duty cycle π phase shift lattice. It is a figure which shows the conventional example of the divergence Talbot interference fringe pattern for a 1: 3 duty cycle π phase shift lattice. It is a figure which shows the phase grid and self-image in various phase grid periods. It is a schematic diagram of the microscope which concerns on embodiment of this invention. It is a figure which shows the substrate which has the embedded target mask. It is a figure which shows the alternative substrate which has an embedded target mask. It is a figure which shows the system which shoots a source electron beam into a target at an oblique angle. It is a figure which shows the target which has a fine structure. It is a figure which shows the plot of the optimum thickness vs. acceleration voltage for molybdenum. FIG. 3 is a schematic diagram of a microbeam, an object and a detector according to an embodiment of FIG. 3A. FIG. 3 is a schematic cross-sectional view of the microbeam, object and detector of the embodiment of FIG. 3A. It is the schematic of the microscope which concerns on embodiment of this invention which put the mask in front of the object to be investigated. FIG. 5 is a schematic diagram of a microbeam, an object, and a detector according to an embodiment of FIG. FIG. 5 is a schematic cross-sectional view of the microbeam, object and detector of the embodiment of FIG. FIG. 3 is a schematic cross-sectional view of an embodiment of a microbeam, object and detector comprising a scintillator. FIG. 3 is a schematic cross-sectional view of an embodiment of a microbeam, object and detector comprising a scintillator and a scintillator imaging system. It is the schematic of the microscope which concerns on embodiment of this invention which put the mask in front of the object to be investigated. FIG. 5 is a schematic diagram of a microbeam, an object, and a detector according to an embodiment of FIG. FIG. 5 is a schematic cross-sectional view of the microbeam, object and detector of the embodiment of FIG. FIG. 3 is a schematic cross-sectional view of an embodiment of a microbeam, object and detector comprising a mask on the detector and scintillator. FIG. 3 is a schematic cross-sectional view of a microbeam, an object and a detector of an embodiment comprising a detector and a scintillator and a scintillator imaging system with a mask. It is a figure which shows the method of collecting the microscope data.

Detailed Description of Embodiments of the Invention This technique is for X-ray microscopy in which an array of microbeams having a microscale or nanoscale beam intensity profile is used to selectively irradiate a microscale or nanoscale region of an object. Including the system of. Each microbeam is separated from the other microbeams by a region of lower X-ray intensity that is 0.8 to 0 times the intensity of this microbeam. The array detector is positioned so that each pixel of this detector detects only the X-rays corresponding to a single microbeam, thereby illuminating certain limited microscale or nanoscale regions. Can identify the signal generated by the X-ray detector. In some examples, the object to be imaged and the detector are positioned within the same Talbot diffraction order. In this system, spatial resolution is decoupled from source size and detector pixel size.

Imaging with Talbot fringes generally analyzes the resulting pattern with a grid (often a phase shift grid) to generate the Talbot interference pattern and / or an array X-ray detector. Need to do.

FIG. 1A shows Talbot interference fringes produced by an absorption grid G with a 50/50 duty cycle and pitch p when illuminated by a plane wave. Interference fringes are generated behind the grid and reconstruct the pitch p with a 50/50 duty cycle at the Talbot distance _DT , where the Talbot distance _DT is expressed by the following equation.

In the equation, p ₁ is the period of the beam dividing lattice and λ is the X-ray wavelength.
As an X-ray irradiator, the Talbot interference pattern can generate bright antinodes with corresponding micron-scale dimensions by suitably selecting a beam-splitting grid. For X-rays with an energy of 24.8 keV and an absorption grid with a 50/50 duty cycle and 1 micron pitch, the Talbot distance is _DT = 4 cm. The x- and y-direction scales of the fringes in the figure of FIG. 1 are quite different, and these fringes may have micron scale and pitch laterally (ie, perpendicular to the propagation direction). It may have a focal depth on the scale of hundreds of microns to several centimeters.

The fringe pattern at various fractions of the Talbot distance may actually be smaller than the size of the original grid features. Therefore, these antinodes may function as multiple microbeams used to illuminate the object to achieve higher resolution.

The range (depth of focus) at which the antinode maintains its finest dimensions is related to the pitch p of the Talbot fringes and is expressed by the following equation.

For example, the waist or "depth of focus" corresponding to an X-ray antinode with a grid period of 1 micron at 20 keV is about a few centimeters.

FIG. 1B shows an enlarged portion of the antinode of FIG. 1A having a portion that can be considered to be a DOF of one of the above antinodes. In some examples, an anti-node is a portion of the beam that differs by more than 20% from the node, even if the contrast ratio between the "anti-node" and the "node" is 1.2: 1. good. The exact definition of the beam "waist" defined by the range in which the antinode changes by less than a predetermined amount (eg, the length range in which the antinode full width at half maximum change is within 5%) is for various Talbot patterns. It may be defined. It should be noted that a given interference pattern may have many fine "waist" that can be used for irradiation, and depending on the grid used, it may have dimensions even finer than the grid half pitch. .. Also, these "waist" may occur at various distances from the grid and may not be at the previously defined fractional Talbot distance.

Therefore, the pattern of Talbot fringes resembles an array of "microbeams" propagating in space. These fringes may be parallel microbeams as shown in FIG. 1 or may be acquired using a convergent or divergent X-ray beam. Further examples of Talbot interference patterns are shown in FIGS. 2A-2C.

FIG. 2A shows the intensity pattern produced by a grid 210-1-90 (shown in cross section) that introduces a π / 2 radian phase shift from a 1: 1 grid-space width ratio. FIG. 2B shows the intensity pattern produced by grid 2101-180, which introduces a π radian phase shift into a 1: 1 grid-spatial width ratio. FIG. 2C shows the intensity pattern produced by the grid 210-3-180, which introduces a π radian phase shift into a grid-space width ratio of 1: 3. The simulations of FIGS. 2A-2C assume a grid with a longy (eg, line / spatial square wave) profile and a point source with sufficient spatial coherence.

FIG. 2D shows a two-dimensional phase grid and self-image in the π and π / 2 phase grid periods. As shown in FIG. 2D, the π-period grid is checkered and produces a "mesh" self-image. A grid with a π / 2 period is also checkered, but produces a checkered self-image with inverted contrast. The X-ray microscope of the present technology can generate a microbeam by utilizing a grid having a π period, a π / 2 period, or another period.

In many embodiments, the beam split grating is a low absorption phase grating, but other predetermined or such as π / 2 or π radians, or a fraction or multiple of π or π / 2. A phase grating that results in a significant X-ray phase shift of a predetermined value. These grids may be one-dimensional or two-dimensional. In some embodiments, the object under investigation is placed downstream of the grating at the fractional Talbot distance _DN represented by the following equation.

In the equation, _pl is the period of the beam splitting lattice, _DN is the fractional Talbot distance for plane wave irradiation, λ is the average X-ray wavelength, and N is the _Talbot fractional order on which the object is placed (N). = 1, 2, 3, ...). In some examples, the object is placed downstream of the grating at a distance that is not a fractional Talbot distance, but instead the area of antinodes and nodes where the wavefront corresponds to the periodic area of analysis. It is located at a distance consisting of.

Depending on the grid parameters (eg, π phase shift grid vs. π / 2 phase shift grid), the optimum Talbot distance ( _Na ) may be selected according to the interference pattern of interest, or the one most suitable for the application. May be.

1. 1. Talbot fringes as an array of microbeams The microscopy systems and methods using it disclosed herein create a variety of microscale or nanoscale X-ray beam arrays used to illuminate an object. It may be formed using technology. As an example, an optical system is used to image an X-ray source with multiple arranged X-ray sources or an alternative transmission target with an array of microstructures within the depth of focus of the X-ray optical system. Can provide a "microbeam" corresponding to an image of the source location.

Talbot fringes, especially those formed by phase grids, are a very efficient way to direct X-rays to a valid array of microbeams. The effective lateral dimension of the Talbot antinode (beam diameter if the beam is constructed in a circle) is very small (eg, 20 nm or 300 nm) by constructing the fringes using a suitable beam splitting grid. Can be submicron). The Talbot interference pattern provides an array of individual micro or nanoprobes that can be detected and analyzed using an array detector when used to illuminate an object under investigation during transmission. Thus, the X-ray microscope system can achieve submicron (eg, 0.3 μm) spatial resolution at high throughput. If the detector is selected to have a pixel size corresponding to the pitch of the Talbot fringes and both the object and the detector are placed within the effective "depth of focus" of the Talbot fringes, each pixel will be of the "microbeam". The transmitted X-ray from one is detected.

The contrast between the intensity of multiple microbeams and the intensity of the region between the microbeams is further improved by installing an absorption grid with the same pitch as the microbeams so that the X-rays between the microbeams are attenuated. Can be made to.

By scanning an object in x-dimensional and y-dimensional, microscale or nanoscale probes can be moved and moved over the object, as seen in the co-pending US patent application and US provisional patent application above. If the range is similar to or greater than the Talbot fringe pitch, a relatively low resolution X-ray pixel array detector can be used to obtain a high resolution "map" of the transmission of the object. The "resolution" of the system is solely determined by the size of the microbeam and is independent of the detector pixel size.

An overview of such a system is shown in FIG. 3A, and more in detail in FIGS. 4A and 4B. Source 011 provides electrons 111 to target 100 to generate an X-ray beam 888, which creates an array of microbeams after passing through grid G1. This source of X-rays meets known constraints and preferably implements an array of beamlets up to submicron size. The source of X-rays may be a single point or line source, or a periodic structure source such as a conventional source paired with an absorption (one-dimensional or two-dimensional) lattice. good. Alternatively, the main outcome of the increased throughput is to separate the source size from the spatial resolution, which allows the use of sources that are high power due to their large size. One innovation in the art that enables greater X-ray power utilizes an X-ray source patterned according to the periodic pattern _A0 . Such a system is shown in FIG. 3A. In this configuration shown, the X-ray source 11 has a target 100, which is a substrate 1000 and a separate microstructure 700 of element size a arranged in a periodic 2D pattern with a period _p0 . It has a region 1001 including. When the electrons 111 are driven in, they generate X-rays 888 in a periodic pattern with period _p0 . In some examples, the target 100, which may include an X-ray generation microstructure, an X-ray blocking mask and / or other elements described herein, can implement an X-ray generator.

Each microstructure 700 in the target 100 of this structured source serves as an independent, mutually incoherent X-ray sub-source (or source location). The interference of these source points creates a set of streaks in the sample plane that are laterally offset with respect to the other source points. The pitch of the structured source and the distance between the source and G1 can be selected to ensure that these streaks overlap in the sample plane. The increase in focused flux is proportional to the number of source locations used.

In some examples, the source is well separated from the G1 grid 210-2D so that it has a coherence length greater than the G1 grid period. When the apparent width of each sub-source is S, the distance between the source and G1 is Z, and the emission wavelength is L, then L * Z / S> p1 and p1 in the equation. Is the G1 cycle.

Once the array 888-M of X-ray irradiation beams (microbeams) is formed, the object 240 under investigation is irradiated to the array 282 at the individual interaction sites. In many embodiments, the sample 248 is installed at a Talbot distance downstream of the beam splitting grid. These positions can be scanned using the position controller 245 in the x and y dimensions perpendicular to the direction of propagation of the microbeam, and the X-ray irradiation beam 889 produced by the interaction of the microbeam with the object. -T can be detected by the array detector 290.

The array detector 290 is aligned so that each pixel of this detector is positioned to collect only the X-rays corresponding to a single microbeam. This is generally within the "depth of focus" of the anti-node. Paired with a detector that has a pixel pitch that matches the pitch of the microbeams, each pixel is aligned to detect X-rays only from the interaction of a single microbeam at a given position on the object. By using a plurality of microbeams, it is possible to create an equivalent of 10 ² to 10 ⁴ parallel microbeam detection systems.

The object can then be scanned at the x and y coordinates. This will generate a "map" of the properties of the object in parallel, but the range of movement may simply be smaller to correspond to the pitch of the microprobe (but some between the scanned areas). Overlaps would be appropriate to provide relative calibration between the data collected for adjacent "maps"). Data at each location in the map is limited in resolution only by the lateral dimensions of the Talbot stripes, so high resolution images are collected using cheaper and / or more efficient detectors with larger pixels. can do.

The "maps" generated by each pixel are then digitally stitched together to reduce the corresponding data acquisition time by an amount related to the number of microbeams (eg, up to a ^quarter ). You may generate a large "macro map" of the properties of the object.

Limited object angle adjustments may also be added to the motion protocol to achieve some tomographic analysis, which is the interaction of X-rays with the object and the corresponding detector pixels both in multiples. It may be done as long as it stays within the entire depth of focus of the microbeam.

1.1 Alternative X-ray Source In some examples, the X-ray source target may include a microstructure mask. FIG. 3B shows a substrate 1000 with an embedded microstructure mask. The substrate 1000 of FIG. 3B includes a thin film 1002, a first substrate portion 1004, and a second substrate portion 1006. Substrate portions 1004 and 1005 may be made of a low atomic element material such as diamond, Be, sapphire. The electron beam emitted into the thin film 1002 generates X-rays in the thin film. The generated X-rays are blocked by the microstructure 700 to create an array of effective X-ray sub-sources. The microstructure 700 may be placed on the substrate portion 1004 and covered or encapsulated by the substrate portion 1006. Alternatively, they may be formed by embedding the microstructure within a single substrate portion, as shown in Target 1000 of FIG. 3C.

Although only one pattern of microstructural elements in the target 1000 is shown in FIGS. 3A-3C, other implementations are possible and are considered to be within the scope of the present disclosure. For example, the target 1000 may include a plurality of target patterns formed by any combination of microstructure and mask, one or more of the plurality of target patterns having a plurality of depths within the substrate. obtain.

In some examples, the electron beam may enter the target at an oblique angle. FIG. 3D shows a system in which one or more electron beams 11 are launched into the target 1000 at an oblique angle such as 20 ° to 80 °. In some examples, the angle of incidence of the electron beam on the target may be about 60 °. By providing an electron beam incident at an oblique angle, a high energy X-ray beam from the target is possible and scattering on a substrate such as diamond is reduced.

FIG. 3E shows a target having a substrate 1004 (generally a low atomic material such as diamond) and a microstructure 700. In some examples of the technique, the target thickness t is optimized for a particular material to improve the contrast between the X-rays emitted to the microstructure 700 and the X-rays generated within the substrate. Can be done. In some examples, the thickness is about 2-10 μm. In some examples, the depth of the target microstructure material in the substrate may be optimized to achieve a particular acceleration voltage. FIG. 3F shows a plot of optimum thickness vs. acceleration voltage for molybdenum (Mo) microstructure. As shown, the relationship between the optimum depth (unit: micrometer) and the acceleration voltage (unit: kilovolt) is approximately linear. For example, at an energy of 60 kV, the optimum depth would be about 10 microns. Although only data for molybdenum is displayed, the optimum depth of the target microstructure for other materials may also be optimized for a particular acceleration energy.

Some microstructure targets may further include a conductive layer, a layer for improving thermal conductivity between the microstructure and the substrate, and / or a diffusion barrier.

1.3 In embodiments where the X-ray source filtering microbeam is generated by the Talbot effect, the bandwidth of the X-ray beam in the object under investigation is in the range of +/- 15% of the predetermined X-ray energy of interest. Must be inside. This is generally achieved by using a filter such as a thin metal leaf.

2. 2. Geometric Conditions Returning to FIG. 3A, the X-rays 888 are individually spatially coherent for the beam-splitting grid G1 _210-2D installed at _a distance L from the arranged X-ray sources A0. It originates from the arranged sources as an array of irradiation sub-sources that are mutually incoherent. The position of the object 240-W illuminated by the array of microbeams is located at a further distance D from the beam splitting grid G ₁ 210-2D. To ensure that each X-ray sub-source at A ₀ contributes constructively to the image formation process, the geometry of the arrangement should meet the following conditions:

When this condition is met, X- _rays from many sub-sources of A0 produce the same (overlapping) Talbot interference patterns, as various mutually incoherent sources do not interfere with each other. The Talbot pattern will be stronger. Therefore, the effect on the object 240-W is to simply increase the intensity of the microbeam (along with it, the signal-to-noise ratio) beyond the intensity that a single coherent source can provide. This configuration is called a Talbot low interferometer. It should be noted that the arranged X-ray sources can, in some embodiments, generate X-rays only from a uniform X-ray material and specific locations arranged in an array of dimensions a and period _p0 . May be provided using a masked grid and. The arranged X-ray source may also be provided by selective implantation of an X-ray generating material using a patterned electron beam.

The beam splitting grid may be an amplitude grid with 50/50 duty cycles or an amplitude grid with other duty cycles, as shown in FIG. 3A. The phase shift beam splitting grid may include a 1D or 2D periodic pattern of π or π / 2 phase shift.

To ensure that the object 240-W under investigation is illuminated by a periodic pattern of X-ray microbeams, the distance D between the grid and the object is one of the fractional Talbot distances, ie: Should correspond to.

In the equation, n is a non-zero integer. If the grid is a transmission grid, a π phase shift grid, or a π / 2 phase shift grid, the appropriate values for n may differ.

Another equation often used in the Talbot-Lago system relates the pitch p1 of the Talbot grid G1 to the size _a of the X _- ray generating elements in the arrayed sources.

Most embodiments of the present invention utilize an interferometer system that meets the conditions set forth in Equations 4-6.

In some embodiments, the object 240-W under investigation may be mounted on a position controller 245 that may be controlled to translate the object 240-W in x and y dimensions. In some embodiments, further rotation of the object to generate tomographic imaging data may also be controlled by the mounting system. In some embodiments, a 5-axis mount or goniometer may be used.

It should be noted that these embodiments shown are not drawn according to a certain ratio.

3. 3. Detector considerations As disclosed here, the detector pitch is multiple micros so that each pixel is positioned to detect only X-rays generated from the interaction of the object with a single microbeam. Matched to the pitch of the beam, crosstalk between pixels due to adjacent microbeams is minimized. It can then be seen that data acquisition and final reconstruction of the "map" of the properties of the object may continue, without further deconvolution of the individual signals from each pixel. If there is crosstalk between the microbeam and the pixels (eg due to scattering or fluorescence), further image analysis can remove some of the crosstalk if properly calibrated. You may. An energy decomposition array detector may also be used to separate the signal from transmitted, scattered and fluorescent X-rays.

This matching is most straightforwardly achieved when the detector pitch is 1: 1 matched with the pitch of the microbeams, i.e. each beam has a corresponding single pixel in the detector, and the detector is , Installed very close to objects and microbeams.

3.1 Fine detector pitch In some embodiments, a detector pitch that is an integral fraction of the pitch of the microbeam (eg, X-rays in which four pixels correspond to a single microbeam in a 2D array). Also a 2x reduction in pitch that would indicate that it is positioned to collect, or a 3x reduction in pitch that would indicate that 9 pixels are present to detect the X-rays corresponding to each microbeam). May be used. This can provide some advantages if the detected X-rays have some spatial structure, for example if the desired X-ray signal is associated with small angle scattering from an object. The particular pixel of the detector can then be aligned to detect only scattered X-rays, while the non-scattered beam may be collected by different pixels or simply blocked.

3.2 Large detector pitch In other embodiments, larger detector pixels may be used. In this case, as long as the active area (the part that converts X-rays into electronic signals) of each pixel of the detector is approximately the same size as the corresponding X-ray microbeam, a pixel size larger than the pitch of the Talbot fringes is used. You may. Therefore, the detector is cheaper, but can still generate a "high resolution" signal (because the spatial resolution is determined by the amount of interaction between the Talbot fringes and the object, not the detector pixel size. be).

One disadvantage of this technique is that only one of the four Talbot stripes is used for detection and the other stripes are wasted. Although certain Talbot fringes end up unused, scanning over the distance between detector pixel centers can still provide missing information. Further, by increasing the pixel size, it is possible to achieve even better detection efficiency for the detected microbeam.

5-12 show the use of larger pixels in some embodiments of the invention. FIG. 5 is similar to that of FIG. 3A, but outlines an embodiment of a system in which a mask is placed in front of an object 240-W to block a specific number of microbeams. As shown, three of the four microbeams are blocked and only one of the four beams is detected by the detector after illuminating the object, but in advance for a variety of applications. Any number of beams may be blocked according to a defined pattern.

6A and 6B show such embodiments in more detail and show similar figures to those of FIGS. 4A and 4B. As can be seen by comparison with FIGS. 4A and 4B, since only a certain number of microbeams are used, the pitch of the beams in the detector is substantially higher and cheaper detectors with larger pixel sizes are available. May be used.

As shown in FIGS. 3-6B, the X-ray detector is shown as a direct array detector that produces an electrical signal in response to X-ray absorption. Such an electronic sensor may directly create an electrical signal in response to X-ray absorption, for example by creating a direct electron-hole pair in amorphous selenium (a-Se). These are then converted into electronic signals using an array of thin film transistors (TFTs). Such direct flat panel detectors (FPDs) such as Shimadzu's (Kyoto, Japan) sapphire FPDs are commercially available.

In other embodiments, the detector may use a scintillator that emits visible or ultraviolet light when exposed to X-rays. The active X-ray detection region is provided by a scintillator such as, for example, thallium (CsI (Tl)) doped cesium iodide, or of a scintillator having a high Z material, eg, a masking layer of gold (Au) on top. It may be defined by providing a uniform coating to the detector.

FIG. 7 is a modification of the embodiment of FIG. 6B, but shows a modification in which the detector 290-S is used in combination with a fluorescent screen or a scintillator 280. The scintillator 280 comprises a material that emits visible and / or UV photons when X-rays are absorbed, and the detector 290-S detects those visible and / or UV photons. A typical scintillator material comprises a layer of cesium iodide (CsI), thallium-doped CsI, yttrium aluminum garnet (YAG) or gadolinium sulfoxylate (GOS).

In conventional imaging systems, high resolution images can be obtained using a scintillator-type detector that is very close to the object, but the overall thickness of the scintillator and electronic elements corresponds to this pixel for each detector pixel. It must be thin enough to collect only X-rays.

However, in the systems disclosed herein, spatial resolution is defined by the dimensions of the microbeam 888-M instead of the detector pixel size. This allows the use of larger pixels and thus thicker scintillator materials. This is because it can be seen that all the photons generated from this larger pixel are generated from a predetermined microbeam. This thicker scintillator increases the probability that a given X-ray photon will be absorbed and converted to visible light, increasing the potential signal.

Some additional X-ray photons generate secondary electrons in the scintillator material, which can excite further visible / UV emission from the scintillator material. However, since it is known that all X-ray photons in the pixel originate from a single microbeam, additional photons resulting from this excitation also end in these spatially defined X-rays. It turns out to be emanating and simply increases all detectable signals.

FIG. 8 shows a further modification of the scintillator-based system in which visible / UV light 890 from the scintillator 280 is collected by the visible / UV optical system 320 and projected onto the detector 290-SI. Visible / UV optical systems may include optical components that further magnify the image of the scintillator. When using relay optics and magnified images, the electronic detector may not be equipped with the high resolution sensor itself, for example an inexpensive commercially available CCD having 1024 x 1024 pixels, each measuring 24 μm x 24 μm square. A detector or complementary metal oxide semiconductor (CMOS) sensor array may be used.

In some embodiments with relay optics, thicker scintillators may also be used, which improves sensitivity. However, when relay optics are used, detection is limited to the field of view collected by the X-ray optics, which can be as small as a few hundred microns in some cases. Therefore, in order to collect data in a larger area, it is necessary to "join" from several shots.

9, 10A and 10B show a further embodiment in which a masking structure 297 is installed between the object 240 and the detector. In this embodiment, all available microbeams 888-M illuminate the object 240, but the masking layer 297, for example made of gold (Au), prevents three of the four beams from entering the detector 290. To. Again, the detector 290 can have larger pixels, also reducing the cost of the direct detector and improving the potential detector efficiency in embodiments that use a scintillator.

FIG. 11 is a further variant of the embodiments of FIGS. 9, 10A and 10B, but further variants in which X-ray detection is achieved using a scintillator 280 and a visible / UV detector 290-S. show.

FIG. 12 shows a further variant of the scintillator-based system in which visible / UV light 890 from the scintillator 280 is collected by the visible / UV optical system 320 and projected onto the detector 290-SI.

The scintillators shown in FIGS. 7, 8, 11 and 12 are shown to have a uniform layer of scintillator, but the scintillator material is a patterned scintillator material in which the scintillator material is placed only on a portion of the pixel. The embodiment using the above may also be used. Selective placement of the scintillator material over a portion of the detector may be used as an alternative to selecting a particular microbeam for detection using a masking layer.

A detector having an additional structure in each pixel may also be utilized. For example, a typical detector pixel is 2.5 microns x 2.5 microns (6.25 microns ² area), but if the microbeam diameter is only 1 micron, it is slightly larger than 1 micron. A detector pixel may be created that is surrounded by a "dead" zone and has a central "spot" of scintillator material positioned to correspond to the location of the microbeam. In this configuration, all X-rays from the microbeam should be detected, while the detection of scattered or diffracted X-rays that would produce a spurious signal when using the entire area of the detector pixels. Decreases.

Similarly, in some embodiments, the detector structure (such as a scintillator material) is positioned only on the outer part of the pixel, for example, to detect only small angle scattered X-rays and not directly transmitted beams. Pixels may also be used.

Similarly, the mask 297 in FIGS. 11 and 12 is shown to be offset from the scintillator layer, but in some embodiments the masking layer may be placed directly on top of the scintillator layer. Other embodiments of patterned scintillators will also be known to those of skill in the art.

3.0 Method of collecting microscope data FIG. 13 shows a method of collecting microscope data. Data acquisition may be used to form 2D "maps" or 3D tomographic images.

In step 4210, an X-ray microbeam is generated by using an X-ray source and a beam splitting grid, preferably a phase grid. In some examples, the X-ray source utilizes an X-ray target composed of microstructures embedded on or within a low mass density substrate (eg, diamond or Be). In some examples, the X-ray source comprises a thin film coated on a low mass density substrate, further comprising an embedded microstructure that acts as a "mask" to block a portion of the X-ray beam. To use. In some examples, the X-ray source is a wide area X-ray source and is used in combination with an absorption grid. In some examples, the X-ray source is a microfocus X-ray source.

A filtering method is installed between the X-ray source and the beam splitting grid (4220) to limit the bandwidth of the X-rays from the X-ray source to a certain bandwidth. In some examples, the bandwidth of the irradiated beam can be ± 15%, depending on whether a predetermined Talbot distance is used or a fractional Talbot distance is used.

By aligning the object under investigation at the Talbot distance (4230), the microbeam node (darkest intensity) and anti-node (highest intensity) regions are orthogonal to the propagation direction (“x”). It has a pitch p of 20 micrometer or less in the direction and (denoted as "y" direction). The contrast between the highest intensity region (generally the center of the microbeam) and the darkest intensity region (generally just the region just between the microbeams) is preferably at least 20%, but in some cases anti. In some cases, a 1.2: 1 or 2: 1 intensity ratio between nodes may provide sufficient contrast. In some examples, the bandwidth of the irradiation beam satisfies the following equation.

By aligning the detector within the "waist" of the microbeam (4240), each detector pixel produces a signal corresponding to a single microbeam. In the microbeam formed by the imaging system, this position may correspond to the depth of focus of the imaging system. In most cases, the center of each microbeam coincides with the center of the detector pixel because the detector pixel pitch and the microbeam are the same or similar with some scaling.

In the microbeam formed by the Talbot system, this may correspond to the position of an interference pattern that is a fraction or an integral multiple of the Talbot distance, where a self-replicating image is formed. As long as each pixel of the detector produces a signal corresponding to only a single microbeam (without crosstalk between microbeams or detector pixels), there is some flexibility in the exact positioning of the detector. be. Generally, the detector is chosen so that every microbeam has a corresponding pixel or set of pixels, but in some embodiments the detector may detect only a subset of the microbeams. .. In some examples, the detector can be selected to have a pixel pitch _pd equal to a non-zero integral multiple of the microbeam pitch p.

The X-rays transmitted by each microbeam are recorded by the detector (4250) and the corresponding electronic signals representing the X-ray intensity and energy are recorded.

If only one set of data points is required, no further data needs to be collected. However, in most embodiments, a position controller is used to move the object under investigation (4260) to build a 1D or 2D "map" of the properties of the object. This is generally done so that the object is moved several times corresponding to the FWHM of each microbeam region of highest intensity, moving in both x-dimensional and y-dimensional dimensions.

When no information beyond 2D scans in x-dimensional and / or y-dimensional is required, the system acquires stored data, in which case various images "joint" commonly known in the art. The technique can be used to synthesize a 2D intensity "map" showing large area X-ray transmission / absorption of an object.

On the other hand, when 3D information is required, the object is rotated at an angle with respect to the z-axis (this rotation may be about either x-dimensional or y-dimensional). A set of data is collected from the X-ray detector at this alternative rotation position. The system loops through these steps to collect x-ray information in a pre-programmed sequence of position and rotation until a complete set of data has been collected. At this point, the system subsequently acquires stored data, in this case using a variety of image 3D analysis techniques commonly known in the art for large area X-ray transmission / absorption of the object. Combine 3D images.

Modifications of the above method may also be implemented. For example, instead of first running a loop of data collection in X and y dimensions at a fixed rotation position and then changing the rotation settings to collect more data, mechanically with the x and y position settings fixed. An embodiment in which an object is rotated by a mechanism may also be implemented. Rotation of the object around the z-axis can also provide additional information that can be used in image tomosynthesis.

4. Limitations and Extensions The present application discloses several embodiments of the invention, including the best embodiments intended by the inventors. Although specific embodiments are shown, it will be appreciated that elements described in detail only for some embodiments may be applied to other embodiments. The details and various elements described as being in the prior art may also be applied to various embodiments of the invention. Although specific materials, designs, configurations and manufacturing steps have been described to illustrate the invention and preferred embodiments, such description is not intended to be limiting. Modifications and modifications are apparent to those skilled in the art and it is intended that the invention is limited only by the appended claims.

Claims (20)

X-ray microscope system
The X-ray irradiation beam generation system is provided, and the X-ray irradiation beam generation system is provided.
X-ray source and
The X-ray irradiation beam generation system including a beam dividing lattice generates a plurality of X-ray microbeams by the Talbot effect, and the plurality of X-ray microbeams are predetermined with a depth of focus and a propagation axis. The X-ray microscopy system further has a predetermined intensity profile perpendicular to the axis for X-ray energy.
The mount comprises a mount configured to support the object under investigation within the depth of focus, the mount being configured to move the object relative to the plurality of X-ray microbeams, and the X-ray microscope system. moreover,
The detector comprises at least one X-ray pixel array detector for detecting X-rays resulting from the interaction of the plurality of X-ray microbeams with the object, and the detector comprises a plurality of pixels within the depth of focus. , X-ray microscope system. The X-ray microscope system according to claim 1, wherein the beam dividing grid is a π phase shift grid or a π / 2 phase shift grid at the predetermined X-ray energy. The X-ray source is
Emitters for electron beams and
A transmission X-ray target comprising a plurality of individual microstructures comprising a first material having a first mass density and a second mass density lower than the first mass density. The X-ray microscope system according to claim 1, comprising a substrate comprising a second material comprising. The X-ray microscope system according to claim 3, wherein the electron beam is incident on the target at an oblique angle. The X-ray microscope system according to claim 1, wherein the X-ray source is a microfocus X-ray source or a wide area X-ray source used in combination with an absorption grid. The X-ray microscope system according to claim 1, further comprising at least one filter such that the full width at half maximum of the bandwidth of the plurality of X-ray microbeams is 30% centered on the predetermined X-ray energy. .. The X-ray microscope system according to claim 1, wherein the mount is configured to translate the object in two orthogonal directions. The X-ray microscope system of claim 7 , wherein the mount is further configured to rotate the object about a direction perpendicular to the propagation axis. The X-ray microscope system according to claim 1, wherein the detector is a CCD-based detector and is aligned so that the center of the pixel is aligned with the center of the X-ray microbeam. The X-ray microscope system according to claim 1, further comprising an analysis system configured to display and analyze an output signal from the detector. The X-ray microscope system of claim 1, further comprising a mask positioned to block a predetermined number of the X-ray microbeams. The X-ray microscope system of claim 1, further comprising a mask positioned upstream of the detector to block a predetermined number of X-ray microbeams that have passed through the object. The X-ray microscope system according to claim 1, wherein the system achieves submicron spatial resolution. The X-ray microscope system according to claim 1, wherein each pixel has an active detection area in the center of the pixel, and the active detection area occupies less than 50% of the total area of the pixel. Attenuation located upstream of the detector and positioned to absorb X-rays between the X-ray microbeams and increase the intensity ratio between the X-ray microbeams and the region between the X-ray microbeams. The X-ray microscope system according to claim 1, further comprising a lattice. A method for measuring X-ray transmission of an object,
Steps to generate an X-ray Talbot interference pattern with multiple antinodes and depth of focus,
A step of positioning the X-ray array detector having a plurality of pixels so that the plurality of pixels are within the depth of focus of the X-ray Talbot interference pattern.
A method comprising the step of positioning the object under investigation within the depth of focus so that at least some X-rays of the antinode that have passed through the object under investigation are detected by the detector. 16. The method of claim 16 , further comprising a step of preventing at least a portion of the X-rays that have passed through the object from being detected by the detector. 16. The method of claim 16 , further comprising a step of preventing at least a portion of the X-rays of the Talbot interference pattern from reaching the object. 18. The method of claim 18 , wherein the blocking step comprises a step of positioning the mask in front of the object. 19. The method of claim 19 , wherein the mask is positioned within the depth of focus.

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