WO2020133533A1

WO2020133533A1 - X-ray absorption grating manufacturing method and x-ray absorption grating

Info

Publication number: WO2020133533A1
Application number: PCT/CN2018/125862
Authority: WO
Inventors: 李冀; 雷耀虎; 黄建衡; 刘鑫
Original assignee: 深圳大学
Priority date: 2018-12-29
Filing date: 2018-12-29
Publication date: 2020-07-02

Abstract

Disclosed are an X-ray absorption grating manufacturing method and an X-ray absorption grating. The manufacturing method comprises the following steps: manufacturing grating grooves (2a) or grating holes (2b) on a substrate (1) to form a grating groove array or a grating hole array; washing the substrate (1) with an organic solvent, water and a surfactant; adding metal nanoparticles (3) into a volatile solvent and the surfactant to prepare a suspension; under vacuum, filling a grating microstructure with the metal nanoparticle suspension, and the metal nanoparticles (3) settling to fill up the grating grooves (2a) or the grating holes (2b); carrying out detection, and if the filling is not uniform or the metal nanoparticles (3) are not distributed in the grating microstructure, continuing the filling; and cleaning the metal nanoparticles (3) on the surface of the substrate. The absorption grating comprises the substrate (1), the grating groove array or the grating hole array is arranged on the substrate (1), and the grating grooves (2a) or the grating holes (2b) are filled with the metal nanoparticles (3). The performance of the absorption grating is not that different from that of a grating made of a molten metal material, the manufacturing method is simple, an entry barrier is low, the cost is low, and the method is convenient to operate and realize in a common laboratory.

Description

X-ray absorption grating manufacturing method and X-ray absorption grating

Technical field

The invention relates to an X-ray absorption grating, in particular to an X-ray absorption grating manufacturing method.

Background technique

Absorption grating is an indispensable key device in X-ray grating differential phase contrast imaging technology. In this technology, it can be divided into source grating and analysis grating. In 2006, F. Pfeiffer et al. introduced the Lau effect into the X-ray phase contrast imaging technology. The source grating was used to modulate the incoherent X-rays emitted by the ordinary X-ray tube into partial coherence (within a grating period) to satisfy phase contrast imaging. At the same time as the requirement of coherence, X-ray flux is fully utilized. On the other hand, in order to distinguish the shear amount of the phase grating self-imaging fringes caused by the object, an analysis grating is usually placed at the self-imaging position to sample the phase information.

Generally speaking, the period of the analysis grating is small, the aspect ratio is large, and the production is very difficult. At present, LIGA (Lithography, Electroplating, and Molding) is still the mainstream technology for making absorption gratings, which can produce large-area, high-aspect-ratio analysis gratings. But its technical barriers are high and cannot be achieved in ordinary laboratories. Subsequently, the technology of applying micro-casting technology and nano-imprint technology to the production of gratings appeared. However, the micro-casting technology needs to go through a high-temperature process in the process of modifying the surface of the grating microstructure, and in the metal filling process, A special filling furnace is required, with a certain breakage rate. Although nanoimprint technology can obtain small-period analysis gratings, the production area is very limited.

technical problem

Generally, the analysis grating has a small period and a large aspect ratio, which makes it difficult to produce. At present, LIGA (Lithography, Electroplating, and Molding) is still the mainstream technology for making absorption gratings, which can produce large-area, high-aspect-ratio analysis gratings. But its technical barriers are high and cannot be achieved in ordinary laboratories. Subsequently, the technology of applying micro-casting technology and nano-imprint technology to the production of gratings appeared. However, the micro-casting technology needs to go through a high-temperature process in the process of modifying the surface of the grating microstructure, and in the metal filling process, A special filling furnace is required, with a certain breakage rate. Although nanoimprint technology can obtain small-period analysis gratings, the production area is very limited.

Technical solution

The technical problem to be solved by the present invention is to provide an X-ray absorption grating manufacturing method with simple manufacturing method, low threshold, and low cost, which is convenient for operation and implementation in ordinary laboratories in view of the defects of the prior art.

The technical problem to be further solved by the present invention is to provide an X-ray absorption grating which is equivalent to a grating filled with melt or electroplated metal, but low in cost, and easy to operate and realize in an ordinary laboratory.

The technical solutions adopted by the present invention to solve its technical problems are:

An X-ray absorption grating manufacturing method includes the following steps:

A. Fabrication of grating microstructure: making grating grooves or grating holes on the substrate according to the grating pattern, the grating grooves or grating holes form the grating groove array or grating hole array;

B. Cleaning and drying: Use organic solvents, water and surfactant to clean the grating microstructure, and then dry;

C. Configure metal nanoparticle suspension: select metal nanoparticles, add a volatile solvent, and add a surfactant. After dispersion, prepare a uniformly dispersed metal nanoparticle suspension; where volatile solvent: the volume of the surfactant The ratio is (200:1)-(20:1), the metal nanoparticles use X-ray strong absorption metal; the particle size of the metal nanoparticles is less than half of the groove width or half of the aperture;

D. Pre-filling and sedimentation: under vacuum, the metal nanoparticle suspension is filled into the grating grooves or grating holes of the grating microstructure, and the metal nanoparticles settle to fill the grating grooves or grating holes of the grating microstructure;

E. Repeated filling and settling: detection, if the filling is uneven or the grating microstructure is not covered with metal nanoparticles, continue filling until the metal nanoparticles fill the grating groove or grating hole of the grating microstructure;

F. Post-treatment: cleaning the metal nanoparticles on the surface of the substrate to obtain an X-ray absorption grating.

Further, in the manufacturing method of the X-ray absorption grating, preferably in the step A, the grating pattern is a mask plate to copy the grating pattern to the surface of the substrate covered with photoresist, and the grating pattern is developed and fixed Cured on the substrate surface.

Further, in the manufacturing method of the X-ray absorption grating, preferably in step A, the substrate is selected from a silicon substrate, a germanium substrate, a plastic substrate or a diamond substrate, and deep reactive ion etching is used to etch the grating pattern along the surface of the substrate Internal etching, etching the grating groove or grating hole, the grating groove or grating hole corresponds to the grating pattern;

Alternatively, in the step A, the substrate is selected from a crystal-oriented (110) silicon substrate, and a film layer is used to cover the area that does not need to be etched, and the grating groove is etched by the etching rate of different crystal planes by KOH solution or TMAH Grating hole, the grating groove or grating hole corresponds to the grating pattern;

Alternatively, in the step A, the substrate is selected from an N-type or P-type (100) silicon substrate, a transparent conductive layer is formed on the back of the silicon substrate, an electric field is applied on both sides of the silicon substrate, and the silicon substrate The etching is performed to etch the grating groove or the grating hole, and the grating groove or the grating hole corresponds to the grating pattern.

Further, in the manufacturing method of the X-ray absorption grating, preferably in step B, the surfactant is selected from OP10, CO520, polyvinyl alcohol, NMP, CTAB, DMSO, or DMF, and the cleaning is ultrasonic cleaning or Shake clean.

Further, in the method for manufacturing an X-ray absorption grating, preferably, in the step C, the surfactant is selected from OP10 (alkylphenol polyoxyethylene ether) and CO520 (alkylphenol ethoxylate). X-ray strong absorption metal is selected from bismuth, tungsten, gold or lead.

Further, in the method for manufacturing an X-ray absorption grating, preferably in step D, the vacuum degree of the vacuum is higher than 0.1 atmosphere.

Further, in the method for manufacturing an X-ray absorption grating, preferably, in the step D, the close arrangement of the metal nanoparticles refers to a metal nanoparticle with a maximum gap of less than 10 times the average particle diameter of the metal nanoparticles.

Further, in the manufacturing method of the X-ray absorption grating, preferably, in step E, the detection refers to observing the distribution of metal nanoparticles in the grating microstructure by electron microscopy; or using an optical microscope to view the substrate surface, if the substrate surface If it is not covered with metal nanoparticles, it will continue to fill. If the surface of the substrate is covered with metal nanoparticles, it will no longer be filled.

An X-ray absorption grating includes a substrate, the substrate is provided with a grating groove or a grating hole, the grating groove or the grating hole forms a grating groove array or a grating hole array, and the grating groove or the grating hole is filled with X-ray strong absorption Metal nanoparticles; in the X-ray absorption grating, it is preferred that the X-ray absorption grating is a one-dimensional structure or a two-dimensional structure, and an anti-lodging strip provided in the vertical direction of the grating groove or the grating hole of the one-dimensional structure band.

Further, in the X-ray absorption grating, it is preferable that the grating period is from 0.5 μm to 50 μm, and the ratio of the width of the grating hole or the diameter of the grating hole to the width of the grating sidewall is 5:1-0.2:1.

Beneficial effect

The manufacturing method of the X-ray absorption grating of the invention is simple, the threshold is low, the cost is low, and it is convenient to operate and realize in an ordinary laboratory. Taking the nano metal particles that strongly absorb X-rays as the absorbing substance to obtain the grating microstructure as the substrate, the present invention makes the metal nano particles into a suspension, which can disperse the metal nano particles to avoid the formation of clumps between particles. Large-diameter particles, which hinder smooth entry into the grating grooves or grating holes inside the grating microstructure, maintain the dispersion characteristics of the nanoparticles, which is very beneficial for filling. Moreover, considering the wettability of the surfactant and the grating microstructure surface, the adhesion between the suspension surface and the grating microstructure surface is relatively increased, and under a negative pressure, the suspension is spread on the substrate surface, Including into the grating groove or grating hole of the grating microstructure, the suspension then carries the metal nanoparticles to the bottom of the grating groove or grating hole of the grating microstructure, because there is air in the grating hole or grating groove, and the metal nanoparticles overcome the surface tension It is very difficult to reach the grating hole or the grating groove. The present invention solves the problem of difficulty in filling metal particles directly.

The invention can densely fill metal nanoparticles inside the grating microstructure, avoiding the high-temperature process of micro-casting in the prior art, improving the yield, and can realize the production of absorption grating on the grating microstructure of large area.

The X-ray absorption grating of the present invention densely arranges metal nanoparticles in the microstructure of the grating. Although the absorption of X-rays is slightly weaker than that of the bulk structure (formed by molten metal) of the same substance, it can still form a sufficient absorption contrast. Therefore, compared with the prior art, metal nanoparticle-filled X-ray absorption gratings have unique advantages in the low-cost production of X-ray large-area absorption gratings.

BRIEF DESCRIPTION

The present invention will be further described below with reference to the drawings and embodiments. In the drawings:

FIG. 1 is a side SEM photograph of an absorption grating filled with a tungsten nanoparticle with a period of 42 μm and a depth of 150 μm in Example 1-1 of the present invention;

Figure 2 is a SEM photograph of bismuth metal filled on a silicon substrate with a period of 42 microns and a depth of 150 microns using micro-casting technology;

FIG. 3 is a contrast diagram of the contrast between the tungsten nanopowder of Example 1-1 of the present invention and the absorption grating filled with molten bismuth using micro-casting technology;

4 is a side SEM photograph of an absorption grating with a period of 5.6 microns and a depth of 50 microns in Example 1-2 of the present invention;

5 is a side SEM photograph of an absorption grating with a period of 24 μm and a depth of 130 μm according to Examples 1-3 of the present invention;

6 is a side SEM photograph of an absorption grating with a period of 24 μm and a depth of 130 μm according to Examples 1-4 of the present invention;

7 is a SEM photograph of tungsten nanoparticles filled in the grating microstructure of Examples 1-4 of the present invention;

8 is a schematic structural view of an unfilled X-ray absorption grating according to Embodiment 2 of the present invention;

9 is a schematic diagram of the structure of the filled X-ray absorption grating of Example 2 of the present invention;

10 is a schematic structural view of the X-ray absorption grating according to Embodiment 2 of the present invention;

11 is a schematic structural diagram of another implementation manner of an X-ray absorption grating according to Example 2 of the present invention.

Best Mode of the Invention

In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the drawings.

Embodiment 1. A method for manufacturing an X-ray absorption grating, including the following steps:

A. Fabrication of grating microstructure: making grating grooves or grating holes on the substrate according to grating graphics;

The grating pattern is to copy the grating pattern to the surface of the substrate covered with photoresist by using a reticle, and then to solidify the grating pattern on the surface of the substrate through development and fixing. The copying and curing of the raster pattern can be carried out by using the existing conventional technology, which will not be repeated here. The raster graphics can be designed according to actual needs, and can be a one-dimensional structure or a two-dimensional structure. The one-dimensional structure can use stripes, and the two-dimensional structure can be a criss-cross strip, or a four-sided enclosing structure with criss-cross arrangement The unit composition can also be a combination of a strip and a four-sided enclosed structural unit. The four-sided enclosing structural unit may be a curved structure connected end to end, such as a circle, an ellipse, etc., or a polygon, such as a triangle, a quadrangle, a hexagon, etc., preferably a circle and an ellipse.

There are several technical solutions for making grating groove or grating hole structure:

The first is: the substrate is selected from a silicon substrate, a germanium substrate, a plastic substrate or a diamond substrate, and deep reactive ion etching is used to etch inward along the grating pattern on the surface of the substrate to etch a grating groove or a grating hole, the grating The slot or grating hole corresponds to the grating pattern. Deep reactive ion etching (DRIE) is a technique to achieve anisotropic etching of substrates. In a plasma environment, ions bombard bare substrates under the action of an electric field. For substrates, SF ₆ is generally used to form The vertical sidewall structure of the grating groove or grating hole needs to be covered with a passivation layer on the surface of the sidewall of the grating groove or grating hole after etching for a period of time (usually a few seconds) to prevent the sidewall from being excessively corroded. Then continue to etch and reciprocate. After several cycles, a microstructure of grating groove or grating hole with a certain aspect ratio is formed. The aspect ratio refers to the ratio of depth to width (diameter). The specific parameters of deep reactive ion etching (DRIE) can be selected according to the size and physical characteristics of the specific etching object, which will not be repeated here.

The second is: when the substrate is selected from the crystal (110) silicon substrate, the area that does not need to be etched is covered with a film layer, and the grating groove or the grating hole is etched by the etching rate of different crystal planes by KOH solution or TMAH. The grating groove or grating hole corresponds to the grating pattern. The anisotropic etching of the silicon substrate is an important technology of silicon micromachining, which is mainly realized by the difference of the etching rate of each crystal plane of silicon by the etching solution. Cover the desired mask on the surface of (110) silicon and place it in KOH or TMAH with a concentration of 10-50%, so that the downward etching rate is tens or even several hundred times. After a period of time, the grating groove or grating hole microstructure with a certain aspect ratio can be obtained. The specific parameter selection of the anisotropic etching of the silicon substrate can be selected according to the size and physical characteristics of the specific etched object, which will not be repeated here.

The third type is: when the substrate is an N-type or P-type (100) crystal silicon substrate, a transparent conductive layer is coated on the back surface, an electric field is applied on both sides of the substrate, and the substrate is subjected to photo-assisted electrochemical etching. Select the substrate with crystal orientation (100), and cover the mask with one side of the substrate, and the other side with the aluminum electrode. The side with the mask first faces the KOH solution. The tip of the inverted pyramid needs to be etched, and then the The corrosive agent is replaced by an aqueous solution of HF, under the assistance of a certain light, under the guidance of the tip to the cavity, a certain voltage is applied, and the corrosion can be started downward. After a period of corrosion, the grating groove or grating hole can be etched, and the grating groove or grating hole corresponds to the grating pattern. Photo-assisted electrochemical etching is a prior art, and its specific parameter selection can be selected according to the size and physical characteristics of the specific etching object, which will not be repeated here.

According to the grating pattern, the strips correspond to the grating grooves formed after etching, and the circular, elliptical or square holes correspond to the grating holes formed after etching. The grating microstructure may also be a combination of grating grooves and grating holes. The present invention needs to etch a grating groove and a grating hole with a certain aspect ratio, and generally requires an aspect ratio <200, preferably an aspect ratio <100, and most preferably an aspect ratio <50. The present invention is suitable for gratings with various aspect ratios, such as absorption gratings with an aspect ratio <3, absorption gratings with a high aspect ratio >3, and absorption gratings with an ultra-high aspect ratio with an aspect ratio >50.

B. Cleaning and drying: Use organic solvents, water, and surfactant to clean the grating microstructure, and then dry; the surfactant can be selected in this step, as long as it can infiltrate the substrate surface, and dissolve and adsorb , Emulsification, solubilization and other surfactants to achieve cleaning purposes are applicable to the present invention. Preferably OP10, CO520, polyvinyl alcohol, NMP, CTAB, DMSO or DMF, the cleaning is ultrasonic cleaning or shaking cleaning. The organic solvent is preferably a volatile organic solvent, and can be selected from: low-carbon chain alkanes, olefins, alcohols, esters, ethers or ketones, for example: methanol, ethanol, acetone, ethyl acetate, tetrachloromethane, petroleum ether, chloroform, ether, etc. .

Specific examples: use organic solvent acetone to clean under ultrasound for 15 minutes, then use pure water to clean for 15 minutes, and finally use a volatile solvent and surfactant OP10 or a mixed solution of volatile solvent and surfactant CO520 to perform ultrasonic cleaning for 15 minutes , Use an oven to dry the substrate.

C. Configure metal nanoparticle suspension: select metal nanoparticles, add a volatile solvent, and add a surfactant. After dispersion, prepare a uniformly dispersed metal nanoparticle suspension; where volatile solvent: the volume of the surfactant The ratio is (200:1)-(20:1), the metal nanoparticles use X-ray strong absorption metal; the particle size of the metal nanoparticles is less than half of the groove width or half of the pore diameter; the volatile organic solvent described in this step can Options: Low-carbon chain alkanes, alkenes, alcohols, esters, ethers, ketones, such as methanol, ethanol, acetone, ethyl acetate, tetrachloromethane, petroleum ether, chloroform, ether, etc. A variety of surfactants can be selected in this step, as long as they can produce a wetting effect on the surface of the substrate and reduce the surface tension.

D. Filling and settling: Under vacuum, the metal nanoparticle suspension is filled into the grating grooves or grating holes of the grating microstructure, and the metal nanoparticles are allowed to settle to fill the grating grooves or grating holes of the grating microstructure;

Specifically: put the cleaned substrate in a suitable vessel, put it into a vacuum furnace together, and start to evacuate, the vacuum degree is higher than 0.1 atm. After a period of time, the configured suspension was added to the vessel without passing the grating microstructure surface. In this way, under the action of negative pressure and capillary force, the suspension quickly enters the interior of the grating microstructure and expels the gas. After the suspension enters the inside of the grating microstructure, stop the vacuum, deflate the vacuum furnace, then take out the vessel and put it into the ultrasonic cleaning machine. After a period of time, the nanoparticles will settle uniformly and finally be closely arranged inside the grating microstructure. . The close arrangement of the metal nanoparticles means that the maximum value of the gap between the metal nanoparticles is less than 10 times the average particle size.

For a grating with a small area, the nanoparticles can also be settled without the aid of an ultrasonic cleaner. After being taken out of the vacuum furnace, the nanoparticles in the suspension are allowed to settle freely and eventually fill the grating microstructure. For gratings with a relatively small period (such as a 5.6-micron grating structure), after filling in a vacuum state, it is necessary to press external force such as centrifugal force to press the metal nanoparticles into the grating microstructure.

E. Repeated filling and sedimentation: detection, if the filling is uneven or the grating microstructure is not covered with metal nanoparticles, continue to fill until the metal nanoparticles fill the grating groove or grating hole of the grating microstructure; testing refers to electron microscope sampling observation particles The distribution in the grating microstructure; or use an optical microscope to view the substrate surface. If the substrate surface is not covered with metal nanoparticles, then continue to fill, if the substrate surface is covered with metal nanoparticles, then no longer fill.

F. Post-treatment: cleaning the metal nanoparticles on the surface of the substrate. After the filling is completed, the surface of the substrate is covered with metal nanoparticle powder, which is quickly cleaned off with low-power ultrasound.

The following is a detailed description through specific embodiments:

Embodiment 1-1, a method for manufacturing an X-ray absorption grating, including the following steps:

A. Microstructure of grating: select 5 inch silicon substrate, first copy the grating pattern on the mask to the silicon substrate covered with photoresist. The grating pattern is a stripe array with a period of 42 microns and a duty cycle of 1 /4, the grating pattern is cured on the silicon substrate through development and fixing. The substrate in this embodiment is a silicon substrate, and it can also be directly replaced with a germanium substrate, a diamond substrate, or a plastic substrate, without affecting the experimental results.

Using the DRIE (Deep Reactive Ion Etching) technique, the surface of the silicon substrate was etched inwards to produce a grating groove structure with a depth of 150 μm and an aspect ratio of 3.57.

B. Cleaning and drying: use acetone to clean the silicon substrate under ultrasound for 15 minutes, then use pure water for ultrasonic cleaning for 15 minutes, and finally use ethanol and surfactant OP10 or a mixed solution of ethanol and surfactant CO520 for ultrasonic cleaning for 15 minutes. Use an oven to dry the silicon substrate.

C. Configuration of metal nanoparticle suspension: Considering cost and safety, tungsten nanoparticles with an average particle size of 50nm can be selected, ethanol is added, and surfactant OP10 is added. With the aid of 750W ultrasound, the nanoparticles are dispersed by ultrasound for 7 minutes Tungsten particles. After dispersion, a uniformly dispersed metal tungsten nanoparticle suspension is prepared; wherein the volume ratio of ethanol: surfactant is 50:1;

D. Pre-filling and settling: Put the cleaned silicon substrate into the vessel and put it into the vacuum furnace together to start evacuation. The vacuum degree is 0.2 atm. After 30 minutes, add the completed suspension to the In this vessel, the surface of the silicon substrate is covered. After the suspension enters the grating microstructure, stop the vacuum, deflate the vacuum furnace, and then take out the vessel and put it in the ultrasonic cleaning machine, ultrasonic for 8 minutes, so that the nanoparticles settle down evenly, and finally closely arranged in the grating microstructure internal.

E. Repeated filling and sedimentation: Observation of the distribution of metal nanoparticles in the grating microstructure by electron microscopy. It was found that the grating microstructure was not covered with tungsten nanoparticles. Prepare the same suspension and place the pre-filled substrate in vacuum In the environment, the suspension does not cross the surface of the substrate. Under vacuum or atmospheric environment, after 8 hours of static settlement or ultrasonic settlement, a densely packed substrate can be obtained;

F. Post-treatment: cleaning the tungsten nanoparticles on the substrate surface. After filling, if the surface of the substrate is covered with a layer of tungsten nanoparticle powder, use 300W power ultrasound for 5 seconds to remove excess tungsten metal nanoparticles remaining on the surface. Finally, the absorption grating shown in Fig. 1 is obtained.

It can be seen from Fig. 1: using an absorption grating filled with tungsten nanoparticles, the base period of the absorption grating is 42 microns, the duty cycle is 1/4, and the depth is 150 microns. It can be seen that the tungsten nanoparticles are filled in the grating grooves of this scale Dense.

Compare the grating of Example 1-1 with the absorption grating filled with molten bismuth used in the conventional micro-casting technique.

Comparative example: the same silicon-based micrograting structure is filled with molten bismuth to obtain the absorption grating shown in FIG. 2. It can be seen from FIG. 2: using the same silicon substrate as in Example 1-1, using micro-casting technology to fill the bismuth into the grating groove, the gray part in the figure is bismuth, the darker part is silicon, because it is bismuth The bulk is denser than tungsten nanoparticles.

Tested by X-ray projection imaging method, the focal spot size of the micro-focal spot source is 7 μm, the X-ray flat panel detector is placed at a distance of 1 m from the micro-focal spot source, and the grating is placed at the X-ray exit of the micro-focal spot source, that is, through the distance Enlarge the raster. The high voltage of the microfocus spot source is set to 40kV, the current is set to 80μA, and the exposure time is set to 3s. The absorption effect of the absorption grating made of the two metal materials shown in Fig. 1 and Fig. 2 on X-rays is compared. Value, plot the contrast of the respective grating, and obtain the curve of FIG. 3. It can be seen from FIG. 3 that the broken line and the solid line are respectively obtained based on the gratings shown in FIG. 1 (absorption grating filled with tungsten powder) and FIG. 2 (absorption grating filled with molten bismuth). It can be seen from the comparison that the contrast formed by the absorption gratings made by the two materials is almost the same, and it also shows the effectiveness of the method of the present invention in the production of absorption gratings.

Embodiment 1-2, a method for manufacturing an X-ray absorption grating, including the following steps:

A. Fabrication of grating microstructure: the substrate is selected from N-type 5-inch crystal orientation (100) silicon substrate, and one side of the silicon substrate is covered with a 300 nm thick Si ₃ N ₄ film, and then the photomask is used to place the mask on the mask plate. grating pattern (striped array) onto the silicon substrate covered with a photoresist, through the developing and fixing the cured grating pattern on a silicon substrate on a Si ₃ N ₄ film, etching away the exposed Si ₃ N ₄ film. The grating pattern here is a stripe array with a period of 5.6 microns and a duty cycle of 1/2. The other side of the silicon substrate is also made a grid-shaped electrode by photolithography technology, and the surface is protected and placed in a 20% KOH solution. After the inverted pyramid-shaped tip structure is etched, the light is used to assist electricity The chemical etching technique uses HF to etch the silicon substrate inwards to form a grating groove structure with a depth of 50 microns and an aspect ratio of 8.92.

B. Cleaning and drying: Use acetone to clean under ultrasound for 15 minutes, then use pure water to clean for 15 minutes, and finally use a mixed solution of ethanol and surfactant CO520 for ultrasonic cleaning for 15 minutes, and use an oven to dry the silicon substrate.

C. Configure metal nanoparticle suspension: select tungsten nanoparticles with an average particle size of 50nm, add ethanol, and add a surfactant to prepare a uniformly dispersed metal tungsten nanoparticle suspension after dispersion; of which ethanol: surface active The volume ratio of the agent is 10:1;

D. Filling and settling: Put the cleaned silicon substrate into the vessel, put it into the vacuum furnace together, and start to evacuate. The vacuum degree is 0.3 atm. After 30 minutes, add the configured suspension to the In the vessel, cover the surface of the silicon substrate. After the suspension enters the grating microstructure, the vacuum is stopped and the vacuum furnace is vented. After this operation, the gas in the tank can be removed, so that the grating tank is completely occupied by the suspension. Then remove the vessel and place it in a centrifuge, rotating at 200 rpm to help the tungsten nanoparticles enter the bottom of the grating groove.

E. Repeated centrifugal sedimentation: Once filling and centrifugal sedimentation are difficult to fill, the centrifugal filling step needs to be repeated. For inspection, use an optical microscope to view the surface of the substrate. If the surface of the silicon substrate is not covered with metal nanoparticles, repeat step D to continue filling until the metal nanoparticles fill the grating groove or grating hole of the grating microstructure;

F. Post-treatment: cleaning the bismuth nanoparticles on the surface of the silicon substrate. After the filling is completed, if the surface of the silicon substrate is covered with a layer of tungsten nanoparticle powder, use 300W ultrasonic power for 5 seconds to remove excess tungsten nanoparticles remaining on the surface. Finally, an absorption grating with a period of 5.6 microns is obtained.

 It can be seen from Figure 4: The period of the absorption grating is 5.6 microns, the duty cycle is 0.5, 2.8 microns, and the depth is 50 microns. From the SEM photograph, it can be seen directly that the particles of tungsten (the gray particles in the figure) have been filled to The bottom of the groove of the silicon-based grating is basically densely filled, and in places where the filling is insufficient, the gap is also less than 10 times the average particle size of the metal tungsten nanoparticles, which can be used as an absorption grating.

Embodiment 1-3, a method for manufacturing an X-ray absorption grating, including the following steps:

A. Microstructure of grating: N-type 5-inch (100) crystal-oriented silicon substrate is selected. The grating pattern on the mask plate is first copied to the silicon substrate covered with photoresist. The grating pattern (circular shape) is developed and fixed. Array) cured on a silicon substrate.

B. Cleaning and drying: use acetone to clean under ultrasound for 15 minutes, then use pure water to clean for 15 minutes, and finally use ethanol and surfactant OP10 or a mixed solution of ethanol and surfactant CO520 to perform ultrasonic cleaning for 15 minutes, use oven to dry Dry silicon substrate.

C. Configuration of metal nanoparticle suspension: Considering the cost and safety, bismuth nanoparticles with an average particle size of 50nm can be selected, ethanol and surfactant are added, and evenly dispersed metal bismuth nanoparticle suspension is prepared after dispersion Liquid; wherein the volume ratio of ethanol: surfactant is 30:1;

D. Filling and settling: Put the cleaned silicon substrate into the vessel, put it into the vacuum furnace together, and start to evacuate, the vacuum degree is 0.25 atm. After a period of time, the configured suspension was added to the vessel to cover the surface of the silicon substrate. After the suspension enters the grating microstructure, stop the vacuum, deflate the vacuum furnace, and then take out the vessel and put it into the ultrasonic cleaning machine. After ultrasonication for a period of time, the bismuth nanoparticles will settle uniformly and finally be closely arranged in the grating microstructure. internal.

E. Repeated filling and sedimentation: Observe the distribution of particles in the grating microstructure by electron microscopy. The filling of the upper part of the grating groove is uneven. Repeat step D to continue filling until the metal nanoparticles fill the grating groove or grating hole of the grating microstructure;

F. Post-treatment: cleaning the bismuth nanoparticles on the surface of the substrate. After the filling is completed, the substrate surface is covered with a layer of bismuth nanoparticle powder, which is quickly cleaned off with low-power ultrasound, and finally a grating as shown in FIG. 5 is obtained.

 It can be seen from Fig. 5: the period of the absorption grating is 24 microns, the duty ratio is 1/3, the depth is 130 microns, and the aspect ratio is 5.4. Since the groove width of the absorption grating is much larger than the particle size, a dense filling of bismuth particles is formed, and the entire groove is substantially filled.

Example 1-4, A. Grating microstructure: N-type 5-inch (100) crystal-oriented silicon substrate is selected, and the grating pattern (strip array) on the mask plate is first copied onto the silicon substrate covered with photoresist , The grating pattern is cured on the silicon substrate through development and fixing.

C. Configuration of metal nanoparticle suspension: Considering cost and safety, tungsten nanoparticles with an average particle size of 50 nm can be selected, ethanol is added, and surfactant is added. After dispersion, a uniformly dispersed metal nanoparticle suspension is prepared. ; Where the volume ratio of ethanol: surfactant is 100:1;

D. Filling and settling: Put the cleaned silicon substrate into the vessel, put it into the vacuum furnace together, and start to evacuate. The vacuum degree is 0.35 atm. After a period of time, the configured suspension was added to the vessel to cover the surface of the silicon substrate. After the suspension enters the inside of the grating microstructure, stop the vacuum, deflate the vacuum furnace, then take out the vessel and put it into the ultrasonic cleaning machine. After a period of time, the nanoparticles will settle uniformly and finally be closely arranged inside the grating microstructure. .

E. Repeated filling and sedimentation: Observe the distribution of particles in the grating microstructure by electron microscopy. The grating microstructure is not covered with tungsten nanoparticles. Repeat step D to continue filling until the metal nanoparticles fill the grating groove of the grating microstructure or Grating hole

F. Post-treatment: cleaning the tungsten nanoparticles on the substrate surface. After the filling is completed, the surface of the substrate is covered with tungsten nanoparticle powder, which is quickly cleaned off with low-power ultrasound, and finally an absorption grating as shown in FIG. 6 is obtained.

It can be seen from Fig. 6 that the absorption grating filled with tungsten nanoparticles has the same substrate as shown in Fig. 5, with a 24 μm duty cycle of 1/3 and a depth of 130 μm. The tungsten nanopowder is densely packed .

FIG. 7 is a more microscopic SEM image of FIG. 6, from which it can be seen that the uniformity of filling and the density of the filled particles.

Example 1-5. The tungsten powder and bismuth powder in the above examples can be directly replaced with gold powder or lead powder. Other steps and experimental conditions remain unchanged, and can also be used for the production of X-ray absorption gratings, and the obtained absorption gratings The contrast ratio of the absorption grating obtained by melt filling the existing micro-casting technology is comparable.

Embodiment 2, as shown in FIGS. 8-11, an X-ray absorption grating includes a substrate 1, the substrate 1 is provided with a grating groove 2a or a grating hole 2b, and the grating groove 2a or the grating hole 2b forms a grating groove array or In the grating hole array, the part of the groove width or aperture removed in one period is the grating side wall 5, and the grating groove 2a or the grating hole 2b is filled with nano-particles 3 of X-ray strongly absorbing metal.

The substrate 1 is selected from a silicon substrate, a germanium substrate, a plastic substrate or a diamond substrate. The above substrate 1 can be used in the present invention. According to different needs, substrates 1 of different materials are selected.

The substrate 1 is an etched grating groove 2a or a grating hole 2b, preferably having an aspect ratio <100, and most preferably having an aspect ratio <50. For the specific etching method, see the content of Example 1.

The X-ray strongly absorbing metal is selected from bismuth, tungsten, gold or lead, and the particle size of the metal nanoparticles 3 is less than half of the groove width of the grating groove 2a or half the aperture diameter of the grating hole 2b. Preferably, the close arrangement of the metal nanoparticles 3 fills the grating grooves 2a or the grating holes 2b, and the close arrangement refers to the average particle diameter of the metal nanoparticles 3 with the maximum gap between the metal nanoparticles 3 being less than 10 times.

The ratio of the width of the grating groove 2a or the diameter of the grating hole 2b to the width of the grating side wall 5 is 5:1-0.2:1 According to different design sizes and parameters of the grating, corresponding to different ratios, any value within this range is applicable to the present invention .

As shown in Figure 8-10, it is a one-dimensional grating microstructure, which is to arrange a plurality of grating grooves 2a in sequence, the spacing between the grating grooves 2a is determined according to the grating design, and a one-dimensional grating microstructure is to arrange a plurality of rows of grating grooves in sequence 2a, the grating grooves 2a are arranged to form an array, and the array arrangement is a rectangular array. The grating period from 0.5 μm to 50 μm is suitable for the present invention. As shown in FIG. 10, the anti-lodging strip 4 provided in the vertical direction of the one-dimensional grating groove 2a to reinforce the structure.

In addition to the above-mentioned grating groove 2a structure, the present invention may also be a grating hole 2b structure as shown in FIG. The grating holes 2b are arranged to form an array, and the array is arranged in a rectangular array.

The two-dimensional grating microstructure may be grating grooves 2a arranged in a crisscross pattern, grating holes 2b arranged in a crisscross pattern, or a combination of grating grooves 2a or grating holes 2b.

Claims

An X-ray absorption grating manufacturing method, characterized in that it includes the following steps:

A. Fabrication of grating microstructures: grating grooves or grating holes are made on the substrate according to the grating pattern, and the grating grooves or grating holes are arranged to form a grating groove array or grating hole array;

B. Cleaning and drying: Use organic solvents, water and surfactant to clean the grating microstructure, and then dry;

C. Configure metal nanoparticle suspension: select metal nanoparticles, add a volatile solvent, and add a surfactant. After dispersion, prepare a uniformly dispersed metal nanoparticle suspension; where volatile solvent: the volume of the surfactant The ratio is (200:1)-(20:1), the metal nanoparticles use X-ray strong absorption metal; the particle size of the metal nanoparticles is less than half of the groove width or half of the aperture;

D. Pre-filling and sedimentation: under vacuum, the metal nanoparticle suspension is filled into the grating grooves or grating holes of the grating microstructure, and the metal nanoparticles settle to fill the grating grooves or grating holes of the grating microstructure;

E. Repeated filling and settling: detection, if the filling is uneven or the grating microstructure is not covered with metal nanoparticles, continue filling until the metal nanoparticles fill the grating groove or grating hole of the grating microstructure;

F. Post-treatment: cleaning the metal nanoparticles on the surface of the substrate to obtain an X-ray absorption grating.
The method for manufacturing an X-ray absorption grating according to claim 1, wherein in the step A, the grating pattern is a reticle to copy the grating pattern to the surface of the substrate covered with photoresist, which is developed and fixed The grating pattern is cured on the surface of the substrate.
The method for manufacturing an X-ray absorption grating according to claim 1, characterized in that in step A, the substrate is selected from a silicon substrate, a germanium substrate, a plastic substrate or a diamond substrate, and deep reactive ion etching is used along the surface of the substrate The grating pattern is etched inwards, and the grating groove or the grating hole is etched, and the grating groove or the grating hole corresponds to the grating pattern;

Alternatively, in the step A, the substrate is selected from the crystal orientation (110) silicon base, covered with a film layer in the area that does not need to be etched, and the grating groove or the etching rate of the different crystal planes is etched by the KOH solution or TMAH Grating hole, the grating groove or grating hole corresponds to the grating pattern;

Alternatively, in the step A, the substrate is selected from an N-type or P-type (100) silicon substrate, a transparent conductive layer is formed on the back of the silicon substrate, an electric field is applied on both sides of the silicon substrate, and the silicon substrate The etching is performed to etch the grating groove or the grating hole, and the grating groove or the grating hole corresponds to the grating pattern.
The method for manufacturing an X-ray absorption grating according to claim 1, wherein in step B, the surfactant is selected from OP10, CO520, polyvinyl alcohol, NMP, CTAB, DMSO, or DMF, and the cleaning is Ultrasonic cleaning or shaking cleaning.
The method for manufacturing an X-ray absorption grating according to claim 1, wherein in step C, the surfactant is selected from OP10 and CO520, and the X-ray strong absorption metal is selected from bismuth, tungsten, gold or lead.
The method for manufacturing an X-ray absorption grating according to claim 1, wherein in step D, the vacuum degree of the vacuum is higher than 0.1 atm.
The method for manufacturing an X-ray absorption grating according to claim 1, wherein in step D, the close arrangement of the metal nanoparticles means that the maximum value of the gap between the metal nanoparticles is less than 10 times the average value of the metal nanoparticles Particle size.
The method for manufacturing an X-ray absorption grating according to claim 1, characterized in that, in the step E, detecting means observing the distribution of metal nanoparticles in the grating microstructure by electron microscopy; or using an optical microscope to view the surface of the substrate, If the surface of the substrate is not covered with metal nanoparticles, the filling is continued, and if the surface of the substrate is covered with metal nanoparticles, it is no longer filled.
An X-ray absorption grating includes a substrate, characterized in that the substrate is provided with grating grooves or grating holes, the grating grooves or grating holes are arranged to form a grating groove array or grating hole array, and the grating grooves or grating holes are filled with X-rays strongly absorb metal nanoparticles.
The X-ray absorption grating according to claim 9, wherein the grating period is from 0.5 μm to 50 μm, and the ratio of the width of the grating groove or the diameter of the grating hole to the width of the grating sidewall is 5:1-0.2:1 .