The present application is related generally to x-ray windows.
Important characteristics of x-ray windows include strength; high x-ray transmissivity, particularly of low-energy x-rays; impervious to gas, visible light, and infrared light; and ease of manufacture. Another important characteristic of x-ray windows is use of materials with low atomic number in order to avoid contaminating the x-ray signal.
It has been recognized that it would be advantageous to provide x-ray windows which are strong; have high x-ray transmissivity; are impervious to gas, visible light, and infrared light; are easy of manufacture; and are made of materials with low atomic numbers. The present invention is directed to x-ray windows that satisfy these needs. Each embodiment may satisfy one, some, or all of these needs.
In one embodiment, the x-ray window can comprise a support frame encircling an aperture, support ribs extending across the aperture, and thin film spanning the aperture. A maximum thickness of the thin film can be ≤250. The thin film can include a boron hydride layer with ≥90 weight percent boron, ≥0.5 weight percent hydrogen, and a thickness of ≥30 nm and ≤200 nm.
In another embodiment, the x-ray window can comprise a support frame encircling an aperture and a thin film spanning the aperture. A maximum thickness across a width of the thin film can be ≤250 nm. The thin film can include a boron hydride layer with ≥97 weight percent boron, ≥1 weight percent hydrogen, ≤3 weight percent hydrogen, a thickness of ≥30 nm and ≤200 nm, and a density of between 2.0 and 2.2 g/cm3.
In another embodiment, the x-ray window can comprise a support frame encircling an aperture and a thin film spanning the aperture. A maximum thickness across a width of the thin film can be ≤250 nm. The thin film can include a boron layer with borophene embedded in amorphous boron. The boron layer can have a thickness of ≥30 nm and ≤200 nm.
c are schematic, cross-sectional side-views of x-ray windows 30, 40a, 40b, and 40c, similar to x-ray window 10, but further comprising an aluminum layer 32, the boron layer 12 and the aluminum layer 32 defining a thin film 31, in accordance with an embodiment of the present invention.
As used herein, the terms “on”, “located at”, and “adjacent” mean located directly on or located over with some other solid material between. The terms “located directly on”, “adjoin”, “adjoins”, and “adjoining” mean direct and immediate contact.
As used herein, the term “mm” means millimeter(s), “μm” means micrometer(s), and “nm” means nanometer(s).
As used herein, the terms “top face,” “top side,” “bottom face,” and “bottom side” refer to top and bottom sides or faces in the figures, but the device may be oriented in other directions in actual practice. The terms “top” and “bottom” are used for convenience of referring to these sides or faces.
As illustrated in
A boron layer 12 can span the aperture 15 of the support structure 11. The boron layer 12 has a bottom side 12B which can adjoin and can be hermetically sealed to the support structure 11. Alternatively, another layer of material can be located between the boron layer 12 and the support structure 11. The gaps 13 can extend to the boron layer 12. A material composition of the boron layer can be mostly boron, such as for example ≥60 weight percent, ≥80 weight percent, ≥95 weight percent, ≥96 weight percent, ≥97 weight percent, ≥98 weight percent, or ≥99 weight percent boron.
The boron layer 12 can provide needed characteristics, including strength, with a relatively small thickness. Thus, for example, the boron layer 12 can have a thickness Th12 of ≥5 nm, ≥10 nm, ≥30 nm, or ≥45 nm and ≤55 nm, ≤70 nm, ≤90 nm, ≤120 nm, ≤200 nm, ≤500 nm, or ≤1000 nm.
The boron layer 12 can include borophene. The borophene can be embedded in amorphous boron.
The boron layer 12 can include both boron and hydrogen and thus can be a boron hydride layer. Addition of hydrogen can make the boron layer 12 more amorphous, more resilient, lower density, and more transparent to x-rays. For example, the boron hydride layer can include the weight percent boron as specified above and can include ≥0.01 weight percent, ≥0.1 weight percent, ≥0.25 weight percent, ≥0.5 weight percent, ≥1 weight percent, ≥1.5 weight percent, or ≥2 weight percent hydrogen. The boron hydride layer can include ≤1.5 weight percent, ≤2 weight percent, ≤3 weight percent, or ≤4 weight percent hydrogen.
The boron hydride layer 12 can have improved performance if density is controlled within certain parameters. For example, the boron hydride layer can have density of ≥1.7 g/cm3, ≥1.8 g/cm3, ≥1.9 g/cm3, ≥2.0 g/cm3, or ≥2.05 g/cm3, and can have density of ≤2.15 g/cm3, ≤2.2 g/cm3, or ≤2.3 g/cm3. The density of the boron hydride layer can be controlled by temperature, pressure, and chemistry of deposition.
As illustrated in
Proper selection of a thickness Th22 of the boron ribs 22 can improve x-ray window 10 strength plus improve low energy x-ray transmissivity. Thus, for example, the boron ribs 22 can have a thickness Th22 of ≥5 nm, ≥10 nm, ≥30 nm, or ≥45 nm; and a thickness of ≤55 nm, ≤70 nm, ≤90 nm, or ≤120 nm. It can also be helpful for optimal x-ray window strength and x-ray transmissivity if the thickness Th22 of the boron ribs 22 is similar to the thickness Th12 of the boron layer 12. Thus for example, a percent thickness difference between the boron layer 12 and the boron ribs 22 can be ≤2.5%, ≤5%, ≤10%, ≤20%, ≤35%, or ≤50%, where the percent thickness difference equals a difference in thickness between the boron layer 12 and the boron ribs 22 divided by a thickness Th12 of the boron layer 12. In other words, percent thickness
The boron ribs 22 can have a percent boron and/or a percent hydrogen as described above in regard to the boron layer 12. The boron ribs 22 can have density as described above in regard to the boron layer 12.
For some applications, it can be important for x-ray windows to block visible and infrared light transmission, in order to avoid creating undesirable noise in sensitive instruments. For example, the x-ray windows described herein can have a transmissivity of ≤10% in one aspect, ≤3% in another aspect, or ≤2% in another aspect, for visible light at a wavelength of 550 nanometers. Regarding infrared light, the x-ray windows described herein can have a transmissivity of ≤10% in one aspect, ≤4% in another aspect, or ≤3% in another aspect, for infrared light at a wavelength of 800 nanometers.
As shown in
As illustrated in
As shown in
As shown on x-ray window 40a in
The thin film 31 can be relatively thin to avoid decreasing x-ray transmissivity. Thus for example, the thin film 31 can have a thickness Th31 of ≤80 nm, ≤90 nm, ≤100 nm, ≤150 nm, ≤200 nm, ≤250 nm, ≤500 nm, or ≤1000 nm. This thickness Th31 does not include a thickness of the support ribs 11R or the support frame 11F. This thickness Th31 can be a maximum thickness across a width W of the thin film 31. Examples of the width W of the thin film 31 include ≥1 mm, ≥3 mm, ≥5 mm, or ≥7.5 mm; and ≤50 mm or ≤100 mm.
As shown in
It can be important for x-ray windows 10, 30, 40, and 50 to be strong (e.g. capable of withstanding a differential pressure of ≥one atmosphere without rupture) and still be transmissive to x-rays, especially low-energy x-rays. This is accomplished by careful selection of materials, thicknesses, support structure, and method of manufacturing as described herein. For example, the x-ray window can have ≥20%, ≥30%, ≥40%, ≥45%, ≥50%, or ≥53% transmission of x-rays in an energy range of 50 eV to 70 eV (meaning this transmission percent in at least one location in this energy range). As another example, the x-ray window can have ≥10%, ≥20%, ≥30%, or ≥40% transmission of x-rays across the energy range of 50 eV to 70 eV.
The x-ray windows 10, 30, 40, and 50 can be relatively strong and can have a relatively small deflection distance. Thus for example, the x-ray window 10, 30, 40, or 50 can have a deflection distance of ≤400 μm, ≤300 μm, ≤200 μm, or ≤100 μm, with one atmosphere differential pressure across the x-ray window 10, 30, 40, or 50. The x-ray windows 10, 30, 40, or 50 described herein can include some or all of the properties (e.g. low deflection, high x-ray transmissivity, low visible and infrared light transmissivity) of the x-ray windows described in U.S. Pat. No. 9,502,206, which is incorporated herein by reference in its entirety.
These x-ray windows 10, 30, 40, and 50 can be relatively easy to manufacture with few and simple manufacturing steps as will be described below. These x-ray windows 10, 30, 40, and 50 can be made of materials with low atomic numbers. Thus for example, ≥30, ≥40, ≥50, or ≥60 atomic percent of materials in the thin film 31 can have an atomic number of ≤5.
A method of manufacturing an x-ray window can comprise some or all of the following steps, which can be performed in the following order. There may be additional steps not described below. These additional steps may be before, between, or after those described.
The method can comprise step 60 shown in
In one embodiment, the wafer 61 can comprise silicon, and can include ≥50, ≥70, ≥90, or ≥95 mass percent silicon. Examples of temperatures in the oven 62 during formation of the boron layer 12 include ≥50° C., ≥100° C., ≥200° C., ≥300° C., or ≥340° C., and ≤340° C., ≤380° C., ≤450° C., ≤525° C., or ≤600° C. Formation of the boron layer 12 can be plasma enhanced, in which case the temperature of the oven 62 can be relatively lower. A pressure in the oven can be relatively low, such as for example 60 pascal. Higher pressure deposition might require a higher process temperature.
Following step 60, the method can further comprise step 70 shown in
Instead of step 60, the method can comprise step 80 shown in
Following step 80, the method can further comprise step 90 shown in
This step 90 can further comprise etching the wafer 61 to form support ribs 11R extending from a bottom face 61B of the wafer 61 towards the boron layer 12. Example chemicals for etching the wafer 61 are described above in reference to step 70. The support ribs 11R can be aligned with the boron ribs 22 and can be sandwiched between the boron ribs 22 and the boron layer 12.
This etching can also result in forming a support frame 11F and/or a boron frame 22F encircling an aperture 15. The support ribs 11R can span the aperture and can be carried by the support frame 11F. The boron ribs 22 can span the aperture and can be carried by the boron frame 22F. The support ribs 11R can be aligned with the boron ribs 22 and can be sandwiched between the boron ribs 22 and the boron layer 12. The support frame 11F can be aligned with the boron frame 22F and can be sandwiched between the boron frame 22F and the boron layer 12.
As shown in
As shown in
In step 110 shown in
The aluminum layer 32 in step 100, step 110, or step 120 can have a weight percent of aluminum as described above. The aluminum layer 32 and the boron layer 12 can define a thin film 31. Examples of methods for applying the aluminum layer 32 in step 100, step 110, or step 120 include atomic layer deposition, evaporation deposition, and sputtering deposition. A thickness Th22 of the boron ribs 22, a thickness Th12 of the boron layer 12, a thickness Th32 of the aluminum layer 32, and a thickness Th31 of the thin film 31 can have values as described above. Step 100 can be combined with step 110 or step 120 to provide two aluminum layers 32, with the boron layer 12 sandwiched between the two aluminum layers 32.
This is a continuation of U.S. patent application Ser. No. 16/826,581, filed on Mar. 23, 2020, which is a continuation of U.S. patent application Ser. No. 16/208,823, filed on Dec. 4, 2018 (now U.S. Pat. No. 10,636,614), which claims priority to U.S. Provisional Patent Application No. 62/614,606, filed on Jan. 8, 2018, and 62/642,122, filed on Mar. 13, 2018, which are incorporated herein by reference.
Number | Date | Country | |
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62614606 | Jan 2018 | US | |
62642122 | Mar 2018 | US |
Number | Date | Country | |
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Parent | 16826581 | Mar 2020 | US |
Child | 17142456 | US | |
Parent | 16208823 | Dec 2018 | US |
Child | 16826581 | US |