X-ray surface analysis and measurement apparatus

Patent metadata

Field	Value
Publication number	US-9594036-B2
Application number	US-201514634834-A
Country	US
Kind code	B2
Filing date	Mar 1, 2015
Priority date	Feb 28, 2014
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

This disclosure presents systems for total reflection x-ray fluorescence measurements that have x-ray flux and x-ray flux density several orders of magnitude greater than existing x-ray technologies. These may therefore useful for applications such as trace element detection and/or for total-reflection fluorescence analysis. The higher brightness is achieved in part by using designs for x-ray targets that comprise a number of microstructures of one or more selected x-ray generating materials fabricated in close thermal contact with a substrate having high thermal conductivity. This allows for bombardment of the targets with higher electron density or higher energy electrons, which leads to greater x-ray brightness and therefore greater x-ray flux. The high brightness/high flux source may then be coupled to an x-ray reflecting optical system, which can focus the high flux x-rays to a spots that can be as small as one micron, leading to high flux density.

First claim

We claim:

1. An x-ray system for analyzing a sample, comprising:
at least one x-ray source comprising:
a vacuum chamber;
a window transparent to x-rays attached to the wall of the vacuum chamber;
and, within the vacuum chamber:
at least one electron beam emitter, and
an anode target comprising:
a substrate comprising a first selected material, and
a planar first surface, from which thickness is measured in a direction perpendicular to the first planar surface, and two orthogonal lateral dimensions are measured parallel to the first planar surface; and

a plurality of discrete structures embedded into the first planar surface of the substrate such that each of the plurality of discrete structures is in thermal contact with the substrate,
the plurality of discrete structures comprising:
one or more materials selected for its x-ray generation properties;

in which at least two of the plurality of discrete structures are arranged on a predetermined axis;
in which the predetermined axis is parallel to the first planar surface of the substrate;
in which the predetermined axis passes through the first window;
in which each of the discrete structures has a thickness of less than 20 microns, and
in which each of the plurality of discrete structures has a lateral dimension in the direction of the predetermined axis of less than 50 microns; and

a means of directing electrons emitted by the at least one electron beam emitter onto the at least two arranged discrete structures such that x-rays are generated from each of the at least two arranged discrete structures;
in which at least a portion of the generated x-rays propagating on the predetermined axis from each of the two arranged discrete structures is transmitted through the window;
and additionally comprising:
an x-ray optical system
having an optical axis aligned relative to said predetermined axis, said optical system positioned to collect diverging accumulated x-rays from said at least two arranged discrete structures in the x-ray source

and to condition and create an x-ray beam with predetermined properties;
said optical system additionally comprising a central beam stop positioned to block x-rays propagating parallel to the optical axis;
a means to direct the x-ray beam to be incident onto an area of the surface of a sample at a grazing angle less than the critical angle with the surface;
at least one detector positioned to detect the intensity of the x-rays emerging from the sample and generate electrical signals; and
a signal processor to analyze the electrical signals to obtain information about at least one of:
composition, concentration, quantity, and film thickness.

2. The x-ray system of claim 1 ,
in which said at least one detector is positioned to detect fluorescent x-rays that are radiated by the sample;
and additionally comprising:
at least one additional detector to detect x-rays reflected from the surface of the sample.

3. The x-ray system of claim 1 , in which said x-ray beam with predetermined properties has the property of being focused to a single spot with a spot size smaller than 300 microns; and in which the focused x-ray spot corresponds to a predetermined position on the surface of the sample.

4. The x-ray system of claim 1 , in which said predetermined axis and said optical axis are coincident.

5. The x-ray system of claim 1 , in which said optical system comprises a total external reflection based x-ray optic.

6. The x-ray system of claim 1 , in which said substrate comprising a first selected material has a thermal conductivity greater than 0.1 W m −1 ° C. −1 .

7. The x-ray system of claim 1 , in which the first selected material is selected from the group consisting of:
beryllium, diamond, graphite, silicon, boron nitride, silicon carbide, sapphire, and diamond-like carbon.

8. The x-ray system of claim 1 , in which the one or more materials selected for its x-ray generation properties are selected from the group consisting of:
aluminum, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, gallium, zinc, yttrium, zirconium, molybdenum, niobium, ruthenium, rhodium, palladium, silver, tin, iridium, tantalum, tungsten, indium, cesium, barium, gold, platinum, lead, and combinations and alloys thereof.

9. An x-ray measurement system, comprising:
an x-ray source, comprising:
a vacuum chamber;
a window transparent to x-rays attached to the wall of the vacuum chamber;
and, within the vacuum chamber:
at least one electron beam emitter, and
an anode target comprising:
a substrate comprising a first selected material, and
a planar first surface,
from which thickness is measured in a direction perpendicular to the first planar surface, and
two orthogonal lateral dimensions are measured parallel to the first planar surface; and

a plurality of discrete structures embedded into the first planar surface of the substrate such that each of the plurality of discrete structures is in thermal contact with the substrate,
the plurality of discrete structures comprising:
one or more materials selected for its x-ray generation properties;
in which at least two of the plurality of discrete structures are arranged on a predetermined axis;
in which the predetermined axis is parallel to the first planar surface of the substrate;
in which the predetermined axis passes through the first window;
in which each of the discrete structures has a thickness of less than 20 microns, and
in which each of the plurality of discrete structures has a lateral dimension in the direction of the predetermined axis of less than 50 microns; and
a means of directing electrons emitted by the at least one electron beam emitter onto the at least two arranged discrete structures such that x-rays are generated from each of the at least two arranged discrete structures;
in which at least a portion of the generated x-rays propagating on the predetermined axis from each of the at least two arranged discrete structures is transmitted through the window;
and additionally comprising:
an optical train having an optical axis to collect diverging x-rays generated by said at least two of the plurality of discrete structures in the anode target, and that produces an x-ray beam with predetermined beam properties;
said optical train additionally comprising a central beam stop positioned to block x-rays propagating parallel to said optical axis;
a mount to hold an object to be investigated, positioned such that the x-ray beam will be incident onto an area of the surface of the object at a grazing angle less than the critical angle with the surface;
a detector to measure x-rays emerging from the object when x-rays are incident on the object.

10. The system of claim 9 , in which said detector is positioned to detect fluorescent x-rays that are radiated by the sample;
and additionally comprising:
an additional detector to measure the intensity of the x-rays reflected from the object.

11. The system of claim 9 , in which each lateral dimension parallel to said first planar surface for each of said at least two arranged discrete structures is less than 50 microns.

12. The system of claim 9 , in which the plurality of discrete structures are arranged in a linear array along said predetermined axis; and
the optical axis of the optical train is also aligned along said predetermined axis.

13. The system of claim 9 , in which the first selected material is selected from the group consisting of:
beryllium, diamond, graphite, silicon, boron nitride, silicon carbide, sapphire, and diamond-like carbon.

14. The system of claim 9

Assignees

• Sigray Inc

Inventors

• Yun Wenbing
• Lewis Sylvia Jia Yun
• Kirz Janos

Classifications

• G01N23/085

  X-ray absorption fine structure [XAFS], e.g. extended XAFS [EXAFS] · CPC title

• G01N23/2076

  for spectrometry, i.e. using an analysing crystal, e.g. for measuring X-ray fluorescence spectrum of a sample with wavelength-dispersion, i.e. WDXFS · CPC title

• G01N23/223 Primary

  by irradiating the sample with X-rays or gamma-rays and by measuring X-ray fluorescence · CPC title

• H01J2235/086

  Target geometry · CPC title

• G21K2201/064

  having a curved surface · CPC title