JP2725971B2 - X-ray source - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray source used for a microscope or the like which enables a magnified fluoroscopic view of a microstructure.

[0002]

2. Description of the Related Art Conventionally, a conventional optical microscope is used for inspection of minute parts whose minute internal structure cannot be seen through the outside due to opaque materials, such as reinforcing belts containing steel wires, fiber sleeves, wire dies, and electronic parts. The measurement could not be used, and the shape was too small to use a shape measuring instrument or the like. For this reason, product inspection of lots was performed by cutting samples of completed parts and optically inspecting them, but it was troublesome, and because it was a destructive test, 100% inspection was impossible in principle .

It has been known for a long time that microradiography can be used for visual inspection of opaque objects, and a fluoroscopic image is enlarged by a projection method using the spread of an X-ray source having a minute focus. X-ray microscopes are used for inspection of soldering of electronic components and the like.

[0004]

However, in order to obtain a minute X-ray source, it is necessary to squeeze the electron beam accelerated to a high voltage minutely and hit the target, which disadvantageously increases the size of the electron lens. was there. Furthermore, since a small X-ray source is used, a pinhole made of a heavy metal is used so as to prevent transmission of X-rays in a direction other than a predetermined direction in order to suppress unnecessary X-ray radiation. The power required for it has increased. Accordingly, the power consumed by the target is increased, so that there is a disadvantage that the target is of a rotary type and the accompanying equipment such as its cooling system is enormous.

According to the present invention, in order to avoid an increase in the size of a device for obtaining a point X-ray source, which is a drawback of the conventional X-ray microscope, the X-ray source is a point light source from the beginning and the device is fundamentally reduced in size. It is intended to provide an X-ray source.

[0006]

In order to solve the above-mentioned problems, the present invention fills a pinhole of a spherical alumite film with metal and impinges electrons on a target surface formed by coating metal on the pinhole. It is characterized by the following.

Further, the spherical target surface is disposed on a surface of the vacuum tube opposite to the electron beam source, so as to shut off the outside air.

[0008]

By the above means, the focal point can be made very small with a small amount of power without using a pinhole, so that a small-sized X-ray microscope can be realized by using this, and inspection of invisible objects becomes convenient. As described above, the apparatus for obtaining a point X-ray source, which is a drawback of the conventional X-ray microscope, is avoided from being enlarged, the X-ray generation source is a point light source from the beginning, and the apparatus is fundamentally reduced in size. .

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1A is a structural view showing an embodiment of an X-ray source (X-ray generating tube) according to the present invention, and FIG. 1B is a partially enlarged view showing the target of FIG. 1A. It is sectional drawing. 1 (a) and 1 (b), 1 is a cathode, 2 is a tube stem, 3 is an aperture, 5 is a tube wall, 6 is a spherical target, 7 is a first DC power supply, and 8 is a second DC A power supply, 11 is a target film, 12 is an electrode, 13 is an insulating shim, 14 is a spherical porous film, and 23 is a substrate. Tube wall 5 and cathode 1
The space surrounded by the tube stem 2, the target 6, and the electrode 12 is maintained at a high vacuum like the vacuum tube. FIG. 2 schematically shows the structure of the target 6 including the porous film 14, in which 21 is an anodized alumite, 22 is a metal pillar,
Reference numeral 23 denotes a substrate, reference numeral 11 denotes a target film, pillars 22 each have a columnar shape with a diameter of several tens of nm, and an interval between the pillars 22 is several tens to several hundreds of nm.

The target 6 has a spherical shape protruding in the direction of the cathode 1, a target film 11 made of a metal film such as tungsten is formed on the vacuum side, and an anodized alumite 21 and a metal pillar 22 are formed on the opposite side. Porous membrane 14
Is formed of a thin film on which is formed. The target 6 is fixed to an electrode 12 having a hole in the target portion.

The porous film 14, which is a feature of this embodiment, is obtained by anodizing aluminum from one side, expanding the hole by etching, and attaching a metal to the hole to perform a sealing process.

The operation of this embodiment will be described with reference to FIG. 1. A high electric field of several tens of kV is applied between the cathode 1 and the electrode 12 by the first DC power supply 7, and Electrons are extracted directly from the cathode 1 into a vacuum. When viewed from the electric field extraction electrode 12 side, since the portions other than the target 6 are covered with the insulating shim 13, the electric field extraction electrode 12
More drawn-out electronic e ^- flows into the target. The electrons e ⁻ drawn from the cathode 1 flow into the target 6. At this time, since the electrons e ⁻ are accelerated at a high speed by a high electric field, the electrons e ⁻ enter the inner nucleus of the target atom, and a part of the kinetic energy is changed to the atom. Target 6 as the characteristic X-ray
Released from Since the generation wavelength and efficiency of X-rays are proportional to the acceleration voltage of the electron e ⁻ and the atomic number of the target 6, X-rays can be efficiently generated along the direction of movement of the electron beam by using the target 6 as a thin metal. .

[0014] X-rays are electrons e accelerated the target 6 ^-
And radiates almost isotropically through the target 6. In other words, the X-ray source has a size of a region where the electron e ⁻ hits. However, when penetrating through the porous film 14 on the front and back of the target film 11, the component perpendicular to the film surface of the X-ray emitted from the target film 11 passes only through the alumite 21 portion, but deviates from the normal direction of the film surface. The X-rays are absorbed because they pass through the metal pillars 22. As a result, only the X-rays in the normal direction component exit from the target 6 and the X-rays having the focal point at the center of the spherical surface are emitted in a spherical shape. That is, it can be regarded as a point light source at the focal position.

In the example shown in FIG. 1, the target 6 also serves as a partition between the inside and the outside, which need to be evacuated in order to accelerate electrons. Since there is no substance, X-rays can be efficiently extracted. Since the substrate 23 may serve as a base for performing anodization by attaching aluminum thereon and performing metal plating thereafter, processing into a spherical surface is easy, and
Any material may be used as long as it has low linear absorption, and for example, a plastic such as graphite or polyimide whose surface is metallized may be used. In the description of the present embodiment, the thin substrate 23 is used.
Although an example is shown in which anodization is used, it is of course possible to remove the layer by anodizing it to a predetermined thickness using aluminum and then etching it from the opposite side.

When the electrons are concentrated and collide with the target 6, heat is generated. However, the electrode 12 connected to the target 6 serves as a current path and also serves as a heat radiation path for generated heat. Further, in this embodiment, the focal point of the X-ray can be extremely small regardless of the size of the target 6, so that the target 6
The density of electrons colliding with the surface can be reduced, and the influence of heat generation can be avoided.

In order to obtain a microfocus X-ray source with a conventional Coolidge tube structure or the like, it is important to focus the electron beam on a small area and collide with the target 6 in order to reduce the X-ray focus. However, even if the electrode 12 is formed into a cone shape to concentrate electrons, the electron beam inevitably spreads according to the potential distribution unless an electron lens for actively converging the electron beam is used in this structure, and the electron beam spreads on the electron tube wall. And the momentum of the electron beam deviates from the linear distribution. If the tube is enlarged to avoid this, maintenance of vacuum degree and mechanical stability deteriorate. Therefore, in this embodiment, the entire X-ray generation tube is configured to be extremely small. Specifically, if the interval between the target 6 and the cathode 1 is set within several tens of μm with respect to the target target region of μm order, the electrons extracted from the cathode 1 are hit against the target 6 without extremely diffusing. By setting the size of the tube stem 2 to about several tens of times, a practically problem-free generating tube can be manufactured.

It is well known that efficient selection of X-rays can be achieved by appropriately selecting the material of the target film 11 and the material of the pillars 22. For example, to make an X-ray microscope of about 1.5 angstroms, copper may be used for the target film 11 and iron may be used for the pillar 22. To obtain a shorter X-ray source, tungsten may be used for the target film 11, Silver or the like may be used for 22.

Using the X-ray generating tube 30 composed of the X-ray source according to the above embodiment, the sample 31 is placed at a distance d1 from the focal position as shown in FIG.
Is arranged, a transmission image of the sample of (d1 + d2) / d1 times is obtained on the fluorescent plate 32. The image on the fluorescent screen 32 is
It is needless to say that an image can be taken by the D camera 33 or the like and displayed on the display / analysis device 34 to be used as a simple X-ray microscope. Reference numeral 35 denotes a control circuit for the X-ray generation tube 30, and reference numeral 36 denotes an objective lens.

As is apparent from the above description, it can be easily analogized that a simple X-ray collimator can be realized by filling the pores of anodized alumite with metal. Therefore, the spherical metal-weighted alumite film and the conventional X
It is of course within the scope of the present invention to realize a point light source by combining radiation sources. Further, it is also conceivable that the metal to be filled is peeled off and the pinhole of alumite is used as an X-ray passage, for example, a very long X-ray (several tens to
Naturally, when the target is several hundred angstroms), it is sufficiently practical.

[0021]

As described above, according to the present invention, the focal point can be made very small with a small amount of power without using a pinhole, so that a small X-ray microscope can be realized by using this, and an invisible object can be realized. There is an advantage that the inspection becomes convenient.

[Brief description of the drawings]

FIG. 1A is a structural view of an X-ray generating tube according to one embodiment of the present invention, and FIG. 1B is a partially enlarged cross-sectional view showing a target of FIG.

FIG. 2 is a schematic structural view showing an example of a target including a porous film according to the present invention.

FIG. 3 is a configuration diagram illustrating an example of an X-ray microscope to which the present invention is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cathode, 2 ... Tube stem, 3 ... Aperture, 5 ... Tube wall, 6 ... Spherical target, 7 ... First DC power supply, 8
... second DC power supply, 11 ... target film, 12 ... electrodes,
13: insulating shim, 14: porous film, 21: anodized alumite, 22: metal pillar, 23: substrate, 30: X-ray generating tube, 31: sample, 32: fluorescent plate, 33: CCD camera,
34: display / analysis device, 35: control circuit, 36: objective lens.

Claims (2)

(57) [Claims] An X-ray source characterized in that a pinhole of a spherical alumite film is filled with a metal and electrons are made to collide with a target surface formed by coating the metal on the pinhole. 2. The X-ray source according to claim 1, wherein the spherical target surface is arranged on a surface of the vacuum tube facing the electron beam source to block the outside air.