JP2007212468A - X-ray microscopic inspection apparatus with high-resolution capability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray microscopic inspection apparatus which has superhigh-resolution power, enables a nondestructive inspection in a very short time and is equipped with excellent functions such as a target switching function, a high-precision electron probe controlling function, a CT function and an elemental analysis function. <P>SOLUTION: The apparatus includes a magnetic-field superposed lens where a magnetic field generation section is located in the vicinity of an electron generation section in an electron gun and a plurality of targets for generating X rays with different wavelengths and is so constituted that it can generate characteristic X rays of an applicable wavelength by switching the targets for generating X rays according to a purpose of an inspection. Moreover, the apparatus is equipped with functions such as an electron probe controlling function, an electron beam alignment function, the CT function and the element analysis function. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an X-ray inspection apparatus, and in particular, in an ultra-high resolution X-ray microscopic inspection apparatus using an electron source that emits a high-intensity electron current, high resolution CT (computerized tomography) The present invention relates to an X-ray microscopic inspection apparatus to which new functions such as a function, an element analysis function using fluorescent X-rays, and a target switching function including a plurality of metal targets and selecting a target according to the inspection purpose are added.

  As an inspection apparatus using X-rays, various industrial inspection apparatuses such as an X-ray microscope, a foreign substance inspection apparatus, and a fluorescent X-ray analysis apparatus, and medical X-ray apparatuses such as an X-ray diagnostic apparatus are known. FIG. 9 shows a configuration example of a conventional X-ray inspection apparatus. The X-ray inspection apparatus in this example uses a thermionic emission cathode 21b as an electron source and applies a high voltage between the grid 21a and the anode 21c to accelerate the electron Re from the electron source 21b, Electrons Re are focused on a target 23 made of a thin plate of a refractory metal such as tungsten by a lens 22 to obtain a minute point X-ray source 23a. Then, the inside of the sample (inspected object) 10 is enlarged and projected using the dotted X-rays Rx generated from the X-ray source 23a, and the fine structure inside the sample is inspected in a non-destructive manner.

  In the conventional X-ray microscopic inspection apparatus developed and commercialized by the present applicant, a two-stage reduction system using a lens having as little spherical aberration and chromatic aberration as possible in the focusing lens system and LaB6 having excellent properties as a thermionic source. It employs a (lanthanum hexaboride) cathode and uses a higher-sensitivity image intensifier tube, and the resolution reaches about 0.4 μm, down to 1 μm. This resolution is currently the highest value for a practical X-ray inspection system in the world (up to about 0.1 μm if the exposure time is ignored), but this is the technical limit. The resolution better than 0.1 μm expected in the present invention is not possible with the prior art (see the description of Non-Patent Documents 1 to 5 described later).

  On the other hand, these projection-type X-ray inspection apparatuses have recently been added with a micro CT function by several companies, and an arbitrary cross-sectional shape of a sample (specimen) can be observed. However, the resolution of the current CT image is several times worse than that of the original projection image, and development is hindered. This is due to the technical limitation of the axial run-out in the rotation of the sample necessary for obtaining the CT image and the essential limitation that the sample cannot be rotated close to the target.

  Traditionally, projection-type X-ray inspection devices only need to estimate the type of sample from the image contrast (ie, the difference in transmittance), and the need for elemental analysis has been extremely high, but this has never been done. It was. This is because if a conventional elemental detector is placed at the bottom of the sample, direct X-rays from the target and characteristic X-rays from the sample (in this case, fluorescent X-rays) overlap and cannot be distinguished. is there. Further, as shown in FIG. 9, there is no space for the detector above the sample 10 in the first place.

  Depending on the sample, it is necessary to change the contrast and observe, and therefore it is desirable to change the acceleration voltage and the target type. Changing the acceleration voltage is a common practice, but it is very difficult to change the target while maintaining a high vacuum, and it must be a large-scale device, so it has been performed online with conventional X-ray inspection equipment. Never been.

  Here, a conventional technique related to the resolution of the X-ray inspection apparatus will be described.

  For example, Non-Patent Document 1 to Non-Patent Document 5 disclose the technology related to resolution. Non-Patent Document 1 relates to an X-ray shadow microscope. Conventionally, the resolution is limited to 0.5 μm, but by using a very thin metal film (thickness 0.1 μm) for the target this time, the resolution is 0. It is described that 1 μm has been achieved. In addition, it is described that the exposure time was 5 minutes to obtain one image. After the paper of Non-Patent Document 1 was disclosed, research for shortening the exposure time was actively conducted. Came to be done. Non-Patent Document 2 is a research report on a transmission X-ray shadow microscope using an irradiation system of an electron microscope (Report of the Research Institute for Scientific Measurement, Tohoku University), which describes that a resolution of 0.1 μm has been achieved. In addition, theoretical analysis is performed for each factor that affects the resolution, and a conclusion that the spot size of the X-ray source has the most influence on the resolution is derived. Further, it is described that the fact that an electron beam is shaken with a deflection coil is used for focusing by utilizing the fact that it is an SEM (scanning electron microscope).

Non-Patent Document 3 describes the flow of X-ray microscopes to date, and particularly describes soft X-ray microscopes having a relatively short wavelength (1 to 100 mm) with reference to observation of biological samples. ing. Non-patent document 4 is substantially the same as the content of non-patent document 2, but shows a waveform that provides a basis for a resolution of 0.1 μm (text p.146). Non-Patent Document 5 explains the X-ray microscope in an easy-to-understand manner. It is the same as Non-Patent Documents 2, 3, and 4, and the image quality can be improved by changing the target for a sample that is difficult to contrast. It is shown.
Nixon, “High-resolution X-ray projection microscopy”, 1960, A232: p. 475-485 Keiji Yada and Hisashi Ishikawa, “Transmission X-ray shadow microscope using SEM”, Tohoku University Institute of Scientific Measurement, 1980, Vol. 29, No. 1, p. 25-42 Keiji Yada and Kunio Shinohara, “Development of Soft X-ray Microscope”, 1980, Biophysics Vol. 33 No. 4 p. 8-16 Keiji Yada, Shoichi Takahashi, “High-Resolution Projection X-ray Microscopy”, 1994, Chap. 8 p133-150 Keiji Yada and Kunio Shinohara, “Development of projection X-ray microscope and its application to biology”, 1996 Bulletin of Aomori Public University, Volume 1 p. 2-13

  The current semiconductor technology is continually miniaturized, and an X-ray microscope with a resolution of about 0.1 μm is expected to become essential in the near future. The field of nanotechnology covers information, medical care, and the environment. For example, in the micromachine referred to in medical care, the components constituting it are about 1 μm and are about to enter the nano order. Further, the current semiconductor technology is continually miniaturized, and a non-destructive inspection with a resolution of 0.1 μm or less using an unprecedented micro X-ray source is a necessary issue. In particular, in the information field, there is a big problem that the line width of the next generation VLSI is to be increased from the current 180 to 130 nm to 70 to 100 nm. At the same time, there are many cases in which a fine structure mainly composed of light elements is an object to be observed, and in order to contrast an image, a long wavelength X due to a low acceleration voltage of 10 to 20 kV, which has been difficult with a conventional X-ray inspection apparatus. Even when lines are used, maintaining high resolution is an important issue. At the same time, many new features will be desired.

  In order to manufacture an X-ray inspection apparatus with unprecedented high resolution, an electron source with higher luminance (a large amount of current per unit area / unit solid angle) and a large amount of radiation current is required. . In addition, an electron lens system that secures as much electron probe current as possible is also required. Further, it is necessary to devise a method for increasing the heat dissipation effect of the target so that the electron probe having such a high current density does not melt or evaporate even if it collides.

  The first new function that is desired to be put into practical use in an X-ray inspection apparatus having an ultra-high resolution (here, a resolution of 0.1 μm or less) is an X-ray generation target (X-ray source) of an electron probe. This is a function (hereinafter referred to as a focus adjustment function) that can easily perform adjustments such as focus adjustment and astigmatism correction of the electronic probe while viewing the image. Second, in order to enable inspection of a desired part of the object to be inspected and target switching, a function that allows the object to be scanned with the X-ray by freely shaking the electronic probe on the target surface. (Hereinafter referred to as an electronic probe control function). The third is an electron beam axis alignment function that can easily align the electron beam applied to the X-ray generation target. The fourth is a high-resolution and high-speed CT function. The fifth is an element analysis function for analyzing an element of a desired portion of the fluoroscopic image. For this, elemental analysis using fluorescent X-rays is used, but an X-ray target is required for this purpose. Therefore, the sixth function is a target switching function that includes a plurality of short-wavelength and long-wavelength targets in addition to the analysis target, and allows the target to be switched according to the inspection purpose.

  The present invention has been made under the circumstances as described above, and an object of the present invention is to provide an X-ray microscopic inspection apparatus that can greatly contribute to the field of nanotechnology. In detail, X is equipped with excellent functions such as non-destructive inspection with ultra-high resolution and very short time, as well as target switching function, high-precision electronic probe control function, CT function, and elemental analysis function. It is to provide a line microscopic inspection apparatus.

  The present invention includes an X-ray microscopic inspection apparatus having X-ray generation means for generating an X-ray by applying an electron beam from an electron source to an X-ray generation target, and inspecting an object to be inspected using the X-ray The above object of the present invention is to provide a magnetic field superposition lens in which a magnetic field generation unit is disposed in the vicinity of an electron generation unit of an electron gun, and a plurality of X-ray generation targets that generate X-rays having different wavelengths. This is achieved by switching the X-ray generation target according to the inspection purpose and generating characteristic X-rays of the wavelength.

  Another object of the present invention is to provide a reflection unit for detecting reflected electrons from an X-ray generation target of an electron probe formed through the magnetic field superimposing lens, with a detection unit disposed above the X-ray generation target. Further comprising: an electron detection means; and an electron image generation means for imaging an electron image of a target surface of the X-ray generation target based on a detection signal of the reflected electron detection means, and the X-ray generation of the electron probe. An adjustment including focus adjustment and astigmatism correction with respect to the target can be performed based on image information of the electronic image, and an electronic probe formed via the magnetic field superimposing lens is disposed on the X-ray generation target. Further comprising a scanning coil for freely swinging on the surface, disposed near the electron generating portion generated from the electron source, and through the magnetic field superimposing lens. An electron beam alignment coil that aligns the electron beam axis applied to the target for generating the beam before the acceleration of the electrons, and generates the X-ray by controlling the magnetic field using the electron beam focused through the magnetic field superimposing lens as an electron probe. A plurality of electron probe control means for scanning a target for scanning along a predetermined path, and a plurality of cross-sections of the object to be inspected based on transmission X-ray detection data of the object to be inspected obtained according to the scanning. This is achieved more effectively by further comprising X-ray tomographic image generation means for processing a single image to display the tomographic fine structure of the object to be examined.

  Another object of the present invention is to detect fluorescence X-rays generated from the object to be inspected by a detection unit disposed above the object to be inspected and outside the region of the X-rays generated from the X-ray generation target. An X-ray detection means; and an element analysis means for analyzing an element of the object to be inspected based on a fluorescent X-ray detection signal from the fluorescence X-ray detection means and a set value for specifying each element; The fluorescent X-ray detection means uses a cadmium telluride semiconductor for the detection unit for detecting the fluorescent X-ray, uses a thermal field emission cathode or a liquid metal field emission cathode as the electron source, the target and the By having pinholes that allow the X-rays generated from the target to pass between the object to be inspected, each can be achieved more effectively.

  According to the present invention, the X-ray generation target can be freely switched according to the inspection purpose without manually replacing the X-ray generation target. Inspection with lines can be easily performed. According to the second aspect of the present invention, the X-ray generating electron probe having a high current density can inspect the fine structure of the object to be inspected with high resolution and has an unprecedented high performance function. It becomes possible to provide a microscopic inspection apparatus. Specifically, it is possible to easily perform adjustment including focus adjustment and astigmatism correction with respect to the X-ray generation target of the electronic probe while viewing the image. According to the invention of claim 3, since the electronic probe can be freely controlled by the scanning coil, it is possible to inspect a desired part without rotating the object to be inspected. In addition, according to the invention of claim 4, since the electron beam axis is aligned before electron acceleration, the axis alignment of the X-ray generating electron probe having a high current density can be performed accurately and extremely easily. It can be carried out.

  Further, according to the invention according to claim 5, since it has a high-resolution and high-speed CT function, it is possible to perform non-destructive inspection at a nano scale with high accuracy, such as inspection of next-generation VLSI. Become. According to the sixth aspect of the present invention, the fluorescent X-rays generated from the test object are detected and the elements of the test object are analyzed with high accuracy without being affected by the X-rays generated from the target. be able to.

  By the way, in recent years, miniaturization of the minimum structural unit of semiconductor components has been progressing from microscale to nanoscale. It will be an indispensable technology in the future to inspect the internal microstructure of such parts in a non-destructive manner, realize the optimum contrast for each object to be inspected using characteristic X-rays, and perform elemental analysis of minute parts. Come. Currently, X-rays are the only means for observing and analyzing such internal structures with high resolution. Therefore, the present invention can greatly contribute to the field of nanotechnology.

  First, the basic configuration of the X-ray microscopic inspection apparatus according to the present invention will be described. In the present invention, the configuration of an X-ray microscopic inspection apparatus having a magnetic field superimposing lens described below includes a focus adjustment function by an electronic image, an electronic probe control function, an electron beam axis alignment function, a CT function, an element analysis function, and a target switching described later. The apparatus configuration is provided with means for realizing multiple functions such as functions.

  FIG. 1 shows an example of a basic configuration of an X-ray microscopic inspection apparatus according to the present invention. X-ray generation means includes an electron gun 1, an objective lens 2, a target 3, and the like. A module 1a, an electron source 1b, an anode 1c, and the like are included.

  In the present embodiment, a magnetic field superimposing lens 1d that has not been used in the X-ray microscope is disposed in the vicinity of the electron generating portion of the electron gun 1 of the X-ray microscopic inspection apparatus, and at least from the electron generating portion 1a to the electron accelerating means. The magnetic field generated by the magnetic field superimposing lens 1d is superimposed on the electric field generated by the electron gun up to the anode 1c, which is a component of the above, and the electron Re is focused while being accelerated by the anode 1c. That is, the loss electron dose of the focused electron beam is reduced by accelerating the focused electron beam Re immediately after being generated from the electron generator 1a. A focused electron beam (X-ray generating electron probe) having a high current density is applied to the target 3 to increase the X-ray dose generated from the target 3.

  So-called magnetic field superimposing lenses are conventionally used in electron beam apparatuses such as transmission electron microscopes and scanning electron microscopes. In these electron beam apparatuses, the spot diameter of the electron beam is small, but the amount of radiation current is small. A desired X-ray dose was not obtained from the target 3 and could not be applied to an X-ray microscopic inspection apparatus. The reason for this is that even if the amount of radiation current is considerably small in an electron microscope, it is sufficient as a signal amount, which is not so much a problem. This is because the problem of requiring a problem arises. In particular, a short exposure time is a necessary condition for spreading to industrial use. Further, an electron beam apparatus such as an electron microscope has a configuration in which a magnetic circuit or the like is incorporated in an electron gun chamber that requires ultra-high vacuum. In an X-ray microscopic inspection apparatus that requires a larger electron current (probe current), it has been difficult to solve the deterioration of the vacuum due to the gas emitted by the electron current and the magnetic circuit that generates heat. For this reason, there is no one used in an electron beam apparatus applied to an X-ray inspection apparatus. In the conventional X-ray inspection apparatus, an electron beam accelerated by an anode is bent by a lens and focused. In the X-ray microscopic inspection apparatus according to the present invention, this problem is solved by adopting a material that is said to have a small amount of gas release and vacuum-separating the magnetic circuit and water cooling.

  Here, the configuration of the magnetic field superimposing lens unique to the X-ray inspection apparatus according to the present invention will be described in comparison with that used in an electron beam apparatus such as a scanning electron microscope apparatus.

  FE (field emission) electron guns can be used in transmission electron microscopes, scanning electron microscopes, scanning transmission electron microscopes, or electron beam exposure devices because they can produce electron beams with high brightness and good coherence. ing. However, this performance is obtained with a significantly reduced reduction in light source crossover. The so-called electron beam probe also exhibits sufficient performance for the first time when it is a nanometer-sized (sub-nanometer) probe. However, when obtaining a probe in which the crossover of the light source is enlarged from submicron to micron size, it is difficult to obtain a sufficient probe current due to large aberration of the magnifying lens. This aberration is related to the distance from the position of the light source of the electron gun to the first stage of the magnifying lens (one or more stages), and is proportional to the 3rd power of the distance. Therefore, a so-called compound lens in which an electron lens is added to the electron gun portion has been devised and has been put into practical use in part.

However, in the conventional FE electron gun, as shown in the configuration example of FIG. 10, the entire housing of the electron gun chamber is formed of a vacuum sealing material 1B such as stainless steel, and is disposed in the ultra high vacuum. An independent magnetic circuit 1d ₁ (magnetic body 1d ₁₁ , excitation coil 1d ₁₂ or the like) is incorporated in the electron gun tip 1A. In such a configuration, it is very difficult to take out a magnetic circuit, cooling water, and a magnetic coil that generate heat in the FE electron gun chamber A in which ultrahigh vacuum is required, and to take out lead wires and pipes connected to them. In addition, an axis alignment mechanism between the electron gun and the electron lens is extremely difficult. On the other hand, an electron gun having a magnetic field superimposing lens according to the present invention (hereinafter referred to as a magnetic lens superimposing electron gun) has a magnetic field generating portion of a magnetic field superimposing lens composed of a magnetic circuit 1d ₁ or the like as an electron source of the electron gun. A configuration is provided in the vicinity of (electron gun tip 1 </ b> A that generates electrons) and at a site separated in vacuum from the electron gun chamber.

FIG. 2 shows a first configuration example of the magnetic lens superposing electron gun according to the present invention corresponding to the configuration of the conventional FE electron gun shown in FIG. 10, wherein 1A is an emitter, suppressor, extractor, etc. 1d ₁ is a magnetic circuit, 1d ₁₁ is a magnetic body constituting the magnetic circuit, 1d ₁₂ is an exciting coil for the magnetic circuit 1d ₁ , and s is two pole pieces of the electron lens. The interval b2 ("b" in FIG. 10) indicates the hole diameter of the pole piece. As shown in FIG. 2, in this embodiment, the electron gun chamber itself is incorporated in a magnetic circuit 1d ₁ made of a magnetic material 1d ₁₁ or the like. In detail, as a component of the magnetic field superimposing lens 1d, an electron gun housing portion in which, for example, the cross section is rectangular as shown in FIG. The electron gun is incorporated in the electron gun housing part. That is, a part of the casing (a part or the whole of the casing such as the top plate, the bottom plate, and the outer cylinder) constituting the electron gun chamber is a part or the whole of the magnetic circuit (magnetic field generator), and the electron gun and the electron lens 1d. Are separated in a vacuum.

  In this first configuration example, strong excitation is required, but since the object surface (light source crossover) is arranged behind the center of the lens field, the aberration coefficient (especially spherical aberration) can be sufficiently reduced. . The reason is that, generally, when the distance from the object surface (in this case, the light source crossover) to the lower pole of the electron lens is fixed, the larger the hole diameter and interval of the pole pieces, the smaller the spherical aberration. . Although chromatic aberration is not limited to this, chromatic aberration can be ignored as an object of the present invention. Further, since the structure is separated from an electron gun chamber that requires ultra-high vacuum, there is an effect that it is easy to take out a vacuum seal, cooling water, lead wires, and the like.

FIG. 3 shows a second configuration example of the magnetic lens superposing electron gun according to the present invention corresponding to the first configuration example shown in FIG. 2, and in the present embodiment, as shown in FIG. A convex electron gun chamber A is provided on the top of the magnetic field superimposing lens 1d made of, for example, the magnetic body 1d ₁₁ having a concave cross section so that the electron gun tip 1A and the magnetic body 1d ₁₁ are closer to each other. The electron gun tip 1A is inserted into the magnetic field from above the magnetic field superimposing lens 1d. In the first configuration example shown in FIG. 2, an extremely strong magnetic field can be obtained, which is extremely effective for a low acceleration electron beam, but is not necessarily advantageous to a high acceleration electron beam to some extent. . Therefore, the hole diameter b of the pole piece (in this example, the hole diameters b1 and b2 having different upper and lower sizes) and the interval s are reduced so that the electron gun tip 1A is placed in the magnetic field so that small excitation is sufficient. It is this embodiment that has been inserted.

  In both the first and second configuration examples of the above-described magnetic field lens superimposing electron gun, the magnetic field superimposing lens has a configuration in which the magnetic field generating unit is disposed in the vicinity of the electron generating unit of the electron gun and separated from the electron gun chamber. The electron gun and the electron lens can be separated in a vacuum (it is easy to achieve ultra-high vacuum including baking), and the electric field created by the electron gun and the magnetic field created by the electron lens can be easily superimposed. effective. In addition, in order to obtain a high-resolution X-ray microscopic inspection apparatus at a nanoscale of 40 nm to 100 nm, the X-ray microscopic inspection apparatus of FIG. 1 is a component of the X-ray generation means, in addition to the magnetic field superimposing lens 1d. The first electron to use the “thermal field emission cathode” or “liquid metal field emission cathode”, whose luminance is two orders of magnitude higher than that of the LaB6 cathode and whose effective electron source size is three orders of magnitude smaller. A source 1b is provided. In the case of an electron source using a liquid metal, a liquid metal (a metal such as In (indium) or Ga (gallium) having a relatively low vapor pressure at the melting point among low melting point metals) is supplied to the tip of the electron generation unit. The configuration is as follows.

  Further, in order to realize a target that can withstand a thermal load even if the temperature rise of the target due to the electron beam is greatly reduced and the X-rays converted from the electron beam are greatly increased, , Diamond (thin plate-shaped diamond formed by CVD (chemical vapor deposition)) with extremely high thermal conductivity and extremely high melting point despite being an insulator is easily used as a heat sink. A "target with a diamond heat sink" having a structure in which a target material is deposited on the diamond by CVD is provided.

  As a lens for focusing an electron beam, in principle, only the above-described magnetic field superimposing lens 1d may be used, and the electron lens (objective lens) 2 on the target 3 side shown in FIG. By providing it and focusing the electron beam in two stages, the degree of freedom in selecting a desired electron probe size and probe current is greatly increased. Compared with the conventional apparatus (see FIG. 9), in the X-ray microscopic inspection apparatus of the present invention, the focal length of the objective lens 2 is long, and a long working distance (several numbers that cannot be obtained with the conventional X-ray microscopic inspection apparatus) cm) can be realized. Therefore, a space between the objective lens 2 and the target 3 can be widened, and peripheral devices for inspection can be installed in the space. In the present invention, a detection device, which will be described later, is arranged in the above-described space, and the X-ray generating electron probe having a high current density can inspect the fine structure of the object to be inspected with high resolution and has an unprecedented function. A high-performance X-ray microscopic inspection system has been realized.

  Hereinafter, an X-ray microscopic inspection apparatus equipped with each function according to the present invention will be described.

  In the X-ray microscopic inspection apparatus of the present invention, the first to sixth functions described in [Problems to be solved by the invention], that is, (1) Focus adjustment functions such as focus adjustment and astigmatism correction by an electronic image , (2) An electronic probe control function that enables the X-ray to scan the object to be inspected by freely swinging the electron probe on the target surface, and (3) an electron that performs axis alignment of the electron beam applied to the X-ray generation target Line-axis alignment function, (4) High-resolution and high-speed CT function, (5) Element analysis function to analyze elements of desired part of fluoroscopic image, (6) Target can be switched according to purpose according to inspection purpose The apparatus configuration is added with at least one of the target switching functions. In order to realize these functions, the electron source 1b and the target 3 with the diamond heat sink using the above-mentioned “thermal field emission cathode” or “liquid metal field emission cathode” are not indispensable as constituent elements. An electron source using a LaB6 cathode and a target that does not have a diamond heat sink may be used. However, in order to realize a higher-resolution device, this embodiment has a device configuration including the above-described components.

  FIG. 4 shows an example of the configuration of the multifunctional X-ray microscopic examination apparatus according to the present invention corresponding to FIG. 1, and the same components as those in the apparatus of FIG. To do.

  As described above, the X-ray microscopic inspection apparatus according to the present invention introduces an electron lens (magnetic field superimposing lens) 1d that focuses while accelerating electrons Re, thereby expanding the number of times as a whole while reducing a loss electron dose. It is made to operate as a system. In this way, since the lens system is operated not by a reduction system but by an enlargement system, the focal length of the objective lens 2 is long, and a long working distance (several centimeters) that cannot be obtained by a conventional X-ray microscopic inspection apparatus can be realized. it can.

  In the present embodiment, between the objective lens 2 and the target 3, a deflection coil (scanning coil) 4 and a detection unit of the reflected electron detector 12 including a reflected electron detection electrode 12 a are provided. The deflection coil 4 is a coil for freely swinging an electron probe (electron beam Re) formed via the magnetic field superimposing lens 1d on the surface of the target 3 for X-ray generation. In this example, as shown in FIG. 4, the deflection coil 4 is formed in the lower part on the center side of the objective lens 2. The backscattered electron detection electrode 12a is an electrode insulated from the mirror body for detecting backscattered electrons from the target 3 for X-ray generation, and the detection signal of the backscattered electron detector 12 is sent to the analysis computer 15 in this example. It is inputted, and an electronic image of the target surface is imaged and displayed on a monitor.

  Further, a fluorescent X-ray detector 13 for detecting fluorescent X-rays generated from the inspection object 10 above the inspection object (sample) 10 and outside the X-ray generation area generated from the X-ray generation target 3. Is arranged. Detection information of fluorescent X-rays detected by the fluorescent X-ray detector 13 is input to the analysis computer 15 via the pulse height analyzer 14, and based on the detection information of fluorescent X-rays and set values for specifying each element. Thus, the analysis process of the element of the object to be inspected is performed.

  In the configuration as described above, each function of the X-ray microscopic inspection apparatus of the present invention will be described. In the X-ray microscopic inspection apparatus shown in FIG. 4, a reflected electron detector 12 is disposed in the vicinity of the X-ray target 3 in order to make the axis adjustment of the electron beam extremely easy. An electronic image of the surface of the target 3 for X-ray generation can be imaged. By stopping the scanning when the reflected electron image of the target 3 becomes the sharpest by adjusting the focus (the focus adjustment of the electron probe with respect to the X-ray generation target), the astigmatism correction of the electron probe, etc. A desired electron probe can be obtained. This method is the first attempt in an X-ray microscopic inspection apparatus. The adjustment by the reflected electron image is performed by, for example, electromagnetically adjusting the objective lens 2 while observing an image imaged by the analysis computer 15, but a drive mechanism that can be controlled by an external signal is provided. Thus, it may be configured to automatically adjust based on the image information of the electronic image.

  The scanning by the electronic probe is performed using a deflection coil (scanning coil) around the electronic probe, and is controlled so as to scan the X-ray generation target along a predetermined path.

  By the way, in order to realize a high-resolution X-ray microscopic inspection apparatus, in order to generate X-rays with a large X-ray dose, a high intensity, and a small focus size, the target (inspected object) 10 is irradiated. Although it is important that the electron beam applied to 3 has a small focusing loss and a large amount of electrons due to a high-performance lens, the direction and position of the axis of the electron beam for generating X-rays are also important. In this embodiment, as illustrated in FIG. 1 and FIG. 4, for the first time as an X-ray microscopic inspection apparatus, an electron beam axis alignment coil 1 e is arranged in the vicinity of an electron generator 1 </ b> A (in the immediate vicinity of an electron source). By using this axis alignment coil 1e, the electron beam before being accelerated by the anode 1c is shifted in the X and Y directions to align the axes, so that the alignment of the electron beam with respect to the X-ray source can be performed accurately and extremely easily. I have to. This axial alignment is performed while viewing the reflected electron image imaged by, for example, the analysis computer 15 together with the focus adjustment described above.

  In the present embodiment, the scanning coil 4 has the ability to scan with an electron beam (electron probe for X-ray generation) and observe the reflected electron image on the target surface based on the detection signal of the reflected electron detector 12. By controlling the current to flow, the electron probe Re is deflected and scanned on the target 3 in a circular manner, for example, as in the example of FIG. Even if the body 10 is not rotated, a large number of images Is can be captured while the electron beam Re is swung in a circle on the target 3. Therefore, an arbitrary cross-sectional area can be observed by CT processing. This method is equivalent to rotating the object to be inspected with extremely high accuracy in a situation where the object to be inspected 10 can be expected to have a high resolution close to the target 3, and can realize a CT function that is several times higher in resolution and speed. .

  Here, an X-ray tomographic imaging process by scanning with an electronic probe will be described. In the present embodiment, an electron probe control unit that scans the X-ray generation target 3 along an arbitrary path by controlling the magnetic field using the electron beam focused through the magnetic field superimposing lens 1d as an electron probe, and scanning Based on the transmission X-ray detection data of the inspected object 10 obtained according to the above, a plurality of images relating to different cross sections of the inspected object 10 can be processed to display the fine structure of the tomography of the inspected object 10 X-ray tomographic image generation means. Control and image processing of these electronic probes are performed by the analysis computer 15 or a control circuit (not shown) or another computer.

  The scanning coil 4 shown in FIG. 4 includes, for example, four arc-shaped coils 4Xa, 4Xb, 4Ya, and 4Yb arranged in an annular shape so as to face each other in the X-axis direction and the Y-axis direction, as shown in FIG. Is done. Then, the current flowing through these scanning coils 4 is controlled to change the magnetic field around the electron probe. As a result, by changing the position and direction of the electron probe, the X-ray image is obtained by scanning in a desired direction such as scanning the object 10 in a circular shape.

  FIG. 7A schematically shows a control example of the scanning coil 4 when scanning with the electronic probe in the horizontal direction and the vertical direction. FIG. 5B schematically shows a control example of the scanning coil 4 when scanning in the circular direction. As shown in FIGS. 7A and 7B, by controlling the amount of current flowing through the coils 4Xa and 4Xb in the X-axis direction and the coils 4Ya and 4Yb in the Y-axis direction, the electron probe is deflected. By continuously changing the position of the X-ray source 23a, the inspection object 10 is scanned to obtain an X-ray image thereof.

  Next, the elemental analysis function will be described. When the inspection object 10 is irradiated with X-rays, fluorescent X-rays having wavelengths specific to the constituent elements of the inspection object are generated in all directions. If this can be detected, elemental analysis of the object to be inspected becomes possible. On the other hand, continuous X-rays and characteristic X-rays are emitted from the target 3. In particular, continuous X-rays are irradiated downward along the incident direction of electrons. For this reason, even if a fluorescent X-ray detector is placed below the object to be inspected, continuous X-rays become the background and fluorescent X-rays cannot be measured. The X-ray microscopic inspection apparatus according to the present invention has a long focal distance of the objective lens 2 and can realize a long working distance (several centimeters) that cannot be obtained by the conventional X-ray microscopic inspection apparatus as described above. As shown, it is possible to secure a space for placing the fluorescent X-ray analysis detector 13 above the inspection object 10 and outside the X-ray generation region (in this example, obliquely above the X-ray target).

As the fluorescent X-ray detector 13, CdTe (cadmium telluride semiconductor) which can be used without cooling and has high detection sensitivity is used. A pinhole of about 10-20 μm is provided in order to specify the site of analysis, and the X-ray that has passed through the pinhole 5 is analyzed at the same time as the fluorescent X-rays that have been scanned and scanned upward from the top surface of the inspection object are analyzed. Enable positional identification on the image.

  Since the generation efficiency of hard X-rays with high energy as primary X-rays is higher than that of fluorescent X-rays, it is desirable to use an X-ray with an atomic number as large as possible. At the same time, it is necessary that the characteristic X-ray from the target is not confused with the fluorescent X-ray of the object to be inspected. In addition to the resolution, the contrast of an important image depends on the acceleration voltage and the type of target material. A conventional X-ray inspection apparatus uses a single target material, and there is no mechanism that uses various characteristic X-rays by changing the target.

  In the present invention, Ti (titanium), Cr (chromium), Ge (germanium), in addition to W (tungsten), which has been generally used as a target, in consideration of fluorescent X-ray analysis and light element samples, A refractory metal such as Mo (molybdenum), Rh (rhodium), Re (rhenium), Ir (iridium), and Pt (platinum) is formed into a fine band shape by CVD or sputtering as shown in FIG. A function of moving an electron beam is added to the scanning coil 4 immediately above the target 3 so that each target 3 (3a, 3a, 3c in this example) can be selected while viewing the reflected electron image according to the observation purpose. To. As a result, it becomes possible to easily select a target material that provides an optimum contrast for each sample.

  Table 1 below shows the atomic numbers, wavelengths of Kα and Lα rays, and melting points of these target materials. From Table 1, it can be seen that “Rh” is suitable as an analysis target from the viewpoint of a material that is not often used for an observation sample.

なお、上述した実施の形態においては、全ての機能を搭載したＸ線顕微検査装置を例として説明したが、個々の機能を独立して搭載することができる。

In the above-described embodiment, the X-ray microscopic inspection apparatus having all the functions is described as an example, but each function can be independently mounted.

It is the schematic which shows an example of the basic composition of the X-ray microscope inspection apparatus which concerns on this invention concerning this invention. It is a schematic diagram which shows the 1st structural example of the magnetic lens superimposition electron gun which concerns on this invention. It is a schematic diagram which shows the 2nd structural example of the magnetic lens superimposed electron gun which concerns on this invention. It is a schematic diagram which shows an example of a structure of the X-ray microscopic inspection apparatus which has a multifunction which concerns on this invention. It is a schematic diagram for demonstrating CT function in this invention. It is a schematic diagram which shows the structural example of a scanning coil. It is a figure for demonstrating the control system of the scanning coil for swinging an electronic probe freely. It is a figure for demonstrating the target switching function in this invention. It is the schematic which shows an example of a structure of the conventional X-ray inspection apparatus. It is a schematic diagram which shows the structural example of the conventional FE electron gun.

Explanation of symbols

1 Magnetic lens superimposed electron gun 1A Electron gun tip (electron generator)
1B Vacuum sealing material 1a Schottky module 1b Liquid metal field emission cathode or thermal field emission cathode (electron source)
1c Anode 1d Magnetic field superposition lens 1d ₁ Magnetic circuit 1d ₁₁ Magnetic body 1d ₁₂ Excitation coil 1e Axis alignment coil 2 Objective lens 3 Target with diamond heat sink 3a Target material 3b Diamond plate 4 Scanning coil (deflection coil)
5 Pinhole 10 Inspected object (sample)
DESCRIPTION OF SYMBOLS 11 X-ray detector 12 Backscattered electron detector 12a Backscattered electron detection electrode 13 Fluorescent X-ray detector 14 Pulse height analyzer 15 Computer for analysis 21 Thermionic emission electron gun 21a Grid 21b Thermionic emission cathode (electron source)
21c Anode 22 Electron lens (objective lens)
23 target 23a X-ray source 24 detector Re electron (electron beam)
Rx X-ray

Claims (10)

In an X-ray microscopic inspection apparatus that has X-ray generation means for generating X-rays by applying an electron beam from an electron source to an X-ray generation target, And a plurality of X-ray generation targets for generating X-rays of different wavelengths, and the X-ray generation target according to the inspection purpose. A high-resolution X-ray microscopic inspection apparatus characterized in that the characteristic X-rays of the wavelength can be generated by switching. A detection unit is disposed above the X-ray generation target, and a reflected electron detection means for detecting reflected electrons from the X-ray generation target of an electron probe formed via the magnetic field superimposing lens; and the reflected electrons Electronic image generation means for imaging an electron image of the target surface of the X-ray generation target based on a detection signal of the detection means, and focus adjustment and astigmatism of the electron probe with respect to the X-ray generation target The high-resolution X-ray microscopic inspection apparatus according to claim 1, wherein adjustment including correction can be performed based on image information of the electronic image. The high-resolution X-ray microscope according to claim 1, further comprising a scanning coil for freely swinging an electron probe formed through the magnetic field superimposing lens on the surface of the X-ray generation target. Inspection device. An electron beam alignment coil is further provided that is disposed in the vicinity of an electron generation portion generated from the electron source and aligns an electron beam axis applied to the X-ray generation target via the magnetic field superimposing lens before electron acceleration. The high-resolution X-ray microscopic inspection apparatus according to claim 1. An electron probe control means for scanning the X-ray generation target along a predetermined path by controlling the magnetic field using an electron beam focused through the magnetic field superimposing lens as an electron probe, and obtained according to the scanning An X-ray tomographic image enabling processing of a plurality of images relating to different cross sections of the object to be inspected and displaying a fine structure of the tomographic object on the object to be inspected based on detection data of transmitted X-rays of the object to be inspected The high-resolution X-ray microscopic inspection apparatus according to claim 1, further comprising a generation unit. A fluorescent X-ray detection means for detecting fluorescent X-rays generated from the inspection object, wherein a detection unit is disposed above the inspection object and outside the X-ray generation region generated from the X-ray generation target, and the fluorescent light 2. An element analyzing means for analyzing the element of the object to be inspected based on a fluorescent X-ray detection signal from the X-ray detecting means and a set value for specifying each element. The high-resolution X-ray microscopic inspection apparatus described. The high-resolution X-ray microscopic inspection apparatus according to claim 6, wherein the fluorescent X-ray detection unit uses a cadmium telluride semiconductor for the detection unit that detects the fluorescent X-ray. The high-resolution high-resolution X-ray microscopic inspection apparatus according to claim 1, wherein a thermal field emission cathode or a liquid metal field emission cathode is used as the electron source. The high-resolution X-ray microscopic inspection apparatus according to claim 1, wherein the magnetic field generation unit is disposed outside an ultra-high vacuum electron gun chamber in which the electron gun is provided. The high-resolution high-resolution X-ray microscopic inspection apparatus according to claim 1, further comprising a pinhole that allows X-rays generated from the target to pass between the target and the inspection object.

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