JP2020145100A - Mass spectrometer - Google Patents

Abstract

To observe the surface of a sample with high optical resolution in a mass spectrometer.SOLUTION: A mass spectrometer includes: a plate-shaped extraction electrode 19 that includes a sample stage 14 provided with a sample arrangement surface and an opening 20 through which ions pass, is provided at a position facing the sample arrangement surface, and extracts ions generated from a sample 12 arranged on the sample arrangement surface in a direction orthogonal to the sample arrangement surface; ion separation/detection units 23 and 24 that separate and detect the ions extracted by the extraction electrode 19 according to the mass-to-charge ratio; and a camera 38 that photographs the surface of the sample 12, wherein the extraction electrode 19 transmits visible light, and an optical path of light emitted from the sample 12 and incident on the camera 38 passes through a region of the extraction electrode 19 other than the opening 20.SELECTED DRAWING: Figure 1

Description

The present invention relates to a mass spectrometer.

The mass spectrometer separates the ionization unit that ionizes the components in the sample, the extraction electrode that draws out the ions derived from the sample from the vicinity of the sample and accelerates them, and the ions extracted by the extraction electrode according to the mass-to-charge ratio. It includes an ion separation / detection unit for detection. There are various methods for ionizing a sample in the ionization section, but the laser desorption / ionization method is widely used in the analysis of solid samples.

In the laser desorption / ionization method, a laser beam of ultraviolet rays is applied to the surface of a solid sample (for example, a flaky sample such as a biological tissue section, a metal plate, or a semiconductor substrate, or a liquid sample solidified by drying or the like). This is a method of irradiating and desorbing a part of the sample from the surface by the energy of the laser beam to ionize the sample. A mass spectrometer that ionizes a sample by a laser desorption / ionization method is called a laser ionization mass spectrometer.

The laser ionization mass spectrometer may be provided with a CCD camera for observing the surface of the sample set inside the device. When analyzing a sample by such a laser ionization mass spectrometer, first, the surface of a solid sample set inside the mass spectrometer is photographed by the CCD camera, and the obtained image is displayed on the screen of the monitor. Is displayed in. While checking the image, the person in charge of analysis (user) determines a region (analysis target region) to be subjected to mass spectrometry on the sample, and causes a laser ionized mass spectrometer to perform mass spectrometry on the region. Alternatively, during mass spectrometry by the laser ionization mass spectrometer, the user observes the image taken by the CCD camera to determine the position on the sample where the laser beam is irradiated, or the surface of the sample. It is also performed in real time to confirm whether or not any defects (sample peeling, impurity adhesion, etc.) have occurred.

Japanese Unexamined Patent Publication No. 2011-232180 ([0005]-[0011])

In the laser ionization mass spectrometer, ions generated from the sample by irradiation with laser light are drawn from the vicinity of the sample by an electric field formed by a plate-shaped extraction electrode arranged at a position facing the sample. The extraction electrode is provided with an opening for passing ions in the center thereof, and the ions extracted from the vicinity of the sample are guided to the ion separation / detection unit through this opening.

However, since the above-mentioned extraction electrode is arranged in the vicinity of the sample, in the conventional laser ionization mass spectrometer, the optical path of the optical system (imaging optical system) for photographing by the CCD camera is not blocked by the extraction electrode. , The arrangement of the photographing optical system was limited (see, for example, Patent Document 1). Therefore, the numerical aperture of the photographing optical system cannot be increased, and it is difficult to observe the surface with sufficient optical resolution.

The present invention has been made in view of the above points, and an object of the present invention is to provide a mass spectrometer capable of observing the surface of a sample with high optical resolution.

The mass spectrometer according to the present invention made to solve the above problems
A sample stage with a sample placement surface and
A plate-shaped electrode having an opening through which ions pass, which is provided at a position facing the sample placement surface and in which ions generated from a sample placed on the sample placement surface are orthogonal to the sample placement surface. With an extraction electrode that can transmit visible light,
An ion separation / detection unit that separates and detects the ions extracted by the extraction electrode according to the mass-to-charge ratio, and
A camera that photographs the surface of the sample and
It has a photographing optical path forming portion that forms an optical path for light emitted from the sample and passing through a region other than the opening of the extraction electrode toward the camera.

According to the present invention, there is provided a mass spectrometer capable of observing the surface of a sample with high optical resolution.

The schematic diagram which shows the main part structure of the laser ionization mass spectrometer which concerns on 1st Embodiment of this invention. The schematic diagram which shows the modification of the laser ionization mass spectrometer which concerns on this embodiment. The schematic diagram which shows the main part structure of the secondary ion mass spectrometer which concerns on 2nd Embodiment of this invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 shows a schematic configuration of a mass spectrometer according to the first embodiment of the present invention. This mass spectrometer is a laser ionization mass spectrometer that uses a laser desorption / ionization (LDI) as a sample ionization method. For LDI, a matrix assisted laser desorption / ionization method (MALDI) that uses a matrix reagent as a desorption / ionization support material, and a metal or metal oxide without using a matrix reagent. Surface-Assisted Laser Desorption / Ionization (SALDI), which uses nanoparticles on the surface of a porous substrate such as nanoparticles or porous silicon plates as a desorption / ionization support material, is included.

The laser ionized mass spectrometer according to the present embodiment includes a vacuum chamber 11 that is evacuated by a vacuum pump (not shown), a sample stage 14 in which the sample plate 13 is set, and a laser that emits ultraviolet rays to the sample 12 on the sample plate 13. A laser light source 15 for irradiating light, a mass separator 23 that separates ions generated from a sample 12 based on a mass charge ratio, an ion detector 24 that detects the separated ions, a sample stage 14, and a mass. An extraction electrode 19 arranged between the separators 23, a camera 38 for photographing the surface of the sample 12, and an illumination light source 31 for illuminating the sample 12 for photographing with the camera 38 are provided. The mass spectrometer 23 and the ion detector 24 correspond to the ion separation / detection unit in the present invention.

The sample 12 to be analyzed is coated or placed on the sample plate 13, and the sample plate 13 is placed on the upper surface of the sample stage 14 (corresponding to the sample placement surface in the present invention). The sample stage 14 is movable in two axial directions, the X-axis and the Y-axis, which are orthogonal to each other by the driving force of a motor (not shown).

The extraction electrode 19 is a plate-shaped electrode arranged in the vicinity of the sample 12 at a position facing the upper surface of the sample stage 14, and is provided with an ion passage port 20 which is an opening for passing ions in the center. There is. The ion passage port 20 is located directly above the irradiation position of the laser beam on the surface of the sample 12.

The laser beam for ionizing the sample 12 is emitted from a laser light source 15 provided outside the vacuum chamber 11, narrowed down to a minute diameter by the condensing optical system 16, and then provided on the wall surface of the vacuum chamber 11. It enters the inside of the vacuum chamber 11 through the window portion 17. The laser beam that has entered the vacuum chamber 11 is reflected by the reflection optical system 18, passes through the ion passage port 20 of the extraction electrode 19, and enters the sample 12.

A voltage is applied between the extraction electrode 19 and the sample stage 14 by a high-voltage power supply 21, and the application of this voltage forms an electric field that accelerates ions in the Z-axis direction orthogonal to the X-axis and the Y-axis. .. The ions generated from the surface of the sample 12 by the irradiation of the laser beam move toward the extraction electrode 19 by the action of the electric field and pass through the ion passage port 20 of the extraction electrode 19.

An ion transport optical system 22 for transporting ions while converging them by the action of an electric field is installed in the subsequent stage of the extraction electrode 19, and in the subsequent stage, a mass separator 23 that separates ions according to the mass-to-charge ratio. And an ion detector 24 for detecting the separated ions are installed. As the mass separator 23, for example, various types such as an ion trap type, a quadrupole type, a double-focusing type, and a time-of-flight type can be used.

The detection signal by the ion detector 24 is sent to the signal processing unit 25. Based on the detection signal, the signal processing unit 25 generates a mass spectrum having the mass-to-charge ratio of ions on the horizontal axis and the intensity of ions on the vertical axis.

As a characteristic feature of this embodiment, the extraction electrode 19 is made of a material having conductivity and capable of transmitting visible light. Further, an optical path for illuminating the surface of the sample 12 and an optical path for photographing the surface of the sample 12 pass through a region of the extraction electrode 19 other than the ion passage port 20. That is, the illumination light (visible light) emitted from the illumination light source 31 includes the condensing optical system 32, the window portion 33 provided on the wall surface of the vacuum chamber 11, and the reflected optical system 34 provided in the vacuum chamber 11. After that, it is incident on the upper surface of the extraction electrode 19. The condensing optical system 32, the window portion 33, and the reflecting optical system 34 correspond to the illumination optical path forming portion in the present invention. Then, the illumination light passes through the inside of the extraction electrode 19 and is incident on the surface of the sample 12 arranged below the extraction electrode 19. Further, of the illumination light, a part of the light reflected on the surface of the sample 12 is incident on the lower surface of the extraction electrode 19, passes through the inside of the extraction electrode 19, and is reflected optical provided in the vacuum chamber 11. The light enters the camera 38 via the system 35, the window portion 36 provided on the wall surface of the vacuum chamber 11, and the condensing optical system 37 provided outside the vacuum chamber 11. The reflective optical system 35, the window portion 36, and the condensing optical system 37 correspond to the photographing optical path forming portion in the present invention. The image taken by the camera 38 is sent to the signal processing unit 25 and displayed on the screen of the monitor 26 connected to the signal processing unit 25.

The lead electrode 19 is assumed to be entirely made of a "material having conductivity and capable of transmitting visible light", and the surface of the electrode body made of a non-conductive visible light transmitting material. A thin film made of "a material having conductivity and capable of transmitting visible light" may be formed. An example of the latter is a thin film of indium tin oxide (ITO), zinc oxide, tin oxide, titanium oxide, graphene, or aluminum formed on the surface of an electrode body made of glass. Be done.

As described above, in the laser ionized mass analyzer according to the present embodiment, since the extraction electrode 19 can transmit visible light, the arrangement of the optical system (illumination optical system) for illuminating the sample 12 and the sample surface are photographed. The arrangement of the optical system (photographing optical system) for this purpose is not restricted by the position and shape of the extraction electrode 19. This makes it possible to mount an illumination optical system and a photographing optical system having high optically high performance.

[Modification of Embodiment 1]
In the above embodiment, the sample 12 is irradiated with a laser beam for ionizing the sample 12 through the ion passage port 20 of the extraction electrode 19, but as shown in FIG. 2, the laser beam is also extracted. The sample 12 may be irradiated by passing through a region of the electrode 19 other than the ion passage port 20. In this case, the condensing optical system 16, the window portion 17, and the reflecting optical system 18 correspond to the laser optical path forming portion in the present invention. As a result, the arrangement of the optical system (irradiation optical system) for irradiating the sample surface with the laser beam is not restricted by the position and shape of the extraction electrode 19, so that the degree of freedom in the arrangement of the irradiation optical system is increased. Can be done. In this case, the extraction electrode 19 is capable of transmitting both visible light and ultraviolet light. Such an extraction electrode 19 is made entirely of "a material having conductivity and capable of transmitting both visible light and ultraviolet light", or is non-conductive and is visible and ultraviolet light. It is assumed that a thin film made of "a material having conductivity and capable of transmitting both visible light and ultraviolet light" is formed on the surface of an electrode body made of a material capable of transmitting. As an example of the latter, for example, a thin film of ITO, zinc oxide, tin oxide, titanium oxide, graphene, aluminum or the like is formed on the surface of an electrode body made of quartz glass.

[Embodiment 2]
FIG. 3 shows a schematic configuration of the mass spectrometer according to the second embodiment of the present invention. This mass spectrometer is a secondary ion mass spectrometer that performs mass spectrometry by secondary ion mass spectrometry (SIMS). In the secondary ion mass spectrometry method, the surface of the sample 12 is irradiated with a primary ion beam, and the mass-to-charge ratio of the secondary ions emitted from the sample surface by the irradiation of the primary ion beam is measured.

The secondary ion mass spectrometer according to the present embodiment has a vacuum chamber 41 that is evacuated by a vacuum pump (not shown), a sample stage 44 in which the sample plate 43 is set, and a primary ion beam on the sample 42 on the sample plate 43. An ion gun 45 for irradiating the sample 42, a mass separator 53 that separates secondary ions generated from the sample 42 based on a mass charge ratio, an ion detector 54 that detects the separated secondary ions, and a sample stage. A drawer electrode 49 arranged between the 44 and the mass spectrometer 53, a camera 68 for photographing the surface of the sample 42, and an illumination light source 61 for illuminating the sample 42 for photographing with the camera 68 are provided. There is. The mass spectrometer 53 and the ion detector 54 correspond to the ion separation / detection unit in the present invention.

The sample 42 to be analyzed is held on the sample plate 43, and the sample plate 43 is placed on the upper surface of the sample stage 44 (corresponding to the sample placement surface in the present invention). The sample stage 44 is movable in two axial directions, the X-axis and the Y-axis, which are orthogonal to each other by the driving force of a motor (not shown).

The extraction electrode 49 is a plate-shaped electrode arranged in the vicinity of the sample 42 at a position facing the upper surface of the sample stage 44, and is provided with an ion passage port 50 which is an opening for passing ions in the center. There is. The ion passage port 50 is located directly above the irradiation position of the primary ion beam on the surface of the sample 42.

The primary ion beam for ionizing the sample 42 is emitted from an ion gun 45 whose tip is inserted into the vacuum chamber 41, and is incident on the sample 42 through the ion passage port 50 of the extraction electrode 49. As the ions constituting the primary ion beam, for example, argon ions, oxygen ions, cesium ions and the like are used.

A voltage is applied between the extraction electrode 49 and the sample stage 44 by a high-voltage power supply 51, and this voltage application forms an electric field that accelerates ions in the Z-axis direction orthogonal to the X-axis and the Y-axis. .. The ions (secondary ions) generated from the sample surface by the irradiation of the primary ion beam move toward the extraction electrode 49 by the action of the electric field and pass through the ion passage port 50 of the extraction electrode 49.

An ion transport optical system 52 for transporting ions while converging them by the action of an electric field is installed in the subsequent stage of the extraction electrode 49, and in the subsequent stage, a mass separator 53 that separates ions according to the mass-to-charge ratio. And an ion detector 54 for detecting the separated ions are installed. As the mass separator 53, for example, various types such as an ion trap type, a quadrupole type, a double-focusing type, and a time-of-flight type can be used.

The detection signal by the ion detector 54 is sent to the signal processing unit 55. Based on the detection signal, the signal processing unit 55 generates a mass spectrum having the mass-to-charge ratio of ions on the horizontal axis and the intensity of ions on the vertical axis.

As a characteristic configuration of the present embodiment, the extraction electrode 49 is made of a material having conductivity and capable of transmitting visible light, and is used to photograph the optical path for illuminating the sample surface and the sample surface. The optical path of the lead electrode 49 passes through a region other than the ion passage port 50 of the extraction electrode 49. That is, the illumination light (visible light) emitted from the illumination light source 61 includes the condensing optical system 62, the window portion 63 provided on the wall surface of the vacuum chamber 41, and the reflected optical system 64 provided in the vacuum chamber 41. After that, it is incident on the upper surface of the extraction electrode 49. The condensing optical system 62, the window portion 63, and the reflecting optical system 64 correspond to the illumination optical path forming portion in the present invention. Then, the illumination light passes through the inside of the extraction electrode 49 and is incident on the surface of the sample 42 arranged below the extraction electrode 49. Further, of the illumination light, a part of the light reflected on the surface of the sample 42 is incident on the lower surface of the extraction electrode 49, passes through the inside of the extraction electrode 49, and is reflected optical provided in the vacuum chamber 41. It enters the camera 68 via the system 65, the window portion 66 provided on the wall surface of the vacuum chamber 41, and the condensing optical system 67 provided outside the vacuum chamber 41. The reflective optical system 65, the window portion 66, and the condensing optical system 67 correspond to the photographing optical path forming portion in the present invention. The image taken by the camera 68 is sent to the signal processing unit 55 and displayed on the screen of the monitor 56 connected to the signal processing unit 55.

The lead electrode 49 is made entirely of "a material having conductivity and capable of transmitting visible light", and the surface of the electrode body made of a non-conductive visible light transmitting material. A thin film made of "a material having conductivity and capable of transmitting visible light" may be formed. Examples of the latter include those in which a thin film such as ITO, zinc oxide, tin oxide, titanium oxide, graphene, or aluminum is formed on the surface of an electrode body made of glass.

As described above, in the secondary ion mass analyzer according to the present embodiment, since the extraction electrode 49 can transmit visible light, it is necessary to arrange the illumination optical system for illuminating the sample 42 and to photograph the sample surface. The arrangement of the photographing optical system is not restricted by the position and shape of the extraction electrode 49. This makes it possible to mount an illumination optical system and a photographing optical system having high optically high performance.

Although various embodiments of the present invention have been described in detail with reference to the drawings, finally, various aspects of the present invention will be described.

The mass spectrometer according to the first aspect of the present invention
A sample stage with a sample placement surface and
A plate-shaped electrode having an opening through which ions pass, which is provided at a position facing the sample placement surface and in which ions generated from a sample placed on the sample placement surface are orthogonal to the sample placement surface. With an extraction electrode that can transmit visible light,
An ion separation / detection unit that separates and detects the ions extracted by the extraction electrode according to the mass-to-charge ratio, and
A camera that photographs the surface of the sample and
It has a photographing optical path forming portion that forms an optical path such that light emitted from the sample and passing through a region other than the opening of the extraction electrode is directed toward the camera.

In the mass spectrometer of the first aspect, since the extraction electrode can transmit visible light, the arrangement of the optical system (imaging optical system) for photographing the sample surface by the camera is restricted by the position and shape of the extraction electrode. I will not receive it. As a result, it is possible to mount an optically high-performance photographing optical system, and it is possible to observe the sample surface with high optical resolution.

The mass spectrometer of the second aspect of the present invention is the mass spectrometer of the first aspect.
Further, an illumination light source that irradiates the surface of the sample with illumination light which is visible light,
An illumination optical path forming portion that forms an optical path that emits light from the illumination light source and passes through a region other than the opening of the extraction electrode toward the sample.
It has.

According to the mass spectrometer of the second aspect, the arrangement of the optical system (illumination optical system) for irradiating the sample surface with the illumination light is not restricted by the position and shape of the extraction electrode, and therefore the incident angle of the illumination light. Can be freely designed. As a result, it is possible to optimize the sample photographing by the photographing optical system.

The mass spectrometer according to the third aspect of the present invention is the mass spectrometer according to the first aspect or the second aspect.
The extraction electrode is capable of transmitting both visible light and ultraviolet light.
Furthermore, a laser light source that irradiates the surface of the sample with a laser beam that is ultraviolet light,
It has a laser optical path forming portion that forms an optical path that emits light from the laser light source and passes through a region other than the opening of the extraction electrode toward the sample.

According to the mass spectrometer of the third aspect, the arrangement of the optical system (irradiation optical system) for irradiating the sample surface with the laser beam is not restricted by the position and shape of the extraction electrode. The degree of freedom of arrangement can be increased.

11, 41 ... Vacuum chamber 12, 42 ... Sample 13, 43 ... Sample plate 14, 44 ... Sample stage 15 ... Laser light source 16, 32, 37, 62, 67 ... Condensing optical system 17, 33, 36, 63, 66 ... ... Windows 18, 34, 35, 64, 65 ... Catadioptric systems 19, 49 ... Drawer electrodes 20, 50 ... Ion passage ports 23, 53 ... Mass spectrometers 24, 54 ... Ion detectors 25, 55 ... Signal processing unit 26, 56 ... Monitor 31, 61 ... Lighting light source 38, 68 ... Camera 45 ... Ion gun

Claims (3)

A sample stage with a sample placement surface and
A plate-shaped electrode having an opening through which ions pass, which is provided at a position facing the sample placement surface and in which ions generated from a sample placed on the sample placement surface are orthogonal to the sample placement surface. With an extraction electrode that can transmit visible light,
An ion separation / detection unit that separates and detects the ions extracted by the extraction electrode according to the mass-to-charge ratio, and
A camera that photographs the surface of the sample and
A mass spectrometer having a photographing optical path forming portion that forms an optical path for light emitted from the sample and passing through a region other than the opening of the extraction electrode toward the camera. Further, an illumination light source that irradiates the surface of the sample with illumination light which is visible light,
The mass spectrometer according to claim 1, further comprising an illumination optical path forming portion that forms an optical path such that light emitted from the illumination light source and passing through a region other than the opening of the extraction electrode is directed to the sample. The extraction electrode is capable of transmitting both visible light and ultraviolet light.
Furthermore, a laser light source that irradiates the surface of the sample with a laser beam that is ultraviolet light,
The mass spectrometer according to claim 1, further comprising a laser optical path forming portion that forms an optical path that emits light from the laser light source and passes through a region other than the opening of the extraction electrode toward the sample.

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