Analysis device and analysis method

Abstract

An analysis device according to the present invention comprises an excitation source, a measuring instrument, an ultraviolet irradiation unit, an electron emitter, and a gas supply unit. The excitation source irradiates a region subject to analysis on the surface of a sample with excitation rays. The measuring instrument measures charged particles that are released from the region subject to analysis when said region is irradiated with the excitation rays. The ultraviolet irradiation unit emits ultraviolet rays. The electron emitter releases electrons toward the region subject to analysis when ultraviolet rays are incident from the ultraviolet irradiation unit. The gas supply unit supplies, to the optical path of the ultraviolet rays between the ultraviolet irradiation unit and the electron emitter, a gas composed of a substance that dissociates ions upon being irradiated with ultraviolet rays.

Description

Analytical device and analytical method

[0001] The present invention relates to an analysis device and an analysis method for analyzing the surface of an object.

[0002] In surface analysis, such as X-ray photoelectron spectroscopy, Auger electron spectroscopy, and secondary ion mass spectroscopy, an X-ray or electron beam is irradiated onto the target area on the sample surface, and charged particles such as secondary electrons and secondary ions emitted from the target area are detected. During this process, the target area becomes charged due to both the accumulation of charge from the incident charged particles and the loss of charge from the emitted secondary electrons and ions. If the sample is conductive, electrons are readily conducted, and the charge is relieved. However, if the sample is highly insulating (semiconductors, organic materials, insulators), the charge is not relieved.

[0003] If the sample charge continues without being alleviated, the surface potential of the sample will differ from the ground potential, causing the exit kinetic energy of the secondary electrons and secondary ions emitted from the sample surface to differ, or the exit kinetic energy to change continuously, making it impossible to measure the sample correctly. To solve this problem, various charging correction techniques have been developed, such as the following:

[0004] Patent Document 1 discloses a technique for uniforming the surface potential of an insulating sample by using an ion gun and an electron gun in combination and supplying positive ions from the ion gun and electrons from the electron gun. Patent Document 2 discloses a charge correction technique related to a sample stage, and Patent Documents 3 to 5 disclose charge correction techniques using an electron gun or electron beam. Patent Document 6 discloses a charge correction technique for pre-treating a sample. Patent Document 7 discloses a charge correction technique for applying a voltage to a sample stage (sample). Patent Document 8 discloses a charge correction technique using a gas ionized by ultraviolet light.

[0005] JP 10-246712 JP 52-077792 JP 03-026948 JP 07-183343 JP 2000-241371 JP 2013-195192 JP 2009-063456 JP 05-045311

[0006] However, the techniques described in Patent Documents 1 to 8 irradiate a sample with either or both of low-energy electrons (approximately 1 eV to 20 eV) and low-energy positive ions (approximately 1 eV to 200 eV). Electron guns and ion guns are used to irradiate electrons and positive ions, but if these guns are placed in a vacuum, particles and other contaminants may be generated from the hot filament, making it difficult to keep the sample surface clean.

[0007] In view of the above circumstances, an object of the present invention is to provide an analytical device and an analytical method suitable for correcting the charge on a sample surface in a vacuum.

[0008] In order to achieve the above object, an analytical device according to one aspect of the present invention comprises an excitation radiation source, a measuring device, an ultraviolet ray irradiation unit, an electron emitter, and a gas supply unit. The excitation radiation source irradiates an analysis target region on a sample surface with excitation rays. The measuring device measures charged particles emitted from the analysis target region by irradiation with the excitation rays. The ultraviolet ray irradiation unit emits ultraviolet rays. When ultraviolet rays are incident on the electron emitter from the ultraviolet ray irradiation unit, the electron emitter emits electrons toward the analysis target region. The gas supply unit supplies a gas consisting of a substance that undergoes ion dissociation when irradiated with ultraviolet rays, onto the optical path of the ultraviolet rays, between the ultraviolet ray emission unit and the electron emitter.

[0009] The electron emitter may be at a negative potential with respect to the sample.

[0010] The electron emitter may be a plate arranged so that the analysis target region is positioned in the normal direction.

[0011] The electron emitter may be a metal plate.

[0012] The sample and the electron emitter may be placed in a vacuum chamber, and the ultraviolet irradiation unit may include an ultraviolet light source placed outside the vacuum chamber, and an optical system placed in the vacuum chamber that causes ultraviolet light emitted from the ultraviolet light source to be incident on the electron emitter.

[0013] The optical system may include a light collector having a mirror-finished inner circumferential surface and a tapered tube shape whose inner diameter gradually decreases from the ultraviolet light source side.

[0014] The ultraviolet light may be vacuum ultraviolet light.

[0015] The excitation source may be an X-ray source, and the measuring device may measure the kinetic energy of electrons emitted from the region to be analyzed.

[0016] The analysis device may further include a shielding mechanism capable of blocking the optical path of the ultraviolet light.

[0017] In order to achieve the above object, an analytical method according to one embodiment of the present invention includes irradiating an analysis target area on a sample surface with an excitation beam, measuring charged particles emitted from the analysis target area, irradiating an electron emitter with ultraviolet light, and causing the electrons emitted from the electron emitter to be emitted toward the analysis target area, and supplying a gas consisting of a substance that undergoes ion dissociation when irradiated with ultraviolet light onto the optical path of the ultraviolet light.

[0018] As described above, according to the present invention, it is possible to provide an analytical device and analytical method suitable for correcting the charge on a sample surface in a vacuum.

[0019] It is a schematic diagram of an analysis device according to an embodiment of the present invention. It is a schematic diagram of a partial configuration of the analysis device. It is a schematic diagram showing the operation of the analysis device. It is a schematic diagram showing the operation of the analysis device.

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] [Configuration of the Analysis Apparatus] The analysis apparatus according to this embodiment will be described. Fig. 1 is a schematic diagram of an analysis apparatus 100 according to this embodiment, and Fig. 2 is a schematic diagram of a portion of the configuration of the analysis apparatus 100. The analysis apparatus 100 is an apparatus that performs X-ray photoelectron spectroscopy (XPS).

[0022] 1, the analytical device 100 includes a vacuum chamber 101, an excitation radiation source 102, a measuring instrument 103, an ultraviolet irradiation unit 104, an electron emitter 105, and a gas supply unit 106. A sample S is placed in the vacuum chamber 101. The sample S is, for example, a silicon wafer.

[0023] The vacuum chamber 101 is connected to a vacuum exhaust means (not shown) and maintains the interior in a vacuum environment. The excitation radiation source 102 is disposed in the vacuum chamber 101 and irradiates the sample S with X-rays. FIG. 3 is a schematic diagram of the sample S being irradiated with X-rays. As shown in the figure, X-rays (in the figure, "X-ray") are irradiated from the excitation radiation source 102 onto a partial region of the surface of the sample S. Hereinafter, the region of the surface of the sample S that is irradiated with X-rays will be referred to as the analysis target region R. Electrons (in the figure, "e － ") is released.

[0024] The measuring device 103 is placed in the vacuum chamber 101 and measures electrons (indicated by "e 1" in FIG. 1) emitted from the analysis target region R by irradiation with X-rays. － The measuring device 103 is, for example, an electron spectrometer.

[0025] The ultraviolet irradiating unit 104 irradiates the electron emitter 105 with ultraviolet rays. The ultraviolet irradiating unit 104 includes an ultraviolet light source 111, a window member 112, and an optical system 113. The ultraviolet light source 111 is disposed outside the vacuum chamber 101 and emits ultraviolet rays. The ultraviolet rays emitted by the ultraviolet light source 111 are preferably vacuum ultraviolet rays (having a wavelength of 10 nm or more and 200 nm or less).

[0026] The window member 112 is disposed between the ultraviolet light source 111 and the optical system 113, constitutes the outer wall of the vacuum chamber 101, and transmits ultraviolet light. The window member 112 is preferably made of a material with high ultraviolet transmittance, such as magnesium fluoride or calcium fluoride.

[0027] The optical system 113 is disposed inside the vacuum chamber 101 and causes ultraviolet light emitted from the ultraviolet light source 111 to be incident on the electron emitter 105. Specifically, the optical system 113 includes a collector 114 and a reflector 115. The collector 114 has a tapered tube shape with an inner diameter gradually decreasing from the ultraviolet light source 111 side. The inner surface of the tapered tube is mirror-finished (shape accuracy of 0.2 μm or less, surface roughness Ra of 50 nm or less), and as shown in FIG. 2 , ultraviolet light ("UV" in the drawing) emitted from the ultraviolet light source 111 is reflected by the inner surface and collected. The inner surface of the tapered tube is preferably made of a metal with high ultraviolet reflectivity, such as aluminum.

[0028] The reflector 115 reflects the ultraviolet light collected by the light collector 114 toward the electron emitter 105. The reflector 115 is, for example, a metal plate, and is preferably made of a material with high ultraviolet reflectivity, such as aluminum. The reflector 115 may be a flat plate, or may be a parabolic surface to achieve a light collecting effect.

[0029] As described above, the optical system 113 causes the ultraviolet light emitted from the ultraviolet light source 111 to be incident on the electron emitter 105. The optical path of the ultraviolet light can be parallel to the surface of the sample S, as shown in FIG. 2 . The configuration of the optical system 113 is not limited to that shown here, and any configuration may be used as long as it is capable of causing the ultraviolet light emitted from the ultraviolet light source 111 to be incident on the electron emitter 105. For example, the optical system 113 may include two or more reflectors 115. Alternatively, the optical system 113 may not include the reflector 115, and the ultraviolet light collected by the collector 114 may be directly incident on the electron emitter 105. Furthermore, instead of the collector 114, an optical lens made of a material with high ultraviolet transmittance, such as magnesium fluoride or calcium fluoride, may be used. Note that optical lenses vary in transmittance and refractive index for the wavelength of vacuum ultraviolet light, so it is preferable to use a collector 114 with a polished surface with high ultraviolet reflectance, such as aluminum. Furthermore, using a surface roughness Ra of 50 nm at a wavelength of approximately λ / 4 is more preferable because it allows for more intense ultraviolet light to be obtained.

[0030] When ultraviolet light is incident on the electron emitter 105 from the ultraviolet light irradiation unit 104, the electron emitter 105 emits electrons toward the analysis target region R. FIG. 4 is a schematic diagram showing electrons emitted from the electron emitter 105. As shown in the figure, when ultraviolet light ("UV" in the figure) is incident on the electron emitter 105, electrons ("e" in the figure) are emitted from the surface of the electron emitter 105. － The electron emitter 105 is made of a material that emits electrons when exposed to ultraviolet light, such as titanium (Ti) or gold (Au).

[0031] The electron emitter 105 is in the form of a flat plate or a paraboloid centered on the irradiated sample point, and is supported so that the analysis target region R is located in the normal direction ("H" in the figure). The electron emitter 105 is preferably positioned close to the analysis target region R but at a location that does not impair the performance of the excitation radiation source 102 and the measuring instrument 103. The electron emitter 105 is also connected to a power supply (not shown), and is switched to and maintained at a negative potential, ground, or positive potential with respect to the sample S. This switching is intended to control the surface potential of the sample by applying negative kinetic energy to the electron emission (negative potential), not applying kinetic energy to the electron emission (ground), or suppressing electron emission and preventing emission (positive potential).

[0032] 4, the gas supply unit 106 supplies a gas ("Gas" in the drawing) onto the optical path of the ultraviolet light between the ultraviolet light irradiation unit 104 and the electron emitter 105. This gas is made of a substance that is ionized by ultraviolet light irradiation, such as nitrogen (N ２ ), oxygen (O ２ ), argon (Ar), or xenon (Xe). When the gas is irradiated with ultraviolet light, the gas is ionized and dissociated into ions (in the figure, "M ＋ Specifically, nitrogen molecular ions (N ２ ＋ ), oxygen molecular ions (O ２ ＋ ), argon ions (Ar ＋ ) or xenon ions (Xe ＋ ) etc.

[0033] The analytical device 100 has the above-described configuration. The analytical device 100 may have other configurations that are alternatives to or additional to the above-described configurations.

[0034] [Operation of the Analysis Apparatus] As described above, in the analysis apparatus 100, X-rays are irradiated from the excitation radiation source 102 onto the analysis target region R of the sample S (see FIG. 3), and electrons (in FIG. 3, "e －The kinetic energy of the electrons emitted from the analysis region R is measured by the measuring device 103. At this time, the analysis region R loses charge due to the emitted electrons, so the analysis region R becomes positively charged. If the sample S is an insulating material, the charge is not alleviated, and the movement of the electrons emitted from the analysis region R is affected, making it impossible to perform accurate measurements.

[0035] In the analysis device 100, ultraviolet rays are irradiated from the ultraviolet irradiating unit 104 to the electron emitter 105 in conjunction with the X-ray irradiation (see FIG. 4). This ultraviolet irradiation causes electrons ("e 105" in FIG. 4) to be emitted from the electron emitter. － ") are released and supplied to the analysis target region R. The electrons eliminate the positive charge of the analysis target region R.

[0036] On the other hand, there is a risk that the electrons supplied from the electron emitter 105 will be excessive, causing the analysis target region R to be negatively charged. To cope with this, in the analysis device 100, a gas is supplied into the optical path of the ultraviolet light by the gas supply unit 106 (see FIG. 4). This gas is ionized by irradiation with ultraviolet light, and becomes positive ions ("M" in FIG. 4). ＋ If the analysis region R is negatively charged, positive ions are attracted to the analysis region R, and the negative charge of the analysis region R is eliminated. In this way, the charge of the analysis region R is eliminated, and the influence of the charge of the analysis region R on the measurement is prevented.

[0037] The potential of the sample S may be kept insulated from the ground potential, or a potential may be applied in the range of negative potential (-20 V) to positive potential (+20 V) with respect to the ground potential. This can be changed depending on the insulating properties of the sample S, but it is necessary to keep the potential of the sample S constant during measurement. The potential of the electron emitter 105 is a negative potential relative to the potential of the sample S, and is preferably in the range of -1 V to -50 V with respect to the ground potential.

[0038] By making the potential of the electron emitter 105 more negative than the potential of the sample S, electrons (indicated by "e － ") advances toward the sample S. The potential of the electron emitter 105 is optimized depending on the arrangement of the electron emitter 105 and the degree of charging of the region R to be analyzed.

[0039] [Effects of the Analysis Apparatus] As described above, the analysis apparatus 100 supplies electrons generated by irradiating the electron emitter 105 with ultraviolet light to the analysis target region R, and supplies positive ions generated by irradiating the gas with ultraviolet light to the analysis target region R, thereby eliminating the charge on the analysis target region R. With this method, the amount of electrons and positive ions supplied can be adjusted by the potential of the electron emitter 105 and the flow rate of gas supplied from the gas supply unit 106, thereby making it possible to accurately and quickly eliminate the charge on the sample S. Furthermore, because the sample S is not directly irradiated with ultraviolet light, damage to the sample S due to the ultraviolet light is prevented.

[0040] Furthermore, the ultraviolet irradiation unit 104 can be configured with the ultraviolet light source 111 outside the vacuum chamber 101 and the optical system 113 inside the vacuum chamber 101. This eliminates the need to place an expensive electron gun or ion gun inside the vacuum. Electron guns and ion guns require thermal filaments, which can cause problems such as heat generation, dust generation, and gas desorption, as well as a lack of stability. Furthermore, thermal filaments have a limited lifespan, making it necessary to open the vacuum chamber 101 and replace the expensive filament each time, and also requiring a period of thermal stabilization upon startup. On the other hand, these problems do not occur with the analytical device 100.

[0041] In addition, the analytical device 100 has a relatively simple configuration, is inexpensive, and is easy to maintain because ultraviolet light can be irradiated from outside the vacuum. Furthermore, no components requiring short-term maintenance are placed inside the vacuum chamber 101. Therefore, the analytical device 100 has a configuration suitable for correcting the charge on the sample surface in a vacuum.

[0042] [Other Configurations] In addition to the above configuration, the analytical device 100 may also include a shielding mechanism. The shielding mechanism is a mechanism capable of shielding the optical path of ultraviolet light between the ultraviolet irradiation unit 104 and the electron emitter 105, and shields the optical path of ultraviolet light when charge correction of the sample surface is not required, thereby stopping the supply of electrons and positive ions to the sample surface. The specific configuration of the shielding mechanism is not particularly limited, and may include a mechanism for opening and closing a shutter. This configuration allows charge correction to be stopped and resumed more quickly than by controlling the light emission of the ultraviolet light source 111.

[0043] [Application to Other Analytical Devices] Although the analytical device 100 has been described as an X-ray electron spectrometer, it may be another type of analytical device as long as the excitation radiation source 102 is capable of irradiating an analysis target region R of the sample S with excitation radiation and the measuring device 103 is capable of measuring charged particles emitted from the analysis target region R by irradiation with the excitation radiation. Specifically, the analytical device 100 may be an analytical device that uses Auger electron spectroscopy or secondary ion mass spectroscopy.

[0044] In the case of Auger electron spectroscopy, the excitation radiation source 102 irradiates the analysis target region R with an electron beam, and the measuring instrument 103 measures the kinetic energy of the Auger electrons emitted from the analysis target region R. In the case of secondary ion mass spectroscopy, the excitation radiation source 102 irradiates the analysis target region R with primary ions, and the measuring instrument 103 measures the mass of the secondary ions emitted from the analysis target region R. The configuration other than the excitation radiation source 102 and the measuring instrument 103 is the same as that described above. In Auger electron spectroscopy and secondary ion mass spectroscopy, the analysis target region R is charged due to the emission of charged particles, but the charging can be corrected by the analyzing device 100 as described above.

[0045] [Regarding the embodiments of the present invention] Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-described embodiments and various modifications can be made. Of the characteristic features described in the above-described embodiments, at least two of the characteristic features can be arbitrarily combined.

[0046] REFERENCE SIGNS LIST 100: Analysis device 101: Vacuum chamber 102: Excitation radiation source 103: Measuring instrument 104: Ultraviolet irradiation unit 105: Electron emitter 106: Gas supply unit 111: Ultraviolet light source 112: Window member 113: Optical system 114: Light collector 115: Reflector

Claims

1. An analytical device comprising: an excitation ray source that irradiates an analysis target region on a sample surface with excitation rays; a measuring device that measures charged particles emitted from the analysis target region by the irradiation of the excitation rays; an ultraviolet ray irradiation unit that emits ultraviolet rays; an electron emitter that emits electrons toward the analysis target region when ultraviolet rays are incident from the ultraviolet ray irradiation unit; and a gas supply unit that supplies a gas consisting of a substance that undergoes ion dissociation when irradiated with ultraviolet rays onto the optical path of the ultraviolet rays between the ultraviolet ray emission unit and the electron emitter.

2. An analytical device according to claim 1, wherein the electron emitter is at a negative potential with respect to the sample.

3. An analytical device according to claim 1, wherein the electron emitter is a plate arranged so that the region to be analyzed is positioned in the normal direction.

4. An analyzer according to claim 1, wherein the electron emitter is a metal plate.

5. An analytical device according to claim 1, wherein the sample and the electron emitter are placed in a vacuum chamber, and the ultraviolet irradiation unit comprises an ultraviolet light source placed outside the vacuum chamber, and an optical system placed inside the vacuum chamber for making the ultraviolet light emitted from the ultraviolet light source incident on the electron emitter.

6. An analytical device according to claim 1, wherein the optical system comprises a light collector having a mirror-finished inner surface and a tapered tube shape whose inner diameter gradually decreases from the ultraviolet light source side.

7. An analytical device according to claim 1, wherein the ultraviolet light is vacuum ultraviolet light.

8. An analytical apparatus according to claim 1, wherein the excitation source is an X-ray source, and the measuring device measures the kinetic energy of electrons emitted from the region to be analyzed.

9. An analytical device according to claim 1, further comprising a shielding mechanism capable of blocking the optical path of the ultraviolet light.

10. An analytical method comprising: irradiating an analysis target area on a sample surface with an excitation beam; measuring charged particles emitted from the analysis target area; irradiating an electron emitter with ultraviolet light; causing electrons emitted from the electron emitter to be emitted toward the analysis target area; and supplying a gas consisting of a substance that undergoes ion dissociation when irradiated with ultraviolet light onto the optical path of the ultraviolet light.

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