JP6039497B2 - Semiconductive ceramic and method for producing semiconductive ceramic - Google Patents

Description

  The present invention relates to a semiconductive ceramic containing aluminum nitride as a main component and a method for producing the semiconductive ceramic.

  For example, an electron accelerator tube used for an electron microscope device, an electrostatic deflector, an insulator for an X-ray tube used for an X-ray irradiation device, and the like are provided with a plurality of electrodes made of metal on the surface of a ceramic body. A ceramic member with an electrode is used. A relatively high voltage is applied between the plurality of electrodes in the electrode-attached ceramic member. When a relatively high voltage is applied between the plurality of electrodes, charge accumulation (charge-up) may occur on the surface of the ceramic between the electrodes. If the amount of the charged up charge becomes too large, a large current is generated due to an electronic avalanche in which the accumulated charge flows out at a stretch, which may lead to malfunction or damage of the deflector.

For example, in Patent Document 1 below, as a ceramic member with an electrode suitable for an electrostatic deflector, a ceramic member with an electrode using a semiconductive ceramic that can reduce charge accumulation (charge-up) that occurs between electrodes is disclosed. Proposed. In Patent Document 1, as a ceramic used for an electrode-equipped ceramic member suitable for an electrostatic deflector, titanium (Ti) is contained in alumina (Al ₂ O ₃ ) as a main component, and the surface resistivity is 1 × 10 ^10. Semiconductive ceramics of the order of (Ω / □) have been proposed.

Japanese Patent Laid-Open No. 2005-190853

  In recent years, miniaturization of electron microscope devices, X-ray emission devices, and the like has progressed, and ceramic members with electrodes used in these devices have also been miniaturized. As these devices are miniaturized, the distance between the ceramic member with an electrode and the heat source in the device becomes closer, and the thermal energy flowing into the ceramic member with an electrode becomes larger. For example, alumina has a relatively low thermal conductivity of 28 to 38 (W / m · K) and a specific heat of 0.75 to 0.8 (W / m · K), which is described in Patent Document 1. In the semiconductive ceramic mainly composed of alumina, a relatively large amount of inflowing thermal energy is easily stored in the semiconductive ceramic. That is, in the ceramic member with an electrode using the semiconductive ceramic mainly composed of alumina described in Patent Document 1, the temperature of the ceramic member with an electrode tends to be excessively increased as the apparatus is downsized.

  If the device is continuously used in a state where the temperature of the ceramic member with electrode is likely to rise excessively, the semiconductive ceramic itself may crack or chip due to thermal expansion and contraction of the semiconductive ceramic, Due to the difference in thermal expansion between the ceramic and the ceramic, there is a problem that the electrode is easily peeled off from the semiconductive ceramic. The present invention has been made to solve such problems.

The present invention contains aluminum nitride as a main component and at least carbon, and the peak of the C _1S spectrum by X-ray photoelectron spectroscopy when the inner region is irradiated with X-rays is C _1S A, and the surface region has X A half-width of C _1S B is smaller than a half-width of C _1S A, where C _1S B is a peak of C _1S spectrum by X-ray photoelectron spectroscopy at the time of irradiation with X-rays. Provide conductive ceramics.

Also, a method for producing a semiconductive ceramic mainly composed of aluminum nitride, in which a ceramic mainly composed of aluminum nitride and a carbon-containing member mainly composed of carbon are disposed in a chamber of a heating device. Then, the inside of the chamber is evacuated and the inside of the chamber is heated to 600 ° C. to 1000 ° C. to heat the ceramics, whereby C _1S by X-ray photoelectron spectroscopy analysis when X-rays are irradiated to the internal region. the peak of the spectrum and C _1S a, when a peak of C _1S spectrum by X-ray photoelectron spectroscopy when irradiated with X-rays in the surface region was C _1S B, the half-width of the C _1S B is the C _1S a A semiconductive ceramic production method characterized by obtaining a semiconductive ceramic whose main crystal is aluminum nitride, which is smaller than the half-value width of Provide.

  The semiconductive ceramic of the present invention is less likely to accumulate relatively large charges on the surface, has a relatively high thermal conductivity, and does not easily rise in temperature. According to the method for producing a semiconductive ceramic of the present invention, it is possible to produce a semiconductive ceramic in which a large charge is difficult to accumulate on the surface and the heat conductivity is relatively high and the temperature is hardly raised.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining the ceramic member with an electrode comprised by providing one Embodiment of the semiconductive ceramic of this invention, Fig.1 (a) is a schematic perspective view, FIG.1 (b) is a schematic sectional drawing. is there. The example of the _C1S spectrum by X-ray photoelectron spectroscopy analysis at the time of irradiating X-rays to the semiconductive ceramics shown in FIG. 1 is shown. It is a schematic block diagram of the electron beam irradiation apparatus comprised including the ceramic member with an electrode shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a view for explaining an electrode-attached ceramic member 10 (hereinafter also simply referred to as a ceramic member 10) configured to include a semiconductive ceramic 12 which is an embodiment of the semiconductive ceramic of the present invention. 1 (a) is a schematic perspective view of the ceramic member 10, and FIG. 1 (b) is a schematic cross-sectional view of the ceramic member 10.

The ceramic member 10 of this embodiment includes a semiconductive ceramic 12, a bonding layer 18a and 18b made of a metal to be provided on the surface of the semiconductive ceramic 12, and a bonding layer 18a.
And 18b and electrodes 14a and 14b joined to the ceramic body 12. The ceramic member 10 is provided with a through-hole 11 that allows the semiconductive ceramic 12 to communicate with the electrode 14a and the electrode 14b.

The semiconductive ceramic 12 contains aluminum nitride (AlN) as a main component and at least carbon (C), and the peak of the C _1S spectrum by X-ray photoelectron spectroscopy when the internal region 12A is irradiated with X-rays. was the C _1S a, when a peak of C _1S spectrum by X-ray photoelectron spectroscopy when irradiated with X-rays in the surface region 12B was C _1S B, the half-width of the _{C 1S B (FWHM: full width} at half maximum ) Is smaller than the half width of C _1S A. The inner region 12A of the semiconductive ceramic 12 refers to a region that is separated from the surface of the semiconductive ceramic 12 by 10 μm or more toward the inside.

The peak of the C _1S spectrum by X-ray photoelectron spectroscopy when the semiconductive ceramic 12 is irradiated with X-rays can be measured using an X-ray photoelectron spectrometer. Specifically, for example, in Quantum 2000 manufactured by ULVAC-PHI, monochrome AlKα is used as the X-ray source, the X-ray output is 4.5 W · 15 kV, and the pass energy is 214.
It can be measured by setting 0.00eV and Step size 0.125eV.

The half-value width of the peak C _1S B of C _1S spectrum by X-ray photoelectron spectroscopy when irradiated with X-rays in the surface region 12B is, C _1S spectrum by X-ray photoelectron spectroscopy when irradiated with X-rays in the interior region 12A small and as compared with the half-width of the peak C _1S a, and the half width of the peak C _1S B is smaller than the half-value width of the peak C _1S a, the half-width of the C _1S B spectra of C _1S a spectrum It is smaller than the half-value width.

The half width of the peak C _1S B being smaller than the half width of the peak C _1S A preferably means that the half width of the peak C _1S B is less than 90% of the half width of the peak C _1S A. Preferably, the half width of the peak C _1S B is less than 80% of the half width of the peak C _1S A.

The semiconductive ceramic 12 will be described in more detail. It is considered that the peak of the C _1S spectrum of the semiconductive ceramic 12 mainly corresponds to the chemical bonding state of carbon dissolved in the crystal of aluminum nitride which is the main component. It is considered that the solid solution of carbon in the aluminum nitride crystal is mainly caused by the solid solution of carbon ions to the nitrogen ion site of the aluminum nitride crystal.

Half-value width of the peak of C _1S spectrum varies depending on the steepness of the peak of C _1S spectrum, a peak of C _1S spectrum is considered the density of carbon in solid solution becomes steep than higher. Half-width of the C peak of _1S spectrum C _1S B by X-ray photoelectron spectroscopy when irradiated with X-rays in the surface region, C _1S peak of spectrum by X-ray photoelectron spectroscopy when irradiated with X-rays in the interior region In the semiconductive ceramic 12 that is smaller than the half width of C _1S A, the surface region 12B of the semiconductive ceramic 12 is a unit of carbon ions dissolved in the surface region 12B of the semiconductive ceramic 12 compared to the inner region 12A of the semiconductive ceramic 12. The number per volume is thought to be large. Such a semiconductive ceramic 12 has a surface resistivity of 1 × 10 ⁶ to 1 × 10 ⁹ (Ω / □) and 1 × 10 which is a surface resistivity of a ceramic mainly composed of general aluminum nitride. ^It is lower than ¹¹ (Ω / □). For this reason, the semiconductive ceramic 12 is relatively difficult to accumulate charges on the surface. Aluminum nitride has a relatively high thermal conductivity of 150 to 170 (W / m · K) and a specific heat of 0.71 to 0.74 (W / m · K). For this reason, the temperature of the semiconductive ceramic 12 is unlikely to rise even when it is close to a heat source. The surface resistivity can be measured by a method based on, for example, JIS K6271, which is called a so-called double ring electrode method.

  Although the exact crystalline state of aluminum nitride when carbon ions are dissolved in aluminum nitride crystals is not clear, it is assumed that holes or free electrons are newly generated as carbon ions are dissolved. be able to. The semiconductive ceramic 12 having the surface region 12B having a relatively large number of carbon ions per unit volume has a relatively low surface resistivity and a relatively large charge because the surface region 12B has a relatively large number of holes or free electrons. Is difficult to accumulate on the surface.

FIG. 2 shows an example of a spectrum obtained by X-ray photoelectron spectroscopy when the semiconductive ceramic 12 is irradiated with X-rays, and C obtained by X-ray photoelectron spectroscopy when the surface region 12B is irradiated with X-rays. and peak C _1S B of _1S spectrum shows superimposed normalized the C _1S spectrum by X-ray photoelectron spectroscopy when irradiated with X-rays in the inner region 12A and a peak C _1S a at the same height, respectively . The peak of the C _1S spectrum of aluminum nitride is the Binding En
It is known that the energy appears at a position of about 284.5 eV. In the example shown in FIG.
The steep peak where inding energy appears at a position of about 284.8 eV is the peak of the C _1S spectrum of aluminum nitride.

In the example shown in FIG. 2, the full width at half maximum of the peak C _1S B is about 75% of the full width at half maximum of the peak C _1S A. In the example of the semiconductive ceramic 12 shown in FIG. 2, the surface resistivity is 1 × 10 ⁶ to 1 × 10 ⁹ (Ω / □), which is the surface resistivity of a general ceramic mainly composed of aluminum nitride. It was lower than 1 × 10 ¹¹ (Ω / □). On the other hand, after removing the surface of the semiconductive ceramic 12 of the example shown in FIG. 2 by about 10 μm using, for example, a sand blast apparatus, the surface resistivity of the surface after the removal is measured, the surface resistivity is 1 × 10 ¹¹ ( Ω / □) and the surface resistivity of general aluminum nitride. As described above, the semiconductive ceramic 12 has the internal region 12A having a relatively small amount of carbon in a solid solution and a relatively high surface resistivity. Therefore, the volume specific resistance as an overall electric resistance value is 1. Since the surface region 12B has a relatively high amount of carbon in a solid solution while having a relatively high insulation property of about × 10 ¹⁴ (Ωcm), the surface charge is excessively accumulated (charge-up). And the generation of a large current due to an electronic avalanche can be suppressed.

  The bonding layers 18a and 18b are made of, for example, a metal layer in which an Ag—Cu—Ti brazing material layer and a Ni plating layer are laminated. The electrodes 14a and 14b are made of gold, copper, Kovar, or the like, the electrode 14a is joined to the semiconductive ceramic 12 via the joining layer 18a, and the electrode 14b is joined to the semiconductive ceramic 12 via the joining layer 18b. Yes. The configuration and material of the bonding layers 18a and 18b and the electrodes 14a and 14b are not particularly limited.

  FIG. 3 is a schematic configuration diagram of an electron beam irradiation apparatus 100 (hereinafter simply referred to as the apparatus 100) configured to include the ceramic member 10 shown in FIG. As shown in FIG. 3, an apparatus 100 includes an electron beam source 101 for emitting electrons E, a ceramic member 10 for accelerating the electrons E emitted from the electron beam source 101, and a metal that is a so-called vacuum chamber. A container 103, an electron beam source power source 105 connected to the electron beam source 101, and an acceleration power source 106 connected to the ceramic member 10. At least a part of the electron beam source 101 and the ceramic member 10 is disposed inside the container 103. An object P placed on the stage S is disposed at a position where the electrons E inside the container 103 reach. One electrode 14 a of the ceramic member 10 is electrically and thermally connected to the container 103.

  The electron beam source 101 includes a cathode 107 and a heating filament 109 for heating the cathode 107. The heating filament 109 is connected to the electron beam source electrode 105 through a conductive wire, and the cathode 107 is supported by the heating filament 109. The heating filament 109 is a hot filament mainly composed of copper or tungsten, and the temperature rises when a voltage is applied by the electron beam source electrode 105 and a current flows. The cathode 107 is a member having a small radius of curvature at the tip (lower tip in FIG. 3) made of tungsten, lanthanum hexaboride, carbon nanotubes, etc., and receives the thermal energy of the heated heating filament 109 to raise the temperature. Then, electrons E are emitted from the tip portion having a small curvature radius. A part of the heating filament 109 on the lower side in FIG. 3 and the cathode 107 are disposed in the through hole 11 of the ceramic member 10.

  A relatively high voltage of about 1 to 100 (kV) is applied between the electrodes 14 a and 14 b of the ceramic member 10 by the acceleration power source 106. The electrons E emitted from the cathode 107 are accelerated toward the lower side in FIG. 3 by the voltage between the electrodes 14a and 14b, and are irradiated onto the object P.

The semiconductive ceramic 12 has a relatively low surface resistivity of 1 × 10 ⁶ to 1 × 10 ⁹ (Ω / □). For this reason, even when a relatively high voltage is applied between the electrode 14a and the electrode 14b, the accumulated charge is semiconductive before an excessively large amount of charge is accumulated on the surface of the semiconductive ceramic 12. It flows on the surface of the ceramic 12 and reaches the electrode 14a or the electrode 14b. The reached electric charge escapes from the ceramic member 10 through the container 103 and the conductive wire through the electrode 14a or the electrode 14b. When the ceramic member 10 including the semiconductive ceramic 12 is used as an electron accelerating tube in this way, the charge-up on the surface of the semiconductive ceramic 12 can be suppressed, and thus an excessive current generated with the charge-up. Can be suppressed.

  In the electron beam irradiation apparatus 100, a part of the heating filament 109 is disposed in the through hole 11 of the ceramic member 10, and the semiconductive ceramic 12 has thermal energy radiated from the heating filament 109 that is a heat source. A lot of reach. Since the semiconductive ceramic 12 mainly composed of aluminum nitride has a relatively small specific heat of 0.71 to 0.74 (W / m · K), the temperature hardly rises even when the thermal energy reaches. Since the thermal conductivity is relatively high at 150 to 170 (W / m · K), the reached thermal energy easily flows to the container 103 through the electrode 14 a thermally connected to the container 103. Thus, the temperature of the semiconductive ceramic 12 mainly composed of aluminum nitride is relatively difficult to increase. For this reason, even when the semiconductive ceramics 12 are arranged close to the heating filament 109 that is a heat source as in the apparatus 100, the semiconductive ceramics 12 are hardly cracked or chipped due to thermal expansion and contraction. The peeling of the metal bodies 14a and 14b from the semiconductive ceramic 12 due to the difference in the degree of thermal expansion between the 14a and the electrode 14b and the semiconductive ceramic 12 is also suppressed. Thus, the device 100 including the ceramic member 10 ensures high operational reliability even when the ceramic member 10 and the heating filament 109 are sufficiently close to each other. In other words, when the ceramic member 10 is used, the ceramic member 10 and the heating filament 109 can be sufficiently brought close to each other, so that the apparatus 100 can be sufficiently downsized.

  Such an apparatus 100 can be used, for example, as an electron gun in an electron microscope apparatus or an electron gun in an electron beam exposure apparatus. In addition, since the semiconductive ceramic of the present invention suppresses the surface charge-up and does not easily generate a large current due to the charge-up, the insulator for the X-ray tube, the SEM lens unit for the TEM acceleration tube, and the vacuum switch application It can be suitably used for applications where a relatively high voltage is applied. The shape and application of the semiconductive ceramic of the present invention are not particularly limited.

  For example, the semiconductive ceramic of the present invention is evacuated in a state where a ceramic containing aluminum nitride as a main component and a carbon-containing member containing carbon as a main component are arranged in a chamber of a heating device. At the same time, the temperature inside the chamber can be raised to 600 ° C. to 1000 ° C., and the aluminum nitride ceramics can be heated. Hereinafter, an embodiment of a method for producing a semiconductive ceramic according to the present invention will be described.

  First, ceramics (aluminum nitride ceramics) whose main component is aluminum nitride is manufactured. For example, a mixed powder composed of 94% by mass of aluminum nitride powder having a particle size of 1 to 2 μm and 6% by mass of a powder of rare earth element oxide such as erbium (Er) is used as a starting material. Ethanol is added and mixed to produce a slurry, and the resulting slurry is spray-dried, and the granules are CIP-molded (cold isostatic pressing), and the resulting molded body is cut to form a cylindrical shape Create a body.

Subsequently, the cylindrical shaped body is degreased by heat treatment in nitrogen gas at 700 ° C. for about 3 hours, and then fired in nitrogen gas at 1750 ° C. for 5 hours to obtain a cylindrical aluminum nitride ceramic. . The obtained aluminum nitride ceramic has, for example, a surface resistivity of about 1 × 10 ¹¹ (Ω / □). In the obtained aluminum nitride ceramic, a composite oxide containing a rare earth element (for example, erbium) and aluminum is present at the grain boundary of particles mainly composed of aluminum nitride.

Subsequently, the aluminum nitride ceramic thus obtained and the carbon-containing member containing carbon as a main component are disposed in the chamber of the heating device, and the inside of the chamber is evacuated and the aluminum nitride ceramic is 600. The temperature is raised to 1000C to 1000C. In this embodiment, a vacuum heating furnace having a resistance heating type infrared heater is used as a heating device. For example, this aluminum nitride ceramic is placed on a stage member containing 90% by mass or more of carbon, and this stage member At the same time, the aluminum nitride ceramic is heated. Specifically, for example, in a state where the inside of the chamber of the vacuum heating furnace is evacuated to 1.0 × 10 ⁻⁵ Pa or less, a current is applied to the resistance heating heater disposed in the chamber, The aluminum nitride ceramic is heated to 600 ° C. to 1000 ° C. together with the stage member, and maintained at 600 ° C. to 1000 ° C. for about 15 minutes. In addition, the carbon containing member which has carbon as a main component may be a protective member etc. for protecting the heater part in a heating apparatus, for example, and is not specifically limited.

During the heat treatment at 600 ° C. to 1000 ° C., the inside of the chamber is evacuated, and carbon is released as outgas from a carbon-containing member containing carbon as a main component. That is, during the heat treatment at 600 ° C. to 1000 ° C., many carbon atoms are floating near the surface of the aluminum nitride ceramics, and these carbon atoms collide with the aluminum nitride ceramics. The carbon atoms that collide with the aluminum nitride ceramics are dissolved in the aluminum nitride crystal as the main component as described above. That is, many carbon atoms are dissolved in the surface region of the aluminum nitride ceramic. As a result, the semiconductive ceramic having a larger number of carbon ions per unit volume in the surface region than in the internal region, that is, the half width of the peak C _1S B is larger than the half width of the peak C _1S A. Small semiconductive ceramics can be obtained. The surface resistivity of the semiconductive ceramic 12 thus obtained is about 1 × 10 ⁶ to 1 × 10 ⁹ (Ω / □). It was found for the first time as a result of trial and error experiments by the present inventor that the surface resistivity of aluminum nitride ceramics can be reduced by such a heat treatment by dissolving carbon on the surface of the aluminum nitride ceramics. Is.

In the above embodiment, the surface resistivity of the obtained semiconductive ceramic 12 was about 1 × 10 ⁶ to 1 × 10 ⁹ (Ω / □), but the temperature and time of heat treatment, the number of heat treatments, etc. were adjusted. By doing so, it is possible to obtain a semiconductive ceramic having a surface resistivity of less than 1 × 10 ⁶ (Ω / □), a semiconductive ceramic having a surface resistivity of greater than 1 × 10 ⁹ (Ω / □), and the like. .

  For example, by adjusting the atmosphere and temperature range in the metalizing process and the plating process when forming the bonding layers 18a and 18b and the electrodes 14a and 14b on the surface of the semiconductive ceramic 12, the semiconductive ceramic 12 The surface resistivity can be further reduced. Specifically, in the metallizing process and the plating process, the semiconductive ceramic 12 and the carbon-containing member containing carbon as a main component are placed in a chamber of a heating device, and the inside of the chamber is evacuated and 600 ° C. By raising the temperature to ˜1000 ° C. and performing a metallizing process and a plating process, carbon is further dissolved in the surface region of the semiconductive ceramic 12 to further reduce the surface resistivity of the semiconductive ceramic 12. It is also possible.

  Conversely, for example, by partially removing the surface region 12B of the semiconductive ceramic 12 from the surface side by blasting or the like, the amount of carbon dissolved in the surface region 12B is reduced, and the semiconductive ceramic 12 The surface resistivity can be adjusted to be relatively high.

As mentioned above, although embodiment of this invention was described, the manufacturing method of the semiconductive ceramic of this invention and a semiconductive ceramic is not limited to said each embodiment, The range which does not deviate from the summary of this invention Of course, various improvements and modifications may be made.

DESCRIPTION OF SYMBOLS 10 Ceramic member with electrode 11 Through-hole 12 Semiconductive ceramic 12A Internal region 12B Surface region 14a and 14b Electrode 18a and 18b Joining layer 100 Electron beam irradiation apparatus 101 Electron beam source 103 Container 105 Electron beam source power source 106 Acceleration power source 107 Cathode 109 Heating filament

Claims (4)

Contains aluminum nitride as a main component and at least carbon,
The peak of the C _1S spectrum by X-ray photoelectron spectroscopy when the inner region is irradiated with X-rays is C _1S A, and the peak of the C _1S spectrum by X-ray photoelectron spectroscopy when the surface region is irradiated with C-rays is C _{1 When 1S} B,
A semiconductive ceramic characterized in that the half width of C _1S B is smaller than the half width of C _1S A. 2. The semiconductive ceramic according to claim 1, wherein the half width of C _1S B is less than 80% of the half width of C _1S A. 3. The semiconductive ceramic according to claim 1, wherein the surface resistivity is 1 × 10 ⁶ to 1 × 10 ⁹ . A method for producing semiconductive ceramics mainly composed of aluminum nitride,
In a state where a ceramic containing aluminum nitride as a main component and a carbon-containing member containing carbon as a main component are arranged in a chamber of a heating device, the inside of the chamber is evacuated and the inside of the chamber is set to 600 ° C to 1000 ° C. By heating the ceramics by raising the temperature, the peak of the C _1S spectrum by X-ray photoelectron spectroscopy when the inner region is irradiated with X-rays is C _1S A, and the surface region is irradiated with X-rays. A semiconductive ceramic whose main crystal is aluminum nitride and whose _C1S B half-value width is smaller than the _C1S A half-value width when the _C1S spectrum peak by linear photoelectron spectroscopy is _C1S B A method for producing a semiconductive ceramic, characterized in that it is obtained.

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