JP4313186B2 - Electrostatic deflector - Google Patents

Description

  The present invention relates to an electrostatic deflector of an electron beam irradiation apparatus used in a semiconductor EB exposure apparatus, an inspection apparatus, an electron microscope, and the like.

  In recent years, as integrated circuits have been miniaturized and densified, exposure methods using charged particle beams such as electron beams and ion beams, or X-rays have been used in place of photolithography technology, which has been the mainstream of fine pattern formation for many years. New exposure methods to be used have been studied and realized.

  Conventionally, as an electrostatic deflector of an electron beam irradiation apparatus using an electron beam typified by an EB exposure apparatus that exposes a fine wiring pattern and a high-sensitivity and high-resolution electron beam inspection apparatus using an electron beam. In order to deflect the trajectory of the electron beam and arrange the condensing part at an equal distance from the electrode, a cylindrical substrate is used, and an insulating ceramic is used as the material thereof. An electrode made of a thin metal film such as Au or Pt polarized in plural is formed on the inner peripheral surface of the cylindrical substrate. As a method for this polarization, a method in which a small groove in the axial direction is formed in the inner peripheral portion of the cylindrical base and a plurality of electrodes are formed in the radial direction has been generally adopted. A magnetic field is generated by applying a voltage to the plurality of electrodes, and the irradiation direction of a desired electron beam can be controlled.

  At this time, in order to increase the resolution of exposure, it is desirable to apply as high a voltage as possible. However, when the cylindrical substrate is insulating, when a high voltage is applied, the electrodes are charged up between the electrodes formed on the cylindrical substrate. There was a problem. For this reason, in order to prevent charge-up, a means for enlarging the groove shape and widening the width between the electrodes has been adopted, but this leads to an increase in the size of the electrostatic deflector itself. An EB exposure apparatus or an electron beam inspection apparatus equipped with an electrostatic deflector is large because the size of the apparatus itself is increased, and it takes time to start up and maintain the apparatus, and the cost of the apparatus itself increases. It was a problem. Also, as a recent technical trend, in the case of an EB exposure apparatus, in order to increase exposure throughput, in the case of an electron microscope, an electron beam is irradiated at a low acceleration voltage in order to reduce damage caused by an electron beam of a sample to be observed. It is attracting attention. Therefore, there is also a demand for downsizing the electrostatic deflector itself that irradiates the electron beam.

  However, when conventional insulating ceramics are used as a cylindrical substrate of an electrostatic deflector, charge-up between polarized electrodes becomes more remarkable. This is because when the cylindrical substrate of the electrostatic deflector is made smaller, the width between the polarized electrodes is inevitably reduced, so that each electrode is easily charged. Therefore, there is a limit to narrowing the width between the electrodes of the cylindrical substrate, and it has not been possible to satisfy the demand for downsizing.

For this reason, it is considered that the material used for the cylindrical substrate in which the electrostatic deflector is miniaturized is preferably not an insulating material. In Patent Document 1, the electrode of the electrostatic deflector is at least 10 ^{−5 to} 10 Ω · m. An electrostatic deflector for an electron beam exposure apparatus has been proposed in which a metal film is formed on the surface of a conductive ceramic having a specific resistance selected in the above range.

  On the other hand, although it differs from the use of the above-mentioned electrostatic polarizer, it is indicated by patent documents 2-5 as ceramics which are not insulation.

Patent Document 2 proposes a material having a resistivity of 10 ⁵ to 10 ¹¹ Ω · m in which titanium oxide, vanadium pentoxide, chromium oxide, manganese oxide, or the like is added to alumina.

Patent Document 3 proposes a semiconducting material having a volume resistivity in the range of 10 to 10 ⁶ Ω · m as a conductive material used in a recording / reproducing apparatus, and has a basic composition of alumina and a spherical titanium in the balance. It has been proposed that an oxide is present, and at least a part of the titanium oxide exists as a composite oxide with alumina having an oxygen amount smaller than the chemical equivalent .

Patent Document 4 proposes a semiconductive material having a volume resistivity of 10 ⁷ to 10 ¹¹ Ω · m as a member for an electrostatic chuck, and 0.5 to 3.6 mass of titanium oxide in terms of Ti. %, Boron and / or a boron compound in an amount of 0.04 to 0.9% by mass in terms of B, and the balance being substantially made of alumina and obtained by non-oxidizing atmosphere firing has been proposed.

Patent Document 5 proposes a recording / reproducing head nonmagnetic ceramic as a semiconductive material having a volume resistivity of 10 ⁸ Ω · m or more.
JP 2000-11937 A JP-A-8-67553 Japanese Patent Laid-Open No. 2001-19536 Japanese Patent Laid-Open No. 2003-119071 JP-A-7-287815

However, as described above, in Patent Document 1, a material whose volume resistivity of the cylindrical substrate is 10 ⁻⁵ to 10 Ω · m is applied to the electrostatic deflector. However, in recent years, the accuracy of the deflection function is improved and the response is improved. In order to increase the speed, a high voltage of 5 kV or higher is often applied, and when the volume resistivity is 10 ⁻⁵ to 10 Ω · m, the electrostatic deflector is polarized in plural on the inner peripheral portion of the cylindrical substrate. There has been a problem of electrical conduction between existing electrodes.

  Moreover, although it is possible to use the material of patent documents 2-5 by which the material which is not an insulation is disclosed as charge-up prevention, all have a problem in using for an electrostatic deflector. That is, in Patent Document 2, the void occupancy ratio of the ceramics constituting the cylindrical substrate is large, and when vacuuming is performed, moisture adsorbed by the voids or organic deposits become a source of outgas. In addition, chromium oxide and manganese oxide added to obtain conductivity are magnetic, and when used as an electrostatic deflector, there is a problem that distortion occurs in the magnetic field. It was.

Also, in Patent Document 3, the porosity is as high as 2.8 to 8.3%, and when used as an electrostatic deflector, there is a problem that it becomes an outgas generation source as in Patent Document 2. In addition, since the mixed powder of alumina powder and titanium oxide powder is fired in a reducing atmosphere, the alumina crystals are not densely sintered, so that Al ₂ TiO _X is not easily dispersed and solid-dissolved at the alumina grain boundaries. , Al ₂ TiO _X is difficult to act as a dopant that becomes a path for electrons, and the dielectric strength is a low value.

Further, in Patent Document 4, since boron nitride or boron carbide is added, boron nitride or boron carbide is oxidized when fired in an air atmosphere, and therefore needs to be fired in a non-oxidizing atmosphere. For this reason, alumina powder, titanium oxide, and boron compound powder must be sintered by hot pressing, HIP or gas pressure firing, and are inevitably complicated such as a cylindrical substrate used as an electrode of an electrostatic deflector. Therefore, it is difficult to obtain a highly accurate sintered body, which is not suitable for an electrostatic deflector. Also, since the alumina powder, titanium oxide and boron compound powder are sintered by hot pressing, HIP or gas pressure firing, it is necessary to have a firing profile in a short time. Al ₂ Ti _X and a boron compound are difficult to uniformly disperse in the boundary, and the dielectric strength is lowered, and there is a problem that charge-up is likely to occur between electrodes.

Furthermore, Patent Document 5, as a material for recording and reproducing head, the purpose of leak static electricity due to sliding, a volume resistivity of 10 ⁸ Ω · m or more, preferably 10 ⁹ Ω · m or more, further 10 ¹⁰ Omega -Although m or more is considered to be optimal, there is no mention of using it as an electrostatic deflector, and a high voltage is applied even if it is used temporarily. There is a problem that the electric charge is charged and the charge is increased.

  As described above, the conventional materials are not suitable for the cylindrical substrate of the electrostatic deflector, and even when the cylindrical substrate having a deflection function is miniaturized, the non-magnetic electron beam is distorted. In addition, even when a high voltage is applied without charge being charged and charging up, there is no conduction between the electrodes that are polarized in the inner periphery of the electrostatic deflector. An electrostatic deflector was desired.

Accordingly, the present inventors have view of the above problems, the main component Alumina and titanium oxide, the production of alumina ceramics portion of the titanium oxide is present as a complex oxide of alumina oxygen is less than the chemical equivalent A method,
Provided is a method for producing alumina ceramics, in which a molded product formed by molding a mixture of alumina powder and aluminum titanate powder is heat-treated in the atmosphere and in a reducing atmosphere, and fired through the respective steps.

The mixture is characterized in that an organic dispersant is added to and mixed with the alumina powder and the aluminum titanate powder.

The present invention also includes a cylindrical substrate made of alumina ceramics produced by the above-described method for producing alumina ceramics, and a plurality of electrodes provided on an inner periphery of the cylindrical substrate. An electrostatic deflector characterized by having a width of 1 mm or less is also provided.

  The alumina ceramics is 10 ⁴ -10 ¹⁰ Preferably, it has a volume resistivity of Ω · m and a void occupancy of 2% or less.

  According to the configuration of the present invention, as a result of intensive studies by the inventors, even if the width between the respective electrodes formed on the inner peripheral portion is reduced to 1 mm or less by downsizing the cylindrical base body, When using alumina ceramics with a dielectric strength of 3 kV / mm or higher when applying voltage under vacuum, there is no charge build-up between the electrodes, and there is no electrical connection between the electrodes. In addition, it is possible to polarize between the electrodes, thereby providing an electrostatic polarizer capable of passing a stable electron beam. Therefore, by using this, the focus accuracy and response speed of the electron beam are improved, so that a highly accurate electrostatic deflector can be obtained.

  Furthermore, since the electrostatic deflector can operate sufficiently even if the voltage is as high as possible, the width between the polarized electrodes can be minimized, and it is smaller than the conventional electrostatic deflector. It became possible to make it. Therefore, the EB exposure apparatus and electron beam inspection apparatus equipped with the electrostatic deflector according to the present invention can be miniaturized, and not only the installation area and apparatus cost are superior, but also characteristics such as exposure accuracy and resolution are excellent. There is.

The electrostatic deflector according to the present invention is characterized in that the titanium oxide is aluminum titanate, so that Al ₂ TiO ₅ which is a reaction product with α-alumina is uniformly dispersed in the alumina grain boundary. Thus, it is easy to make a solid solution state and the dielectric strength can be improved.

  Further, the cylindrical substrate for an electrostatic deflector according to the present invention is characterized in that the alumina is 70 to 85% by weight and the aluminum titanate is 15 to 30% by weight. It is possible to deal with complicated and highly accurate processing of an electrostatic deflector.

  Then, by setting the void occupancy ratio of the cylindrical substrate of the electrostatic deflector described above to 2% or less, it is possible to reduce the amount of outgas generation under vacuum pressure as much as possible.

  Hereinafter, the best mode for carrying out the present invention will be described.

  1A and 1B are diagrams showing an embodiment of an electrostatic deflector 1 according to the present invention, in which FIG. 1A is a sectional view in the radial direction, and FIG. 1B is a diagram showing an XX section in FIG. .

  The electrostatic deflector 1 of the present invention includes a cylindrical base 2 used as a lens, an aperture member, and a polarizer in an electron optical system used for electron optics, and an electrode 3 formed on an inner peripheral portion of the cylindrical base 2 described later. And a pin 4 for applying a voltage from the outside as a voltage application connector.

  The cylindrical base body 2 is formed into a cylindrical shape by a through hole formed in the center of a cylinder, and a plurality of electrodes 3 are formed in the circumferential direction via grooves 5 in the inner peripheral portion thereof. Further, the above-described pin 4 passes through the side wall of the cylindrical base 2 and is connected to the electrode 3.

  The electrode 3 may be a nonmagnetic metal film, and is formed of one or more metal films of metals such as Cu, Ni, Au, Pt, Ag, TiN, and TiC. A plurality of electrodes 3 are formed coaxially with the central axis of the cylindrical substrate 2 and are also formed on the same circumference. The number of electrodes 3 on the same circumference is one or two or more even numbers. It has become a piece. When the number of the electrodes 3 is two or more even numbers on the same circumference, it is desirable that the areas are substantially equal. Moreover, when it becomes an even number of 2 or more, it becomes an electrically independent electrode basically. FIG. 1 shows a case where four electrodes 3 are formed on the same circumference.

  The electrodes 3 are polarized with the adjacent electrodes 3 by the grooves 5 arranged in the axial direction. The groove 5 may be only the electrode 3 or may be formed in the thickness direction of the cylindrical substrate 2. In addition, the groove | channel in FIG. 1 is the figure by which the groove | channel 5 was formed to the cylindrical base | substrate 2. As shown in FIG.

  The dimensional accuracy such as cylindricity, roundness, and coaxiality of the inner periphery of the cylindrical substrate 2 needs to be processed from several μm to submicron order in order to obtain necessary and sufficient performance as the electrostatic deflector 1. Preferably, the cylindricity and roundness of 2 μm or less and the coaxiality of the inner diameter with respect to the outer diameter are 2 μm or less.

The pin 4 is made of a non-magnetic material such as Au, Pt, or Cu, and is joined to both the cylindrical substrate 2 and the electrode 3 by brazing so as to be electrically connected to the electrode 3. The brazing portion of the pin 4 may be a non-magnetic brazing material such as Ag, Cu, or Ti, and 10 ⁻⁷ torr to ensure airtightness between the inner peripheral portion and the outer peripheral portion of the cylindrical base 2. The following airtightness is required.

The material of the cylindrical substrate 2 is composed of alumina and titanium oxide as main components, and a part of the titanium oxide is a composite oxide with alumina having less oxygen than the chemical equivalent (hereinafter referred to as “oxygen-deficient titanium oxide”). It is important to make the alumina ceramics present as a), and in particular, as a method of causing the oxygen-deficient titanium oxide to be present in the alumina ceramics, the starting material is formed by mixing an alumina powder with an aluminum titanate powder, After firing, it is important to produce alumina ceramics by firing again in a reducing atmosphere. That is, by forming and firing an aluminum titanate powder containing alumina powder, Al ₂ TiO _5, which is a reaction product with α-alumina, is uniformly dispersed and dissolved in the alumina grain boundary. Easy to do. Then, a part of the uniformly dispersed Al ₂ TiO ₅ is fired in a reducing atmosphere to form an oxygen-deficient titanium oxide, thereby obtaining a volume resistivity of 10 ⁴ to 10 ¹⁰ Ω · m, and a vacuum. A cylindrical substrate 2 having a dielectric strength of 3 kV / mm or more when a voltage is applied below can be stably obtained.

On the other hand, as shown in Patent Documents 2 to 5, when a simple titanium oxide such as TiO ₂ is added to 15 to 30% by weight of alumina, Al ₂ TiO ₅ is formed at the alumina grain boundary. is reduced, because the TiO ₂ is most existing tissue alumina grain boundaries, this TiO ₂ calcined at further reducing atmosphere alumina ceramics was added to the alumina, a portion of the alumina ceramics chemical equivalent of oxygen amount Compared to the composite oxide with alumina reduced in amount and the one added with the same amount of aluminum titanate in terms of titanium oxide as in the present invention, the volume resistivity value and the voltage applied under vacuum It has been found that there is a difference in dielectric strength values.

By the way, being oxygen-deficient titanium oxide means a state in which a part of Ti ⁴⁺ of titanium oxide dissolved in alumina grain boundaries, for example, TiO ₂ and Al ₂ TiO ₅ is reduced to Ti ^3+. Said, these can be confirmed by X-ray diffraction or Auger electron spectroscopy.

The content of the starting material constituting the alumina ceramic of the present invention is preferably composed of 70 to 85% by weight of alumina powder and 15 to 30% by weight of aluminum titanate powder, and the content of aluminum titanate powder is 15% by weight. If it is less than 10%, the fired ceramic is reduced again to form an oxygen-deficient titanium oxide, so that the volume resistivity becomes larger than 10 ¹⁰ Ω · m. When applied to the deflector 1, electric charges are charged between the electrodes 3 that are polarized in a plural number and are charged up. On the other hand, if the content of the aluminum titanate powder is more than 30% by weight, a part of the titanium oxide is reduced and fired, so that the volume resistivity becomes 10 ⁴ Ω · m or less even as oxygen-deficient titanium oxide. Since conduction is made between the plurality of electrodes 3 polarized on the inner peripheral portion of the cylindrical body of the electric deflector 1, the polarization structure cannot be maintained, and it becomes difficult to stably emit an electron beam. End up. Therefore, it is preferable that the alumina powder is 70 to 85% by weight and the aluminum titanate powder is 15 to 30% by weight. As a more preferable range, the volume resistivity can be stably set to 10 ⁵ to 10 ⁸ Ω · m by making alumina 72 to 77 wt% and aluminum titanate powder 23 to 28 wt%.

Further, it is important that these cylindrical substrates 2 have a volume resistivity of 10 ⁴ to 10 ¹⁰ Ω · m. The range of the volume resistivity of 10 ⁴ to 10 ¹⁰ Ω · m is a value higher than 10 ¹⁰ Ω · m. For example, in the case of an EB exposure apparatus, a high voltage is reduced when an electron beam is emitted. When applied to the electric deflector 1, electric charges are charged between the plurality of electrodes 3 polarized on the inner peripheral portion of the cylindrical substrate 2 and charged up. On the other hand, if the value is smaller than 10 ⁴ Ω · m, the volume specific resistance value is too low, which causes a problem of conduction between the polarized electrodes 3 and stable exposure. It becomes difficult.

Therefore, the volume resistivity of the electrostatic deflector 1 is preferably in the range of 10 ⁴ to 10 ¹⁰ Ω · m, and more preferably 10 ⁵ to 10 ⁸ Ω · m. Here, the volume resistivity can be measured by a three-terminal method based on JIS C 2141 using an insulation resistance meter such as DSM-8103 manufactured by Toa Denpa Kogyo.

  Furthermore, it is necessary that the dielectric strength when applying voltage under vacuum is 3 kV / mm or more.

  That is, as a result of diligent study by the present inventors, even when the width between the electrodes 3 formed on the inner peripheral portion is reduced to 1 mm or less by downsizing the cylindrical substrate 2, voltage application under vacuum is performed. If an alumina ceramic having a dielectric strength of 3 kV / mm or more is used, electric charges are not charged between the electrodes 3 and the electrodes 3 are not electrically connected to each other. Accordingly, it is possible to provide an electrostatic deflector through which an electron beam can pass stably. Therefore, by using this, the focus accuracy and response speed of the electron beam are improved, so that a highly accurate electrostatic deflector can be obtained. The dielectric strength is preferably 5 kV / mm or more, more preferably 5 to 15 kV / mm.

In the present invention, the vacuum under which the insulator force is measured means an atmospheric pressure of 10 ⁻⁵ torr or less.

Here, the dielectric strength refers to a specimen of arbitrary size (in the present invention, a material used for a cylindrical substrate), plated with a conductive film such as Au or Pt, and then with a diamond tool or the like, with a width of 0.3 mm and a depth of 0. A test piece for measuring the dielectric strength is obtained by processing a through groove of 3 mm. This test piece is placed in a vacuum chamber, a terminal to which a voltage can be applied is connected to the plated portion of the conductive film on both sides of the through groove, one side of the cable connected to the power supply device is set to +, and the other is − Connect. Then, after evacuating the inside of the vacuum chamber to 10 ⁻⁵ torr or less, a voltage is applied stepwise to both connected terminals, and the voltage charged up between the through grooves is taken as the dielectric strength. At this time, the power supply device, the groove shape, and the like are not particularly limited.

Furthermore, the void occupancy ratio of the cylindrical substrate 2 is preferably 2% or less, and the generation amount of outgas can be reduced as much as possible at a vacuum pressure of 10 ⁻⁷ torr or less necessary for EB electron beam irradiation. .

By the way, when the void occupancy is a value larger than 2%, it is difficult to evacuate due to moisture and organic matter entering the void at the vacuum pressure of 10 ⁻⁷ torr or less necessary for EB electron beam irradiation. In addition, if the outgas contains a contamination source, it may cause adverse effects such as contamination in the vacuum chamber.

Therefore, by controlling the raw material refining process of alumina and aluminum titanate and optimizing the firing profile, by making the crystal grain size uniform and fine, the void occupancy is 2% or less, and EB electron beam irradiation The generation amount of outgas can be reduced as much as possible at a vacuum pressure of 10 ⁻⁷ torr or less necessary for the above. Depending on the application of the electrostatic deflector 1, the vacuum pressure may be 10 ⁻⁹ torr or less, and the void occupancy ratio of the electric deflector 1 may be 1% or less in order to further reduce the outgas emission amount. More preferred.

  The void occupancy ratio can be measured by image processing with an image processing apparatus such as LUZEX-FS manufactured by Nireco after a ceramic sintered body having an arbitrary size is prepared and the surface is mirror-polished.

  Further, the cylindrical substrate 2 of the present invention having an inner diameter of 20 mm or less is preferably used, but a small one having an inner diameter of 3 to 10 mm is used. As the inner diameter W is reduced, the width w of the electrode 3 is also reduced. The width w is preferably 1 mm or less, and more preferably, the width w is 0.2 to 0.6 mm.

In the cylindrical substrate 2 of the present invention, in order to uniformly disperse minute Al ₂ TiO _X at alumina grain boundaries, in the raw material purification step of alumina and aluminum titanate, the wet mixed powder of alumina and aluminum titanate is pulverized. The particle size is controlled to be 0.2 to 0.8 μm, and the dispersion of aluminum titanate in alumina is made uniform by addition of an organic dispersion material, followed by drying and granulation with a spray dryer, A secondary material is prepared.

Here, when alumina and titanium oxide have a pulverized particle size of 0.2 to 0.8 μm, they may be re-agglomerated. In particular, when titanium oxide is re-agglomerated, it becomes difficult to obtain a state in which it is uniformly dispersed at the alumina grain boundary. Therefore, the use of an organic dispersant is effective for uniformly dispersing Al ₂ TiO _X at the alumina grain boundary. . An organic dispersant is effective when added when pulverizing titanium oxide or when mixing and pulverizing alumina and titanium oxide. As the dispersant used, an acetylene-based, carboxylic acid-based or ester-based dispersant is effective.

In addition, by controlling the firing profile in the firing process, the maximum temperature is 1400 to 1600 ° C., the temperature range from the shrinkage start temperature to the maximum temperature, and the crystal growth from the maximum temperature until the crystal grain growth stops, the alumina crystal grains The alumina-aluminum titanate sintered body in a solid solution state in which the size of the diameter became fine and Al ₂ TiO _5, which is a reaction product with α-alumina, was uniformly dispersed in the alumina grain boundary was obtained. Thereby, not only obtaining the state where Al ₂ TiO _{X serving} as a path of electricity is uniformly dispersed in the alumina grain boundaries, but also making the crystal grain size of alumina as fine as 1.0 to 10 μm, The electric path can be shortened and the dielectric strength can be increased.

  Below, the manufacturing method of the electrostatic deflector 1 of this invention is demonstrated.

  First, as starting materials, alumina particles having an alumina purity of 99% or more and an average particle size of 0.3 to 1 μm and aluminum titanate having an aluminum titanate purity of 99% or more and an average particle size of 0.3 to 2 μm are used. The organic material additive is added, mixed and pulverized in a wet state, and then dried and granulated with a spray dryer to prepare a secondary material.

  The obtained secondary material is molded into a desired shape by applying a molding pressure in the range of 80 to 200 MPa by a known molding method such as CIP molding or mechanical press molding, and the desired shape is formed by a known cutting process. .

Next, it is fired so that the maximum temperature is in the range of 1400 to 1600 ° C. to form an alumina-aluminum titanate sintered body. At this time, in order to satisfy the performance of the electrostatic deflector 1 as the base 2, the temperature range from the shrinkage start temperature to the maximum temperature and the temperature range from the maximum temperature until the crystal grain growth stops are controlled to be optimum conditions, and alumina Alumina-titanium, which has a solid solution state in which Al ₂ TiO _5, which is a reaction product with α-alumina, is uniformly dispersed at the grain boundary, is stable in terms of electrical characteristics and void occupancy, and has little deformation An aluminum oxide sintered body is obtained.

  Next, this alumina-aluminum titanate sintered body is heat-treated in a reducing atmosphere. That is, heat treatment is performed at 1000 to 1500 ° C. in a firing furnace in a reducing atmosphere such as hydrogen, nitrogen, or argon, or HIP treatment. And it finishes in a predetermined shape by well-known grinding and polishing.

  Next, the pins 4 are brazed to the base 2, and the electrodes 3 are attached to the inner peripheral surface to form the electrostatic deflector 1. At this time, as a means for forming the electrode, a known metal film forming means such as plating, CVD, PVD or the like is used.

By the way, the electrostatic deflector 1 of the present invention is characterized in that the titanium oxide is aluminum titanate. When the titanium oxide is aluminum titanate, a reaction product of α-alumina at the alumina grain boundary. It is easy to make a state in which Al 2 TiO 5 is uniformly dispersed and dissolved, and by reducing the amount of oxygen from the chemical equivalent by reduction firing, it has a volume resistivity of 10 ⁴ to 10 ¹⁰ Ω · m, and 10 ^The electrostatic deflector 1 having a dielectric strength of 3 kV / mm or more when a voltage is applied can be stably obtained under a vacuum of ⁻⁵ torr or less.

Examples of the present invention will be described below.

Example 1
The sintered body composition of an alumina raw material having an alumina purity of 99.5% and an average particle diameter of 0.5 μm and an aluminum titanate raw material having an average particle diameter of 99.7% and an average particle diameter of 1.2 μm is shown in Table 1. Weighed so that 99.9% alumina balls and ion-exchanged water were added, wet pulverized until the pulverized particle size became 0.3 μm, dried and sized through 80 mesh, then powdered into a φ60 mold The body was filled and mechanical press molding was performed at a pressure of 100 MPa. The obtained molded body was fired at a sintering temperature of 1500 ° C. and then reduced and fired at 1350 ° C. in a hydrogen atmosphere to perform a reduction treatment.

Table 1 shows the characteristics of the obtained sintered body.

  Here, the Archimedes method was used for the density, and a test piece having a strength of 3 mm × 4 mm × 40 mm was cut out and measured by a 3-point bending test method with a span of 30 mm.

  Next, the volume resistivity in the three terminal method based on JIS C 2141 was measured.

In addition, the dielectric strength is 50 mm x 50 mm x 10 mm, and after plating the surface with Au, a diamond tool is used to process through-grooves with a width of 0.3 mm and a depth of 0.3 mm. A test specimen for measurement was obtained. Install this test piece in a vacuum chamber, connect a terminal to which voltage can be applied to the conductive plating parts on both sides of the through groove, connect one side of the cable connected to the power supply to +, and the other to- After evacuating the inside of the vacuum chamber to 10 ⁻⁵ torr, a voltage was applied stepwise to both connected terminals, and a measurement method was selected in which the voltage charged up between the through grooves was the dielectric strength.

As a result, with respect to the alumina-aluminum titanate sintered body of the electrostatic deflector 1 of the present invention, in Examples 4 to 7, the volume specific resistance, the dielectric strength, and the void occupancy ratio are both the base 2 for the electrostatic deflector 1. As a result, sufficient characteristics are obtained. On the other hand, for Examples 1 to 3 and 8 and Comparative Examples 1 to 3, good results were obtained for the volume resistivity, but the dielectric strength was insufficient to be applied as the electrostatic deflector 1. It is a value, the void occupancy is large, and it is highly possible that it becomes an outgas generation source at a vacuum pressure of 10 ⁻⁷ torr or less necessary for EB electron beam irradiation, and it is determined that it cannot be used.

(Example 2)
A test piece was prepared in the same manner as in Example 1, grooves having different sizes were formed in the test piece, and a dielectric strength test was performed.

With respect to the groove shape, the dielectric strength was measured in the direction of increasing the creepage distance, with the industrially feasible size, that is, groove width 0.3 mm × groove depth 0.3 mm being the minimum size. As in Example 1, a test piece was placed in a vacuum chamber, a terminal to which a voltage could be applied was connected to the conductive plating part on both sides of the through groove, one side of the cable connected to the power supply device was set to +, and the other side was connected. After evacuating the inside of the vacuum chamber to 10 ⁻⁵ torr, a voltage is applied stepwise to both connected terminals, and the voltage charged up between the through grooves is taken as the dielectric strength.

The results are shown in Table 2.

As a result, when the groove size is industrially feasible, that is, when the groove width is 0.3 mm and the depth is 0.3 mm, the dielectric strength is more than 3.0 kV / mm in any of Examples 9 to 11. A high value was obtained. In addition, the creepage distance was increased by increasing the groove width and depth, and the dielectric strength was confirmed. As a result, even higher dielectric strength values could be obtained. The accuracy of the lens is improved, and the response speed is improved. However, when the groove shape is increased, the size of the electrostatic deflector 1 is inevitably increased. Therefore, it can be said that it is not preferable to increase the groove shape. Accordingly, in order to obtain the necessary and sufficient characteristics as the performance of the electrostatic lens without increasing the size of the electrostatic deflector 1 more than necessary, the groove shape has a width of about 0.6 mm and a depth of about 0.6 mm. The dielectric strength at that time is 14.3 kV / mm. Therefore, the range of 3 to 15 kV / mm is an industrially realistic value for the dielectric strength.

It can be used for an EB electron beam irradiation apparatus, an EB exposure apparatus, and an electron beam inspection apparatus that improve the accuracy and response speed of the deflection direction of the electron beam.

It is a figure which shows one Example of the electrostatic deflector which concerns on this invention, (a) is sectional drawing of radial direction, (b) is a figure which respectively shows the XX cross section of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrostatic deflector 2 ... Cylindrical base | substrate 3 ... Electrode 4 ... Pin 5 ... Groove

Claims (4)

A main component Alumina and titanium oxide, a portion of the titanium oxide is a manufacturing method of alumina ceramics present as a composite oxide of alumina oxygen is less than stoichiometric amounts,
A molded product formed by molding a mixture of alumina powder and aluminum titanate powder,
Heat treatment in the air and in a reducing atmosphere, characterized by firing through each step,
A method for producing alumina ceramics. The method for producing an alumina ceramic according to claim 1, wherein the mixture is obtained by adding an organic dispersant to the alumina powder and the aluminum titanate powder and mixing them. A cylindrical substrate made of alumina ceramics produced by the method for producing alumina ceramics according to claim 1 or 2,
  A plurality of electrodes provided on the inner periphery of the cylindrical substrate,
  An electrostatic deflector characterized in that a width between the electrodes is 1 mm or less.   The alumina ceramic is 10 ⁴ -10 ¹⁰ 4. The electrostatic deflector according to claim 3, wherein the electrostatic deflector has a volume resistivity of Ω · m and a void occupancy of 2% or less.

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