Transmitter and device equipped with the same

Abstract

The emitter according to the present disclosure includes: a first heater and a second heater that generate heat by being energized; an electron source composed of a first material that releases electrons when heated by the first heater and the second heater; and an intermediate member that is interposed between the first heater and the second heater and the electron source, respectively, and is composed of a second material having a lower thermal conductivity than the first material.

Description

Technical Field

[0001] The present disclosure relates to an electron-emitting emitter and a device including the same. Background Art

[0002] Electron-emitting emitters are used, for example, in electron microscopes and semiconductor inspection devices. An emitter includes an electron source and a heater that heats the electron source to a temperature at which the electron source emits electrons. Patent Document 1 discloses an electron source having the following structure: an electron-emitting material (chip) formed of a hexaboride of a rare earth element is sandwiched between a pair of heating elements, and the heating elements are sandwiched between a pair of conductive pillars. In this electron source, an insulating coating is formed in a region of the heating element that does not contact the electron-emitting material and the conductive pillars.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2006-12496 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] When observing the chip after the electron source disclosed in Patent Document 1 has actually been operated for a long period of time, vapor deposition of hexaboride was confirmed near the contact portion of the heater with the conductive pillar. It is presumed that the temperature near the contact portion of the heater with the conductive pillar decreases due to heat conduction to the conductive pillar, and thus the hexaboride evaporated from the chip fails to be re-evaporated and is vapor-deposited on this region (see (b) of Figure 5 . Figure 5 (b) is a longitudinal sectional view schematically showing a state in which a material constituting the electron source 11 is vapor-deposited near the heaters 15a and 15b. A vapor-deposited material D is attached so as to cover the upper surfaces of the conductive pillars 17a and 17b and a part of the upper surfaces of the heaters 15a and 15b that are continuous therewith. Figure 5 In (a) of Figure 5 and Figure 5 (b), the arrows indicate the current during energization. In a state where the vapor-deposited material D is not attached, as shown in (a) of Figure 5 , current is stably supplied to the heaters 15a and 15b. In contrast, as shown in (b) of Figure 5 , when the vapor-deposited material D is attached, the vapor-deposited material D hinders the stable current in the heaters 15a and 15b. It should be noted that in the invention described in Patent Document 1, by forming an insulating coating in a specified region of the heating element, a reduction in reliability due to vapor deposition of hexaboride is suppressed.

[0008] The present disclosure provides an emitter and a device including the same that can maintain high reliability even during long-term operation.

[0009] Means for Solving the Problem

[0010] One aspect of the present disclosure provides a transmitter. The transmitter includes: a first heater and a second heater that generate heat when energized; an electron source composed of a first material that releases electrons when heated by the first heater and the second heater; and an intermediate member that is interposed between the first heater and the second heater and the electron source, respectively, and is composed of a second material having a lower thermal conductivity than the first material.

[0011] In the transmitter according to the present disclosure, an intermediate member (second material) having a lower thermal conductivity than the electron source (first material) is provided between the electron source and the heater. With such a configuration, compared with the case where no intermediate member is provided, it is possible to operate under the condition that the temperature of the heater is higher. As a result, it is possible to suppress the deposition of the material constituting the electron source near the heater itself, and it is possible to suppress the deterioration of the performance of the transmitter caused thereby. Therefore, the transmitter according to the present disclosure can operate stably for a long time. The thermal conductivity of the intermediate member is preferably 100 W / m·K or less. The thermal conductivity in the present disclosure refers to the value at 20°C measured according to the method described in JIS R1611.

[0012] The transmitter according to the present disclosure is based on the concept of somewhat hindering the efficient heating of the electron source by the heater, and on the other hand, using the excess heat of the heater to suppress the deposition of the material constituting the electron source near the heater (for example, a pair of conductive pillars sandwiching the heater). In order to effectively realize this concept, it is preferable that the intermediate member has a certain volume and is disposed between the electron source and the heater. That is, the length of the shortest path of the intermediate member through which the heat travels from the heater to the electron source is preferably 100 μm or more.

[0013] It is preferable that the resistivity of the intermediate member is sufficiently smaller than the resistivity of the heater. The resistivity of the intermediate member is preferably 300 μΩ·m or less. By making this value 300 μΩ·m or less, it is possible to suppress excessive heating of the intermediate member caused by energization. The resistivity of the heater is preferably 500 μΩ·m or more. By making this value 500 μΩ·m or more, it is possible to sufficiently heat the heater by energization. The resistivity in the present disclosure refers to the value at 20°C measured according to the method described in JIS R7222.

[0014] The intermediate member preferably covers the surface of the electron source other than the electron emission surface. By covering the surface of the electron source other than the electron emission surface with the intermediate member, it is possible to trap the evaporant of the electron source during energization by the intermediate member. That is, at least the diffusion of the evaporant of the material of the electron source toward the heater can be suppressed. Therefore, it is possible to further highly suppress the deterioration of the performance of the emitter due to the evaporation of the material constituting the electron source.

[0015] One aspect of the present disclosure provides an apparatus including the above-described emitter. As an apparatus including an emitter, for example, an electron microscope, a semiconductor manufacturing apparatus, an inspection apparatus, and a processing apparatus can be cited.

[0016] Advantageous Effects of Invention

[0017] According to the present disclosure, an emitter and an apparatus including the same that can maintain high reliability even during long-term operation can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Figure 1 FIG. (a) is a longitudinal sectional view schematically showing a first embodiment of an emitter according to the present disclosure, Figure 1 FIG. (b) is Figure 1 a cross-sectional view of the emitter shown in FIG. (a).

[0019] Figure 2 Figure 2 FIG. (a) is a longitudinal sectional view schematically showing a second embodiment of an emitter according to the present disclosure, Figure 2 FIG. (b) is Figure 2 a cross-sectional view of the emitter shown in FIG. (a).

[0020] Figure 3 Figure 3 FIG. (a) is a longitudinal sectional view schematically showing a third embodiment of an emitter according to the present disclosure, Figure 3 FIG. (b) is Figure 3 a top view of the emitter shown in FIG. (a).

[0021] Figure 4 Figure 4 is a thermal imaging camera image showing the upper surface temperature of the emitter according to the example.

[0022] Figure 5 Figure 5 FIG. (a) is a longitudinal sectional view schematically showing an emitter according to a comparative example, Figure 5 FIG. (b) is a longitudinal sectional view schematically showing a state in which a material (lanthanum boride) constituting an electron source is vapor-deposited near a heater of the emitter shown in FIG. (a). Figure 5 ​​​​​​​​​​Detailed Implementation Modes

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following description, the same reference numerals are used for the same elements or elements having the same functions, and repeated descriptions are omitted. It should be noted that the present invention is not limited to the following embodiments.

[0024] <First Embodiment>

[0025] Figure 1 (a) of is a schematic longitudinal sectional view of the emitter related to the first embodiment, Figure 1 and (b) of is Figure 1 a cross-sectional view of the emitter shown in (a) of. The emitter 10 shown in these figures includes: an electron source 1; a pair of heaters 5a, 5b (a first heater and a second heater) that generate heat by being energized; intermediate members 2a, 2b disposed between the electron source 1 and the heaters 5a, 5b; and a pair of conductive struts 7a, 7b disposed in a manner of sandwiching these components. The electron source 1 is made of a material (a first material) that releases electrons when heated. The intermediate members 2a, 2b are made of a material (a second material) having a lower thermal conductivity than the material constituting the electron source 1. The heaters 5a, 5b are used to heat the electron source 1. The pair of conductive struts 7a, 7b are used to hold the electron source 1 and the like and supply power to the heaters 5a, 5b. Examples of the device equipped with the emitter 10 include an electron microscope, a semiconductor manufacturing device, an inspection device, and a processing device. Hereinafter, each component of the emitter 10 will be described.

[0026] (Electron Source)

[0027] The electron source 1 is made of a first material (electron emission material) having electron emission characteristics. The front end portion 1a of the electron source 1 is formed in a conical shape, and electrons are released from the front end portion 1a. In the present embodiment, the electron source 1 is exposed on the side surfaces 10a, 10b of the emitter 10, respectively.

[0028] In the present embodiment, the shape of the portion other than the front end portion 1a of the electron source 1 is a quadrangular prism (see Figure 1 (a) of and Figure 1 (b) of). The length of the electron source 1 is, for example, 0.1 to 2 mm, and may also be 0.2 to 1.5 mm or 0.2 to 1 mm. By making the length 0.1 mm or more, there is a tendency for it to be easier to operate, and by making the length 2 mm or less, there is a tendency for the heating to be more uniform. The cross-sectional shape of the quadrangular prism portion in the electron source 1 is substantially square. The side length thereof is, for example, 0.02 to 1 mm, and may also be 0.05 to 0.5 mm or 0.05 to 0.15 mm.

[0029] Examples of the electron emission material include lanthanum boride (LaB6 ) Cerium boride (CeB 6 ) and other rare earth borides; high melting point metals such as tungsten, tantalum, hafnium and their oxides, carbides and nitrides; noble metal-rare earth alloys such as iridium-cerium.

[0030] From the viewpoints of electron emission characteristics, strength and workability, the electron emission material constituting the electron source 1 is preferably a rare earth boride. When the electron source 1 is formed of a rare earth boride, the electron source 1 is preferably a single crystal processed in such a manner that the <100> orientation that easily emits electrons is aligned with the electron emission direction. The electron source 1 can be formed into a desired shape by electrical discharge machining or the like. The side surface of the electron source 1 is considered to have a slower evaporation rate, so the (100) plane crystal face is preferred.

[0031] The material constituting the electron source 1 has a higher thermal conductivity than the materials constituting the intermediate members 2a and 2b. The thermal conductivity of the material constituting the electron source 1 is preferably 5 W / m·K or more, more preferably 10 W / m·K or more. By making the thermal conductivity of this material 5 W / m·K or more, the entire electron source 1 tends to be heated sufficiently and uniformly by the heat from the heaters 5a and 5b. It should be noted that the upper limit value of the thermal conductivity of this material is, for example, 200 W / m·K. The following shows the thermal conductivities of various materials.

[0032] · Lanthanum boride (LaB 6 ) : 60 W / m·K

[0033] · Tungsten: 177 W / m·K

[0034] The value T of the thermal conductivity of the electron source 1 E is preferably sufficiently larger than the value T of the thermal conductivity of the intermediate members 2a and 2b. I The value T of the thermal conductivity of the electron source 1 E relative to the value T of the thermal conductivity of the intermediate members 2a and 2b I The ratio (T E / T I ) is, for example, 7 to 13, and may also be 8 to 12 or 10 to 11. By making this ratio within these ranges, the temperatures of the heaters 5a and 5b during energization can be made moderately high. The temperatures of the heaters 5a and 5b during energization can be made, for example, 150 to 250 °C higher than the temperature of the electron source 1. Thereby, the material constituting the electron source 1 can be inhibited from being vapor-deposited near the heaters 5a and 5b.

[0035] (Intermediate member)

[0036] The intermediate members 2a and 2b are arranged so as to be in contact with and cover a pair of surfaces 1b and 1c of the electron source 1 (see Figure 1(b)). The intermediate members 2a and 2b are respectively exposed on the side surfaces 10a and 10b of the emitter 10. The length of the shortest path of the intermediate member through which the electrons pass when going from the heater to the electron source is preferably 100 μm or more. That is, in the present embodiment, the thickness of the intermediate member 2a (the distance between the electron source 1 and the heater 5a) is preferably 100 μm or more, and may be 100 to 1000 μm or 300 to 800 μm.

[0037] The intermediate members 2a and 2b are made of a material (second material) having a lower thermal conductivity than the material constituting the electron source 1. The thermal conductivity of the material constituting the intermediate members 2a and 2b is, for example, 100 W / m·K or less, preferably 1 to 100 W / m·K, and more preferably 1 to 60 W / m·K. The lower limit value of this value may be 2 W / m·K or 3 W / m·K. The upper limit value of this value may be 45 W / m·K or 40 W / m·K. By making the thermal conductivity of this material 1 W / m·K or more, there is a tendency for the heat from the heaters 5a and 5b to be sufficiently transferred to the electron source 1. On the other hand, by making the thermal conductivity of this material 100 W / m·K or less, there is a tendency for a sufficient temperature difference to be generated between the heaters 5a and 5b and the electron source 1.

[0038] The material constituting the intermediate members 2a and 2b preferably contains a high melting point metal or its carbide, and preferably contains at least one or more selected from tantalum metal, titanium metal, zirconium metal, tungsten metal, molybdenum metal, rhenium metal, tantalum carbide, titanium carbide, and zirconium carbide. In addition, this material may contain at least one or more of boron carbide and graphite (carbon material), and may also contain at least one or more of niobium, hafnium, and vanadium. As this material, glassy carbon (for example, Glassy Carbon (trade name, manufactured by REIHO Co., Ltd.)) can be used. As this material, boron nitride can also be used. The following shows the thermal conductivities of various materials.

[0039] · Rhenium metal: 48 W / m·K

[0040] · Boron carbide: 35 W / m·K

[0041] · Graphite: 80 - 250 W / m·K

[0042] · Glassy carbon: 5.8 W / m·K

[0043] The materials constituting the intermediate members 2a and 2b are electrically conductive. From the viewpoint of suppressing excessive heating of the intermediate members 2a and 2b due to energization, the resistivity of the materials constituting the intermediate members 2a and 2b is preferably lower than that of the materials constituting the heaters 5a and 5b. The resistivity of the materials constituting the intermediate members 2a and 2b is preferably 300 μΩ·m or less, more preferably 100 μΩ·m or less. By making the resistivity of this material 300 μΩ·m or less, there is a tendency to suppress excessive heating of the intermediate members 2a and 2b due to energization. It should be noted that the lower limit value of the resistivity of this material is, for example, 0.1 μΩ·m, and it can also be 0.3 μΩ·m or 1.0 μΩ·m. The following shows the resistivity of various materials.

[0044] · Rhenium metal: 0.2 μΩ·m

[0045] · Graphite: 5 - 15 μΩ·m

[0046] · Glassy carbon: 42 μΩ·m

[0047] (Heater)

[0048] The heaters 5a and 5b are formed of a material having a high resistivity and generate heat by energization. The resistivity of the materials constituting the heaters 5a and 5b is preferably 500 - 1000 μΩ·m, more preferably 600 - 900 μΩ·m. By making the resistivity of this material 500 μΩ·m or more, there is a tendency to be able to sufficiently heat the electron source 1 by energization. On the other hand, by making the resistivity of this material 1000 μΩ·m or less, there is a tendency to be able to energize sufficiently. Examples of the materials constituting the heaters 5a and 5b include pyrolytic graphite and hot-pressed carbon. It should be noted that the resistivity (representative value) of pyrolytic graphite is 800 μΩ·m.

[0049] The resistivity value R of the heaters 5a and 5b H is preferably sufficiently larger than the resistivity value R of the intermediate members 2a and 2b. The resistivity value R of the heaters 5a and 5b I is preferably sufficiently larger than the resistivity value R of the intermediate members 2a and 2b. The resistivity value R of the heaters 5a and 5b H relative to the resistivity value R of the intermediate members 2a and 2b I The ratio (R H / R I ) is, for example, 12 - 20, and it can also be 13 - 19 or 14 - 18. By making this ratio 12 or more, there is a tendency that the temperature of the heaters 5a and 5b during energization can be made sufficiently high, and the evaporation of the material constituting the electron source 1 onto the vicinity of the heaters 5a and 5b can be suppressed. On the other hand, by making this ratio 20 or less, there is a tendency to be able to reduce the power loss for heating the heaters 5a and 5b.

[0050] <Second Embodiment>

[0051] Figure 2 Fig. (a) is a longitudinal sectional view schematically showing a transmitter according to the second embodiment. Figure 2 Fig. (b) is Figure 2 a cross-sectional view of the transmitter shown in Fig. (a). In the transmitter 20 shown in these figures, it is different from the transmitter 10 according to the first embodiment in that the four side surfaces of the columnar portion of the electron source 1 are covered by the intermediate member 2. That is, in the first embodiment, the intermediate member 2a is interposed between the electron source 1 and the heater 5a, and the intermediate member 2b is interposed between the electron source 1 and the heater 5b. In contrast, in the present embodiment, the intermediate member 2 is interposed between the electron source 1 and the heaters 5a and 5b. By covering the four side surfaces of the columnar portion of the electron source 1 with the intermediate member 2, effects such as suppressing the diffusion of the evaporant of the electron source and making the heating of the electron source uniform can be achieved. It should be noted that the material of the intermediate member 2 may be the same as that of the intermediate members 2a and 2b according to the first embodiment.

[0052] <Third Embodiment>

[0053] Figure 3 Fig. (a) is a longitudinal sectional view schematically showing a transmitter according to the third embodiment. Figure 3 Fig. (b) is Figure 3 a cross-sectional view of the transmitter shown in Fig. (a). In the transmitter 30 shown in these figures, the intermediate member 3 is composed of a columnar portion 3a and a conical portion 3b. An opening 4 is provided at the front end of the conical portion 3b, and the electron source 1 is inserted into the opening 4. The front surface of the electron source 1 is the electron emission surface 1f. It should be noted that the material of the intermediate member 3 may be the same as that of the intermediate members 2a and 2b according to the first embodiment.

[0054] In the present embodiment, the shape of the electron source 1 is a quadrangular prism (see Figure 3 Fig. (a) and Figure 3 Fig. (b)). The length of the electron source 1 is, for example, 0.1 to 1 mm, and may also be 0.2 to 0.6 mm or 0.3 mm. By making the length 0.1 mm or more, there is a tendency for it to be easier to operate, and by making the length 1 mm or less, there is a tendency for it to be less likely to introduce cracks or the like. The cross-sectional shape of the electron source 1 is substantially square. Its side length is, for example, 20 to 300 μm, and may also be 50 to 150 μm or 100 μm.

[0055] In the present embodiment, the shape of the columnar portion 3a of the intermediate member 3 is a quadrangular prism (see Figure 3 Fig. (a) and Figure 3(b)). The cross-sectional shape of the columnar portion 3a is substantially square. Its side length is, for example, 0.5 to 2 mm, and it can also be 0.6 to 1 mm or 0.7 to 0.9 mm.

[0056] By covering the surfaces other than the electron emission surface of the electron source 1 with the intermediate member 3, the emission of electrons from the surfaces other than the electron emission surface can be suppressed. The front end of the electron source 1 may or may not protrude from the front end of the conical portion 3b of the intermediate member 3, and it is preferably not to protrude. By not allowing the front end of the electron source 1 to protrude from the intermediate member 3, the emission of unnecessary electrons, that is, the emission of electrons to the side, can be sufficiently suppressed. For example, in order to obtain electrons with a larger current, the front end portion of the electron source 1 is heated to a high temperature of about 1550 °C and a high electric field of several kV is applied to the electron source 1. When such a high electric field is applied, extra electrons are also generated from parts other than the front end portion of the electron source. These extra electrons may reduce the brightness of the electron beam from the front end portion due to the space charge effect or cause unnecessary heating of the surrounding electrode components. To prevent the above situation, only the surface of the front end of the electron source 1 can be exposed, and the other surfaces can be covered with the intermediate member 3, thereby obtaining only a high-brightness electron beam from the front end portion. It should be noted that the front end of the electron source 1 may also be recessed with respect to the front end of the conical portion 3b of the intermediate member 3.

[0057] By covering the entire side surface of the electron source 1 with the intermediate member 3, an effect of suppressing the occurrence of a phenomenon called microdischarge can also be achieved. That is, in thermionic emission, electrons are emitted by heating the electron source to a high temperature. Along with this, when the electron emission material evaporates, it adheres to the surrounding electrode components and forms fibrous crystals called whiskers. If charges accumulate in these whiskers, microdischarge will occur. Microdischarge is an important factor that makes the electron beam unstable and reduces the device performance. By covering the entire side surface of the electron source 1 with the intermediate member 3, the sublimated electron emission material is trapped by the intermediate member 3, and the amount of adhesion to the surrounding electrode components can be reduced, so that microdischarge is not likely to occur. It should be noted that the intermediate member 3 covers the entire side surface of the electron source 1 and does not have a notch at a part of the circumferential direction. Since the intermediate member 3 does not have a notch, the emission of electrons to the side can be sufficiently suppressed.

[0058] As described above, the embodiments of the present disclosure have been described in detail, but the present invention is not limited to the above embodiments. For example, in the above embodiments, an electron source having a columnar portion with a substantially square cross-sectional shape is exemplified, but the cross-sectional shape of the columnar portion may also be a substantially polygon other than a substantially square, for example, it may be a substantially rectangle, a substantially rhombus, a substantially parallelogram, a substantially triangle (e.g., a substantially equilateral triangle), or a substantially regular hexagon. The cross-sectional shape of the opening portion 4 in the third embodiment may also not be the same as the cross-sectional shape of the electron source, for example, it may be a substantially circular shape, a substantially rhombus, a substantially parallelogram, a substantially triangle (e.g., a substantially equilateral triangle), or a substantially regular hexagon.

[0059] Example

[0060] Hereinafter, the present disclosure will be described based on examples and comparative examples. It should be noted that the present invention is not limited to the following examples.

[0061] (Example)

[0062] A transmitter having the same configuration as the transmitter shown in Figure 1 was fabricated using the materials shown in Table 1. The length of the electron source was about 0.3 mm, and the length of one side of the columnar portion was about 100 μm. The thickness of the intermediate member (the distance between the electron source and the heater) was set to 300 μm.

[0063] [Table 1]

[0064]

[0065] The transmitter was energized by constant current control so that the temperature of the electron source became 1550 °C. As a result, the temperature of the heater was 1768 °C. Figure 4 This is a thermal imaging camera image showing the upper surface temperature of the transmitter according to the example. According to the research of the inventors of the present application, from the viewpoint of preventing the evaporation of lanthanum boride, it is preferable that when the electron source is heated to 1550 °C, the temperature of the heater is 1700 - 1800 °C.

[0066] (Comparative Example)

[0067] A transmitter having the same configuration as the example except that no intermediate member was disposed between the electron source and the heater was fabricated (see Figure 5 (a)). The transmitter was energized by constant current control so that the temperature of the electron source became 1550 °C. As a result, the temperature of the heater was 1634 °C.

[0068] Industrial Applicability

[0069] According to the present disclosure, a transmitter and a device including the same that can maintain high reliability even during long-term operation can be provided.

[0070] Explanation of reference numerals

[0071] 1… electron source, 1f… electron emission surface, 2, 2a, 2b, 3… intermediate members, 5a, 5b… heaters, 10, 20, 30… emitters

Claims

1. A transmitter, comprising: a first heater and a second heater, which generate heat when energized; an electron source composed of a first material that releases electrons when heated by the first heater and the second heater; an intermediate member interposed between the first heater and the second heater and the electron source respectively, and composed of a second material having a lower thermal conductivity than the first material; and a pair of conductive supports disposed outside the first heater and the second heater in a manner that clamps the first heater and the second heater, the electron source, and the intermediate member, and the pair of conductive supports energize the first heater and the second heater, the length of the shortest path of the intermediate member through which electrons pass when going from the heater to the electron source is 100 μm to 1000 μm.

2. The transmitter according to claim 1, wherein, the resistivity value of the intermediate member is 300 μΩ·m or less, the resistivity value of the heater is 500 μΩ·m or more.

3. The transmitter according to claim 1 or 2, wherein, the second material is at least one material selected from carbon, boron carbide, boron nitride, and rhenium.

4. The transmitter according to claim 1 or 2, wherein, the second material is glassy carbon.

5. The transmitter according to claim 1 or 2, wherein, the first material is one material selected from the group consisting of rare earth borides, high melting point metals and their oxides, carbides and nitrides, and noble metal-rare earth alloys.

6. The transmitter according to claim 1 or 2, wherein, the intermediate member covers the surfaces other than the electron emission surface of the electron source.

7. An apparatus comprising the transmitter according to any one of claims 1 to 6.

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