Emitter

Abstract

This emitter comprises: an insulator; a pair of terminals extending along a predetermined direction and fixed to the insulator so as to be separated from each other; a filament fixed to the pair of terminals; and a chip part formed of an electron emission material and fixed to the filament. Each of the pair of terminals has a fixed surface, and the fixed surface protrudes or is recessed in a direction perpendicular to a predetermined direction at the terminal with respect to a surface located on the insulator side of the fixed surface in the predetermined direction. The filament is fixed to the pair of terminals on the fixed surface. When the protruding height from the pair of terminals of the filament in the predetermined direction is designated as H and the length of the fixed surface in the predetermined direction is designated as L, L / H is 0.4 or less.

Description

Emitter

[0001] One aspect of the present disclosure relates to an emitter.

[0002] Patent Document 1 describes an emitter including an insulator, a pair of terminals fixed to the insulator, a filament fixed to the pair of terminals, and a tip fixed to the filament. In this emitter, the tip is heated by passing current through the filament via the terminals, and an electron beam is emitted from the tip.

[0003] WO2009 / 044871 publication

[0004] The emitter described above can be used in, for example, an electron microscope. In this case, if the filament vibrates due to resonance, the electron beam cannot be stably supplied, which may result in a decrease in the resolution of the electron microscope. Therefore, the emitter is required to suppress the resonant vibration of the filament and stably supply the electron beam.

[0005] Therefore, an object of one aspect of the present disclosure is to provide an emitter that can stably supply an electron beam.

[0006] An emitter according to one aspect of the present disclosure is [1] "an emitter comprising: an insulator; a pair of terminals extending along a predetermined direction and fixed to the insulator at a distance from each other; a filament fixed to the pair of terminals; and a tip portion formed of an electron emitting material and fixed to the filament, each of the pair of terminals having a fixing surface that protrudes or is recessed in a direction perpendicular to the predetermined direction with respect to a surface of the terminal that is located on the insulator side of the fixing surface in the predetermined direction; the filament being fixed to the pair of terminals at the fixing surface; and wherein, where H is a protruding height of the filament from the pair of terminals in the predetermined direction and L is a length of the fixing surface in the predetermined direction, L / H is 0.4 or less."

[0007] In an emitter, the portion consisting of the filament and tip may vibrate due to resonance. Therefore, in order to stably supply an electron beam, it is considered to increase the resonant frequency of this portion and suppress the occurrence of vibration due to resonance. In this case, it is considered to shorten the filament (reducing its protruding height from the terminal). This shortens the pendulum length of the portion consisting of the filament and tip, thereby increasing the resonant frequency of this portion. However, the present inventors have found that even if the filament is made short, simply fixing the filament to the terminal may not achieve the desired resonant frequency. For example, if the filament is fixed to the terminal by welding, fine adjustment of the welding position is difficult, and therefore the fixing position of the filament relative to the terminal may vary. In this case, some of the resulting emitters may have a long filament length (the above-mentioned pendulum length) and a resonant frequency outside the desired range. Therefore, in the emitter [1], each of the pair of terminals has a fixing surface that protrudes or is recessed in a direction perpendicular to the predetermined direction with respect to the surface of the fixing surface located on the insulator side of the terminal in a predetermined direction, and the filament is fixed to the pair of terminals at the fixing surface. This suppresses variations in the fixing position of the filament relative to the terminals, enabling the desired resonance characteristics to be stably obtained. Furthermore, in the emitter [1], where H is the protruding height of the filament from the pair of terminals in a predetermined direction and L is the length of the fixing surface in the predetermined direction, L / H is 0.4 or less. Although variations in the fixing position of the filament relative to the fixing surface may occur by the length L of the fixing surface, by reducing the length L of the fixing surface in this manner, the desired resonance characteristics can be stably obtained regardless of the fixing position of the filament relative to the fixing surface. Therefore, with the emitter [1], vibrations due to resonance can be reliably suppressed, enabling the stable supply of electron beams.

[0008] The emitter according to one aspect of the present disclosure may be [2] "the emitter according to [1], in which L / H is 0.2 or more." In this case, the length L of the fixing surface can be ensured, and the workability of fixing the filament to the fixing surface can be ensured.

[0009] An emitter according to one aspect of the present disclosure may be [3] "the emitter according to [1] or [2], wherein the fixing surface is formed on an end of the terminal opposite the insulator." In this case, fixing of the filament to the fixing surface can be facilitated. Furthermore, the length of the filament can be shortened, thereby improving resonance characteristics.

[0010] An emitter according to one aspect of the present disclosure may be [4] "the emitter according to any one of [1] to [3], wherein the surface of the terminal is a bottom surface of a groove formed in the terminal, and the fixing surface protrudes in a direction perpendicular to the predetermined direction relative to the bottom surface of the groove." An emitter according to one aspect of the present disclosure may be [5] "the emitter according to any one of [1] to [3], wherein the terminal has a protrusion that protrudes in a direction perpendicular to the predetermined direction relative to another portion of the terminal, and the fixing surface is a surface of the protrusion." An emitter according to one aspect of the present disclosure may be [6] "the emitter according to any one of [1] to [3], wherein the fixing surface is a bottom surface of a groove or recess formed in the terminal, and is recessed in a direction perpendicular to the predetermined direction relative to the surface." In the cases of [4] to [6], vibration due to resonance can also be reliably suppressed, and an electron beam can be stably supplied.

[0011] According to one aspect of the present disclosure, it is possible to provide an emitter that can stably supply an electron beam.

[0012] It is a front view of the emitter of the embodiment. It is a plan view of the emitter. It is a schematic perspective view of the emitter. It is a schematic perspective view of the emitter according to the first modified example. It is a schematic perspective view of the emitter according to the second modified example.

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be designated by the same reference numerals, and redundant description will be omitted.

[0014] As shown in FIGS. 1 to 3 , the emitter 1 includes an insulator 2, a pair of terminals 3, a filament 4, and a tip portion 5 (electron source). The emitter 1 is, for example, a thermal field emission type emitter. The emitter 1, together with a suppressor electrode, an extraction electrode, and the like, constitutes an electron gun and can be used in electron microscopes, semiconductor manufacturing equipment, inspection equipment, processing equipment, and the like. In the emitter 1, the tip portion 5 is heated by passing current through the pair of terminals 3 to the filament 4, and an electron beam is emitted from the tip of the tip portion 5. The emitter 1 may also be a cold field emission type emitter. The following description will be made with reference to the X direction, the Y direction perpendicular to the X direction, and the Z direction (predetermined direction) perpendicular to the X and Y directions shown in each figure. Note that the filament 4 and tip portion 5 are omitted in FIG. 3 , and only one of the pair of terminals 3 is shown.

[0015] The insulator 2 is formed, for example, in a substantially cylindrical shape from an insulating material. The terminal 3 is formed, for example, in a rod shape from a metal material such as tungsten, titanium, kovar, or niobium. In this example, the terminal 3 is formed in a cylindrical shape and extends straight along the Z direction. The terminal 3 penetrates the insulator 2 along the Z direction and is fixed to the insulator 2 at its middle portion. The terminal 3 has a protrusion 31 that protrudes from the insulator 2 to one side in the Z direction (the upper side in each drawing). The pair of terminals 3 face each other at a distance in the X direction.

[0016] The filament 4 is formed in an arch shape, extends between the pair of terminals 3, and is fixed at both ends to the pair of terminals 3. The filament 4 has an apex 41 and a pair of extension portions 42 that extend from the apex 41 toward both ends. The apex 41 is curved so as to be convex toward one side in the Z direction (the side opposite the insulator 2 and terminal 3). In this example, the extension portions 42 extend straight. The filament 4 is fixed to the protrusions 31 of each terminal 3 at the extension portions 42. The extension portions 42 are fixed to the protrusions 31 by, for example, spot welding. Details of the fixing of the filament 4 to the terminals 3 will be described later.

[0017] The filament 4 is made of, for example, a high-melting-point metal having a melting point of 2200° C. or higher. In this example, the filament 4 is made of tungsten. Other examples of the material of the filament 4 include an alloy of tungsten and a high-melting-point metal (e.g., rhenium). The material of the filament 4 may also be tungsten doped with an alkali metal (e.g., potassium) for tissue stabilization.

[0018] The tip portion 5 is fixed to the top 41 of the filament 4. The tip portion 5 is formed, for example, in a rod (needle) shape from an electron-emitting material. Examples of materials for the tip portion 5 include high-melting-point metals such as tungsten, tantalum, and hafnium, as well as their oxides, carbides, and nitrides, rare-earth borides such as lanthanum boride (LaB6) and cerium boride (CeB6), and precious metal-rare earth alloys such as iridium-cerium. In this example, the tip portion 5 is fixed so as to extend along the Z direction.

[0019] The details of the fixation of the filament 4 to the terminal 3 will now be described. The protrusion 31 of each terminal 3 has a fixation surface 32 to which the filament 4 is fixed. In this example, a groove 33 extending along the X direction is formed in the protrusion 31, and the surface of the terminal 3 located on one side of the groove 33 in the Z direction (upper side in the figure) serves as the fixation surface 32. That is, the fixation surface 32 is a part of the surface of the terminal 3, and in this example, is a cylindrically curved surface. The fixation surface 32 is formed on the end 3a of the terminal 3 (protrusion 31) opposite the insulator 2. The groove 33 is formed, for example, in a rectangular shape in a cross section perpendicular to the X direction. The groove 33 is formed so as to penetrate the terminal 3 along the X direction (throughout the entire terminal 3 in the X direction). The fixation surface 32 may be a flat surface perpendicular to the Y direction. For example, the terminal 3 may be processed so that the fixation surface 32 is flat.

[0020] The filament 4 is fixed to one side in the Y direction (the front side of the paper in FIG. 1, the bottom side in FIG. 2) of the terminal 3 located on one side in the X direction (the right side in FIGS. 1 and 2), and is fixed to the other side in the Y direction (the back side of the paper in FIG. 1, the top side in FIG. 2) of the terminal 3 located on the other side in the X direction (the left side in FIGS. 1 and 2). That is, the fixing surface 32 and the groove 33 are provided on one side in the Y direction of the terminal 3 on one side in the X direction, and on the other side in the Y direction of the terminal 3 on the other side in the X direction. As a result, as shown in FIG. 2, the tip portion 5 is positioned between the pair of terminals 3 when viewed from the Z direction.

[0021] The fixing surface 32 protrudes in the Y direction relative to the bottom surface 33a of the groove portion 33. The bottom surface 33a is a surface of the terminal 3 that is located on the insulator 2 side of the fixing surface 32 in the Z direction (the lower side in each drawing), and is adjacent to the fixing surface 32 in the Z direction. In the terminal 3 located on one side in the X direction (the right side in FIGS. 1 and 2), the fixing surface 32 protrudes to one side in the Y direction (the front side of the paper in FIG. 1, the lower side in FIG. 2) relative to the bottom surface 33a of the groove portion 33, and in the terminal 3 located on the other side in the X direction (the left side in FIGS. 1 and 2), the fixing surface 32 protrudes to the other side in the Y direction (the back side of the paper in FIG. 1, the upper side in FIG. 2) relative to the bottom surface 33a of the groove portion 33.

[0022] The filaments 4 are fixed to the terminals 3 at the fixing surfaces 32 by welding. That is, the fixing surfaces 32 function as welding surfaces for welding the filaments 4 to the terminals 3.

[0023] If the protruding height of the filament 4 from the terminal 3 in the Z direction is H and the length (maximum length) of the fixing surface 32 in the Z direction is L (FIG. 1), the ratio of the protruding height H of the filament 4 to the length L of the fixing surface 32, L / H, is 0.2 or more and 0.4 or less. As an example, the protruding height H of the filament 4 is about 1.5 mm, and the length L of the fixing surface 32 is about 0.4 mm. In this case, L / H is 0.27. L / H is preferably 0.3 or less. The length L of the fixing surface 32 is, for example, 0.6 mm or less, and preferably 0.5 mm or less. [Operation and Effects]

[0024] In the emitter 1, each terminal 3 has a fixing surface 32 that protrudes in the Y direction (a direction perpendicular to the Z direction) from the bottom surface 33a of the groove 33 (the surface of the terminal 3 that is located on the insulator 2 side of the fixing surface 32 in the Z direction), and the filament 4 is fixed to each terminal 3 at the fixing surface 32. This suppresses variation in the fixing position of the filament 4 relative to the terminal 3, thereby stably achieving desired resonance characteristics. Furthermore, in the emitter 1, where H is the protruding height of the filament 4 from the terminal 3 in the Z direction and L is the length of the fixing surface 32 in the Z direction, L / H is 0.4 or less. Although variation in the fixing position of the filament 4 relative to the fixing surface 32 may occur by the length L of the fixing surface 32, by reducing the length L of the fixing surface 32 in this manner, desired resonance characteristics can be stably achieved regardless of the fixing position of the filament 4 relative to the fixing surface 32. That is, in the above embodiment, the fixing position of the filament 4 relative to the terminal 3 can be reliably controlled within a range from the end 3a of the terminal 3 to the length L of the fixing surface 32 or less. Therefore, according to the emitter 1, it is possible to reliably suppress vibrations due to resonance and to stably supply electron beams.

[0025] The ratio L / H is 0.2 or more. This ensures the length L of the fixing surface 32, and ensures the ease of fixing (welding) the filament 4 to the fixing surface 32.

[0026] The fixing surface 32 is formed on the end 3a of the terminal 3 opposite to the insulator 2. This makes it easier to fix (weld) the filament 4 to the fixing surface 32. Furthermore, the length of the filament 4 can be shortened, improving the resonance characteristics.

[0027] The fixing surface 32 protrudes in the Y direction from the bottom surface 33a of the groove 33. In this case, vibration due to resonance can also be reliably suppressed, and the electron beam can be supplied stably. [Modification]

[0028] The fixing surface 32 may be configured as shown in Fig. 4 or Fig. 5. In Fig. 4 and Fig. 5, similarly to Fig. 3, the filament 4 and the tip portion 5 are omitted, and only one of the pair of terminals 3 is shown.

[0029] In a first modified example shown in Fig. 4, the terminal 3 has a cylindrical main body 35 and a protruding portion 36 that protrudes in the Y direction relative to the main body 35 (other portions of the terminal 3). The protruding portion 36 is formed, for example, in a rectangular parallelepiped shape, and protrudes from the main body 35 along its entire periphery when viewed in the Z direction. In the first modified example, the fixing surface 32 is a flat surface formed by the surface of the protruding portion 36. The fixing surface 32 protrudes in the Y direction relative to the surface (cylindrical surface) of the main body 35 (the surface of the terminal 3 that is located on the insulator 2 side of the fixing surface 32 in the Z direction).

[0030] 5, a recess 37 is formed in the end 3a of the terminal 3 (protrusion 31) opposite the insulator 2, and the bottom surface 37a of the recess 37 forms the fixing surface 32. In this case, the fixing surface 32 is recessed in the Y direction with respect to the surface (cylindrical surface) of the terminal 3 that is located on the insulator 2 side of the fixing surface 32 in the Z direction. The recess 37 is formed in a semicircular shape when viewed from the Z direction, for example, and the bottom surface 37a is a rectangular flat surface.

[0031] The first and second modified examples also reliably suppress vibrations due to resonance and stably supply electron beams. In the first modified example, the protrusion 36 may have any shape. In the second modified example, a groove may be formed in the terminal 3 instead of the recess 37, and the fixing surface 32 may be formed by the bottom surface of the groove. In other words, in the example of FIG. 3 , the fixing surface 32 may be formed by the bottom surface 33 a of the groove 33.

[0032] The present disclosure is not limited to the above-described embodiment and modified examples. For example, the materials and shapes of each component are not limited to those described above, and various materials and shapes can be used. In the above-described embodiment, the fixing surface 32 is provided on one side in the Y direction for the terminal 3 on one side in the X direction, and on the other side in the Y direction for the terminal 3 on the other side in the X direction. However, the fixing surface 32 may be provided on the same side in the Y direction for a pair of terminals 3. That is, both ends of the filament 4 may be fixed on one side in the Y direction relative to the pair of terminals 3.

[0033] In the above embodiment, the emitter 1 includes one filament 4 (first filament 4), but it may also include multiple (e.g., two) filaments 4. In this case, for example, each terminal 3 has fixing surfaces 32 on both sides in the Y direction, and the second filament 4 is fixed to the fixing surface 32 opposite to the fixing surface 32 to which the first filament 4 is fixed. The second filament 4 supports the tip portion 5 from the side opposite to the first filament 4. That is, for example, the tip portion 5 may be fixed to the top portion 41 of each of the first filament 4 and the second filament 4, and the tip portion 5 may be supported so as to be sandwiched between these top portions 41 in the Y direction.

[0034] 1...emitter, 2...insulator, 3...terminal, 3a...end, 4...filament, 5...tip portion, 32...fixing surface, 33...groove portion, 33a...bottom surface, 36...protrusion portion, 37...recess, 37a...bottom surface.

Claims

1. An emitter comprising: an insulator; a pair of terminals extending along a predetermined direction and fixed to the insulator with a space between them; a filament fixed to the pair of terminals; and a tip portion formed of an electron emitting material and fixed to the filament, each of the pair of terminals having a fixing surface that protrudes or is recessed in a direction perpendicular to the predetermined direction with respect to a surface of the fixing surface that is located on the insulator side in the predetermined direction of the terminal, the filament being fixed to the pair of terminals at the fixing surface, and wherein, where H is a protruding height of the filament from the pair of terminals in the predetermined direction and L is a length of the fixing surface in the predetermined direction, L / H is 0.4 or less.

2. The emitter of claim 1, wherein L / H is 0.2 or greater.

3. The emitter according to claim 1 or 2, wherein the fixing surface is formed on an end of the terminal opposite to the insulator.

4. An emitter as claimed in claim 1 or 2, wherein the surface of the terminal is a bottom surface of a groove formed in the terminal, and the fixing surface protrudes in a direction perpendicular to the predetermined direction relative to the bottom surface of the groove.

5. An emitter according to claim 1 or 2, wherein the terminal has a protruding portion that protrudes in a direction perpendicular to the predetermined direction relative to other portions of the terminal, and the fixing surface is a surface of the protruding portion.

6. The emitter according to claim 1 or 2, wherein the fixing surface is a bottom surface of a groove or recess formed in the terminal, and is recessed in a direction perpendicular to the predetermined direction with respect to the surface.