Cold cathode electron source

Abstract

PURPOSE: To achieve a cold cathode electron gun that includes a cold field emitter capable of stably and easily maintaining an ultra-bright state for 10 hours or more necessary for factory operations, etc., regarding a cold cathode electron source with high brightness and long life.CONSTITUTION: A cold cathode electron source includes: an emitter with a sharp tip, for emitting an electron beam; a holed extractor for applying an electric field to the tip of the emitter to extract an electron beam; a heated elastic body for holding and flushing the emitter; and a support post for supporting the elastic body and supplying a power supply to heat. The elastic body is fixed to the support post disposed at a symmetrical position around the emitter and configured to shrink during flushing to reduce the drift of the emitter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cold cathode electron source having a high-brightness, long-life cold cathode. [Background technology]

[0002] Electron beam equipment is widely used in semiconductor device manufacturing and control as electron beam exposure equipment, CDSEM, high-speed inspection equipment, and repair equipment. Electron beams are obtained by accelerating electrons, a type of negatively charged elementary particle generated by an electron gun. Because the de Broglie wavelength is short (sub-angstrom) and can be focused to a nanometer-order spot, electron beams are essential for the manufacturing and high-speed inspection of cutting-edge semiconductor devices that require nanometer-order microfabrication.

[0003] Following Moore's Law, semiconductor devices are becoming increasingly miniaturized and integrated every year. Although there has been a tendency toward saturation in recent years, the number of semiconductor elements formed on a single photomask or wafer continues to increase. Currently, more than one trillion transistors with a minimum linewidth of tens of nanometers or less are formed on a single wafer. The most advanced GPUs used in generative AI have as many as 100 billion transistors per semiconductor device. Furthermore, the number of semiconductors used continues to increase rapidly due to the construction of data centers to run generative AI applications.

[0004] Manufacturing or inspecting these devices using electron beam equipment requires a fairly high throughput. The throughput of an inspection system is determined by the image acquisition speed. It is said that 10 to 1000 electrons per pixel are required to acquire an image with an SNR that can be used for inspection. In order to increase the throughput, it is necessary to increase the number of electrons that can be irradiated per pixel per unit time.

[0005] The electron beam emitted from the electron source is focused by a lens into a small spot and irradiated onto the sample surface. The maximum current density that can be supplied by a single electron gun is determined by the maximum brightness of the electron source. As long as current electron guns are used, no matter how much the electron beam optics are improved to eliminate aberration, the maximum number of electrons that can be irradiated per unit area and time is determined by the maximum brightness of the electron source, and there is a limit to how much throughput can be improved.

[0006] Currently, thermal-field electron guns, which use a sharp tungsten needle with diffused zirconium (TFE), are widely used. This electron gun was invented approximately 40 years ago. The tip of the sharpened tungsten needle is heated to approximately 1700 Kelvin, where it is coated with a thin film of diffused zirconium, lowering the work function and achieving high brightness. Electrons are emitted by applying a voltage of 3 kV or more to the emitter tip. Gases present around the emitter are not easily adsorbed by the ultra-high temperature emitter, making it less susceptible to influence from surrounding gases. The output current is very stable and has low noise, allowing for continuous use for years until the zirconium is depleted. However, because it is used at temperatures above 1700 Kelvin, thermal disturbances cause an electron beam energy distribution of approximately 1 eV. Furthermore, because the beam emission area is relatively large (micron-sized), it is difficult to focus the electron beam to a small spot on the order of a few nanometers at low energy.

[0007] On the other hand, there is the cold field emitter (CFE), which can achieve more than three times the brightness of TFE. As the name suggests, a cold field emitter is an electron source that emits electrons by applying a high electric field to a sharp tungsten needle at room temperature. CFEs have a much older history than TFEs. Because they emit electrons at room temperature, the energy distribution of the emitted electrons is narrower (approximately 0.3 eV), less than half that of TFEs. This makes them less susceptible to the chromatic aberrations inherent in electron beam optics, allowing the electron beam to be focused to a smaller spot than TFEs for the same electron beam energy. Furthermore, because the electron beam generation point is narrower (several tens of nanometers) than TFEs, when using electron optics with a large reduction ratio, the source size becomes negligible, resulting in higher brightness. Cooling the needle tip with liquid nitrogen or other cooling devices reduces the energy dispersion of the electron beam due to thermal aberration, thereby narrowing the energy distribution to a few tens of millivolts.

[0008] With conventional cold field emitters, an ultra-bright region appears immediately after startup, producing brightness more than 10 times that of TFE. However, within a few minutes, gas adsorption occurs at the tip of the emitter, causing the brightness to decay to about one-tenth of its original brightness. After this, a stable region appears for a while, where the brightness does not change. After the stable region appears, the applied voltage can be increased slightly to achieve brightness about three times that of TFE.

[0009] Conventional cold field emitters utilize this stable region. After a few hours, hydrogen adsorption to the emitter gradually increases, causing the work function to fluctuate, resulting in current fluctuations and instability, eventually causing electron emission to cease.

[0010] Each time, a reactivation process called flashing is performed, in which the emitter tip is heated to a high temperature of over 1000°C for a few seconds to release the adsorbed hydrogen. Flashing restores brightness, but each time flashing is performed, the emitter tip melts and curls, increasing the radius of curvature and reducing the effective electric field generated at the emitter tip even when the same voltage is applied.

[0011] To compensate for this defect, electron emission is restarted by gradually increasing the applied voltage. Each time flashing is repeated, the applied voltage required to obtain the same emission increases. If the applied voltage is increased continuously, eventually the voltage applied to the emitter tip will exceed the vacuum breakdown voltage, causing an arc discharge at the emitter tip, completely damaging the emitter and reaching the end of its life. This is the life cycle of a conventional CFE.

[0012] Cold field emitters were known long before the invention of TFE. At the time, the limit of vacuum technology was ultra-high vacuums of around 10-7 Pascals. Because the current emitted by CFE in ultra-high vacuums was very unstable and produced a lot of noise, its use was limited to research applications requiring ultra-high resolution, and it was completely inapplicable to applications requiring 24 / 7 operation, such as semiconductor device manufacturing plants.

[0013] The turning point came after the non-evaporable getter pump (NEG pump) became practical. Traditionally, ion sublimation pumps had been widely used as a means of achieving ultra-high vacuum in electron beam columns. Ion pumps utilize the titanium sputtering phenomenon to achieve a vacuum by reacting and solidifying reactive titanium with gas molecules floating in the vacuum. This method can achieve a vacuum of about 10-7 Pascals. Most electron microscopes currently in operation that require ultra-high vacuum achieve this using ion pumps. In the days when ion pumps were the only option, TFE and conventional cold field emitters operated at ultra-high vacuums of about 10-7 Pascals.

[0014] On the other hand, NEG pumps operate on a different principle than ion pumps, using a chemically active substance called a getter. Their unique feature is that the pump is first heated to several hundred degrees to activate the getter. After activation, when the pump cools, gas molecules floating in the vacuum are adsorbed and solidified by the getter, thereby exhibiting pumping action. This pump continues to pump even when the power is disconnected. This pump can ultra-fastly pump hydrogen molecules and carbon monoxide, which ion pumps cannot pump, and easily achieve ultra-high vacuums of 10-9 Pascals or higher. In other words, it can reach ultra-high vacuum regions unattainable with conventional ion pumps. Its particular value lies in its ability to create a vacuum free of hydrogen, carbon monoxide, or both. Ultra-compact combined pumps capable of both ion and NEG pumping are now available. With sufficient bakeout and a combined NEG pump, ultra-high vacuums of 10-10 Pascals or higher can be achieved.

[0015] In an extremely high vacuum state, the number of gas molecules colliding with the tip of the cold field emitter is drastically reduced, reducing the adsorption of hydrogen molecules, carbon monoxide, or both, which increase the work function, making the cold field emitter operation extremely stable. It is now possible to use an ultra-high brightness region that is more than 10 times brighter than the stable region used by conventional cold field emitters. Experiments have shown that if the degree of vacuum is increased to 10-10 Pa or higher, the ultra-high brightness state can be maintained for several hours or more. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0016] However, as explained above, although the time during which the ultra-high brightness state can be maintained has become longer than in the past, there remains the problem that the time during which the ultra-high brightness state can be maintained is still one order of magnitude or more shorter than that required for use in semiconductor device manufacturing.

[0017] Furthermore, reactivating the emitter requires operations such as flashing, which damages the emitter tip, and immediately after flashing, the emitter tip condition changes, causing the electron beam emission position to shift. This change in electron emission position necessitates time-consuming readjustment of the electron beam column, which prevents the device from being used continuously. Another issue is the difficulty of fully automating flashing for emitters that change over time. [Means for solving the problem]

[0018] In order to solve the above-mentioned problems, the present invention aims to realize a cold cathode electron gun having a cold field emitter that can stably and easily maintain an ultra-high brightness state for 10 hours or more, which is necessary for factory operations, etc.

[0019] Therefore, the present invention provides a cold cathode electron source that extracts an electron beam from an emitter, The device comprises an emitter with a pointed tip that emits an electron beam, an extractor with a hole that applies an electric field to the tip of the emitter to extract the electron beam, a heating elastic body for holding and flashing the emitter, and a support that supplies power to support and heat the elastic body. The elastic body is fixed to the support that is positioned symmetrically around the emitter, and the elastic body expands and contracts during flashing to reduce drift.

[0020] The present invention also provides a cold cathode electron source that extracts an electron beam from an emitter, comprising: an emitter with a pointed tip that emits the electron beam; an extractor with a hole that applies an electric field to the tip of the emitter to extract the electron beam; a heating elastic body for holding and flashing the emitter; a support that supplies power to support and heat the elastic body; and a thermally insulating emitter support part that fixes the part of the emitter opposite to its tip, thereby eliminating or reducing drift of the emitter fixed to the emitter support part during flashing.

[0021] In these cases, the number of elastic bodies and support posts is set to an integral multiple of two.

[0022] Also, the heated portion of the elastic body is eliminated, and the heated portion is provided in the emitter.

[0023] In addition, the tip of the emitter protrudes above the hole in the extractor to reduce the collision of the electron beam with the extractor, thereby reducing gas emission or increasing the efficiency of electron beam utilization.

[0024] The tip of the emitter is shaped like a spot to produce a high-intensity, minute spot, or like a ring to produce a high-intensity, large-current electron beam.

[0025] In addition, a location at a predetermined distance or more from the tip of the emitter is covered with a non-electron emitting body to increase the brightness of the electron beam emitted from the tip or to reduce the decrease in brightness due to flashing.

[0026] Furthermore, a pointed emitter is formed on the substrate by deposition or etching. [Effects of the Invention]

[0027] This invention has made it possible to realize a cold cathode electron gun with a cold field emitter that can stably and easily maintain an ultra-high brightness state for 10 hours or more, as required for factory operations, etc. By eliminating the misalignment between the extractor position and the emitter tip position that occurs during flashing, automatic flashing is possible, eliminating the need for electron beam adjustment after flashing.

[0028] In more detail, it is as follows.

[0029] 1 The emitter is held symmetrically by elastic bodies attached to the supports on both sides, and when the elastic bodies are heated by passing electricity through them during flashing, the drift of the emitter tip position relative to the extractor position is reduced, making it possible to stabilize the electron beam.

[0030] 2 The tip of the emitter and the opposite side are fixed with an emitter support, which reduces the drift of the emitter tip position relative to the extractor position when heated by current during flashing, making it possible to stabilize the electron beam.

[0031] 3 By making the tip of the emitter protrude above the hole in the extractor, it is possible to reduce or eliminate the collision of the emitted electron beam with the extractor, thereby reducing gas emissions and increasing the amount of electron beam available for use as probe current.

[0032] 4 The structure can be simplified by passing electricity through the electrically heated part of the emitter to directly heat and flash it.

[0033] 5 By making the tip of the emitter spot-shaped or ring-shaped, it is possible to achieve a high-intensity, minute spot, or a high-intensity, large current.

[0034] 6 By covering the emitter except for the tip with an insulator, it is possible to achieve high brightness and reduce the decrease in brightness due to flashing.

[0035] 7 By depositing or etching the emitter onto the substrate, it is now possible to easily create emitter tips of any shape. Example 1

[0036] FIG. 1 shows a configuration diagram (part 1) of one embodiment of the present invention.

[0037] FIG. 1(a) shows an example of constraints on degrees of freedom, FIG. 1(b) shows a top view, and FIG. 1(c) shows a side view.

[0038] In Figures 1(b) and (c), the filament 1 is a tungsten wire bent upward into a hairpin shape, and is heated by passing electricity through it to heat the emitter 2 fixed to the bent part into a hairpin shape.

[0039] The emitter 2 is a tungsten wire with a sharpened tip, which emits an electron beam from a field.

[0040] The extractor support part 3 holds the extractor 4 .

[0041] The extractor 4 is a disk with a hole in the center, and generates an electric field by applying a voltage between it and the tip of the emitter 2, thereby field-emitting an electron beam.

[0042] The electron beam 5 is an electron beam extracted from the emitter 2 .

[0043] The support member 6 is used to fix the support column 7 and is electrically insulating.

[0044] The supports 7 are electrically conductive supports that are symmetrically arranged to fix the filaments 1 .

[0045] The switch 8 is a switch for passing a current between the two supports 7 to energize and heat the filament during flashing.

[0046] The device state detection device 9 detects whether the device is in a state where flushing is required (for example, detecting a flushing instruction from an operator, or detecting whether the device has reached a preset flushing state).

[0047] The heating power supply 10 is a power supply for energizing and heating the filament 8 .

[0048] The gas vent window 111 is a window for releasing gas within the space where the emitter 2 is located to the outside.

[0049] The field emission power supply 12 is a power supply that applies a voltage between the emitter 2 and the extractor 4 to cause electrons to be field emitted from the tip of the emitter 2 .

[0050] Filament currents A and B are currents that flow through filaments A and B, respectively, fixed between two symmetrically arranged supports 7, and in this case, for example, are currents that flow through filaments A and B that are arranged in the X and Y directions (the axial direction of the electron beam is the Z direction). Here, by arranging two sets of filaments A and B, each fixed to the tip of support 7, in the X and Y directions, when the filaments are heated by passing electricity through them, the amount of thermal expansion or contraction between the support and filament and between the filament and support is approximately the same, so that the drift of emitter 2 fixed at the center is canceled (or reduced), and by arranging it in the X and Y directions, its degree of freedom is eliminated (or reduced) in the X and Y directions, and it is possible to fix it and reduce drift.

[0051] In the example of (a) constraint on the degrees of freedom, as shown in constraint 1 and constraint 2 of the degrees of freedom, by placing filaments AB in the X and Y directions, the drift of emitter 2 in the X and Y directions is restrained 1 and 2, and the drift can be reduced. Here, the filaments are placed in the X and Y directions (placed at right angles), but they can also be placed in any two directions within the XY plane. Since it is sufficient to be able to restrain the position of the emitter tip within the XY plane, similar results can be obtained by supporting it from three points equally spaced at 60 degrees, for example. Any number of additional restraints can be achieved.

[0052] Furthermore, the drift of the tip of the emitter 2 in the Z direction can be ignored because the opening angle in the direction of travel (Z direction) of the electron beam 5 is small, and even if there is drift, the beam size of the electron beam 5 when irradiated onto a mask, etc. does not become significantly larger.

[0053] Furthermore, the drift that occurs when a filament is heated by passing electricity through it can be divided into short-term drift and long-term drift. The former, short-term drift, is the drift at the tip of the emitter 2 caused by the expansion and contraction of the filament when it is heated by passing electricity through it (for example, 2 to 20 seconds, or even longer (the optimum value is determined through experiments)). On the other hand, the latter, long-term drift, is the drift that occurs when the temperature gradually rises and falls (and distortion is eliminated) due to thermal conduction or thermal radiation from the filament when it is heated by passing electricity through the support 7, the support member 6, and so on, and continues for an extremely long period of time. Here, both types of drift are referred to as drift.

[0054] Next, the configuration of FIG. 1 will be briefly explained.

[0055] (1) Figure 1 shows an example of an emitter of the present invention that uses a single-crystal tungsten needle. Tungsten has a high melting point of approximately 3400°C, making it an excellent field emitter material. Its work function is also not particularly high, at 4.54 eV. Furthermore, by using a crystal plane such as the 310 plane, a single sharp tip structure can be easily created. The desired tip shape can be obtained by mechanical polishing and electrolytic polishing.

[0056] (2) This tungsten needle is fixed to the support 7 by a filament that also serves as a heater. The filament and tungsten needle are welded together. Conventionally, the tungsten needle was fixed to the support 7 by two filaments, but in the present invention, it is fixed by two symmetrically arranged filaments to prevent the needle from moving during flashing. Although four filaments are used in Figure 1, three filaments are also possible as long as they are arranged symmetrically, with one common electrical wiring. The number can also be a multiple of two.

[0057] Figure 2 shows a configuration diagram (part 2) of one embodiment of the present invention. In this Figure 2, the emitter 2 of Figure 1 is fixed as emitter 21 by the emitter support part 22 of Figure 2, thereby reducing drift. In addition, a secondary electron absorbing film 4-1 is provided on the bottom surface of the extractor 4 shown in the figure, thereby reducing gas emission due to irradiation with an electron beam. This will be explained below.

[0058] FIG. 2(a) shows an example of constraints on degrees of freedom, FIG. 2(b) shows a top view, and FIG. 2(c) shows a side view.

[0059] 2(b) and (c), the elastic body 11 corresponds to the filament 1 in Fig. 1 and is an elastic body (for example, a spring-like body made of tungsten) that expands and contracts when heated by passing current through it. The elastic body in this embodiment is not directly related to the constraint on the degree of freedom of the emitter, so any number of elastic bodies can be used in any direction.

[0060] The emitter 21 is a tungsten wire with a sharpened tip, and here, the portion opposite the tip is fixed to an emitter support 22 to eliminate or reduce drift.

[0061] The emitter support 22 fixes the emitter 21 and eliminates or reduces drift. The emitter tip position is restricted in terms of freedom in the X, Y, and Z directions by the emitter support 22.

[0062] The extractor support part 3 holds the extractor 4 .

[0063] The extractor 4 is a disk with a hole in the center, and generates an electric field by applying a voltage between it and the tip of the emitter 21, thereby field-emitting an electron beam.

[0064] The secondary electron absorbing film 4-1 absorbs the electron beam emitted from the emitter 21 and reduces gas emission (described later). The secondary electron absorbing film 4-1 is also attached to the lower surface of the extractor 4 in FIG. 1 in the same manner as described above, and reduces gas emission (described later).

[0065] The electron beam 5 is an electron beam extracted from an emitter 21 .

[0066] The support member 6 is used to fix the support column 7 and is electrically insulating.

[0067] The supports 7 are electrically conductive supports that are symmetrically arranged to fix the filaments 1 .

[0068] The switch 8 is a switch for passing a current between the two supports 7 to energize and heat the filament during flashing.

[0069] The device state detection device 9 detects whether the device is in a state where flushing is required (for example, detecting a flushing instruction from an operator, or detecting whether the device has reached a preset flushing state).

[0070] The heating power supply 10 is a power supply for energizing and heating the filament 8 .

[0071] The gas vent window 111 is a window for releasing gas within the space where the emitter 21 is located to the outside.

[0072] The field emission power supply 12 is a power supply that applies a voltage between the emitter 21 and the extractor 4 to cause electrons to be field emitted from the tip of the emitter 21 .

[0073] Current A is a current that flows through filament A fixed between a pair of symmetrically arranged supports 7, and in this case, is a current that flows in any of the X and Y directions (the axial direction of the electron beam is the Z direction). Note that since emitter 21 is fixed to emitter support part 22 and does not drift, elastic body 11 is configured so that drift caused by expansion and contraction when heated by current is not transmitted to emitter 21 as much as possible, or is configured so that it is canceled out by being arranged symmetrically, thereby eliminating or reducing drift.

[0074] In the example of (a) restricting the degree of freedom, as shown in the fixed degree of freedom (Y=0) and fixed degree of freedom (X=0) in the figure, the surface opposite the tip of the emitter 21 is fixed 32 to the emitter support part 22, thereby reducing the drift of the emitter 21 in the X direction and Y direction.

[0075] Furthermore, the drift of the tip of the emitter 21 in the Z direction can be ignored because the opening angle in the direction of travel (Z direction) of the electron beam 5 is small, and even if there is drift, the beam size of the electron beam 5 when irradiated onto a mask, etc. does not become significantly larger.

[0076] Furthermore, the drift that occurs when the filament is heated by electrical current (for example, 2 to 20 seconds, or even longer) can be divided into short-term drift and long-term drift. The former, short-term drift, is the drift at the tip of the emitter 21 caused by the expansion and contraction of the filament when electrical current is applied to the filament. On the other hand, the latter, long-term drift, is the drift that occurs when the temperature gradually rises and falls (and distortion is eliminated) due to thermal conduction or thermal radiation from the filament when electrical current is applied to the filament through the support 7, emitter support 22, support member 6, and other paths when the filament is heated by electrical current, and this drift continues for an extremely long period of time. Here, both types of drift are referred to as "drift."

[0077] Next, the configuration of FIG. 2 will be briefly described.

[0078] (1) The tip and opposite end of the emitter 21 are fixed to the center of the emitter support 22, which is made of an ultra-low thermal conductivity ceramic material such as Microtherm. It is preferable to fabricate the emitter 21 and emitter support 22 as a single unit. They can also be attached by gluing or by threading the tungsten needle (emitter 21). This prevents the emitter 21 from shifting or tilting even when the elastic body (filament) 11 is heated by passing a current through it, causing it to expand and contract or move hysteretically due to thermal expansion. The emitter material can be made of materials other than tungsten, such as LaB6 or hBN, which have a low work function. Metal oxides, CNTs, thorium-impregnated emitters, and CaO-Al2O3-based electrolytes can also be used.

[0079] (2) The conductive support 7 is fixed with a member made of an insulating material with an ultra-low thermal expansion coefficient, such as alumina or cordierite ceramic material. The extractor 4 is made of a conductive member with holes of approximately 0.5 mm or less that allow electrons to pass through. This member is preferably made of a material that can withstand high-temperature processing and does not easily absorb gases, so that outgassing is easy. It is also desirable that the thermal expansion coefficient be less than 1 ppm. These members are surrounded on their outer periphery by the extractor support part 3 and are integrated to prevent the emitter tip position from moving relative to the extractor position. In particular, to prevent the tip position of the emitter 21 from moving due to thermal expansion, the members are fabricated and fixed concentrically with the axis of the emitter 21 with an error of several microns. The concentric arrangement of the members prevents the axis of the electron beam 5 from moving when heated for outgassing.

[0080] (3) The extractor 4 is generally a metal plate with a hole in the center for the electron beam to pass through. Non-magnetic materials such as stainless steel or titanium are used, but materials with good gas release properties such as BeCu can also be used. It is desirable to use these that have been thoroughly vacuum heated and degassed in advance.

[0081] (4) The extractor 4 can be provided with holes for venting gases designed to prevent adverse effects on the electric field generated at the tip of the emitter 21. For the same purpose, a portion of the extractor 4 can be made mesh-like to allow gas to pass through. Similarly, it is desirable that the extractor support part 3 be provided with multiple windows for venting gases. As long as it can support the extractor 4, it may be made of a columnar member.

[0082] Figure 3 shows a configuration diagram (part 3) of one embodiment of the present invention. This Figure 3 is characterized in that the tip of the emitter 21 in Figure 2 is configured to protrude above the electrode of the extractor 4, as shown in Figure 3. This provides the effects (1) and (2) of Figure 5(b) (described later using Figure 5).

[0083] Fig. 4 shows the configuration of another embodiment of the present invention, in which a groove is provided in the lower portion of the emitter 21 as shown in the figure, and heating is performed by passing electricity through the groove.

[0084] In Figure 4, the emitter 21 has a structure in which the emitter 21 and a conventional filament are integrated as shown. This emitter 21 is heated by, for example, digging a vertical groove in the pointed tip of a tungsten needle and the opposite end as shown in the figure, and forming a resistance heating circuit around the groove. In other words, by passing a current from the lower left of the groove to the top, and then from the top to the groove to the lower right (or by passing a current in the opposite direction), the upper tip of the emitter 21 is heated by electrical heating.

[0085] The support pillars 7 are made of an electrically conductive material with a small coefficient of thermal expansion and are connected to the left and right sides of the grooved portion below the emitter 21 in the drawing to pass (supply) current.

[0086] With the above structure, when the grooved portion below the emitter 21 is heated by applying electricity, heat is concentrated only on the pointed portion at the top, and the pointed portion at the tip of the emitter 21 can be heated to a high temperature with little thermal energy overall. In other words, excess heat is not transferred to other areas (for example, to the emitter support portion in Figures 2 and 3), reducing displacement and distortion due to thermal expansion. There is no need to provide a new emitter support portion (see Figures 2 and 3) to secure the emitter 21, and this simple structure prevents displacement during flushing.

[0087] FIG. 5 shows an explanatory diagram of the gas generation reduction of the present invention.

[0088] FIG. 5(a) shows an example where the emitter is recessed (FIGS. 1 and 2), and FIG. 5(b) shows an example where the emitter is protruding (FIGS. 3 and 4).

[0089] 5(a) shows a schematic diagram of the direction of the electron beam when the sharp tip of the emitter 21 is positioned below the bottom surface of the hole in the extractor 4 shown in the figure, and the electric field when a positive voltage is applied to the extractor 4 with respect to the emitter 21. As shown in the figure, an electric field is formed around the tip of the emitter 21, and the electron beam is emitted in a direction perpendicular to that electric field, so most of the electron beam collides with the bottom surface of the hole in the extractor 4 as shown in the figure, which has the disadvantage of releasing gas.

[0090] That is, as shown in the figure, "Most of the electrons emitted from Emitter 21 collide with Extractor 4, generating a large amount of gas due to the electron impact." This means that...

[0091] In FIG. 5B, the direction of the electron beam when the pointed tip of the emitter 21 is positioned above the upper surface of the hole of the illustrated extractor 4, and the direction of the electron beam when the emitter 21 is positioned above the upper surface of the hole of the illustrated extractor 4, 5(a) is a schematic diagram showing the electric field when a positive voltage is applied to the extractor 4 with respect to the emitter 21. As shown in the figure, a strong electric field is formed around the tip of the emitter 21, and the electron beam is emitted in a direction perpendicular to that electric field. As shown in the figure, the electron beam is emitted vertically upward from the hole in the extractor 4 and does not collide with the extractor 4, thereby eliminating the drawback of Figure 5(a). The emitter height for the optimal extractor position that maximizes the electron beam extraction efficiency is determined by simulation or experiment.

[0092] That is, as shown in the figure, (1) Most of the electrons emitted from the emitter 21 become an electron beam without colliding with the extractor 4. This effect of improving the electron beam extraction makes it possible to use sufficient probe current with a lower applied voltage than before, thereby improving throughput and extending the emitter life.

[0093] (2) The energy can be reduced to reduce sputtering of the emitter 21 by positive ions. Here, in (2), the energy of the positive ions among the ions generated when the electrons emitted in (1) collide with the nearby gas is small (the energy is small because they are ionized in the very vicinity of the extractor 4), so even if positive ions collide with the tip of the emitter 21, the amount of sputtering can be reduced.

[0094] FIG. 6 shows an example of the shape of the emitter tip of the present invention.

[0095] Figure 6(a) shows an example of a high-brightness emitter, where Figure 6(a-1) shows a top view and Figure 6(a-2) shows a side view.

[0096] In Figure 6(a), by making the shape of the tip of the emitter a long, spot-like cylinder, as shown, it is possible to form an emitter that is high in brightness and can be used for a long period of time even if the upper tip becomes obsolete due to flashing, etc.

[0097] Figure 6(b) shows an example of a high current emitter, where Figure 6(b-1) shows a top view and Figure 6(b-2) shows a side view.

[0098] In Figure 6(b), by making the shape of the tip of the emitter ring-shaped and placing the cup upside down as shown, it is possible to form a ring-shaped emitter that is high in brightness, has a large current, and can be used for a long period of time even if the upper tip is lost due to flashing, etc.

[0099] FIG. 7 shows an explanatory diagram of the coating of the emitter tip of the present invention.

[0100] FIG. 7(a) shows an example of the tip of the emitter, and FIG. 7(b) shows an explanatory diagram of the applied voltage and brightness.

[0101] FIG. 7(a) shows the tip of the emitter, FIG. 7(a-1) shows a side view, and FIG. 7(a-2) shows a top view.

[0102] In Figure 7(a), the emitter tip is the tip of the emitter 2, 21 already described, and as shown in the figure, a portion of the cylindrical tip of about several tens of nanometers is left, while the other portion is covered with a cylindrical insulator (insulating sleeve), giving it a structure that prevents the emission of electron beams.

[0103] 7(b) shows an explanatory diagram of applied voltage and luminance, where the horizontal axis represents applied voltage and the vertical axis represents luminance at that time.

[0104] In Figure 7(b), the "covered" state represents the case where the emitter is covered with an insulator, non-electron emitting material, or a material with a work function greater than tungsten, as shown in Figure 7(a), and only protrudes a few tens of nanometers from the tip. In this case, electron beams are field emitted only from a portion of the emitter tip that is about a few tens of nanometers long; that is, the electric field is concentrated in this portion, creating a high electric field. As a result, many electron beams are emitted from the same location (more electron beams per unit area), resulting in high brightness (see the "covered" state in the figure). Because the electron emission area is limited, the energy dispersion is not large.

[0105] On the other hand, when there is no cover, increasing the applied voltage increases the total current, but the area from which the electron beam is emitted increases, the electric field strength decreases, and the brightness becomes relatively lower (relative to the case with a cover) (see the illustration without a cover). Since electrons of various energies are emitted, the energy dispersion also increases.

[0106] FIG. 8 shows an example of a micro CFD manufacturing process (deposition) of the present invention. This FIG. 8 shows the steps for manufacturing the previously described emitters 2 and 21 by known deposition. The emitters 2 and 21 described in FIGS. 1 to 7 use single crystals such as the (310) surface of tungsten, which is easy to fabricate by electrolytic polishing or the like. However, the material is not limited to these single crystals. FIG. 8 (and FIG. 9) shows the steps for fabricating the emitter material by deposition (etching in FIG. 9). For example, any material that can be gasified in a vacuum and from which an organometallic compound can be synthesized can be deposited, including pure metals (W, Cr, Mo, Pt, Re, Ir, Cu, etc.), metal oxides, and organic materials such as columnar carbon nanotubes (CNTs).

[0107] 8, as is well known, emitters 2 and 21 having the shapes explained in Figures 1 to 7 can be formed by deposition in steps S1 to S6 and further in step S7. An example of the configuration of a deposition apparatus is shown in Figure 10, which will be described later.

[0108] FIG. 9 shows an example of the micro CFD manufacturing process (etching) of the present invention. This FIG. 9 shows the steps for manufacturing the emitters 2 and 21 described above by known etching. The emitters 2 and 21 described above in FIGS. 1 to 7 use single crystals such as the (310) surface of tungsten, which is easy to create by electrolytic polishing or the like. However, the material is not limited to these single crystals, and FIG. 8 (and FIG. 9) shows the steps for creating emitter materials by particle beam etching such as electron beams or ion beams. For example, crystalline materials such as LaB6 and BaO can be used.

[0109] 9, as is well known, an emitter material is formed on a silicon substrate in steps S11 to S15 and further in step S16, and then the emitters 2 and 21 having the shapes described in Figures 1 to 7 are formed by etching in step S17. An example of the configuration of an etching apparatus is shown in Figure 10, which will be described later.

[0110] Figure 10 shows an example of the use of the CFE of the present invention. This Figure 10 shows an electron beam mask repair device (see, for example, Japanese Patent Application No. 2022-135894), which is one of the electron beam devices using the CFE of the present invention (the CFE already described in Figures 1 to 9).

[0111] In Figure 10, the mask repair device consists of an electron gun for generating the electron beam, a device for temporarily heating the electron emission source to degas it, an objective lens for narrowing the electron beam, an electron beam deflector for scanning the electron beam, a blanking device for turning the electron beam on and off, a gas supply device for supplying gas that reacts with the electron beam, a gas supply nozzle for supplying gas to specific positions on the photomask, an XY stage for moving the photomask to a specified position and a Z stage for maintaining a constant WD and keeping the photomask horizontal. It also consists of a vacuum chamber and vacuum pump for maintaining a vacuum state so that the electron beam can propagate, and a controller and PC for controlling the above equipment.

[0112] A mask repair system uses the interaction of an electron beam and a reactive gas to etch or deposit a photomask to repair a pattern. This system is required to repair as small an area as possible as quickly as possible. To perform such small repairs, it is important to use low energy and a small beam spot. Mask repair takes several minutes to several tens of minutes. When it detects that the mask is not in the repair process state or is not in the SEM observation state, it can automatically perform degassing if necessary by temporarily turning on a heater to raise the temperature of the electron emitter. Simply, degassing can be performed at set intervals. The emitter can also be constantly heated to a low temperature of around 200°C, which does not affect the electron energy dispersion.

[0113] Since it is only necessary to heat the tip of the emitter, the laser beam can be guided through an optical fiber, etc. By automatically repeating this process, it is possible to maintain an ultra-high brightness state.

[0114] When a conventional TFE is used in an electron gun, narrowing a low-energy electron beam of several hundred electron volts to a nanometer order results in an extremely low probe current of a few pA or less, making it difficult to achieve a practical repair speed.

[0115] By using the CFE of the present invention, it is possible to obtain an irradiation current 10 times or more greater than that of conventional methods with the same beam size, and therefore it is expected that the repair speed will be improved by 10 times or more.

[0116] Similarly, when used in high-speed inspection equipment or CDSEM, the probe current value can be increased while keeping the beam size small, thereby improving throughput. [Brief explanation of the drawings]

[0117] [Figure 1] FIG. 1 is a configuration diagram (part 1) of an embodiment of the present invention. [Figure 2] FIG. 2 is a configuration diagram (part 2) of an embodiment of the present invention. [Figure 3] FIG. 3 is a configuration diagram (part 3) of an embodiment of the present invention. [Figure 4] FIG. 10 is a diagram illustrating the configuration of another embodiment of the present invention. [Figure 5] FIG. 2 is an explanatory diagram of the reduction in gas generation according to the present invention. [Figure 6] 1 shows an example of the emitter tip shape of the present invention. [Figure 7] FIG. 2 is an explanatory diagram of the coating of the emitter tip of the present invention. [Figure 8] 1 is an example of a micro CFD manufacturing process (deposition) of the present invention. [Figure 9] 1 is an example (etching) of a micro CFD manufacturing process of the present invention. [Figure 10] This is an example of the use of CFD of the present invention. [Explanation of symbols]

[0118] 1: Filament 11: Elastic body 111: Gas vent window 2, 21: Emitter 22: Emitter support 3: Extractor support 32: Fixed 4: Extractor 4-1: Secondary electron absorbing film 5: Electron beam 6: Support member 7: Prop 8: Switch 9: Device status detection device 10:Heating power supply 11: Gas vent window 12: Field emission power supply

Claims

1. In a cold cathode electron source that extracts an electron beam from an emitter, a pointed emitter that emits an electron beam; an extractor with a hole for extracting the electron beam by applying an electric field to the tip of the emitter; a heating elastic body for holding and flushing the emitter; a support for supporting the elastic body and supplying a power source for heating the elastic body; a cold-cathode electron source, characterized in that the elastic body is fixed to the support pillars arranged at positions symmetrical about the emitter, and the elastic body expands and contracts during the flashing to reduce drift of the emitter.

2. In a cold cathode electron source that extracts an electron beam from an emitter, a pointed emitter that emits an electron beam; an extractor with a hole for extracting the electron beam by applying an electric field to the tip of the emitter; a heating elastic body for holding and flushing the emitter; a support column for supporting the elastic body and supplying power for heating; a thermally insulating emitter support portion that fixes a portion of the emitter opposite to the tip, A cold cathode electron gun characterized in that drift of the emitter fixed to the emitter support portion during flashing is eliminated or reduced.

3. 2. A cold cathode electron gun according to claim 1, wherein the number of said elastic bodies and said support posts is an integral multiple of two.

4. 4. The cold cathode electron gun according to claim 1, wherein the portion to be heated of said elastic body is eliminated and a portion to be heated is provided in said emitter.

5. 5. A cold cathode electron gun according to claim 1, wherein the tip of the emitter protrudes above the hole of the extractor, thereby reducing the collision of the electron beam with the extractor, thereby reducing gas emission or increasing the efficiency of electron beam utilization.

6. 6. The cold cathode electron gun according to claim 1, wherein the tip of the emitter is shaped like a spot to produce a high-brightness, minute spot, or like a ring to produce a high-brightness, large-current electron beam.

7. 7. The cold cathode electron gun according to claim 1, wherein a location at a predetermined distance or more from the tip of the emitter is covered with a non-electron emitting body, thereby increasing the brightness of the electron beam emitted from the tip portion or reducing a decrease in brightness due to flashing.

8. 8. The cold cathode electron gun according to claim 1, wherein the pointed emitter is formed on a substrate by deposition or etching.

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