JP2013235799A - Method of manufacturing field emission electron source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a field emission electron source capable of further improving electron emission characteristics and reliability respectively.SOLUTION: A method of manufacturing a field emission electron source comprising a first electrode 2, a second electrode 7 opposed to the first electrode 2, and a strong field drift layer 6 provided between the first electrode 2 and the second electrode 7, and being capable of emitting electrons via the second electrode 7, includes: a first step of forming a semiconductor layer 3 on one surface side of the first electrode 2; a second step of forming a porous semiconductor layer 4 by making at least a part of the semiconductor layer 3 porous by anode oxidation treatment; a third step of forming the strong field drift layer 6 by oxidizing or nitriding the porous semiconductor layer 4; and a fourth step of forming the second electrode 7. The method includes a fifth step of removing impurities remaining on the strong field drift layer 6 by utilizing supercritical fluid, after the fourth step.

Description

  The present invention relates to a method for manufacturing a field emission electron source.

  Conventionally, a conductive substrate, a strong electric field drift layer made of an oxidized or nitrided porous semiconductor layer formed on one surface side of the conductive substrate, and a surface electrode formed on the strong electric field drift layer are provided. A field emission electron source is known (for example, Patent Document 1). In this field emission electron source, a voltage is applied between the surface electrode and the conductive substrate so that the surface electrode is on the high potential side with respect to the conductive substrate, so that the strong electric field drift layer is formed from the conductive substrate. The injected electrons drift through the strong electric field drift layer and are emitted through the surface electrode. In this type of field emission electron source, at least a part of the conductive substrate constitutes the lower electrode (first electrode), and the surface electrode constitutes the upper electrode (second electrode).

  By the way, Patent Document 1 proposes a manufacturing method capable of improving the electron emission characteristics and reliability of a field emission electron source. In this manufacturing method, a porous semiconductor layer is formed by making at least a part of the semiconductor layer porous by a first step of forming a semiconductor layer on one surface side of a conductive substrate and anodizing treatment. A second step and a third step of forming a strong electric field drift layer by oxidizing or nitriding the porous semiconductor layer. Further, this manufacturing method uses a supercritical fluid for moisture remaining on one surface side of the conductive substrate in at least one stage after the third process between the second process and the third process. And a supercritical drying step for removing the same.

JP 2002-352705 A

  The field emission electron source is improved in electron emission characteristics and reliability by adopting the above-described manufacturing method, but further improvements in the electron emission characteristics and reliability are expected.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide a method of manufacturing a field emission electron source capable of further improving the electron emission characteristics and reliability. It is.

  The method of manufacturing a field emission electron source according to the present invention includes: a first electrode; a second electrode opposed to the first electrode; and a strong electric field drift layer between the first electrode and the second electrode. A method of manufacturing a field emission electron source capable of emitting electrons through the second electrode, the first step of forming a semiconductor layer on one surface side of the first electrode, A second step of forming a porous semiconductor layer by making at least a portion of the semiconductor layer porous; and a third step of forming the strong electric field drift layer by oxidizing or nitriding the porous semiconductor layer. And a fourth step of forming the second electrode, and a fifth step of removing impurities remaining in the strong electric field drift layer using a supercritical fluid after the fourth step. It is characterized by providing.

  In this method of manufacturing a field emission electron source, it remains on the one surface side of the first electrode in at least one stage after the third step between the second step and the third step. It is preferable to provide a supercritical drying step of removing moisture and impurities that are present using a supercritical fluid.

  In the method for manufacturing a field emission electron source of the present invention, it is possible to provide a field emission electron source capable of further improving the electron emission characteristics and the reliability.

It is principal process sectional drawing for demonstrating the manufacturing method of the field emission type electron source of embodiment. It is a schematic perspective view of the field emission type electron source of an embodiment. (A) is the schematic sectional drawing which the field emission type electron source of embodiment partly fractured, (b) is the other schematic sectional drawing which partly fractured the field emission type electron source of example embodiment. (A) is a principal part schematic sectional drawing of the field emission type electron source of embodiment, (b) is an operation | movement principle explanatory drawing of the field emission type electron source of embodiment. It is operation | movement explanatory drawing of the field emission type electron source of embodiment. It is an electron emission characteristic figure of the field emission type electron source of each of an embodiment and a comparative example.

  As shown in FIGS. 2 to 4, the field emission electron source 10 according to the present embodiment includes a first electrode 2, a second electrode 7 facing the first electrode 2, a first electrode 2, and a second electrode 7. And a strong electric field drift layer 6 between them, and can emit electrons through the second electrode 7. Here, the first electrode 2 is formed on one surface side of the substrate 1. Further, the first electrode 2 and the second electrode 7 are arranged apart from each other in the thickness direction of the first electrode 2. The thickness of the second electrode 7 is preferably set in the range of about 10 nm to 15 nm.

  In the field emission electron source 10, each of the first electrode 2 and the second electrode 7 has a band shape. In the field emission electron source 10, a plurality of first electrodes 2 are arranged on the one surface of the substrate 1, and the functional layer 16 including the strong electric field drift layer 6 is disposed on the one surface side of the substrate 1. Each of the first electrodes 2 and the substrate 1 are formed so as to cover the one surface. The field emission electron source 10 has a plurality of second electrodes 7 arranged in a row on the surface side of the functional layer 16 opposite to the first electrode 2 side. The plurality of second electrodes 7 are arranged in a direction intersecting the first electrode 2.

  The field emission electron source 10 includes a first electrode 2, a strong electric field drift layer 6, and a first electrode at lattice points of a matrix (lattice) including a plurality of first electrode 2 groups and a plurality of second electrode 7 groups. This corresponds to the arrangement of the electron source element 10 a having two electrodes 7. Therefore, in the field emission electron source 10, it is possible to emit electrons from a desired electron source element 10a by selecting a set of the second electrode 7 and the first electrode 2 to which a voltage is applied. Pads 27 are formed on both ends of the first electrode 2 in the longitudinal direction. Further, pads 28 are formed on both ends of the second electrode 7 in the longitudinal direction.

  The functional layer 16 includes a strong electric field drift layer 6 in each of the regions overlapping both the first electrode 2 and the second electrode 7 in the thickness direction of the first electrode 2. In addition, the functional layer 16 is configured by the semiconductor layer 3 except for the strong electric field drift layer 6. In the functional layer 16, a part of the semiconductor layer 3 is interposed between the strong electric field drift layer 6 and the first electrode 2. The functional layer 16 constitutes an electron passage layer by the strong electric field drift layer 6 and the portion 3 a interposed between the strong electric field drift layer 6 and the first electrode 2 in the semiconductor layer 3. The electron passage layer is a layer through which electrons injected from the first electrode 2 pass toward the second electrode 7. The functional layer 16 may have a configuration in which a part of the semiconductor layer 3 is not interposed between the strong electric field drift layer 6 and the first electrode 2. In other words, the electron passage layer may be constituted only by the strong electric field drift layer 6. In the functional layer 16, a region between the adjacent strong electric field drift layers 6 in the semiconductor layer 3 constitutes an element isolation portion 3 b that suppresses the occurrence of crosstalk between adjacent electron source elements 10 a. ing.

  In addition, the field emission electron source 10 is disposed along the longitudinal direction of the second electrode 7 on each side of the width direction of each second electrode 7 and is electrically connected to the second electrode 7. It has.

  In addition, the field emission electron source 10 includes the element isolation unit 3b and the element isolation unit 3b on the element isolation unit 3b between the strong electric field drift layers 6 adjacent to each other in the direction along the longitudinal direction of the second electrode 7 in the functional layer 16. An insulating layer 8 is provided between the two electrodes 7. Since the field emission electron source 10 includes the insulating layer 8, it is possible to further suppress the occurrence of crosstalk. The insulating layer 8 is formed of a silicon oxide film, but is not limited thereto, and may be formed of, for example, a silicon nitride film or a stacked film of a silicon oxide film and a silicon nitride film. .

  The substrate 1 is composed of an insulating glass substrate. As the glass substrate, for example, an alkali-free glass substrate or a quartz glass substrate can be used. As the substrate 1, an insulating ceramic substrate or the like can be used.

  The first electrode 2 is composed of a conductive layer. The thickness of the first electrode 2 is preferably set in a range of about 100 nm to 400 nm, for example. The conductive layer constituting the first electrode 2 may have a single layer structure or a multilayer structure of two or more layers. When the first electrode 2 is formed of a conductive layer having a multilayer structure, for example, a laminated film of a Ti film on the substrate 1 and a W film on the Ti film can be employed. In this case, the 1st electrode 2 can be comprised by the conductive layer which consists of a laminated film of Ti film | membrane with a thickness of 50 nm, and W film | membrane with a thickness of 250 nm, for example. As a material for the conductive layer, for example, a metal such as Cr, W, Ti, Ta, Ni, Al, Cu, Au, Pt, or Mo, an alloy, an intermetallic compound (silicide, or the like) can be employed.

  The functional layer 16 is formed across each first electrode 2 and the one surface of the substrate 1. In short, the functional layer 16 is formed so as to cover each surface of the first electrodes 2 and the substrate 1. The functional layer 16 is formed from the semiconductor layer 3 formed on the one surface side of the substrate 1 after the first electrodes 2 are formed on the one surface side of the substrate 1. The strong electric field drift layer 6 in the functional layer 16 is formed by oxidizing or nitriding a porous semiconductor layer formed by anodizing a part of the semiconductor layer 3. The semiconductor layer 3 is preferably composed of a non-doped polycrystalline silicon layer. In the present embodiment, the thickness of the functional layer 16 is set to 1.5 μm, but this numerical value is an example and is not particularly limited. The thickness of the functional layer 16 is preferably set in a range of about 0.5 μm to 2 μm, for example.

  As shown in FIG. 4B, the strong electric field drift layer 6 includes a plurality of grains 32 formed along the thickness direction of the first electrode 2 (see FIG. 4A), and each of the grains 32. A thin first insulating film 35 formed on the surface of the semiconductor substrate, a large number of nanometer-order microcrystalline semiconductors 33 interposed between adjacent grains 32, and a microcrystalline semiconductor 33 formed on the surface of each microcrystalline semiconductor 33. A second insulating film 34 having a thickness smaller than the crystal grain size. In the field emission electron source 10, the microcrystalline semiconductor 33 is made of microcrystalline silicon, and the first insulating film 35 and the second insulating film 34 are made of a silicon oxide film. Here, the microcrystalline semiconductor 33 and the insulating films 34 and 35 are not formed in the element isolation portion 3 b in the functional layer 16.

  The thickness of the second electrode 7 is preferably set in the range of about 10 to 15 nm. The second electrode 7 includes a first conductive layer on the functional layer 16 side and a second conductive layer laminated on the first conductive layer. As the material of the first conductive layer, Cr is employed, but is not limited to Cr, and for example, Ni, Pt, Ti, Zr, Rh, Hf, Ir, or the like may be employed. As a material of the second conductive layer, Au is preferable. In the field emission electron source 10, the thicknesses of the first conductive layer and the second conductive layer are set to 2 nm and 10 nm, respectively, but are not particularly limited to these numerical values.

  The material of the second electrode 7 is preferably a metal that has a relatively high conductivity, a relatively low work function, excellent oxidation resistance, and is chemically stable. The second electrode 7 is not limited to a two-layer structure, and may be a single-layer structure.

When electrons are emitted from the electron source element 10a, for example, as shown in FIG. 5, the second electrode 7 and the first electrode 2 so that the second electrode 7 is on the high potential side with respect to the first electrode 2. A DC drive voltage Vps may be applied between the two. When measuring the electron emission characteristics of the field emission electron source 10 or using the field emission electron source 10, a collector electrode 9 facing the field emission electron source 10 is provided. It is preferable to apply a DC acceleration voltage Vc between the collector electrode 9 and the second electrode 7 so that is on the high potential side with respect to the second electrode 7. 5 indicates the flow of electrons e ⁻ emitted through the second electrode 7 (the solid line arrow in FIG. 4B drifts through the strong electric field drift layer 6 and passes through the surface electrode 7). Shows the flow of emitted electrons e ⁻ ). The electrons injected from the first electrode 2 into the strong electric field drift layer 6 and reaching the surface of the strong electric field drift layer 6 are considered to be hot electrons, and are easily tunneled through the second electrode 7 and emitted. That is, in the strong electric field drift layer 6, electrons are accelerated in the direction from the first electrode 2 toward the second electrode 7 by the electric field that acts when the second electrode 7 is set to the high potential side with respect to the first electrode 2. A drifting quantum effect will appear.

  As the material of each pad 27, 28, for example, Al, Al-Si, Au, Pd or the like can be adopted.

  As a material of the bus electrode 25, for example, a material having a low resistivity such as Al or Cu is preferable. The thickness dimension of the bus electrode 25 is preferably larger than the thickness dimension of the second electrode 7.

  In the following description, the current flowing between the second electrode 7 and the first electrode 2 in the electron source element 10a is referred to as a diode current Ips, and the current flowing between the collector electrode 9 and the second electrode 7 is referred to as an emission current ( This is called emission electron current (Ie). The electron source element 10a has a higher electron emission efficiency (= (Ie / Ips) × 100 [%]) as the ratio of the emission current Ie to the diode current Ips (= Ie / Ips) increases. The electron source element 10a can emit electrons even when the drive voltage Vps applied between the second electrode 7 and the first electrode 2 is a low voltage of about 10 to 20V. Further, the electron source element 10a has a small degree of vacuum dependency of electron emission characteristics. Further, the electron source element 10a can stably emit electrons without causing a popping phenomenon.

  In the above-described electron source element 10a, it is considered that electron emission occurs in the following model. In order to emit electrons from the electron source element 10a, for example, the drive voltage Vps is applied between the second electrode 7 and the first electrode 2 with the second electrode 7 at the high potential side, and the collector electrode 9 and the second electrode 7 An acceleration voltage Vc is applied between the electrode 7 and the collector electrode 9 as a high potential side. Then, in the electron source element 10a, electrons are thermally excited from the first electrode 2 and injected into the strong electric field drift layer 6. The electrons injected into the strong electric field drift layer 6 are accelerated by the strong electric field applied to the second insulating film 34, and the portion between the grains 32 in the strong electric field drift layer 6 is directed toward the second electrode 7. Drift. Therefore, when the driving voltage Vps is equal to or higher than a predetermined value (for example, a voltage at which the potential of the second electrode 7 is equal to or higher than the work function), the electron source element 10a causes the electrons that have reached the second electrode 7 to Tunnel and release into vacuum. Each microcrystalline semiconductor 33 in the strong electric field drift layer 6 is about the Bohr radius. For this reason, electrons accelerated by a strong electric field applied to the thin second insulating film 34 on the surface of the microcrystalline semiconductor 33 drift in the strong electric field drift layer 6 with almost no scattering, and pass through the second electrode 7. Released into vacuum. Further, since the heat generated in the strong electric field drift layer 6 is dissipated through the grains 32, no popping phenomenon occurs during electron emission, and electrons can be stably emitted. The electrons reaching the surface of the strong electric field drift layer 6 are considered to be hot electrons, and are easily tunneled through the second electrode 7 and released into the vacuum. The electron source element 10a can stably emit electrons not only in a vacuum but also in the atmosphere.

  Hereinafter, a method for manufacturing the field emission electron source 10 will be described with reference to FIG.

  In manufacturing the field emission electron source 10, first, the substrate 1 is prepared (FIG. 1A). The substrate 1 is preferably in a wafer state in which a plurality of field emission electron sources 10 can be formed. Moreover, although the thickness of the board | substrate 1 was 0.7 mm, it does not specifically limit.

  After the substrate 1 is prepared, a structure shown in FIG. 1B is obtained by performing a first electrode forming step of forming the first electrode 2 on the one surface side of the substrate 1. In the first electrode forming step, for example, a conductive layer serving as a basis of the first electrode 2 is formed on the entire surface of the substrate 1 on the one surface side by a sputtering method, a vapor deposition method, or the like, and then a photolithography technique and an etching technique. The first electrode 2 is formed by patterning the conductive layer using the above. In the first electrode formation step, the first electrode 2 may be formed using a lift-off method and a sputtering method. As the conductive layer, for example, a laminated film of a Ti film on the one surface of the substrate 1 and a W film on the Ti film is employed, but a single layer film may be employed as the conductive layer.

After the first electrode forming step, a semiconductor layer forming step for forming a semiconductor layer 3 made of a non-doped polycrystalline silicon layer on the one surface side of the substrate 1 is performed to obtain the structure shown in FIG. . In the semiconductor layer forming step, a non-doped polycrystalline silicon layer or an amorphous silicon layer is formed by plasma CVD (Chemical Vapor Deposition), and then the semiconductor layer 3 is formed by annealing. The annealing process may be performed, for example, in an H ₂ gas atmosphere, an N ₂ gas atmosphere, or a mixed gas atmosphere of H ₂ gas and N ₂ gas. The method for forming the polycrystalline silicon layer is not limited to the plasma CVD method, and for example, a CGS (Continuous Grain Silicon) method, a catalytic CVD method, or the like may be employed. The thickness of the semiconductor layer 3 is set to 1.5 μm, but is not particularly limited. In the present embodiment, the semiconductor layer forming step constitutes a first step of forming the semiconductor layer 3 on the one surface side of the first electrode 2.

After the semiconductor layer 3 is formed, a resist layer forming step is performed in which a resist layer (not shown) covering the surface of the semiconductor layer 3 other than the region where the porous semiconductor layer 4 is to be formed is formed using photolithography technology. . After this resist layer forming step, an anodizing treatment step for forming the porous semiconductor layer 4 by making at least a part of the semiconductor layer 3 porous by anodizing treatment is carried out, so that FIG. The structure shown in is obtained. In the anodic oxidation treatment, first, a treatment tank (not shown) containing a predetermined electrolytic solution is prepared, and a surface of the semiconductor layer 3 is in contact with the electrolytic solution. The cathodes (not shown) are arranged to face each other. Next, in the anodizing treatment, the porous semiconductor layer 4 is applied by applying a voltage between the cathode and the first electrode 2 and allowing a constant current having a first predetermined current density to flow for a first predetermined time. Form. In the anodizing process, the porous semiconductor layer 4 having a predetermined thickness is formed in a portion of the semiconductor layer 3 that overlaps the first electrode 2 in the thickness direction of the first electrode 2. In the non-overlapping portion, the semiconductor layer 3 remains as it is. The predetermined thickness dimension of the porous semiconductor layer 4 is set to be smaller than the thickness dimension of the semiconductor layer 3 before the anodizing treatment step, but may be set to the same value. In the anodizing treatment, since the semiconductor material of the semiconductor layer 3 is silicon, for example, a hydrofluoric acid solution made of a mixed solution obtained by mixing a 55 wt% hydrogen fluoride aqueous solution and ethanol in a ratio of approximately 1: 1 is used as the electrolytic solution. be able to. The concentration of the aqueous hydrogen fluoride solution and the mixing ratio with ethanol are not particularly limited. In addition, the liquid mixed with the aqueous hydrogen fluoride solution is not limited to ethanol, and is not particularly limited as long as it is a liquid that can remove bubbles generated in the anodizing reaction, such as alcohol such as methanol, propanol, and isopropanol (IPA). Absent. Further, as the electrolytic solution, an appropriate mixed solution may be used according to the semiconductor material of the semiconductor layer 3. Further, in the anodizing treatment, the first predetermined current density is set to 12 mA / cm ² and the first predetermined time is set to 12 seconds. However, these numerical values are only examples and are particularly limited. is not. In the anodic oxidation treatment, the anodic oxidation reaction preferentially proceeds in the vicinity of the grain boundaries of adjacent grains 32, so that it is assumed that a large number of microcrystalline semiconductors 33 are formed continuously in the thickness direction of the semiconductor layer 3. In the present embodiment, since the semiconductor layer 3 is composed of a non-doped polycrystalline silicon layer, a current is allowed to flow while irradiating light from the light source to the semiconductor layer 3 during the anodic oxidation process. When the p-type polycrystalline silicon layer is used, there is no need for light irradiation. In the present embodiment, the anodizing process constitutes a second process for forming the porous semiconductor layer 4 by making at least a part of the semiconductor layer 3 porous by anodizing.

  After the anodizing treatment step, the structure shown in FIG. 1E is obtained by performing a strong electric field drift layer forming step of forming the strong electric field drift layer 6 by oxidizing or nitriding the porous semiconductor layer 4. In the present embodiment, the strong electric field drift layer forming step constitutes a third step of forming the strong electric field drift layer by oxidizing or nitriding the porous semiconductor layer 4.

In the strong electric field drift layer forming step, when the porous semiconductor layer 4 is oxidized, for example, an oxidation containing an electrolyte solution made of a solution obtained by dissolving 0.04 mol / L potassium nitrate in an organic solvent consisting of ethylene glycol. Prepare a treatment tank. Thereafter, a counter electrode (not shown) made of a platinum electrode or the like is disposed in a state where the porous semiconductor layer 3 and the electrolyte solution are in contact with each other. Thereafter, a predetermined voltage is applied between the counter electrode and the first electrode 2 to cause a constant current having a second predetermined current density to flow, and the voltage between the counter electrode and the first electrode 2 becomes a specified voltage. The porous semiconductor layer 4 is electrochemically oxidized until it rises only. Thereby, in the strong electric field drift layer forming step, the strong electric field drift layer 6 including at least the grain 32, the microcrystalline semiconductor 33, the first insulating film 35, and the second insulating film 34 is formed. In the present embodiment, the second predetermined current density is 0.1 mA / cm ² and the specified voltage is 20 V. However, these numerical values are merely examples and are not particularly limited. Further, as a method for nitriding the porous semiconductor layer 4, for example, an electrochemical nitriding method can be employed.

  After the strong electric field drift layer 6 is formed, the resist layer is removed. Thereafter, an insulating layer forming step for forming the insulating layer 8 is performed, and then a second electrode forming step for forming the second electrode 7 is performed. In the present embodiment, the second electrode forming step constitutes a fourth step for forming the second electrode 7.

  After the second electrode forming step, the bus electrode forming step for forming the bus electrode 25 is performed, thereby obtaining the structure shown in FIG. Thereafter, a pad forming process for forming the pads 27 and 28, an organic substance removing process for removing organic substances on the surface of the second electrode 7 by irradiating the second electrode 7 with at least one of ultraviolet light and ozone. Thus, the field emission electron source 10 can be obtained. It should be noted that after forming a plurality of field emission electron sources 10 on one wafer at a wafer level, a dicing process for cutting into individual field emission electron sources 10 may be performed.

  In the insulating layer forming step, for example, after forming a silicon oxide film as a base of the insulating layer 8 by sputtering, the insulating layer 8 is formed by patterning the silicon oxide film using a photolithography technique and an etching technique. do it.

  In the second electrode formation step, for example, after forming a conductive film made of a laminated film of the first conductive layer and the second conductive layer serving as the basis of the second electrode 7 by vapor deposition or sputtering, photolithography technology Then, the second electrode 7 may be formed by patterning the conductive film using an etching technique.

  In the bus electrode formation step, for example, after forming a first metal film serving as the basis of the bus electrode 25 by vapor deposition or sputtering, the first metal film is patterned using photolithography technology and etching technology. Thus, the bus electrode 25 may be formed.

  In the pad forming step, for example, a second metal film that is the basis of the pads 27 and 28 is formed by vapor deposition or sputtering, and then the second metal film is patterned using photolithography technology and etching technology. Thus, the pads 27 and 28 may be formed.

  For the dicing step, for example, it is preferable to employ a dicing method using laser light. The dicing process is not necessarily an essential process.

  The structure of the field emission electron source 10 is such that the electron source is located at a lattice point of a matrix (lattice) composed of a plurality of groups of second electrodes 7 and a plurality of groups of first electrodes 2 as in the structure of FIG. The configuration is not limited to the configuration in which the element 10a is disposed, and may be a configuration in which only one electron source element 10a is provided. In this case, the bus electrode 25 is unnecessary.

  By the way, the inventors of the present application performed cross-sectional observation on the second electrode 7 using SEM (Scanning Electron Microscopy), and estimated the coverage of the second electrode 7 per unit area on the surface of the strong electric field drift layer 6. As a result, the inventors of the present application obtained an estimated value of 70% with respect to the above-described coverage. Then, the inventors of the present application have patterned the conductive film using a photolithography technique and an etching technique in the second electrode formation step, so that an organic solvent, a rinsing liquid, pure water, a photoresist are formed. It was inferred that the strong electric field drift layer 6 penetrated into the strong electric field drift layer 6 from a portion not covered with the second electrode 7 and remained in the strong electric field drift layer 6.

Therefore, the inventors of the present application considered performing a fifth step of removing impurities remaining in the strong electric field drift layer 6 using a supercritical fluid after the fourth step. The fifth step is a step for removing impurities composed of residual components such as an organic solvent, a rinsing liquid, pure water, and a photoresist used when removing a resist layer formed after the strong electric field drift layer forming step. If there is a bus electrode forming step and a pad forming step, these steps are performed after these steps. In short, in the method of manufacturing the field emission electron source 10 of the present embodiment, the fifth step is performed after the formation of the second electrode 7 is completed and the step of removing the resist such as the photoresist is completed.
In the fifth step, it is preferable to use a supercritical fluid of carbon dioxide as the supercritical fluid.

  FIG. 6 shows the electron emission characteristics of the field emission electron source 10 manufactured by the method of manufacturing the field emission electron source 10 of this embodiment and the field emission electron source manufactured by the manufacturing method of the comparative example. Yes. The manufacturing method of the comparative example is different from the manufacturing method of the field emission electron source of the embodiment only in that the fifth step is not performed.

  In FIG. 6, the horizontal axis represents the drive voltage Vps, the vertical axis represents the current density of the diode current Ips, A1 and A2 represent the electron emission characteristics of the field emission electron source of the comparative example, and the field emission electron source 10 of the embodiment. The electron emission characteristics of each are shown. That is, in FIG. 6, A1 (black circle) indicates the electron emission characteristics of the field emission electron source manufactured by the manufacturing method of the comparative example, and A2 (black square) indicates the field emission electron source 10 of the embodiment. The electron emission characteristic of the field emission type electron source 10 manufactured by the manufacturing method is shown.

  From FIG. 6, in the field emission type electron source 10 manufactured by the method of manufacturing the field emission type electron source 10 of the present embodiment, the field emission type manufactured by the manufacturing method of the comparative example when the drive voltage Vps is 12V or more. It can be seen that the current density of the diode current Ips is slightly smaller than that of the electron source. Also, from FIG. 6, in the field emission electron source 10 manufactured by the method of manufacturing the field emission electron source 10 of this embodiment, the electric field manufactured by the manufacturing method of the comparative example when the drive voltage Vps is less than 12V. It can be seen that the current density of the diode current Ips is smaller than that of the radiation electron source. In addition, the field emission electron source 10 manufactured by the method of manufacturing the field emission electron source 10 of the present embodiment can have a longer lifetime than the field emission electron source manufactured by the manufacturing method of the comparative example. It was confirmed. Therefore, the inventors of the present application have inferred that most of the current that flows when the drive voltage Vps is less than 12 V is caused by the leakage current. Further, in the field emission electron source 10 manufactured by the method of manufacturing the field emission electron source 10 of the present embodiment, the electron emission efficiency is improved as compared with the field emission electron source manufactured by the manufacturing method of the comparative example. It was confirmed that

  The inventors of the present application also have SIMS for each of the field emission electron source 10 manufactured by the method of manufacturing the field emission electron source 10 of the present embodiment and the field emission electron source manufactured by the manufacturing method of the comparative example. Comparison of impurity depth profiles by (Secondary Ion Mass Spectroscopy) was conducted. As a result, the field emission electron source 10 manufactured by the method of manufacturing the field emission electron source 10 of the present embodiment has a stronger electric field drift layer 6 than the field emission electron source manufactured by the manufacturing method of the comparative example. It was confirmed that the concentration of C and H in each was low. This is because C and H remaining in the strong electric field drift layer 6 due to an organic solvent, a rinsing liquid, pure water, a photoresist, and the like perform the fifth step, so that the strong electric field drift layer 6 It is presumed that this is due to the separation from the portion not covered with the second electrode 7.

  In the method of manufacturing the field emission electron source 10 according to the present embodiment described above, the impurities remaining in the strong electric field drift layer 6 before the fifth step are removed from the strong electric field drift by the fifth step. It becomes possible to reduce the structure of the layer 6 without destroying it, and it becomes possible to further improve the electron emission characteristics and the reliability.

  Further, in the method of manufacturing the field emission electron source 10 described above, it remains on the one surface side of the first electrode 2 between the second step and the third step and at least one stage after the third step. A supercritical drying step of removing the moisture and impurities (here, moisture and impurities remaining in the strong electric field drift layer 6) using a supercritical fluid may be provided. Thereby, in the manufacturing method of the field emission electron source 10 of this embodiment, it becomes possible to remove moisture and impurities in the strong electric field drift layer 6 without destroying the structure of the strong electric field drift layer 6. In the method of manufacturing the field emission electron source 10 as described above, it is possible to further improve the electron emission characteristics and the reliability.

  In the supercritical drying process, it is preferable to use a supercritical fluid of carbon dioxide as the supercritical fluid.

2 First electrode 3 Semiconductor layer 4 Porous semiconductor layer 6 Strong electric field drift layer 7 Second electrode 10 Field emission electron source

Claims (2)

  An electric field comprising a first electrode, a second electrode facing the first electrode, and a strong electric field drift layer between the first electrode and the second electrode, and capable of emitting electrons through the second electrode A method for manufacturing a radiation electron source, wherein a first step of forming a semiconductor layer on one surface side of the first electrode, and at least part of the semiconductor layer is made porous by anodizing treatment A second step of forming a porous semiconductor layer; a third step of forming the strong electric field drift layer by oxidizing or nitriding the porous semiconductor layer; and a fourth step of forming the second electrode. And a fifth step of removing impurities remaining in the strong electric field drift layer using a supercritical fluid after the fourth step. Production method.   Between the second step and the third step, a supercritical fluid is used for moisture and impurities remaining on the one surface side of the first electrode in at least one stage after the third step. The method of manufacturing a field emission electron source according to claim 1, further comprising a supercritical drying step of removing the step.

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