JP2003162959A - Manufacturing method of field emission type electron source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a field emission type electron source, having longer life service than that of conventional ones. <P>SOLUTION: In this manufacturing method of a field emission type electron source, at first a polycrystalline silicon layer 3 is formed on a lower electrode 12 (Fig. 1 (a)), and then a porous polycrystalline silicon layer 4 is formed by carrying an anode oxidation treatment process which makes the polycrystalline silicon layer 3 porous (Fig. 1 (b)), and further, a strong field drift layer 6 is formed by oxidizing the porous polycrystalline silicon layer 4 (Fig. 1 (c)). In the anodic oxidation treatment process using a treatment vessel filled with electrolyte, a current is made to flow between an electrode 12 and a cathode, while light emitted from an light source irradiates a surface of the polycrystalline silicon layer 3. Here, a current flowing between the electrode 12 and the cathode is made to gradually increase its current density up to a prescribed value during a time elapsed after starting, and then the current density is maintained at the prescribed value for a prescribed time, to finish energizing. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a field emission type electron source which emits an electron beam by field emission. 2. Description of the Related Art Conventionally, a lower electrode, a surface electrode made of a conductive thin film facing the lower electrode, and an oxidized porous semiconductor layer (porous silicon) interposed between the lower electrode and the surface electrode. A field emission type electron source having a strong electric field drift layer comprising a layer and a porous polycrystalline silicon layer) has been proposed. This type of field emission type electron source is, for example, as shown in FIG. A strong electric field drift layer 6 made of an oxidized porous polycrystalline silicon layer is formed on the main surface (one surface) side of an n-type silicon substrate 1 as a substrate.
A surface electrode 7 made of a metal thin film (for example, a gold thin film) is formed thereon. An ohmic electrode 2 is formed on the back surface of the n-type silicon substrate 1, and the n-type silicon substrate 1 and the ohmic electrode 2 constitute a lower electrode 12. In the example shown in FIG. 10, although the non-doped polycrystalline silicon layer 3 is interposed between the n-type silicon substrate 1 and the strong electric field drift layer 6, the n-type A configuration in which a strong electric field drift layer 6 is formed on the main surface of the silicon substrate 1 has also been proposed. A field emission type electron source 1 having a configuration shown in FIG.
In order to emit electrons from 0 ′, a collector electrode 21 disposed opposite to the surface electrode 7 is provided, and a vacuum is applied between the surface electrode 7 and the collector electrode 21. DC voltage Vps is applied between the surface electrode 7 and the lower electrode 12 so that
DC voltage Vc is applied between collector electrode 21 and surface electrode 7 so that collector electrode 21 is on the higher potential side with respect to surface electrode 7. If the DC voltages Vps and Vc are appropriately set, the electrons injected from the lower electrode 12 drift in the strong electric field drift layer 6 and are emitted through the surface electrode 7 (the dashed line in FIG. Shows the flow of electrons e ⁻ ). The thickness of the surface electrode 7 is 10 to
It is set to about 15 nm. The above-mentioned field emission type electron source 10 '
In this embodiment, the lower electrode 12 is composed of the n-type silicon substrate 1 and the ohmic electrode 2. As shown in FIG. 11, for example, the lower electrode 12 made of a metal material is formed on one surface of an insulating substrate 11 made of a glass substrate. A field emission type electron source 10 ″ having a 12 is also proposed. Here, the same components as those of the field emission type electron source 10 ′ shown in FIG. [0005] The field emission type electron source 1 having the structure shown in FIG.
In order to emit electrons from 0 ", a collector electrode 21 disposed opposite to the surface electrode 7 is provided, and the surface electrode 7 is DC voltage Vps is applied between the surface electrode 7 and the lower electrode 12 so that
DC voltage Vc is applied between collector electrode 21 and surface electrode 7 so that collector electrode 21 is on the higher potential side with respect to surface electrode 7. If the DC voltages Vps and Vc are appropriately set, electrons injected from the lower electrode 12 drift in the strong electric field drift layer 6 and are emitted through the surface electrode 7 (the dashed line in FIG. Shows the flow of electrons e ⁻ ). The electrons that have reached the surface of the strong electric field drift layer 6 are considered to be hot electrons and are easily tunneled through the surface electrode 7 and discharged into a vacuum. The above-mentioned field emission electron sources 10 ', 10 "
Then, the current flowing between the surface electrode 7 and the lower electrode 12 is called a diode current Ips, and the current flowing between the collector electrode 21 and the surface electrode 7 is called an emission current (emission electron current) Ie. (See FIGS. 10 and 11), the emission current I with respect to the diode current Ips
The larger the ratio of e (= Ie / Ips), the higher the electron emission efficiency (= (Ie / Ips) × 100 [%]). In the field emission electron sources 10 ′ and 10 ″ described above, electrons can be emitted even when the DC voltage Vps applied between the surface electrode 7 and the lower electrode 12 is as low as about 10 to 20 V. When the DC voltage Vps is higher, the emission current Ie is larger.In forming the strong electric field drift layer 6 in the above-described process of manufacturing the field emission electron sources 10 'and 10 ", a non-doped layer is formed on the lower electrode 12. After forming the polycrystalline silicon layer, the polycrystalline silicon layer is made porous by anodizing to form a porous polycrystalline silicon layer, and the porous polycrystalline silicon layer is subjected to a rapid thermal oxidation method or an electrochemical method. It is formed by oxidation by a conventional method. Here, in the anodic oxidation treatment, a polycrystalline silicon layer which is a semiconductor layer is made porous by flowing a current having a specified current density between the anode and the cathode using the lower electrode 12 as an anode in an electrolytic solution. A polycrystalline silicon layer is formed. In the field emission type electron source 10 ′ shown in FIG. 10, the polycrystalline silicon layer, which is a semiconductor layer formed on the n-type silicon substrate 1, is porous by anodizing using an electrolytic solution. However, the surface of the n-type silicon substrate is made porous by anodizing and then oxidized by using the single-crystal n-type silicon substrate as a semiconductor layer and oxidizing the surface of the n-type silicon substrate. A field emission electron source having a strong electric field drift layer has also been proposed. By the way, in the above-described anodic oxidation treatment, the semiconductor layer is made porous by flowing a current having the above specified current density for a predetermined time between the anode and the cathode.
The current density of the current flowing between the anode and the cathode at the start of energization between the anode and the cathode is immediately adjusted to the specified current density. [0010] However, the field emission type electron source 1 manufactured by employing the above-described manufacturing process.
In the case of 0 ′, 10 ″, there was a problem that the life was short when considering industrial use. Here, the cause of the short life of the field emission electron sources 10 ′, 10 ″ was polycrystalline. Fine irregularities due to a large number of fine holes are formed on the surface of the porous polycrystalline silicon layer formed by making the silicon layer porous by the above-described anodic oxidation treatment. As a result, the surface of the strong electric field drift layer 6 is formed. It is conceivable that fine irregularities are formed, the distribution of the electric field applied to the strong electric field drift layer 6 becomes non-uniform in the plane, and the deterioration is accelerated in the electric field concentrated portion, thereby shortening the life. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method of manufacturing a field emission type electron source that can have a longer life than conventional ones. According to a first aspect of the present invention, there is provided a strong electric field drift layer comprising a lower electrode and an oxidized, nitrided or oxynitrided porous semiconductor layer formed on one surface of the lower electrode. And a surface electrode formed on the strong electric field drift layer, and electrons injected from the lower electrode drift through the strong electric field drift layer by applying a voltage between the surface electrode and the lower electrode, and pass through the surface electrode. A method for manufacturing a field emission electron source to be emitted, wherein in forming the strong electric field drift layer, an anode having a specified current density flowing between an anode and a cathode in an electrolyte with a lower electrode serving as an anode. Anodizing treatment step of forming a porous semiconductor layer by making the semiconductor layer on the one surface side of the lower electrode porous by oxidation treatment,
Oxidizing, nitriding, or oxynitriding the porous semiconductor layer. In the anodizing step, energization is started so that a current flows between the anode and the cathode, and the current density of the current is increased to the specified current. Characterized in that the density gradually increases with time, and in the anodizing treatment step, energization is started so that a current flows between the anode and the cathode, and the current density of the current is reduced until the specified current density. Gradually increases with the passage of time, so that the porosity near the outermost surface of the porous semiconductor layer formed in the anodic oxidation treatment step is reduced, and fine irregularities on the surface of the porous semiconductor layer due to the anodic oxidation treatment step are reduced. As a result, the surface roughness of the strong electric field drift layer becomes smaller than that of the conventional device, and the surface of the strong electric field drift layer is caused by fine irregularities during electron emission. Since the the electric field concentration can be prevented, it is possible to provide a long field emission electron source of life as compared with the prior art. DESCRIPTION OF THE PREFERRED EMBODIMENTS In a field emission type electron source 10 described in this embodiment, a single-crystal n-type silicon substrate (for example, a resistor) having a resistivity relatively close to that of a conductor is used as a conductive substrate. (100) with a rate of approximately 0.01 Ωcm to 0.02 Ωcm
Substrate). As shown in FIG. 3, a field emission type electron source 10 according to the present embodiment has a strong electric field drift layer made of an oxidized porous polycrystalline silicon layer on the main surface side of an n-type silicon substrate 1 as a conductive substrate. 6, a surface electrode 7 is formed on the strong electric field drift layer 6, and an ohmic electrode 2 is formed on the back surface of the n-type silicon substrate 1. In this embodiment, the lower electrode 12 is composed of the n-type silicon substrate 1 and the ohmic electrode 2. Therefore, the surface electrode 7 faces the lower electrode 12, and the strong electric field drift layer 6 is interposed between the lower electrode 12 and the surface electrode 7. Further, the porous polycrystalline silicon layer forms a porous semiconductor layer. A material having a small work function is adopted as the material of the surface electrode 7, and the thickness of the surface electrode 7 is set to 10 nm. However, the thickness is not particularly limited. The thickness of the surface electrode 7 may be set to about 10 to 15 nm as long as the electron passing through 6 can be tunneled. In order to emit electrons from the field emission type electron source 10 having the structure shown in FIG. 3, a collector electrode 21 disposed opposite to the surface electrode 7 is provided as shown in FIG. 21 and a DC voltage Vps is applied between the surface electrode 7 and the lower electrode 12 so that the surface electrode 7 is on the higher potential side with respect to the lower electrode 12. Is applied between the collector electrode 21 and the surface electrode 7 so that the voltage Vc is on the high potential side with respect to the surface electrode 7. If the DC voltages Vps and Vc are appropriately set, the electrons injected from the lower electrode 12 drift in the strong electric field drift layer 6 and are emitted through the surface electrode 7 (the dashed line in FIG. Shows the flow of electrons e ⁻ ). The field emission type electron source 10 according to this embodiment
Then, the current flowing between the surface electrode 7 and the lower electrode 12 is called a diode current Ips, and the current flowing between the collector electrode 21 and the surface electrode 7 is called an emission current (emission electron current) Ie. (See FIG. 4), the ratio of the emission current Ie to the diode current Ips (= I
e / Ips), the electron emission efficiency (= (Ie / Ip)
s) × 100 [%]). In the field emission type electron source 10 of the present embodiment, the surface electrode 7 and the lower electrode 12
Can emit electrons even when the DC voltage Vps applied between them is as low as about 10 to 20 V.
The emission current Ie increases as ps increases. As shown in FIG. 5, the strong electric field drift layer 6 in this embodiment is arranged at least on the main surface side of the n-type silicon substrate 1 (ie, on the surface electrode 7 side of the lower electrode 12). Columnar polycrystalline silicon grains 51, a thin silicon oxide film 52 formed on the surfaces of the grains 51, a number of nanometer-order silicon microcrystals 63 interposed between the grains 51, and a surface of each silicon microcrystal 63. And a large number of silicon oxide films 64 which are insulating films having a thickness smaller than the crystal grain size of the silicon microcrystal 63. In short, in the strong electric field drift layer 6, the surface of each grain of the polycrystalline silicon layer is made porous, and the crystalline state is maintained at the center of each grain. Each of the grains 51 extends in the thickness direction of the lower electrode 12. Therefore, in the field emission type electron source 10 of the present embodiment, it is considered that electron emission occurs in the following model. That is, the surface electrode 7 is arranged in a vacuum, the DC voltage Vps is applied between the surface electrode 7 and the lower electrode 12 with the surface electrode 7 on the high potential side, and the collector electrode 2
By applying the DC voltage Vc between the first electrode 1 and the surface electrode 7 with the collector electrode 21 on the high potential side, the DC voltage Vps
Reaches a predetermined value (critical value), electrons e ⁻ are injected from lower electrode 12 (n-type silicon substrate 1) into strong electric field drift layer 6 by thermal excitation. On the other hand, most of the electric field applied to the strong electric field drift layer 6 is applied to the silicon oxide film 64, so that the injected electrons e ⁻ are accelerated by the strong electric field applied to the silicon oxide film 64, and 5 drifts toward the surface in the direction between the grains 51 in the direction of the arrow in FIG. 5 (upward in FIG. 5), and tunnels through the surface electrode 7 and is discharged into a vacuum. In the strong electric field drift layer 6, electrons injected from the lower electrode 12 are hardly scattered by the silicon microcrystal 63,
The electron is accelerated by the strong electric field applied to the silicon oxide film 64, drifts and is emitted through the surface electrode 7 (ballistic electron emission phenomenon), and the heat generated in the strong electric field drift layer 6 is radiated through the grains 51, so that electron emission is performed. It is considered that the popping phenomenon does not sometimes occur and electrons can be stably emitted. The electrons that have reached the surface of the strong electric field drift layer 6 are considered to be hot electrons.
The surface electrode 7 is easily tunneled and released into a vacuum. Hereinafter, the field emission type electron source 10 of this embodiment will be described.
Will be described with reference to FIG. First, an ohmic electrode 2 is formed on the back surface of an n-type silicon substrate 1, and then a non-doped polycrystalline silicon layer 3 is formed as a semiconductor layer on the main surface (one surface) of the n-type silicon substrate 1. By performing the process, FIG.
The structure as shown in FIG. As a method for forming the polycrystalline silicon layer 3, for example, a CVD method (for example, an LPCVD method, a plasma CVD method, a catalytic CVD method, etc.), a sputtering method, or a CGS (Continuous Grain Silicate) is used.
on) method or the like. After the non-doped polycrystalline silicon layer 3 is formed, an anodic oxidation step of making the polycrystalline silicon layer 3 which is a semiconductor layer to be anodized porous by anodizing using an electrolytic solution is performed. As a result, a porous polycrystalline silicon layer 4 as a porous semiconductor layer is formed.
The structure as shown in FIG. Here, the porous polycrystalline silicon layer 4 formed by the anodic oxidation process
Is a large number of polycrystalline silicon grains 51 (see FIG. 5).
And a number of silicon microcrystals 63 (see FIG. 5). In the anodizing step, a processing tank containing an electrolytic solution composed of a mixture of a 55 wt% aqueous solution of hydrogen fluoride and ethanol in a ratio of about 1: 1 is used.
A current is passed between the lower electrode 12 and the cathode composed of a platinum electrode while irradiating light to the surface of the polycrystalline silicon layer 3 with a light source composed of a 0 W tungsten lamp so that the polycrystalline silicon layer 3 is n-type from the main surface. It is made porous to a depth reaching the silicon substrate 1. Here, the current density of the current flowing between the lower electrode 12 and the cathode is changed as shown in FIG. That is, energization is started so that a current flows between the lower electrode 12 and the cathode, and the current density is gradually increased to a specified current density I1 (for example, 25 mA / cm ² ) with the passage of time. Is maintained for the specified time T2 (for example, 3 seconds), and the energization is terminated. The time T1 (see FIG. 2) from the start of energization to the time when the current density reaches I1 may be set to, for example, about 1 second. After the above-described anodizing step is completed,
After rinsing with ethanol, an oxidation step of oxidizing the porous polycrystalline silicon layer 4 is performed, whereby semiconductor crystals (each grain 51 and each silicon microcrystal 63) included in the porous polycrystalline silicon layer 4 are removed. By forming the silicon oxide films 52 and 64 on the surface, the strong electric field drift layer 6 including the grains 51, the silicon microcrystals 63, and the silicon oxide films 52 and 64 is formed. By performing the heat treatment step, FIG.
The structure as shown in (c) is obtained. Here, in the oxidation step, after rinsing with ethanol after the completion of the above-described porous step, a predetermined concentration (for example, 1 mol
/ L = 1M) using a treatment tank containing an aqueous solution of sulfuric acid, and applying each of the grains 51 and each of the silicon microcrystals 63 by an electrochemical method of applying a constant voltage between the lower electrode 12 and the cathode made of a platinum electrode. Silicon oxide film 5 on each surface
2, 64 are formed. In the heat treatment step, the first heat treatment is performed at a first set temperature and a temperature increasing rate (for example, 20 ° C./sec or less) set so that moisture contained in the silicon oxide films 52 and 64 is removed without bumping. After that, the silicon oxide films 52 and 6 are heated to a temperature higher than the first set temperature.
The second heat treatment is performed at the second set temperature set so that the structural relaxation of No. 4 occurs. In the heat treatment step, the first heat treatment is performed in an oxygen gas atmosphere (that is, an atmosphere containing an oxidizing species) using a lamp annealing apparatus.
Is set at 450 ° C. and the heat treatment time is set at 1 hour. The second heat treatment is performed in an oxygen gas atmosphere (that is, an atmosphere containing an oxidizing species), the second set temperature is set to 900 ° C., and the heat treatment time is set to 20 minutes.
Further, in this embodiment, a rapid heat treatment method is employed as the second heat treatment, and the heating rate during the heating period in which the substrate temperature is increased from the first set temperature to the second set temperature is set to 150.
° C / sec (the heating rate during this heating period may be set to 20 ° C / sec or more;
/ Sec or more is desirable). After the strong electric field drift layer 6 is formed, a surface electrode 7 made of a metal material (for example, gold) is formed by a vapor deposition method or the like, so that the field emission type electron source having the structure shown in FIG. 10 is obtained. In the present embodiment, the surface electrode 7 is formed by a vapor deposition method, but the method of forming the surface electrode 7 is not limited to the vapor deposition method, and for example, a sputtering method may be used. According to the above-described manufacturing method, in the anodic oxidation step, energization is started so that a current flows between the lower electrode 12 serving as the anode and the cathode, and the current density of the current is adjusted to the specified current density. I1 (see FIG. 2) gradually increases with time, so that the porous polycrystalline silicon layer 4 as a porous semiconductor layer formed in the anodic oxidation step is formed.
Of the porous polycrystalline silicon layer 4 due to the anodic oxidation process can be suppressed, and as a result, the strong electric field drift layer 6 can be prevented.
Of the field emission type electron source having a longer life than the conventional one because the surface roughness of the electron source can be reduced as compared with the prior art, and the electric field concentration caused by the minute unevenness on the surface of the strong electric field drift layer 6 during electron emission can be prevented. 10 can be provided. FIG. 6 shows the results of measuring the change over time in the electron emission characteristics of the field emission electron source 10 manufactured by the above-described manufacturing method. FIG. 7 shows the results immediately after the start of energization in the anodizing step. The result of measuring the change over time of the electron emission characteristics of a comparative example manufactured by supplying a current of a specified current density I1 and maintaining the current for the specified time is shown. The electron emission characteristics of the field emission type electron source 10 and the field emission type electron source of the comparative example are measured by introducing the field emission type electron source 10 or the field emission type electron source of the comparison example into a vacuum chamber (not shown). hand,
As shown in FIG. 4 described above, the collector electrode 21 is arranged to face the surface electrode 7, the DC voltage Vps is applied while the surface electrode 7 is on the high potential side with respect to the lower electrode 12, and the collector electrode 21 is 7 was performed by applying a DC voltage Vc as the high potential side. 6 and 7 show that the above-mentioned DC voltage Vc is constant at 100 V, the above-mentioned DC voltage Vps is constant at 16 V, and the degree of vacuum in the vacuum chamber is 5 × 10 ^−5.
It shows the measurement results of the electron emission characteristics when Pa, the horizontal axis of each figure is the elapsed time from the start of energization, the left vertical axis is the current density, the right vertical axis is the electron emission efficiency. ,
“A” indicates the current density of the diode current Ips, “B” indicates the current density of the emission current Ie, and “C” indicates the electron emission efficiency. From FIGS. 6 and 7, it can be seen that the field emission electron source 10 of the present embodiment has a longer elapsed time until dielectric breakdown and a longer life than the field emission electron source of the comparative example. . In the present embodiment, the lower electrode 12 is composed of the n-type silicon substrate 1 and the ohmic electrode 2. However, a metal surface is provided on one surface side of an insulating substrate (eg, a glass substrate, a ceramic substrate, etc.). A configuration in which the lower electrode 12 made of a material or a highly doped polycrystalline silicon layer may be employed. Further, a part of the surface side of the n-type silicon substrate is made porous by using the n-type silicon substrate 1 as a semiconductor layer in the above-described anodic oxidation process to form a polycrystalline silicon layer as a porous semiconductor layer. The porous silicon layer may be oxidized in the above-described oxidation step. In this embodiment, the strong electric field drift layer 6 is constituted by an oxidized porous polycrystalline silicon layer. However, the strong electric field drift layer 6 is formed by nitriding the porous polycrystalline silicon layer or the oxynitrided porous polycrystalline silicon layer. It may be composed of a polycrystalline silicon layer, or may be composed of another oxidized, nitrided or oxynitrided porous semiconductor layer.
When the strong electric field drift layer 6 is a nitrided porous polycrystalline silicon layer, the porous polycrystalline silicon layer is nitrided instead of the oxidation step of oxidizing the porous polycrystalline silicon layer formed in the porous process. In the case where each of the silicon oxide films 52 and 64 described with reference to FIG. 5 is a silicon nitride film and the strong electric field drift layer 6 is a porous polycrystalline silicon layer oxynitrided, An oxynitriding step of oxynitriding the porous polycrystalline silicon layer may be employed instead of the oxidizing step of oxidizing the porous polycrystalline silicon layer formed in the porous forming step, and each silicon oxide film described with reference to FIG. Both 52 and 64 become silicon oxynitride films. According to the first aspect of the present invention, there is provided a lower electrode, a strong electric field drift layer formed of an oxidized, nitrided or oxynitrided porous semiconductor layer formed on one surface side of the lower electrode,
A surface electrode formed on the strong electric field drift layer, and by applying a voltage between the surface electrode and the lower electrode, electrons injected from the lower electrode drift in the strong electric field drift layer and are emitted through the surface electrode. A method of manufacturing a field emission type electron source, wherein the strong electric field drift layer is formed by anodizing treatment in which a current having a specified current density is passed between an anode and a cathode with a lower electrode serving as an anode in an electrolytic solution. An anodic oxidation step of forming a porous semiconductor layer by making the semiconductor layer on the one surface side of the lower electrode porous, and a step of oxidizing or nitriding or oxynitriding the porous semiconductor layer,
In the anodic oxidation step, current is started so that a current flows between the anode and the cathode, and the current density of the current is gradually increased with the passage of time to the specified current density. In the processing step, current is started so that a current flows between the anode and the cathode, and the current density of the current is gradually increased with the passage of time to the specified current density. The porosity in the vicinity of the outermost surface of the porous semiconductor layer becomes low, and the formation of fine irregularities on the surface of the porous semiconductor layer due to the anodic oxidation step can be suppressed. As a result, the surface of the strong electric field drift layer Roughness is smaller than before, and it is possible to prevent electric field concentration due to fine irregularities on the surface of the strong electric field drift layer during electron emission, so that the life is longer than before. There is an effect that it is possible to provide a field emission electron source.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a main process sectional view for describing a method of manufacturing a field emission electron source according to an embodiment. FIG. 2 is an explanatory diagram of a manufacturing method according to the embodiment. FIG. 3 is a schematic cross-sectional view of the field emission electron source according to the first embodiment. FIG. 4 is an operation explanatory diagram of the above. FIG. 5 is an operation explanatory view of the above. FIG. 6 is an electron emission characteristic diagram of the field emission electron source of the above. FIG. 7 is an electron emission characteristic diagram of the field emission type electron source showing the comparative example. FIG. 8 is an operation explanatory diagram of a field emission type electron source showing a conventional example. FIG. 9 is an operation explanatory view of a field emission type electron source showing another conventional example. [Description of Signs] 1 n-type silicon substrate 2 ohmic electrode 3 polycrystalline silicon layer 4 porous polycrystalline silicon layer 6 strong electric field drift layer 7 surface electrode 10 field emission electron source 12 lower electrode

Continuation of front page    (72) Inventor Nobuyoshi Koshida             6-5-10-203, Josuihoncho, Kodaira-shi, Tokyo

Claims (1)

Claims: 1. A lower electrode, a strong electric field drift layer formed of an oxidized, nitrided, or oxynitrided porous semiconductor layer formed on one surface side of the lower electrode; A field emission type electron source comprising a formed surface electrode, and by applying a voltage between the surface electrode and the lower electrode, electrons injected from the lower electrode drift in the strong electric field drift layer and are emitted through the surface electrode. In the method of forming the strong electric field drift layer, the lower electrode is formed by anodizing treatment in which a current having a specified current density is passed between the anode and the cathode using the lower electrode as an anode in an electrolytic solution. An anodic oxidation step of forming a porous semiconductor layer by making the semiconductor layer on one surface porous, and a step of oxidizing, nitriding, or oxynitriding the porous semiconductor layer; Producing a field emission type electron source, wherein current is started so that a current flows between the anode and the cathode, and the current density of the current is gradually increased to the specified current density with the passage of time. Method.