JP2001118498A - Electric field radiation electron source and method for fabricating it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for fabricating an electric field radiation electron source with high insulating internal pressure that the aging change of the electron emission efficiency is less. SOLUTION: A strong electric field drift layer 6 made of an oxidized porous polycrystalline silicon layer is deposited on the main surface of a conductive n-type silicon substrate 1, having a surface electrode 7 formed thereon. An ohmic electrode 2 is formed in the inside of the n-type silicon substrate 1. The drift layer 6 has an oxide layer of a dense SiO2 structure or a structure near to it obtained by heat-treating the porous polycrystalline silicon layer 4 formed by oxidizing the polycrystalline silicon layer 3 with the anode. Thus, the amount of hydrogen entering the drift layer 6 becomes less to prevent degradation of the electron emission efficiency caused by the aging change of the hydrogen distribution as well as enhancing the withstand voltage because of the dense oxide layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission type electron source which emits an electron beam by field emission using a semiconductor material, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a field emission type electron source, there is a so-called Spindt electrode disclosed in, for example, US Pat. No. 3,665,241. This Spindt-type electrode has a substrate on which a number of minute triangular pyramid-shaped emitter chips are arranged, a gate layer having a radiation hole for exposing the tip of the emitter chip, and being arranged insulated from the emitter chip. And applying a high voltage with the emitter tip as a negative electrode to the gate layer in a vacuum to emit an electron beam from the tip of the emitter tip through a radiation hole.

However, the Spindt-type electrode has a complicated manufacturing process, and it is difficult to accurately form a large number of triangular pyramid-shaped emitter chips. For example, the Spindt-type electrode has a large area when applied to a flat light emitting device or a display. There was a problem that was difficult. In the Spindt-type electrode, the electric field is concentrated at the tip of the emitter tip, so if the degree of vacuum around the tip of the emitter tip is low and residual gas is present, the emitted gas turns the residual gas into positive ions. Since the ions are ionized and the positive ions collide with the tip of the emitter tip, the tip of the emitter tip is damaged (for example, damage due to ion bombardment), and the current density and efficiency of emitted electrons become unstable. There is a problem that the life of the chip is shortened. Therefore, the Spindt-type electrode needs to be used in a high vacuum (about 10 ^-5 Pa to about 10 ^-6 Pa) in order to prevent such a problem from occurring, which increases the cost and complicates handling. There was a problem.

In order to improve this kind of problem, MIM
(Metal Insulator Metal) method and MOS (Metal Oxid
e Semiconductor) type field emission electron sources have been proposed. The former is a flat field emission type electron source having a metal-insulating film-metal structure, and the latter is a metal-oxide film-semiconductor stacked structure. However, in order to increase the electron emission efficiency (to emit many electrons) in this type of field emission electron source, it is necessary to reduce the thickness of the insulating film or the oxide film. If the thickness of the insulating film or the oxide film is too thin, dielectric breakdown may occur when a voltage is applied between the upper and lower electrodes of the laminated structure. Since the thickness of the insulating film or the oxide film is limited, the electron emission efficiency (drawing efficiency) cannot be increased.

On the other hand, in recent years, as a field emission type electron source capable of increasing the electron emission efficiency, a single-crystal semiconductor such as a silicon substrate has recently been disclosed as disclosed in Japanese Patent Application Laid-Open No. 8-250766. Using a substrate, one surface of the semiconductor substrate is anodized to form a porous semiconductor layer (porous silicon layer), and a surface electrode made of a metal thin film (conductive thin film) is formed on the porous semiconductor layer. In addition, a field emission type electron source (semiconductor cold electron emission element) configured to emit electrons by applying a voltage between a semiconductor substrate and a surface electrode has been proposed.

[0006] However, the above-mentioned Japanese Patent Application Laid-Open No. Hei 8-2507 has been disclosed.
In the field emission type electron source described in Japanese Patent Publication No. 66, so-called popping phenomenon easily occurs at the time of electron emission, and the amount of emitted electrons tends to be uneven. Therefore, when applied to a flat light emitting device or a display device, uneven light emission occurs. There is a problem that.

[0007] The inventors of the present application have proposed a technique disclosed in Japanese Patent Application No. Hei 10-2.
No. 72340, Japanese Patent Application No. 10-272342,
Rapid thermal oxidation of a porous polycrystalline semiconductor layer (eg, a porous polycrystalline silicon layer) by a rapid thermal oxidation (RTO) technique intervenes between a conductive substrate and a metal thin film (surface electrode). We have proposed a field emission type electron source with a strong electric field drift layer in which electrons injected from a conductive substrate drift. In the field emission type electron source 10 ', for example, as shown in FIG. 5, a strong electric field drift layer 6' made of an oxidized porous polycrystalline silicon layer is formed on the main surface side of an n-type silicon substrate 1 as a conductive substrate. And a surface electrode 7 made of a metal thin film is formed on the strong electric field drift layer 6 '.
An ohmic electrode 2 is formed on the back surface of the silicon substrate 1.

A field emission type electron source 10 'having the structure shown in FIG.
Then, the surface electrode 7 is arranged in a vacuum, the collector electrode 21 is arranged opposite to the surface electrode 7, and the DC voltage Vps is applied using the surface electrode 7 as a positive electrode with respect to the n-type silicon substrate 1 (ohmic electrode 2). At the same time, by applying a DC voltage Vc with the collector electrode 21 as a positive electrode to the surface electrode 7, electrons injected from the n-type silicon substrate 1 drift in the strong electric field drift layer 6 ′ and are emitted through the surface electrode 7. (Note that the dashed line in FIG. 5 indicates the flow of electrons e ⁻ emitted through the surface electrode 7). Therefore, it is desirable to use a material having a small work function as the surface electrode 7. Here, a current flowing between the surface electrode 7 and the n-type silicon substrate 1 (the ohmic electrode 2) is called a diode current Ips, and a current flowing between the collector electrode 21 and the surface electrode 7 is called an emission electron current Ie. The larger the emission electron current Ie with respect to the diode current Ips (the larger Ie / Ips), the higher the electron emission efficiency. In this field emission type electron source 10 ', electrons can be emitted even when the DC voltage Vps applied between the surface electrode 7 and the ohmic electrode 2 is as low as about 10 to 20V.

In the field emission type electron source 10 ', the electron emission characteristics have a small dependence on the degree of vacuum and the electrons can be stably emitted with a high electron emission efficiency without generating a popping phenomenon during electron emission. Here, as shown in FIG. 6, the strong electric field drift layer 6 ′ includes at least a columnar polycrystalline silicon 51 (grain), a thin silicon oxide film 52 formed on the surface of the polycrystalline silicon 51, and a polycrystalline silicon 51. A nanometer-order microcrystalline silicon layer 63 interposed between the silicon 51 and a silicon oxide film 64 formed on the surface of the microcrystalline silicon layer 63 and serving as an insulating film having a thickness smaller than the crystal grain size of the microcrystalline silicon layer 63; It is considered to be composed of That is, in the strong electric field drift layer 6 ', it is considered that the surface of each grain is porous and the crystalline state is maintained in the central portion of each grain. Therefore, most of the electric field applied to the strong electric field drift layer 6 ′ is applied to the silicon oxide film 64, and the injected electrons are accelerated by the strong electric field applied to the silicon oxide film 64 and travel between the polycrystalline silicon 51 toward the surface. 6 drifts in the direction of arrow A in FIG. 6 (upward in FIG. 6), so that the electron emission efficiency can be improved. 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. Here, the film thickness of the surface electrode 7 is 10 n
It is set to about m to 15 nm.

[0010] If a substrate in which a conductive layer made of, for example, an ITO film is formed on an insulating substrate such as a glass substrate is used instead of the semiconductor substrate such as the n-type silicon substrate 1 as the conductive substrate, the The area of the source can be increased and the cost can be reduced.

Incidentally, the above-mentioned field emission type electron source 10 '
Then, after the strong electric field drift layer 6 ′ deposits a non-doped polycrystalline silicon layer on the n-type silicon substrate 1, which is a conductive substrate, the polycrystalline silicon layer is made porous by anodizing treatment, The converted polycrystalline silicon layer (porous polycrystalline silicon layer) is heated at 900 ° C. by a rapid heating method.
Formed by oxidation at a temperature of Here, as the electrolytic solution used for the anodic oxidation treatment, a solution obtained by mixing a hydrogen fluoride aqueous solution and ethanol at a ratio of about 1: 1 is used. In the step of oxidizing by the rapid heating method,
Using a lamp annealing apparatus, the substrate temperature is raised from room temperature to 900 ° C. in dry oxygen as shown in FIG. 7, and then oxidized by maintaining the substrate temperature at 900 ° C. for 1 hour. Down.

[0012]

As described above, the porous polycrystalline silicon layer formed by the anodic oxidation treatment uses a mixture of an aqueous solution of hydrogen fluoride and ethanol as an electrolyte in the anodic oxidation treatment. Therefore, the outermost surface of the porous polycrystalline silicon layer is terminated by hydrogen atoms as shown in FIG. For this reason, when the porous polycrystalline silicon layer formed by the anodic oxidation treatment is oxidized at 900 ° C. in a temperature profile as shown in FIG. 7, as shown in FIG. 9, hydrogen atoms remain or Si—OH Or the like, and a dense oxide film having a structure of SiO ₂ is hardly formed and the dielectric strength voltage is lowered. Further, the content of hydrogen in the strong electric field drift layer 6 ′ becomes relatively large, and the distribution of hydrogen in the strong electric field drift layer 6 ′ changes with time (for example, hydrogen atoms are removed from the surface of the strong electric field drift layer 6 ′). Desorption), the stability over time of the electron emission efficiency may be deteriorated.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a field emission type electron source having a small change with time in electron emission efficiency and a high withstand voltage, and a method of manufacturing the same. .

[0014]

According to a first aspect of the present invention, there is provided a strong electric field comprising a conductive substrate and an oxidized porous semiconductor layer formed on one surface of the conductive substrate. A drift layer and a surface electrode formed of a conductive thin film formed on the strong electric field drift layer, and electrons injected from the conductive substrate by applying a voltage with the surface electrode being a positive electrode with respect to the conductive substrate. Is a method of manufacturing a field emission type electron source that drifts through a strong electric field drift layer and is emitted through a surface electrode, comprising: forming a semiconductor layer on a conductive substrate; and anodizing the at least one of the semiconductor layers. Forming a porous semiconductor layer by making the portion porous, removing hydrogen atoms bonded to the surface of the porous semiconductor layer by heat treatment, and removing the hydrogen atoms from the porous semiconductor layer after removing the hydrogen atoms. Semiconduct A step of forming a strong electric field drift layer by oxidizing the layer and a step of forming a surface electrode made of a conductive thin film on the strong electric field drift layer, and bonding to a surface of the porous semiconductor layer. Since a strong electric field drift layer is formed by oxidizing the porous semiconductor layer after desorbing hydrogen atoms by heat treatment, the strong electric field drift layer is formed as compared with the case where the porous semiconductor layer is oxidized immediately after the anodic oxidation treatment. It is possible to reduce the amount of hydrogen contained in the drift layer, form a dense oxide film, and realize a field emission electron source with a small change with time in electron emission efficiency and a high withstand voltage. it can.

In a preferred embodiment, the heat treatment is performed at a temperature in the range of 300 ° C. to 700 ° C.

According to a third aspect of the present invention, in the first or second aspect of the invention, the step of oxidizing the porous semiconductor layer is a step of annealing in an oxygen atmosphere, so that the insulating property is high and the physical properties are stable. An oxide film can be formed.

According to a fourth aspect of the present invention, in the first or second aspect, the step of oxidizing the porous semiconductor layer is a step of electrochemically oxidizing the porous semiconductor layer with an acid. Thus, the strong electric field drift layer can be formed at a low temperature, the process temperature becomes low, the restriction on the conductive substrate is reduced, and the area and cost can be easily reduced.

According to a fifth aspect of the present invention, in the first or second aspect of the invention, the step of oxidizing the porous semiconductor layer is a step of oxidizing using an oxygen plasma. The strong electric field drift layer can be formed at a low temperature, the process temperature becomes low, the restriction on the conductive substrate is reduced, and the area and cost can be easily reduced.

According to a sixth aspect of the present invention, in the first or second aspect of the present invention, the step of oxidizing the porous semiconductor layer is a step of oxidizing using a ozone gas.
The invention makes it possible to form a strong electric field drift layer at a lower temperature as compared with the invention of the first aspect, so that the process temperature becomes lower, the restriction on the conductive substrate is reduced, and the area and cost can be easily reduced.

According to a seventh aspect of the present invention, the porous semiconductor layer is manufactured by the manufacturing method according to any one of the first to sixth aspects. In comparison with the field emission type electron source in which the strong electric field drift layer is formed, the mixing of hydrogen into the strong electric field drift layer is less, so that the decrease in the electron emission efficiency due to the temporal change of the hydrogen distribution as in the conventional case is reduced. In addition, the oxide film tends to be dense and the withstand voltage is high.

[0021] The invention of claim 8 is the invention of claim 7, wherein the porous semiconductor layer, which has the porous polycrystalline silicon layer, the strong electric field drift layer is close to the structure or the SiO ₂ structure of SiO ₂ It has an oxide film with high density.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In this embodiment, a method for manufacturing a field emission type electron source 10 having the structure shown in FIG. 4 will be described with reference to FIGS. In the present embodiment,
As a conductive substrate, a single-crystal n-type silicon substrate 1 having a resistivity relatively close to that of a conductor (for example, a resistivity of approximately 0.0
A (100) substrate of 1 Ωcm to 0.02 Ωcm) is used.

The basic configuration of the field emission type electron source 10 of this embodiment is the same as the conventional configuration shown in FIG. 5, and as shown in FIG. 4, the main surface of the n-type silicon substrate 1 which is a conductive substrate. A strong electric field drift layer 6 made of an oxidized porous polycrystalline silicon layer is formed on the side, a surface electrode 7 made of a metal thin film 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. Are formed.

In the field emission type electron source 10 having the structure shown in FIG. 4, the surface electrode 7 is arranged in a vacuum and the collector electrode 21 is arranged opposite to the surface electrode 7 in the same manner as in the above-mentioned conventional structure. 7 is applied to the n-type silicon substrate 1 (ohmic electrode 2) as a positive electrode, and a DC voltage Vps is applied to the collector electrode 21 as a positive electrode to the surface electrode 7. The electrons injected from 1 drift in the strong electric field drift layer 6 and are emitted through the surface electrode 7 (the dashed line in FIG. 4 indicates the flow of electrons e ⁻ emitted through the surface electrode 7). Therefore, it is desirable to use a material having a small work function as the surface electrode 7. Here, a current flowing between the surface electrode 7 and the n-type silicon substrate 1 (the ohmic electrode 2) is referred to as a diode current Ips,
The current flowing between the collector electrode 21 and the surface electrode 7 is referred to as an emission electron current Ie. The electron emission efficiency increases as the emission electron current Ie with respect to the diode current Ips increases (Ie / Ips increases). In the field emission type electron source 10 of the present embodiment, as in the above-described conventional configuration, electrons are emitted even when the DC voltage Vps applied between the surface electrode 7 and the ohmic electrode 2 is set to a low voltage of about 10 to 20 V. Can be released.

In the present embodiment, the strong electric field drift layer 6
Compared with the strong electric field drift layer 6 'in the above-described conventional configuration, the present embodiment is characterized in that a small amount of hydrogen is mixed therein and a dense oxide film is provided.
Oxide film here is, in the above-mentioned conventional configuration is the silicon oxide film 52, 64 described in FIG. 6, the oxide film in this embodiment is dense film close to the structure close to the structure or the SiO ₂ structure of SiO ₂ It has become.

However, in the field emission type electron source 10 of the present embodiment, the decrease in the electron emission efficiency due to the temporal change of the hydrogen distribution as in the conventional case is small because the mixing of hydrogen into the strong electric field drift layer 6 is small. Also, since the oxide film becomes denser than before, the withstand voltage is high.

In this embodiment, the n-type silicon substrate 1 is used as the conductive substrate. However, a metal substrate such as chromium may be used instead of the n-type silicon substrate 1, or an insulating substrate such as a glass substrate may be used. A substrate in which a conductive layer (for example, an ITO film) is formed on one surface side of the substrate may be used. When a substrate in which a conductive layer is formed on one surface side of a glass substrate is used, a larger area and lower cost can be achieved as compared with a case where a semiconductor substrate is used. In the present embodiment, the surface electrode 7 is made of a gold thin film, but may be made of at least two thin film electrode layers stacked in the thickness direction. When it is composed of two thin film electrode layers,
For example, gold is used as the material of the upper thin-film electrode layer,
As a material for the lower thin film electrode layer (the thin film electrode layer on the strong electric field drift layer 6 side), for example, chromium, nickel, platinum, titanium, iridium or the like may be used. In the present embodiment, the strong electric field drift layer 6 is composed of an oxidized porous polycrystalline silicon layer.
Oxidized porous single-crystal silicon or another oxidized porous semiconductor layer.

Hereinafter, the manufacturing method will be described with reference to FIGS.

First, after an ohmic electrode 2 is formed on the back surface of the n-type silicon substrate 1, a non-doped polycrystalline silicon layer 3 as a semiconductor layer having a predetermined thickness (for example, 1.5 μm) is formed on the surface of the n-type silicon substrate 1. Is formed (deposited), a structure as shown in FIG. 1A is obtained. When the conductive substrate is a semiconductor substrate, the polycrystalline silicon layer 3 may be formed by, for example, an LPCVD method or a sputtering method, or an amorphous silicon film is formed by a plasma CVD method and then an annealing process is performed. Crystallization may be performed to form a film. When the conductive substrate is a glass substrate on which a conductive layer is formed, CVD is used.
The polycrystalline silicon layer may be formed by forming an amorphous silicon film on the conductive layer by a method and annealing the film with an excimer laser. Further, the method of forming a polycrystalline silicon layer on the conductive layer is not limited to the CVD method, and for example, a CGS (Continuous Grain Silicate).
on) method or a catalytic CVD method.

After the non-doped polycrystalline silicon layer 3 is formed, an anodic oxidation treatment tank containing an electrolytic solution consisting of a mixture of a 55 wt% aqueous solution of hydrogen fluoride and ethanol in a ratio of about 1: 1 is used. A platinum electrode (not shown) is connected to the negative electrode, n
Type silicon substrate 1 (ohmic electrode 2) as a positive electrode
By performing anodizing treatment under predetermined conditions while irradiating the polycrystalline silicon layer 3 with light, a porous polycrystalline silicon layer 4 is formed, and a structure as shown in FIG. 1B is obtained. Here, in the present embodiment, as the conditions of the anodic oxidation treatment, the light power applied to the surface of the polycrystalline silicon layer 3 is constant and the current density is constant during the anodic oxidation treatment, but these conditions are appropriately changed. (For example, the current density may be changed).

After the above-described anodic oxidation treatment is completed, hydrogen atoms bonded to the outermost surface of the porous polycrystalline silicon layer 4 are desorbed by a heat treatment, and then the porous polycrystalline silicon layer 4 is oxidized by annealing. Thus, the strong electric field drift layer 6 is formed, and the structure shown in FIG. 1C is obtained.
In short, in the present embodiment, the porous polycrystalline silicon layer 4
After hydrogen atoms terminating the silicon atoms of the porous polycrystalline silicon layer 4 when the polycrystalline silicon layer 4 is formed by anodizing treatment are desorbed by the heat treatment, the porous polycrystalline silicon layer 4
Is oxidized by annealing. Here, in the present embodiment, the heat treatment and the annealing for oxidizing the porous polycrystalline silicon layer 4 are continuously performed using one lamp annealing apparatus. That is, the atmosphere in the furnace of the lamp annealing apparatus is replaced with an oxygen atmosphere, and the substrate temperature is changed from room temperature to a predetermined heat treatment temperature (4 in the illustrated example) as shown in FIG.
00 ° C.) to maintain the heat treatment temperature for a predetermined heat treatment time T1 (for example, 5 minutes), and then further raise the substrate temperature to a predetermined annealing temperature (90 in the illustrated example).
After maintaining the annealing temperature at a predetermined annealing time T2 (for example, 1 hour) with the temperature raised to 0 ° C.), the temperature is lowered to room temperature. Here, before the heat treatment, the outermost surface of the porous polycrystalline silicon layer 4 is terminated by hydrogen atoms as shown in FIG. 8, but by performing the heat treatment,
The outermost surface of the polycrystalline silicon layer 4 is in a state where hydrogen atoms have been eliminated as shown in FIG. The heat treatment temperature is 4
The temperature is not limited to 00 ° C., but is preferably a temperature at which desorption of hydrogen atoms occurs and oxidation of the porous polycrystalline silicon layer 4 does not proceed.
It is desirable to set in the temperature range of ° C.

After the strong electric field drift layer 6 is formed, a surface electrode 7 made of a conductive thin film (for example, a gold thin film) is formed on the strong electric field drift layer 6 by, for example, vapor deposition, as shown in FIG. A field emission electron source 10 having the structure shown is obtained. In this embodiment, the thickness of the surface electrode 7 is set to 1
Although the thickness is set to 5 nm, the thickness is not particularly limited, and may be any thickness as long as electrons passing through the strong electric field drift layer 6 can tunnel. In the present embodiment, the conductive thin film to be the surface electrode 7 is formed by vapor deposition.
The method for forming the conductive thin film is not limited to vapor deposition, and for example, a sputtering method may be used.

According to the above-described manufacturing method, after the hydrogen atoms bonded to the surface of the porous polycrystalline silicon layer 4 formed by the anodic oxidation treatment are desorbed by the heat treatment, the porous polycrystalline silicon layer 4 is removed. Since the strong electric field drift layer 6 is formed by oxidizing the layer 4, the amount of hydrogen contained in the strong electric field drift layer 6 is reduced as compared with the case where the porous polycrystalline silicon layer is oxidized immediately after the anodic oxidation treatment. it is possible to, it is possible to form a dense oxide film near the structure or the SiO ₂ structure of SiO _2, less change with time of the electron emission efficiency and dielectric strength high field emission electron source 1
0 can be realized. In addition, the field emission type electron source manufactured by the above-described manufacturing method has a small degree of vacuum dependence of the electron emission characteristic and has a popping property at the time of electron emission, similarly to the conventional field emission type electron source 10 ′ shown in FIG. Electrons can be stably emitted without a phenomenon occurring.

In the above-described manufacturing method, the hydrogen atoms bonded to the outermost surface of the porous polycrystalline silicon layer 4 are desorbed by heat treatment, and then the porous polycrystalline silicon layer 4 is removed.
Is oxidized by annealing at 900 ° C. to form the strong electric field drift layer 6. Instead of oxidizing the porous polycrystalline silicon layer 4 by annealing, an acid (for example, HNO ₃ , H ₂ SO ₄ , Water, etc.), may be oxidized using oxygen plasma, may be oxidized using ozone gas, and the porous polycrystalline silicon layer 4 may be annealed at 900 ° C. It is possible to form the strong electric field drift layer 6 at a lower temperature than in the case where the substrate is oxidized, and the process temperature is reduced, the restriction on the conductive substrate is reduced, and an inexpensive glass substrate or the like can be used. Therefore, it is easy to increase the area and reduce the cost.

(Embodiment) The field emission type electron source 10 was manufactured by the method of manufacturing the field emission type electron source 10 described in the embodiment with reference to FIG. 1 under the following conditions.

The n-type silicon substrate 1 has a resistivity of 0.01 to 0.02 Ωcm and a thickness of 525 μm (10
0) A substrate was used. The polycrystalline silicon layer 3 (see FIG. 1A) is formed by an LPCVD method.
The degree of vacuum was 20 Pa, the substrate temperature was 640 ° C., and the flow rate of the monosilane gas was 600 sccm.

In the anodic oxidation treatment, 55 wt.
% Of an aqueous solution of hydrogen fluoride and ethanol were mixed at approximately 1: 1. Anodization is performed on the polycrystalline silicon layer 3
Of the surface, only the surface area of 10 mm in diameter is in contact with the electrolyte, the other parts are sealed so that they do not come into contact with the electrolyte, the platinum electrode is immersed in the electrolyte, and a polycrystal is formed using a 500 W tungsten lamp. While irradiating the silicon layer 3 with light at a constant light power, a predetermined current was passed using the platinum electrode as a negative electrode and the n-type silicon substrate 1 (ohmic electrode 2) as a positive electrode. Here, the current density was constant at 25 mA / cm ² , and the energizing time was 12 seconds.

The heat treatment and oxidation were performed in an atmosphere of oxygen in the furnace of the lamp annealing apparatus. The conditions of the heat treatment were a substrate temperature of 400 ° C. and a heat treatment time of 5 minutes, and the oxidation conditions were a substrate temperature of 900 ° C. and an annealing time. For 1 hour. Further, as the surface electrode 7, a gold thin film having a thickness of 15 nm was formed by an evaporation method.

The field emission type electron source 10 of this embodiment is introduced into a vacuum chamber (not shown), and a collector electrode 21 (radiation electron collection) is placed at a position facing the surface electrode 7 as shown in FIG. Electrodes), the degree of vacuum in the vacuum chamber is set to 5 × 10 ⁻⁵ Pa, and a DC voltage Vps is applied between the surface electrode 7 (positive electrode) and the ohmic electrode 2 (negative electrode). 100 V between the surface electrode 7
Of the diode current Ips flowing between the surface electrode 7 and the ohmic electrode 2 by applying the DC voltage Vc of
And electrons e ⁻ emitted from the field emission type electron source 10 through the surface electrode 7 (the dashed line in FIG. 4 indicates a radiated electron flow), and the emitted electrons flow between the collector electrode 21 and the surface electrode 7. The current Ie was measured. As a result, it was confirmed that the field emission electron source 10 of the present example has a higher dielectric strength than the conventional field emission electron source 10 ′.

[0040]

According to the first aspect of the present invention, a strong electric field drift layer composed of a conductive substrate, an oxidized porous semiconductor layer formed on one surface side of the conductive substrate, and a strong electric field drift layer formed on the strong electric field drift layer And a surface electrode made of a conductive thin film, and electrons injected from the conductive substrate are drifted through the strong electric field drift layer and emitted through the surface electrode by applying a voltage with the surface electrode being a positive electrode with respect to the conductive substrate. A method for manufacturing a field emission type electron source, comprising: forming a semiconductor layer on a conductive substrate; and anodizing treatment to make at least a part of the semiconductor layer porous. Forming, a step of desorbing hydrogen atoms bonded to the surface of the porous semiconductor layer by a heat treatment, and oxidizing the porous semiconductor layer after desorbing the hydrogen atoms to form a strong electric field drift layer. Forming a surface electrode made of a conductive thin film on the strong electric field drift layer, so that the hydrogen atoms bonded to the surface of the porous semiconductor layer are desorbed by a heat treatment, and the porous semiconductor layer becomes porous. Since the strong electric field drift layer is formed by oxidizing the semiconductor layer, the amount of hydrogen contained in the strong electric field drift layer can be reduced as compared with the case where the porous semiconductor layer is oxidized immediately after the anodic oxidation treatment. At the same time, a dense oxide film can be formed, and there is an effect that a field emission electron source having a small change over time in electron emission efficiency and a high withstand voltage can be realized.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the step of oxidizing the porous semiconductor layer is a step of annealing in an oxygen atmosphere, so that the insulating property is high and the physical properties are stable. There is an effect that an oxide film can be formed.

According to a fourth aspect of the present invention, in the first or second aspect of the present invention, the step of oxidizing the porous semiconductor layer is a step of electrochemically oxidizing with an acid. Thus, the strong electric field drift layer can be formed at a low temperature, and the process temperature becomes low, the restriction on the conductive substrate is reduced, and the effect of increasing the area and the cost is facilitated.

According to a fifth aspect of the present invention, in the first or second aspect of the invention, the step of oxidizing the porous semiconductor layer is a step of oxidizing using an oxygen plasma. It is possible to form a strong electric field drift layer at a low temperature, and there is an effect that the process temperature becomes low, the restriction on the conductive substrate is reduced, and the area and cost can be easily reduced.

According to a sixth aspect of the present invention, in the first or second aspect of the present invention, the step of oxidizing the porous semiconductor layer is a step of oxidizing using a ozone gas.
It is possible to form a strong electric field drift layer at a lower temperature as compared with the invention of the third aspect, and there is an effect that the process temperature is lowered, the restriction on the conductive substrate is reduced, and the area and cost can be easily reduced. .

According to a seventh aspect of the present invention, there is provided a method of manufacturing a semiconductor device according to any one of the first to sixth aspects, wherein the porous semiconductor layer is oxidized immediately after the anodic oxidation treatment to thereby obtain a strong electric field. Compared to a field emission type electron source having a drift layer formed therein, less hydrogen is mixed into the strong electric field drift layer. The effect is that the film is likely to be dense and the withstand voltage is high.

The invention of claim 8 is the invention of claim 7, wherein the porous semiconductor layer, which has the porous polycrystalline silicon layer, the strong electric field drift layer is close to the structure or the SiO ₂ structure of SiO ₂ This has the effect of having an oxide film with high density.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of main processes for describing a manufacturing method of an embodiment.

FIG. 2 is an explanatory diagram of a manufacturing method according to the embodiment.

FIG. 3 is an explanatory diagram of a main part in a manufacturing process of the above.

FIG. 4 is an explanatory diagram of a measurement principle of emitted electrons of the field emission electron source manufactured by the above.

FIG. 5 is an explanatory diagram of a principle of measuring emitted electrons of a conventional field emission electron source.

FIG. 6 is an explanatory diagram of an electron emission mechanism of the field emission electron source of the above.

FIG. 7 is an explanatory diagram of the manufacturing method.

FIG. 8 is an explanatory view of a main part in a manufacturing process of the same.

FIG. 9 is an explanatory view of a main part in a manufacturing process of the above.

[Explanation of symbols]

 REFERENCE SIGNS LIST 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

Claims (8)

[Claims] 1. A conductive substrate, a strong electric field drift layer formed of an oxidized porous semiconductor layer formed on one surface side of the conductive substrate, and a conductive thin film formed on the strong electric field drift layer A field emission type electron source comprising: a surface electrode; and when a voltage is applied with the surface electrode being a positive electrode with respect to the conductive substrate, electrons injected from the conductive substrate drift through the strong electric field drift layer and are emitted through the surface electrode. A method of forming a semiconductor layer on a conductive substrate,
Forming a porous semiconductor layer by making at least a part of the semiconductor layer porous by anodizing treatment;
A step of desorbing hydrogen atoms bonded to the surface of the porous semiconductor layer by heat treatment; a step of forming a strong electric field drift layer by oxidizing the porous semiconductor layer after desorbing the hydrogen atoms; Forming a surface electrode made of a conductive thin film on the electric field drift layer. 2. The method according to claim 1, wherein the heat treatment is performed in a temperature range of 300 ° C. to 700 ° C. 3. The step of oxidizing the porous semiconductor layer,
3. The method according to claim 1, wherein the annealing is performed in an oxygen atmosphere. 4. The step of oxidizing the porous semiconductor layer,
The method according to claim 1 or 2, wherein the method is a step of electrochemically oxidizing with an acid. 5. The step of oxidizing the porous semiconductor layer,
3. The method for manufacturing a field emission type electron source according to claim 1, wherein the method is a step of oxidizing using oxygen plasma. 6. The step of oxidizing the porous semiconductor layer,
3. The method for manufacturing a field emission type electron source according to claim 1, wherein the method is a step of oxidizing using an ozone gas. 7. A field emission type electron source manufactured by the manufacturing method according to claim 1. Description: 8. The field emission type electron source according to claim 7, wherein said porous semiconductor layer comprises a porous polycrystalline silicon layer.