JP3508651B2 - Field emission type electron source and method of manufacturing the same - Google Patents

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 in which a semiconductor material is used to emit an electron beam by field emission and a method for manufacturing the same.

[0002]

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

However, the Spindt-type electrode has a complicated manufacturing process, and it is difficult to form a large number of triangular pyramid-shaped emitter chips with high precision. For example, when the Spindt-type electrode is applied to a planar light emitting device or a display, the area becomes large. There was a problem that it was difficult. In addition, since the electric field is concentrated on the tip of the emitter tip in the Spindt-type electrode, when the vacuum degree around the tip of the emitter tip is low and residual gas exists, the residual gas becomes positive ions due to the emitted electrons. Since the positive ions are ionized and collide with the tip of the emitter tip, the tip of the emitter tip is damaged (for example, by ion bombardment) and the current density and efficiency of the emitted electrons become unstable, There is a problem that the life of the chip is shortened. Therefore, in the Spindt-type electrode, in order to prevent the occurrence of this kind of problem, high vacuum (about 10 ⁻⁵ Pa
It is necessary to use it at about 10 ⁻⁶ Pa), resulting in a high cost and a troublesome handling.

In order to improve this kind of problem, MIM
(Metal Insulator Metal) method and MOS (Metal Oxid)
A field emission electron source of the e Semiconductor) type has been proposed. The former is a plane-type field emission electron source having a laminated structure of metal-insulating film-metal and the latter metal-oxide film-semiconductor. However, in order to increase the electron emission efficiency (in order to emit many electrons) in this type of field emission electron source, it is necessary to reduce the film thickness of the insulating film and the oxide film. If the thickness of the insulating film or the oxide film is too thin, there is a risk of causing dielectric breakdown when a voltage is applied between the upper and lower electrodes of the laminated structure. There is a problem that the electron emission efficiency (drawing efficiency) cannot be made so high because there is a restriction on thinning of the insulating film and the oxide film.

On the other hand, as a field emission type electron source capable of improving electron emission efficiency, a single crystal semiconductor such as a silicon substrate has recently been disclosed in, for example, Japanese Patent 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. Then, a field emission type electron source (semiconductor cold electron emission device) configured to apply a voltage between a semiconductor substrate and a surface electrode to emit electrons has been proposed.

However, the above-mentioned Japanese Patent Laid-Open No. 8-2507
In the field emission electron source described in Japanese Patent Publication No. 66, a so-called popping phenomenon is likely to occur at the time of electron emission, and unevenness in the amount of emitted electrons is likely to occur. Therefore, when applied to a flat light emitting device, a display device, etc., uneven light emission occurs. There is a problem called.

Therefore, the inventors of the present application filed Japanese Patent Application No. 10-2.
No. 72340 and Japanese Patent Application No. 10-272342,
A porous polycrystalline semiconductor layer (for example, a porous polycrystalline silicon layer) is rapidly thermally oxidized by a rapid thermal oxidation (RTO) technique so as to be interposed between a conductive substrate and a metal thin film (surface electrode). Then, we proposed a field emission electron source with a strong electric field drift layer where electrons injected from a conductive substrate drift. In this field emission 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 which is a conductive substrate. And the 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 so as to face the surface electrode 7, and the DC voltage Vps is applied with the surface electrode 7 as a positive electrode with respect to the n-type silicon substrate 1 (ohmic electrode 2). At the same time, the collector electrode 21 is applied to the surface electrode 7 as a positive electrode and a DC voltage Vc is applied, so that the 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 alternate long and short dash line in FIG. 5 shows the flow of electrons e ⁻ emitted through the surface electrode 7.) Therefore, it is desirable to use a material having a small work function for the surface electrode 7. Here, the current flowing between the surface electrode 7 and the n-type silicon substrate 1 (ohmic electrode 2) is referred to as a diode current Ips, and the current flowing between the collector electrode 21 and the surface electrode 7 is referred to as an emission electron current Ie. As the emitted electron current Ie with respect to the diode current Ips is larger (Ie / Ips is larger), the electron emission efficiency is higher. In this field emission electron source 10 ', electrons can be emitted even if the DC voltage Vps applied between the surface electrode 7 and the ohmic electrode 2 is a low voltage of about 10 to 20V.

In the field emission type electron source 10 ', the vacuum degree dependence of the electron emission characteristic is small, and the popping phenomenon does not occur during electron emission, and electrons can be emitted stably with high electron emission efficiency. Here, as shown in FIG. 6, the strong electric field drift layer 6 ′ includes at least columnar polycrystalline silicon 51 (grains), 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 silicons 51 and a silicon oxide film 64 which is an insulating film formed on the surface of the microcrystalline silicon layer 63 and having a film thickness smaller than the crystal grain size of the microcrystalline silicon layer 63. It is considered to consist of and. That is, in the strong electric field drift layer 6 ′, it is considered that the surface of each grain is made 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 are directed to the surface between the polycrystalline silicon 51. And 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 easily tunnel through the surface electrode 7 and are emitted into a vacuum. Here, the film thickness of the surface electrode 7 is 10 n
It is set to about m to 15 nm.

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

By the way, the above-mentioned field emission type electron source 10 'is used.
Then, the strong electric field drift layer 6 ′ is formed by depositing a non-doped polycrystalline silicon layer on the n-type silicon substrate 1 which is a conductive substrate, and then making the polycrystalline silicon layer porous by anodic oxidation treatment. The converted polycrystal silicon layer (porous polycrystal silicon layer) is heated to, for example, 900 ° C. by a rapid heating method.
It is formed by oxidation at a temperature of. Here, as the electrolytic solution used for the anodizing treatment, a solution obtained by mixing an aqueous solution of hydrogen fluoride and ethanol at a ratio of about 1: 1 is used. Also, in the step of oxidizing by the rapid heating method,
Using a lamp annealing device, the substrate temperature was raised from room temperature to 900 ° C. in dry oxygen as shown in FIG. 7, and then the substrate temperature was maintained at 900 ° C. for 1 hour to oxidize the substrate. Have been lowered to.

[0012]

By the way, the porous polycrystalline silicon layer formed by the anodizing treatment as described above uses a mixed solution of an aqueous solution of hydrogen fluoride and ethanol as an electrolytic solution in the anodizing treatment. Therefore, the outermost surface of the porous polycrystalline silicon layer is terminated by hydrogen atoms as shown in FIG. Therefore, when the porous polycrystalline silicon layer formed by the anodic oxidation treatment is oxidized at 900 ° C. in the temperature profile as shown in FIG. 7, hydrogen atoms remain or Si--OH is left as shown in FIG. However, there is a problem in that a dielectric oxide film having a structure of SiO ₂ is unlikely to be formed and a withstand voltage is lowered. Further, the hydrogen content 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 transferred from the surface of the strong electric field drift layer 6 ′). Desorption) may deteriorate the stability of electron emission efficiency over time.

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

[0014]

In order to achieve the above object, the invention of claim 1 comprises a conductive substrate and an oxidized porous polycrystalline silicon layer formed on one surface side of the conductive substrate. The strong electric field drift layer and the surface electrode made of a conductive thin film formed on the strong electric field drift layer are provided, and the surface electrode is electrically conductive by applying a voltage to the conductive substrate as a positive electrode. a method of manufacturing a field emission electron source electrons injected from sexual substrate is released through the surface electrode drift strong electric field drift layer, a polycrystalline silicon on a conductive substrate
The polycrystal is formed by the process of forming a con layer and anodizing treatment.
Forming a porous polycrystalline silicon layer <br/> including a microcrystalline silicon layer order of nanometers interposed between the columnar grains and grain by porous at least a portion of the silicon layer, porous A step of desorbing hydrogen atoms bonded to the surface of the polycrystalline silicon layer by heat treatment,
After desorbing hydrogen atoms, the porous polycrystalline silicon layer is oxidized to thin the surface of each grain.
Forming a silicon oxide film and forming the microcrystalline silicon
The crystal grain size of the microcrystalline silicon layer on the surface of each layer
And remote forming a silicon oxide film strong electric field drift layer by forming a small thickness, characterized by a step of forming a surface electrode made of a conductive thin film on the strong electric field drift layer, porous Of hydrogen atoms bonded to the surface of porous polycrystalline silicon layer after desorption by heat treatment
Since the strong electric field drift layer to oxidize polysilicon layer is formed, a porous polycrystalline immediately after the anodized
The amount of hydrogen contained in the strong electric field drift layer can be reduced as compared with the case where the recon layer is oxidized, and a dense silicon oxide film is used for each grain and each fine grain.
A field emission electron source that can be formed on the surface of each of the crystalline silicon layers, has a small change in electron emission efficiency over time, and has a high withstand voltage can be realized.

According to a second aspect of the present invention, in the first aspect of the invention, the heat treatment is performed in a temperature range of 300 ° C. to 700 ° C., which is a preferable embodiment.

According to a third aspect of the present invention, in the first or second aspect of the invention, the step of oxidizing the porous polycrystalline silicon layer is a step of annealing in an oxygen atmosphere.
It is possible to form a silicon oxide film having high insulation and stable properties.

The invention according to claim 4 is the invention according to claim 1 or claim 2, wherein the step of oxidizing the porous polycrystalline silicon layer is a step of electrochemically oxidizing with an acid. It becomes possible to form the strong electric field drift layer at a lower temperature than that of the above-mentioned method, the process temperature becomes low, the restriction on the conductive substrate is reduced, and it becomes easy to increase the area and the cost.

According to a fifth aspect of the invention, in the first or second aspect of the invention, the step of oxidizing the porous polycrystalline silicon layer is a step of using oxygen plasma. In comparison, 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 invention, in the first or second aspect of the invention, the step of oxidizing the porous polycrystalline silicon layer is a step of oxidizing with ozone gas.
It becomes possible to form the strong electric field drift layer at a low temperature as compared with the invention of claim 3, the process temperature becomes low, the restriction of the conductive substrate is reduced, and it is easy to increase the area and cost.

The invention of claim 7 is characterized by being manufactured by the manufacturing method according to any one of claims 1 to 6, and the porous polycrystal is formed immediately after the anodizing treatment.
Compared to the field emission type electron source in which the strong electric field drift layer is formed by oxidizing the silicon layer , hydrogen is less mixed into the strong electric field drift layer. There is little decrease in efficiency, and
The conoxide film is likely to be dense and the dielectric strength is high .

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION In this embodiment, a method for manufacturing a field emission electron source 10 having the structure shown in FIG. 4 will be described with reference to FIGS. In this 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 about 0.0) is used.
A (100) substrate of 1 Ωcm to 0.02 Ωcm is used.

The basic structure of the field emission electron source 10 of this embodiment is the same as the conventional structure 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 vacuum and the collector electrode 21 is arranged so as to face the surface electrode 7 as in the conventional structure. 7 is applied to the n-type silicon substrate 1 (ohmic electrode 2) as a positive electrode to apply a DC voltage Vps, and the collector electrode 21 is applied to the surface electrode 7 as a positive electrode to apply a DC voltage Vc. Electrons injected from 1 drift in the strong electric field drift layer 6 and are emitted through the surface electrode 7 (note that the chain line in FIG. 4 indicates the flow of the electrons e ⁻ emitted through the surface electrode 7). Therefore, it is desirable to use a material having a small work function for the surface electrode 7. Here, a current flowing between the surface electrode 7 and the n-type silicon substrate 1 (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 the 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. Also in the field emission electron source 10 of the present embodiment, as in the above-described conventional configuration, electrons are generated even if the DC voltage Vps applied between the surface electrode 7 and the ohmic electrode 2 is a low voltage of about 10 to 20V. Can be released.

In this embodiment, the strong electric field drift layer 6 is
It is characterized by having a dense oxide film in which hydrogen is less mixed as compared with the strong electric field drift layer 6'in the above-mentioned conventional configuration.
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 the structure of SiO ₂ or SiO ₂
It is a dense film with a structure close to that of.

In the field emission type electron source 10 of this embodiment, however, the amount of hydrogen mixed in the strong electric field drift layer 6 is small, and thus the decrease in electron emission efficiency due to the change over time in the distribution of hydrogen is small. Moreover, since the oxide film is denser than in the conventional case, the dielectric strength is high.

In this embodiment, the n-type silicon substrate 1 is used as the conductive substrate, but a metal substrate such as chrome may be used instead of the n-type silicon substrate 1, or an insulating material such as a glass substrate may be used. A substrate having a conductive layer (for example, an ITO film) formed on one surface side thereof 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 the case of using a semiconductor substrate. Further, although the surface electrode 7 is made of the gold thin film in this embodiment, it may be made of at least two thin film electrode layers laminated 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 the material of the lower thin film electrode layer (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 adopted. In this embodiment, the strong electric field drift layer 6 is composed of an oxidized porous polycrystalline silicon layer.
It is conceivable that it is composed of oxidized porous single crystal silicon or other oxidized porous semiconductor layer.
It

The manufacturing method will be described below with reference to FIGS. 1 and 2.

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

After the non-doped polycrystalline silicon layer 3 is formed, an anodizing treatment tank containing an electrolytic solution composed of a mixed solution of 55 wt% hydrogen fluoride aqueous solution and ethanol at a ratio of about 1: 1 is used. Platinum electrode (not shown) is the negative electrode, n
Using the silicon substrate 1 (ohmic electrode 2) as a positive electrode,
By carrying out 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 condition of the anodizing treatment, the optical power with which the surface of the polycrystalline silicon layer 3 is irradiated and the current density are kept constant during the anodizing treatment, but this condition may be changed appropriately. (For example, the current density may be changed).

After the above-mentioned anodizing treatment is completed, 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 annealed. By doing so, the strong electric field drift layer 6 is formed, and the structure shown in FIG. 1C is obtained.
In short, in this embodiment, the porous polycrystalline silicon layer 4 is
The hydrogen atoms terminating the silicon atoms of the porous polycrystalline silicon layer 4 when formed by the anodic oxidation treatment are desorbed by the heat treatment, and then the porous polycrystalline silicon layer 4 is removed.
Are 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 by using one lamp annealing device. That is, the inside of the furnace of the lamp annealing device is replaced with an oxygen atmosphere so that the substrate temperature is from room temperature to a predetermined heat treatment temperature (in the illustrated example, 4).
After the temperature is increased to 00 ° C. and the heat treatment temperature is maintained for a predetermined heat treatment time T1 (for example, 5 minutes), the substrate temperature is further increased to a predetermined annealing temperature (90 in the illustrated example).
The annealing temperature is maintained for a predetermined annealing time T2 (for example, 1 hour) in a state of being raised to 0 ° C.), and then 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 are desorbed as shown in FIG. The heat treatment temperature is 4
The temperature is not limited to 00 ° C., and is preferably a temperature at which desorption of hydrogen atoms occurs and oxidation of the porous polycrystalline silicon layer 4 does not proceed, and is 300 ° C. to 700 ° C.
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. A field emission type 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 the electrons passing through the strong electric field drift layer 6 can tunnel. Further, in the present embodiment, the conductive thin film to be the surface electrode 7 is formed by vapor deposition,
The method of forming the conductive thin film is not limited to vapor deposition, and for example, a sputtering method may be used.

However, according to the above-mentioned manufacturing method, 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, and then the porous polycrystalline silicon 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 smaller than that in the case where the porous polycrystalline silicon layer is oxidized immediately after the anodic oxidation treatment. In addition, the field emission type electron source 10 having a SiO ₂ structure or a dense oxide film close to the SiO ₂ structure can be formed, and the electron emission efficiency is small with time and the withstand voltage is high. be able to. The field emission electron source manufactured by the above-described manufacturing method has a small vacuum degree dependence of electron emission characteristics and pops at the time of electron emission, as in the conventional field emission electron source 10 ′ shown in FIG. Electrons can be emitted stably without any phenomenon.

In the manufacturing method described above, 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.
The strong electric field drift layer 6 is formed by annealing at 900 ° C. for annealing, but instead of oxidizing the porous polycrystalline silicon layer 4 by annealing, an acid (for example, HNO ₃ , H ₂ SO ₄ , It may be electrochemically oxidized with water, etc., may be oxidized with oxygen plasma, or may be oxidized with ozone gas, and the porous polycrystalline silicon layer 4 may be annealed at 900 ° C. It becomes possible to form the strong electric field drift layer 6 at a lower temperature than that in the case of oxidizing by oxidation, the process temperature becomes low, and the restrictions on the conductive substrate are reduced, and an inexpensive glass substrate or the like can be used. Therefore, it is easy to increase the area and reduce the cost.

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

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 the LPCVD method under the following film forming conditions.
The degree of vacuum was 20 Pa, the substrate temperature was 640 ° C., and the flow rate of monosilane gas was 600 sccm.

In the anodizing treatment, the electrolyte solution is 55 wt
% Aqueous solution of hydrogen fluoride and ethanol were used in an approximately 1: 1 mixture. Anodization is performed on the polycrystalline silicon layer 3
Only the area of 10 mm in diameter of the surface is exposed to the electrolytic solution, and the other part is sealed so as not to contact the electrolytic solution, the platinum electrode is dipped in the electrolytic solution, and the polycrystal is formed by using a 500 W tungsten lamp. While irradiating the silicon layer 3 with light having a constant optical 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 energization time was 12 seconds.

The heat treatment and the oxidation are carried out in an oxygen atmosphere in a furnace of a lamp annealing apparatus. The heat treatment conditions are a substrate temperature of 400 ° C. and a heat treatment time of 5 minutes, and the oxidation conditions are a substrate temperature of 900 ° C. and an annealing time. Was one hour. Further, as the surface electrode 7, a gold thin film having a film thickness of 15 nm was formed by vapor deposition.

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

[0039]

According to the invention of claim 1, the conductive substrate and the oxidized porous polycrystalline film formed on one surface side of the conductive substrate.
A strong electric field drift layer made of a recon layer and a surface electrode made of a conductive thin film formed on the strong electric field drift layer are provided, and the surface electrode is made conductive by applying a voltage to the conductive substrate as a positive electrode. a method of manufacturing a field emission electron source electrons injected from the substrate is released through the drift surface electrodes a strong electric field drift layer, the conductive substrate to
By the process of forming a polycrystalline silicon layer and the anodizing process
Porous polycrystalline including a microcrystalline silicon layer order of nanometers interposed between the columnar grains and grain by porous at least a portion of the polycrystalline silicon layer
Forming a silicon layer, a step of desorbing heat treatment a hydrogen atom bonded to the porous polycrystalline silicon layer <br/> surface of the porous polycrystalline silicon hydrogen after desorbed
By oxidizing the con layer ,
A thin silicon oxide film is formed on the surface and
Of the microcrystalline silicon layer on the surface of each crystalline silicon layer
A step of forming a strong electric field drift layer by forming a silicon oxide film having a film thickness smaller than the crystal grain size and a step of forming a surface electrode made of a conductive thin film on the strong electric field drift layer are performed. Since it has a porous structure , it is porous after hydrogen atoms bonded to the surface of the porous polycrystalline silicon layer are desorbed by heat treatment.
Since it is a strong electric field drift layer to oxidize polysilicon layer is formed, a porous polycrystalline immediately after the anodized
The amount of hydrogen contained in the strong electric field drift layer can be reduced as compared with the case where the recon layer is oxidized, and a dense silicon oxide film is used for each grain and each fine grain.
It is possible to form a field emission type electron source that can be formed on the surface of each of the crystalline silicon layers, has a small change in electron emission efficiency with time, and has a high withstand voltage.

According to the invention of claim 3, in the invention of claim 1 or 2, since the step of oxidizing the porous polycrystalline silicon layer is a step of annealing in an oxygen atmosphere,
There is an effect that it is possible to form a silicon oxide film having a high insulating property and being physically stable.

The invention according to claim 4 is the invention according to claim 1 or claim 2, wherein the step of oxidizing the porous polycrystalline silicon layer is a step of electrochemically oxidizing with an acid. It is possible to form the strong electric field drift layer at a lower temperature than that of, and the process temperature becomes lower, so that there are less restrictions on the conductive substrate, and it is easy to increase the area and the cost.

According to a fifth aspect of the invention, in the first or second aspect of the invention, the step of oxidizing the porous polycrystalline silicon layer is performed by using oxygen plasma. In comparison, it is possible to form the strong electric field drift layer at a low temperature, the process temperature becomes low, the restrictions on the conductive substrate are reduced, and it is easy to increase the area and cost.

According to a sixth aspect of the invention, in the first or second aspect of the invention, the step of oxidizing the porous polycrystalline silicon layer is a step of oxidizing using ozone gas.
It is possible to form the strong electric field drift layer at a low temperature as compared with the invention of claim 3, the process temperature becomes low, the restriction of the conductive substrate is reduced, and it is easy to increase the area and cost. effective.

The invention according to claim 7 is manufactured by the manufacturing method according to any one of claims 1 to 6, and the porous polycrystalline silicon layer is oxidized immediately after the anodizing treatment. Compared to the field emission type electron source in which the strong electric field drift layer is formed, hydrogen is less mixed into the strong electric field drift layer, so that the electron emission efficiency is less likely to decrease due to the change over time in the distribution of hydrogen as in the conventional case. In addition, the silicon oxide film is likely to be dense and the dielectric strength is increased .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of main steps for explaining a manufacturing method according to an embodiment.

FIG. 2 is an explanatory diagram of the above manufacturing method.

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

FIG. 4 is an explanatory diagram of a principle of measuring emitted electrons of a field emission electron source manufactured according to 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 view of an electron emission mechanism of the field emission electron source of the above.

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

FIG. 8 is an explanatory diagram of a main part in the above manufacturing process.

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

[Explanation of symbols]

1 n-type silicon substrate 2 Ohmic electrodes 3 Polycrystalline silicon layer 4 Porous polycrystalline silicon layer 6 Strong electric field drift layer 7 Surface electrode 10 Field emission electron source

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 10-326557 (JP, A) JP 11-111670 (JP, A) JP 9-259795 (JP, A) Special table 10- 507576 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 9/02 H01J 1/30 H01J 31/12

Claims (7)

(57) [Claims] 1. A strong electric field drift layer comprising a conductive substrate, an oxidized porous polycrystalline silicon 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 device in which electrons injected from the conductive substrate drift in the strong electric field drift layer and are emitted through the surface electrode by applying a voltage with the surface electrode as a positive electrode with respect to the conductive substrate. a method of manufacturing an electron source, a step of forming a polycrystalline silicon layer on a conductive substrate, the polycrystalline silicon at anodization
Columnar grayed by porous at least a portion of the layer
Fine- grained nanometer order between the rain and grain
Forming a porous polycrystalline silicon layer containing a crystal silicon layer, a step of desorbing heat treatment a hydrogen atom bonded to the surface of the porous polycrystalline silicon layer, a hydrogen atom After desorbed By oxidizing the porous polycrystalline silicon layer , thin silicon is formed on the surface of each grain.
Forming an oxide film and forming each of the microcrystalline silicon layers
Smaller than the crystal grain size of the microcrystalline silicon layer on the surface
Of a strong electric field drift layer by forming a silicon oxide film having a uniform thickness, and a step of forming a surface electrode made of a conductive thin film on the strong electric field drift layer. Method of manufacturing electron source. 2. The method of manufacturing a field emission electron source according to claim 1, wherein the heat treatment is performed in a temperature range of 300 ° C. to 700 ° C. 3. The method of manufacturing a field emission electron source according to claim 1, wherein the step of oxidizing the porous polycrystalline silicon layer is a step of annealing in an oxygen atmosphere. 4. The method of manufacturing a field emission electron source according to claim 1, wherein the step of oxidizing the porous polycrystalline silicon layer is a step of electrochemically oxidizing with an acid. Method. 5. The method of manufacturing a field emission electron source according to claim 1, wherein the step of oxidizing the porous polycrystalline silicon layer is a step of oxidizing using a plasma of oxygen. . 6. The method of manufacturing a field emission electron source according to claim 1, wherein the step of oxidizing the porous polycrystalline silicon layer is a step of oxidizing using an ozone gas. 7. A field emission electron source manufactured by the manufacturing method according to any one of claims 1 to 6 .