JP3478206B2 - Method for manufacturing field emission electron source - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a field emission electron source.

[0002]

2. Description of the Related Art The inventors of the present invention rapidly oxidize a porous polycrystalline semiconductor layer (for example, a porous polycrystalline silicon layer <porous polysilicon layer>) by a rapid thermal oxidation (RTO) technique. Proposes a field emission electron source in which a strong electric field drift layer, which is interposed between a conductive substrate and a metal thin film (surface electrode) and in which electrons injected from the conductive substrate drift, is formed.

This field emission electron source 10 'is, for example,
As shown in FIG. 3, an 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 main surface side of, and a surface electrode 7 made of a metal thin film is formed on the strong electric field drift layer 6, and the back surface of the n-type silicon substrate 1 is The ohmic electrode 2 is formed.

A field emission type electron source 10 'having the structure shown in FIG.
Then, as shown in FIG. 4, the surface electrode 7 is arranged in a vacuum, and the collector electrode 21 is arranged so as to face the surface electrode 7, and the surface electrode 7 is arranged with respect to the n-type silicon substrate 1 (ohmic electrode 2). Electrons injected from the n-type silicon substrate 1 drift in the strong electric field drift layer 6 by applying the DC voltage Vps as the positive electrode and applying the DC voltage Vc as the positive electrode to the surface electrode 7 with the collector electrode 21. The electrons are emitted through the surface electrode 7 (note that the alternate long and short dash line in FIG. 4 shows 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. put it here,
The current flowing between the surface electrode 7 and the 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. Big (Ie
/ Ips is larger), the higher the electron emission efficiency. In addition,
In this field emission electron source 10 ', the DC voltage Vps applied between the surface electrode 7 and the ohmic electrode 2 is 10 to 20.
Electrons can be emitted even at a low voltage of about V.

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, the strong electric field drift layer 6 is, as shown in FIG. 5, at least a columnar polycrystalline silicon 51 (grain), a thin silicon oxide film 52 formed on the surface of the polycrystalline silicon 51, and the polycrystalline silicon 51. A nanometer-order microcrystalline silicon layer 63 interposed between 51 and a silicon oxide film 64, which is an insulating layer 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 be composed of

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, so that the injected electrons are accelerated by the strong electric field applied to the silicon oxide film 64 and are directed toward the surface between the polycrystalline silicon 51. Since it drifts in the direction of arrow A in FIG. 5 (upward in FIG. 5), 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. The thickness of the surface electrode 7 is set to about 10 nm to 15 nm.

[0007]

By the way, in the above structure, when electrons are accelerated and emitted by the drift due to the electric field applied to the silicon oxide film 64 which is the insulating layer, the efficiency is lowered due to the defect of the silicon oxide film 64. Alternatively, there is a problem that the withstand voltage decreases. On the other hand, when the silicon oxide film 64 is formed by the rapid temperature rising oxidation method (RTO) or the like, many defects are caused in the interface between the microcrystalline silicon layer 63 and the silicon oxide film 64 or in the silicon oxide film due to stress or the like. As a result, the above decrease in efficiency was inevitable.

The present invention has been made in view of the above problems, and an object thereof is to provide a field emission type electron source capable of improving electron emission efficiency and electric withstand voltage. It is to provide a manufacturing method.

[0009]

In order to achieve the above object, the invention of claim 1 provides a conductive substrate and the conductive substrate.
A strong electric field drift layer made of a porous semiconductor layer formed on the surface side of the electric field and a surface electrode formed on the strong electric field drift layer, and the surface electrode is set to a high potential side with respect to the conductive substrate. In the method of manufacturing a field emission electron source in which electrons injected from the conductive substrate by applying a voltage drift in the strong electric field drift layer and are emitted through the surface electrode, a catalytic action is exerted on the strong electric field drift layer. the surface electrode is formed of a material having a, after forming the surface electrodes, high temperature, in an oxygen atmosphere by the catalytic action of the surface electrode oxide film quality improvement process of the insulating layer made of an oxide film of the strong electric field drift layer It is characterized by applying .

According to the invention of claim 2, a conductive substrate,
A strong electric field drift layer formed of a porous semiconductor layer formed on the surface side of the conductive substrate and a surface electrode formed on the strong electric field drift layer are provided, and the surface electrode is higher than the conductive substrate. Electrons injected from the conductive substrate by applying a voltage on the potential side drift in the strong electric field drift layer and are emitted through the surface electrode. a material having a catalytic action on the surface to form the surface electrode, after forming the surface electrodes, the high temperature, the strong electric field drift layer by oxidizing the porous semiconductor layer by the catalytic action of the surface electrode in an oxygen atmosphere And further the strong electric field drift layer
And characterized by applying an oxidation film quality improvement process of the insulating layer in the catalysis of the insulating layer above table surface electrode consisting of a formed oxide film.

A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the insulating layer is formed of a silicon oxide film.

The invention of claim 4 is characterized in that, in any of the inventions of claims 1 to 3, the surface electrode is formed of Pt.

A fifth aspect of the invention is characterized in that, in any one of the first to fourth aspects of the invention, the strong electric field drift layer is formed of a porous polycrystalline silicon layer.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to embodiments.

(Embodiment 1) This embodiment is an embodiment corresponding to the invention of claim 1, and FIG. 1 shows a schematic configuration of a manufacturing process thereof.

The structure of the field emission electron source 10 obtained by the manufacturing method of this embodiment is the same as the field emission electron source 1 described above.
The structure is basically the same as that of 0 ', and n is a conductive substrate.
A strong electric field drift layer 6 made of an oxidized porous polycrystalline silicon layer <porous polysilicon layer> is formed on the main surface side of the shaped silicon substrate 1, and a surface electrode 7 made of a metal thin film is formed on the strong electric field drift layer 6. N-type silicon substrate 1
The ohmic electrode 2 is formed on the back surface of the.

The manufacturing method will be described below with reference to FIG.

First, after the ohmic electrode 2 is formed on the back surface of the n-type silicon substrate 1, the non-doped polycrystalline silicon layer 3 which is 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, the LPCVD method or the sputtering method, or the amorphous silicon may be formed by the plasma CVD method and then annealed to crystallize the film. May be.

After forming the non-doped polycrystalline silicon layer 3, an anodizing treatment tank containing an electrolytic solution made 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,
Porous polycrystalline silicon layer 4 is formed as shown in FIG. 1B by performing anodizing treatment under predetermined conditions while irradiating polycrystalline silicon layer 3 with light.

After the above-mentioned anodic oxidation 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 rapidly removed. The strong electric field drift layer 6 is formed by oxidation by the temperature rising oxidation method (RTO).
The structure shown in (c) is obtained. In short, in this embodiment, after the hydrogen atoms terminating the silicon atoms of the porous polycrystalline silicon layer 4 when the porous polycrystalline silicon layer 4 is formed by the anodic oxidation treatment are desorbed by the above heat treatment, , The porous polycrystalline silicon layer 4 is oxidized by annealing.

As described with reference to FIG. 5, the strong electric field drift layer 6 has at least columnar polycrystalline silicon 51 (grains), a thin silicon oxide film 52 formed on the surface of the polycrystalline silicon 51, and the polycrystalline silicon 51. A nanometer-order microcrystalline silicon layer 63 interposed between the silicon 51 and the microcrystalline silicon layer 6 formed on the surface of the microcrystalline silicon layer 63.
3 is a silicon oxide film 64 which is an insulating layer having a film thickness smaller than the crystal grain size.

Then, a surface electrode 7 made of a material having a catalytic action, for example, a conductive thin film using Pt is formed on the strong electric field drift layer 6 by vapor deposition shown in FIG. 1D, for example.

Although the field emission type electron source is as it is, the defects are still generated in the silicon oxide film 64, but after the surface electrode 7 is formed, the oxide film quality improving process is further performed in a high temperature and oxygen atmosphere ( FIG. 1E). In this case, the temperature at which the catalytic effect of Pt can be exerted is about 200.
Since the temperature is about 0 ° C., the temperature of the oxide film quality improving process is set to about 200 ° C. to match the device forming process.

In this process, oxygen in the atmosphere is decomposed into ions by the catalytic action of Pt forming the surface electrode 7, and the defects of the silicon oxide film 64 are compensated. In particular, since the strong electric field drift layer 6 is porous, a high defect compensation effect can be expected by oxygen ions.

By thus undergoing the oxide film quality improving process, the defect compensation of the silicon oxide film 64 is performed, and as a result, the electron emission efficiency is improved and the electric breakdown voltage is also improved. 10 will be obtained.

As the material of the surface electrode 7, a material having a catalytic action such as alumina or magnesium may be used.

(Embodiment 2) In the first embodiment, after the oxide film is formed, the surface electrode 7 is formed and the oxide film quality improving process is sequentially performed. In this embodiment, the silicon film corresponds to the invention of claim 2. It is characterized in that the oxide film formation and the oxide film quality improvement treatment are performed simultaneously.

That is, in the present embodiment, first, as shown in FIG. 2A, after forming the ohmic electrode 2 on the back surface of the n-type silicon substrate 1, a predetermined film thickness (for example, 1 A non-doped polycrystalline silicon layer 3 which is a semiconductor layer having a thickness of 0.5 μm) is formed (formed), the polycrystalline silicon layer 3 is formed, and then 55 wt% hydrogen fluoride aqueous solution and ethanol are mixed at a ratio of about 1: 1. Using an anodic oxidation treatment tank containing an electrolytic solution composed of the mixed solution, a platinum electrode (not shown) is used as a negative electrode, and an n-type silicon substrate 1 (ohmic electrode 2) is used.
As a positive electrode, the polycrystalline silicon layer 3 is anodized under a predetermined condition while being irradiated with light, whereby the porous polycrystalline silicon layer 4 is formed as shown in FIG. 2 (b). The process so far is the same as that of the first embodiment.

In this embodiment, after the anodic oxidation treatment is completed, the surface electrode 7 is deposited on the outermost surface of the porous polycrystalline silicon layer 4 by using a material having a catalytic action such as Pt, alumina or magnesium by vapor deposition or the like. Formed (Fig. 2
(C))

After the surface electrode 7 is formed, the porous polycrystalline silicon layer 4 is oxidized at a high temperature in an oxygen atmosphere to form the strong electric field drift layer 6, and at the same time, the silicon oxide film 64 of the strong electric field drift layer 6 is formed. Defect 7 on the surface electrode
As in the case of the first embodiment, the defect compensation is performed by the catalytic action of the above material.

That is, in the present embodiment, the oxide film quality improving process can be performed at the same time by the same process as the oxide film formation, so that the process can be simplified, the yield can be improved, and the manufacturing cost can be reduced as compared with the first embodiment.

The manufacturing method and material of the strong electric field drift layer 6 having the surface electrode 7 formed on the surface thereof are not particularly limited to those in the above-mentioned embodiment, and may be obtained by other manufacturing methods and materials.

[0033]

According to the invention of claim 1, a conductive substrate and the conductive substrate are provided.
A strong electric field drift layer made of a porous semiconductor layer formed on the surface side of the conductive substrate and a surface electrode formed on the strong electric field drift layer are provided, and the surface electrode is higher than the conductive substrate. In the method of manufacturing a field emission electron source, electrons injected from the conductive substrate drift on the strong electric field drift layer and are emitted through the surface electrode when a voltage is applied on the strong electric field drift layer. to a material having a catalytic action to form the surface electrode, after forming the surface electrodes, high temperature, oxidation film quality of the insulating layer made of an oxide film in an oxygen atmosphere the strong electric field drift layer by the catalytic action of the surface electrode Since the improvement treatment is performed, oxygen ions generated by the catalytic action of the material of the surface electrode can compensate for defects in the insulating layer made of an oxide film, and as a result, the efficiency of electron emission can be improved. There is an effect of obtaining the field emission electron source gas withstand voltage is improved.

According to a second aspect of the present invention, there is provided a conductive substrate and the conductive substrate.
A strong electric field drift layer of the multi-porous semiconductor layer formed on a surface side of the conductive substrate, and a surface electrode formed on said strong electric field drift layer, said surface electrode against the conductive substrate In the method of manufacturing a field emission electron source, electrons injected from the conductive substrate drift on the strong electric field drift layer and are emitted through the surface electrode by applying a voltage on the high potential side, in the porous semiconductor layer. the surface electrode is formed on the surface of a material having a catalytic action, after forming the surface electrodes, the high temperature, the strength and oxidizing the porous semiconductor layer by the catalytic action of the surface electrode in an oxygen atmosphere field drift Layer, and further to the strong electric field drift layer
Since catalysis of the surface electrodes made of formed oxide film insulating layer subjected to oxidation film quality improvement process of the insulating layer, defects in the insulating layer made of an oxide film by oxygen ions generated by the catalytic action of the surface electrode material The effect that the field emission electron source can be compensated, and as a result, the efficiency of electron emission is improved and the electric breakdown voltage is improved, the process can be simplified, the yield can be improved, and the manufacturing cost can be reduced. There is.

According to the invention of claim 3, in the invention of claim 1 or 2, since the insulating layer is formed of a silicon oxide film, the effect of defect compensation is high.

According to the invention of claim 4, in any one of the inventions of claims 1 to 3, since the surface electrode is formed of Pt, the temperature of the oxide film quality improving treatment can be matched with the device forming process.

According to a fifth aspect of the invention, in any one of the first to fourth aspects of the invention, since the strong electric field drift layer is formed of the porous polycrystalline silicon layer, the defect compensation effect by oxygen ions becomes higher.

[Brief description of drawings]

FIG. 1 is a process explanatory diagram according to a first embodiment of the present invention.

FIG. 2 is a process explanatory diagram according to the second embodiment of the present invention.

FIG. 3 is a schematic sectional view of a basic field emission electron source.

FIG. 4 is an explanatory view of a characteristic principle of the above.

FIG. 5 is an explanatory diagram of an electron emission mechanism of the above.

[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-A-10-326557 (JP, A) JP-A-9-45679 (JP, A) JP-A-9-259795 (JP, A) JP-A-8- 250766 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01J 9/02 H01J 1/30 H01J 31/12

Claims (5)

(57) [Claims] 1. A conductive substrate and a shape on the surface side of the conductive substrate.
A strong electric field drift layer formed of a porous semiconductor layer ,
A surface electrode formed on the strong electric field drift layer,
A field emission electron 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 on the high potential side of the conductive substrate. the method of manufacturing a source, a material having a catalytic action in the strong electric field drift layer to form the surface electrode, the strong electric field after the formation of the surface electrodes, high temperature, in an oxygen atmosphere by the catalytic action of said surface electrode A method of manufacturing a field emission electron source, characterized by performing an oxide film quality improving process on an insulating layer made of an oxide film of a drift layer. 2. A conductive substrate and a shape on the surface side of the conductive substrate.
A strong electric field drift layer formed of a porous semiconductor layer ,
A surface electrode formed on the strong electric field drift layer,
A field emission electron 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 on the high potential side of the conductive substrate. the method of manufacturing a source, a material having a catalytic effect on the surface of the porous semiconductor layer to form the surface electrode, after forming the surface electrodes,
High temperature, above by the catalytic action of the surface electrode in an oxygen atmosphere
Oxidizing the porous semiconductor layer to form the strong electric field drift layer, and further improving the oxide film quality of the insulating layer by the catalytic action of the surface electrode of the insulating layer formed of the oxide film formed on the strong electric field drift layer. A method of manufacturing a field emission electron source, which comprises: 3. The method of manufacturing a field emission electron source according to claim 1, wherein the insulating layer is formed of a silicon oxide film. 4. The method for manufacturing a field emission type electron source according to claim 1, wherein the surface electrode is formed of Pt. 5. The strong electric field drift layer is formed of a porous polycrystalline silicon layer.
5. A method for manufacturing a field emission electron source according to any one of 1.