JPH07335116A - Electron emission device - Google Patents

Abstract

PURPOSE:To provide an electron emission device capable of emitting electrons with high intensity and uniformity by forming an electron emission cathode of a conductor region in the gap of fine skeletons formed on the main surface of a semiconductor board. CONSTITUTION:A silicon nitride film 2 is formed on one main surface of a silicon board 1, and an aluminium electrode 3 is deposited on the other main surface. The silicon board other than a part for forming an electron emission cathode is covered with an acid resistant protection film, and anodically formed in a hydrofluoric acid family etching solution to form silicon fine skeletons 4. Porous silicon obtained has the three dimensionally extended silicon fine skeletons 4, and gaps 5 exist between them. Anodic oxidation is conducted in a non-etching electrolyte solution by using silicon as an anode to form an anode oxide film 6 on the surface of the silicon fine skeleton 4. By using nickel for a conductor, a conductor region 7 is formed in the gap 5. Nickel electrodes 8 serving as electrodes in the conductor region 7 are arranged at both ends of a device by utilizing continuity in the lateral direction of the conductor region 7 to complete an electron emission device.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electron-emitting device.

[0002]

2. Description of the Related Art In recent years, electron-emitting devices used as electron-emitting sources have been applied to ultra-high-speed microwave devices, electron beam devices, flat-panel image display devices and the like.
Conventionally, hot cathode type electron-emitting devices have been widely used as electron emission sources, but electron-emitting devices using hot cathodes require large pre-ionization due to large energy loss due to heating, and also the cathode tip due to overheating. There were problems such as severe wear and pollution and short life.

A cold cathode type is known as a conventional electron-emitting device which has been drawing attention to solve these problems. Among them, an electric field for locally generating a high electric field to perform field emission is known. In recent years, active electron emission devices have been actively researched.

As an example of this field effect type electron-emitting device, the one shown in Japanese Unexamined Patent Publication No. 5-211030 is shown in the sectional view of FIG. First, aluminum (Al) is anodized to open the pores 61. At this time, the pores 61 grow in a direction horizontal to the direction in which the electric field is applied, that is, in the vertical direction of the paper surface. Further, Al is anodized at the same time when anodization is performed to form an alumina (Al ₂ O ₃ ) layer 62. After that, a part of the pores 61 is filled with the electron emission cathode 63, and Al
_A conductive portion 64 is formed on one surface of the ₂ O ₃ layer 62 to bond the plurality of electron emission cathodes 63.

With such a structure, the shape of the cathode is changed to Al.
Since it can be determined by the shape of the pores 61 formed in the ₂ O ₃ layer 62, the variation in the shape of the tip of the cathode is reduced and a highly reliable electron-emitting device can be obtained.

However, this electron-emitting device has the following problems. First, in the anodic oxide film of Al, the pores 61 grow in the direction horizontal to the direction in which the electric field is applied, and there is almost no branching or lateral growth. Therefore, when the electron emitting cathode 63 is filled in the pores, a substantially vertical columnar structure is formed. On the other hand, the unfilled pores 61 remain as cavities that are long in the vertical direction, so that the strength of the device is weakened, which is sufficient. Durability cannot be obtained.

Further, since the electron-emitting cathodes 63 are arranged independently in a column shape long in the vertical direction and are connected by a conductive portion, the diameters of the pores 61 themselves are different, so that the electron-emitting cathodes filled therein are filled. No. 63 has a non-uniform diameter, and the resistance value also changes, so the uniformity of the current flowing through each wire is not very high. Therefore, electrons cannot be emitted due to uniform electric field concentration.

[0008]

As described above, the conventional electron-emitting device has the problems that the device is weak in strength and that it cannot emit electrons due to uniform electric field concentration.
An object of the present invention is to solve the above problems and to provide an electron-emitting device having high strength and capable of uniform electron emission.

[0009]

In order to solve the above problems, the present invention provides a first aspect of the present invention, wherein a fine skeleton formed on a main surface of a semiconductor substrate and a conductor filled in a gap between the fine skeletons. Provided is an electron-emitting device having an area electron-emitting cathode.

According to a second aspect of the present invention, there is provided an electron emission control gate of a fine skeleton formed on the main surface of the semiconductor substrate, and an electron emission cathode of a conductor region filled in the gap of the fine skeleton. An electron-emitting device is provided.

Further, the present invention provides, as the invention of claim 3, an electron emitting cathode having a fine skeleton formed on the main surface of the semiconductor substrate, and a conductor region filled in a gap of the fine skeleton. Provided is an electron emitting device.

According to a fourth aspect of the present invention, there is provided an electron emission cathode having a fine skeleton formed on the main surface of the semiconductor substrate, and an electron emission control gate for the conductor region filled in the gap of the fine skeleton. An electron-emitting device is provided.

Further, the present invention provides, as a seventh aspect of the invention, an electron-emitting device comprising an electron-emitting cathode of a fine skeleton formed on the main surface of a semiconductor substrate and covered with a conductor layer.

Here, the semiconductor substrate means a substrate in which the semiconductor is exposed on the surface, and includes not only a substrate using the semiconductor itself but also a substrate having a semiconductor layer formed on the surface of an insulating material.

The fine skeleton is formed by subjecting a semiconductor substrate to anodization or the like, and refers to a structure in which fine line-shaped skeletons are three-dimensionally connected, such as coral and loofah. It is different from the state in which columns are parallel to each other and hardly connected.

The shape of such a fine skeleton varies depending on the impurity concentration of the semiconductor substrate used. When the impurity concentration is high, the thin wires are close to a columnar parallel structure, and as the impurity concentration is low, the structure becomes a three-dimensional structure farther from the columnar structure. Further, even when the impurity concentration of the semiconductor substrate is high, if the light is irradiated or the current flowing in the anodization step is increased, the structure has a fine skeleton similar to that when the impurity concentration is low.

Filling the gaps of the fine skeleton with the conductor regions includes not only forming the conductor regions in all the gaps of the fine skeleton but also forming the conductor regions in a part of the gaps. For example, there is a case where a conductor region is formed in the middle of the gap and is not above the gap, or a case where the conductor region is lost in a part of the gap and pores are formed in the conductor region.

Here, as a material that can be used for the conductor region or the conductor layer, a material such as gold (Au) or platinum (Pt) whose surface is resistant to oxidative deterioration and is stable,
Materials with excellent electrical conductivity such as silver (Ag), and materials with high strength and mechanical stability such as diamond (C) and silicon carbide (SiC), cermet, etc. As described above, there are materials having a high melting point and excellent heat resistance. Further, not limited to the above materials, any material having a low work function and a high electron emission efficiency can be used.

Further, in the inventions of claims 1 to 4, the main surface of the semiconductor substrate having a fine skeleton may be anodized to form an anodized film. In both cases where the anodic oxide film is formed and not formed, the conductor region is used as an electron emission cathode in the invention of claim 1, the conductor region is used as an electron emission cathode in the invention of claim 2, and the fine skeleton is used as an electron emission control gate. be able to. On the contrary, in the invention of claim 3, the fine skeleton can be used as an electron emission cathode, in the invention of claim 4 the fine skeleton can be used as an electron emission cathode, and the conductor region can be used as an electron emission control gate. Therefore, in the inventions of claims 2 and 4, it is not necessary to separately provide a field emission control gate.

When the conductor region is used as an electron emission cathode, it is possible to perform better electron emission by etching the formed anodic oxide film to expose the conductor region.

Further, in the invention of claim 1, after forming the conductor region, the upper part of the fine skeleton may be etched to expose the side surface of the conductor region. In this case, the anodic oxide film is not formed.

Further, in the invention of claim 7, the fine skeleton having the conductor layer formed on the surface thereof is used as the electron emission cathode. In this case, an anodic oxide film may be formed between the surface of the fine skeleton and the conductor layer. Since the tip of the electron emission cathode is exposed, good electron emission can be performed.

In the first to fourth aspects of the invention, the conductor regions are filled in the gaps of the fine skeleton, and in the seventh aspect of the invention, the conductor layer is coated on the main surface of the semiconductor substrate having the fine skeleton. This can be changed by the time it takes to form the conductor. Longer times will only fill, shorter times will only cover.

This difference also depends on the current when anodizing is performed when forming the anodized film. When the current is large, the thickness of the anodic oxide film formed on the bottom of the fine skeleton becomes thicker than the thickness of the anodic oxide film formed on other parts of the fine skeleton, and the conductors are sequentially filled from the bottom of the fine skeleton. It will be easier. On the other hand, when the current is small, the thickness of the formed anodic oxide film is uniform, and the conductor is easily formed uniformly. However, even if the current is small, if the time for forming the conductor is long, the conductor is filled in the gaps of the fine skeleton.

[0025]

According to the first to fourth aspects of the present invention, the fine skeleton formed on the main surface of the semiconductor substrate has a structure in which the fine skeletons are three-dimensionally connected, and electrons can freely move in the lateral direction. Since either the fine skeleton or the conductor region filled in the gap of the fine skeleton is used as the electron emission cathode, the strength is higher than that of the conventional electron emission device in which the electron emission cathodes are arranged in a columnar shape, and The electron emission becomes uniform.

According to the invention of claim 7, a conductor layer is formed on the main surface of a semiconductor substrate having a fine skeleton, and the fine skeleton is used as an electron emission cathode. In this case as well, as in the first to fourth aspects of the invention, the strength is higher than that of the conventional electron-emitting device, and uniform electron emission can be performed.

[0027]

EXAMPLES Examples of the present invention will be described below. (Embodiment 1) FIG. 1 shows a schematic sectional view of a manufacturing process of an electron-emitting device according to this embodiment. This electron-emitting device uses a fine skeleton as an electron emission control gate and a conductor region as an electron emission cathode. Hereinafter, description will be given with reference to FIG.

First, as a semiconductor substrate, silicon (S) having a plane having a (100) orientation, p-type and a volume resistivity of 10 Ωcm (S
i) A silicon nitride film 2 is formed on one main surface of the substrate 1. After patterning a portion of the silicon nitride film 2 corresponding to a portion forming the electron emission cathode of the Si substrate 1, an Al electrode 3 having a thickness of 300 nm is formed by vapor deposition on the main surface opposite to the surface on which the silicon nitride film 2 is formed. 470 ° C. in a mixed atmosphere of nitrogen and hydrogen for further ohmic contact, 2
Sintering was performed for 0 minutes.

Then, the Si substrate 1 is covered with an acid-resistant protective film (not shown) while leaving a portion for forming an electron emission cathode, and anodization is performed in a hydrofluoric acid-based etching solution to obtain an average height of 1
A Si fine skeleton 4 of 0 μm was formed. As the etching solution, a mixed solution of 49% hydrofluoric acid: ethanol = 2: 3 was used. The anodization was performed at a current density of 1 mA / cm ² while irradiating an incandescent lamp from a very short distance. The formation time was 5 minutes. The porous Si obtained in this way is 3
The Si fine skeleton 4 extends dimensionally, and a gap 5 exists between them. The gaps that exist above and below are connected in the depth direction of the paper. (Fig. 1
(A)).

Subsequently, in a non-etching electrolytic solution, Si
Was used as an anode to carry out anodization to form an anodized film 6 on the surface of the Si fine skeleton 4. The current density at this time is 1 mA /
cm ² and the voltage was suppressed to 20 V or less from the time when the oxidation was started. This is to prevent the Si fine skeleton 4 from being electrically insulated from the substrate when it is oxidized to an excessive voltage. It is considered that the reason why the Si fine skeleton 4 is electrically insulated from the substrate is that the root of the Si fine skeleton 4 is more preferentially oxidized than other portions when the voltage is increased, and becomes electrically insulated (Fig. 1 (b)).

Next, using nickel (Ni) as a conductor,
The conductor region 7 is formed in the gap 5. An electrolytic plating method was used for formation. The conditions were as follows. Nickel sulfate (Ni
SO ₄ ) + nickel chloride (NiCl ₂ ) + boric acid was used as an acidic nickel plating solution, and the current density during plating was 1 with respect to the surface area of the Si substrate 1 before anodization.
It is set to 0 mA / cm ² . The plating solution is heated to 50 ° C., stirred, and irradiated with light without fail. The time was 1 minute (FIG. 1 (c)).

The conductor region 7 in the gap 5 thus obtained has an end face of extremely high-density thin wire, and the cross-sectional area of this thin wire is extremely thin, on the order of several nm to several hundred nm. After that, in order to further increase the efficiency of electron emission, the anodic oxide film 6 between the Si fine skeleton 4 and the conductor region 7 is treated with a mixed solution of ammonium fluoride (NH ₄ F) / hydrogen fluoride (HF). Is selectively used to etch back so that the upper portion of the conductor region 7 does not come into contact with the anodic oxide film 6.

Finally, the Ni electrode 8 is provided as the electrode of the conductor region 7 at both ends of the device by utilizing the fact that the conductor region 7 is connected in the lateral direction. It is completed (Fig. 1 (d)).

In this electron-emitting device, the Si fine skeleton 4 is used as an electron emission control gate and the conductor region 7 is used as an electron emission cathode. Al electrode 3 is used as the electrode of the electron emission control gate.
Can be used.

When this electron-emitting device is used for the cathode, the cathode is three-dimensionally connected and there is lateral communication as compared with the conventional electron-emitting device, so that the strength is increased and the electron emission for each cathode is increased. Becomes uniform.

In the case of this embodiment using p-type Si, a current flows between the cathode and the gate in the range in which the gate potential on the Si substrate side with respect to the cathode is set from zero to minus. Instead, only the electric field was applied. By changing the applied voltage at this time, it is possible to control the emission current to the anode arranged at a position opposed to the cathode.

The current density during anodization is 1 to 10
It is preferably in the range of 0 mA / cm ² . This is because the porosity of Si increases as the current density increases, so that if the current density is less than 1 mA, Si is hardly anodized, and if it is more than 100 mA, most of the Si is anodized and the fine skeleton hardly remains. Further, the formation time is preferably 10 seconds to 10 minutes. This is because the depth of the fine skeleton becomes deeper as the current density becomes higher, and the depth of the fine skeleton becomes too shallow when the time is shorter than 10 seconds and becomes too deep when the time is longer than 10 minutes. is there.

The current density during anodic oxidation is 10 mA / c.
It is preferably m ² or less. This is because if the current density is too high, the rate of formation of the anodic oxide film becomes too fast, making it difficult to control, and the oxide film is preferentially formed on the upper part of the fine skeleton, making it difficult to obtain a uniform film thickness. is there.

The current density when plating is 10 mA /
It is desirable that it is not more than cm ² . This is because if the current density is too high, the formation speed of the conductor region becomes too fast, which makes control difficult, and the conductor region is preferentially formed on the upper part of the fine skeleton, so that the conductor may reach the lower part of the fine skeleton. Because there is no. The plating time is preferably 30 seconds or longer. This is because if it is shorter than 30 seconds, the entire conductor gap is not filled in the gaps of the fine skeleton.

As a method of filling this conductor region, electroless plating can be used. In this case, for example, sodium hypochlorite (NaClO) + sodium acetate (CH ₃ COONa) + nickel sulfate (N
An aqueous solution of iSO ₄ ) can be kept at 90 ° C., and the substrate can be dipped in this for nickel plating. Furthermore, in addition to the above methods, any method may be used as long as it is a method of filling a liquid or a gas into micropores or gaps which cannot be entered by a means for forming a normal thin film, and forming a conductor material to be a conductor region by a subsequent reaction. Can be used without limitation. Specifically, there are an electrolytic polymerization method, an organic metal thermal decomposition method, an impregnation method, a pressure method, a CVD method and the like.

Further, as the conductor region, in addition to Ni, a metal or a low resistance semiconductor such as Au, Pt, indium (In), palladium (Pd), Ag, copper (Cu),
Tin oxide (SnO _2), tantalum oxide (TaO _5), indium oxide _{(InO 3), SiC, SnO} 2 were added niobium (Nb), indium phosphide (InP), gallium arsenide (GaAs), gallium nitride ( GaN), Ga
AlAs or the like can be used. Also, an alloy of metals among these may be used.

In addition to Al, Au, AuGe, gold (Au) / titanium (Ti), A is used as the electrode formed on the back surface.
It is also possible to use u / Cr, aluminum silicide (AlSi), or the like. (Embodiment 2) This electron-emitting device has substantially the same structure as the electron-emitting device of Embodiment 1. The different point is that the fine skeleton is used as an electron emission cathode and the conductor region is used as an electron emission control gate.

Similar to the electron-emitting device of the first embodiment, this electron-emitting device is stronger than the conventional electron-emitting device, and the electron emission is uniform for each cathode. (Embodiment 3) FIG. 2 shows a schematic sectional view of a manufacturing process of an electron-emitting device according to this embodiment. In the following embodiments, the numbers in the figure are the same as those in FIG. 1, and the detailed description is omitted. In this electron-emitting device, the conductor region is exposed by etching the upper portion of the fine skeleton without forming an anodic oxide film, and the conductor region is used as an electron emission cathode, but the fine skeleton is not used as an electron emission control gate. The point is different from the electron-emitting device of the first embodiment. Hereinafter, description will be given with reference to FIG.

First, Example 1 was used except that a Si substrate 1 having a surface having a (100) orientation, an n-type, and a volume resistivity of 0.1 Ωcm was used as a semiconductor substrate, and a silicon nitride film was not formed.
Anodization was performed in the same manner as in FIG. 1A to form the Si fine skeleton 4 (FIG. 2A).

Next, as shown in FIG. 1 of Example 1 except that light is not irradiated.
Similarly to (c), the conductor region 7 was filled in the gap 5 by the electrolytic plating method. Note that light irradiation may be performed (Fig. 2
(B)).

Finally, from the surface of the Si fine skeleton 4 300 n
Only Si was selectively etched and removed to a thickness of about m. As an etching solution, hydrazine: water = 1:
Etching was performed by using the mixed solution of No. 1 and raising the temperature to 70 ° C. in a nitrogen atmosphere. As a result, the conductor region 7 is projected (FIG. 2C).

In this way, the electron-emitting device according to this example is completed. In the case of this electron-emitting device, the conductor region 7 is used as an electron-emitting cathode. Next, FIG. 3 shows an example in which a field emission control gate is formed in addition to the cathode. The same parts as those in FIG. 2 have the same numbers.

Si of (100) plane, n-type, 0.1 Ωcm
After the Si oxide film 31 is formed on the substrate 1 by the CVD method, 3 is formed on the main surface opposite to the surface on which the Si oxide film 31 is formed.
An Al electrode 3 having a thickness of 00 nm is formed by vapor deposition, and 470 is formed in a mixed atmosphere of nitrogen and hydrogen for ohmic contact.
Sintering was performed at 20 ° C. for 20 minutes.

Next, an electrode layer 32 of Ni serving as a field emission control gate is formed on the Si oxide film 31 by magnetron sputtering. The electrode layer 32 and the Si oxide film 31 above the portion forming the electron emission cathode are both patterned and removed. After this, except for the portion where the electron emission cathode is formed, it is covered with an acid resistant tape to perform anodization in the same manner as in FIG. 2A, and thereafter, as shown in FIGS. 2B to 2C. An electron-emitting device is completed in the same process. At this time, the substrate 1 and the Al electrode 3 function as electrodes for supplying electrons to the cathode.

Similar to the electron-emitting device of the first embodiment, this electron-emitting device has high strength and uniform electron emission for each cathode. The current density during anodization is 1 to 50 m.
It is preferably in the range of A / cm ² . This is 1mA
If it is smaller, Si is hardly anodized and 50 mA
If it is larger, the volume that is anodized is large, so
This is because the volume of the filled conductor region used as the electron emission cathode becomes large and the structure becomes unsuitable for the electron emission cathode which requires a fine structure. The formation time is preferably 10 seconds to 10 minutes for the same reason as in Example 1.

The conditions at the time of anodic oxidation / plating are as in Example 1.
The same as (Embodiment 4) FIG. 4 shows a schematic sectional view of a manufacturing process of an electron-emitting device according to this embodiment. This electron-emitting device differs from the electron-emitting device of Example 2 in that the surface of the fine skeleton is covered with a conductor layer without forming an anodic oxide film. Here, the fine skeleton covering the conductor layer is used as an electron-emitting device.
Hereinafter, description will be given with reference to FIG.

First, anodization was performed in the same manner as in FIG. 2A of Example 2 to form the Si fine skeleton 4 on the Si substrate 1 (FIG. 4A). Next, the surface of the Si fine skeleton 4 was coated with the conductor layer 41 by using the electrolytic plating method as in FIG. However, the time was set to 30 seconds (FIG. 4 (b)).

In this way, the electron-emitting device according to this example is completed. Next, FIG. 5 shows an example in which a field emission control gate is formed. (100) surface, n-type, 0.1 Ωcm Si
After the Si oxide film 31 is formed on the substrate 1 by the CVD method, 3 is formed on the main surface opposite to the surface on which the Si oxide film 31 is formed.
An Al electrode 3 having a thickness of 00 nm is formed by vapor deposition, and 470 is formed in a mixed atmosphere of nitrogen and hydrogen for ohmic contact.
Sintering was performed at 20 ° C. for 20 minutes.

Next, an electrode layer 32 of Ni, which serves as a field emission control gate, is formed on the Si oxide film 31 by magnetron sputtering. The electrode layer 32 and the Si oxide film 31 above the portion forming the electron emission cathode are both patterned and removed. Thereafter, except for the portion where the electron emission cathode is formed, it is covered with an acid resistant tape to perform anodization in the same manner as in FIG. 3A, and thereafter, the same steps as shown in FIG. 3B are performed. The electron-emitting device is completed. In the figure, the surface of the Si fine skeleton 4 is covered with a conductive layer.

Similar to the electron-emitting device of the first embodiment, this electron-emitting device has a higher strength and the electron emission is uniform for each cathode. The conditions for the anodization and anodic oxidation may be the same as in Example 1.

The current density during plating is preferably 0.1 to 10 mA / cm ² for the same reason as in Example 1. The plating time is preferably 1 to 30 seconds. This is because if it is shorter than 1 second, the conductor layer is hardly covered, and if it is longer than 30 seconds, the conductor is filled in the entire gap of the fine skeleton.

[0057]

As described above, according to the present invention, it is possible to provide an electron-emitting device having high strength and capable of uniform electron emission.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a manufacturing process of an electron-emitting device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the manufacturing process of the electron-emitting device according to the second embodiment of the present invention.

FIG. 3 is a sectional view of a manufacturing process of the electron-emitting device according to the second embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view of the manufacturing process of the electron-emitting device according to the third embodiment of the present invention.

FIG. 5 is a sectional view of a manufacturing process of the electron-emitting device according to the third embodiment of the present invention.

FIG. 6 is a sectional view of a conventional electron-emitting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Si substrate 3 ... Al electrode 4 ... Si fine skeleton 5 ... Gap 6 ... Anodized film 7 ... Conductor area 31 ... Si oxide film 32 ... Electrode layer 41 ... Conductor layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Tanamoto 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center (72) Inventor Masayuki Nakamoto Small, Kawasaki-shi, Kanagawa Muko Toshiba Town No. 1 Inside Toshiba Research and Development Center, a stock company

Claims (7)

[Claims] 1. An electron-emitting device comprising: a fine skeleton formed on a main surface of a semiconductor substrate; and an electron-emitting cathode in a conductor region filled in a gap of the fine skeleton. 2. An electron comprising an electron emission control gate of a fine skeleton formed on a main surface of a semiconductor substrate and an electron emission cathode of a conductor region filled in a gap of the fine skeleton. Emissive element. 3. An electron emitting device comprising an electron emitting cathode having a fine skeleton formed on a main surface of a semiconductor substrate, and a conductor region filled in a gap of the fine skeleton. 4. An electron comprising an electron emission cathode having a fine skeleton formed on a main surface of a semiconductor substrate, and an electron emission control gate of a conductor region filled in a gap of the fine skeleton. Emissive element. 5. The electron-emitting device according to claim 1, wherein an insulating separator of an anodic oxide film is formed between the fine skeleton and the conductor region. 6. The side surface of the conductor region is exposed by etching the fine skeleton.
Alternatively, the electron-emitting device according to item 2. 7. An electron-emitting device comprising an electron-emitting cathode of a fine skeleton formed on the main surface of a semiconductor substrate and covered with a conductor layer.