JPH08148080A - Array-shaped field emission cold cathode and manufacture thereof - Google Patents

Abstract

PURPOSE: To improve a reliable life of a cathode by preventing decreasing of insulating resistance and dielectric strength due to contamination by dirt, dust or the like received during a process of manufacturing an array-shaped field emission cold cathode and an electronic device equipped with this cathode. CONSTITUTION: Layers of insulating layer 2 and gate electrode 3 are deposited through a cathode of forming an emitter 5 by a film deposition method in a gate opening and through a mask formed on the emitter 5 formed by etching a substrate 1. In this cathode, a common insulating film 6 is formed in at least a lower part of the emitter 5 and a side surface part of the insulating layer 2. In order to form this insulating film 6, a pressure reducing CVD method or SOG technique is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold cathode serving as an electron emission source, and more particularly to an array-type field emission cold cathode which emits electrons from an array of sharp tips.

[0002]

2. Description of the Related Art A cold condensing cathode is formed by arranging a minute conical emitter and a micro cold cathode formed in the immediate vicinity of the emitter and having a function of drawing a current from the emitter and a current control function. The cathode is C.I. A. Spi
proposed by Ndt et al. (Journal o
f Applied Physics, Vol. 39,
No. 7, pp. 3504, 1968). This Spindt type cold cathode has advantages that a higher current density can be obtained and the velocity dispersion of emitted electrons is smaller than that of a hot cathode. In addition, the current noise is smaller than that of a single field emission emitter, and it operates at a low voltage of several tens to 200 V,
It is said to work even in an environment with a relatively poor vacuum degree.

FIG. 5 (a) shows a sectional view of the structure of a Spindt-type cold cathode main part which is the prior art disclosed in the above document. An insulating layer 102 and a gate electrode 103 are deposited on a substrate 101. Insulating layer 102 and gate electrode 1
03 has a cavity 104 formed therein. In the cavity 104, a minute conical emitter 105 having a height of about 1 μm is formed by a film deposition method.

The substrate 101 and the emitter 105 are electrically connected, and a voltage of about 100 V is applied between the emitter 105 and the gate electrode 103. The thickness of the insulating layer 102 is about 1 μm, and the opening diameter of the gate electrode 103 is also about 1 μm.
Since the tip of the emitter 105 is extremely sharp, about 10 nm, a strong electric field is applied to the tip of the emitter 105. When this electric field becomes 2-5 × 10 ⁷ V / cm or more, electrons are emitted from the tip of the emitter 105. Reference numeral 106 denotes equipotential lines in the cavity 104 of the micro cold cathode, and reference numeral 107 denotes an electron beam trajectory of emitted electrons.

A micro cold cathode having such a structure is mounted on a substrate 101.
A planar cathode that emits a large current is formed by arranging the cathodes in an array. In addition, a cold cathode that forms an emitter by etching a substrate is proposed by Gray and is called a Gray type. This Gray type cathode is shown in FIG.

In such a cathode, since a high electric field is applied between the emitter 105 and the gate electrode 103, dust and the like are deposited on the insulating layer during the manufacturing process of the cathode or the manufacturing process of an electronic device such as an electron tube on which the cathode is mounted. In this case, the insulation resistance between the emitter 105 and the gate electrode 103 may be reduced to cause leakage current, or the withstand voltage may be reduced to cause a discharge, thereby destroying the gate electrode 103 or the emitter 105. .

FIG. 6 shows a prior art disclosed in Japanese Patent Application Laid-Open No. 6-52788. 6, an emitter 109 made of the same silicon material is formed on a silicon substrate 108, and an insulating layer 110 is laminated on the silicon substrate 108 except for the tip of the emitter 109. An insulating layer 111 and a gate electrode 112 are formed thereon. The material of the auxiliary insulating layer 111, which is superior in corrosion resistance to the etching material used in the etching process for exposing the tip of the emitter 109 and is hard to be etched, is used. Therefore, the emitter 109
Thus, a step is formed between the insulating layer 110 and the auxiliary insulating layer 111. As a result, the gate electrode 112 and the emitter 10
9 is increased, and the lower portion of the gate electrode 112 is protected by the insulating layer, so that the dielectric strength is improved.

Japanese Patent Application Laid-Open No. HEI 6-176686 discloses an embodiment in which the lower portion of the emitter is covered with an insulating layer separating the gate electrode and the emitter, similarly to FIG.

FIG. 7 shows a conventional technique disclosed in Japanese Patent Laid-Open No. 6-131968. In FIG. 7, a coating film made of a hard carbon film or a carbide layer is formed on the surface of the emitter 105. Therefore, the atmospheric gas is hardly adsorbed to the emitter 105, and stable electron emission characteristics can be obtained.

FIG. 8 shows a structure of a conventional cold cathode disclosed in US Pat. No. 4,940,916. In FIG. 8, an emitter electrode 114 is formed on an insulating substrate 113, a resistor layer 115 is formed on the emitter electrode 114, and an emitter 105 is formed on the resistor layer 115. The resistance layer 115 becomes a resistor in series with the emitter 105.

FIG. 9 shows a prior art disclosed in Japanese Patent Laid-Open No. 4-292831. In FIG. 9, an emitter electrode 114, a resistance layer 115, and an insulating layer
2. The gate electrode 103 is laminated. However, in the portion where the emitter 105 is formed, the emitter electrode 11
4 is absent, so that the spreading resistance of the resistive layer 115 is in series with the emitter 105.

In the cathode shown in FIGS. 8 and 9, the resistance layer below the emitter serves as a negative feedback resistance or a current limiting resistance and limits the current flowing from the emitter. Therefore, for example, conductivity is provided between the emitter and the gate electrode. Even if the dust is sandwiched and the emitter and the gate electrode are short-circuited, the structure of the emitter and the gate electrode is not destroyed by the excessive current. Also, even under the condition that discharge occurs, the current flowing through this resistor is limited.

[0013]

In the field emission cold cathode, the upper part of the emitter 105 cannot be covered with an insulating film or the like in order to extract electrons into a vacuum, and the emitter 105 and the gate electrode 103 which is the peripheral part thereof. Are exposed to the external environment during manufacturing of the cathode and during assembly of the electronic device containing the cold cathode.

During the manufacturing process of the field emission cold cathode, fine dust and adsorbed substances are generated on the side wall of the insulating layer 102 or the emitter 1.
There are many opportunities to adhere to the side surface of 05 and the surface of the gate electrode 103. For example, when the emitter material deposited on the gate electrode 103 is removed by the lift-off method, the substance dissolved in the etching liquid may adhere even in the etching step of etching the sacrificial layer on the gate electrode 103. . Further, in the dicing step of cutting the wafer into individual chips, there is a possibility that chips generated by the dicing saw may adhere. When an electronic device such as a flat display or an electron tube is manufactured by mounting the cold cathode, there is a risk of contamination by gas released from an envelope or an internal electrode.

When these substances adhere to the side surface of the insulating layer 102, they cause a leakage current between the gate electrode 103 and the emitter 105 and a discharge between the gate electrode 103 and the emitter 105.

A cold cathode shown in FIG.
In the structure shown in FIG. 5, the insulating property is improved by the auxiliary insulating layer 111, but the distance between the insulator surface between the emitter 109 and the gate electrode 112 is 0.5 μm or less, which is extremely short. If fine particles or the like generated in the above process adhere to the insulating layer, the insulation during this period is likely to deteriorate.

In the cathode shown in FIG. 7, the hard carbon film or carbon compound coated on the emitter becomes a conductor or a semiconductor, and the insulation resistance and the breakdown voltage of the fine particles such as dust and the adsorbed substances adhered to the side surface of the insulating layer. There is no improvement effect on deterioration.

In the cathodes shown in FIGS. 8 and 9, there is no risk that the entire cathode will be destroyed or the entire cathode region will become unusable due to a short circuit between the emitter and the gate electrode, but conductive dust will adhere. When the emitter 105 and the gate electrode 103 are short-circuited, a current larger than the maximum operating current of the emitter 105 flows, power is consumed, and the resistor portion in which the current flows is heated. Further, no emission current flows from this emitter, and the effective electron emission area is reduced.

[0019]

According to the present invention, Sp
In the indt and gray type cold cathode, the gate electrode, the side wall of the insulating layer, and the emitter are covered with the insulating film except for the tip of the emitter and the part of the gate electrode of the field emission cold cathode.

In order to form this insulating film, a low pressure CVD method or SOG technique is used.

[0021]

As a result, during the manufacturing process of the cold cathode and during the manufacture of the electronic device on which the cold cathode is mounted, the possibility of lowering the insulation resistance between the emitter and gate electrodes and the danger of electric discharge caused by adhesion of dust and adsorption of contaminants is eliminated. be able to.

As a result, the reliability and the production yield of the cold cathode and the electronic device using the cold cathode are improved.

[0023]

The present invention will be described in detail with reference to the drawings. FIG. 1 shows a sectional view of the structure of a field emission cold cathode showing a first embodiment of the present invention. In FIG. 1, an insulating layer 2 and a gate electrode 3 are laminated on a silicon substrate 1 in order from the bottom,
A minute cavity 4 is formed in the gate electrode 3 and the insulating layer 2. In the cavity 4, a conical emitter 5 for emitting electrons is formed by etching the silicon substrate 1. In the cavity 4, the side of the gate electrode 3, the side of the insulating layer 2, and the bottom of the emitter 5 are formed. The insulating film 6 is covered.
The minute cold cathode 7 is formed by the emitter 5, the opening of the gate electrode 3, and the cavity 4.

The insulating layer 2 is made of silicon oxide or silicon nitride, and the gate electrode 3 is made of polysilicon. The diameter of the opening of the gate electrode 3 is about 1 μm,
Is about 1 μm, the thickness of the insulating layer 2 is about 0.8 μm, and the thickness of the gate electrode 3 is about 0.2 μm. Micro cold cathodes having such a fine structure are arranged in a single or array form and used as an electron source, that is, a cathode.

As is apparent from FIG. 1, in the cathode having this structure, the side surfaces of the gate electrode 3 and the insulating layer 2 and the lower part of the emitter 5 are covered with a common insulating film 6. Therefore, as compared with the conventional technique shown in FIG. 6, the insulating surface distance between gate electrode 3 and emitter 5 becomes longer, and even if there is contamination on the surface of the insulator, the current flowing through the surface is sufficiently small. It becomes possible to suppress. As a result, the possibility of insulation resistance deterioration becomes extremely small. Further, it is said that the electron that triggers the minute discharge is easily emitted at the intersection of the electrode to which the negative voltage is applied, the dielectric and the vacuum. In the case of FIG. The insulating film end portion 8 where the nearby insulating film 6 is cut off corresponds to this. Even when electrons are emitted therefrom, the electrons do not hit the surface of an insulator such as the insulating layer 2 or the insulating film 6 and are directly directed to the gate electrode 3 or to the emitter 5 although not shown in the drawing. A voltage is applied to an electrode, for example, an anode. Therefore, there is no need to generate a large number of secondary electrons by colliding with the surface of the insulator to multiply the electrons that cause discharge. Further, even when fine particles adhere to the cavity 4, the possibility that the emitter 5 and the gate electrode 3 are short-circuited by the insulating film 6 on the surface of the emitter 3 is reduced.

The basic structure of this cathode is called Gray type, and its manufacturing method is known (for example, Applied Physics, No. 5).
9, Vol. 2, No. 2, pp. 164-169, 1990. ).
For example, LPCVD (low-pressure CV)
D) deposits an insulator such as silicon oxide or silicon nitride on the entire surface including the inside of the cavity 4, the surface of the emitter 5 and the side surface of the gate electrode 3, and then a part of the dielectric is removed by dry etching or the like. The structure is removed to obtain the structure shown in FIG.

FIG. 2 is a sectional view showing the structure of a field emission cold cathode according to a second embodiment of the present invention. In FIG. 2, the parts with the same numbers as in FIG. 1 indicate the same constituent elements as in FIG. 1, and the materials and dimensions of each constituent element are the same as in the first embodiment shown in FIG. In FIG. 2, the insulating film 6 is formed by a thermal oxidation method. Since polysilicon is used for the gate electrode 3, silicon oxide is formed on the upper and side surfaces of the gate electrode 3. The structure shown in FIG. 2 is realized by removing the oxide on the gate electrode 3 and the tip of the emitter 5 as in the first embodiment.

In this embodiment, the same effect as in the first embodiment can be expected. When the insulating film 6 is not provided, the insulating surface distance between the gate electrode 3 and the substrate 1 (emitter 5) is slightly longer than the thickness of the insulating layer 2;
Is formed, the insulating surface distance can be made 1.5 times or more the thickness of the insulating layer 2. Furthermore, even if electrons are emitted from the portion where the emitter 5 and the insulating layer 6 are in contact, the electrons directly reach the gate electrode and the electrons are not multiplied by the insulator.

FIG. 3 shows a manufacturing process diagram of the field emission cold cathode of FIG. An insulating layer 9 for a mask using an insulator such as silicon nitride is formed on the substrate 1 (FIG. 3A).
Next, the mask insulating layer 9 is patterned to form a mask corresponding to the opening of the gate electrode 3 (FIG. 3B).
The substrate 1 is etched using the mask insulating layer 9 'as a mask to obtain FIG. On this, an insulating layer 2 and a polysilicon gate electrode 3 are deposited in a direction perpendicular to the substrate 1 to obtain FIG. Next, the mask insulating layer 9 '
Is removed by etching, and the insulating film layer 10 of silicon oxide is formed on the side surface and the upper portion of the gate electrode 3 of polysilicon and on the emitter 5 by thermal oxidation to obtain FIG. Here, the tip of the emitter 5 is oxidized from both sides, and a structure with a sharp tip is obtained. Further, the silicon oxide at the tips of the gate electrode 3 and the emitter 5 is removed by etching to obtain FIG.

FIG. 4 is a sectional view showing the structure of a field emission cold cathode according to a third embodiment of the present invention. 4, parts having the same numbers as in FIG. 1 indicate the same constituent elements as those in FIG. 1, and the materials and dimensions of each constituent element are the same as those in the first embodiment shown in FIG. In FIG. 4, the emitter 12 is made of a heat-resistant metal such as tungsten or molybdenum, and the gate electrode 11 is made of a metal or a metal compound such as tungsten, molybdenum, niobium, or tungsten silicide.
For example, a thermal oxide film of silicon (SiO ₂ ) is used for the insulating layer 2. The diameter of the gate opening is about 1 μm and the emitter 12
Has a height of about 1 μm, the insulating layer 2 has a thickness of about 0.8 μm, and the gate electrode 11 has a thickness of about 0.2 μm.

To manufacture this cathode, basically (J
own of Applied Physic
s, Vol. 39, no. 7, pp. 3504,196
8) etc., after forming a cavity in the gate electrode 11 and the insulating layer 2, a sacrificial layer such as aluminum or aluminum oxide is deposited from an oblique direction while rotating the wafer, and then the emitter material is deposited on the wafer. What is necessary is just to deposit from right above. Next, an insulator made of SOG is formed on the wafer, and the gate electrode 11 is formed by means such as etch back.
4 and the insulator on the top of the emitter 12 and the tip of the emitter 12 are removed.
Is formed.

[0032]

As described above, in the cold cathode of the present invention, during the manufacturing process of the cold cathode and the manufacturing of the electronic device on which the cold cathode is mounted, the emitter gate generated by the adhesion of dust and the adsorption of the contaminants is produced. It is possible to eliminate the possibility of lowering the insulation resistance between the electrodes, lowering the withstand voltage and discharging. This improves the reliability and manufacturing yield of the cold cathode and the electronic device using the cold cathode.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a field emission cold cathode according to a first embodiment of the present invention.

FIG. 2 is a structural diagram of a field emission cold cathode showing a second embodiment of the present invention.

FIGS. 3 (a) to 3 (f) are process diagrams for manufacturing a field emission cold cathode according to a second embodiment of the present invention.

FIG. 4 is a structural diagram of a field emission cold cathode showing a third embodiment of the present invention.

FIG. 5 Prior art Spindt type (a) and G
It is sectional drawing of the cold cathode of a ray type (b).

FIG. 6 is a sectional view of a conventional cold cathode disclosed in JP-A-6-53788.

FIG. 7 is a cross-sectional view of a conventional cold cathode disclosed in JP-A-6-131968.

FIG. 8 is a cross-sectional view of a prior art cold cathode disclosed in US Pat. No. 4,940,916.

FIG. 9 is a sectional view of a conventional cold cathode disclosed in JP-A-4-292831.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 101 Substrate 2, 102, 110 Insulating layer 3, 11, 103, 112 Gate electrode 4, 104 Cavity 5, 12, 105, 109 Emitter 6, 13 Insulating film 7 Micro cold cathode 8 Insulating film edge 9 Insulation for mask Layer 10 insulating film layer 106 equipotential surface 107 electron beam orbit 108 silicon substrate 111 auxiliary insulating layer 113 insulating substrate 114 emitter electrode 115 resistance layer

Claims (5)

[Claims] 1. A substrate, an electron-emitting electrode formed on the substrate by an etching method and having a sharpened tip, an insulating layer formed on the substrate except the electron-emitting electrode and its vicinity, In an array-type field emission cold cathode composed of a plurality of minute cold cathodes including a control electrode having an opening surrounding the electron emission electrode, at least a side wall of the insulating layer and the vicinity of the substrate of the electron emission electrode are formed of an insulating film. Arrayed field emission example cathode characterized by being coated. 2. A substrate, an electron-emitting electrode formed on the substrate by a film deposition method and having a sharpened tip, and an insulating layer formed on the substrate except the electron-emitting electrode and its vicinity. In an array-type field emission cold cathode composed of a plurality of minute cold cathodes each including a control electrode having an opening surrounding the electron emission electrode, at least a side wall of the insulating layer and the vicinity of the substrate of the electron emission electrode are formed of an insulating film. An array-type field emission cold cathode characterized by being coated. 3. The method for manufacturing an array field emission cold cathode according to claim 1, wherein the insulating film is formed by a low pressure CVD method. 4. The method of manufacturing an array field emission cold cathode according to claim 1, wherein the control electrode is formed of polysilicon, and the insulating film is formed by a thermal oxidation method. 5. The insulating film is SOG (Spin on)
The method for manufacturing an array-type field emission cold cathode according to claim 2, wherein the film is formed by a glass method.