JPH02239538A - Planar cold cathode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electron source using a planar cold cathode.

BACKGROUND OF THE INVENTION Many thin film field emission type cold cathodes have been reported in the past. Among them, a planar cold cathode as shown in Fig. 6 (Fig. 5 of JP-A No. 63-274047) has an 80V
Electron emission is said to occur at gate voltages above this level. As shown in FIG. 6, this cold cathode is constructed by having a cold cathode 2 and a gate electrode 3 facing each other on the surface of an insulating substrate 1. A large number of convex portions 4 are formed at the edge of the cold cathode facing the gate electrode. The distance between the tip of the convex cane provided on this cold cathode and the gate electrode was 0.1 μm. When a voltage of 80 V or more is applied between the cold cathode and the gate electrode configured in this way, the radius of curvature of the tip of the convex part of the cold cathode is small, so the convex part receives a strong force of 2×10'V/cm. An electric field is generated and electrons are emitted from the tip.

Problems to be Solved by the Invention Although the planar cold cathode described above has the above-mentioned characteristics7, in order to put it into practical use, it is necessary to
It is necessary to widen the distance between the cooling pole and the gate electrode to about 2 to 4 μm. In order to satisfy these conditions, a convex portion of the cold cathode with an even smaller radius of curvature is required, but current photoetching techniques have limitations.

In addition, in the electric field formed by such a pair of thin films, since the film thicknesses of both electrodes are about the same, the strong electric field formed on the surface of the electron-emitting electrode due to variations in electrode processing is effective and reproducible. As a result, there was a problem in that the electron emission start voltage varied between devices.

Means for Solving the Problem In a planar cold cathode consisting of two pairs of electrodes formed on the surface of an insulating substrate, a gate applies an electric field to the surface formed by the electrode that emits electrons. At least a portion of the electrode near the electron emitting electrode has an angle of 60 to 160
Form a surface of 1f.

By forming a step on the working gate electrode and forming an angle with respect to the electron-emitting electrode to form a structure that uniformly forms a strong electric field on the electron-emitting surface, it is possible to create a planar cold cathode with a conventional configuration. In comparison, a planar cold cathode with a stable electron emission start voltage can be obtained.

Examples Example 1 FIG. 1 shows the main part of the electrode structure of Example 1. 1! The pole is composed of an electron-emitting electrode (cold cathode) 7 and a gate electrode 8 bent on the electron-emitting electrode side facing each other on the surface of an insulating layer 6 formed on the surface of a substrate 5.

A method of manufacturing this planar cold cathode will be explained. S
After forming Si021KB with a thickness of 1.5 μm as an insulating layer on the surface of the i-wafer substrate 5 by thermal oxidation, the edge of the gate electrode of this SiOaK% is etched by photoetching.
．． A groove with a depth of 5 μm is formed.

At this time, the slope of the groove can be controlled depending on the method of forming the groove. For example, with sputter etching, a steep slope can be obtained, and with wet etching, the amount of side etching changes depending on the etching rate, so the slope can be easily changed. In addition, the lift-off method can also obtain an inclination in the opposite direction. This surface has a thickness of 0.2 μm.
A WSis film is formed on the entire surface, and a cold cathode 7 and a gate electrode 8 are simultaneously formed by photoetching.

At this time, mask alignment is required so as to leave the groove of the gate electrode, but it can be easily formed because it can be done with precision enough to cover the groove or leave the electrode at the bottom of the groove. At this time, the angle formed between the gate electrode remaining in the groove and the electron emitting electrode (cold cathode) surface is controlled by the groove forming method described above.

Here, the distance between the cold cathode and the gate electrode is 1 to 4 μm. This substrate was then etched with a buffered etch solution (HFI and NH).
The Si02 film is further etched by dipping in a mixed solution of 4F6 volume to form a recess 9 at the bottom of the cold cathode tip, making the cold cathode tip shaped like an eave.

Furthermore, this substrate is immersed in fluoronitric acid, and the eaves-like portion of the cold cathode is etched from above and below to a thickness of 200 to 1000 mm.
A cold cathode having a tip 10 was formed.

The combination of electrode material and insulating material is not limited to WSi* and Si02, but W. M01
W2 C) N b C+ H f (1: It is possible to combine a material with a high melting point, a low work function, and which is hardly soluble in a buffer etch solution, and a material that dissolves in a buffer etch solution such as a glass plate as an insulating substrate material. It is.

60 to 10 between the cold cathode and the gate electrode configured as above
When a voltage of 0V is applied, 10'V/c is applied to the cold cathode tip.
A strong electric field of more than m is generated, and electrons are emitted from the tip.

FIG. 7 shows the relationship between the thickness of the cold cathode tip and the electron emission starting voltage in a conventional configuration in which the gate electrode is parallel to the electron emission electrode. 01 mouth, Δ and the distance between the cold cathode and the gate electrode are each 1.2 μm1! ．． 7μmq 2.2
The graph shows the emission start voltage at 1 time when gm and 2.6 μm are set to 5. As can be seen from FIG. 7, the electron emission start voltage hardly depends on the distance between the cold cathode and the gate electrode, but depends on the thickness of the cold cathode tip.

Furthermore, it can be seen that there is a large variation in the electron emission start voltage within the range of 30V.

Figure 2 shows that the distance between the gate electrode and the electron emission electrode is 1.7μ.
m1 When the film thickness of the electron emitting electrode tip 10 is 400 mm, the relationship between the angle formed by the electron emitting electrode and the groove formed in the groove of the gate electrode and the electron emission starting voltage is shown. As can be seen from FIG. 2, the electron emission start voltage is unchanged from the conventional case at an angle of 160 degrees or more, and is approximately saturated at about 135 degrees. From this, it is desirable that the angle formed between the electron-emitting electrode and the surface formed in the groove of the gate i-pole is 160 degrees or less, preferably 135 degrees or less.

Further, although an angle of 90 degrees or less is possible by the lift-off method, an angle of 60 degrees or more is preferable because techniques such as a vapor thinning method and resist exposure are limited in metal film formation and photoetching process 1-.

Further, in the configuration of this embodiment, the variation in the ionization start voltage can be suppressed to about 10 V in the range of 90 to 135 degrees, whereas it was 30 V in the conventional configuration.

As in the present invention, when the thickness of the tip of the electron-emitting electrode (cold cathode) is less than i ooo and the distance between the two electrodes is 1 μm or more, lines of electric force are generated radially from the cross section of the tip of the cold cathode. Therefore? A part of the electrons emitted from the cathode flows into the gate electrode, and most of the electron beam can be extracted to the outside.

Furthermore, with the electrode configuration shown in Figure 3, the electrons emitted from the cold cathode are emitted perpendicularly to the opposing electrode surfaces, and the gap does not widen in the longitudinal direction, allowing it to be used as an electron source for display devices. When doing so, it has the advantage of significantly reducing crosstalk.

Example 2 FIG. 4 shows the main part of the electrode structure of Example 2. An insulating layer with a thickness of 2μ is formed on the surface of the Si wafer substrate 11 by thermal oxidation.
After forming the Sins film 12 with a thickness of m, a groove with a depth of 1 μm is formed in the vicinity of the end of the gate electrode as in the first embodiment. In this case 11
An angle of approximately 0 degrees was observed from the cross-sectional SEM photograph. A WSizl film with a thickness of 0.2 μm is formed on the entire surface of this SXOe film, and a cold cathode 13 and a gate electrode 14 are simultaneously formed by photo-etching. be. Next, this substrate is immersed in a Pabfa etch solution to remove the siO* film so that the eaves of the cold cathode are 0. Etch until the length is l tt m. Next, this substrate is immersed in fufu nitric acid, and the eaves-like part of the cold cathode is etched from above and below to form a cold cathode having a sharp tip shape 15.

Furthermore, this substrate is again immersed in a buffer solution and the Si02 film is etched 7 to form a recess 16 at the bottom of the cold cathode tip.

50 to 60 mm between the cold cathode and the gate electrode configured in this way.
When a voltage of V is applied, a voltage of 10”V/cm is applied to the cold cathode tip.
A stronger electric field is generated, and electrons are emitted from the tip.

Example 3 FIG. 5e shows the main part of the electrode structure of Example 3.

The electrode is formed of a double layer of conductive material 17 and cold cathode material 18.

Figure 5 shows the manufacturing process for this planar cold cathode.
A thermally oxidized SiOZ insulating layer 24 is formed on the Si substrate 19. A groove 2e is formed in this insulating layer.

Furthermore, on this surface, a 0.2 μm thick W Si +l
i 17 and a 500 mm thick WC film 18 on its surface.
(Fig. 5b). A cold cathode section 20 and a gate electrode section 21 are simultaneously formed from this double layer of WSi2 and WC by photoetching. The distance between the cold cathode and the gate electrode is 1 to 4 μm (FIG. 5C). Next, this substrate is immersed in a buffer etch solution to etch the insulating layer 24 to form a recess 22 at the lower part of the cold cathode tip, thereby making the cold cathode tip shaped like an eave (FIG. 5d). Further, this substrate was immersed in hydrofluoric nitric acid, and only the WSi2 film 17 below the tip of the electrode double layer was removed by etching, forming a cold cathode having a WC tip 23 with a thickness of 500 mm (Fig. 5). e).

The conductive material 17 serves to reduce the resistance of the cathode, gate electrode, and wiring, and to increase the adhesive strength between the cold cathode material and the substrate material.

The combination of the conductive material and cold cathode material of the electrode double layer is WS.
Not limited to i* and WC, conductive materials such as W+ M O3 Wa C+ N b C+ H
f C, etc., materials that are soluble in fluoro-nitric acid and poorly soluble in Babuf 1 etch solution, and as cold cathode materials, WC = S I
ClTa%B. It is possible to combine low work function materials that are sparingly soluble in the nitric acid and buff T etch solutions, such as C.

Furthermore, any material that is sparingly soluble in solutions for etching substrate materials and acidic and alkaline solutions for etching conductive materials and has a relatively low work function can be used as a cold cathode material. In addition, as conductive materials, acids other than fluoro-nitric acid, metal materials that dissolve in alkaline solutions, and Au
Alloy materials such as Cr can be used. Furthermore, if necessary, it is possible to form an electrode with a double layer or more.

60 to 10 between the cold cathode and the gate electrode configured as above
When a voltage of 0V is applied, the tip of the cold cathode has 1 0? V/
A strong electric field of more than C rrx is generated, and electrons are emitted from the tip.

Effects of the Invention According to the present invention, the surface of the gate electrode on which the electron emission electrode is formed is 60 to 16
By forming a 0 degree plane, a stable electron emission starting voltage can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a planar cold cathode according to an embodiment of the present invention, FIG. 2 is a graph showing the relationship between the angle between the electron emission electrode surface and the gate electrode surface and the electron emission start voltage, and FIG. 3 is a perspective view of a planar cold cathode according to one embodiment of the present invention, FIG. 4 is a sectional view of a planar cold cathode according to another embodiment of the present invention, and FIG. 5 is a perspective view of a planar cold cathode according to another embodiment of the present invention. A cross-sectional view for explaining the manufacturing process of a planar cold cathode in an example, FIG. 8 is a perspective view of a conventional planar cold cathode, and FIG. 7 is an electron emitting electrode film thickness and electron emission starting voltage of a conventional configuration. FIG. 1Φφ fist insulator substrate, 2, 7, 13. 20
, 24-●●cold cathode, 3, 8, 14. 21
, 25-● Reference gate electrode, 4●-e cold cathode convex portion, 5.
11, 19●●●Si wafer substrate, 8, 12, 24-
●●Insulating layer, 9.1B. 22●@Fist insulation layer recess, 10,
15, 23●●●cold cathode tip, 17-●conductive material, 18φ fist●cold cathode material, 26●ΦlI groove. Name of agent Patent attorney Shigetaka Awano and 1 other person 1st Kuanbaku θ Scroll 249 Child release practice I 25 yen bt indulgence / Figure

Claims (4)

[Claims] (1) In a planar cold cathode consisting of two pairs of electrodes formed on the surface of an insulating substrate, the other electrode (which applies an electric field to the surface formed by the electron-emitting electrode)
A planar cold cathode characterized in that at least a portion of the electron emitting electrode (hereinafter referred to as a gate electrode) in the vicinity thereof forms a surface with an angle of 60 to 160 degrees. (2) The planar cold cathode according to claim 1, wherein the thickness of the tip of the electron-emitting electrode is 0.1 μm or less. (3) The planar cold cathode according to claim 1 or 2, wherein the distance between the tip of the electron-emitting electrode and the opposing gate electrode is 0.3 μm or more and 5 μm or less. (4) A planar type cooling device according to any one of claims 1 to 3, wherein a part of the insulating substrate under the cold cathode tip is removed, and the cold cathode tip is formed in an eave shape. cathode.