JPH08148083A - Surface reforming method for field emitter - Google Patents

Abstract

PURPOSE: To prevent short-circuiting between a cathode electrode layer and a gate electrode layer by coating a wall surface in a hole provided in a field emission cathode with a resist, thereafter coating an emitter with a low work function material, and removing the resist. CONSTITUTION: A cathode electrode layer 101, resistance layer 102, insulating layer 103 and a gate electrode layer 104 are molded on a glass substrate 100, to from in the insulating layer 103 a hole formed with an emitter cone 115 in the inside. Next on the electrode layer 104, a photoresist 1 is applied, and after the hole is buried with the photoresist 1, the emitter cone 115 is exposed to form a film of a photoresist 2 in a wall surface of the insulating layer 103 in the hole. Then by spattering a low work function material, after its films 3, 4 are formed in surface of the emitter cone 115 and the electrode layer 104, the photoresist 2 in the hole is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission cathode known as a cold cathode and relates to a method for modifying the surface of an emitter.

[0002]

2. Description of the Related Art The voltage applied to the surface of a metal or semiconductor is 10
^At about ⁹ [V / m], electrons pass through the barrier due to the tunnel effect, and the electrons are emitted in vacuum even at room temperature. This is called field emission, and the cathode that emits electrons based on this principle is called a field emission cathode or field emission element.

In recent years, it has become possible to fabricate a surface-emission type field emission cathode consisting of micron-sized field emission cathodes by making full use of semiconductor fine processing technology, and forming a large number of field emission cathodes on a substrate. These devices are expected to serve as an electron supply unit that constitutes a flat display device and various electronic devices by irradiating the phosphor screen with electrons emitted from the respective emitters.

As an example of such a field emission cathode, a perspective view of a field emission cathode called a Spindt type (hereinafter referred to as FEC) is shown in FIG. In this figure, a cathode electrode layer 101 is formed on a substrate 100, and the resistance layer 1 is formed on the cathode electrode layer 101.
02, the insulating layer 103, and the gate electrode layer 104 are sequentially formed. Then, an emitter cone 115 is formed in the hole formed in the insulating layer 103, and a tip end portion of the emitter cone 115 faces the opening of the gate electrode layer 104.

In this FEC, the emitter cone 115 and the gate electrode layer 1 are formed by using a fine processing technique.
Since the distance from 04 can be submicron,
By applying a voltage of only a few tens of volts between the emitter cone 115 and the gate electrode layer 104, electrons can be emitted from the emitter cone 115.

Therefore, as shown in FIG.
An anode substrate 116 coated with a fluorescent material is arranged above a substrate 100 on which a large number of ECs are formed in an array, and when the voltages V _GE and V _A are applied, the fluorescent material is caused to emit light by the emitted electrons. It can be used as a display device.

An example of the manufacturing process of the Spindt-type FEC will be described with reference to FIG. First, (a) of FIG.
As shown in FIG. 2, Nb (niobium), which is a cathode material, is sputtered onto a substrate 100 such as glass by sputtering to a thickness of 0.2 μm.
A thin film conductor layer 101 is formed by m film formation, and Si (amorphous) doped with impurities is further formed on the thin film conductor layer 101 by C.
Resistive layer 1 formed by VD (Chemical Vapor Deposition)
02 is formed, and SiO ₂ (silicon oxide) is further added to the CV.
The insulating layer 103 is formed by forming a film by D. Then, Nb to be the gate electrode layer 104 is formed thereon by sputtering to a thickness of 0.4 μm.

Furthermore, the gate electrode layer 104 which is the outermost surface
After applying the photoresist layer 111 on top, the mask 11
The resist layer 11 is formed by photolithography by applying 2
Patterning 1 is performed. As a result, an opening pattern is formed in the photoresist layer 111.

Next, anisotropic etching is performed by reactive ion etching (RIE) from the direction in which the resist 111 is applied using a gas such as SF ₆ to obtain a gas as shown in FIG. An opening 113 similar to the resist pattern is formed in the gate electrode layer 104.

Next, the laminated substrate is dipped in an etching solution such as buffered hydrofluoric acid (BHF) and the insulating layer 103 is isotropically etched, as shown in FIG. A hole 114 is formed in

Then, while the substrate is rotated in the same plane and Al (aluminum) to be the peeling layer 105 is obliquely vapor-deposited, Al is not vapor-deposited in the holes 114, and FIG. As shown in FIG.
The peeling layer 105 is formed by selectively adhering only to the surface of the.

Next, when Mo (molybdenum), which is an emitter material, is deposited on the hole 114 side of such a substrate by vapor deposition, the vaporized emitter material is deposited on the bottom side of the hole 114, that is, as shown in FIG. At the same time as vapor deposition / deposition on the resistance layer 102, the emitter material 106 is also deposited on the peeling layer 105. Then, the peeling layer 105
The opening is closed by the emitter material 106 deposited thereon, and at the same time, a cone-shaped emitter 115 is formed on the resistance layer 102.

After that, the substrate is immersed in phosphoric acid which is a solution of the peeling layer 105 to remove the peeling layer 105 on the gate electrode layer 104 and the emitter material layer 106.
As a result, it is possible to obtain an FEC having a shape as shown in FIG.

[0014]

By the way, in the above-mentioned FEC, it is necessary to use a substance having a low work function (and surface inactivity) as an emitter material in order to emit an emission from the emitter at a low applied voltage. As already reported, low work function materials include TiN and LaB ₆ , but when these are tried to be deposited by vapor deposition, TiN
In that case, N is La, and in the case of LaB ₆ , light elements such as B are missing during the vapor deposition, and it has been difficult to produce a good compound such as TiN or LaB ₆ .

To solve the above problems, there is a method called reactive vapor deposition. For example, when depositing TiN,
Since N is likely to be lost, it is a method of performing vapor deposition while introducing N ₂ gas or the like into the vapor deposition chamber in order to compensate for it. As a result, it is possible to prevent the loss of N, and to obtain a relatively high quality T
iN is obtained. However, it is essential to introduce a reactive gas into the deposition chamber, which shortens the mean free path of molecules in the chamber. Then, as shown in FIG. 4, the substance 118 having a slightly low work function is also formed on the wall surface of the insulating layer 103. Therefore, there is a possibility that the cathode electrode layer 102 and the gate electrode layer 104 may be short-circuited.

Further, as disclosed in Japanese Examined Patent Publication (Kokoku) No. 54-36828, when the emitter cone is coated with a high melting point material, as shown in FIG.
The surface of the extraction electrode layer (gate electrode layer) 122 is formed by projecting (overhanging) by μm or more and performing vapor deposition.
It is useful for a field emission cathode manufactured by an etching method, since the surface of the emitter cone 123 and the surface of the emitter cone 123 are coated so that the insulation between the substrate 120 and the extraction electrode 122 can be maintained. However, in the FEC manufactured by the Spindt method, as shown in FIG. 3E, the gate electrode layer 10 is formed above the insulating layer 103 of the FEC.
4 is formed, when the amount of overhang of the gate electrode layer 104 increases, the gate electrode layer 104 sags, and the emitter cone 115 and the gate electrode layer 104
A short circuit occurs.

When diamond carbon is formed as the emitter material by the CVD method or the like, since the wraparound is large, the surface of the insulating layer is also coated and the state as shown in FIG.
There is a problem that 4 is short-circuited.

The present invention has been made in order to solve the above problems and provides a method for modifying the surface of a field emitter by coating the surface of the FEC emitter cone manufactured by the Spindt method with a material having a low work function. It is intended to be provided.

[0019]

To achieve the above object, holes are formed in a gate electrode layer and an insulating layer in a laminated substrate in which a cathode electrode layer, an insulating layer, and a gate electrode layer are sequentially formed on at least the substrate. In a field emission cathode provided with an emitter formed in the hole, after filling the hole with a resist by a spinner or the like, at least the resist formed on the emitter is removed.
And a second step of coating the tip of the emitter surface with a material having a low work function by a sputtering method, and a first step
The third step of removing the low work function material adhering to the inside of the hole of the emitter together with the remaining resist by the above step.

[0020]

According to the present invention, the steps are such that the wall surface inside the hole formed in the FEC is coated with a resist, the emitter is coated with a material having a low work function, and then the resist is removed. The coating material can be prevented from adhering to the wall surface of the insulating layer regardless of the amount of overhang, and the gate electrode layer and the cathode electrode layer are covered with the low work function material.

[0021]

FIG. 1 shows an example of a method for modifying an emitter cone of a field emission cathode as an embodiment of the present invention. FIG. 3A shows an FEC manufactured by the Spindt method described in FIG. 3, in which a cathode electrode layer 101, a resistance layer 102, an insulating layer 103, and a gate electrode layer 104 are sequentially formed on a glass substrate 100. Has been done. Then, the insulating layer 103
A hole is formed in the hole, and an emitter cone 115 is formed in the hole.

Next, in FIG. 2B, reference numeral 1 is a low-viscosity positive photoresist, which is applied on the gate electrode layer 104 by using a spinner or the like. At this time, the insulating layer 10
The photoresist 1 permeates into the holes formed in 3 and the holes are completely filled with the photoresist.

Then, when the emitter cone 115 is exposed from the upper surface of the gate electrode layer 104 without using a photomask,
Since the wall surface of the insulating layer 103 in the hole, which is directly below the eaves of the gate electrode layer 104, is not exposed to light and is not exposed,
As shown in FIG. 3C, the photoresist 2 is self-aligned.
Is formed.

Next, high melting point materials such as W (tungsten) and Ta (tantalum) and materials having a low work function (for example, nitrides such as TiN, TaN and ZrN, Si compounds, carbon or carbon compounds, (Ba). , Sr) O (C
a, Sr) O and other barium oxides, (La, B) B
_{6, (La, Eu) B} 6, (La, Yb) B lanthanum Poraido compounds such as _{6, (Pr, Sr) B} 6, (P
_{r, Eu) B 6, (} Pr, Yb) B praseodymium Poraido compounds such as _{6, (Nd, Sr) B} 6, (Nd,
Ba) B ₆ , (Nd, Eu) B ₆ , (Nd, Yb) B
₆ , etc. are sputtered by, for example, a sputtering method which is a physical vapor condensation method (Physical Vapor Deposition).

For example, when TiN having a low work function is sputtered, Ti is formed on the surface of the gate electrode layer 104 and the surface of the emitter cone 115 as shown in FIG.
N sputter films 3 and 4 are formed. Similarly, on the side surface of the photoresist 2, a sputtered film 5 of the material TiN having a low work function is formed. This is because, in general, sputtering is performed at a vacuum degree of about 10 ⁻³ Torr, so that wraparound of sputtered electrons occurs. That is, the photoresist 2 acts as a mask that prevents the low work function material from directly adhering to the wall surface of the insulating layer 103.

Then, the photoresist 2 in the hole is removed with a photoresist stripping solution to remove together with the low work function material 5 attached to the side surface of the photoresist 2. Therefore, as shown in FIG. 8E, the sputter films 3 and 4 of the low work function material TiN are left only on the surfaces of the gate electrode layer 104 and the emitter cone 115. That is, the surface of the emitter cone 115 can be modified to the material TiN having a low work function.

Further, the sputtered film 3 formed on the gate electrode layer 104 is anisotropic by reactive ion etching (RIE) using SF ₆ gas if the low work function material to be sputtered is TiN. It can be removed by etching, and when forming a gate wiring over the gate electrode layer 104, the conventional technique can be used as it is.

Although the FEC manufactured by the Spindt method has been described in the present embodiment, the present invention is not limited to this and can be applied to an FEC manufactured by a silicon etching type or the like and the shape of the emitter. It is of course possible to apply a variant of roof type.

[0029]

As described above, in the method for modifying the field emitter of the present invention, after the insulating layer in the hole is coated with the resist, the low work function material is sputtered. It is possible to prevent a short circuit between the cathode electrode layer and the gate electrode layer, regardless of the amount of overhang, and to coat the emitter cone with a material having a low work function. Therefore, the surface of the emitter cone can be made to have a low work function and a high current density can be dealt with, and in particular, the electron emission capability of the tip portion can be maintained in a high state.

Further, in the case of sputtering, it is possible to form a uniform thin film in a large area with a high throughput as compared with vapor deposition. Since the emitter is coated with this thin film, the field emission becomes uniform, and it is possible to use it for many years. Can also be a stable field emission cathode.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a method for modifying a surface of a field emitter according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a display device using an FEC array.

FIG. 3 is a diagram showing an example of a method for manufacturing a field emission cathode.

FIG. 4 is a diagram showing a mode of deposition by sputtering when a resist is not used.

FIG. 5 is a diagram showing an example of coating of a field emission cathode manufactured by a conventional etching method.

[Explanation of symbols]

 1, 2 resist 3, 4, 5 sputtered film

Claims (3)

[Claims] 1. A laminated substrate in which a cathode electrode layer, an insulating layer, and a gate electrode layer are sequentially formed on at least the substrate,
In a field emission cathode in which a hole is provided in the gate electrode layer and the insulating layer, and an emitter is formed in the hole, the hole is formed at least above the emitter after a resist is filled in the hole by a spinner method or the like. A first step of removing the resist that has been removed, a second step of coating the tip of the emitter surface with a material having a low work function by a physical vapor condensation method, and the holes left by the first step. A method of modifying the surface of a field emitter, comprising a third step of stripping the resist inside, wherein the surface of the emitter is coated with the low work function material. 2. The method for modifying a surface of a field emitter according to claim 1, wherein the resist is a positive photoresist. 3. The method according to claim 1, wherein the physical vapor condensation method is a method of forming a film in a relatively low vacuum (10 ⁻⁴ to 10 ⁻¹ torr), such as a sputtering method. Surface emitter surface modification method.