JPH0612976A - Forming method for field emission cathode - Google Patents

Abstract

PURPOSE:To provide a forming method for a field emission cathode whereby a distance between an emitter tip and an anode electrode can be shortened, possible to perform high speed action by decreasing a running distance of an electron and further possible to easily and stably form the cathode. CONSTITUTION:The first insulating film 2 is formed in a region except a region of forming a gate and emitter of a substrate 1, to form a conductive film 3 in a front surface, and etching of the concerned conductive film 3 is performed to form an anode pattern 3a of comprising a pad part 3b, support part 3d and an anode part 3c. Thereafter, the anode pattern 3a serves as a mask, to perform etching of the substrate 1 between the first insulating films 2 in a condition that the predetermined side etching is provided, and an emitter tip 1a acute in the uppermost part is formed just below the anode part 3c of the anode pattern 3a. Next, the second insulating film 4 and a gate electrode 5 are successively formed on the substrate 1 between the first insulating film 2 and the emitter tip 1a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a field emission cathode, and more particularly, it can be applied to a method for forming a minute cold cathode used in a display device, a micro vacuum tube, etc.
In particular, the present invention relates to a method for forming a field emission cathode that can shorten the distance traveled by electrons by shortening the distance between the emitter tip and the anode electrode.

In recent years, micro cold cathodes have been used for display elements, micro vacuum tubes, etc., and in the latter micro vacuum tubes, the mobility of electrons is higher than that of semiconductor elements,
Utilizing the features of high-speed and high-temperature operation and resistance to radiation damage, it is expected to be applied to microwave elements, ultra-high-speed arithmetic elements, radiation environments such as space and nuclear reactors, high-temperature environments, and display elements.

[0003]

2. Description of the Related Art FIG. 4 is a view showing the structure of a field emission cathode used in a micro vacuum tube. In FIG. 4A, a conical emitter tip 32 is formed on a silicon substrate 31, a silicon oxide film 33 is formed so as to surround the emitter tip 32, and the emitter tip 32 is further formed.
The gate electrode 35 having the opening 34 is formed above.

Further, in FIG. 4B, the emitter tip 32 and the gate electrode 35 are formed on the silicon substrate 31 so as to be opposed to each other and spaced from each other. In the field emission cathodes of FIGS. 4A and 4B, by applying a voltage between the emitter tip 32 and the gate electrode 35, a large electric field is applied to the cone tip of the emitter tip 32 to cause field emission. You can

Next, FIG. 5 is a diagram for explaining a conventional method for forming a field emission cathode. 5, the same reference numerals as those in FIG. 4 indicate the same or corresponding portions, 41 is a silicon oxide film such as SiO ₂ formed by thermally oxidizing the silicon substrate 31, and 41a is formed by etching the silicon oxide film 41. 42 is a silicon substrate.
S formed by thermally oxidizing the surface of the emitter tip 32 of 31
It is a silicon oxide film such as iO ₂ . Reference numerals 43 and 44 respectively denote an insulating film such as SiO _{2 and} a conductive film such as Cr.
Is a gate electrode formed by etching the conductive film 44.

Next, a method of forming the field emission cathode will be described. First, as shown in FIG. 5A, the n-type silicon substrate 31 is thermally oxidized to form a silicon oxide film 41 on the silicon substrate 31.
5B, the silicon oxide film 41 is etched into a circular shape by reactive ion etching (RIE) to form a circular mask pattern 41a, as shown in FIG. 5B.

Next, as shown in FIG. 5C, a mask pattern is formed by RIE using the mask pattern 41a as a mask.
The emitter tip 32 is formed by etching under the condition that an appropriate side etching occurs at the lower part of 41a. At this time, the side etching of the upper portion of the silicon substrate 31 progresses to form cones, but the etching is terminated in a state where the mask pattern 41a remains so that it cannot be removed. In this state, since the tip of the emitter tip 32 is flat and not sharp, the mask pattern 41a can be left on the flat portion of the tip of the emitter tip 32. After that, as shown in FIG. 5D, the silicon is thermally oxidized on the emitter tip 32 of the silicon substrate 31 to form a silicon oxide film 42 on the surface of the emitter tip 32. This process forms a very sharp tip of silicon inside the emitter tip 32.

By patterning the Cr conductive film 44 and forming the gate electrode 44a, a field emission cathode as shown in FIG. 5 (g) can be obtained. Next, as shown in FIG. 5E, SiO ₂ and Cr are vapor-deposited in order to form the insulating film 43 and the conductive film 44, and then immersed in hydrofluoric acid as shown in FIG. 5F. Then, the silicon oxide film 42 on the surface of the emitter tip 32 is removed, and the mask pattern 41a is formed.
The insulating film 43 and the conductive film 44 thereabove are removed by lift-off.

In the above-mentioned conventional field emission cathode, a silicon oxide film 41 having a circular shape is used, and an upper part of the silicon substrate 31 is etched to form an emitter tip 32 so that side etching can be performed under the mask pattern 41a. ,
In order to prevent the mask pattern 41a from coming off, the emitter tip 32 is not etched at an acute angle and etching is stopped in a flat state, and the emitter tip 32 is thermally oxidized while leaving the mask pattern 41a so as not to come off.
The tip is sharp. Emitter tip
32 If the tip is etched to an acute angle, the mask pattern 41a is separated, and in this state, the gate opening is formed even if the insulating film 43 and the conductive film 44 are formed on the entire surface and etched. Is very difficult. Therefore, as described above, the insulating film 43 and the conductive film 44 are formed by vapor deposition with the mask pattern 41a left, and the silicon oxide film 42 portion on the surface of the emitter tip 32 is removed by lift-off to remove the mask pattern 41a. The gate opening is formed by removing the insulating film 43 and the conductive film 44 on the gate insulating film.

[0010]

However, in the above-described conventional method for forming a field emission cathode, as shown in FIG. 6, the anode electrode 51 is on the insulating film 43 outside the gate electrode 44a with respect to the emitter tip 32. Since it is formed apart from the gate electrode 44a (about 1 μm at the photolithography limit), when trying to operate at high speed, the distance between the emitter tip 32 and the anode electrode 51 is long and the traveling distance of electrons is long. There was a problem that it could not be operated at high speed.

Therefore, in order to shorten the distance between the emitter tip 32 and the anode electrode 51 and shorten the traveling distance of electrons, it is easily guessed that the anode electrode 51 should be arranged right above the emitter tip 32. However, it is very difficult to realize the structure from the above-described conventional method for forming a field emission cathode, and no method for forming the field emission cathode has been reported yet.

Therefore, according to the present invention, the distance between the emitter tip and the anode electrode can be shortened, the traveling distance of electrons can be shortened, high speed operation can be performed, and the electric field can be easily and stably formed. It is an object to provide a method for forming an emission cathode.

[0013]

In order to achieve the above object, the method for forming a field emission cathode according to the present invention provides a field emission cathode having a sharp pointed portion on a substrate from which an electron beam is extracted by field emission. In the forming method, an emitter is formed by etching using a conductive film as a mask, then an insulating film and an extraction electrode film are formed, and the conductive film of the mask is used as an anode.

In order to achieve the above object, the method for forming a field emission cathode according to the present invention comprises a step of forming a first insulating film on a region of a substrate other than a region where a gate and an emitter are formed,
Next, a step of forming a conductive film on the entire surface, and then, etching the conductive film to form a pad portion on the first insulating film, and an anode portion on the substrate between the pad portions. And a support part having a width smaller than the width of the anode part is formed between the anode part and the pad part, thereby forming an anode pattern composed of the pad part, the support part and the anode part. Process, and then
Using the anode pattern as a mask, etching the substrate 1 between the first insulating films under a condition that a predetermined side etching is performed to form an emitter tip having an acute uppermost portion just below the anode portion of the anode pattern; Then, a step of sequentially forming a second insulating film and a gate electrode on the silicon substrate between the first insulating film and the emitter tip is included.

[0015]

In the present invention, as shown in FIGS. 1 to 3 of an embodiment described later, the anode pattern 3a is formed on the insulating film 2 and the pad portion 3b and the silicon substrate 1 are formed into a substantially circular shape (anode portion). An anode part 3c having an acute tip tip 3a immediately below 3c and a width smaller than the width of the anode part 3c formed between the anode part 3c and the pad part 3b (the emitter tip 1 below the support part 3d).
Since the silicon substrate 1 is etched using the anode pattern 3a under conditions where side etching is appropriately performed, the tip is provided only under the anode portion 3c of the anode pattern 3a. It is possible to form the emitter tip 1a having an acute angle. At this time, the emitter tip 1a and the pad portion 3
b are spaced apart, but since the emitter tip 1a is supported by the support portion 3d integrally formed with the pad portion 3b formed on the insulating film 2, the emitter tip 1a is also supported during the process and after mounting. It can be done without letting go.

Moreover, since the anode pattern 3a is integrally formed of the pad portion 3b, the support portion 3d and the anode portion 3c, the anode portion 3c which has received the electrons emitted from the emitter tip 1a has the support portion 3d. It can be drawn as a current from the pad portion 3b connected to the external circuit via the pad portion 3b.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1A and 1B are views showing the structure of a field emission cathode according to an embodiment of the present invention. FIG. 1A is a plan view thereof, and FIG.
1-A2 direction sectional view, FIG. 1C is a B1-B2 direction sectional view. 2 and 3 are views for explaining a method for forming a field emission cathode according to an embodiment of the present invention.

1-3, 1 is a silicon substrate
1a is formed by etching the upper part of the silicon substrate 1.
The tip is a sharp-edged emitter tip, and 2 is silicon
SiO formed by thermally oxidizing the substrate 1.₂With an insulating film such as
Yes, 3 is the entire surface of the silicon substrate 1 on which the insulating film 2 is formed
It is a conductive film of Cr or the like formed on. Then 3a
Anode pattern formed by etching the conductive film 3
The anode pattern 3a is formed on the insulating film 2.
Formed pad portion 3b and silicon between the pad portions 3b
A substantially circular anode part 3c formed on the substrate 1,
Anode part formed on the anode part 3c and the pad part 3b
It consists of a support part 3d with a width smaller than the width of 3c.
It In addition, the pad portion 3b is for pulling out to an external circuit.
Also serves as an electrode pad. 4 and 5 are emitter tips.
Emitter on the silicon substrate 1 between the tip 1a and the insulating film 2.
Si sequentially formed so as to surround the tip 1a
O ₂And an insulating film such as Cr, and a gate electrode such as Cr.

Next, a method of forming the field emission cathode will be described. First, as shown in FIG. 2A, the silicon substrate 1
The region other than the region where the gate and the emitter are formed (region where the pad portion of the anode pattern is formed) is thermally oxidized to form the insulating film 2 having a thickness of about 1.5 μm. next,
As shown in FIG. 2B, Cr is vapor-deposited on the entire surface to form a film thickness 3
The conductive film 3 of about 000Å is formed.

Next, as shown in FIGS. 2C and 2D (FIG. 2D is a plan view of FIG. 2C), the conductive film 3 is etched to form silicon between the insulating films 2. An anode pattern 3a is formed from the substrate 1 to the insulating film 2. At this time, the anode pattern 3a has a pad portion 3b formed on the insulating film 2 and a substantially circular anode portion 3c formed on the silicon substrate 1 between the pad portions 3b and having a width of about 1.5 μm.
And a support portion 3d having a width smaller than the width of the anode portion 3c formed between the anode portion 3c and the pad portion 3b.

Next, as shown in FIG. 3 (e), the silicon substrate 1 between the insulating films 2 is etched using the anode pattern 3a as a mask under the condition that side etching is performed, to directly under the anode portion 3c of the anode pattern 3a. An emitter tip 1a having a sharp uppermost portion separated from the anode portion 3c
To form. At this time, since the support portion 3d of the anode pattern 3a is formed with a pattern that is sufficiently thinner than the anode pattern 3a, as shown in FIG.
a is not formed. The base of the pad portion 3b is SiO ₂
Since it is the insulating film 2, it is not etched.

Then, as shown in FIGS. 3F and 3G, SiO ₂ is formed on the silicon substrate 1 between the emitter tip 1a and the insulating film 2 so as to surround the emitter tip 1a while leaving the anode pattern 3a. , Cr are sequentially deposited to form an insulating film 4 having a thickness of about 1.0 μm and a thickness of 2000 Å
A field emission cathode can be obtained by forming the gate electrode 5 to a certain extent. At this time, the anode pattern 3a
The insulating film 4 and the gate electrode 5 are also formed thereon, but the insulating film 4 and the gate electrode 5 are not formed on the emitter tip 1a because the anode portion 3c of the anode pattern 3a is masked. The gate electrode 5 formed in the portion where the anode pattern 3a is not formed may be formed at substantially the same height so as to surround the emitter tip 1a by appropriately adjusting the film thicknesses of the insulating film 4 and the gate electrode 5. it can.

That is, in this embodiment, the anode pattern 3a is formed into the pad portion 3b formed on the insulating film 2 and the substantially circular shape formed on the silicon substrate 1 (the emitter tip 1a having a sharp tip just below the anode portion 3c). To form the anode part 3c, the anode part 3c and the pad part 3
and a support portion 3d having a width smaller than the width of the anode portion 3c (between the support portion 3d and the emitter tip 1a are not formed), and the silicon substrate 1 is formed by using the anode pattern 3a. Since the etching is performed under the condition that the side etching is appropriately included, it is possible to form the emitter tip 1a having a sharp tip only under the anode portion 3c of the anode pattern 3a. At this time, the emitter tip 1a and the pad portion 3b are arranged apart from each other, but the emitter tip 1a is supported by the support portion 3d integrally formed with the pad portion 3b formed on the insulating film 2. Therefore, it is not necessary to disengage during the process or after mounting.

Moreover, the anode pad 3a is the pad portion 3
b, the support portion 3d, and the anode portion 3c are integrally formed, so that the anode portion 3c that has received the electrons emitted from the emitter tip 1a has a pad portion 3b that is connected to an external circuit via the support portion 3d. Can be drawn as a current from. As described above, in this embodiment, since the anode part 3c of the anode pattern 3a can be arranged right above the emitter tip 1a, the distance between the emitter tip 1a and the anode part 3c serving as the anode electrode can be set to be the same as the conventional planar shape. It can be made extremely shorter than when it was placed in. Therefore, the traveling distance of electrons can be shortened to operate at high speed.

[0025]

According to the present invention, the distance between the emitter tip and the anode electrode can be shortened, the traveling distance of electrons can be shortened, high-speed operation can be performed, and stable and easy formation is possible. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a field emission cathode according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a method for forming a field emission cathode according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a method for forming a field emission cathode according to an embodiment of the present invention.

FIG. 4 is a diagram showing a structure of a conventional field emission cathode.

FIG. 5 is a diagram illustrating a method of forming a conventional field emission cathode.

FIG. 6 is a diagram illustrating a problem of a conventional example.

[Explanation of symbols]

 1 Silicon substrate 1a Emitter tip 2 Insulating film 3 Conductive film 3a Anode pattern 3b Pad part 3c Anode part 3d Support part 4 Insulating film 5 Gate electrode

Claims (2)

[Claims] 1. A method for forming a field emission cathode, in which a sharp pointed portion is formed on a substrate and an electron beam is taken out by field emission from the sharpened portion, in which a conductive film is used as a mask to form an emitter by etching, followed by insulation. A method for forming a field emission cathode, which comprises forming a film and an extraction electrode film and using the conductive film of the mask as an anode. 2. A step of forming a first insulating film (2) on a region of the substrate (1) other than a region where a gate and an emitter are formed, and then a process of forming a conductive film (3) on the entire surface. Then, the conductive film (3) is etched to form a pad portion (3b) on the first insulating film (2), and on the substrate 1 between the pad portions (3b). The pad is formed by forming an anode part (3c) and further forming a support part (3d) having a width smaller than the width of the anode part (3c) between the anode part (3c) and the pad part (3b). A step of forming an anode pattern (3a) consisting of a portion (3b), the support portion (3d) and the anode portion (3c), and then using the anode pattern (3a) as a mask, the first insulating film Predetermined side etching of the substrate (1) between (2) A step of etching under the conditions to enter to form an emitter tip (1a) having an acute uppermost portion immediately below the anode part (3c) of the anode pattern (3a), and then, the first insulating film (2) and the emitter. A step of sequentially forming a second insulating film (4) and a gate electrode (5) on the silicon substrate 1 between the tips (1a), the method for forming a field emission cathode.