JPH04133241A - Field electron emitting element - Google Patents

Abstract

PURPOSE:To lessen dispersion of electric characteristics over a large area, enlarge the current gain, and enhance the power efficiency by forming a conical projection on the surface of a flat base board, and allowing the tip of this projection to protrude from the assumed plane which is bounded by the peripheries of an opening provided in a gate electrode. CONSTITUTION:A conical projection 14 is formed by etching of a Si base board 11 having azimuth of (100) plane, wherein the height is 12000Angstrom and the appex angle in e cross-section is approx. 90deg. An insulative layer 12 shall preferably have a film thickness smaller than this height of projection, for ex. 6000Angstrom , and the DC dielectric breakdown voltage preferably be large, for ex. over 6X10<6>V/cm. Of a gate electrode 13, the conical electrode part 16 is formed in parallel with the wall surface of the projection 14. This electric field electron emitting element thus obtained has an anode current of 3muA with the gate voltage 100V when it is operated under a vacuum of 1X10<-7>Torr, and dispersion of the cathode current on a 3-inch Si base board is less than 10%. The current gain (I6k/I9k ratio) is 100.

Description

[Detailed Description of the Invention] [Industrial Application Field] ] However, the above-mentioned conventional field electron emission device, light-emitting display device, printer head, and electronic device according to the present invention had several problems as described below. ＼ -Threshold voltage for electron emission, current density-voltage-current characteristics, etc.■ The current gain (I*v/I-ratio) is small and the power efficiency is low. When a heel-like process is formed across the whole body, this is the sign.

One of the reasons for this is that the heel-like protrusion is formed by a method such as sputtering or vapor deposition. That is, when viewed from the radiation source, different elevation angles occur depending on the position of the substrate, and the angle of the axis of the field-like protrusion with respect to the substrate surface differs near the center and near the periphery of the substrate. Another reason is that in the etching process for opening the gate electrode, a fluctuation force 5 occurs in the diameter im Ii, and the distance between the tip of the heel-like projection and the gate electrode varies by 1 katak.

Regarding (2), this is because due to the geometric structures of the cathode, gate, and anode, electrons flow more easily from the heel-like protrusion to the gate than from the heel-like protrusion, which is the cathode, to the anode.

SUMMARY OF THE INVENTION Therefore, the present invention is intended to overcome the problems of the prior art described above, and its purpose is to reduce variations in electrical characteristics such as voltage, current density, and threshold voltage over a large area, and to The object of the present invention is to provide a field emission device with a large current gain (I-m/knee* ratio) and high power efficiency.

[Means for Solving the Problems] A field emission device of the present invention comprises a flat substrate, a cone-shaped protrusion formed on the surface of the flat substrate, and an insulating layer formed on the surface of the flat substrate. A field emission device having an insulating layer having an opening in the vicinity of the cone-shaped projection, and a gate electrode formed on the surface of the insulating layer and having an opening in the vicinity of the heel-shaped projection. The tip of the cone-shaped projection has a structure that projects upward from a virtual plane roughly defined by the periphery of the opening of the gate electrode.

[Example] The field emission device of the present invention and the method for manufacturing the same will be explained in more detail based on a practical example. However, the present invention is not limited to the following examples.

(Example 1 of 71) Figures 1 (a) and (b) are for explaining the field electron emission device of the present invention, and are a schematic plan view of the field electron emission device and a schematic diagram along the line A-A'. A cross-sectional view is shown in each case.

This field emission device has a circle on the surface of a single-crystal silicon substrate 11! ! The surface of the silicon substrate except for the cone-shaped projections has an insulating layer 12 made of a silicon dioxide thin film, and the surface of the insulating layer 120 is made of molybdenum (Mo).
) It has a structure with a gate electrode 13 made of a metal thin film, and the protrusion tip 15 of the heel-like protrusion 14 protrudes upward from the virtual plane B-B' roughly defined by the periphery of the opening of the one pole 13. It has a similar structure.

The silicon substrate 11 has a (100) plane orientation, and the carrier concentration is about I x 10"am-".However, in order to lower the resistance, impurities are added to the entire silicon substrate or near the cone-like protrusions to 1xlO"am-" The fm-shaped protrusion 14 is made by etching the silicon substrate 11, and its height is 12,000 mm, and the apex angle of the cross section is about 90°.The insulating layer 22 has a film thickness of The smoke-shaped electrode portion 16 of the gate electrode 13 is preferably smaller than the height of the heel-like protrusion, is 6000A, and has a DC breakdown voltage of 6×10”V/cm or more.
is formed parallel to the wall surface of the heel-like process 14.

The field emission device of this example has approximately 1xlO-'Tor
When operated in a vacuum of r, the anode current is 3μ when the gate voltage is 100V.
It was A. In addition, (1) The variation in cathode current on 3-inch silicon 1& was 10% or less. Also, ■ current gain (I −
b/engine s-ratio) was 100.

(Example 2) Figure M2 explains a second example of the present invention, and is a schematic cross-sectional view of a field emission device formed on the surface of a silicon single crystal substrate. This field emission device has silicon jI on the surface of a first electrode 21 made of a (100) plane n-type silicon single crystal substrate with a carrier temperature of lx10"cm".
A conical cone-shaped protrusion 24 made of a part of the IN crystal substrate and an insulating layer 22 made of a silicon oxide film (SiOtl film) are provided, and the roughness is extremely high! In this structure, a gate electrode 23 made of chromium (Or) is provided on the surface of the gate electrode 22.

The gate electrode 23 has a circular opening at the top of the cone-shaped projection 24, and the tip of the above-water projection 24 projects upward from a virtual plane roughly defined by the periphery of the opening of the gate electrode. The manufacturing method is based on our patent [11 Hei 01-32762
A manufacturing method similar to that described in 1 was used, but
In the manufacturing method, after forming the bird's beak-shaped 5102 thin film and before forming the insulating layer 23, a step of etching 5iOpHii was added to make the cone-shaped protrusion 24 protrude.

The field electron emission device of this example has a Torr of approximately 1×10 Torr.
(1) The variation in cathode current on a 3-inch silicon substrate was less than 10%. In addition, the current gain (Igk ratio) was 100.

(Comparative Example 1) A field emission device having a structure similar to that described in our patent application (Japanese Patent Application No. 02-109203) was fabricated as a prototype, and the variation in electrical characteristics and gain were measured. The following results were obtained. humiliated.

■ ■ Cathode current variation on 3-inch silicon [E
... 10% or less current gain (X ah / engineering ratio) - ... 30 (Comparative Example 2) Field electron emission having a structure similar to the structure described in our patent application (Japanese Patent Application No. 01-327621) When we prototyped a device and measured the variation in electrical characteristics and gain, we obtained the following results.

The field emission device of the present invention was found to be superior when its characteristics were compared using Table 1.

Table 1 ■ Variation in cathode current on 3-inch silicon substrate ... 10% or less ■ Current gain (I-w/engine, relative to) ... 30 (Comparative example 3) Field emission device by Spind et al. When a field emission device with a similar structure was fabricated as a prototype and the variation in electrical characteristics and gain were measured, the following results were obtained.

■ Variation in cathode current on a 3-inch silicon substrate ... ~20% ■ Current gain (1 to 1/k ratio) The reason for this is as follows: I was able to understand this by considering a model. Figure 3 (
This will be explained in detail using a) and (b). Figure 3(a)
is the case of the field emission device of Example 1, and Fig. 3 (
b) is the case of the field emission device of Comparative Example (1).

As can be seen from FIG. 3, the field electron emission device of the present invention (Example 1) has a cone-shaped cathode, compared to the conventional field emission device (Comparative Example 1). Protrusion 34
It can be inferred that the emitted electrons easily reach the anode 35 without being trapped by the gate electrode 33.

(Working report 3) Figures 4 (a) to (f) explain the method for manufacturing the field electron emission device described in Example 1, and show a schematic cross-sectional view of the silicon substrate after the manufacturing process is completed, which is the key point. This is what is shown.

The manufacturing process of the field electron emission device of the present invention will be explained based on FIG. First, the diameter is 3 inches and the thickness is 400 μm (+)
The cone-shaped projections 4 are formed on the surface of the n-type silicon plate 41 by anisotropic etching of silicon using a KOH-based etching solution.
form 4. (FIG. 4(a)) The etching mask contains a silicon dioxide thin film deposited by atmospheric pressure CVD. The composition of the anisotropic etching solution was KOH: IPA: H2 using a 5 μm-sized one.
Using 0 = 1: 2: 8 (wt ratio), the liquid temperature was
The temperature was set to 0°C. By etching for about 60 minutes, the height is 1.
2,000 people, an almost conical cone-shaped process with an apex angle of 90° is produced.

Next, an insulating layer 42 made of a silicon dioxide thin film and a gate electrode 43 made of a Mo thin film are successively deposited on the entire surface of the silicon substrate 41 including the cone-shaped projections by high frequency sputtering. ), the thickness of the insulating layer 42 is about 600 OA, but on the slope of the cone-shaped projection 44 it is slightly thinner, about 5000 OA. This is because the sputtered particles have a directionality perpendicular to the silicon substrate surface. Gate electrode 43
The film thickness is approximately 3,000 people. Next, the gate electrode 43
A photoresist thin film 49 is applied on the surface of the protrusion by a spin code method (FIG. 4(C)). Since the photoresist thin film has low viscosity when applied, the film tends to be thinner at the top of the protrusion. Therefore, the thickness of the photoresist thin film 49 is about 1,500 on the top of the cone-shaped projection 44 and about 13,000 on the flat surface. Next, the photoresist thin film 49 and the gate T4 pole 43 are dry-etched to expose the insulating layer 42 above the cone-shaped projection 44 (FIG. 4(d)). A microwave plasma etching device is used as the dry etching device. , etching gas CFs1
02 mixed gas is used. The beginning of etching is Oe
The photoresist thin film 49 is uniformly ashed from the surface by the gas. After approximately 1,500 photoresists 4WA49 were etched, the sleep protrusions 44 were etched.
A part of the upper gate electrode 43 made of the Mo thin film appears on the surface.

The Mo thin film appearing on the surface is etched by the CF4 gas, and at the same time the photoresist thin film @49 is also etched.By appropriately selecting the CF1102 ratio, the etching speed of the Mo thin film and the photoresist thin film can be made equal. By setting the etching time appropriately, it is possible to obtain an etched cross-sectional shape as shown in FIG. 4(d).
2=30/200, and dry etching was performed for 30 minutes. At this time, the diameter of the electrode opening 47 of the gate electrode 43 was about 16,000. Next, the insulating layer 42 at the opening is etched away using an HF-based etching solution to expose the cone-shaped protrusion 44 (see (e) in the same figure).The HF-based etching solution dissolves the silicon dioxide thin film and removes the Mo thin film and silicon substrate. It is preferable to use an etchant that does not dissolve, such as an HF buffer etching solution.After i&, the photoresist thin film 49 is removed using a stripping solution (FIG. 4(f)).

By the above-described manufacturing method, the cone-like protrusion 44 is approximately 2.0 mm from the virtual plane I roughly defined around the opening of the gate electrode 43.
A field emission device protruding above 000A could be manufactured.

In the method for manufacturing a field emission device according to the present embodiment, the distance between the smoke tip 45 and the heel-shaped electrode portion 46 of the gate electrode is determined by the thickness of the insulating layer 42 formed on the slope of the cone-shaped protrusion 44. Ru. Therefore, i! Evenness of the film thickness of the edge layer 42
If the cost is well controlled, a field emission probe with uniform gate threshold voltage can be obtained.

It should be noted that Ba, which has a small number of working spaces, is placed on the protruding portion of the cone-like protrusion 24.
Forming a dielectric thin film such as O can lower the gate threshold.

These three fruits! Throw it flat! E! Although a silicon substrate was used for H, the present invention is not limited to this.
It is also possible to use other insulating substrates such as crystalline substrates and glass substrates. The same applies to the gate 12 as a pole or as a film.

[Effects of the Invention] The field emission device of the present invention includes a flat substrate, a female-shaped projection formed on the surface of the flat substrate, and an insulating layer formed on the surface of the flat substrate, and the conical projection formed on the surface of the flat substrate. and a gate electrode formed on the surface of the insulating layer and having an opening in the vicinity of the cone-shaped protrusion. Because the tip of the protrusion has a structure that protrudes upward from the virtual plane roughly defined by the periphery of the opening of the gate electrode, the threshold voltage and current of emitted electrons are reduced over a large area. Small variations in electrical characteristics such as density and voltage-current characteristics,
Moreover, it is possible to provide a field emission device with a large gain (i/I-ratio) and high power efficiency.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are a schematic plan view and a schematic cross-sectional view taken along the line AA' of a field emission device according to Example 1 of the present invention. FIG. 2 explains a second embodiment of the present invention, and is a schematic cross-sectional view of a field emission device formed on the surface of a silicon single crystal substrate. FIGS. 3(a) and 3(b) are modeled views of the field electron emission behavior of the field electron emission probe of the present invention and the conventional field electron emission device. FIGS. 4(a) to 4(f) show the field electron emission device of the present invention!
! FIG. FIG. 6 is a cross-sectional view of a conventional field emission device. Substrate Insulating layer Gate electrode cone-shaped protrusion Anode Trajectory of emitted electrons Silicon substrate system Color Edge layer Gate electrode cone-shaped protrusion Tip part Heel-shaped electrode part Electrode opening Photoresist thin film Silicon substrate Insulating layer Gate electrode Female protrusion Applicant: Seiko Epson Agent Co., Ltd. Patent Attorney Kizobe Suzuki

Claims (1)

[Claims] a flat substrate, a cone-shaped protrusion formed on the surface of the flat substrate, an insulating layer formed on the surface of the flat substrate and having an opening near the cone-shaped protrusion, and In a field electron emission device having a gate electrode formed on the surface and having an opening near the cone-shaped projection, the tip of the cone-shaped projection is located near the opening of the gate electrode. A field emission device characterized by having a structure protruding upward from a virtual plane roughly defined by