JP2956565B2 - Method of manufacturing field emission cold cathode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a cold cathode serving as an electron emission source, and more particularly to a method of manufacturing a field emission cold cathode emitting electrons from a sharp tip.

[0002]

2. Description of the Related Art An array of cold cathodes arranged in the form of an array of minute conical emitters and minute cold cathodes formed in the immediate vicinity of the emitters and configured with a gate layer having a function of extracting current from the emitters and having a current control function. Cathodes have been proposed (Journal of Applied Physi
cs, Vol. 39, no. 7, pp. 3504, 19
68). The Spindt-type cold cathode has advantages that a higher current density can be obtained compared to a hot cathode, and the velocity distribution of emitted electrons is small. In addition, current noise is smaller than that of a single field emission emitter, the device operates at a low voltage of several tens to 200 V, and the electron microscope operates at a degree of vacuum of about 10 ⁻¹⁰ Torr. Depending on the emitter, 10
It is said that a sealed glass tube of ^-6 to 10 ^-8 Torr also operates.

FIG. 5 shows a prior art Spint.
FIG. 2 shows a cross-sectional view of a structure of a main part of a dt) type cold cathode. A small conical emitter 102 having a height of about 1 μm is formed on a conductive substrate 101 by a vacuum evaporation method.
2, a gate layer 103 and an insulating layer 104 are formed. The substrate 101 and the emitter 102 are electrically connected. Between the substrate 101 (and the emitter 102) and the gate layer 103, the gate
V DC voltage is applied. Since the distance between the substrate 101 and the gate layer 103 is as small as about 1 μm and the opening diameter of the gate layer is about 1 μm, and the tip of the emitter 102 is extremely sharp, a strong electric field is applied to the tip of the emitter 102.
When the electric field becomes 2-5 × 10 ⁷ V / cm or more, electrons are emitted from the tip of the emitter 102, and a current of 0.1 to several tens μA is obtained for each emitter. By arranging a plurality of minute cold cathodes having such a structure in an array on the substrate 101, a planar cathode emitting a large current is formed.

A method for manufacturing a Spindt-type cold cathode will be described with reference to FIG. An insulating layer 62 such as silicon dioxide (SiO ₂ ) and a low-resistance gate layer 63 serving as a gate electrode are formed on a conductive substrate 61 such as silicon also serving as a cathode electrode (FIG. 6A). Next, a cavity 65 patterned on the resist 64 by photolithography or the like.
(FIG. 6B) is transferred to the gate layer 63 and the insulating layer 62 by etching (FIG. 6C).

Next, a sacrificial layer 66 for later lift-off is formed on the gate layer 63 and on the edge of the cavity 65.
While rotating the substrate 61, aluminum oxide or the like is deposited from an oblique direction (FIG. 6D). Thereafter, in order to form an emitter, an emitter material 67 such as molybdenum is deposited vertically on the substrate (FIG. 6E). At this time, as the deposition proceeds, the opening of the cavity gradually narrows, so that a conical emitter 68 is formed on the bottom surface of the cavity. Finally, the sacrificial layer 66 is etched to remove an unnecessary film on the surface, thereby exposing the emitter 68 (FIG. 6F).

[0006]

In the field emission cold cathode,
As described above, a voltage of 100 V is applied between the electrodes at intervals of about 1 μm.
In order to operate by applying a voltage of the order of magnitude, insulation between the gate layer and the emitter is an important characteristic. If the insulation between the gate and the emitter is poor, the operation will not be stable and the life will be affected.

In the conventional manufacturing method, a substantially conical emitter electrode is formed from directly above by vacuum evaporation. However, not all of the deposited particles are deposited as an emitter electrode, and the wraparound or the like also causes the insulation layer side surface in the cavity to be formed. A small amount of emitter material will adhere, thereby degrading the insulation properties between the gate layer and the emitter. In addition, Japanese Unexamined Patent Publication No.
89651 discloses a technique for forming an emitter electrode from various materials by a sputtering method. However, in the case of a sputtering method, the degree of vacuum is lower than that of a vacuum evaporation method, and the influence of scattering of vapor-deposited particles by gas molecules is reduced. Due to the large size, the adhesion of the emitter material to the side surface of the insulating layer due to the wraparound increases, and the insulating characteristics are greatly deteriorated. This effect causes a remarkable deterioration of insulating characteristics, particularly in a cathode having a structure in which a large number of emitters are arranged in parallel, and may not operate.

Japanese Patent Application Laid-Open No. 6-96664 discloses a method of manufacturing a Spindt-type cold cathode. When a sacrificial layer is formed by oblique deposition as shown in FIG. A sacrificial layer is deposited only on a small part of the side of the insulating layer. When evaporation is performed thereafter, the emitter material that has wrapped around does not adhere to the side of the insulating layer covered by the sacrificial layer, but adheres to most of the other sides of the insulating layer. No effect can be expected.

[0009]

According to the present invention, a protective film is formed on the entire side surface of an insulating layer before vapor deposition of an emitter material, so that the emitter material which wraps around during the subsequent vapor deposition is deposited on the protective film. Then, after the emitter is formed, the film is peeled off to remove deposits together with the protective film.

That is, the present invention provides a process for forming an insulating layer and a conductive gate layer on a conductive substrate or a substrate having a conductive layer deposited on an insulating material; Forming a cavity for forming an emitter electrode in the cavity, forming a sacrificial layer overhanging the gate layer and inside the cavity, and forming an emitter electrode in the cavity by depositing an emitter electrode material. Removing a sacrificial layer to lift off excess emitter electrode material, wherein a protective film is formed on the entire side surface of the insulating layer surrounding the emitter electrode before depositing the emitter electrode material. After the film is formed and the material for the emitter electrode is deposited, a step of removing the protective film is provided.

When forming the sacrificial layer, while rotating the substrate around the vertical axis, the substrate is substantially tan-1 (D
g / (tg + ti)), and the sacrificial layer material deposited on the entire side surface of the insulating layer in the cavity can be used as the protective film. Further, after forming the protective film by CVD, the protective film deposited on the portion of the substrate where the emitter electrode is to be formed may be removed and left only on the side surface of the insulating layer. Alternatively, a protective film is deposited by vacuum evaporation or sputtering, and when the protective film deposited on the portion of the substrate where the emitter electrode is formed is removed by sputter etching, the protective film is scattered to protect the film deposited on the entire side surface of the insulating layer in the cavity. It may be a film.

Since the cold cathode can be manufactured without the side surface of the insulating layer being contaminated by the conductive emitter material, the insulation resistance between the emitter and the gate does not deteriorate and the dielectric strength does not deteriorate. Therefore, the gate current during operation can be reduced, and stable operation can be achieved. Further, a stable operation of an element in which a large number of emitters are arrayed is enabled, and the emission current can be increased.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a configuration and a process of a field emission cold cathode according to a first embodiment of the present invention. FIG.
(A) As shown in FIG.
(Thickness t _i = about 0.8 μm), gate layer 3 (thickness t _g =
A microcavity 4 (diameter D _g = about 1 μm) is formed in the gate layer 3 and the insulating layer 2 by photolithography and etching. Insulating layer 2, gate layer 3
Are, for example, silicon dioxide and tungsten, respectively.

Subsequently, a sacrificial layer 5 is formed. In the film formation, aluminum is deposited while rotating the substrate 1 about an axis perpendicular thereto. At this time, an angle tan ^-1 (D _g / (t _g + t _i )) formed on the gate layer 3 and the entire side surface of the insulating layer in the cavity 4 so that the sacrificial layer 5 also serves as a protective film. The deposition is performed at about 45 degrees from the axis (Fig. 1).
(B)). As a result, a continuous aluminum layer from the gate layer 3 to the side surface of the insulating layer in the cavity 4 is formed.

Normally, the diameter D _{g of the} cavity 4 is 0.2 to 2 μm.
On the order, the emitter height = t _i + t _g is 0 the D _g.
It is set to 8 to 2 times. Therefore, the optimal tan ^-1 (D _g
/ (T _g + t _i )) is in the range of 25 to 50 degrees. Typically, about 45 degrees is desired.

Thereafter, while rotating the substrate 1 about an axis perpendicular to the substrate 1, an emitter 7 is formed by molybdenum vapor deposition from directly above the substrate 1. In the meantime, the emitter material particles 8 that have wrapped around due to scattering by residual gas in vacuum or the like adhere to the sacrificial layer (protective film) 5 on the side surface of the insulating layer (FIG. 1).
(C)). Finally, by dissolving the sacrificial layer 5 with phosphoric acid to remove the unnecessary emitter material 6 and the emitter material particles 8, a side surface of the insulating layer free from contamination is realized (FIG. 1D).

In addition, besides molybdenum, gold, platinum, rhodium, etc., besides molybdenum, tungsten silicide, molybdenum, polycrystalline silicon, etc., besides tungsten, besides molybdenum, and silicon nitride, besides silicon dioxide, besides silicon dioxide. As the sacrificial layer, aluminum oxide, silicon nitride, nickel or the like can be used in addition to aluminum. In addition, a substrate obtained by depositing a conductive layer on an insulating material can be used as the substrate. In this case, it is not necessary to add a special process for forming and removing the protective film.
The purpose is achieved by forming the sacrificial layer and etching the sacrificial layer in FIG.

FIG. 2 shows the structure and process of a field emission cold cathode according to a second embodiment of the present invention. In FIG.
1 denote the same components as in FIG. 1, and the materials and dimensions of each component are the same as those in the first embodiment shown in FIG. As shown in FIG. 2, an insulating layer 2, a gate layer 3, and aluminum serving as a sacrifice layer 9 are laminated, and a minute cavity 4 is formed in the sacrifice layer 9, the gate layer 3, and the insulating layer 2 (FIG. 2A). ). Subsequently, the protective film material 10 is formed by CVD.
Is formed on the sacrificial layer 9 and on the surface of the cavity 4 (FIG. 2B).

Thereafter, reactive ion etching (RI) using carbon tetrachloride gas is performed so that the bottom surface of the cavity 4 appears.
E), the protective film 11 is formed only on the side surfaces of the insulating layer 2, the gate layer 3, and the sacrificial layer 9.
Remain (FIG. 2 (c)). The steps from emitter formation are shown in FIG.
This is the same as the first embodiment shown in (c) and (d).

Although aluminum has been described as the sacrificial layer and the protective film material, aluminum oxide, silicon nitride, or a combination thereof can also be used by changing the gas introduced during CVD or RIE.

FIG. 3 shows a structure and a process of a field emission cold cathode according to a third embodiment of the present invention. The process up to the formation of the cavity 4 is the same as that of the second embodiment shown in FIG. Subsequently, the side surface of the insulating layer is etched with hydrofluoric acid to form a shape in which the gate layer protrudes as shown in the figure (FIG. 3A). Thereafter, a positive type resist 12 is applied so as to enter the cavity 4 (FIG. 3B), and the resist 12 is left only in a portion which becomes negative at the time of exposure by pre-baking, exposure from just above the substrate, and development. The protective film 13 is formed (FIG. 3C). The steps from the formation of the emitter (FIG. 3D) to the removal of the sacrificial layer are shown in FIG.
This is the same as the first embodiment shown in (c) and (d).
Finally, by removing the protective film 13 with a stripper, a side surface of the insulating layer without contamination is realized (FIG. 3E).

FIG. 4 shows the structure and process of a field emission cold cathode according to a fourth embodiment of the present invention. The process up to the etching of the side surface of the insulating layer is the same as that of the third embodiment shown in FIG. Further, a protective film material (aluminum) 14 is applied to the substrate 1.
And vapor deposition from the vertical direction (FIG. 4A). Thereafter, sputter etching is performed using argon ions. The protective film material 14 on the bottom surface of the sputtered cavity 4 is removed and adheres to the side surface of the insulating layer to form a protective film 15 (FIG. 4).
(C)). Steps after the formation of the emitter are shown in FIG.
This is the same as the first embodiment shown in FIG.

[0023]

As described above, according to the present invention,
Adhesion of the emitter material to the side surface of the insulating layer can be prevented, and a cold cathode can be manufactured without deteriorating the insulating characteristics. As a result, discharge and leakage current, particularly when the emitters are arrayed, can be reduced, so that the emission current can be increased and the yield can be improved.

Further, even when the emitter electrode is formed by a sputtering method or the like, it is possible to prevent insulation characteristics from deteriorating due to wraparound. It becomes easy to expand the range.

[Brief description of the drawings]

FIGS. 1 (a) to 1 (d) are diagrams for explaining a manufacturing process of a field emission cold cathode according to a first embodiment of the present invention.

FIGS. 2A to 2C are diagrams illustrating a manufacturing process of a field emission cold cathode according to a second embodiment of the present invention.

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

FIGS. 4A to 4C are diagrams illustrating a manufacturing process of a field emission cold cathode according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a main part of a Spindt-type cold cathode.

FIGS. 6 (a) to 6 (f) are diagrams for explaining a manufacturing process of a Spindt-type cold cathode disclosed in JP-A-6-96664.

[Explanation of symbols]

 Reference Signs List 1,61,101 substrate 2,62,104 insulating layer 3,63,103 gate layer 4,65 cavity 5 sacrificial layer (protective film) 6,67 emitter material 7,68 emitter 8 emitter material particles 9,66 sacrificial layer 10 , 14 Protective film material 11, 13, 15 Protective film 12, 64 Resist

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01J 9/02 JICST file (JOIS)

Claims (7)

(57) [Claims] 1. A step of forming an insulating layer and a conductive gate layer on a conductive substrate or a substrate having a conductive layer deposited on an insulating material, and forming an emitter electrode on the insulating layer and the conductive gate layer. Forming a cavity for the gate layer,
Forming a sacrificial layer in the portion, and forming an emitter electrode in the cavity by depositing an emitter electrode material, and then removing off the sacrificial layer to lift off excess emitter electrode material. the method of manufacturing a cathode, before depositing the emitter electrode material, et
A method of manufacturing a field emission cold cathode, comprising: forming a protective film on the entire side surface of an insulating layer inside a cavity for forming a mitter electrode , removing the protective film after depositing a material for the emitter electrode, . 2. When forming the sacrificial layer by a vacuum deposition method, while rotating the substrate around an axis perpendicular to the substrate,
Assuming that the cavity opening diameter is Dg and the thicknesses of the gate layer and the insulating layer are tg and ti, respectively, tan ^-1 (Dg
/ (Tg + ti)) depositing a sacrificial layer material and a composed angles, according to claim 1, wherein utilizing a sacrificial layer material <br/> deposited on the insulating layer side front surface of the cavity as a protective film Manufacturing method of field emission cold cathode. 3. A method for manufacturing a field emission cold cathode according to claim 2, wherein said sacrificial layer material is continuously deposited from the surface of the gate layer to the side of the insulating layer inside the cavity for forming the emitter electrode. 4. The method according to claim 1, wherein after forming the protective film by CVD, the protective film deposited on a portion of the substrate where an emitter electrode is to be formed is removed by sputter etching or anisotropic dry etching. Item 2. A method for producing a field emission cold cathode according to Item 1. 5. An emitter electrode of a substrate is formed by applying a positive photoresist as the protective film on the sacrificial layer and on the surface of the cavity for forming the emitter electrode, and exposing it using an opening in the gate layer. 2. The method according to claim 1, wherein the protective film deposited on the portion is removed by development. Wherein said protective layer is to be formed an emitter electrode of the substrate a protective film material by vacuum deposition or sputtering
Deposited portion, said insulating layer side surface of the cavity by the protective film material are removed by sputter etching
2. The method for producing a field emission cold cathode according to claim 1, wherein the film is a film to which a protective film material is adhered . 7. The method according to claim 2, wherein the angle is in a range of 25 to 50 degrees.