JPH0850853A - Manufacture of electron emission element - Google Patents

Abstract

PURPOSE:To form a homogeneous cold cathode on a substrate by etching. CONSTITUTION:A plurality of divided metallic layers 35 (aluminum) are made on a substrate. Each divided metallic layer 35 is isolated by a groove G. The groove G has a width enough for functioning as a passage for etchant. Resist layers 32 having circular patterns about 5mum in diameter are made at pitches of 10mum vertically and horizontally. The whole of the substrate is soaked in etchant to perform wet etching. The divided metallic layer 35 consisting of aluminum is removed by etching, but only the section right below each resist layer 32 remains as a conical cold cathode. Since the groove G is made, etchant convects all over the substrate, and roughly homogeneous etching is performed as a whole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electron-emitting device, and more particularly to a method for forming a cold cathode by etching.

[0002]

2. Description of the Related Art With the spread of semiconductor devices, the vacuum tube technology has been forgotten, but in the last few years, the vacuum tube technology has regained attention. This is the development of so-called vacuum micro devices. This vacuum micro device is one in which fine vacuum tubes are integrated on the same substrate by utilizing the semiconductor fine processing technology cultivated in many years of research on semiconductor devices. That is, this element is provided with a cold cathode, an extraction electrode, and an anode, and an electron is extracted from the cold cathode by the extraction electrode and is emitted to the anode. By controlling the voltage applied to the extraction electrode, the amount of electrons emitted from the cold cathode can be controlled.

In a semiconductor device, since electrons move in a solid, the operating speed is governed by the mobility of electrons in the solid. On the other hand, in the vacuum micro device, since electrons move in the vacuum, it can operate at a very high speed as compared with the semiconductor device, and has attracted attention as a charge transport medium utilizing the advantages of the vacuum. Further, along with the research on this vacuum micro device, a cold cathode has been developed and is expected to be applied to a flat display and the like.

As described above, the vacuum micro device is, in principle, the same as the vacuum tube, but the size thereof is so minute that it cannot be compared with the vacuum tube. Further, since the cold cathode needs to have a structure in which electrons are easily emitted from the tip portion, it is usually processed into a cone shape such as a cone.
As a method for forming a large number of such fine cone-shaped cold cathodes, a method of performing an etching process using a photolithography technique or a journal of applied
Third edition of the Journal of Applied Physics
A method using oblique vapor deposition as disclosed in Volume 9 (1968) No. 7, pages 3504 to 3505 is known. However, since the latter method requires high technical strength and know-how, the former method is usually used. To form a cold cathode by the former method, a metal layer to be a material for the cold cathode is formed on a substrate, and a resist layer having a pattern corresponding to the planar shape of the cold cathode is formed on the upper surface of this metal layer. Then, the metal layer may be etched using the resist layer as a mask. For example, if a conical cold cathode is formed, a resist layer having a circular pattern may be formed and etching may be performed.

If a sufficiently sharp tip cannot be obtained by the above-mentioned etching alone, a method of further oxidizing the surface by the anodic oxidation method and then removing the oxide film on the surface to sharpen the surface is proposed. Japanese Patent Application No. 5-259044, and a method of performing electropolishing instead of oxidization by the anodic oxidation method is proposed in Japanese Patent Application No. 6-78029.

[0006]

When the electron-emitting device is used as a display device such as a display, it is necessary to arrange extremely fine cold cathodes on the substrate with high density. For example, when conical cold cathodes having a bottom surface of a circle having a diameter of about 5 μm are arranged vertically and horizontally at a pitch of about 10 μm, tens of thousands to millions of cold cathodes are arranged on one substrate. Will be done. However, as described above, when these substrates are dipped in an etching solution and subjected to etching treatment to form these cold cathodes, the contact conditions with the etching solution are different in each part of the substrate, resulting in a difference in etching rate. Specifically, in the peripheral portion of the substrate, the convection of the etching solution actively occurs, so that the etching rate becomes faster, whereas in the central portion of the substrate, the convection of the etching solution becomes slow and the etching rate tends to become slow. It is in. As a result, the cold cathode formed in the peripheral portion of the substrate becomes a slightly smaller cone-shaped cold cathode due to over-etching, whereas the cold cathode formed in the central portion of the substrate becomes slightly larger due to under-etching. It becomes a conical electrode. Alternatively, under-etching may leave a trapezoidal cross section without forming a cone.

As described above, when many cold cathodes formed on one substrate are not uniform and uneven in size and shape, discharge characteristics are also affected, and they are used for displays. In this case, there arises a problem that uniform display cannot be obtained.

Therefore, an object of the present invention is to provide a method of manufacturing an electron-emitting device capable of forming a uniform cold cathode on a substrate by etching.

[0009]

[Means for Solving the Problems]

(1) A first aspect of the present invention is to manufacture an electron-emitting device, which comprises a cold cathode and an extraction electrode, extracts electrons from the cold cathode by the extraction electrode and emits the electrons to an anode, on a substrate. A step of forming a first conductive layer for wiring to the cold cathode, and a step of forming a second conductive layer made of a material forming the cold cathode on the first conductive layer. Forming a resist layer having a pattern corresponding to the planar shape of the cold cathode to be formed on the second conductive layer at the position where each cold cathode is arranged, and exposing the substrate to a predetermined etching solution. Manufacturing an electron-emitting device in which a cold cathode is formed by immersing and etching the second conductive layer using the resist layer as a mask to form a cone-shaped cold cathode in a portion covered by the resist layer. In the method, the second conductive layer is planar It is configured by a plurality of divided conductive layers that are arranged in a uniform manner, and a groove portion having a width that functions as a channel of an etching solution is secured between adjacent divided conductive layers.

(2) A second aspect of the present invention is the above-mentioned first aspect.
In the method of manufacturing an electron-emitting device according to the above aspect, an opening for introducing an etching solution is further provided in the central portion of each divided conductive layer.

[0011]

[Operation] In the method of manufacturing an electron-emitting device according to the present invention,
The second conductive layer is composed of a plurality of divided conductive layers arranged in a plane, and a groove portion having a width that functions as an etching liquid flow path is secured between the adjacent divided conductive layers. To be done. Therefore, when the substrate is dipped in the etching liquid, convection of the etching liquid is likely to occur along the groove portion, and convection of the etching liquid is uniformly generated over the entire substrate. Therefore, there is no difference in etching rate between the peripheral portion and the central portion of the substrate, and it becomes possible to form a uniform cold cathode on the entire surface of the substrate.

Further, if an opening for introducing an etching solution is further provided in the central portion of each divided conductive layer, the peripheral portion and the central portion of one divided conductive layer can be separated from each other by the etching solution. The difference in contact state is reduced, and a uniform cold cathode can be formed.

[0013]

The present invention will be described below based on illustrated embodiments. First, the structure of a conventional general vacuum micro device will be described. FIG. 1 is a cross-sectional view showing a general structure of a vacuum micro device for driving a flat panel display. In this vacuum micro device, a large number of cold cathodes are two-dimensionally arranged on the substrate, but here, for convenience of description, only one cold cathode and its peripheral structure are shown, and the structure of each part is also shown. I will draw ignoring the actual size ratio.

The glass substrate 1 has a sufficient thickness to support this element, and the wiring layer 2 is formed thereon. A cold cathode 3 and an insulating layer 4 are formed on the wiring layer 2, and an extraction electrode 5 is formed on the insulating layer 4. The wiring layer 2 is for supplying a voltage to the cold cathode 3, and is made of a metal thin film of chromium, tantalum, or the like.
It is configured by being formed with a thickness of about 5 μm. The cold cathode 3 formed on this is, in this embodiment,
It is a conical electrode made of aluminum and having a height of about 2.0 μm. The insulating layer 4 is made of SiO ₂ , Al ₂
The extraction electrode 5 is a layer obtained by depositing O ₅ or the like to a thickness of about 2.0 μm, and the extraction electrode 5 is formed by forming a metal thin film such as aluminum or tantalum to a thickness of about 0.1 to 0.5 μm. Is. The extraction electrode 5 is located at almost the same height as the height of the tip of the cold cathode 3.

On the other hand, the anode 7 and the phosphor layer 8 are formed on the lower surface of the other glass substrate 6. Anode 7
Is a transparent conductive film of ITO, ZnO: Al, etc.
The phosphor layer 8 is formed to have a thickness of about 1.0 μm, and the phosphor layer 8 is made of a phosphor such as ZnO: Zn to have a thickness of 10 μm.
A layer of about m is formed. The structure formed on the upper surface of the glass substrate 1 is the electron-emitting device 10 to which the present invention is applied. On the other hand, the structure formed on the lower surface of the glass substrate 6 is, so to speak, also an electron accepting element 20, and is arranged so as to face the electron emitting element 10 as shown in FIG. The void is kept in a vacuum.

The vacuum micro device having such a structure operates as a vacuum tube. That is, the cold cathode 3 is a cathode, the anode 7 is an anode, the extraction electrode 5 is a grid,
As a result, if a predetermined voltage is applied to each electrode, electrons can be extracted from the cold cathode 3 and emitted to the anode 7,
The amount of emitted electrons can be controlled by the voltage applied to the extraction electrode 5. The phosphor layer 8 emits light in response to collision of electrons toward the anode 7. This light emission is observed from above the drawing through the anode 7 and the glass substrate 6.

Now, in manufacturing the vacuum micro device having such a structure, the most difficult process is to form the conical cold cathode 3 on the electron emitting device 10 side. In FIG. 1, only one cold cathode and its peripheral structure are shown for convenience of explanation, but in reality, as shown in FIG. 2, a large number of such structures are arranged vertically and horizontally, It is necessary to make the size and shape of each cold cathode 3 uniform. If there are variations in the size and shape of the plurality of cold cathodes 3 arranged vertically and horizontally, the display screen becomes uneven.

As a method for forming the cold cathode 3,
An etching method using a photolithography technique is generally used. Here, this conventional general etching method will be described. First, as shown in the side sectional view of FIG. 3, a wiring layer 2 made of a metal such as chromium is formed on a glass substrate 1 by a sputtering method, a vacuum deposition method or the like to have a thickness of 0.1 to 0.5 μm. It is formed with a film thickness of about. Then, the metal layer 31 is formed on the wiring layer 2. This metal layer 31 is made of a material that constitutes the cold cathode 3, and in this embodiment, an aluminum layer having a thickness of about 2 μm is formed by a sputtering method, a vacuum evaporation method or the like. Furthermore,
A resist layer 32 having a pattern corresponding to the planar shape of the cold cathode 3 to be formed is formed on the upper surface of the metal layer 31. In this example, since the conical cold cathode 3 is formed, the planar shape of the cold cathode projected onto the substrate surface of the glass substrate 1 is a circle. Therefore, the resist layer 32 is formed so as to have a circular pattern when viewed from above. More specifically, by coating a photosensitive resist on the metal layer 31, arranging a mask having a circular pattern on the metal layer 31 for exposure, and performing development processing, a circular pattern as shown in FIG. 3 is obtained. 32 (FIG. 3 is a side sectional view, but when viewed from above, it becomes a circle having a diameter D). However, for convenience of description, the case of forming a single cold cathode is illustrated here. However, in reality, since a large number of two-dimensionally arranged cold cathodes are simultaneously formed, the resist layer A large number of 32 will be arranged accordingly.

After the resist layer 32 having a predetermined pattern is formed in this manner, the entire glass substrate 1 is immersed in the etching solution. Here, MR-ALE (manufactured by Hishie Chemical Co., Ltd.) is used as the isotropic etching liquid for aluminum. In such isotropic etching,
Etching progresses in both the vertical and horizontal directions of the figure using the resist layer 32 as a mask, and as a result, the conical cold cathode 3 as shown in the side sectional view of FIG. 4 is obtained immediately below the resist layer 32. become. After that, if the resist layer 32 is peeled off (or etching may be continued until it is peeled off naturally), as shown in FIG. 5, a cone made of aluminum is formed on the wiring layer 2 made of chromium. The cold cathode 3 is formed.

Etching is carried out by setting the thickness t of the aluminum metal layer 31 shown in FIG. 3 to 2 μm and the diameter D of the resist layer 32 having a circular pattern D to 5 μm, and etching is performed until just before the resist layer 32 is peeled off. As shown in FIG. 5, a conical cold cathode 3 having a diameter d of about 2 μm and a radius of curvature of about 50 nm at the tip can be formed. If necessary, a treatment for further sharpening the tip portion (a method for forming and removing an oxide film proposed in Japanese Patent Application No. 5-259044, and Japanese Patent Application No. 6-780).
The method of performing electropolishing proposed in the specification No. 29) is performed.

By the way, in practice, since it is necessary to form a large number of cold cathodes 3 on the glass substrate 1, the top view at the stage of forming the resist layer 32 shown in FIG.
It becomes something like FIG. It can be seen that a large number of resist layers 32 indicated by black circles are arranged on the metal layer 31 made of aluminum. FIG. 7 is a partially enlarged view thereof. In this example, a circular resist layer 32 having a diameter D = 5 μm
Are arranged vertically and horizontally with a pitch of 10 μm. Figure 6
As shown in, in this embodiment, a square glass substrate 1 having a side of 3600 μm is used, and the peripheral edge of the substrate is
A circular resist layer 32 is tightly arranged inside with a gap of about 10 μm. In other words, in this embodiment, an enormous number of circular resist layers 32 of approximately 360 × 360 are formed vertically and horizontally (in FIG. 6, the number of resist layers 32 is not correct for convenience of illustration). As a result of the etching process, the same number of cold cathodes 3 are formed.

However, as described above, when the cold cathode 3 is formed by immersing the entire substrate as shown in FIG. 6 in an etching solution to perform the etching process, the contact condition with the etching solution is different in each part of the substrate. However, there is a difference in etching rate. That is, in the peripheral portion of the substrate, the convection of the etching solution actively occurs, so that the etching rate becomes faster, whereas in the central portion of the substrate, the convection of the etching solution becomes slow and the etching rate tends to become slow. As a result, the cold cathode formed in the peripheral portion of the substrate becomes a rather small cone-shaped cold cathode by over-etching, while the cold cathode formed in the central portion of the substrate becomes slightly larger by under-etching. It becomes a conical electrode. Or by under etching,
Sometimes the cross section remains trapezoidal without becoming a cone. After all, even though the cold cathode 3 is formed on the same one glass substrate 1, the size and shape of each portion will be uneven, and when used for a display or the like, a uniform display is obtained. Will not be obtained.

The present invention solves such a problem by the following method. That is, instead of forming one metal layer 31 as shown in FIG. 6, a plurality of divided metal layers 35 as shown in FIG. 8 are formed. In the embodiment shown here, each split metal layer 35 has 6
It has a square shape of 00 μm × 600 μm and is arranged two-dimensionally. Moreover, a groove portion G having a width that functions as a flow path for the etching liquid is secured between the adjacent divided metal layers 35. In this embodiment, the groove portion G has a width of 150 μm. The resist layer 32 is
It is to be formed on the upper surface of the divided metal layer 35 formed in this way (in order to avoid complication of the drawing, the resist layer 32 is shown only partially in FIG. 8). FIG. 9 is a side sectional view of the entire substrate shown in FIG. 8 taken along the cutting line XX. The split metal layer 35 is a layer made of aluminum and having a thickness of about 2 μm, and is in a state of being physically separated from each other by the groove portion G. To form the divided metal layer 35 having such a pattern, for example, the metal layer 31 formed on the entire surface of the substrate may be etched using a photolithography method to form the groove portion G.

In this way, as shown in FIG. 8, when the resist layer 32 having a circular pattern can be formed on each of the divided metal layers 35, the entire glass substrate 1 is immersed in an etching solution as in the conventional method. Isotropic etching with respect to aluminum may be performed. By this etching, the conical cold cathodes 3 are formed immediately below the resist layer 32. However, unlike the etching for the conventional structure as shown in FIG. 6, the structure according to the present invention shown in FIG. 8 has a width (in this embodiment, a width that functions as a flow path of the etching liquid) in the vertical and horizontal directions on the substrate. , 150 μm), the etching solution is convected to the entire substrate along the groove G. Therefore, there is no difference in etching rate between the peripheral portion and the central portion of the substrate as in the conventional case, and the etching can be uniformly advanced over the entire surface of the substrate.
As a result, it is possible to form uniform cold cathodes having substantially the same shape and size over the entire surface of the substrate.

Of course, 600 μm × 600 shown in FIG.
Considering the etching conditions for one segmented metal layer 35 having a size of μm, again, since the convection of the etching solution is performed more actively in the peripheral portion than in the central portion, the etching rate in the peripheral portion is higher. The phenomenon of high value is still occurring. However, the difference in the etching rate is smaller than the conventional difference over the entire surface of the substrate, and can be suppressed to a practically negligible level. In addition, when it is desired to reduce even the difference in etching rate for such one divided metal layer 35, as shown in the top view of FIG.
An opening 36 may be formed in the central portion of each divided metal layer 35. FIG. 11 is a side sectional view of a part of the substrate shown in FIG. 10 taken along the cutting line YY. The opening 36 thus formed has a function of introducing an etching liquid, and the etching liquid is formed on both sides of the peripheral portion (groove G) and the central portion (opening 36) of one divided metal layer 35. The etching rate becomes substantially equal in the peripheral portion and the central portion.

By the way, the manufacturing method according to the present invention has one disadvantage. As can be seen by comparing the structure according to the present invention shown in FIG. 8 with the conventional structure shown in FIG. 6, when the present invention is applied, the cold cathode cannot be formed in the region of the groove portion G. . Arrangement pitch of cold cathode is 10μ
Considering that the width of the groove G is about 150 μm, it is possible to obtain
About the number of cold cathodes will be thinned out. Therefore, a cold cathode is formed by the structure shown in FIG.
When an electron-emitting device for a display is manufactured by forming necessary insulating layers and extraction electrodes, this device is a device in which the arrangement of the cold cathodes is chipped in the region of the groove portion G. For example, when electrons are emitted from the cold cathode to display high brightness on the entire display surface, a grid line corresponding to the groove G appears.

However, such a lack of arrangement of the cold cathodes causes no problem in practical use. This is because one pixel, which is the “minimum unit of display” when applied to a display or the like, is generally composed of a plurality of cold cathodes. For example, in FIG. 8, if one pixel is formed by a large number of cold cathodes (approximately 60 × 60 in this embodiment) formed on one divided metal layer 35, 600 μm × The area of 600 μm corresponds to one pixel, and the groove portion G corresponds to the boundary line between pixels. Therefore, even if the cold cathode is missing in the groove portion G, no display problem occurs. Further, even when the one divided metal layer 35 is used so as to correspond to the display area of one character, the practical problem is solved. In this case, the groove portion G corresponds to the boundary line between characters.

The present invention has been described above based on the illustrated embodiments, but the present invention is not limited to these embodiments and can be implemented in various modes other than this. In particular, the dimensions shown in the above-mentioned examples are presented by reference to the numerical values actually experimented by the inventor of the present application, and the basic idea of the present invention is not limited by such numerical values. is not. Problems such as how large one divided metal layer should be and how wide the groove G should be can be appropriately set in consideration of the application.

[0029]

As described above, according to the method of manufacturing an electron-emitting device according to the present invention, when the cold cathode is formed by etching, the metal layer to be etched is divided by the groove portion, and the etching solution is Since it is arranged over the entire substrate, it becomes possible to form a uniform cold cathode on the substrate.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a conventional general vertical vacuum micro device.

FIG. 2 is a perspective view showing a state in which vacuum micro devices having the structure shown in FIG. 1 are arranged on a plane.

FIG. 3 is a side sectional view showing a first step of a conventional general process of forming a cold cathode by using etching.

FIG. 4 is a side sectional view showing a second step of a conventional general process of forming a cold cathode using etching.

FIG. 5 is a side sectional view showing a third step of a conventional general process of forming a cold cathode using etching.

FIG. 6 is a top view showing a state in which a large number of resist layers 32 having a circular pattern are formed on a metal layer 31 to be etched in a conventional method for forming a cold cathode.

7 is a partially enlarged view of FIG.

FIG. 8 is a top view showing a state in which a large number of resist layers 32 having a circular pattern are formed on the divided metal layer 35 to be etched in the method for forming a cold cathode according to the present invention.

9 is a side sectional view of the structure shown in FIG. 8 taken along section line XX.

FIG. 10 is a plan view showing a method of forming a cold cathode according to the present invention, in which a split metal layer 35 to be etched is further provided with an opening 36.
It is a top view which shows the state which formed.

11 is a side sectional view of the structure shown in FIG. 10 taken along the section line YY.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass substrate 2 ... Wiring layer 3 ... Cold cathode 4 ... Insulating layer 5 ... Extraction electrode 6 ... Glass substrate 7 ... Anode 8 ... Phosphor layer 10 ... Electron emitting element 20 ... Electron receiving element 31 ... Metal layer 32 ... Resist layer 35 ... Dividing metal layer 36 ... Opening G ... Groove

Claims (2)

[Claims] 1. A wiring to a cold cathode is provided on a substrate to manufacture an electron-emitting device comprising a cold cathode and an extraction electrode, wherein the extraction electrode extracts electrons from the cold cathode and emits the electrons to the anode. A step of forming a first conductive layer for performing, a step of forming a second conductive layer made of a material to form a cold cathode on the first conductive layer, and the second conductive layer Above, a step of forming a resist layer having a pattern corresponding to the planar shape of the cold cathode to be formed, at the position of arrangement of each cold cathode, the substrate is immersed in a predetermined etching solution, the resist layer Etching the second conductive layer as a mask to form a cone-shaped cold cathode in the portion covered by the resist layer; and Second conductive layer Is composed of a plurality of divided conductive layers arranged in a plane, and secures a groove portion having a width that functions as a channel of an etching liquid between adjacent divided conductive layers. Method of manufacturing electron-emitting device. 2. The method of manufacturing an electron-emitting device according to claim 1, wherein an opening for introducing an etching solution is further provided in the central portion of each divided conductive layer. Production method.