Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
1999-02-08
2001-11-20
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C445S049000
Reexamination Certificate
active
06319082
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron emission device production method for an electron emission device having an emitter electrode for field electron emission.
2. Description of the Prior Art
Recently, development of display apparatuses has been directed to make the apparatuses thinner. In such a circumstance, special attention is paid to a so-called field emission type display (hereinafter, referred to as FED) constituted by electron emission devices.
In an FED, for each pixel, there is provided an electron emission device in combination with an anode electrode and a fluorescent body arranged to opposite to this electron emission device. A plurality of such pixels are formed in a matrix to constitute a display. In this FED, an electron emitted from the electron emission device is accelerated by an electric field between the electron emission device and the anode electrode so as to strike the fluorescent body. Thus, in the FED, the fluorescent body is excited to emit light to display an image.
In general, the electron emission apparatus is a spindt type electrom emission device. As shown in
FIG. 1
the spindt type electron emission device includes; a cathode electrode
100
, a gate electrode
102
layered on an insulation layer
101
on the cathode electrode
100
, and an emitter electrode
104
having an approximately concial shape formed in an opening
103
formed in the insulation layer
101
and the gate electrode
102
so as to expose the cathode electrode
100
. In this electron emission apparatus, the emitter electrode
104
is formed so that its vertex matches with the center line of the opening
103
. In the FED, a plurality of the spindt type electron emission devices are arranged corresponding to respective pixels.
In the electron emission device having such configuration, a positive potential is applied to the gate electrode
102
, whereas a negative potential is applied to the cathode electrode
100
, so as to generate an electric field between the gate electrode
102
and the cathode electrode
100
. This electric field is applied to the tip end of the emitter electrode
104
, so that an electron is emitted from the tip end of the emitter electrode
104
. As has been described above, this causes the fluorescent body to emit light.
When producing such an electron emission device, firstly, the cathode electrode
100
is formed on a substrate, and then the gate electrode
102
is formed over the insulation layer
101
on the cathode electrode
100
. The aforementioned opening
103
is formed by way of photo-lithographic technique.
This opening
103
is, for example, formed as follows. A mask layer having a plurality of openings is formed on the gate electrode
102
. Etching is carried out on the mask layer together with the gate electrode
102
exposed by these openings, so that the openings are transferred to the gate electrode
102
and the insulation layer
101
. Thus, by transferring the openings formed on the mask layer, it is possible to form an opening
103
communicating with the gate electrode
102
and the insulation layer
101
.
After this, a conductive material is sputtered from various directions onto the gate electrode
102
, so as to form the conical emitter electrode
104
inside the opening
103
. Then, the conductive material sputtered onto the gate electrode
102
is removed, thus obtaining the aforementioned spindt type electron emission device.
In such a spindt type electron emission device, it is possible to effectively emit electrons by concentrating an electric field to the tip end of the emitter electrode
104
. In other words, in the spindt type electron emission device, in order improve the electron emission characteristic, it is necessary to concentrate the electric field at the tip end of the emitter electrode
104
. This is achieved by reducing the dimension of the opening formed in the gate electrode
102
.
However, in the FED using the spindt type electron emission device, it is generally impossible to obtain a uniform electron emission characteristic between pixels. Because the luminance varies depending on respective pisels, it is difficult to display a clear image. Accordingly, in the FED using the spindt type electron emission device, in order to obtain a preferable image, it is necessary to take additional care to provide a uniform electron emission characteristic over the entire screen. This result can be obtained by uniformly forming the openings of the electron emission device constituting the pixels and by assuring to a strictly conical shape for the emitter electrode
104
.
In the production method of the aforementioned spindt type electron emission device, when forming the opening
103
in the gate electrode
102
and the insulation layer
101
, a photo-resist is used as the sacrifice layer. In this case, the photo-resist is partially exposed to light so as to form the opening in the sacrifice layer.
In this method, however, there is an optical limit in the diameter of the opening that can be formed on the photo-resist. That is, the possible diameter is on the order of 0.2 to 0.3 micrometers. Because of this limit of the dimension of the opening
103
formed in the gate electrode
102
, this method cannot produce an electron emission device having a sufficient electron emission characteristic. If the dimension of the opening
103
is too large and the electron emission characteristic is insufficient, it is necessary to apply a great voltage to the gate electrode
102
.
Moreover, U.S. Pat. No. 5,564,959 discloses a method for reducing the dimension of the opening formed in the mask layer. That is, an organic high molecule is used for the mask layer, to which accelerated particles such as ions are radiated so as to form a circular opening with a predetermined density. This method enables the formation of an opening having a diameter of 0.2 micrometers or less;
However, this method cannot form an opening at a predetermined position. In other words the positional accuracy of the opening is extremely low. That is, in this method, two or more openings may be overlapped. In such a case, it is difficult to uniformly form the emitter electrode. According to the method disclosed in this U.S. Pat. No. 5,564,959 it is difficult to produce an electron emission device having a uniform electron emission characteristic over a wide area.
Furthermore, PCT International Publication WO96/06443 discloses another method for reducing the dimension of the opening formed in the mask layer. That is, an insulator having a porous structure is used as the insulation layer, and an emitter electrode is formed within the porous structure of this insulation layer. A gate electrode is then formed on the porous insulation layer. By this method, it is possible to form an opening having a dimension of 0.2 micrometers or less.
In this method, however, the gate electrode is formed by deposition on the porous insulation layer and there is a chance that the conductive material constituting the gate electrode will adhere inside this porous structure. In this case, the electron emission device causes a short-circuit between the conductive material and the emitter electrode. Moreover, the wall of the porous structure may be subjected to etching so as to remove the conductive material adhered to the porous structure. However, it is difficult to completely removed the conductive material by this method to prevent the aforementioned short-circuit.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an electron emission device production method for obtaining a preferable electron emission characteristic with a low voltage and for significantly increasing the positional accuracy of the emitter electrode.
The electron emission device production method according to the present invention includes steps of: forming a conductive layer on an insulation layer on a cathode electrode; forming a first opening in the conductive layer; forming a second opening to communicate with the fi
Hirano Takashi
Okita Masami
Hopper Todd Reed
Kananen Ronald P.
Patel Nimeshkumar D.
Rader Fishman & Grauer
Sony Corporation
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