JP3168795B2 - Display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device using a field emission device known as a cold cathode.

[0002]

2. Description of the Related Art An electric field applied to a metal or semiconductor surface is 10
^At about ⁹ [V / m], the tunnel effect causes electrons to pass through the barrier and emit electrons in a vacuum even at room temperature. This is called field emission,
A cathode that emits electrons according to such a principle is called a field emission element FEC (Field Emission Cathode). In recent years, it has become possible to make a large number of micron-sized field emission devices simultaneously by making full use of semiconductor processing technology to create a surface emission type field emission cathode. Placed in a shape,
Techniques have been developed for irradiating the phosphor screen with electrons emitted for each block to adapt to flat display devices and various electronic devices.

One of the methods for manufacturing the above-mentioned field emission device is a rotary oblique deposition method developed by Spindt (US Pat. No. 37).
89471), and another method is based on a selective etching method for a silicon single crystal plate. The former has a feature that the cathode chip material can be almost freely selected, and the latter has a feature that the current semiconductor fine processing can be applied as it is.

Hereinafter, an outline of a method of manufacturing an FEC corresponding to the SPINDT method (Japanese Patent Application Laid-Open No. 1-154426) will be briefly described with reference to FIG. First, as shown in FIG. 6A, a cathode electrode layer 101 is formed on a substrate 100 such as glass by evaporation, and silicon is further laminated thereon to form a resistance layer 102.
Further, an insulating layer 103 is formed of silicon oxide. Further, a conductor is deposited thereon to form the gate electrode layer 104. Such a laminated substrate has a photoresist layer 1 on a gate electrode layer on its upper surface.
After the application of 11, the patterning is performed using a mask 112 except for the region where the cold emitter is to be formed, and the resist layer is irradiated with ultraviolet rays to remove the resist layer 111 with a dedicated solution. As a result, the region where the cold emitter is formed is defined as the opening 113 as shown in FIG.

The diameter of this opening is about 1 μm,
For example, a hole is also formed in the gate electrode layer 104 by performing dry etching from the upper surface with SF ₆ gas or the like. Next, the laminated substrate is immersed in an etchant to perform isotropic etching, and the insulating layer 103 is etched to form a hole 114 as shown in FIG. When the oblique deposition of aluminum serving as the release layer 105 is performed while the entire laminated substrate is supported and rotated obliquely, the release layer 105 is not deposited in the opened hole 114, and the gate 10 is not deposited.
It is selectively deposited only on the surface of the four electrode layer.

Next, the hole 114 of such a laminated substrate is used.
When molybdenum as an emitter material is deposited from the side by forward evaporation, the evaporated molybdenum falls from the hole 114 as shown in FIG.
5 is also deposited. A cone-shaped emitter 115 is formed on the resistance layer 102 while the opening is closed by molybdenum deposited on the release layer 105. After that, when the peeling layer 105 and the emitter material layer 106 on the gate electrode layer 104 are removed by etching,
A field emission device (FEC) having a shape as shown in FIG.
Can be obtained.

In the above manufacturing method, when forming a laminated substrate, a second insulating layer 107 is coated above the gate electrode 104, and a second gate electrode layer 108 is formed above the insulating layer 107. When a laminated substrate is used, as shown in FIG.
It is also possible to manufacture an FEC having a tetraode structure in which 8 can be used as a focusing electrode.

As shown in this figure, the FEC allows the distance between the cone-shaped emitter 115 and the gate electrode layer 104 to be submicron, so that the distance between the emitter 115 and the gate electrode layer 104 is only 80 to 120 volts. By applying a voltage, the potential gradient at the tip of the emitter 115 becomes extremely high, so that electrons can be emitted at room temperature in a vacuum.

FIG. 7 is a perspective view showing a conventional technique for forming a display device using a field emission device formed by the above-described method. (JP-A-2-309541)
In this figure, 100 is a glass substrate, 101 is a cathode electrode layer, 102 is a resistance layer, 103 is an insulating layer, 10
Reference numeral 4 denotes a gate electrode layer. A glass substrate 120 that forms a display surface is disposed to face the laminated substrate, and an anode conductor layer 121 is provided as a transparent electrode on the inner surface thereof. A fluorescent material 122 that emits light is applied in a predetermined pattern,

The space between the upper and lower glass substrates is kept in a vacuum state. In this conventional technique, a voltage for scanning the gate electrode is applied to each divided gate electrode via a thin film transistor (TFT) 117. Scanning electrode 11
8 and is configured such that electrons are emitted from each of the emitters 115 when a voltage is applied to the gate electrode via the TFT 117.

Therefore, a scanning signal is supplied to the scanning electrode 118 (drain electrode) of the TFT 117 and a display screen signal is supplied to the scanning electrode 119 connected to the gate electrode of the TFT 117 in synchronization with the scanning signal. By providing the drive circuit, it is possible to emit light from the fluorescent material applied to the anode electrode layer and display characters and graphics.

[0012]

In the above display device, since the emitter 115 sufficiently emits electrons corresponding to an image signal, the gate electrode 104 has a voltage of 40 to 80 volts even when there is no resistive layer. When a voltage must be applied and a resistive layer is provided, the gate electrode 1
It is necessary to apply a voltage of about 80 to 120 volts to 04. For this reason, it is extremely difficult to form a high-breakdown-voltage TFT capable of performing a sufficient switching operation with respect to such a voltage on the laminated substrate in units of several μm.

It is also conceivable that the anode electrode 121 is divided into pixels and arranged in a matrix, and a scanning voltage is applied to the striped anode electrode. In this case, a higher voltage (several hundred volts) is applied. Therefore, there is a problem in that the drive circuit becomes expensive, heat is generated, the cost is increased, and power saving becomes difficult.

[0014]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a plurality of cone-shaped emitters for emitting electrons are deposited above a cathode conductor layer formed on a substrate. A plurality of field emission devices each including a first gate electrode layer for emitting electrons from the emitter and a focusing electrode layer disposed above the gate electrode layer for converging the extracted electrons. And the field emission device is divided into predetermined blocks on the display surface, and X, Y
A matrix control line extending in the direction is arranged, a switching element is formed between the intersection of the control line and the focusing electrode conductor, and a scanning signal for image display is supplied to the focusing electrode via the switching element. It is configured to be performed.

[0015]

Since the control of emitted electrons by the focusing electrode can be performed at a relatively low voltage, the switching element can be formed by a low voltage type TFT or a MIM two-terminal switching element, and the integrated technology is utilized. By arranging them at high density, image quality can be improved.

[0016]

FIG. 1 is a partially enlarged cross-sectional view of a field emission device employed in a display device according to the present invention. As described above, reference numeral 100 denotes a glass substrate. Reference numeral 101 denotes a cathode electrode layer formed on the upper surface of the glass substrate by vapor deposition or the like. On the upper surface of the cathode electrode layer 101, a resistance layer 102 is laminated. And this resistance layer 10
Above 2 is a cone-shaped emitter 11 whose tip protrudes in a conical shape made by the above-mentioned Spindt method or the like.
5 have been deposited. Above the emitter 115, the gate electrode layer 10 supported by the insulating layer 103 is formed.
4 and a focusing electrode layer 108 is further provided on the upper surface thereof with a second insulating layer 107 interposed therebetween.

The second insulating layer 107 and the focusing electrode layer 1
08 is a well-known FEC having a tetraode structure, and is used when forming a laminated substrate by the above-mentioned Spindt method or the method proposed by the present applicant (Japanese Patent Application No. 5-191848). Although the structure can be easily formed by previously laminating the insulating layer and the focusing electrode layer, the detailed manufacturing method is omitted.

Each emitter 115 has a height of about 1 micron, and electrons emitted from one emitter 115 pass through a gate electrode layer 104 and a focusing electrode layer 108 provided with holes of about 1 micron. Are emitted toward the anode electrode side. And the anode electrode 1
21, the fluorescent material is excited, and that portion emits light. In the light emitting portion, several tens to several hundreds of such field emission elements form one pixel, and each pixel applies a scanning voltage to a strip-shaped electrode wired in a matrix as described later. An image is displayed by scanning.

An inverted staggered thin film transistor (TFT) is formed on the side surface of the field emission element employed in the display device of the present invention during the manufacturing process. That is, a gate electrode 201 of a TFT is formed by vapor deposition or the like above a portion where the insulating layer 103 in FIG. 1A is extended, and a gate insulating layer 202 made of SiO ₂ is formed thereon. And the second insulating layer 1 extending in the lateral direction.
07, an amorphous silicon layer 203 and an adjacently doped n + amorphous silicon layer 204 are formed.
A channel region serving as a signal path of T is formed. At both ends of the channel region, a source electrode 205 and a drain electrode 206 of the TFT are provided.
And the drain electrode 206 is formed at the same time when the conductor forming the focusing electrode layer 108 of the field emission device is deposited.

As is well known, when a voltage is applied to the gate electrode 201 of such an inverted stagger type TFT, charges can move in the channel,
The source electrode 205 and the drain electrode 206 are controlled to be conductive. As a result, the potential of the focusing electrode 108 becomes equal to the potential applied to the source electrode 205.

In the above-described embodiment, the gate electrode 104 and the focusing electrode 108 having an opening above each of the cone-shaped emitters 115 are formed, but as shown in FIG. Emitter 115 as electrode 108
It may be configured to have a slightly wider opening for controlling two or four of them at once.

In the above embodiment, a TFT formed on the same substrate is used as a switching element for applying a voltage to the focusing electrode 108. The switching element is shown in FIG. MIM (Me
tai Insulater Metal) The two-terminal switching element may be configured in a similar manner. That is, as shown in FIG. 3A, a conductive material (Ta) is vapor-deposited on the upper surface of the insulating layer 103 extending in the lateral direction, and one terminal 207 is vapor-deposited in a strip shape. Ta ₂ O ₂ is coated as an insulating layer 208. The above-mentioned material constituting the focusing electrode is extended and vapor-deposited above the insulating layer to form a terminal 209 in another direction, and a MIM (Metal Insulate) in which ON / OFF control is performed between the terminals by a tunnel effect.
r Metal) A two-terminal switching element is formed. Note that FIG. 2 (b) is, as shown in FIG. 1 (b),
FIG. 3 is a cross-sectional view in a case where a focusing electrode 108 is provided in common for two or four emitters 115.

The field emission device employed in the display device of the present invention has a focusing electrode layer 108 having an action of converging electrons emitted from the emitter 115, as embodied by the above-described cross-sectional structure. TFT drain electrode 2
Reference numeral 06 is connected on the laminated substrate. Therefore, when the source electrode 205 and the gate electrode 201 of this TFT are connected to the intersections of the control lines arranged on the matrix and operation voltages are sequentially applied, a video signal can be displayed as described in the conventional display device. Will be able to

FIGS. 3A and 3B show the trajectories of electrons simulating how the electrons emitted from the emitter of the field emission device as described above are affected by the focusing electrode. And the gate hole diameter is 1μ
m, cone height 1 μm, focusing electrode hole diameter 1.2 μm,
When the distance between the gate and the focusing electrode is 1 μm, the thickness of the gate electrode layer and the focusing electrode layer is 0.4 μm, and the distance from the bottom of the cone to the anode electrode is 200 μm, the emission of the right half emitted electrons from the center point P at the top of the emitter is considered. The trajectory is drawn.

The trajectory of the electrons obtained by this simulation is such that the point for emitting electrons is located at the vertex P of the emitter, and the gate electrode G1 for emitting electrons is provided with a slight gap (1 μm). It is assumed that the focusing electrode G2 is further disposed above the anode electrode layer A and the anode electrode layer A is further disposed above the above distance and has the dimensions described above. When 120 volts are applied to the gate electrode G1 and 400 volts to the anode electrode, and when the focusing electrode G2 is 0 volt, most of the electrons emitted from the apex P of the emitter as shown in FIG. It can be seen that it has not reached the anode electrode.

However, in this state, 10 V is applied to the focusing electrode G2.
When a small voltage is applied, as shown in FIG. 3B, the flow of the electrons drifted by the space charge is remarkably improved, and the flow of the electrons is changed so that most of the electrons reach the anode electrode. The flow changes and the anodic current increases.

FIG. 4 shows the emitter 11 for electron emission described above.
5 is a block diagram showing a field emission device cell (hereinafter, referred to as a cell) 300 indicated by a dashed-dotted line, and shows a drive circuit for dynamically driving each cell. That is, each cell 300 has a plurality of emitters 11
5 and the gate electrode 104 for each emitter 115
And the focusing electrode 108. Each cell 30
0, one TFT is provided.
Of the control lines G1, G2, G3,.
... Connected to Gn. Control lines S1, S2, S3,..., Sn are connected to the source electrodes of the TFTs in column units.

The gate electrodes 104 of each cell 300 are connected in common and connected to a predetermined acceleration voltage (E1), and the emitter 115 of each cell 300 is also collectively connected to the cathode electrode which is conductive via a resistance layer. In addition, wiring is performed so that a predetermined voltage (normally, a zero-level voltage E2) is supplied. The floating capacitance C formed on the drain side of the TFT
Although not shown, all the terminals G are grounded.

The above-described display driving circuit includes, for example, control lines G1, G2, G3,.
..A control line S connected to a drive circuit for sequentially supplying scan pulses in a time-division manner and arranged vertically
When a video signal (character / graphic signal) for one horizontal period is sequentially supplied to 1, S2, S3,... In synchronization with the scanning pulse, as described above, the cell 300 when the TFT is turned on is focused A voltage lower by about 10 volts is applied to the electrode 108, and the electrons emitted from the emitter in this cell strike the anode electrode as shown in FIG. 3B. As a result, the cell 300 in which the TFT is turned on
The phosphor located above the light-emitting device emits light, and an image can be displayed according to the video signal. Although the switching element shown in FIG. 4 is formed by one TFT, it is preferably formed by a C-MOS type switching element using two TFTs.

FIG. 5 shows that the above-mentioned field emission element block is M
4 shows an example of a circuit for driving a cell 301 constituted by an IM2 terminal switching element.
Are configured to be activated by a MIM two-terminal switching element. In this case, the control lines G1, G2, G3 provided in the horizontal direction as in the case of FIG.
... and the control line S provided in the vertical direction
The cell 301 located at the intersection of 1, S2, S3,... Emits electrons. Since this switching element has two terminals, it performs an off-through control operation, that is, when the potentials of the control lines G1, G2, G3,... Are high, the control lines S1, S2, S3.・
.. Are activated, and the focusing electrode 10 of this cell is activated.
8, a voltage is applied.

Although the above embodiment has been described with reference to the case where the focusing electrode 108 has a single layer, it is needless to say that the technology of the present invention can be applied to an FEC having a pentode structure having two focusing electrodes. Nor.

[0032]

As described above, the display device of the present invention has a four-electrode field emission device including at least a gate electrode for extracting electrons to the emitter and a focusing electrode for limiting the spread of the extracted electrons. Since a switching element that is electrically connected to the focusing electrode is formed on the substrate on which the field emission element is formed by an integration technique, a low-voltage signal for scanning is transmitted to the focusing electrode via the switching element. Can be applied. Therefore, it is easy to integrate the size of the switching element on the order of μm, and the resolution of the display screen can be improved.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a part of a field emission device employed in a display device of the present invention.

FIG. 2 is an enlarged sectional view of a part of a field emission device according to another embodiment of the present invention.

FIG. 3 is an explanatory diagram simulating a trajectory of an electron extracted from a field emission device.

FIG. 4 is a wiring diagram illustrating an example of a drive circuit of a display device including the field emission device of the present invention.

FIG. 5 is a wiring diagram showing an example of a driving circuit when the field emission device of FIG. 3 is used.

FIG. 6 is an explanatory view showing one example of a method for manufacturing a field emission device.

FIG. 7 is a perspective view showing a conventional example of a display device constituted by FEC.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 glass substrate 101 cathode electrode layer 102 resistive layer 103, 107 insulating layer 104 gate electrode layer 108 focusing electrode layer 121 anode electrode layer 201 gate electrode of TFT 205 source electrode 206 of TFT 206 drain electrode

Claims (4)

(57) [Claims] 1. A large number of cone-shaped emitters for emitting electrons are deposited above a cathode conductor layer formed on a substrate, a gate electrode layer for emitting electrons from the emitter, and A stacked substrate including a plurality of field emission elements each including one or two focusing electrode layers disposed above the gate electrode layer for convergence; In a display device in which an anode electrode to which a material is attached is enclosed in a vacuum container, the plurality of field emission elements are divided into predetermined blocks on a display surface, and extend in the X and Y directions on the laminated substrate. Control lines arranged in a matrix are arranged, and a switching element is formed between an intersection of the control lines and a focusing electrode of the field emission element. Display device characterized by progressive scanning signal into a bundle electrode is configured to be supplied. 2. The display device according to claim 1, wherein said switching element is constituted by a thin film transistor. 3. The display device according to claim 1, wherein the switching element is constituted by a MIM two-terminal switching element. 4. The display device according to claim 1, wherein the focusing electrode is configured to simultaneously control the plurality of emitters as a group.