KR100256530B1 - Field emission cold cathode - Google Patents

Abstract

The present invention relates to an electric field emission cold cathode in which a high resistance resistor can be formed with a low resistance. A resistive layer is formed on the conductive substrate having a cold cathode function having the first insulating layer inserted therein, a gate electrode is formed on the resistive layer having the second insulating layer inserted therein, and a plurality of gate electrodes Openings are formed, and conical emitter cones are formed over each resistive layer of these openings. The resistive layer is made of an emitter forming region and a plurality of resistors arranged uniformly around the circumference of the emitter forming region, each resistor being electrically connected to the conductor substrate. Emitter cones located on the outermost circumference are arranged with the same resistance length for each resistor in the resistive layer.

Description

Electric field emission cold cathode

The present invention is directed to an improved field emission cold cathode prepared using semiconductor microprocessing techniques.

When an electric field of about 10 ⁶ to 10 ⁷ (V / cm) is applied to the surface of the metal or semiconductor, electrons pass through the barrier even at room temperature, and electrons are released in a vacuum by the tunnel effect. This phenomenon is known as electron emission, and the cathode emitting electrons according to this principle is known as an electric field emission (cold) cathode.

Due to the size of the micron, the field emission cold cathode enables high density integration, and further has the advantages of high efficiency and high current density when compared to the hot cathode. In addition, the emitted electrons are active in a vacuum state, and the device using the cold cathode is faster than the solid state device. These characteristics are expected to be useful in applications such as high amplitude devices and high brightness displays.

Recently, known field emission cold cathodes, known as Spindt type, are described as being on the order of microns and manufactured by using semiconductor integrated technology. By using semiconductor microprocessing techniques in the production of this type of field emission cold cathode, the distance between the conical emitter and the gate electrode is on the order of microns. This field emission cold cathode may emit electrons from the emitter cone tip when a voltage of about 30 to 60V is applied between the emitter cone and the gate electrode. Since field emission cold cathodes of this type can be fabricated with peaks between emitter cones on the order of several microns, hundreds to tens of thousands of field emission cold cathodes can be supplied over a substrate.

As an example of the above-described electric field emission cold cathode, Japanese Patent Laid-Open Publication No. 282716/1995 forms a plurality of cold cathode emitters in a rectangular emitter formation region, and then the outer circumference of the rectangular emitter formation is a material of high resistance. The structure that allows constant and high-speed reaction control of the discharge current is described. This field emission cold cathode is shown in the top view of FIG. 1 and in the cross-sectional view of FIG. 2.

As shown in FIGS. 1 and 2, this electric field emission cold cathode comprises an emission region made of a gate electrode 2 and a cathode 1. This emitting region is a resistor 3 having a much higher resistance than that of the cathode 1 formed in a frame shape with a constant width along the outer circumference of the square region cut out from the cathode 1, and the inner circumference of the resistor 3. It consists of the square conductor 4 formed as a continuous film in the inside.

On the surface of the conductor 4 are provided various emitter cones 5 which are fine cold cathodes. This emitter cone 5 is formed of an electron emitting material such as molybdenum and is formed in a substantially conical shape, the ends of which are substantially the gate openings 2a for the passage of electrons formed in the gate electrode 2. Is located in the center of. An anode for receiving the emitted electrons is formed on the upper facing surface of the gate electrode 2 with an inserted vacuum portion (not shown in the figure).

By adding a prescribed voltage between the cathode 1 and the gate electrode 2 of this field emission cold cathode, the specified voltage is in turn applied to the emitter cone 5 within the emitter forming region 15 and the tunnel By effect, electrons are emitted from each emitter cone 5. In this case, the specified voltage is such that the electric field strength at the end of each emitter cone 5 is 10 ⁷ (V / cm). The reason for providing a resistive layer between the emitter and the cathode in the above described configuration is as follows.

In general, in an electric field emission cold cathode, the ends of the emitter cones are arranged at extremely fine distances, at very fine levels, from the gate electrode. Since hundreds to tens of thousands of emitter cones are formed on the substrate, a short circuit may occur between the gate and the emitter cone due to the dust generated in the manufacturing process. Even a short circuit between one emitter cone and the gate electrode causes a short circuit between the cathode and the gate electrode, resulting in inoperability due to failure to apply voltage to the emitter cone.

In addition, gas leakage may occur in some cases when the field emission cold cathode is initially operated, and this gas is discharged between the emitter cone and the gate electrode or anode, causing a high current to flow through the cathode, resulting in failure of the cathode.

In addition, some emitter cones between multiple emitter cones may tend to release the author more easily because of the variability that occurs during manufacture. As a result, during electron emission, electron emission tends to gather around these emission cones, which are more likely to emit, which will cause the amount of current to vary greatly.

As shown in FIG. 2, a resistor 3 having a constant width is formed along the outer circumference of the emitter forming region 15 between the cathode 1 and the emitter cone 5, and has a non-uniform shape. By means of one emitter cone along the emitter cone 5, it starts to emit an unusually high number of electrons, causing a voltage drop between the gate electrode 2 and the cathode 1 due to the resistor 3 Occurs. As a result of the voltage drop, when an abnormally high current is emitted, the voltage applied to the emitter cone in response to the emission current drops, thereby suppressing electron emission and allowing electron emission to be stabilized at each emitter cone 5. And prevents damage to the cathode 1.

As another example of the above-described electric field emission cold cathode having a size of a micron size, Japanese Patent Laid-Open Publication No. 94076/1995 discloses a resistance between a cathode and an emitter that is fused when a circuit between the emitter and the gate is short-circuited. A device has been described in which an insulating layer is provided on the layer and the melt-dispersant is not theoretically dispersed. A partial view of the cathode conductor of this field emission cold cathode is shown in FIG. 3.

In Fig. 3, a plurality of cutouts 6 are provided in the cathode 1, and in each cutout 6 a rectangular resistor 3 is provided. The resistor 3 has eight terminals 7 around it, and these terminals 7 electrically connect the cathode and the resistor 3 to each other. An electric field cold cathode having a plurality of emitter cones 5 is formed on this resistor 3.

FIG. 4 is a cross-sectional view taken along line B-B and shows the state of the electric field emission cold cathode formed on the resistor 3 shown in FIG. 3. In FIG. 4, the cathode 1 is formed on the insulating substrate 9, and in the cutout 6 formed in the cathode 1, the resistor 3 has a terminal (terminal portion 7) having a cathode 1. It is formed to be connected to the top of the. The gate electrode 2 is formed on the resistor 3 with an insulating layer inserted therein, and then in each of the plurality of openings 8 provided in the gate electrode 2 and the insulating layer 10 an emitter cone ( 5) is formed. In addition, a gate electrode 2 is formed on the cathode 1 together with the inserted insulating layer 10.

In the event that a short circuit occurs between the gate electrode 2 and the emitter cone 5 in the electric field emission cold cathode, the terminal portion 7 provided in the outer circumference of the resistor 3 is fused to form an emitter formation region. Insulate completely. In this way, the terminal portion 7 functions as a fuse for a plurality of emitter forming regions, whereby the device fails even if an abnormality occurs in a part of the region, and thus the emitter fails. I will be able to function in my case.

Nevertheless, the above-described electric field emission cold cathodes of the prior art have the following problems:

(1) In the invention described in Japanese Patent Laid-Open No. 282716/95: As shown in Fig. 5, there is a proportional relationship between the voltage (breakdown voltage) and the resistance causing the failure of the negative electrode, For example, at a field emission cold cathode, a voltage of at least 100 V must be maintained, and a resistance of at least 50 KΩ must be obtained.

However, some conditions apply when forming resistors. In order not to discharge, the relationship between the resistance R and the resistance length L shown in FIG. 6 is applied as the dimensional condition of the resistor. In addition, the relationship between the ion implantation amount and the layer resistance shown in FIG. 7 is applied as a manufacturing condition of resistor formation. In this case, the impurity concentration shown in FIG. 7 corresponds to the resistor length L shown in FIG. 6.

As can be seen from the relationship shown in Figs. 6 and 7, the resistance length L should be 5 mu m when a resistance of at least 50 KΩ is obtained, and according to this condition, the ion implantation amount is 10 ¹⁴ cm ^-2 and The resistance is formed using a high resistance layer region having a high resistance with a low concentration of impurities, and as a result, a wide variety will appear in the manufactured product.

Using a low resistance layer region having a low resistance, a low impurity concentration, and extending the resistance length L to 100 [mu] m with an ion implantation amount of 10 ¹⁶ cm ^-2 can be regarded as a means of increasing resistance, but outside the emitter formation region In the case where the resistance is formed with a constant width along the periphery, the resistance is independent of the resistance length L, and the resistance can rise to a high level even if the resistance length L is extended to 100 mu m.

(2) In the invention described in Japanese Patent Application Laid-Open No. 94076/95, the resistor shown in Fig. 4 in which narrow terminal portions are formed at four corners of the resistive layer serving simply as a fuse does not prevent destruction of the emitter formation region. can not do it. In this type of structure where a resistor is used as a fuse, the requirement of the resistor to fuse when a short circuit current flows through the resistor requires quite narrow patterning. The use of resistors that require such narrow patterning as a safeguard against discharge requires a resistive layer with a high resistor, and the use of high resistance components entails poor reproducibility and poor stability.

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems and to form a high resistance resistor having a low resistance, not only to properly adjust the resistance required for the emission characteristics, but also to protect it from destruction, and to have excellent reproducibility. It is to provide an electric field emission cold cathode.

1 is a plan view of a field emission cold cathode of the prior art described in Japanese Patent Laid-Open No. 282716/95.

2 shows a cross section of FIG. 1;

3 is a plan view of the electric field emission cold cathode of the prior art described in Japanese Patent Laid-Open No. 94076/95.

4 shows a cross section taken at line B-B in FIG. 3;

5 is a graph showing the relationship between the resistance of a field emission cold cathode and the breakdown voltage.

6 is a graph showing the relationship between the resistance and the resistance length of a resistor used in an electric field emission cold cathode.

7 is a graph showing the relationship between the layer surface resistance and the ion implantation amount of a resistor used in an electric field emission cold cathode.

8 is a plan view showing one embodiment of the electric field emission cold cathode of the present invention.

FIG. 9 shows a section taken at line A-A in FIG. 8; FIG.

10 is a plan view showing another embodiment of the present invention.

11 is a plan view showing another embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

1 cathode 2 electrode

11: conductor substrate 13: insulating layer

12a: cathode power supply 12b: non-oxidation contact

14 reaction layer 15 emitter forming region

15 ': Resistor 18: Focusing electrode

In order to achieve the above object, a resistance layer formed on the conductor substrate constituting the cathode together with the first inserted insulating layer; A gate electrode formed on the resistance layer with an inserted second insulating layer; And a field emission cold cathode comprising conical emitter cones formed on the resistive layer, respectively, in the plurality of openings, wherein the plurality of openings pass through the gate electrode and the second insulating layer as far as the surface of the resistive layer. Formed within, the resistor layer is formed of an emitter formation region in which the emitter cone is formed, and a plurality of resistor units of the same structure are constantly arranged around the outer circumference of the emitter formation region, and the plurality of resistor units Are each electrically connected to the conductor substrate. In the above case, of the above-described emitter cones, the emitter cones located at the outermost periphery may be positioned with the same resistance length for each resistance unit of the resistance layer, which is connected with the conductor substrate. It is determined as the distance from the end of each resistor unit.

Further, the emitter forming region may be a simple cross shape having an edge between each end having a defined curvature and each end having a rectangular shape. In such a case, the rectangular resistance may be a structure formed on each of the ends of the emitter forming region. The rectangular resistor may also be tapered.

Alternatively, a structure in which the emitter forming region is formed as a disk may be employed, and the emitter cone is formed with concentric circles centered at the center of the emitter forming region.

Alternatively, a structure in which the emitter forming region is formed in a square or a rectangle, and the emitter cones on opposite sides are arranged symmetrically with the center of the emitter forming region as the center of symmetry.

In some cases of the field emission cold cathode described above, the resistive layer may be a silicon layer having an ion implantation amount of at least 10 ¹⁶ cm ⁻² . In this case, the impurity is phosphorus, boron, arsenic, or antimony.

According to the present invention as described above, the insulating layer necessary for the emission characteristics and protecting against fracture is made of a plurality of resistor units which are constantly arranged around the outer circumference of the emitter forming region, and as a result, the specified resistance value is It is obtained by changing the resistance length L and the resistance width W of the resistor unit. Therefore, a high resistance material having a low resistance can be used in the resistive layer, which is necessary for the emission characteristic and can appropriately adjust the resistance for protecting against breakage, and high reproducibility can be obtained.

In addition, the emitter cone located on the outermost circumference, emitter cone around the resistance formed over the outer circumference of the emitter formation region, in a configuration arranged such that the resistance length is the same for each resistance unit of the resistive layer. There is no difference in distance between and the central emitter cone and the central emitter cone, and as a result, there will be no voltage drop between the gate electrode and the cathode due to the resistor. In a structure in which a constant balance of resistance is achieved on the resistive layer before the gate electrode and the cathode, fusion of the resistor will not occur due to the discharge flow.

As described above, according to the present invention, the high resistance resistor can be formed to have a slight change in the layer resistance and a low resistance, and as a result, the present invention provides an electric field emission cold cathode having excellent emission characteristics as well as protection against destruction. It can provide, and also provides excellent reproducibility.

In addition, the resistance unit constituting the resistive layer and the emitter forming region can be simultaneously formed in the shape specified by the patterning performed by the etching process, so that the high resistive resistive layer can be formed with excellent control, and the production yield Can be expected to improve. Finally, since the configuration of the present invention eliminates the voltage drop by the resistance between the gate electrode and the cathode and eliminates the fusion of the resistor by discharge, the field emission cold cathode is characterized by stable operation and high reliability.

The above and other objects, features and advantages of the present invention will become apparent from the following description based on the accompanying drawings which illustrate by way of example preferred embodiments of the invention.

[Detailed Description of Preferred Embodiments]

Next will be described with respect to embodiments of the present invention with reference to the accompanying drawings. 8 is a plan view showing a first embodiment of the field emission cold cathode according to the invention and FIG. 9 shows a cross section taken along line A-A of FIG. 8.

An insulating layer 13 made of silicon dioxide (SiO ₂ ) is formed on the surface of the conductor substrate 11 made of single crystal silicon (Si) by a thermal oxidation method, which acts as a cathode, and then a lithography or RIE (reactive) Dry etching, such as ion etching), forms the non-oxidation contact portion 12b, which acts as the cathode power supply 12a at four separate locations. Next, a reaction layer 14 made of, for example, polysilicon (poly-Si) is formed on the surface, and the insulating layer 13 and the contact portion 12b are formed thereon by a CVD method. On this reaction layer 14, impurities such as phosphorus (or boron, arsenic, or antimony) are implanted at an ion implantation level of 10 ¹⁶ cm ⁻² , resulting in a low resistance layer surface resistance of, for example, 100 KΩ / *. do. The resistive layer 14 has an emitter forming region 15 in which an emitter cone 5 is formed in a portion located above the insulating layer 13, over the outer circumference of the emitter forming region, and in the region as the center of symmetry. Four resistors 15 'are formed in an arrangement opposite the center. The emitter forming region 15 has a simple cross shape, the four terminal portions have a rectangular shape, and the edge between each terminal portion has a prescribed curvature (determined according to the uniform arrangement of the resistance lengths L to be described). . On each end of the emitter formation region 15, a rectangular resistor 15 'is formed. This cross-shaped resistive layer 14 is in electrical contact with the conductor substrate 11 (cathode) by contact portions 13b (i.e., supply portions of the electrodes 12a) adjacent to each end (17 in FIG. 8). . In this case, the resistive layer 14 is patterned by etching in a form having a resistive width W of 5 μm and a resistive length L of 10 μm so that a resistance of 50 KΩ is obtained. The emitter forming region 15 and the resistive region are formed simultaneously during this patterning.

An insulating layer 10 made of silicon nitride (Si _x N _y ) or silicon oxide (Si _x O _(1-8x) ) is formed on the surface on which the resistive layer 14 is formed. For example, a gate electrode 2 made of a conductive material such as tungsten silicide WSi or tungsten W is formed on the insulating layer 10 by a sterling method. In the insulating layer 10 and the gate electrode 2, a plurality of cylindrical openings 8 penetrating as far as the surface of the resistance layer 14 are formed, and the openings 8 are evaporated on the surface of the internal resistance layer 14. By the method, a conical emitter cone 5 composed of a refractory metal or a distatic mixture such as molybdenum (Mo) is formed. Here, the opening 8 may be formed by a photoresist method and a dry etching or wet etching method such as RIE.

In the formation of the emitter cone 5 described above, the emitter cones 5 located on the outermost circumference have their distances (resistance length L) from the connecting ends of the contact portions 12b of each end (resistor 15 '). It is arranged to be equal to each end of the layer 14 (resistor 15 '). This arrangement eliminates the difference in distance between the outer edge and the center emitter cone 5 for a resistor formed beyond the circumference of the emitter forming region 15. As a result, the influence of the voltage drop can be eliminated.

In an electric field emission cold cathode constructed as described below, applying the specified voltage between the cathode 1 and the gate electrode 2, as in the above-described example of the prior art, the specified voltage in the emitter forming region is applied to the emitter cone 5. To be applied, electrons are emitted from each emitter cone 5 by the tunnel effect.

In this embodiment, the resistor 15 'formed over the outer circumference of the emitter forming region 15 is uniformly disposed, and the overall resistance balance of the resistive layer 14 between the gate electrode 2 and the cathode 1 is It is structured so that uniformity and, as a result, fusion of resistance due to discharge do not occur.

In addition, since the emitter forming region 15 and the resistor 15 'making the resistive layer 14 can be formed by patterning using an etching process, the emission characteristics can be improved by using a resistive layer having a low resistance. A high resistance resistive layer may be formed which is necessary to obtain and protect against breakage.

In addition, if the insulating layer 13 is formed by the thermal oxidation method, the thickness of the insulating layer will grow in the direction of the conductor substrate 11, and the gate electrode 2 can be formed more evenly than when the CVD process is used. have. By further using the leveling technique, a more even gate electrode 2 can be formed.

If the resistor 15 'shown in Fig. 8 is formed in a tapered form T as indicated by the dotted line, a higher resistance layer 14 can be obtained. In this case, the resistance of the resistance layer 14 can be adjusted to a desired value by adjusting the tapering range.

Although the above description has been made of a configuration having four resistors 15 'at the outer end of the emitter forming region 15, the present invention is not limited to four, but is uniformly around the surrounding emitter forming region 15. Any number can be arranged if it can be arranged. In other words, any number of resistors 15 'is allowed.

[Other specific examples]

In the above-described embodiment, the emitter cone located at the outermost circumference has emitters symmetrically with respect to each resistor of the resistive layer 14, although the resistor length L is uniformly arranged for each end of the resistive layer 14. By arranging the cones 5, the voltage drop can be eliminated.

For example, as shown in FIG. 10, a structure may be employed in which the emitter forming region 25 in which the emitter cone is formed is configured as a disk, and the emitter cone is disposed concentrically centered at the center of the disk. Four resistors 25 'are uniformly disposed around the outer circumference of the emitter forming region 25. By adopting such a configuration, when the focusing electrode 18 is formed on the circumference of the emitter forming region 25 as an application of the CRT, the focusing of the electron beam emitted from the emitter forming region 25 toward the anode can be improved. have.

Thus, as shown in Fig. 11, a structure in which the emitter forming region in which the emitter cone is formed is formed in a rectangle or a square is adopted, and the emitter cones are arranged symmetrically with respect to each opposite side and the center of symmetry. The resistor 35 'is constantly arranged around the outer circumference of the emitter forming region 35. Adopting such a configuration allows the use of the present invention as a pixel area inside the screen of the ultra-thin display device.

However, the above description is for illustrative purposes only, and the features and advantages of the present invention are not limited to those described above, and the arrangement of parts may be changed within the scope of the appended claims.

Claims (21)

An electric field emission cold cathode comprising: a resistance layer formed on a conductor substrate constituting a cathode together with an inserted first insulating layer; A gate electrode formed on the resistance layer with an inserted second insulating layer; And a conical emitter cone formed on the resistive layer in each of the plurality of openings, the plurality of openings being formed in the gate electrode and the second insulating layer penetrating as far as the surface of the resistive layer. And the resistor layer is made of an emitter forming region in which the emitter cone is formed, and a plurality of identically structured resistor units are constantly arranged around the outer circumference of the emitter forming region, and the plurality of resistor units are respectively An electric field emission cold cathode, which is electrically connected to a conductor substrate. The emitter cone of the emitter cone, located at the outermost circumference, is positioned with the same resistance length for each resistance unit of the resistive layer, wherein the resistance length is established with the conductor substrate. The field emission cold cathode, characterized by the distance of the emitter cone from the end of each resistor unit. 2. The field emission cold cathode of claim 1, wherein the emitter forming region has a simple cross shape with an edge between each end having a specified curvature and each end having a rectangular shape. 4. The field emission cold cathode of claim 3, wherein a rectangular resistor is formed above each end of the emitter formation region. 5. The field emission cold cathode of claim 4, wherein the rectangular resistors are each tapered. The field emission cold cathode of claim 1, wherein the emitter forming region is formed as a disk and the emitter cone is formed in a concentric circle centered at the center of the emitter forming region. The field emission method of claim 1, wherein the emitter forming region is formed in a square or a rectangle, and the emitter cones on opposite sides are arranged symmetrically with a center of the emitter forming region as a center of symmetry. Cold cathode. The field emission cold cathode of claim 1, wherein the resistance layer is a silicon layer having an ion implantation amount of at least 10 ¹⁶ cm ⁻² . 3. The field emission cold cathode of claim 2, wherein the resistance layer is a silicon layer having an ion implantation amount of at least 10 ¹⁶ cm ⁻² . 4. The field emission cold cathode of claim 3, wherein the resistance layer is a silicon layer having an ion implantation amount of at least 10 ¹⁶ cm ⁻² . 5. The field emission cold cathode of claim 4, wherein the resistance layer is a silicon layer having an ion implantation amount of at least 10 ¹⁶ cm ⁻² . 6. The field emission cold cathode of claim 5, wherein the resistance layer is a silicon layer having an ion implantation amount of at least 10 ¹⁶ cm ⁻² . The field emission cold cathode of claim 6, wherein the resistance layer is a silicon layer having an ion implantation amount of at least 10 ¹⁶ cm ⁻² . The field emission cold cathode of claim 7, wherein the resistance layer is a silicon layer having an ion implantation amount of at least 10 ¹⁶ cm ⁻² . The field emission cold cathode of claim 8, wherein the impurity is any of phosphorus, boron, arsenic, and antimony. 10. The field emission cold cathode of claim 9, wherein the impurity is any of phosphorus, boron, arsenic, and antimony. 11. The field emission cold cathode of claim 10, wherein said impurity is any of phosphorus, boron, arsenic, and antimony. 12. The field emission cold cathode of claim 11, wherein the impurity is any of phosphorus, boron, arsenic, and antimony. 13. The field emission cold cathode of claim 12, wherein the impurities are any of phosphorus, boron, arsenic, and antimony. 14. The field emission cold cathode of claim 13, wherein said impurity is any of phosphorus, boron, arsenic, and antimony. 15. The field emission cold cathode of claim 14, wherein said impurity is any of phosphorus, boron, arsenic, and antimony.

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