JP2003151427A - Manufacturing method for field emission type electron emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a field emission type electron emitting element capable of reducing element defects caused by short-circuit and occurrence of a leakage current, and substantially cutting down a leakage current value. SOLUTION: This manufacturing method includes an element forming process S11 to form the field emission type electron emitting element structured by forming a cathode electrode, an insulating film, and a gate electrode on a base in a laminated condition, by forming a cavity in the insulating film through an opening formed in the gate electrode, and by forming a cathode in the cavity, a cleaning process S12 to clean the base on which the element is formed by the element forming process S11 by oxygen plasma or ozone, and an oxide removing process S13 to remove an oxide produced on the base by the cleaning process S12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat panel display (FPD) utilizing a field electron emission phenomenon, and more particularly to a field emission type electron-emitting device arranged in a large number in a flat panel display device. It relates to a manufacturing method.

[0002]

2. Description of the Related Art In a field emission type electron-emitting device, a voltage is applied between a gate electrode and a cathode electrode crossing each other through an insulating film to concentrate an electric field on a sharpened portion of the cathode, which causes a tunnel effect. The phenomenon that electrons are emitted into the vacuum through the barrier by the
mission) phenomenon is used to emit electrons.

As a flat-panel display device using a field emission electron-emitting device (hereinafter abbreviated as FE device), an FED (Fie
ld Emission Display) is known. Further, as a cathode structure of an FE element in an FED, a conical (Spindt-type) cathode called a cone shape is known. FIG. 6 is a cross-sectional view showing the structure of an FE element using a conical cathode. In FIG. 6, a cathode electrode 11, an insulating film 12, and a gate electrode 13 are sequentially formed in a laminated state on a substrate 10 such as glass serving as a base. An opening (gate hole) 14 is formed in the gate electrode 13, and a conical cathode 16 is formed in a cavity (cavity) 15 of the insulating film 12 which communicates with the opening 14.

In manufacturing the FE element having the above structure, first, a metal film serving as a cathode electrode material is formed on the entire surface of one side of the substrate 10, and then the metal film is patterned to form a plurality of cathode lines. The cathode electrode 11 is formed. As the material of the substrate 10, for example, non-alkali glass, low-alkali glass, quartz glass and the like, as well as ceramic materials such as alumina can be used.

Next, an insulating film 12 made of SiO _{2 is} formed on the entire surface of the substrate 10 so as to cover the cathode electrode 11, and a metal film to be a gate electrode material is further formed on the insulating film 12. By patterning the metal film, the gate electrode 13 forming a plurality of gate lines
To form. At this time, on the substrate 10, the line of the gate electrode 13 is formed to intersect with the line of the cathode electrode 11 with the insulating film 12 interposed therebetween, whereby the cathode lines and the gate lines are arranged in a matrix. It As the electrode material of the cathode electrode 11 and the gate electrode 13, aluminum (Al), titanium (T
i), titanium nitride (TiN), molybdenum (Mo), manganese (Mn), tungsten (W), chromium (C)
r), tantalum (Ta), etc. can be used. The line width (wiring width) of each of the cathode electrode 11 and the gate electrode 13 is appropriately set within a range of, for example, several tens to several hundreds of μm depending on the size of the flat panel display device or the like.

In this way, the cathode electrode 11,
After the insulating film 12 and the gate electrode 13 are formed in a laminated state, subsequently, as shown in FIG. 7A, after forming an opening 14 having a diameter of, for example, about 1 μm in the gate electrode 13, through this opening 14. The cavity 15 is formed by wet etching the insulating film 12. At this time, the opening 14 of the gate electrode 13 and the cavity 15 of the insulating film 12 are formed at the position where the cathode line and the gate line intersect. Then, while rotating the substrate 10 with respect to the gate electrode 13 on the substrate 10, as shown in FIG.
As shown in (B), the peeling layer 17 is formed in a state of covering (overhanging) the gate electrode 13 and its opening end face by vapor-depositing aluminum or the like from an oblique direction.

After that, as shown in FIG. 7C, a cathode material 18 is vapor-deposited and deposited on the peeling layer 17 to form the cathode 1 in the cavity 15 of the insulating film 12.
6 is formed. At this time, the opening 14 of the gate electrode 13
Since the cathode material 18 also grows in the lateral direction, the diameter of the opening 14 gradually decreases with the deposition of the cathode material 18, and is finally completely closed. As a result, in the cavity 15 of the insulating film 12, the gate electrode 1
3 Conical cathode 16 according to the reduction of the diameter on 3
Is formed. A refractory metal such as molybdenum can be used as the cathode material 18. In addition to molybdenum, the cathode electrode 11 and the gate electrode 13 may be used.
A refractory metal such as tungsten can be appropriately selected and used from the metal materials mentioned as the electrode material of 1.

Next, as shown in FIG. 7D, the unnecessary cathode material 18 on the gate electrode 13 is removed together with the peeling layer 17. After that, the organic and metallic residues attached to the openings 14 of the gate electrode 13 and the sidewalls of the cavity 15 are removed by hydrofluoric acid treatment together with the surface layer of the insulating film 14. Through the above manufacturing process, an FE element using a conical cathode can be obtained.

[0009]

However, in the above-mentioned conventional method for manufacturing an FE element, a step of removing the residue by hydrofluoric acid treatment after removing the unnecessary cathode material 18 together with the release layer 17 is provided. However, if the residue is firmly adhered to the side wall of the insulating film 12 or the like, there is a problem that the residue cannot be sufficiently removed with hydrofluoric acid. For these reasons, in flat-panel display devices such as FEDs, element defects such as short circuits caused by residues have occurred in a considerable amount. Further, a minute leak current (leakage current) is generated between the cathode electrode 11 and the gate electrode 13 even if the element result such as a short circuit is not reached.

Since such a short circuit or a leak current is always generated when a voltage is applied between the cathode electrode 11 and the gate electrode 13, it becomes a factor of increasing the current consumption of the flat panel display device. Further, since the hydrofluoric acid used for removing the residue has high reactivity as a chemical solution, for example, if the treatment time or the number of times of the chemical solution treatment with hydrofluoric acid is increased in order to improve the effect of removing the residue, the FE element itself is Damage is likely to occur. Therefore, at present, due to the limitation of the treatment time and the number of treatments, the improvement rate of the leak current due to the hydrofluoric acid treatment is only about 10 to 20% of the initial value, and a sufficiently satisfactory effect is not obtained.

The present invention has been made to solve the above problems, and an object of the present invention is to reduce the occurrence of element defects and leakage current due to a short circuit and to greatly reduce the leakage current value. An object of the present invention is to provide a method of manufacturing an FE element that can be used.

[0012]

The field-emission electron-emitting device according to the present invention is manufactured in such a manner that a cathode electrode, an insulating film and a gate electrode are formed in a stacked state on a substrate and an opening formed in the gate electrode. A device forming step of forming a field emission type electron-emitting device by forming a cavity in the insulating film and forming a cathode in the cavity through a substrate formed by the device forming step by oxygen plasma or ozone. It includes a cleaning step of cleaning and an oxide removing step of removing oxides generated on the substrate by the cleaning step.

In the above-described method for manufacturing a field emission type electron-emitting device, the substrate on which the device is formed in the device forming process is cleaned with oxygen plasma or ozone in the cleaning process, whereby unnecessary organic compounds remaining on the substrate surface are removed. While being removed by oxidation reaction with oxygen plasma or ozone, the surface of the metal forming the gate electrode and the cathode is oxidized together with unnecessary metal-based residues. In addition, the oxide generated on the substrate by the cleaning process, that is, the oxide film on the metal surface forming the gate electrode and the cathode, and the residual metal oxide due to unnecessary metal-based residue are removed in the oxide removing process.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, in the present embodiment, the same parts as those in the above-described conventional art will be described with the same reference numerals.

FIG. 1 illustrates the structure of a flat-panel display device obtained by using the method for manufacturing an FE element according to the present invention. (A) is an external view thereof, and (B) is an enlarged display portion thereof. Figure, (C) is an enlarged view of one pixel area of the display unit,
FIG. 3D is an enlarged cross-sectional view of the FE element in the 1-pixel area.

First, the appearance of the flat panel display device 1 is shown in FIG.
As shown in (A), the display unit 3 is arranged in front of the device housing 2. As shown in FIG. 1B, the display unit 3 includes two wiring lines 4 and 5 forming a matrix.
For example, pixels having a size of about 0.3 mm square are regularly arranged at the intersections of. Each pixel (one pixel) is composed of three sub-regions corresponding to each color of red (R), green (G), and blue (B). In each sub-region, as shown in FIG. 1C, a large number of holes 6, ... Are located at the intersections (orthogonal portions) of the two wiring lines 4, 5.
Is provided.

These holes 6, ... Are F shown in FIG.
In the E element, the opening 1 provided in the gate electrode 13
4 and the cavity 15 communicating therewith. A conical cathode 16 is formed in the cavity 15. Although the cathode 16 depends on the size of the display unit 3 of the flat-panel display device 1, generally, several thousand cathodes 16 or more are required for each pixel. Further, one of the two wiring lines 4 and 5 described above corresponds to a wiring line (cathode line) formed by the cathode electrode 11,
The other wiring line 5 corresponds to a wiring line (gate line) formed by the gate electrode 13. The cathode electrode 11 and the gate electrode 13 intersect with each other through the insulating film 12,
The cathode 16 is formed at this intersection. Also,
The cathode electrode 11, the insulating film 12 and the gate electrode 13 are
They are sequentially stacked on the substrate 10. In this FE element, when a positive (+) voltage is applied to the gate electrode 13 in vacuum, an electric field is concentrated at the tip of the cathode 16 and electrons are emitted from the tip of the cathode 16 due to the tunneling effect. It Incidentally, the configuration of the FE element is the same as that described in the prior art.

FIG. 2 is a flow chart showing a method of manufacturing the FE element according to the embodiment of the present invention. First, in the element forming step S11, an FE element is formed according to the manufacturing process (see FIG. 7) described in the prior art. However, this element forming step S11 includes a process until the unnecessary cathode material 18 deposited on the gate electrode 13 is removed, and does not include the hydrofluoric acid process described as the subsequent process.

Next, in the cleaning step S12, the substrate 10 on which the elements have been formed in the element forming step S11 is cleaned with oxygen plasma or ozone. In the cleaning step 12, a plasma ashing device used for resist removal or the like can be used, and as a processing type thereof, a batch processing type ashing device called a barrel type can be used. In addition to this, an ozone ashing device of the type that introduces ozone into the ashing chamber can also be used.

In the cleaning step S12, when the surface of the substrate 10 is irradiated with oxygen plasma using, for example, a plasma ashing device, unnecessary organic compounds 100 remaining in the cavity 15 are removed as shown in FIG. It is oxidized and decomposed into water and carbon dioxide, and is removed from the surface of the substrate 10. Further, although not shown, even in cleaning with ozone, the organic compound is decomposed into water and carbon dioxide gas by the oxidation reaction with ozone and removed from the surface of the substrate 10.

At that time, when the surface of the substrate 10 is exposed to oxygen plasma or ozone, the gate electrode 13 and the cathode 16 as well as the unnecessary metallic residue 200 in the cavity 15 are exposed.
The metal surface forming the metal oxide is also oxidized, and the oxide film 300 is formed on the metal surface. However,
As the processing time in the cleaning step 12 is about several minutes, a sufficient cleaning effect can be obtained, so that the thickness of the oxide film 300 formed on the metal surface can be suppressed to about 5 to 10 nm.

Further, in the cleaning step S12, in order to enhance the cleaning effect by oxygen plasma or ozone, for example, heat is applied by a heater or the like, or RIE (reactive
Ion bombardment such as ion etching) may be applied. Further, a gas such as argon (Ar) (for example, an addition rate of 50% or more) may be added to the oxygen gas. In particular, when the residual organic compound 100 is strongly adhered, the residual organic compound 100 is heated by applying heat or ionicity.
The oxidation reaction can be promoted and a high cleaning effect can be obtained.

Subsequently, in the oxide removing step S13, the oxide generated on the substrate 10 by the cleaning step S12 is removed. The oxides to be removed include the metal-based residue 200 oxidized in the cleaning step S12, the oxide film 300 formed on the metal surface of the gate electrode 13, the cathode 16, and the like.

In the oxide removing step S13, a wet cleaning apparatus using an alkaline aqueous solution can be used. When using this wet cleaning device, see FIG.
As shown in, the substrate 10 on which the element is formed is immersed in the cleaning tank 8 in which the alkaline aqueous solution 7 is stored. As the alkaline aqueous solution 7, for example, temperature-controlled low-concentration ammonia water can be used. At this time, the liquid temperature of the aqueous solution 7 may be room temperature, and the alkali concentration may be several% or less. The processing time may be several minutes. Further, as the management item of the aqueous solution 7, it is sufficient to manage the mixing date and time, the number of treatments, and the like. Therefore, the cleaning process of the substrate 10 can be performed very easily and safely.

Here, as shown in FIG. 4, the cleaning tank 8
When the substrate 10 is dipped in the above liquid,
The metal-based residue 200 that has been oxidized in step 1, the oxide film 300 formed on the metal surfaces of the gate electrode 13 and the cathode 16, and the like are peeled off. Then, the metal-based residue 200 and the oxide film 300 together with other residual compounds 400 are added to the substrate 10.
Are removed from the surface of. At this time, only the oxide film 300 covering the surfaces of the gate electrode 13 and the cathode 16 is peeled off, and the metal in the underlying layer does not react. Therefore,
From the surface of the gate electrode 13 and the cathode 16 to the oxide film 300
Only can be selectively stripped / removed. Further, since the oxide film 300 formed on the metal surface of the gate electrode 13 and the cathode 16 is very thin with a thickness of about 5 to 10 nm as described above, it can be easily removed by the alkaline aqueous solution 7.

Thereafter, the number of treatments is compared with the prescribed number n (S14), and if the number of treatments is less than the prescribed number n, the cleaning step S12 and the oxide removing step S13 are repeated.
The specified number of times n is set to a plurality of times, more specifically, a few times (for example, n = 3). Thereby, the cleaning step S1
The combination process of 2 and the oxide removing step S13 is repeatedly performed a plurality of times.

After that, when the number of treatments reaches the prescribed number n, the cathode electrode 11 and the gate electrode 1 in the FE element are
Conduct an electrical test for short circuit and leakage current between 3
The quality is judged (S15). In this electrical test,
A measurement voltage (reverse bias) whose positive and negative values are reversed is applied between the cathode electrode 11 and the gate electrode during actual operation (when electrons are emitted from the cathode 16), and the leak current value during that time is measured. Then, the leak current value obtained by the measurement is compared with a preset allowable current value, and based on the comparison result, when the leak current value is equal to or less than the allowable current value, “OK”, the allowable current value is determined. If it exceeds the value, it is determined to be "defective (NG)".

In the measurement result of the electrical test, if it is determined to be "defective", the process returns to the previous cleaning step S12 and the same process is repeated, and if it is determined to be "good", a series of steps is performed at that time. The process ends and the process proceeds to the next step.

As described above, in the FE element manufacturing method according to the embodiment of the present invention, the cleaning step S after the element forming step S11 is performed.
In step 12, the residual organic compound 100 is removed from the surface of the substrate 10 by cleaning the substrate 10 with oxygen plasma or ozone, and the oxide (200, 300) generated in the cleaning step S12 is removed in the oxide removing step S13. By removing it by the wet cleaning treatment, it is possible to effectively remove the residue attached to the surface of the substrate 10, especially unnecessary organic compounds and metal particles remaining in the cavity 15 of the insulating film 12. As a result, the occurrence of element defects and leakage current due to a short circuit between the cathode electrode 11 and the gate electrode 13 can be significantly reduced, and the leakage current value generated between the electrodes 11 and 13 can be significantly reduced. be able to. As a result, in the flat-panel display device, it is possible to reduce the power loss due to the element defect of the FE element and the leak current and realize the power saving.

Further, in the cleaning step S12, when oxygen plasma is used, the organic compound remaining on the substrate 10 can be oxidized and removed with good uniformity.
Furthermore, the wettability of the surface of the substrate 10 is improved by the irradiation of oxygen plasma, and the affinity between the oxide and the chemical liquid (alkaline-based aqueous solution) is increased in the subsequent oxide removal step (S13). The peeling effect of can be enhanced. Furthermore, since the gas (oxygen) used in the cleaning step S12 and the chemical solution (alkali-based aqueous solution) used in the oxide removal step S13 have low reactivity, it is possible to suppress damage to the FE element itself.

In the above embodiment, the combination process of the cleaning step S12 and the oxide removing step S13 is repeated a plurality of times, but the present invention is not limited to this, and the specified number of times n is one, A short circuit / leakage current test may be performed each time, and the above combination processing may be performed a plurality of times as necessary based on the test results.

By the way, the following remarkable effects have been obtained in the experiments by the present inventors. First, as an experimental condition, in the element forming step S11, a conical cathode 16 was formed by using tungsten as a cathode material. In the cleaning step S12, a barrel-type plasma ashing device is used, pressure: 133 Pa, output: 1 kW, reactive gas: oxygen (0 ₂ ) 100%, temperature: 50-60 ° C.
Treatment time: Under the condition of 3 minutes, the element-formed substrate 10 was washed with oxygen plasma. In addition, in the oxide removing step 13, ammonia water having a concentration of 0.5% was used, and the substrate 10 was immersed therein for 3 minutes. As a result, the average leak current value in one sub-region in one pixel is reduced to 1/10 or less in the relative ratio to the average leak current value before processing,
Further, when the combination process including the cleaning process 12 and the oxide removing process 13 was repeated several times, the average leak current value decreased to 1/100 or less. From the above results, the combination of the cleaning step S12 and the oxide removal step 13 is very effective in removing the residual organic compound and the metal-based residue from the substrate 10 after the element formation, and greatly reduces the leakage current. It was confirmed that the effect was exhibited.

Further, in an experiment conducted by the present inventors, when the FE element that has undergone the cleaning step S12 and the oxide removing step S13 is heat-treated (heated), a slight change in the leakage current value appears before and after the treatment. Was also found. That is, it was confirmed that the leakage current value after the heat treatment was slightly higher than that before the heat treatment. The reason for this is considered to be that an extra residue, which cannot be completely removed by the cleaning process S12 and the oxide removing process S13, appears on the surface of the substrate 10 by the heat treatment.

Therefore, in another embodiment of the present invention, the FE element is manufactured according to the flow chart shown in FIG. First, the element forming step S21 in the figure
The processes up to the process count determination step S24 are the element forming process S11 to the process count determination process S in the above embodiment.
The process up to 14 is performed.

Next, it is confirmed whether or not the heat treatment of the substrate 10 is completed (S25), and if not, the substrate 10 is heated in the heating step S26. In this heating step S26, a vacuum heating furnace or the like can be used. The treatment temperature may be 400 ° C. or lower (for example, 300 to 400 ° C.), and the treatment time may be within several hours. In the heating step S26, so-called batch processing is possible, in which a large number of substrates 10 are put into the heating furnace at one time for processing, so the processing time per unit number is shortened. By the heat treatment in this heating step S26,
It is considered that extra residue appears on the surface of the substrate 10.

Therefore, in the subsequent surface layer removing step S27, the excess residue generated by the above heat treatment is removed together with the surface layer of the insulating film 12. In this surface layer removal step S27, a wet cleaning device using a hydrofluoric acid aqueous solution can be used. When using this wet cleaning device, the substrate 1 is placed in a cleaning tank that stores a hydrofluoric acid aqueous solution.
Soak 0. The liquid temperature of the hydrofluoric acid aqueous solution may be room temperature, and the concentration of hydrofluoric acid may be several% or less. Further, the processing time may be about 1 minute. By this hydrofluoric acid treatment, the insulating film 12
SiO _{2 in} the surface layer portion of is dissolved thinly. Therefore, the residue adhering to the surface of the insulating film 12 is removed by the insulating film 12 concerned.
The entire surface layer can be removed.

Then, the cathode electrode 1 in the FE element
An electrical test for a short circuit between 1 and the gate electrode 13 and a leakage current is performed to determine the quality (S28). The determination process by this electrical test is performed in the same manner as the determination process (S15) in the above embodiment.

If the result of the electrical test is "defective", the process returns to the previous cleaning step S22 and the same process is repeated. If "good" is determined, a series of processes is performed at that time. Is completed and the process proceeds to the next step. By the way, in the manufacturing flow shown in FIG. 5, when it is judged as “defective” by the electrical test and the process returns to the cleaning step S22, the heating process of the substrate 10 has been completed at the stage before that, so the heating process S
26 and the surface layer removing step S27 are not repeated. However, when the leakage current is judged to be “defective” twice or more in the electric test, the combination process of the heating step S26 and the surface layer removing step S27 is performed a plurality of times as necessary, and thus, You may make it improve the removal effect of a residue.

Thus, the F according to another embodiment of the present invention
In the method for manufacturing the E element, in addition to the effect of removing the organic and metal residues by the cleaning step S22 and the oxide removing step S23 as in the previous embodiment, the residue by the heating step S26 and the surface layer removing step 27 is added. As a result, the change (increase) in the leak current due to the heat treatment can be reliably prevented.

Further, in the manufacturing process of the flat-panel display device using the FE element, there is a sealing process for sealing the cathode substrate constituted of the substrate 10 and the anode substrate facing the cathode substrate in a vacuum state. Exhaust (degas) in this sealing process
The substrate 10 is heated as described above in the element manufacturing stage before that, and the excess residue that appears due to this is removed, so that the leakage current due to the heat treatment in the sealing process is increased. It is possible to prevent an increase in the power consumption and a change in the characteristics of the FE element.

[0041]

As described above, according to the present invention, a substrate on which elements are formed in the element forming step is washed with oxygen plasma or ozone in the washing step, and then is generated on the substrate by an oxidation reaction in the washing step. By removing the oxides in the oxide removing step, it is possible to efficiently remove unnecessary deposits such as organic compounds and metal particles remaining on the substrate from the substrate surface during the element formation stage. This makes it possible to reduce the occurrence of element defects and leakage current due to a short circuit between the cathode electrode and the gate electrode and to significantly reduce the leakage current value when manufacturing the field emission electron-emitting device.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a configuration of a flat-panel display device obtained by using a method for manufacturing a field emission electron-emitting device according to the present invention.

FIG. 2 is a flowchart showing a manufacturing procedure of the FE element according to the embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating an element state in a cleaning process.

FIG. 4 is a schematic diagram illustrating an element state in an oxide removing step.

FIG. 5 is a flowchart showing a method of manufacturing an FE element according to another embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a structure of a field emission electron-emitting device.

FIG. 7 is a diagram illustrating a manufacturing process of the field emission electron-emitting device.

[Explanation of symbols]

10 ... Substrate, 11 ... Cathode electrode, 12 ... Insulating film, 13
... gate electrode, 14 ... opening, 15 ... cavity, 16
… Cathode

Continued front page    (72) Inventor Takeshi Urazono             6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Soni             -Inside the corporation F-term (reference) 5C031 DD17 DD19

Claims (5)

[Claims] 1. A cathode electrode, an insulating film and a gate electrode are formed in a stacked state on a substrate, a cavity is formed in the insulating film through an opening formed in the gate electrode, and a cathode is formed in the cavity. An element forming step of forming a field emission type electron-emitting device formed by: a cleaning step of cleaning the substrate on which the element is formed by the element forming step with oxygen plasma or ozone; and a cleaning step generated on the substrate. A method of manufacturing a field emission electron-emitting device, comprising: an oxide removing step of removing oxide. 2. The method of manufacturing a field emission electron-emitting device according to claim 1, wherein the combination process including the cleaning process and the oxide removing process is performed a plurality of times. 3. The method according to claim 1, further comprising a heating step of heating the substrate after the oxide removing step and a surface layer removing step of removing a surface layer portion of the insulating film after the heating step. Of manufacturing a field emission type electron-emitting device of. 4. The method of manufacturing a field emission electron-emitting device according to claim 1, wherein the cathode formed in the cavity in the device forming step is a conical cathode. 5. The method of manufacturing a field emission electron-emitting device according to claim 3, wherein the combination process of the heating step and the surface layer removing step is performed a plurality of times.