JP4693980B2 - Method for manufacturing field electron emission device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a field emission type electron-emitting element that emit electrons by strong electric field. More specifically, as an electron generation source or electron gun for an optical printer, an electron microscope, an electron beam exposure apparatus or the like, or as an illumination lamp ultra-compact illumination source, in particular, an array of FEA (Field Emitter Array) constituting a flat display. a method for producing a useful field electron emission element as an electron generating source.
[0002]
[Prior art]
Conventionally, a cathode ray tube has been widely used as an electronic display device. However, the cathode ray tube consumes a large amount of energy to emit thermal electrons from the cathode of an electron gun, and requires a large volume in structure. There was a problem.
For this reason, there is a demand for a flat display that can use cold electrons instead of thermoelectrons to reduce energy consumption as a whole, and further downsize the device itself. Realization of high-speed response and high resolution is strongly demanded for the type display.
[0003]
As a structure of a flat display using such cold electrons, a structure in which minute electron-emitting devices are formed in an array in a high vacuum flat plate cell is considered promising. As an electron-emitting device used for this purpose, a field-emission type electron-emitting device using a field emission phenomenon has attracted attention.
In this field emission type electron-emitting device, when the strength of the electric field applied to the substance is increased, the width of the energy barrier on the surface of the substance is gradually narrowed according to the strength, and the electric field strength is 10 ⁷ V / cm or more. Then, the electrons in the material can break through the energy barrier due to the tunnel effect, and the phenomenon that electrons are emitted from the material is used. In this case, since the electric field follows Poisson's equation, if a portion where the electric field concentrates is formed on the member (emitter) that emits electrons, cold electrons can be efficiently emitted with a relatively low extraction voltage.
[0004]
As a general type of such a field emission type electron-emitting device (field-electron emitting device), as shown in FIG. 4, a conical field-electron emitting device having a sharp tip can be exemplified. In this element, a conductive layer 52, an insulating layer 53, and a gate electrode 54 are sequentially stacked on an insulating substrate 51, and an opening A reaching the conductive layer 52 is formed in the insulating layer 53 and the gate electrode 54. Has been. A conical emitter 55 having point-like protrusions is formed on the conductive layer 52 in the opening A so as not to contact at least the gate electrode 54.
[0005]
Among such conical emitters, Spindt-type emitters are widely known.
A manufacturing process sectional view of a field electron emission device including a Spindt-type emitter will be described with reference to FIGS. 5 (a) to 5 (d).
First, as shown in FIG. 5A, an insulating layer 63 and a gate electrode 64 are sequentially formed on an insulating substrate 61 on which a conductive layer 62 has been formed in advance by sputtering or vacuum evaporation. Subsequently, a circular hole (gate hole) is opened in part of the insulating layer 63 and the gate electrode 64 by using a photolithography method and a reactive ion etching method (RIE) until the conductive layer 62 is exposed. Etch into.
[0006]
Next, as shown in FIG. 5B, a release layer 65 is formed only on the upper surface and side surfaces of the gate electrode 64 by oblique deposition. As the material of the peeling layer 65, Al, MgO or the like is often used.
Subsequently, as shown in FIG. 5C, a metal material for the emitter 66 is deposited on the conductive layer 62 by normal anisotropic deposition from the perpendicular direction. At this time, as the deposition proceeds, the opening diameter of the gate hole is narrowed, and at the same time, the conical emitter 66 is formed on the conductive layer 62 in a self-aligning manner. Deposition is performed until the gate hole is finally closed. As the material of the emitter, Mo, Ni or the like is used.
[0007]
Finally, as shown in FIG. 5D, the peeling layer 65 is peeled off by etching, and the gate electrode 64 is patterned as necessary. As a result, a field electron emission device including a Spindt-type emitter is obtained.
A field electron emission device having such a Spindt-type emitter has the advantage that a cone-shaped emitter can be easily formed in a self-aligning manner by anisotropic vapor deposition, and that a wide range of emitter materials can be selected. .
[0008]
By the way, when a field electron emission device using a microfabrication technique represented by a Spindt-type emitter is applied to a flat display or the like in particular, the fluctuation of the emission current from the emitter is small to obtain high quality image quality. Indispensable.
In addition, the fluctuation of the emission current can be reduced to some extent by integrating the emitter. This is because the influence of variations in emission characteristics among individual emitters is reduced by integration. However, since this method merely apparently averages the emission current from each emitter, it is impossible to suppress an abnormally large emission current that appears locally.
[0009]
As means for reducing such fluctuations in emission current, US Pat. No. 3,789,471 discloses a technique of providing a resistance layer between a conductive layer and an emitter in a Spindt emitter.
A configuration example of an electron-emitting device having such a resistance layer will be described with reference to FIG.
[0010]
A conductive layer 72, a resistance layer 73, an insulating layer 74, and a gate electrode 75 are sequentially stacked on the insulating substrate 71, and an opening A reaching the resistance layer 73 is formed in the insulating layer 74 and the gate electrode 75. ing. A conical emitter 76 is formed on the resistance layer 73 in the opening A so as not to contact at least the gate electrode 75.
[0011]
In this case, the resistance layer 73 is electrically inserted between the conductive layer 72 and the emitter 76 in series. The resistance layer 73 has an effect of making the current between the elements uniform, further reduces a large current that leads to element destruction, and also reduces fluctuations in the emission current in proportion to the resistance value of the resistance layer 73. It becomes possible.
As the resistance layer 73, a silicon thin film formed by vapor deposition, sputtering, or PECVD is generally used. The specific resistance of the resistance layer 73 is about 10 ⁵ Ω · cm.
[0012]
[Problems to be solved by the invention]
However, in a field electron emission device in which a silicon thin film formed by vapor deposition and sputtering is used as a resistance layer for current stabilization, a large number of structural defects exist in the silicon thin film, which is a resistance layer. Value design and control is difficult. Therefore, the control range of the emission current has been limited.
[0013]
Further, in a field electron emission device in which a silicon thin film material formed by PECVD (plasma-enhanced chemical vapor deposition) is applied to a resistance layer, the silicon thin film as the resistance layer contains hydrogen that terminates defects. The resistance value of the silicon thin film can be controlled to some extent by changing the doping amount of the impurity, but the temperature dependency and light dependency of the resistance value are large, and the current control characteristics of the electron-emitting device change depending on the operating environment. There's a problem.
[0014]
In view of the above situation, the present invention can design and control a resistance value by using a material mainly composed of carbon as a resistance layer, and has little change due to temperature and light, that is, has high environmental resistance. further it can be used a glass base plate is formed at a low temperature, and an object thereof is to provide a method for producing low-cost and large area also easy field electron emission element.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides
[1] In the method for manufacturing a field emission device, a resistive material consisting of a thin film composed mainly of emitter wiring material及beauty-carbon made of a metal thin film on an insulating substrate sequentially deposited, emitter wiring material layer, resistance After sequentially forming the material layer, the emitter wiring material layer and the resistance material layer are patterned by a photolithography method to form the emitter wiring layer and the resistance layer in sequence, and an insulating material and a metal thin film are formed on the resistance layer. After sequentially forming a gate electrode material, a resist is applied, and the resist is formed into a circular hole having a gate opening diameter by photolithography, and then the gate electrode material layer and the insulating layer are formed by reactive ion etching. Etching the material layer until the resistive layer is exposed to form a gate hole and forming a gate electrode and an insulating layer; Said depositing a release layer material only to the gate electrode upper surface and side surfaces by vapor deposition, forming a peeling layer, by an anisotropic deposition in a direction perpendicular to the insulating substrate, the emitter to the gate bore A method of manufacturing a field electron emission device comprising: forming a material and forming an emitter in a self-aligning manner; and removing the release layer and simultaneously removing the emitter material on the gate electrode; The insulating substrate is a glass substrate, and the temperature of the glass substrate is set to 150 ° C. or lower, and the low temperature of the diamond-like carbon thin film as the resistive material layer is formed by PECVD using at least a mixed gas of methane and nitrogen as a reaction gas. A film is formed .
[0016]
[ 2 ] The method of manufacturing a field electron emission device according to [ 1 ], wherein a high frequency (RF) plasma is used in the PECVD method.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of a field electron emission device showing an embodiment of the present invention.
As shown in this figure, in this field electron emission device, an emitter wiring layer 2, a resistance layer 3 made of a carbon-based thin film, an insulating layer 4 and a gate electrode 5 are sequentially laminated on an insulating substrate 1. Has a structure. The gate electrode 5 and the insulating layer 4 are provided with an emitter hole A reaching the resistance layer 3, and the emitter 6 does not contact the gate electrode 5 on the resistance layer 3 in the emitter hole A. It is formed as follows.
[0018]
Here, the insulating substrate 1 is used as a supporting insulating substrate for a field electron emission device, and an insulating substrate that can be easily increased in area can be preferably used. As such an insulating substrate, a glass substrate, a ceramic substrate, a quartz substrate, or the like can be used. Note that a substrate in which an insulating film is formed on the surface of single crystal silicon can also be used.
[0019]
The emitter wiring layer 2 is formed of a material having low wiring resistance and good adhesion to the insulating substrate 1. For example, it is formed from a material having resistance to an etching gas used for RIE used when forming the emitter 6 to be described later, or an etching solution used during lift-off. This is because the emitter wiring layer 2 functions as an etching stopper when the emitter 6 is formed. As such a material, Cr or an Al / Cr laminated film is particularly preferable.
[0020]
The thickness of the emitter wiring layer 2 is not particularly limited as long as sufficient wiring resistance and adhesion can be obtained, but is usually 0.50 to 0.5 μm, preferably 0.1 to 0.3 μm.
The resistance layer 3 is formed from a material mainly composed of carbon. Preferably, a diamond-like carbon material, more preferably a diamond-like carbon material doped with an impurity such as nitrogen is used.
[0021]
By providing the resistance layer 3, in order to perform good current control of the field electron emission device using the negative feedback action, the resistance value of the resistance layer 3 can be easily designed and matched to the current level to be obtained. It is desirable to be able to control and produce the element. In addition, it is necessary to use a material whose control characteristics do not change even under the influence of temperature, light, etc., that is, high environmental resistance. From the viewpoint of such an action, it can be realized by configuring the resistance layer 3 with a material mainly composed of carbon.
[0022]
In the element manufacturing process, the resistance layer 3 has good adhesion to the insulating substrate 1 and the emitter wiring layer 2 and is used for RIE used for forming an emitter hole A to be described later. It is required to have resistance to the etching gas or the etching solution used when removing the release layer. This resistive layer 3 in order to function as an etching stopper during the formation of the emitter hole A. From such a process point of view, it is possible to satisfy the requirements by using a material mainly composed of carbon.
[0023]
Further, when a diamond-like carbon material by PECVD method is used as the resistance layer 3, the substrate temperature during film formation can be easily formed at a low temperature of 150 ° C. or lower, so that a low-cost glass substrate or plastic can be used as the insulating substrate 1. A substrate can be used.
The thickness of the resistance layer 3 is not particularly limited as long as appropriate resistance and adhesion can be obtained, but is usually 0.3 to 2.0 μm, preferably 0.5 to 1.5 μm.
[0024]
The insulating layer 4 is a layer for electrically insulating the emitter wiring layer 2 and the gate electrode 5. Such an insulating layer 4 can be formed of a known material used as an insulating layer of a field electron emission device.
The insulating layer 4 may have a thickness as long as sufficient insulation is maintained between the emitter wiring layer 2 and the gate electrode 5, for example, 0.2 to 2.0 μm, preferably 0.3 to 0.7 μm. is there.
[0025]
The gate electrode 5 functions as an electrode for concentrating a strong electric field on the emitter 6. The material of the gate electrode 5 is preferably a refractory metal from the viewpoint of current resistance and preferably resistant to the etching solution used when forming the emitter, such as Cr, W, Ta or Nb. it can. Among them, it is preferable to use Nb from the viewpoint of adhesion with the base.
[0026]
The thickness of the gate electrode 5 can be appropriately determined as necessary, but is 0.1 to 0.5 μm.
The emitter 6 is a member that directly emits electrons from its surface, and is made of metal (for example, molybdenum, nickel, niobium, tungsten, silicon, etc.), metal oxide (for example, indium oxide, tin oxide, palladium oxide, etc.). Alternatively, metal nitride (for example, titanium nitride) can be used. Furthermore, from the viewpoint of forming the emitter 6 in a self-aligning manner, a material that can be formed by vapor deposition is desirable.
[0027]
The thickness (height) of the entire emitter 6 can be appropriately determined as necessary, but is usually preferably 0.3 to 2.0 μm.
Further, the shape of the emitter 6 is preferably a conical shape.
Next, a method for manufacturing a field electron emission device according to an embodiment of the present invention will be described in detail with reference to FIG.
[0028]
(1) First, as shown in FIG. 2A, after a metal thin film is formed as an emitter wiring material on the insulating substrate 1 by sputtering or the like, subsequently, a material mainly composed of carbon as a resistance material, For example, a diamond-like carbon material is formed by PECVD using RF plasma. Here, methane is used as the reaction gas, and hydrogen is used as the dilution gas. Moreover, the resistance of the film material can be controlled by introducing nitrogen as an additive gas. Next, the emitter wiring layer 2 and the resistance layer 3 are formed by photolithography.
[0029]
(2) Next, as shown in FIG. 2B, the insulating layer 4 is formed. As a method for forming an insulating material, a mixed gas composed of silane and ammonia is used as a reaction gas. A silicon nitride film formed by PECVD is preferable. Then, using conventional film forming method such as vapor fusing method or a sputtering method, a metal thin film as a material of the gate electrode 5. Next, patterning is performed into a circular hole having an opening diameter of the gate by photolithography, and the gate electrode material and the insulating material are etched until the resistance layer 3 is exposed to form the emitter hole A.
[0030]
(3) Next, as shown in FIG. 2 (c), the peeling layer 7 is formed substantially only on the gate electrode material by performing oblique deposition on the insulating substrate 1 .
(4) Next, as shown in FIG. 2D, an emitter material is deposited on the resistance layer 3 and the release layer 7 by normal anisotropic deposition from a direction perpendicular to the insulating substrate 1 . However, the emitter 6 is formed in a self-aligning manner.
[0031]
(5) Next, as shown in FIG. 2E, the emitter material on the release layer 7 is peeled off at the same time as the release layer 7 is released. Finally, the gate electrode material is patterned by photolithography to form the gate electrode 5. Thereby, the field electron-emitting device shown in FIG. 1 is obtained.
As described above, in the field electron emission device of the present invention, the emission current can be easily and highly controlled by configuring the resistance layer with a material mainly composed of carbon.
[0032]
【Example】
The production example of the field electron emission device of the present invention will be specifically described in the following examples.
Example [Production Example of Field Electron Emission Device of Aspect of the Present Invention (see FIG. 2)]
(1) First, as shown in FIG. 2A, Cr was deposited as a metal thin film on the insulating substrate 1 to a thickness of 0.15 μm by sputtering. Subsequently, a diamond-like carbon thin film having a thickness of 0.5 μm was formed by PECVD using RF plasma as a resistive material layer. A film was formed using methane gas and nitrogen gas (nitrogen partial pressure of 30%) as the reaction gas under the conditions of a gas pressure of 10 mTorr, an anode electrode temperature of 100 ° C., and a self-bias of 1300 V. Subsequently, the emitter wiring layer 2 and the resistance layer 3 were patterned by photolithography.
[0033]
(2) Next, as shown in FIG. 2B, silicon nitride as an insulating material was formed to a thickness of 0.7 μm by PECVD to form an insulating layer 4 . Here, silane gas and ammonia gas were used as the reaction gas, and hydrogen was used as the dilution gas, and the film was formed under the conditions of a total gas flow rate of 540 sccm, a gas pressure of 1 Torr, a substrate temperature of 400 ° C., and an RF power of 150 W. Subsequently, Nb was sputtered with a thickness of 0.3 μm as a gate electrode material. Next, after a circular hole pattern having a gate opening diameter of 1 μm is formed by using a normal photolithography method to obtain an etching mask layer, the gate electrode material and the insulating material are exposed by reactive ion etching until the resistance layer 3 is exposed. Etched. Etching conditions at this time were introduced gas: SF _{6 60} sccm / power 100 W / gas pressure 4.5 Pa.
[0034]
(3) Next, as shown in FIG. 2C, Al was deposited as the release layer 7 only on the gate electrode material by performing oblique deposition on the insulating substrate 1. Subsequently, the emitter 6 was formed in a self-aligning manner while depositing an emitter material by anisotropic vapor deposition from a direction perpendicular to the insulating substrate 1.
(4) Next, as shown in FIG. 2 (d), Al of the release layer 7 was wet-etched using an aqueous phosphoric acid solution, and was peeled off together with the upper emitter material.
[0035]
(5) Finally, as shown in FIG. 2 (e), the gate electrode material was patterned by photolithography to form the gate electrode 5.
Thereby, a field electron emission device having the structure shown in FIG. 1 was obtained.
“Evaluation 1: Resistance layer film characteristics [see FIGS. 3A and 3B]”
The diamond-like carbon material thin film, which is the resistance layer obtained in the above example, was tested and evaluated as follows.
[0036]
Diamond-like carbon was deposited on the silicon substrate on which the thermal oxide film was formed under the same film forming conditions as the resistance layer formation, and the resistivity and sheet resistance were measured by a four-probe method.
FIG. 3A shows a change in resistivity when the nitrogen partial pressure is changed. The resistivity of diamond-like carbon not containing nitrogen is about 10 ¹³ Ωcm, but it can be seen that by introducing nitrogen, the resistivity decreases to 10 ⁻¹ Ωcm, and the resistivity can be controlled in a wide range.
[0037]
FIG. 3 (b) shows the temperature dependence of the resistivity of diamond-like carbon deposited at different anode electrode temperatures. It can be seen that the resistivity temperature change from low temperature to room temperature is smaller than that of amorphous silicon and the like, and the stability against temperature fluctuation is high.
"Evaluation 2: Field electron emission device characteristics"
The field electron emission devices obtained in the above examples were tested and evaluated as follows. That is, a glass plate member having a transparent electrode (anode) coated with a phosphor on an element having a structure in which the distance between the emitter and gate electrodes of each element integrated with 1000 tips is 0.6 μm and the emitter height is 1 μm. When the extraction voltage is applied between the emitter electrode and the gate electrode so that the gate electrode side has a positive polarity, the electron is satisfactorily and stably applied with a current of 100 μA (extraction voltage 100 V) at a switching voltage of about 30 V. Could be released.
[0038]
In addition, this invention is not limited to the said Example, A various deformation | transformation is possible based on the meaning of this invention, and these are not excluded from the scope of the present invention.
[0039]
【The invention's effect】
As described above in detail, in the present invention, the resistance layer is made of a material containing carbon as a main component, for example, a diamond-like carbon material. Then, since the temperature characteristic is more stable than that of amorphous silicon or the like, it is possible to obtain a field electron emission device having an emission current characteristic that is easily and highly controlled.
[0040]
Therefore, a field electron emission device with high current stability can be obtained on a glass substrate capable of increasing the area at low cost. Further, when applied to a flat panel display, a high-speed, high-definition image can be obtained with low power consumption.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a field electron emission device of the present invention.
FIG. 2 is a manufacturing process diagram of a field electron emission device of the present invention.
FIG. 3 is an example of temperature dependence of electrical characteristics of a resistance layer included in the field electron emission device of the present invention.
FIG. 4 is a cross-sectional view of a conventional field electron emission device.
FIG. 5 is a manufacturing process diagram of a conventional field electron emission device.
FIG. 6 is a diagram illustrating a configuration example of an electron-emitting device having a conventional resistance layer.
[Explanation of symbols]
1 Insulating substrate 2 Emitter wiring layer 3 Resistance layer 4 Insulating layer (silicon nitride film)
5 Gate electrode 6 Emitter 7 Release layer A Emitter hole

Claims (2)

(A) a thin film composed mainly of emitter wiring material及beauty-carbon made of a metal thin film on an insulating substrate a resistive material successively deposited, emitter wiring material layer, after the resistive material layer are sequentially formed, wherein Patterning the emitter wiring material layer and the resistance material layer by photolithography, and sequentially forming the emitter wiring layer and the resistance layer;
(B) An insulating material and a gate electrode material made of a metal thin film are sequentially formed on the resistance layer, and subsequently a resist is applied, and the resist is formed into a circular hole having a gate opening diameter by photolithography. Forming the gate electrode material layer and the insulating material layer by reactive ion etching until the resistance layer is exposed to form a gate hole and forming the gate electrode and the insulating layer;
(C) depositing a release layer material only on the top and side surfaces of the gate electrode by oblique deposition, and forming a release layer;
(D) forming an emitter material in the gate hole by anisotropic vapor deposition in a direction perpendicular to the insulating substrate, and forming an emitter in a self-aligning manner;
(E) the same time to remove the peeling layer, and a step of flaking the emitter material on the gate electrode to a method for producing facilities to electric field electron emission device,
(F) The insulating substrate is a glass substrate, and the temperature of the glass substrate is set to 150 ° C. or less, and diamond-like carbon as the resistance material layer is formed by PECVD using a mixed gas of at least methane and nitrogen as a reaction gas. A method of manufacturing a field electron emission device, comprising performing a low-temperature film formation of a thin film. 2. The method of manufacturing a field electron emission device according to claim 1 , wherein a high frequency (RF) plasma is used in the PECVD method.

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