JP3945049B2 - Method for manufacturing cold electron-emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a field emission type that emits cold electrons by a strong electric field. Method for manufacturing cold electron-emitting device About. 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 ultra-compact illumination source for an illumination lamp, and in particular, an array-like FEA (Field Emitter Array) constituting a flat display. Useful as an electron source of Method for manufacturing cold electron-emitting device About.
[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 in order to emit thermal electrons from the cathode of an electron gun, and requires a large volume in structure. There were problems such as.
[0003]
For this reason, there is a demand for a flat display that can use cold electrons instead of thermal electrons 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.
[0004]
As a structure of such a flat display using cold electrons, a structure in which minute electron-emitting devices are arranged 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 cold electron-emitting device utilizing a field emission phenomenon has been attracting attention. In this field emission type cold electron emission device, when the strength of the electric field applied to the material is increased, the width of the energy barrier on the surface of the material is gradually reduced according to the strength, and the electric field strength becomes a strong electric field of 107 V / cm or more. This makes use of the phenomenon that electrons in a substance can break through its energy barrier by the tunnel effect, and thus electrons are emitted from the substance. 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.
[0005]
As a general example of such a field emission type cold electron emission element, for example, a conical cold electron emission element having a sharp tip as shown in FIG. 4 can be exemplified. In this element, a conductive layer 42, an insulating layer 43, and a gate electrode 44 are sequentially stacked on an insulating substrate 41, and an opening B (gate hole) reaching the conductive layer 42 is formed in the insulating layer 43 and the gate electrode 44. ) Is formed.
[0006]
A conical emitter 45 having point-like protrusions is formed on the conductive layer 42 in the opening B so as not to contact the gate electrode 44. Among such conical emitters, Spindt-type emitters are widely known.
[0007]
An example of manufacturing a cold electron emission device having a Spindt-type emitter will be described with reference to FIGS.
[0008]
First, as shown in FIG. 5A, an insulating layer 53 and a gate electrode layer 54 are sequentially formed on an insulating substrate 51 on which a conductive layer 52 has been previously formed by a sputtering method, a vacuum evaporation method, or the like. Subsequently, a part of the insulating layer 53 and the gate electrode layer 54 is formed into a circular hole (opening B; gate hole) until the conductive layer 52 is exposed using a photolithography method and a reactive ion etching method (RIE). ) Is etched so that it opens.
[0009]
Next, as shown in FIG. 5B, a release layer 55 (lift-off layer) is formed by vapor-depositing a lift-off material only on the top and side surfaces of the gate electrode 54 by rotational oblique deposition. Al, MgO, etc. are often used as the lift-off material.
[0010]
Subsequently, as shown in FIG. 5C, a metal material for the emitter 56 is vapor-deposited on the conductive layer 52 from the perpendicular direction by normal anisotropic vapor deposition (vertical vapor deposition). At this time, as the deposition proceeds, the opening diameter of the gate hole B narrows, and at the same time, the conical emitter 56 is formed on the conductive layer 52 in a self-aligning manner. Deposition is performed until the gate hole B is finally closed. As the material of the emitter, Mo, Ni or the like can be used.
[0011]
Finally, as shown in FIG. 5D, the release layer 55 made of the lift-off material is removed by etching, and the gate electrode layer 54 is patterned as necessary to form a gate electrode. As a result, a cold electron emission device including a Spindt-type emitter can be obtained.
[0012]
The cold electron emission device having such a Spindt-type emitter has an advantage that a conical emitter can be easily formed in a self-aligning manner by anisotropic vapor deposition, and further, a wide range of emitter materials can be selected. .
[0013]
By the way, when applying a cold electron-emitting device using a microfabrication technology represented by a Spindt-type emitter to a flat display or the like in particular, a small fluctuation in the emission current from the emitter is necessary to obtain a high-quality image. Indispensable.
[0014]
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.
[0015]
As means for reducing such fluctuations in emission current, US Pat. No. 3,789,471 discloses a technique of providing a resistive layer between a conductive layer and an emitter in a Spindt emitter.
[0016]
A configuration example of a cold electron emission device having such a resistance layer will be described with reference to FIG.
[0017]
A conductive layer 62, a resistance layer 63, an insulating layer 64, and a gate electrode layer 65 (or an appropriately patterned gate electrode) are sequentially stacked on the insulating substrate 61, and the insulating layer 64 and the gate electrode layer 65 are stacked on the insulating substrate 61. An opening B (gate hole) reaching the resistance layer 63 is formed. A conical emitter 66 is formed on the resistance layer 63 in the opening B so as not to contact the gate electrode layer 65.
[0018]
In this case, the resistance layer 63 is electrically inserted in series between the conductive layer 62 and the emitter 66. This resistance layer 63 provides an effect of equalizing the current between the elements, further reduces a large current that leads to element destruction, and also reduces the fluctuation of the emission current in proportion to the resistance value of the resistance layer 63. It becomes possible. An appropriate specific resistance of the resistance layer 63 is 102 to 106 Ω · cm.
[0019]
On the other hand, silicon emitters using semiconductor integrated circuit manufacturing technology are also widely known. (Tech. Dig. IVMC., (1991) p26)
[0020]
An example of manufacturing a cold electron-emitting device having a silicon emitter will be described with reference to FIGS.
[0021]
First, as shown in FIG. 7A, a single crystal silicon substrate 71 is thermally oxidized to form a silicon oxide layer on the surface, and the silicon oxide layer is patterned into a circular shape using a photolithography method. A circular etching mask silicon oxide layer 72 is formed. The silicon oxide layer 72 also functions as a lift-off material (peeling layer) as will be described later. The diameter of the silicon oxide layer 72 substantially corresponds to the gate hole diameter.
[0022]
Next, as shown in FIG. 7B, the silicon substrate 71 is etched by a reactive ion etching method (RIE) under a condition with a high side etch rate to form an emitter 73.
[0023]
Subsequently, as shown in FIG. 7C, an emitter tip sharpening silicon oxide layer 74 is formed on the surfaces of the silicon substrate 71 and the emitter 73 by thermal oxidation. Due to the stress generated when the silicon oxide layer 74 is formed, the tip of the emitter 73 inside the silicon oxide layer 74 is easily sharpened.
[0024]
Then, as shown in FIG. 7D, an insulating layer 75 and a gate electrode layer 76 are stacked by anisotropic vapor deposition (vertical vapor deposition in a direction perpendicular to the single crystal silicon substrate 71).
[0025]
Finally, as shown in FIG. 7E, the etching mask silicon oxide layer 72 that also functions as a lift-off material is lifted off by etching, and the silicon oxide layer 74 on the surface of the emitter 73 is removed by etching. Then, the gate electrode layer 76 is patterned as necessary. As a result, a cold electron emission device including a silicon emitter is obtained.
[0026]
More recently, it has been shown that silicon current can be controlled at a high level by utilizing the properties of silicon as a semiconductor. (Jpn. Appl. Phys. Vol. 35 (1996) p6637)
[0027]
A silicon emitter having such a current control function is referred to as a MOSFET structure emitter. The configuration of the cold electron emission device including this MOSFET structure emitter will be described with reference to FIG.
[0028]
On the same plane of the p-type silicon substrate 81, a conical emitter 82 made of n-type silicon and an emitter wiring layer 84 are provided via an n-type silicon layer 83, and insulation is provided between the emitter 82 and the emitter wiring layer 84. A gate electrode layer 86 (or a gate electrode) is provided through the layer 85. That is, this emitter has a structure in which a MOSFET (metal-oxide-field-effect-transistor) structure is built in the cold electron emitter, the emitter wiring layer 84 of the cold electron emitter is the source of the MOSFET, and the emitter 82 is the drain. The gate electrode 86 functions as a gate, and the insulating layer 85 functions as a gate insulating layer.
[0029]
An example of manufacturing a cold electron-emitting device having a MOSFET structure emitter will be described with reference to FIGS.
[0030]
First, as shown in FIG. 9A, a single crystal p-type silicon substrate 91 is thermally oxidized to form a silicon oxide layer 92 on the surface, and the silicon oxide layer 92 is formed into a circular shape by using a photolithography method. By patterning, a circular silicon oxide layer 92 for an etching mask is formed. The silicon oxide layer 92 also functions as a lift-off material (peeling layer) as will be described later. The diameter of the silicon oxide layer 92 substantially corresponds to the gate hole diameter.
[0031]
Next, as shown in FIG. 9B, the p-type silicon substrate 91 is etched by a reactive ion etching method (RIE) under a condition with a high side etch rate to form an emitter 93.
[0032]
Subsequently, as shown in FIG. 9C, a silicon oxide layer 94 for sharpening the emitter tip and for the insulating layer is formed on the surfaces of the p-type silicon substrate 91 and the emitter 93 by thermal oxidation. Due to the stress generated when the silicon oxide layer 94 is formed, the tip of the emitter 93 inside the silicon oxide layer 94 is easily sharpened.
[0033]
9D, a gate electrode layer 95 is formed on the silicon oxide layer 92 and the silicon oxide layer 94 by anisotropic vapor deposition (vertical vapor deposition), and the gate electrode layer adjacent to the emitter 93 is formed. In 95, a circular hole pattern 98 for emitter wiring is formed using a photolithography method.
[0034]
Next, as shown in FIG. 9E, the etching mask silicon oxide layer 92 that also functions as a lift-off material is lifted off by etching, and the surface of the emitter 93 and the silicon oxide layer 94 in the circular hole pattern 98 are further removed. Etching is performed to form a gate hole B in the emitter 93 portion and an emitter wiring hole C in the circular hole pattern 98 portion.
[0035]
Subsequently, as shown in FIG. 9F, phosphorus is ion-implanted into the p-type silicon substrate 91 at the bottom of the emitter 93 and the emitter wiring hole C, and then diffusion annealing is performed to make the emitter 93 n-type. Then, an n-type silicon layer 96 is formed at the bottom of the emitter wiring hole C.
[0036]
Finally, as shown in FIG. 9G, a metal thin film 97 such as aluminum is formed as an electrode material for the emitter wiring and the gate wiring on the n-type silicon layer 96 at the bottom of the emitter wiring hole C, and then necessary. Accordingly, the gate electrode layer 95 is patterned. As a result, a cold electron-emitting device having a MOSFET structure emitter is obtained.
[0037]
In a cold electron emission device composed of a silicon emitter having such a MOSFET structure, although it can be easily manufactured in substantially the same manufacturing process as a conventional silicon emitter, a transistor control is realized by incorporating a MOS transistor in the device. Therefore, it is possible to obtain a very stable emission current, and to eliminate the generation of a large local current.
[0038]
[Problems to be solved by the invention]
However, in a cold electron emission device provided with a resistance layer for current stabilization, in order to obtain a sufficient current reduction characteristic with respect to a large local current, it is necessary to provide a larger resistance and a current fluctuation. However, there is a problem that it can only be reduced relatively with respect to the characteristics of the individual elements, and further, in principle, an increase in operating voltage cannot be avoided.
[0039]
On the other hand, a silicon emitter having a MOSFET structure equipped with a current control function can obtain a stable current at a very high level by transistor control. However, since a single crystal silicon substrate is required, the cost is reduced and the size is increased. There was a problem that it was difficult to increase the area.
[0040]
Further, in the cold electron emitting device according to the prior art, since the driving voltage of the device is a cold electron extraction voltage (operating voltage) applied to the gate electrode, a high voltage of several tens of volts or more is usually required, and a low-cost IC Since the circuit cannot be used, there is a problem that the drive circuit becomes expensive.
[0041]
The present invention is intended to solve the above-mentioned problems of the prior art, and suppresses a large local current without increasing the operating voltage by mounting a current control function on the element itself using a semiconductor thin film. At the same time, current fluctuation can be reduced to a minimum, and a glass substrate or the like can be used to facilitate cost reduction and area increase. Further, by providing a switching electrode separately from the gate electrode, the drive voltage can be reduced. An object of the present invention is to provide a field emission type cold electron emission device which can reduce the circuit cost and can be easily manufactured by a process equivalent to a conventional device which does not have a current control function, and a method for manufacturing the same.
[0052]
[Means for Solving the Problems]
A metal thin film layer, an insulating layer, and a gate electrode layer are sequentially stacked on the insulating substrate, and an opening is provided in the gate electrode layer and the insulating layer, so that the emitter does not contact the gate electrode layer in the opening. In the field emission type cold electron-emitting device formed on the metal thin film layer, the metal thin film layer is composed of the first conductive layer and the second conductive layer so that the conductive layers are not in direct contact with each other. A semiconductor thin film layer made of non-single crystalline silicon is provided on the same plane of the insulating substrate between at least the first conductive layer and the second conductive layer, A method of manufacturing a cold electron-emitting device, wherein a third conductive layer made of the same material as a gate electrode is provided on a semiconductor thin film via the insulating layer, and the insulating layer functions as a gate insulating layer. The (A) After forming a metal thin film layer on an insulating substrate, the metal thin film layer is patterned by photolithography to form the first conductive layer and the second conductive layer simultaneously so as not to be in direct contact with each other. Then, after forming a semiconductor thin film layer between the first conductive layer and the second conductive layer, an insulating layer and a gate electrode layer are sequentially formed; (b) the gate electrode layer and Forming a gate hole having a shape corresponding to the opening diameter of the gate electrode with respect to the insulating layer by photolithography until the second conductive layer is exposed; (c) on the gate electrode layer on which the gate hole is formed; A release layer is formed on the insulating substrate by a rotational oblique deposition method, and then an emitter material is formed on the gate electrode layer by an anisotropic deposition method in a direction perpendicular to the insulating substrate. Self-aligned on the second conductive layer A step of forming a cone-shaped emitter; (d) a step of peeling and removing the emitter material on the peeling layer formed on the gate electrode layer by peeling off the peeling layer from the gate electrode layer; And a step of patterning the gate electrode layer by photolithography to simultaneously form the gate electrode and the third conductive layer.
[0053]
The present invention Claim 2 The invention according to the above Claim 1 In the step (a) in the invention according to the invention, the method of manufacturing a cold electron-emitting device, wherein the semiconductor thin film layer is a hydrogenated amorphous silicon layer formed by a plasma enhanced CVD method.
[0054]
The present invention Claim 3 The invention according to the above Claim 1 In the step (a) in the invention according to the invention, the semiconductor thin film layer is a polysilicon layer formed by forming an amorphous silicon film by thermal CVD or plasma enhanced CVD, and then performing annealing treatment. It is a manufacturing method of an element.
[0055]
The present invention Claim 4 The invention according to the above Claim 1 In the step (a) according to the invention, after forming an ohmic layer on the metal thin film layer formed on the insulating substrate, the metal thin film layer and the ohmic layer are patterned by a photolithography method, Forming a first conductive layer and a second conductive layer on which an ohmic layer is formed; Claim 1 In the step (b) of the present invention, a channel hole having a shape corresponding to the opening diameter of the gate electrode is formed in the gate electrode layer and the insulating layer by photolithography until the second conductive layer is exposed. This is a method for manufacturing a cold electron-emitting device.
[0056]
The present invention Claim 5 The invention according to the above Claim 4 The ohmic layer is a method for manufacturing a cold electron-emitting device, wherein the ohmic layer is an n-type hydrogenated amorphous silicon layer formed by a plasma enhanced CVD method using at least a mixed gas of silane and phosphine as a reaction gas.
[0057]
[Action]
The present inventor has provided a first conductive layer (drain) and a second conductive layer (source) on an insulating substrate, and is made of non-single crystal silicon on the insulating substrate at least between the conductive layers. A thin film transistor (TFT) structure is realized by stacking a semiconductor thin film, a gate insulating layer, and a third conductive layer (gate). Further, a metal or metal oxide is formed on the first conductive layer (drain). Alternatively, by forming an emitter made of metal nitride, a thin film transistor can be easily formed in the vicinity of the emitter in the cold electron emission device without using a single crystal silicon substrate.
[0058]
As a result, the current can be stabilized and the driving voltage can be reduced by using the gate electrode of the thin film transistor as the switching electrode of the element. Furthermore, the gate electrode and the third conductive layer (TFT gate) are made of the same material as a single layer thin film. In addition, the present invention has been completed by finding an easy device structure and a manufacturing method by forming the insulating film from the same single layer film by sharing the TFT gate insulating layer.
[0059]
The cold electron-emitting device of the present invention has a TFT structure using non-single crystal silicon as a channel, and an emitter is made of metal, metal oxide or metal nitride on the drain electrode, so that it is formed on the insulating substrate. In addition, a highly controlled emission current can be obtained by the transistor, and low voltage driving can be realized by using the gate of the TFT as a switching electrode instead of the gate electrode (extraction electrode) of the emitter. Furthermore, by sharing the insulating layer with the TFT and processing and forming the TFT gate from the same thin film as the gate electrode, an element having the above current control function can be obtained by an easy manufacturing method.
[0060]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1A is a cross-sectional view of an example of the cold electron emission device of the present invention. As shown in the figure, in this cold electron emission element, a first conductive layer 2 and a second conductive layer 3 separated so as not to be in direct contact with each other are provided on an insulating substrate 1. A semiconductor thin film layer 4 made of non-single crystal silicon is disposed on the conductive layer 2 and the second conductive layer 3 and on the nonconductive portion A in the gap between the first conductive layer 2 and the second conductive layer 3. Has been. A third conductive layer 6 is formed on the insulating layer 5 on the semiconductor thin film layer 4 corresponding to the nonconductive portion A in the gap between the first conductive layer 2 and the second conductive layer 3. .
[0061]
An insulating layer 5 and a gate electrode 7 are sequentially stacked on the first conductive wire layer 2, and an emitter hole B reaching the semiconductor thin film layer 4 is provided in the gate electrode 7 and the insulating layer 5. Yes. A conical or frustoconical emitter 8 made of metal, metal oxide or metal nitride is formed on the first conductive layer 2 in the emitter hole B so as not to contact the gate electrode 7. ing. Here, the third conductive layer 6 and the gate electrode 7 are made of the same material.
[0062]
The first conductive layer 2, the second conductive layer 3, the semiconductor thin film layer 4, the insulating layer 5, and the third conductive layer 6 together form a thin film transistor structure (TFT) that operates in an n-channel enhancement mode. is doing. That is, the first conductive layer 2 functions as a drain, the second conductive layer 3 functions as a source, the semiconductor thin film layer 4 functions as a channel, the insulating layer 5 functions as a gate insulating layer, and the third conductive layer 6 functions as a gate. It is.
[0063]
FIG. 1B is a cross-sectional view of another example of the cold electron emission device of the present invention. As shown in the drawing, the first conductive layer 2 and the semiconductor thin film are obtained from the viewpoint of obtaining better current control characteristics. Between the layer 4 and between the second conductive layer 3 and the semiconductor thin film layer 4, an ohmic layer 10 (a layer having characteristics according to Ohm's law; usually a low resistance film, for example, n ⁺ -A-Si: H or the like) is preferably interposed.
[0064]
In the present invention, the insulating substrate 1 is used as a support substrate for a cold electron-emitting 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 and the like can be used, and among them, a glass substrate can be preferably used. A substrate in which an insulating layer is formed on the surface of single crystal silicon can also be used.
[0065]
In the present invention, the first conductive layer 2 functions as the drain of the TFT. As the material for the first conductive layer 2, a material having low wiring resistance and high adhesion to the underlying insulating substrate 1 is appropriate. Particularly preferable examples of such a material include Cr, Al, and a Cr laminated film.
[0066]
The thickness of the first conductive layer 2 is not particularly limited as long as sufficient wiring resistance and adhesion can be obtained, but is usually 0.01 to 1.0 μm, preferably 0.05 to 0.5 μm.
[0067]
The second conductive layer 3 functions as an emitter wiring layer and also functions as a TFT source. As a material for the second conductive layer 3, a material having a low wiring resistance and high adhesion to the underlying insulating substrate 1 is appropriate. Particularly preferable examples of such a material include Cr, Al, and a Cr laminated film.
[0068]
The thickness of the second conductive layer 3 is not particularly limited as long as sufficient wiring resistance and adhesion can be obtained, but is usually 0.01 to 1.0 μm, preferably 0.05 to 0.5 μm.
[0069]
The semiconductor thin film layer 4 functions as a channel of a thin film transistor (TFT). Such a semiconductor thin film layer 4 can be formed from a known material similar to a TFT widely used as a switching element of a liquid crystal display, and preferably, non-single crystal silicon can be used. Examples of such non-single crystal silicon include amorphous silicon (particularly non-doped hydrogenated amorphous silicon) and polysilicon.
[0070]
When a glass substrate is used as the insulating substrate 1, hydrogenated amorphous silicon or polysilicon by laser annealing can be preferably used as the semiconductor thin film layer 4.
[0071]
The thickness of the semiconductor thin film layer 4 is usually 0.01 to 2 [mu] m, preferably 0.03 to 0.7 [mu] m, so that it can operate as a TFT channel.
[0072]
The insulating layer 5 is a layer for electrically insulating the emitter 8 and the first conductive layer 2 from the gate electrode 7. Furthermore, it is used simultaneously for electrically insulating the semiconductor thin film layer 4 and the third conductive layer 6. That is, the insulating layer 5 in the present invention also functions as a gate insulating layer of the TFT.
[0073]
As such an insulating layer 5, anisotropic vapor deposition is desirable for forming it in a self-aligned manner, and silicon oxide by a reactive chimney resistance heating vapor deposition method using a mixed gas of ozone and oxygen as a reaction gas is particularly good. Insulating properties can be obtained, which is preferable. However, although the gate insulating layer of the TFT is separately formed depending on the manufacturing method, in such a case, the insulating layer 5 can be formed of a known material similar to the conventional TFT. For example, silicon nitride or silicon oxide formed by PECVD can be used.
[0074]
As for the thickness of the insulating layer 5, sufficient insulation is maintained between the emitter 8, the first conductive layer 2 or the semiconductor thin film layer 4 and the gate electrode 7 in the periphery of the emitter, and the gate of the TFT portion. In order to simultaneously function as an insulating layer, it is usually 0.01 to 2 μm, preferably 0.03 to 1 μm.
[0075]
The third conductive layer 6 functions as a TFT gate. As the material of the third conductive layer 6, a material having low wiring resistance and high adhesion to the lower insulating layer 5 is appropriate. Particularly preferable examples of such a material include Cr, Al, and a Cr laminated film. However, Cr and Nb are suitable in view of the fact that they are made of the same material as that of the gate electrode 7 in view of ease of production.
[0076]
The thickness of the third conductive layer 6 is not particularly limited as long as sufficient wiring resistance and adhesion can be obtained, but is usually 0.05 to 2.0 μm, preferably 0.05 to 0.5 μm.
[0077]
The gate electrode 7 is an electrode for concentrating a strong electric field on the emitter 8. As the material of the gate electrode 7, it is possible to use a material having a high melting point from the viewpoint of current resistance and having resistance to an etching solution used when forming the emitter, preferably Cr, W, Ta or Nb. Can be mentioned.
[0078]
The thickness of the gate electrode 7 can be appropriately determined as necessary, but is preferably 0.1 to 0.5 μm.
[0079]
The emitter 8 is a member that directly emits electrons from its surface, and is made of metal (eg, molybdenum, nickel, niobium, tungsten, silicon, etc.), metal oxide (eg, indium oxide, tin oxide, palladium oxide, etc.). Alternatively, metal nitride (for example, titanium nitride) can be used. Further, from the viewpoint of forming the emitter 8 in a self-aligning manner, a material that can be formed by vapor deposition is desirable.
[0080]
The thickness (height) of the entire emitter 8 can be appropriately determined as necessary, but is preferably 0.3 to 2 μm.
[0081]
The shape of the emitter 8 is preferably a conical shape or a cylindrical shape, or a truncated cone shape or a polygonal frustum shape.
[0082]
The ohmic layer 10 (resistive layer) is used to obtain an ohmic contact (contact holding electrical resistance) between the first conductive layer 2 and the second conductive layer 3 and the semiconductor thin film layer 4, or a better ohmic contact. Provided to get contact. The material of the ohmic layer 10 can be formed from a known material similar to a conventional TFT. For example, n-type hydrogenated amorphous silicon by PECVD can be used.
[0083]
The thickness of the ohmic layer 10 is not particularly limited as long as sufficient ohmic characteristics can be obtained, but is usually 0.01 to 1.0 μm, preferably 0.03 to 0.07 μm.
[0084]
Next, a method for manufacturing the cold electron-emitting device of the embodiment of the present invention shown in FIG. 1A will be described in detail with reference to FIG.
[0085]
Step (a)
As shown in FIG. 2A, first, after a metal thin film is formed on the insulating substrate 1 by a sputtering method or the like, a gap corresponding to the channel length of the TFT and a width corresponding to the channel width are formed by photolithography. The first conductive layer 2 and the second conductive layer 3 are formed by providing and patterning the non-conductive layer portion A (TFT channel), and the conductive layers 2 and 3 are insulative so as not to be in direct contact with each other. It is provided on the same plane of the substrate 1.
[0086]
Next, as shown in FIG. 2A, a semiconductor such as non-single crystal silicon is formed on the first conductive layer 2 and the second conductive layer 3 and on the insulating substrate 1 in the non-conductive layer portion A. A thin film material and an insulating material are formed in this order by the CVD method or the like, and the semiconductor thin film layer 4 and the insulating layer 5 are formed, respectively. Here, as the semiconductor thin film layer 4, a polysilicon film formed by annealing a hydrogenated amorphous silicon film formed by PECVD or an amorphous silicon film formed by thermal CVD or PECVD, for example, by laser annealing. Can be preferably used.
[0087]
As a method for forming the insulating layer 5, a silicon nitride film formed by PECVD using a mixed gas composed of silane and ammonia as a reaction gas can be preferably used.
[0088]
Subsequently, as shown in FIG. 2A, a metal thin film, which is a gate electrode material, is formed on the insulating layer 5 by using a normal film forming method such as a vapor deposition method or a sputtering method. 7 is formed.
[0089]
Step (b)
Next, as shown in FIG. 2B, an etching resist is applied on the gate electrode layer 7, and a portion of the etching resist corresponding to the upper side of the second conductive layer 3 is formed with an opening diameter corresponding to the gate hole by photolithography. After removing and patterning into a pattern of circular holes or polygonal holes having a pattern, the gate electrode layer 7, the insulating layer 5, and the semiconductor thin film layer 4 are etched until the second conductive layer 3 is exposed (for example, relithography). The emitter gate hole B (opening) is formed by active ion etching or reactive ion etching and wet etching.
[0090]
Step (c)
Subsequently, as shown in FIG. 2C, the gate is substantially formed on the gate electrode layer 7 and the periphery of the gate hole B for the emitter by performing oblique deposition on the insulating substrate 1 by the rotational oblique deposition method. A release layer 9 (lift-off layer) is formed only on the electrode layer 7. Next, as shown in FIG. 2C, the second conductive in the emitter gate hole B is formed by a normal anisotropic vapor deposition method (vertical vapor deposition method) from a direction perpendicular to the insulating substrate 1. While the emitter material is deposited on the layer 3 and the release layer 9, the conical emitter 8 is formed in the emitter gate hole B in a self-aligning manner. A vapor deposition film 8a is formed on the release layer 9 by vapor deposition of the emitter material so as to bridge and close the upper opening of the emitter gate hole B.
[0091]
Step (d)
Next, as shown in FIG. 2D, the peeling layer 9 is peeled off to form a vapor deposition film 8a made of the emitter material on the peeling layer 9 and a vapor deposition film 8a that bridges and closes the upper opening of the emitter gate hole B. Remove and remove.
[0092]
Step (e)
Finally, as shown in FIG. 2 (e), the gate electrode layer 7 is patterned by a photolithography method to form the gate electrode layer 7 (gate electrode) in a pattern, and at the same time, a third layer is formed immediately above the TFT channel. Conductive layer 6 is formed. As a result, the cold electron-emitting device of the present invention shown in FIG.
[0093]
Next, the method for manufacturing the cold electron-emitting device of the embodiment of the present invention shown in FIG. 1B will be described in detail with reference to FIG.
[0094]
Step (a)
First, as shown in FIG. 3A, a metal thin film is formed on the insulating substrate 1 by sputtering or the like to form a conductive layer, and an ohmic material is formed on the conductive layer to form an ohmic layer 10. After forming the first conductive layer on which the ohmic layer 10 is formed by patterning by providing a gap corresponding to the channel length of the TFT and a non-conductive layer portion A having a width corresponding to the channel width by photolithography. Layer 2 and second conductive layer 3 are formed. Here, as the ohmic material, an n-type hydrogenated amorphous silicon film formed by PECVD can be preferably used.
[0095]
Next, as shown in FIG. 3A, a semiconductor thin film such as non-single-crystal silicon is formed on the ohmic layer 10 and the non-conductive layer portion A on the first conductive layer 2 and the second conductive layer 3, respectively. A material and an insulating material are formed by a CVD method or the like, and the semiconductor thin film layer 4 and the insulating layer 5 are formed, respectively. Here, as the semiconductor thin film layer 4, a polysilicon film formed by annealing a hydrogenated amorphous silicon film formed by PECVD method or an amorphous silicon film formed by thermal CVD or PECVD method by laser annealing or the like, for example. Can be preferably used.
[0096]
As a method for forming the insulating layer 5, a silicon nitride film formed by PECVD using a mixed gas composed of silane and ammonia as a reaction gas can be preferably used.
[0097]
Subsequently, as shown in FIG. 3A, a metal thin film as a gate electrode material is formed on the insulating layer 5 by using a normal film forming method such as vapor deposition or sputtering, and the gate electrode layer 7 Form.
[0098]
Step (b)
Next, as shown in FIG. 3B, an etching resist is applied on the gate electrode layer 7, and a portion of the etching resist corresponding to the upper side of the second conductive layer 3 is opened by a photolithography method. After removing and patterning in the shape of a circular hole or polygonal hole having a pattern, the gate electrode layer 7, the insulating layer 5, the semiconductor thin film layer 4 and the ohmic layer 10 are etched until the second conductive layer 3 is exposed ( The emitter gate hole B (opening) is formed by, for example, reactive ion etching or etching using reactive ion etching and wet etching in combination.
[0099]
Step (c)
Subsequently, as shown in FIG. 3C, the gate is substantially formed on the gate electrode layer 7 and the periphery of the gate hole B for the emitter by performing oblique deposition on the insulating substrate 1 by the rotational oblique deposition method. A release layer 9 (lift-off layer) is formed only on the electrode layer 7. Next, as shown in FIG. 3C, the second conductive in the emitter gate hole B is formed from the direction perpendicular to the insulating substrate 1 by a normal anisotropic vapor deposition method (vertical vapor deposition method). While the emitter material is deposited on the layer 3 and the release layer 9, the conical emitter 8 is formed in the emitter gate hole B in a self-aligning manner. A vapor deposition film 8a is formed on the release layer 9 by vapor deposition of the emitter material so as to bridge and close the upper opening of the emitter gate hole B.
[0100]
Step (d)
Next, as shown in FIG. 3D, the peeling layer 9 is peeled to form a vapor deposition film 8a made of an emitter material on the peeling layer 9 and a vapor deposition film 8a that bridges and closes the upper opening of the emitter gate hole B. Remove and remove.
[0101]
Step (e)
Finally, as shown in FIG. 3E, the gate electrode layer 7 is patterned by a photolithography method to form the gate electrode layer 7 (gate electrode) in a pattern, and at the same time, a third layer is formed immediately above the TFT channel. Conductive layer 6 is formed. As a result, the cold electron-emitting device of the present invention shown in FIG. 1B is obtained.
[0102]
As described above, the cold electron-emitting device of the present invention has a TFT structure using non-single crystal silicon as a channel, and an emitter is made of metal, metal oxide or metal nitride on the drain electrode. Even on an insulating substrate, a highly controlled emission current can be obtained by a transistor, and driving by using the gate of the TFT as a switching electrode instead of the gate electrode (extraction electrode) of the emitter enables low voltage driving. Can be realized. Furthermore, by sharing the insulating layer with the TFT and processing and forming the TFT gate from the same thin film as the gate electrode, an element having the above current control function can be obtained by an easy manufacturing method.
[0103]
【Example】
A manufacturing example of the cold electron emission device of the present invention will be specifically described in the following examples.
[0104]
<Example 1>
Example of manufacturing cold electron-emitting device of the present invention in the mode shown in FIG. 1B (see FIG. 3))
Step (a)
First, after forming a conductive layer by forming Cr as a metal thin film on the insulating substrate 1 by a sputtering method to a thickness of 0.1 μm on the insulating substrate 1, n-type hydrogen is formed as an ohmic material by PECVD method. An ohmic layer 10 was formed by forming a hydrogenated amorphous silicon film with a thickness of 0.05 μm. Silane gas and phosphine gas (dope concentration 3000 ppm) were used as the reaction gas, and hydrogen was used as the dilution gas. The film was formed under the conditions of a total gas flow rate of 560 sccm, a gas pressure of 1 Torr, a substrate temperature of 350 ° C., and an RF power of 60 W. Subsequently, the ohmic layer 10 and the conductive layer covered thereby are patterned by photolithography to form a nonconductive layer portion A, and the first conductive layer 2 and the second conductive layer 2 separated by the nonconductive layer portion A are formed. A conductive layer 3 was formed, and a TFT channel was formed by the non-conductive layer portion A.
[0105]
Next, in FIG. 3A, a non-doped hydrogenated amorphous silicon film having a thickness of 0.1 μm is formed on the first conductive layer 2 and the second conductive layer 3 and on the non-conductive layer portion A by PECVD. The semiconductor thin film layer 4 was formed by film formation. A film was formed using silane gas as a reactive gas and hydrogen as a diluent gas under the conditions of a total gas flow rate of 300 sccm, a gas pressure of 1 Torr, a substrate temperature of 250 ° C., and an RF power of 60 W.
[0106]
Next, an insulating layer 5 was formed by depositing silicon nitride as an insulating material on the semiconductor thin film layer 4.
[0107]
Next, a gate electrode layer 7 was formed by sputtering Nb as a gate electrode material to a thickness of 0.2 μm on the insulating layer 5.
[0108]
Step (b)
Next, FIG. 3B shows an etching mask layer in which a circular etching pattern having a gate hole diameter of 1.2 μm is formed using a normal photolithography method, and then the gate electrode is formed by reactive ion etching. The layer 7, the insulating layer 5, the semiconductor thin film layer 4 and the ohmic layer 10 were etched until the second conductive layer 3 was exposed to form a gate hole B (opening). The etching conditions at this time were (introduced gas: SF660 sccm / power 100 W / gas pressure 4.5 Pa).
[0109]
Step (c)
Next, as shown in FIG. 3C, the release layer is formed only on the gate electrode layer 7 and the gate electrode layer 7 corresponding to the peripheral edge of the gate hole B by performing oblique evaporation on the insulating substrate 1 by the rotational oblique evaporation method. Aluminum (Al) was deposited as 9 (lift-off layer). Subsequently, the emitter 8 was formed in a conical shape in a self-aligning manner while depositing the emitter material by anisotropic vapor deposition (vertical vapor deposition) from the vertical direction with respect to the insulating substrate 1.
[0110]
Step (d)
Next, in FIG. 3D, the peeling layer 9 (Al) is peeled off by wet etching using an aqueous phosphoric acid solution, and the deposited film 8a made of the emitter material on the peeling layer 9 and the upper opening of the emitter gate hole B are formed. The vapor deposition film 8a that was cross-linked was peeled and removed.
[0111]
Step (e)
Finally, in FIG. 3E, the gate electrode layer 7 is patterned by photolithography to form the gate electrode layer 7 (gate electrode) in a pattern, and at the same time, the third conductive layer 6 is formed immediately above the TFT channel. Formed. As a result, the cold electron-emitting device of the present invention shown in FIG. 1B was obtained.
[0112]
<Test and test results>
The cold electron-emitting device of the present invention obtained in Example 1 was tested and evaluated as follows. That is, the distance between the emitter and the gate electrode of each element is 0.6 μm, the emitter height is 0.8 μm, and the ratio (L / W) of channel length (L) to channel width (W) as TFT parameters. The glass plate member having a transparent electrode (anode) coated with a phosphor is opposed to an element having a structure of 1/10) at a distance of 30 mm, and the gate electrode side has a positive polarity between the emitter electrode and the gate electrode. When the extraction voltage was applied, electrons could be emitted more stably and better than the emitter 8 at a switching voltage of about 10V.
[0113]
The typical emission characteristics obtained showed the current-voltage characteristics of the emitter 8 itself in the low electric field region, and the saturation characteristics according to the current-voltage characteristics of the TFT in the high electric field region. That is, in a high electric field region where the emission current exceeded the drain current value of the TFT, a saturation current region was obtained by current transistor control, and a stable emission current was obtained at an extraction voltage of 110 V or more. In addition, an emission current was obtained when the gate voltage of the TFT was 15 V or higher, and switching was possible at a low voltage.
[0114]
【The invention's effect】
According to the present invention, by forming an emitter with a metal having a TFT structure, an emission current highly controlled by a transistor can be obtained even on an insulating substrate, and a switching electrode is provided separately from the gate electrode. Thus, it is possible to obtain a cold electron emission device that easily realizes a reduction in driving voltage. Furthermore, by sharing the insulating layer with the TFT and processing and forming the TFT gate from the same thin film as the gate electrode, an element having a current control function can be obtained by an easy manufacturing method.
[0115]
Therefore, a cold electron-emitting device that has high current stability and can be driven at a low voltage can be obtained on a glass substrate that can be increased in area at low cost. Furthermore, 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 cold electron emission device of the present invention.
FIG. 2 is a manufacturing process diagram of the cold electron emission device of the present invention.
FIG. 3 is a manufacturing process diagram of another cold electron emission device of the present invention.
FIG. 4 is a cross-sectional view of a conventional cold electron emission device.
FIG. 5 is a manufacturing process diagram of a conventional cold electron-emitting device.
FIG. 6 is a cross-sectional view of another conventional cold electron emission device.
FIG. 7 is a cross-sectional view of a conventional cold electron emitter.
FIG. 8 is a manufacturing process diagram of another conventional cold electron emission device.
FIG. 9 is a manufacturing process diagram of another conventional cold electron emission device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... 1st conductive layer 3 ... 2nd conductive layer 4 ... Semiconductor thin film layer
5 ... Insulating layer 6 ... Third conductive layer 7 ... Gate electrode layer 8 ... Emitter 9 ... Release layer
10 ... Ohmic layer
41 ... Insulating substrate 42 ... Conductive layer 43 ... Insulating layer 44 ... Gate electrode
45 ... Emitter
51 ... Insulating substrate 52 ... Conductive layer 53 ... Insulating layer 54 ... Gate electrode
55 ... Lift-off material 56 ... Emitter
61 ... Insulating substrate 62 ... Conductive layer 63 ... Resistive layer 64 ... Insulating layer
65 ... Gate electrode 66 ... Emitter
71 ... Insulating substrate 72 ... Conductive layer 73 ... Emitter 74 ... Silicon oxide layer
75 ... Insulating layer 76 ... Gate electrode
81 ... p-type silicon substrate 82 ... emitter 83 ... n-type silicon layer
84 ... Emitter wiring layer 85 ... Insulating layer 86 ... Gate electrode
91 ... p-type silicon substrate 92 ... silicon oxide layer 93 ... emitter
94 ... Silicon oxide layer 95 ... Gate electrode 96 ... N-type silicon layer
97 ... Metal thin film
A ... TFT channel (non-conductive layer part) B ... Emitter gate hole (opening)

Claims (5)

A metal thin film layer, an insulating layer, and a gate electrode layer are sequentially stacked on the insulating substrate, and an opening is provided in the gate electrode layer and the insulating layer, so that the emitter does not contact the gate electrode layer in the opening. In the field emission type cold electron-emitting device formed on the metal thin film layer, the metal thin film layer is composed of the first conductive layer and the second conductive layer so that the conductive layers are not in direct contact with each other. A semiconductor thin film layer made of non-single crystalline silicon is provided on the same plane of the insulating substrate between at least the first conductive layer and the second conductive layer, A method of manufacturing a cold electron-emitting device, wherein a third conductive layer made of the same material as a gate electrode is provided on a semiconductor thin film via the insulating layer, and the insulating layer functions as a gate insulating layer. Te, (a) an insulating substrate After forming the metal thin film layer, the metal thin film layer is patterned by photolithography to form the first conductive layer and the second conductive layer at the same time so as not to be in direct contact with each other. Subsequently, the first conductive layer is formed. A step of sequentially forming an insulating layer and a gate electrode layer after forming a semiconductor thin film layer between the layer and the second conductive layer; and (b) a photolithography method for the gate electrode layer and the insulating layer. (C) forming a gate hole having a shape corresponding to the opening diameter of the gate electrode until the second conductive layer is exposed, and (c) rotating obliquely with respect to the insulating substrate on the gate electrode layer in which the gate hole is formed. After the release layer is formed by the lateral evaporation method, the emitter material is deposited on the second conductive layer by the anisotropic evaporation method in the direction perpendicular to the insulating substrate from the gate electrode layer. A conical emitter (D) a step of peeling and removing the emitter material on the peeling layer formed on the gate electrode layer by peeling off the peeling layer from the gate electrode layer; A method of manufacturing a cold electron-emitting device, including a step of simultaneously forming a gate electrode and a third conductive layer by patterning by a lithography method. 2. The method of manufacturing a cold electron-emitting device according to claim 1 , wherein in the step (a), the semiconductor thin film layer is a hydrogenated amorphous silicon layer formed by a plasma enhanced CVD method. 2. The cold electron according to claim 1 , wherein, in the step (a), the semiconductor thin film layer is a polysilicon layer formed by forming an amorphous silicon film by a thermal CVD method or a plasma enhanced CVD method and then performing an annealing process. A method for manufacturing an emitting device. In the step (a), after an ohmic layer is formed on the metal thin film layer formed on the insulating substrate, the ohmic layer is formed by patterning the metal thin film layer and the ohmic layer by a photolithography method. A first conductive layer and a second conductive layer are formed, and then, in the step (b), the gate electrode layer and the insulating layer are adapted to the opening diameter of the gate electrode by photolithography. 2. The method of manufacturing a cold electron emission device according to claim 1 , wherein the channel hole having the shape is formed until the second conductive layer is exposed. 5. The method of manufacturing a cold electron-emitting device according to claim 4 , wherein the ohmic layer is an n-type hydrogenated amorphous silicon layer formed by a plasma enhanced CVD method using at least a mixed gas of silane and phosphine as a reaction gas.

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