JP2008091263A - Field electron emission device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field electron emission device capable of preventing deterioration of tips of carbon fiber type emitters without being influenced by oxygen in emitting electrons; and its manufacturing method. <P>SOLUTION: A cathode electrode 2 is formed on a glass substrate 1, and an insulating film 3 having an opening is formed on the cathode electrode 2. A gate electrode 4 having an opening as well is formed on the insulating film 3. Carbon fibers 5 are formed on the cathode electrode 2 exposed in the opening. Each surface of the carbon fibers 5 used as the emitters is covered with a carbon film 5a, including the tips thereof. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a carbon fiber type field electron emission device using carbon nanotubes and the like and a method for manufacturing the same.

  A field electron emission device is used as an electron emission source of an FED (Field Emission Display), STM (Scanning Tunneling Microscope), and electron drawing device. Recently, carbon fiber emitters such as carbon nanotubes (CNT), carbon nanofibers (CNF), and graphite nanofibers (GNF) having high mechanical strength and excellent electrical performance are used in this field electron emission device. .

  A field electron emission device having a carbon fiber type emitter has, for example, a cathode electrode formed on a substrate at a lower portion and an electron extraction portion at an upper portion as shown in Patent Document 1 and Patent Document 2, for example. A gate electrode is used as an electrode, and an insulating layer is provided between the cathode electrode and the gate electrode. An emitter is formed inside the emitter hole exposing a part of the cathode electrode.

When a voltage is applied between the cathode electrode and the gate electrode, a large electric field is applied to the tip of the emitter, causing electron emission. The carbon fiber type field electron emission device has an advantage that the tip of the emitter is nano-order thin and has a high aspect ratio, so that electric field concentration occurs at the tip of the emitter at a relatively low voltage, and it can be driven at a low voltage. is there.
JP 2003-59436 A JP 2006-49322 A

However, since the emitter material in the conventional field electron emission device is composed of carbon (carbon), there is a defect in the graphite constituting the carbon fiber, and when the degree of vacuum in the device is poor, Oxidation occurs due to the influence of oxygen during electron emission, and part of the emitter material becomes CO ₂ , CO, and carbon oxide, which are released into the air and become shorter from the tip. There was a problem.

  In addition, when the tip portion is shortened, the distance between the gate electrode and the emitter tip is increased, so that the electric field at the emitter tip is weakened, and in order to extract electrons, it is necessary to apply a larger voltage. When the applied voltage is increased, when the electron is emitted, the emitter tip is again affected by oxygen as described above, and the carbon of the emitter material is released into the air, the emitter length is further shortened, and the emitter is applied again. The voltage must be increased. When the above operation is repeated, the tip of the emitter becomes shorter and eventually becomes unusable as a field electron emission device, resulting in a very short lifetime.

  The present invention was devised to solve the above-described problems, and is a field electron emission device capable of preventing deterioration of the tip of a carbon fiber emitter without being affected by oxygen during electron emission, and its The object is to provide a manufacturing method.

  In order to achieve the above object, the invention according to claim 1 is a field electron emission device comprising a carbon fiber type emitter, wherein a carbonized film for preventing deterioration of the emitter is formed on the surface of the emitter. This is a field electron emission device.

  The invention according to claim 2 is the field electron emission device according to claim 1, wherein the carbonized film has a work function lower than that of carbon.

  The invention according to claim 3 is the field electron emission device according to claim 2, wherein the carbonized film is any one of TiC, ZrC, TaC, and NbC.

  According to a fourth aspect of the present invention, there is provided a method for manufacturing a field electron emission device including a carbon fiber type emitter, the first step of depositing a material for forming a carbide film on the surface of the emitter, and annealing. And a second step of forming a carbonized film on the surface of the emitter from the reaction between the material and carbon constituting the emitter.

  According to a fifth aspect of the present invention, an insulating film is formed between a cathode electrode provided with the emitter and a gate electrode, and before the first step, an insulating film between adjacent gate electrodes is formed. 5. The method for manufacturing a field electron emission device according to claim 4, wherein the field electron emission device is removed to a predetermined depth.

  According to the present invention, a carbonized film that prevents deterioration of the carbon fiber type emitter is formed on the emitter surface, and this carbonized film is a protective film that is resistant to heating and oxidation of the tip due to electric field concentration. Deterioration of the tip can be prevented. Further, by making the work function of the carbonized film smaller than that of carbon, the electric field strength at the tip of the emitter can be increased and the driving voltage can be reduced.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1A shows a basic cross-sectional structure of one element of the field electron emission device of the present invention. Moreover, FIG.1 (b) shows what expanded and displayed one carbon fiber 5 of Fig.1 (a).

  As shown in FIG. 1A, a cathode electrode (cathode) 2 is formed on a glass substrate 1, and an insulating film 3 having an opening is formed on the cathode electrode 2. On the insulating film 3, a gate electrode 4 having an opening is provided. A carbon fiber (carbon fiber) 5 is formed on the exposed cathode electrode 2 in the opening.

  The carbon fiber 5 is composed of carbon nanostructures such as carbon nanotubes (CNT), carbon nanofibers (CNF), and graphite nanofibers (GNF). The carbon fiber 5 corresponds to an emitter in the field electron emission device, and when a voltage is applied between the cathode electrode 2 and the gate electrode 4, electrons are emitted from the emitter tip (tip of the carbon fiber 5). Is.

Characteristically, as shown in FIG. 1B, the surface of the carbon fiber 5 including the tip is covered with a carbonized film 5a. The carbide film 5a is so resistant to heat and oxidation due to electric field concentration of the emitter tip, the time of electron emission tip is oxidized, that the carbon constituting the carbon fiber 5 is liberated become CO and CO ₂ It can prevent, and it can prevent that the length of the carbon fiber 5 becomes short.

  TiC (titanium carbide), ZrC (zirconia carbide), TaC (tantalum carbide), NbC (niobium carbide), or the like is used for the carbonized film 5a. For example, in the case of TiC (titanium carbide), the melting point is as high as 3000 ° C. or more, it is chemically stable, and the work function is 3.7 to 3.8 eV, which is lower than the work function of carbon 4 to 5 eV. Low voltage driving can be performed.

  The work function of the carbonized film other than TiC is 3.5 eV for ZrC, 3.05 to 3.98 eV for TaC, and 2.24 to 4.1 eV for NbC, both of which are higher than the work function of carbon. The melting point is as low as 3000 ° C. or higher.

  Next, a method for manufacturing the field electron emission device of FIG. 1 will be described. First, as shown in FIG. 3, the cathode electrode layer 21 is laminated on the glass substrate 1 by sputtering or the like. For the cathode electrode layer 21, Cr, Mo, or the like is used. In this embodiment, description will be made using Cr.

  Next, a resist 6 is applied, exposed to pattern the resist 6 in a stripe shape, and a plurality of stripe-shaped cathode electrodes 2 are formed by wet etching using an acid etchant. As shown in FIG. 6 is removed by ultrasonic cleaning with an organic solvent. At this time, the striped cathode electrode 2 is produced, for example, as shown in FIG.

Thereafter, for example, an insulating film 3 of SiO ₂ is formed, and a gate electrode layer 41 is deposited on the insulating film 3 as shown in FIG. Cr, Mo, or the like can be used for the gate electrode layer 41. In this embodiment, Cr is used as in the cathode electrode 2, and the gate electrode layer 41 is laminated by sputtering.

  As shown in FIG. 6, a resist 7 is applied and exposed to pattern the resist 7 in a stripe shape as shown in FIG. 7, and by wet etching using an acid etchant, a stripe-shaped gate electrode as shown in FIG. A plurality of lines 4 are formed. At this time, not only the gate electrode 4 but also the insulating film 3 is wet-etched using a buffered hydrofluoric acid solution, and the insulating film 3 is dug slightly as shown in the figure. Both the cathode electrode 2 and the gate electrode 4 are formed in a stripe shape, and are formed so as to cross vertically and horizontally.

  Next, after removing the resist 7 by ultrasonic cleaning or the like with an organic solvent, a resist 8 is applied as shown in FIG. In order to form the emitter hole, patterning is performed so as to form an opening in part of the resist 8 by performing exposure as shown in FIG. The opening is formed in an annular shape such as a circular shape or a polygonal shape. As shown in FIG. 11, wet etching is performed to remove a part of the gate electrode 4, and further, the insulating layer 3 is wet etched to expose the cathode electrode 2 to form a recess serving as an emitter hole. .

  The gate electrode 4 is wet etched with an acid-based solution, and a buffered hydrofluoric acid solution is used for wet etching of the insulating film 3.

Next, as shown in FIG. 12, a carbon catalyst 9 is deposited on the resist 8 by sputtering. Then, after the resist 8 is lifted off to leave only the catalyst 9 deposited on the cathode electrode 2 in the emitter hole, as shown in FIG. 13, carbon monoxide (CO) and hydrogen (H ₂ ) is supplied, and the carbon fiber (emitter) 5 is grown on the basis of the catalyst 9.

  Then, as shown in FIG. 14, a carbonized material 10 such as Ti, Zr, Ta, Nb, or the like, which is a raw material for the carbonized film, is deposited by sputtering to about several nm. At this time, the carbonized material 10 is also deposited between the adjacent gate electrodes 4 across the region indicated by A in FIG.

  Two gate electrodes 4 adjacent to each other across the region indicated by A in the figure are for applying an electric field to the emitters of different elements, and operate separately. However, since the carbonized material 10 is a metal and has conductivity, if the carbonized material 10 is deposited in the region A so as to connect the adjacent gate electrodes 4, a short circuit occurs between the adjacent gate electrodes 4. End up.

  However, since wet etching is performed in the manufacturing process of FIG. 8 so that the depth of digging of the insulating film 3 is larger than the deposition height of the carbonized material 10, the deposited carbonized material 10 causes a gap between adjacent gate electrodes 4. Can be prevented from being connected, and a short circuit can be prevented.

Next, rapid heating is performed from room temperature to 550 ° C. to 600 ° C. by rapid annealing (RTA: Rapid Thermal Anneal) in a reducing atmosphere supplied with hydrogen (H ₂ ), and as shown in FIG. A film 5a is formed. If the carbonized material 10 is any one of Ti, Zr, Ta, and Nb as described above, the carbonized film 5a becomes TiC, ZrC, TaC, and NbC, respectively. As described above, the field electron emission device is completed.

It is a figure which shows the cross-section for one element of the field electron emission apparatus in this invention. It is a figure which shows the arrangement | positioning state of the cathode electrode of a field electron emission apparatus. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention. It is a figure which shows one manufacturing process of the field electron emission apparatus in this invention.

Explanation of symbols

1 Glass substrate 2 Cathode electrode 3 Insulating film 4 Gate electrode 5 Carbon fiber (emitter)
5a Carbonized film

Claims (5)

A field electron emission device including a carbon fiber type emitter,
A field electron emission device characterized in that a carbonized film for preventing deterioration of an emitter is formed on a surface of the emitter.   The field electron emission device according to claim 1, wherein the carbonized film has a work function lower than that of carbon.   The field electron emission device according to claim 2, wherein the carbonized film is any one of TiC, ZrC, TaC, and NbC. A method for manufacturing a field electron emission device including a carbon fiber emitter,
A first step of depositing a material for forming a carbide film on the surface of the emitter;
A method of manufacturing a field electron emission device, comprising: a second step of forming a carbide film on the surface of the emitter by a reaction between the material and carbon constituting the emitter by annealing.   An insulating film is formed between the cathode electrode and the gate electrode provided with the emitter, and the insulating film between adjacent gate electrodes is removed to a predetermined depth before the first step. A method for manufacturing a field electron emission device according to claim 4.

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