Field emission device and method of fabricating the same

Information

  • Patent Grant
  • 6729923
  • Patent Number
    6,729,923
  • Date Filed
    Thursday, May 30, 2002
    22 years ago
  • Date Issued
    Tuesday, May 4, 2004
    20 years ago
Abstract
The present invention relates to a field emission device and a method of fabricating the same. The method includes forming a hole having a nanometer size using silicon semiconductor process and then forming an emitter within the hole to form a field emission device. Therefore, the present invention can reduce the driving voltage and thus lower the power consumption.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates generally to a field emission device having an emitter formed in a nano hole, and more particularly to a field emission device and a method of fabricating the same which can lower the operating voltage to reduce the power consumption.




2. Description of the Prior Art




Field emission devices employ a phenomenon that electrons are emitted from a part of the emitter when a voltage is applied between the emitter and a gate electrode. The field emission devices are applied to microwave devices or field emission displays (FED).




Generally, the field emission device is divided into a diode-type having an upper plate and a lower plate used as an emitter and a cathode, and a triode-type having a gate formed around an emitter for supplying a voltage.




As the diode-type has a high operating voltage and is difficult to control the amount of electron emission, the triode-type is usually employed. In particular, a spindle type emitter is widely used.




The spindle type emitter has a fine tip of a cylindrical shape and emits electrons when a high electric field is applied to an end of the fine tip. Thus, as the operating characteristic of the spindle type emitter is stable, it has been most widely used as an emitter of the triode-type field emission device. Further, a lot of researches on the shape and material of the tip have been actively made.




As the field emission device having this spindle type emitter, however, is driven with a high voltage of about 50V˜100V, it has a high consumption voltage. Thus, it is required that the voltage be further lowered in order to commercialize the field emission device using the spindle type emitter.




In order to fabricate a field emission device driven with a low voltage, an aspect ratio of the emitter must be increased. Therefore, a research on manufacturing the emitter using carbon nanotube has recently been made.





FIG. 1

is a cross-sectional view of a conventional field emission device.




Referring now to

FIG. 1

, an emitter electrode


12


made of metal is formed on a silicon substrate


11


. An insulating layer


15


having an aperture


15




a


is formed on the emitter electrode


12


. A catalyst layer


13


made of a transition metal is formed on the emitter electrode


12


exposed through the aperture


15




a


. An emitter


14


is formed on the catalyst layer


13


. A gate electrode


16


having a given pattern is formed on the insulating layer


15


. The transition metal includes carbon nanotube, a nano grain film and a metal tip.




At this time, the emitter


14


composed of a metal tip may be formed right on the emitter electrode


12


exposed through the aperture


15




a


without the catalyst layer


13


.




If an operating voltage is applied to the emitter electrode


12


and the gate electrode


16


, respectively, a high electric field is formed around the emitter


14


. Due to this, electrons are emitted from the emitter


14


.




Meanwhile, in order to fabricate the field emission device driven with a low voltage, it is required that the aspect ratio of the emitter be increased. The aspect ratio of the emitter can be increased by a formation of a hole having a nanometer size. The hole having a nanometer size should be formed in anodized aluminum oxide layer since the hole can not be formed in conventional oxide layer. However, anodized aluminum oxide is not suitable for the semiconductor manufacturing process. Therefore, it is difficult to manufacture the emitter having a large aspect ratio by using the conventional method.




SUMMARY OF THE INVENTION




The present invention is contrived to solve the above problems and an object of the present invention is to provide a field emission device and a method of fabricating the same, capable of reducing the driving voltage and thus lower the power consumption, in such as way that a hole having a nanometer size is formed by processes of manufacturing the semiconductor devices and an emitter is then formed in the hole to increase the aspect ratio of the emitter.




In order to accomplish the above object, a field emission device according to the present invention, is characterized in that it comprises a silicon substrate having an emitter electrode formed in a surface portion thereof; an insulating layer formed on the emitter electrode and having a nano hole to expose the emitter electrode; an emitter formed on the emitter electrode exposed through the nano hole; and a gate electrode formed on the insulating layer.




A method of fabricating a field emission device according to the present invention is characterized in that it comprises the steps of forming silicon rods on a silicon substrate; forming an emitter electrode within the silicon substrate; forming insulating layer between the silicon rods; forming a gate electrode on the insulating layer; forming a nano hole in the insulating layer by removing the silicon rods; and forming an emitter on the emitter electrode exposed through the nano hole.











BRIEF DESCRIPTION OF THE DRAWINGS




The aforementioned aspects and other features of the present invention will be explained in the following description, taken in conjunction with the accompanying drawings, wherein:





FIG. 1

is a cross-sectional view of a conventional field emission device;





FIG. 2

is a cross-sectional view of a field emission device according to the present invention;





FIG. 3



a


˜

FIG. 3



g


are cross-sectional views of field emission devices for describing a method of fabricating the field emission devices according to a preferred embodiment of the present invention; and





FIG. 4



a


and

FIG. 4



b


are cross-sectional views of field emission devices for describing a method of fabricating the field emission devices according to another embodiment of the present invention.











DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS




The present invention will be described in detail by way of a preferred embodiment with reference to accompanying drawings, in which like reference numerals are used to identify the same or similar parts.





FIG. 2

is a cross-sectional view of a field emission device according to the present invention.




Referring now to

FIG. 2

, an emitter electrode


24


is formed on a silicon substrate


21


. An insulating layer


25


is formed on the emitter electrode


24


. A nano hole


27


having a nanometer size is formed in the insulating layer


25


. A catalyst layer


28


is formed on the emitter electrode


24


exposed through the nano hole


27


. An emitter


29


is formed within the nano hole


27


. A gate electrode


26


is formed on the insulating layer


25


around the emitter


29


.




The emitter electrode


24


is composed of an impurity region in which an impurity is implanted into the silicon substrate


21


. The insulating layer


25


is formed of a low-temperature silicon oxide film or a silicon nitride film. Further, the catalyst layer


28


is made of a transition metal and is formed by means of an Electrochemical Deposition Method.




The emitter


29


is selectively formed on the catalyst layer


28


by a Chemical Vapor Deposition Method if the emitter


29


is made of either carbon nanotube or a nano grain film. On the contrary, in case of the emitter


24


is made of a metal tip, the emitter


24


is formed by an Electro-Beam Evaporation Method. The gate electrode


26


is made of a common metal or polysilicon.




A method of fabricating the field emission device formed thus will be below described.





FIG. 3







FIG. 3



g


are cross-sectional views of field emission devices for describing a method of fabricating the field emission devices according to a preferred embodiment of the present invention.




Referring now to

FIG. 3



a


, a given region of a silicon substrate


21


is etched by a given thickness to form a protruded portion


21




a.






By reference to

FIG. 3



b


, an oxide film


22


is grown on a surface of the silicon substrate


21


and the protruded portion


21




a


by an oxidization process. The surface of the silicon substrate


21


is changed to the oxide film


22


as the reaction of silicon with oxygen. At this time, the thickness of the protruded portion


21




a


remained can be thin to be a nanometer size by controlling the oxidation condition.




Referring now to

FIG. 3



c


, the oxide film


22


is removed to form silicon rods


23


made of the protruded portion


21




a


that remains without being oxidized. Next, an n-type impurity is implanted into the silicon substrate


21


, and then annealing process is performed to diffuse the impurity. Thereby, the emitter electrode


24


is formed in a surface portion of the silicon substrate


21


.




By reference to

FIG. 3



d


, an insulating layer


25


is formed between the silicon rods


23


. A gate electrode


26


is then formed on a given region of the insulating layer


25


. The insulating layer


25


is formed to have the same height to the silicon rod


23


, so that an upper surface of the silicon rod


23


is exposed. The gate electrode


26


is formed to have a given pattern so that it does not overlap with the silicon rod


23


.




At this time, a self align etching method can be used to form the gate electrode


26


.




The higher of the insulating layer


25


formed on the silicon rod


23


is higher than that of the insulating layer


25


formed between the silicon rod


23


by the aspect of the silicon rod


23


. In this status, a conductive layer and a photoresist film (not shown) are formed on the insulating layer


25


, sequentially. The photoresist film is removed by an etch back process until the conductive layer formed on the silicon rod


23


is exposed. And then the photoresist film and the conductive layer exposed are removed until the conductive layer formed between the silicon rod


23


is exposed. The gate electrode


26


composed of the conductive layer remained is formed by the above self-aligned patterning method.




The insulating layer


25


is formed of a low-temperature silicon oxide film or a silicon nitride film. The gate electrode


26


is formed of metal or polysilicon.




Referring now to

FIG. 3



e


, the silicon rod


23


is removed by etching process. A nano hole


27


having a nanometer size is formed at a region from which the silicon rod


23


is removed. The emitter electrode


24


is exposed at the bottom of the nano hole


27


.




A dry etch process or a wet etch process is performed to remove the silicon rod


23


. The etching selective ratio of the insulating layer


25


and the silicon rod


23


is controlled to remove only the silicon rod


23


.




Thereafter, an emitter


29


is formed within the nano hole


27


. At this time, a method of forming the emitter


29


may differ depending on what material is the emitter is formed. A method of forming the emitter


29


using carbon nanotube or a nano grain film will be first described below.




Referring now to

FIG. 3



f


, if the carbon nanotube or the nano grain film is used to form the emitter


29


, a catalyst layer is required to grow the carbon nanotube or the nano grain film. A catalyst layer


28


is formed on the emitter electrode


24


exposed through the nano hole


27


. The catalyst layer


28


is formed by means of an Electrochemical Deposition Method, so that the catalyst layer


28


is selectively formed only on the emitter electrode


24


.




Referring now to

FIG. 3



g


, the carbon nanotube or the nano grain film is formed on the catalyst layer


28


to form the emitter


29


. The carbon nanotube or nano grain film is grown by means of a Chemical Vapor Deposition Method. Thereby, the triode-type field emission device can be fabricated.




As shown in

FIG. 3



g


, the aspect ratio of the emitter


29


is increased since the emitter


29


is formed within the nano hole


27


. Therefore, electrons can be efficiently emitted even at a low voltage level.




Meanwhile, a method of forming the emitter


29


using a metal tip will be below described by reference to

FIG. 4



a


and

FIG. 4



b.






Referring now to

FIG. 4



a


, though not shown in the drawings, processes before

FIG. 4



a


are same to those from

FIG. 3



a


˜

FIG. 3



e


. The process before

FIG. 4



a


will not be described. An emitter electrode


24


is grown to form an emitter growth layer


24




a


at the bottom of a nano hole


27


. A sacrifice metal layer


30


is then formed on an insulating layer


25


and a gate electrode


26


. The sacrifice metal layer


30


is made of a material that is usually made of aluminum or materials that can be lift off but do not affect other thin films. The sacrifice metal layer


30


is formed by means of an Electro-Beam Evaporation Method.




Referring now to

FIG. 4



b


, metal is deposited within the nano hole


27


using a deposition apparatus having a good linearity to thus form an emitter


31


. The sacrifice metal layer


30


is then removed. Thus the triode-type field emission device which can smoothly emit electrons even at a low voltage level is fabricated.




As mentioned above, the present invention includes forming a hole having a nanometer size by using common semiconductor manufacturing processes and forming an emitter within the nano hole to increase the aspect ratio of the emitter. Therefore, the present invention has outstanding advantages that it can lower the driving voltage and reduce the power consumption.




The present invention has been described with reference to a particular embodiment in connection with a particular application. Those having ordinary skill in the art and access to the teachings of the present invention will recognize additional modifications and applications within the scope thereof.




It is therefore intended by the appended claims to cover any and all such applications, modifications, and embodiments within the scope of the present invention.



Claims
  • 1. A method of fabricating a field emission device, comprising the steps of:forming silicon rods on a silicon substrate; forming an emitter electrode within said silicon substrate; forming insulating layer between said silicon rods; forming a gate electrode on said insulating layer; forming a nano hole in said insulating layer by removing said silicon rods; and forming an emitter on said emitter electrode exposed through said nano hole.
  • 2. The method as claimed in claim 1, wherein said emitter electrode is formed by the steps of:implanting an impurity into said silicon substrate; and diffusing said impurity.
  • 3. The method as claimed in claim 2, wherein said impurity is an N-type impurity.
  • 4. The method as claimed in claim 1, wherein said emitter is formed by the steps of:forming a catalyst layer on said emitter electrode exposed through said nano hole; growing any one of carbon nanotube and a nano grain film on said catalyst layer to form emitter.
  • 5. The method as claimed in claim 4, wherein said catalyst layer is formed by an Electrochemical Deposition Method.
  • 6. The method as claimed in claim 1, wherein said emitter is formed by the steps of:growing said emitter electrode exposed through said nano hole to form an emitter growth layer; forming a sacrifice metal layer on said insulating layer and said gate electrode; depositing metal on said emitter growth layer to form a metal tip; and removing said sacrifice metal layer.
  • 7. The method as claimed in claim 6, wherein said sacrifice metal layer is made of aluminum or materials that can be lift off, and wherein said sacrifice metal layer is formed by an Electrochemical Deposition Method.
  • 8. A method of fabricating a field emission device, comprising the steps of:forming silicon rods on a silicon substrate, wherein said silicon rods are formed by the steps of etching a given region of said silicon substrate by a target thickness to form a protruded portion, oxidizing the surface of said silicon substrate and said protruded portion to form an oxide film, and removing said oxide film; forming an emitter electrode within said silicon substrate; forming insulating layer between said silicon rods; forming a gate electrode on said insulating layer; forming a nano hole in said insulating layer by removing said silicon rods; and forming an emitter on said emitter electrode exposed through said nano hole.
  • 9. The method as claimed in claim 8, wherein said emitter electrode is formed by the steps of:implanting an impurity into said silicon substrate; and diffusing said impurity.
  • 10. The method as claimed in claim 9, wherein said impurity is an N-type impurity.
  • 11. The method as claimed in claim 8, wherein said emitter is formed by the steps of:forming a catalyst layer on said emitter electrode exposed through said nano hole; growing any one of carbon nanotube and a nano grain film on said catalyst layer to form said emitter.
  • 12. The method as claimed in claim 11, wherein said catalyst layer is formed by an Electrochemical Deposition Method.
  • 13. The method as claimed in claim 8, wherein said emitter is formed by the steps of:growing said emitter electrode exposed through said nano hole to form an emitter growth layer; forming a sacrifice metal layer on said insulating layer and said gate electrode; depositing metal on said emitter growth layer to form a metal tip; and removing said sacrifice metal layer.
  • 14. The method as claimed in claim 13, wherein said sacrifice metal layer is made of aluminum or materials that can be lift off, and wherein said sacrifice metal layer is formed by an Electrochemical Deposition Method.
Priority Claims (1)
Number Date Country Kind
2001-86836 Dec 2001 KR
US Referenced Citations (14)
Number Name Date Kind
3755704 Spindt et al. Aug 1973 A
5583393 Jones Dec 1996 A
5910701 Takemura Jun 1999 A
5965972 Takada et al. Oct 1999 A
5973444 Xu et al. Oct 1999 A
6031322 Takemura et al. Feb 2000 A
6057172 Tomihari May 2000 A
6146227 Mancevski Nov 2000 A
6187603 Haven et al. Feb 2001 B1
6278231 Iwasaki et al. Aug 2001 B1
6369496 Yoshiki Apr 2002 B1
6422906 Hofmann et al. Jul 2002 B1
6482575 Tokai et al. Nov 2002 B2
6574130 Segal et al. Jun 2003 B2
Foreign Referenced Citations (1)
Number Date Country
2001-39123 May 2001 KR