WO2009151170A1

WO2009151170A1 - Vacuum channel transistor

Info

Publication number: WO2009151170A1
Application number: PCT/KR2008/003362
Authority: WO
Inventors: Youngjin Woo; Gyuha Cho
Original assignee: Jda Technology Co., Ltd.
Priority date: 2008-06-13
Filing date: 2008-06-13
Publication date: 2009-12-17

Abstract

The present invention relates to a transistor, and more particularly, to a vacuum channel transistor. The vacuum channel transistor according to the present invention comprises a semiconductor substrate; a cathode layer disposed on the semiconductor substrate; an anode layer disposed above the cathode layer to be spaced apart from the cathode layer; and a gate layer disposed between the cathode layer and the anode layer to be spaced apart from the cathode layer and the anode layer. In the vacuum channel transistor, the cathode layer comprises a heating resistor, and the gate layer comprises an electron passing region so that electrons emitted from the cathode layer are transferred to the anode layer.

Description

[DESCRIPTION] [invention Title] VACUUM CHANNEL TRANSISTOR

[Technical Field]

The present invention relates to a transistor, and more particularly, to a vacuum channel transistor.

[Background Art] A conventional microtip-type vacuum transistor has a sharp cathode tip and uses the principle that a strong voltage is applied between a cathode electrode and a gate electrode, and electrons quantum-mechanically coming out from the metal surface of the cathode tip are accelerated by applying a high voltage to an anode electrode and then provided to the anode electrode, so that current flows. A voltage of 0.5 V/ A or more should be applied so that free electrons are appropriately emitted from the metal surface in a vacuum. To this end, the radius of the gate electrode at an electron emission portion around the metal cathode tip should be much smaller than lμm. In order to fabricate a microtip of a vacuum transistor that satisfies such a condition, a lμm-or-less semiconductor photolithography process should be supported at a very large area, and a high resolution of lμm or less should be maintained. With the considerable development of current semiconductor processing techniques, such vacuum transistors can be fabricated on a small scale using the semiconductor processing techniques. However, it still takes much time to substantially provide a completed process on a large scale. A stable electron emission material having a low work function is required for the purpose of successful configuration of a vacuum transistor in addition to formation of a gap between electrons and an electron emission portion. The electron emission material is used for driving at a low voltage.

Currently, studies on microtips using a metal such as molybdenum (Mo) or tungsten (W) as such an electron emission material are conducted. A molybdenum or tungsten microtip is mechanically very strong. However, the microtip has a high work function, and there is a limit to allow the curvature radius of the end of the microtip to be small. Therefore, a driving voltage necessary for sufficient electron emission is high.

Recently, studies have been conducted to develop a method of lowering a work function by surface treating a microtip and a material having a low work function such as a diamond-based thin film. Microtip cathodes are being developed in various aspects.

However, the conventional vacuum transistor using a microtip has several problems. Firstly, the microtip may be damaged by ion sputtering or the like during an operation of the vacuum transistor. Secondly, a process for forming the microtip is difficult. Thirdly, the implementation of spatial uniformity is difficult, which has influence on uniformity of an image in an image display device using a vacuum transistor as a pixel. Fourthly, flickers are generated. Fifthly, the gate or cathode tip may be broken down due to arc discharge caused by a high electric field between the gate electrode and the cathode tip. Practically, the degree of a vacuum may be lowered during a process or operation. Since the gap between electrons is very narrow, arc discharge may be easily generated when an impurity such as a small amount of a metal atom is deposited between the electrodes. Sixthly, arc discharge may be generated between the gate and anode. When a high voltage is applied to the anode so as to accelerate electrons, discharge may be generated between broad gate and anode electrodes. Currently, the aforementioned problems are improved, but a fundamental problem is provided from formation of the microtip from which electrons are emitted. For this reason, the present invention provides a novel vacuum transistor of a planar structure so as to solve these problems. [Disclosure] [Technical Problem]

The present invention is conceived to solve the aforementioned problems. Accordingly, an object of the present invention is to provide a vacuum transistor fabricated to be microminiature using a micro-machine and a semiconductor processing technique, thereby operating at a low voltage and making mass production. [Technical Solution]

According to an aspect of the present invention, there is provided a vacuum channel transistor, which comprises: a semiconductor substrate; a cathode layer disposed on the semiconductor substrate; an anode layer disposed above the cathode layer to be spaced apart from the cathode layer; and a gate layer disposed between the cathode layer and the anode layer to be spaced apart from the cathode layer and the anode layer, wherein: the cathode layer comprises a heating resistor; and the gate layer comprises an electron passing region so that electrons emitted from the cathode layer are transferred to the anode layer. Preferably, the cathode layer and the semiconductor substrate are spaced apart from each other.

Preferably, a low work function material is coated on the cathode layer. Preferably, the vacuum channel transistor further comprises one or more control gate layers disposed between the anode layer and the gate layer to be spaced apart from the anode layer and the gate layer, and the control gate layer comprises the same electron passing region as that of the gate layer.

Preferably, the electron passing region comprises a plurality of holes made in a grid shape.

According to another aspect of the present invention, there is provided a vacuum channel transistor, which comprises: a semiconductor substrate; a heating electrode having a heating resistor, and disposed above the semiconductor substrate to be spaced apart from the semiconductor substrate; a cathode layer disposed above the heating electrode to be spaced apart from the heating electrode; an anode layer disposed above the cathode layer to be spaced apart from the cathode layer; and a gate layer disposed between the cathode layer and the anode layer to be spaced apart from the cathode layer and the anode layer, wherein the gate layer comprises an electron passing region so that electrons emitted from the cathode layer are transferred to the anode layer.

Preferably, a low work function material is coated on the cathode layer.

According to still another aspect of the present invention, there is provided a vacuum channel transistor, which comprises: a semiconductor substrate; a channel insulating layer disposed on the semiconductor substrate; a source and a drain disposed on the channel insulating layer to be spaced apart from each other; a gate disposed beneath the channel insulating layer; and a heating resistor layer disposed beneath the semiconductor substrate, wherein: a low work function material is coated on an electron emission portion of the source; the gate is disposed close to the source below a region between the source and the drain; and the semiconductor substrate and the heating resistor layer are electrically isolated from each other.

According to still another aspect of the present invention, there is provided a vacuum channel transistor, which comprises: a semiconductor substrate; a heating resistor layer disposed on the semiconductor substrate; an insulating layer disposed on the heating resistor layer; a channel insulating layer disposed on the insulating layer; a source and a drain disposed on the channel insulating layer to be spaced apart from each other; and a gate disposed beneath the channel insulating layer, wherein: a low work function material is coated on an electron emission portion of the source; and the gate is disposed close to the source below a region between the source and the drain.

Preferably, the vacuum channel transistor further comprises a control gate disposed beneath the channel insulating layer, and the control gate is disposed below a region between the source and the drain to be spaced apart from the gate. According to still another aspect of the present invention, there is provided a vacuum channel transistor, which comprises: a semiconductor substrate; a channel insulating layer disposed on the semiconductor substrate; a source disposed on the channel insulating layer; a drain layer disposed above the source to be spaced apart from the source; a gate disposed beneath the channel insulating layer; and a heating resistor layer disposed beneath the semiconductor substrate, wherein: a low work function material is coated on an electron emission portion of the source; the gate is disposed close to the source below an outer region of the source; and the semiconductor substrate and the heating resistor layer are electrically isolated from each other.

Preferably, the vacuum channel transistor further comprises one or more control gates disposed between the source and the drain layer to be spaced apart from the source and the drain layer.

According to still another aspect of the present invention, there is provided a vacuum channel transistor, which comprises: a semiconductor substrate; a heating resistor layer disposed on the semiconductor substrate; an insulating layer disposed on the heating resistor layer; a channel insulating layer disposed on the insulating layer; a source disposed on the channel insulating layer; a drain layer disposed above the source to be spaced apart from the source; and a gate disposed beneath the channel insulating layer, wherein: a low work function material is coated on an electron emission portion of the source; and the gate is disposed close to the source below an outer region of the source.

Preferably, the vacuum channel transistor further comprises one or more control gates disposed between the source and the drain layer to be spaced apart from the source and the drain layer. [Advantageous Effects] In a vacuum channel transistor according to the present invention, the voltage of a drain can reduce influence on electron emission of a source.

Further, electrons can be emitted from the source at a gate voltage much lower than that in a conventional vacuum channel transistor. [ Description of Drawings ]

FIG. 1 is a cross-sectional view of a vacuum channel transistor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a vacuum channel transistor in which a low work function material is coated according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view of a vacuum channel transistor further including a control gate according to still another embodiment of the present invention.

FIG. 4 is a cross-sectional view of a vacuum channel transistor including a grid-shaped gate according to still another embodiment of the present invention. FIG. 5 is a cross-sectional view of a vacuum channel transistor including a grid-shaped gate electrode and a control gate according to still another embodiment of the present invention.

FIG. 6 is a cross-sectional view of an indirectly heated vacuum channel transistor according to still another embodiment of the present invention. FIG. 7 is a cross-sectional view of a vacuum channel transistor in which a low work function material is coated according to still another embodiment of the present invention.

FIGS. 8 and 9 are cross-sectional views of planar vacuum channel transistors according to still another embodiment of the present invention. FIG. 10 is a cross-sectional view of a planar vacuum channel transistor further including a control gate according to still another embodiment of the present invention.

FIGS. 11 and 12 are cross-sectional views of vertical vacuum channel transistors according to still another embodiment of the present invention.

FIG. 13 is a cross-sectional view of a vertical vacuum channel transistor further including a control gate according to still another embodiment of the present invention.

***** Description of the symbols of the important part of the drawings *****

100: Semiconductor substrate

110: Insulating layer

120: Channel insulating layer 220: Heating electrode 230, 320: Cathode layer (source) 223, 233, 253, 263: Heating resistor 324, 234, 354, 364: Low work function material 350, 360: Source

520, 530, 550, 560: Gate 630, 640, 650, 660, 740, 760: Control gate 900, 920, 930: Anode 950: Drain 960: Drain layer

[Mode for Invention]

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

First of all, electron emission from a cathode electrode in a vacuum will be theoretically described.

Electron emission from a metal in a vacuum is caused by movement of electrons due to the tunneling effect that the height and width of a potential barrier at a metal surface is reduced by a very large electric field. The intensity of an electric field necessary for allowing electrons in a general metal to be emitted into a vacuum is 10⁹[V/m] or more. Such metals are generally pure metals and have a work function of about 3 to 5eV. However, diamond or diamond like carbon (DLC), used as a specific metal compound or nonmetal, has a low work function and obtains emission current having a size similar to that of a general metal even in an electric field of about 10⁷ to

10 [Wm]. If such a metal having a low work function is used as a cathode material, an electron emission transistor capable of being driven at a low voltage can be fabricated.

The current density of electrons emitted from a metal into a vacuum may be obtained by the Fowler-Nordheim equation shown in Equation 1.

Here, Φ denotes a potential difference corresponding to the work function of a metal, t(y) denotes an elliptic function considering an image force of emitted electrons, v(y) denotes an elliptic function, which is almost 1, and E denotes an intensity of an electric field applied to a surface of the metal. Microscopic protrusions may be formed on the surface of the metal. It is generally known that the increment of current due to such protrusions reaches a few hundreds or a few thousands of times.

The amplitude of current is determined by electrons emitted from a cathode, and the amount of the emitted electrons is changed depending on the intensity of an electric field at an edge of a cathode electrode adjacent to a gate electrode and the size of the work function of a metal constituting the cathode electrode. The electric field strength at the edge of the cathode electrode becomes a function of the amplitude of a voltage (gate voltage) applied between the cathode and gate electrodes, the thickness of a channel insulating layer interposed between the cathode and gate electrodes, and the dielectric constant of the channel insulating layer.

Therefore, if the work function (qΦ) of a cathode metal and the intensity of an electric field are given from Equation 1, the current density (J) can be obtained. In order to increase the current density, a material having a low work function is used, the curvature radius at the edge of the cathode electrode is decreased, and the intensity of an electric field is increased by increasing a voltage between the cathode and gate electrodes.

In the conventional vacuum transistor, when the gap between the cathode tip and the gate electrode is formed to be 1 or less, the gate electrode may be broken down due to arc discharge between the cathode tip and the gate electrode. For this reason, there is a limit to decrease the gap between the two electrodes. In order to increase emission current, the electric field strength may be increased by decreasing the curvature radius of the cathode tip. However, there is a structural disadvantage in that the gate voltage should be increased to obtain sufficient emission current. If a gate driving voltage is large, a high-voltage driving IC should be used. Therefore, price is heightened, and power consumption is also increased.

However, in the structure of the present invention, a channel insulating layer is interposed between a gate and a cathode to prevent arc discharge, so that it is possible to prevent a gate from being broken down due to arc discharge in the conventional structure. The thickness of the cannel insulating layer is decreased, so that electrons can be emitted at a gate voltage sufficiently lower than that in the conventional structure.

Therefore, the vacuum transistor can be driven using a low-power and low-voltage driving IC fabricated through a MOS process, and thus, vacuum transistors having price competitiveness can be produced. When assuming that the non-dielectric constant of the channel insulating layer is ε X, the intensity E of an electric field within a vacuum channel in which the cannel insulating layer is adjacent to the cathode electrode is increased by ε X times, and the intensity of the electric field is more increased by a small curvature radius at an edge of the cathode. Accordingly, the current density (J) can be considerably increased. When the cathode is formed of molybdenum (Mo) or tungsten (W), the work function is about 4.5eV, which is excessively large. On the other hand, when the cathode is formed of diamond or DLC having a very low work function, a desired current density can be obtained at a low electric field strength. A possible method is to form a cathode with a conductor having a good conductivity and then coat a low work function material on the cathode. There has been reported an example in which a material, such as diamond or DLC, having a low work function, chemical stability, excellent thermal and electrical conductivity and thermal stability is coated on a surface, thereby improving stability of electron emission and emission characteristics. The low work function material available in the present invention includes all materials having the aforementioned characteristics, for example, including DLC and barium oxide.

The current density of electrons emitted from the cathode can be increased by directly or indirectly heating the cathode. As the temperature of the cathode increases, electrons in a covalent bond strongly tend to become free electrons by obtaining energy. Therefore, a large number of electrons can be emitted even at a low gate voltage. If anode current starts to flow while electrons emitted from the surface of the cathode move along an electric field due to the anode voltage, the amplitude of the current may be easily controlled by the gate. When the vacuum transistor is used for an image display device, energy of accelerated electrons increases as a voltage applied to the anode increases. Preferably, light emitting efficiency is increased using a high- voltage phosphor. However, a flashover phenomenon may occur in a conventional microtip field effect display device. The flashover phenomenon is a phenomenon that occurs when cathode current in a conduction state cannot be controlled by a gate voltage.

In the present invention, a control gate is formed to prevent the flashover phenomenon. A metal having a high work function is selected as a conductor constituting the control gate, so that it is possible to prevent electrons from being directly emitted from a protection gate metal due to the high voltage. The detailed configuration of a control gate according to various embodiments of the present invention will be described later.

Throughout the present specification, the terms "gate, anode, cathode, source, drain and the like" are used as the same meanings as those used in a general transistor. Therefore, detailed functions will be omitted.

Hereinafter, vacuum channel transistors according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a vacuum channel transistor according to an embodiment of the present invention. Referring to FIG. 1, the vacuum channel transistor according to the embodiment of the present invention comprises a semiconductor substrate 100; a cathode layer disposed on the semiconductor substrate 100; an anode layer 930 disposed above the cathode layer 230 to be spaced apart from the cathode layer 230; and a gate layer 530 disposed between the cathode and anode layers 230 and 930 to be spaced apart from the cathode and anode layers 230 and 930.

The cathode layer 230 comprises a heating resistor 233. When current flows in the heating resistor 233, the temperature of the heating resistor increases. Therefore, the entire temperature of the cathode layer 230 is increased, so that electrons can be easily emitted from the cathode layer 230. In order to allow current to flow through the heating resistor 233, it can be readily understood by those skilled in the art that voltage is applied to the heating resistor 233, separately from voltage applied to the gate, anode and cathode of the vacuum channel transistor. The application of voltage to the heating resistor 233 means that a voltage having different potentials is applied to two different points of the heating resistor. The heating resistor 233 may be electrically isolated from the cathode layer 230 so that the current that flows through the heating resistor 233 does not have influence on the cathode layer 230. Preferably, the cathode layer 230 and the semiconductor substrate 100 are spaced apart from each other. By doing so, the heating resistor 233 does not directly conduct heat to a portion except the cathode layer 230. Therefore, the heat has little influence on the temperature of other portions of the device.

If voltage is applied between the gate layer 530 and the cathode layer 230, electrons are emitted from the cathode layer 230, and the emitted electrons are transferred to the anode layer 930 by an electric field formed between the anode layer

930 and the cathode layer 230. At this time, the gate layer 530 comprises an electron passing region so that the electrons emitted from the cathode layer 230 can be transferred to the anode layer 930. The electron passage region has a shape of the gate layer 530 that does not interrupt electrons from being transferred between the cathode layer 230 and the anode layer 930. In order not to interrupt transfer of electrons, the gate layer 530 may have, for example, a shape containing holes in a portion thereof. At this time, electrons may be transferred from the cathode layer 230 to the anode layer 930 through the holes. Alternatively, the gate layer 530 may comprise one or more separate gates disposed therein. At this time, electrons can be transferred from the cathode layer 230 to the anode layer 930 without interruption of the gate layer 530. In this case, the electron passing region refers to a region in which electrons can pass through a section on which the gate layer 530 exists.

The aforementioned vacuum channel transistor shown in FIG. 1 is a vacuum transistor in which a serial triode is implemented on a semiconductor substrate.

FIG. 2 is a cross-sectional view of a vacuum channel transistor according to another embodiment of the present invention. The vacuum channel transistor according to the embodiment of the present invention a low work function material is coated on the cathode layer 230 of the vacuum channel transistor shown in FIG. 1. The low work function material is used so that electrons are emitted from the cathode layer

230 at a lower gate voltage.

Preferably, the low work function material 234 includes a material having a low work function, such as DLC or barium oxide.

FIG. 3 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. The vacuum channel transistor according to the present invention further comprises a control gate layer 630 spaced apart from the anode layer 930 and the gate layer 530 between the anode layer 930 and the gate layer 530 in the vacuum channel transistor according to the aforementioned embodiments. Like the gate layer 530, the control gate layer 630 comprises an electron passing region so that electrons emitted from the cathode layer 230 can be transferred to the anode layer 930.

Hereinafter, the function of the control gate layer 630 will be briefly described. While electrons emitted from a surface of the cathode layer 230 due to the potential difference between the gate layer 530 and the cathode layer 230 move along an electric field due to the voltage of the anode layer 930, anode current starts to flow. At this time, as the voltage applied to the anode layer 930, energy of accelerated electrons increases, and therefore, the speed and efficiency of the device can be improved. However, there is a high possibility of occurrence of the flashover phenomenon that occurs when cathode current in a conduction state cannot be controlled by the voltage of the gate layer 530. Since an increase in amount of electrons emitted from the cathode layer 230 by the voltage of the anode layer 930 is equivalently to decrease the output resistance of the transistor, it is not preferable as a characteristic of the transistor. Therefore, the control gate layer 630 is additionally disposed so that it is possible to prevent the flashover phenomenon and the low output resistance when the voltage of the anode layer 930 is very high. A metal having a high work function is selected as a conductor constituting the control gate layer 630 so that it is possible to prevent electrons from being directly emitted from the control gate layer 630 by a high voltage of the anode layer 930. The low work function material 234 of the cathode layer 230 is partially shielded from the high voltage of the anode layer 930 by applying a negative voltage lower than that of the cathode layer 230 to the control gate layer 630. Therefore, the intensity of a surface electric field can be lowered, or a negative electric field can be maintained. Accordingly, current can be controlled by the control gate layer 630, and the flashover phenomenon can be prevented. The functions of control gates used in the following embodiments are equal to that of the aforementioned control gate.

FIG. 4 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. The vacuum channel transistor according to the embodiment, shown in FIG. 4, comprises an electron passing region of the gate layer 540 having a plurality of holes made in a grid shape in the aforementioned embodiments. That is, a portion of the gate layer 540 is formed in a grid shape. Since the gap between the gate layer 540 and the cathode layer 230 is decreased by such a gate shape, a stronger electric field can be formed at the same gate voltage. Therefore, when the same gate voltage is applied, more electrons are emitted from the cathode layer 230. The emitted electrons are transferred to the anode layer 930 through the grid-shaped gate layer 230.

FIG. 5 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. Referring to FIG. 5, the vacuum channel transistor according to the embodiment of the present invention comprises a semiconductor substrate 100; a cathode layer 230 disposed on the semiconductor substrate 100; an anode layer 930 disposed above the cathode layer 230 to be spaced apart from the cathode layer 230; a gate layer 540 disposed between the cathode and anode layers 230 and 930 to be spaced apart from the cathode and anode layers 230 and 930; and two control gate layers 640 and 740 disposed between the gate layer 540 and the anode layer 930 to be spaced apart from the gate layer 540 and the anode layer 930.

Here, the cathode layer 230 comprises a heating resistor 233, and a low work function material 234 is coated on the cathode layer 230. Each of the gate layer 540 and control gate layers 640 and 740 has an electron passing region so that electrons emitted from the cathode layer 230 can be transferred to the anode layer 930. Here, the electron passing region has the same grid shape as described with reference to FIG. 4.

The vacuum channel transistor comprises two control gate layers 540 and 640, so that the voltage of the anode layer 930 can have less influence on electron emission of the cathode layer 230 as compared with the vacuum channel transistor including one control gate layer. The aforementioned vacuum channel transistor is a vacuum transistor in which a conventional pentode is implemented on a semiconductor substrate.

FIG. 6 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. Referring to FIG. 6, the vacuum channel transistor according to the embodiment of the present invention comprises a semiconductor substrate 100; a heating electrode 220 having a heating resistor 223 and disposed above the semiconductor substrate 100 to be spaced apart from the semiconductor substrate; a cathode layer 320 disposed above the heating electrode 220 to be spaced apart from the heating electrode 220; an anode layer 920 disposed above the cathode layer 320 to be spaced apart from the cathode layer 320; and a gate layer

520 disposed between the cathode layer 320 and the anode layer 920 to be spaced apart from the cathode layer 320 and the anode layer 920. The gate layer 520 comprises an electron passing region so that electrons emitted from the cathode layer 320 can be transferred to the anode layer 920. If voltage or current is applied to the heating resistor 223, its temperature is increased, and therefore, the temperature of the heating electrode 220 is increased. Since the temperature of the heating electrode 220 is increased, the temperature of the cathode layer 320 is increased due to the convection or radiation phenomenon, thereby promoting electron emission. The cathode layer 320 is separated from the heating electrode 220, thereby minimizing a change in electrical characteristic of the entire transistor, caused by electrical characteristics of the heating electrode 220 and the heating resistor 223.

This is a vacuum channel transistor in which an indirectly-heated triode is implemented on a semiconductor substrate. FIG. 7 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. Referring to FIG. 7, a low work function material 324 is coated on the cathode layer 320 of the embodiment shown in

FIG. 6. Electrons can be emitted at a low gate voltage by the low work function material 324.

FIG. 8 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. Referring to FIG. 8, the vacuum channel transistor according to the embodiment of the present invention comprises a semiconductor substrate 100; a channel insulating layer 120 disposed on the semiconductor substrate 100; a source 350 and a drain 950, disposed on the channel insulating layer 120 to be spaced apart from each other; a gate 550 disposed beneath the channel insulating layer 120; and a heating resistor layer 253 disposed beneath the semiconductor substrate 100.

Here, a low work function material 354 is coated on an electron emission portion of the source 350. The gate 550 is disposed close to the source 350 below a region between the source 350 and the drain 950.

If voltage (gate voltage) is applied between the source 350 and the gate 550, electrons are emitted from the source 350 into a vacuum. The emitted electrons are transferred to the drain 950 due to an electric field formed between the drain 950 and the gate 550.

A low work function material is coated on the source 350 so that electrons can be emitted from the source 350 at a lower gate voltage. Preferably, the low work function material 354 is formed of a material having a low work function, such as DLC or barium oxide. The heating resistor layer 253 is disposed so that electrons can be easily emitted from the source. If voltage or current is applied to the heating resistor layer 253, its temperature is increased. Therefore, the temperature of the source 350 is increased, and the low work function material 354 is directly/indirectly increased, thereby promoting electron emission. The semiconductor substrate 100 and the heating resistor 253 may be electrically isolated from each other by an insulating layer

110 so that the voltage or current applied to the heating resistor layer 253 have no influence on other portions of the device.

FIG. 9 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. Referring to FIG. 9, the vacuum channel transistor according to the embodiment of the present invention comprises a semiconductor substrate 100; a heating resistor layer 253 disposed on the semiconductor substrate 100; an insulating layer 110 disposed on the heating resistor layer 253; a channel insulating layer 120 disposed on the insulating layer 110; a source 350 and a drain 950, disposed on the channel insulating layer 120 to be spaced apart from each other; and a gate 550 disposed beneath the channel insulating layer 120.

A low work function material 354 is coated on an electron emission portion of the source 350, and the gate 550 is disposed close to the source 350 below a region between the source 350 and the drain 950. The vacuum channel transistor of this embodiment is a vacuum channel transistor in which the inserting position of the heating resistor layer 253 is changed from that in the vacuum channel transistor shown in FIG. 8.

FIG. 10 is a cross-sectional view of a planar vacuum channel transistor according to still another embodiment of the present invention. Referring to FIG. 10, the vacuum channel transistor according to the embodiment of the present invention further comprises a control gate 650 disposed beneath the channel insulating layer 120 in the vacuum channel transistor according to the embodiment shown in FIG. 9. The control gate 650 is disposed below a region between the source 350 and the drain 950 to be spaced apart from the gate 550. The control gate 650 functions to decrease influence of the voltage of the drain 950 on electron emission of the source 350.

FIG. 11 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. Referring to FIG. 11, the vacuum channel transistor according to the embodiment of the present invention comprises a semiconductor substrate 100; a channel insulating layer 120 disposed on the semiconductor substrate 100; a source 360 disposed on the channel insulating layer 120; a drain layer 960 disposed above the source 360 to be spaced apart from the source; a gate 560 disposed beneath the channel insulating layer 120; and a heating resistor layer 263 disposed beneath the semiconductor substrate 100.

A low work function material 364 is coated on an electron emission portion of the source 360, and the gate 560 is disposed close to the source 360 below an outer region of the source 360. The semiconductor substrate 100 and the heating resistor layer 263 are electrically isolated from each other.

If voltage is applied between the source 360 and the gate 560, electrons are emitted from the source 360 into a vacuum, and the emitted electrons are transferred to the drain layer 960 due to an electric field formed between the drain layer 960 and the gate 560.

Here, the source 360 has a shape through which electrons can be emitted in a horizontal direction. Therefore, the source 360 may be a single layer having a portion of a side surface opened in a vacuum, or comprise two or more separate sources.

The low work function material 364 is coated on the electron emission portion of the source 360 so that electrons can be emitted at a lower gate voltage. Preferably, the low work function material 364 is formed of a material having a low work function, such as DLC or barium oxide. If voltage or current is applied to the heating resistor layer 263, its temperature is increased, and the temperature of the source 360 is directly or indirectly increased due to the increase in temperature of the heating resistor layer 263, thereby promoting electrons emitted from the source 360.

The semiconductor substrate 100 and the heating resistor 263 may be electrically isolated from each other by an insulating layer 110 so that the voltage or current applied to the heating resistor layer 263 have no influence on the transistor.

Although not shown in this figure, the vacuum channel transistor may further comprise a control gate disposed between the source 360 and the drain layer 960 to be spaced apart from the source 360 and the drain layer 960. At this time, the control gate functions to decrease influence of the voltage of the drain layer 960 on electron emission of the source 360.

FIG. 12 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. Referring to FIG. 12, the vacuum channel transistor according to the embodiment of the present invention comprises a semiconductor substrate 100; a heating resistor layer 263 disposed on the semiconductor substrate 100; an insulating layer 110 disposed on the heating resistor layer 263; a channel insulating layer 120 disposed on the insulating layer 110; a source 360 disposed on the channel insulating layer 120; a drain layer 960 disposed above the source 360 to be spaced apart from the source; a gate 560 disposed beneath the channel insulating layer 120; and a control gate 660 disposed between the source 360 and the drain layer

960 to be spaced apart from the source 360 and the drain layer 960.

The control gate 660 functions to decrease influence of the voltage of the drain layer 960 on electron emission of the source 360.

The low work function material 364 is coated on the electron emission portion of the source 360 so that electrons can be emitted at a lower gate voltage. Preferably, the low work function material 364 is formed of a material having a low work function, such as DLC or barium oxide.

If voltage or current is applied to the heating resistor layer 263, its temperature is increased, and the temperature of the source 360 is directly or indirectly increased due to the increase in temperature of the heating resistor layer 263, thereby promoting electrons emitted from the source 360.

FIG. 13 is a cross-sectional view of a vacuum channel transistor according to still another embodiment of the present invention. The vacuum channel transistor shown in FIG. 13 includes two control gates 660 and 760. The vacuum channel transistor comprises the two control gates 660 and 760, so that the voltage of the drain layer 960 can have less influence on electron emission, and the flashover phenomenon can be more easily controlled, as compared with the vacuum channel transistor including only one control gate.

Although the preferred embodiments of the present invention have been described, the present invention may employ various modifications, changes and equivalents. It will be apparent that the present invention may be equally applied by appropriately modifying the embodiments. Accordingly, the descriptions are not intended to limit the scope of the present invention defined by the appended claims.

Claims

[CLAIMS] [Claim 1 ]

A vacuum channel transistor, comprising: a semiconductor substrate; a cathode layer disposed on the semiconductor substrate; an anode layer disposed above the cathode layer to be spaced apart from the cathode layer; and a gate layer disposed between the cathode layer and the anode layer to be spaced apart from the cathode layer and the anode layer, wherein: the cathode layer comprises a heating resistor; and the gate layer comprises an electron passing region so that electrons emitted from the cathode layer are transferred to the anode layer.

[Claim 2]

The vacuum channel transistor as claimed in claim 1, wherein the cathode layer and the semiconductor substrate are spaced apart from each other.

[Claim 3]

The vacuum channel transistor as claimed in claim 1, wherein a low work function material is coated on the cathode layer.

[Claim 4] The vacuum channel transistor as claimed in claim 1, further comprising one or more control gate layers disposed between the anode layer and the gate layer to be spaced apart from the anode layer and the gate layer, wherein the control gate layer comprises the same electron passing region as that of the gate layer.

[Claim 5]

The vacuum channel transistor as claimed in claim 1, wherein the electron passing region comprises a plurality of holes made in a grid shape.

[Claim 6]

A vacuum channel transistor, comprising: a semiconductor substrate; a heating electrode comprising a heating resistor, and disposed above the semiconductor substrate to be spaced apart from the semiconductor substrate; a cathode layer disposed above the heating electrode to be spaced apart from the heating electrode; an anode layer disposed above the cathode layer to be spaced apart from the cathode layer; and a gate layer disposed between the cathode layer and the anode layer to be spaced apart from the cathode layer and the anode layer, wherein the gate layer comprises an electron passing region so that electrons emitted from the cathode layer are transferred to the anode layer.

[Claim 7]

The vacuum channel transistor as claimed in claim 6, wherein a low work function material is coated on the cathode layer.

[Claim 8]

A vacuum channel transistor, comprising: a semiconductor substrate; a channel insulating layer disposed on the semiconductor substrate; a source and a drain disposed on the channel insulating layer to be spaced apart from each other; a gate disposed beneath the channel insulating layer; and a heating resistor layer disposed beneath the semiconductor substrate, wherein: a low work function material is coated on an electron emission portion of the source; the gate is disposed close to the source below a region between the source and the drain; and the semiconductor substrate and the heating resistor layer are electrically isolated from each other.

[Claim 9]

A vacuum channel transistor, comprising: a semiconductor substrate; a heating resistor layer disposed on the semiconductor substrate; an insulating layer disposed on the heating resistor layer; a channel insulating layer disposed on the insulating layer; a source and a drain disposed on the channel insulating layer to be spaced apart from each other; and a gate disposed beneath the channel insulating layer, wherein: a low work function material is coated on an electron emission portion of the source; and the gate is disposed close to the source below a region between the source and the drain.

[Claim 10] The vacuum channel transistor as claimed in claim 9, further comprising a control gate disposed beneath the channel insulating layer, wherein the control gate is disposed below a region between the source and the drain to be spaced apart from the gate.

[Claim 11 ] A vacuum channel transistor, comprising: a semiconductor substrate; a channel insulating layer disposed on the semiconductor substrate; a source disposed on the channel insulating layer; a drain layer disposed above the source to be spaced apart from the source; a gate disposed beneath the channel insulating layer; and a heating resistor layer disposed beneath the semiconductor substrate, wherein: a low work function material is coated on an electron emission portion of the source; the gate is disposed close to the source below an outer region of the source; and the semiconductor substrate and the heating resistor layer are electrically isolated from each other.

[Claim 12]

The vacuum channel transistor as claimed in claim 11, further comprising one or more control gates disposed between the source and the drain layer to be spaced apart from the source and the drain layer.

[Claim 13]

A vacuum channel transistor, comprising: a semiconductor substrate; a heating resistor layer disposed on the semiconductor substrate; an insulating layer disposed on the heating resistor layer; a channel insulating layer disposed on the insulating layer; a source disposed on the channel insulating layer; a drain layer disposed above the source to be spaced apart from the source; and a gate disposed beneath the channel insulating layer, wherein: a low work function material is coated on an electron emission portion of the source; and the gate is disposed close to the source below an outer region of the source. [Claim 14] The vacuum channel transistor as claimed in claim 13, further comprising one or more control gates disposed between the source and the drain layer to be spaced apart from the source and the drain layer.