KR100233255B1 - Fed having control transistor and method for manufacturing the same - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

A field emission device having a control transistor and a method of manufacturing the same.

2. Technical problem to be solved by the invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron source device, and provides a silicon field emission device having a control transistor, thereby easily controlling electron emission in the electron source device, stabilizing and improving uniformity of electron emission characteristics, and device breakage. It is for suppressing (failure). In addition, a method for manufacturing the proposed field emission device on a glass substrate by a low temperature process is provided, thereby providing a method for manufacturing a low cost and large area electron source device using a semiconductor process.

3. Summary of the Solution of the Invention

The field emission device of the present invention includes a silicon field emission device and a thin film transistor on an insulating substrate, and the cathode electrode of the silicon field emission device and the source of the thin film transistor are electrically connected to each other, and the gate and the drain of the thin film transistor. The emission characteristics of the field emission device can be easily controlled by adjusting the voltage applied to the field emission device.

4. Important uses of the invention

Microwave devices and field emission devices used as electron sources for sensors and flat panel displays

Description

Field emission device having control transistor and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron source device, and more particularly to a silicon field emission device having a control transistor and a method of manufacturing the same. The field emission device is a device that emits electrons from an electrode (hereinafter referred to as a cathode electrode) by applying an electric field in a vacuum or a specific gas atmosphere. Such a field emission device is used as an electron source such as a microwave device and a sensor, a flat panel display.

In general, the emission of electrons in the field emission device varies greatly depending on the device structure, electrode material, and electrode shape. Currently, the structure of the field emission device can be largely classified into a diode composed of a cathode electrode and an anode, and a triode composed of a cathode electrode, a gate, and an anode. The three-pole structure has been developed because low-voltage driving is possible compared to the two-pole type because the electric field for electron emission is applied to the gate adjacent to the cathode electrode, and the emission current can be easily controlled by the gate as well as the anode. Electrode materials include metals, silicon, diamonds, and diamond like carbon, and if silicon is used as an electrode material, the advantages of using semiconductor process equipment and the field emission device can be made compatible with integrated circuit process. You can take advantage of it.

On the other hand, the field emission device has a disadvantage in that its electrical characteristics are very unstable due to the characteristics of electrons penetrating the cathode electrode surface, the uniformity of electrical characteristics between the cathode electrodes is poor, and device breakage due to overcurrent is easily caused. In order to solve this problem, control transistors have been introduced into field emission devices.

1 shows a cross-sectional view of a silicon field emission device with a conventional control MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor).

As shown in FIG. 1, a conventional silicon field emission device has an n-well 311 on a p-type silicon wafer 30. And a cathode electrode 312, a gate insulating film 313, and a gate electrode 314 of the field emission device on the n-well 311, a drain 323 of the MOSFET for controlling the field emission device, The gate insulating film 324, the gate electrode 325, and the drain electrode 326 are formed. In FIG. 1, the field emission characteristics can be easily controlled by adjusting the voltages applied to the drain 323 and the gate electrode 325 of the MOSFET.

However, since the field emission output is controlled by a MOSFET having good electrical characteristics, the silicon field emission device having the conventional control MOSFET facilitates control of electron emission, stabilization and uniformity of electron emission characteristics, and device breakage. Field emission characteristics such as suppression of failure) can be greatly improved, but since a silicon wafer must be used as the substrate of the field emission device, a large area electron source device can not be manufactured and a manufacturing cost is large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a silicon field emission device having a control transistor capable of easily controlling electron emission, stabilization and uniformity of electron emission characteristics, and suppressing device failure.

In addition, an object of the present invention is to provide a field emission device and a method of manufacturing the same that can be manufactured on a glass substrate in a low temperature process can reduce the cost.

1 is a cross-sectional view of a field emission device having a conventional control transistor.

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

3 (a) to 3 (k) are sectional views of the manufacturing process of the field emission device having the control transistor according to the present invention.

* Explanation of symbols for main parts of the drawings

10: insulating substrate 11: field emission device

12 thin film transistor 20 insulating film

30 p-type silicon wafer 114 gate of field emission device

127: gate electrode of the thin film transistor 210: insulating film

211: doped polycrystalline silicon 213: oxide film

211a, 212a, 212b, 212c: undoped amorphous silicon

220: oxide film or nitride film

222,223,225,226,227: Doped Polycrystalline Silicon

221a, 225a: undoped polycrystalline silicon film

311 n-type well 314 gate of field emission device

A field emission device having a control transistor of the present invention includes an insulating substrate; A first cathode electrode formed horizontally on the insulating substrate; A second cathode electrode formed on a portion of an upper portion of the first cathode electrode and electrically connected to the first cathode electrode; A gate insulating layer formed on the first cathode electrode; A gate electrode formed on the gate insulating layer and extending toward the second cathode without being in electrical contact with the second cathode; And a thin film transistor having a source region formed on an extension line of the first cathode electrode formed horizontally on the insulating substrate and electrically connected to the first cathode electrode.

A method of manufacturing a field emission device with a control transistor of the present invention includes the steps of forming a first amorphous silicon film doped on an insulating substrate; Implanting an impurity into the first amorphous silicon film by forming a first mask layer in a selected region over the undoped first amorphous silicon film; After converting the first amorphous silicon film to a polycrystalline silicon film and activating the implanted impurities, a second amorphous silicon film is formed on the entire surface of the substrate, and then a second mask layer is formed on the selected region above the second amorphous silicon film. Forming a; Etching the second amorphous silicon film using the second mask layer to form a pillar-shaped conical silicon cathode electrode body; After removing the first mask layer, forming a first insulating film over the entire structure, and then forming a gate body of a thin film transistor made of an undoped silicon film of a selected size in a selected region of the first insulating film; ; Implanting impurities into the silicon cathode electrode body, the gate body of the thin film transistor, and selected regions of the polycrystalline silicon film to form channels, sources, and drains of the cathode electrode of the field emission device and the thin film transistor; Forming a second insulating layer over the entire structure and exposing portions of the gate and the source by removing the first and second insulating layers on the drain and the gate of the thin film transistor; Sequentially forming a conductive film and a planarization layer on the entire structure; Performing an etch back process on the conductive film and the planarization layer to remove the conductive film of the cathode electrode portion, and then removing selected regions of the first and second oxide films to expose the conical cathode electrode; And patterning the conductive film to form a gate of the field emission device, a drain electrode of the thin film transistor, and a gate electrode.

In addition, the method of manufacturing a field emission device having a control transistor of the present invention includes the steps of forming an undoped first amorphous silicon film on an insulating substrate; Implanting an impurity into a portion of the first amorphous silicon film and heat treating the first amorphous silicon film to form a first polycrystalline silicon film; Forming a conical silicon cathode electrode body having a column on a portion of the first amorphous silicon film; Forming a first insulating film over the entire structure and forming a gate electrode of a thin film transistor having a predetermined size on the first insulating film; Implanting impurities into the silicon cathode electrode body and a portion of the first polycrystalline silicon film to form a source and a drain of the thin film transistor; Forming a second insulating layer over the entire structure and exposing the gate electrode and the drain of the thin film transistor; Sequentially forming a conductive film and a planarization layer on the entire structure; Performing an etch back process on the conductive film and the planarization layer to remove the conductive film of the cathode electrode portion, and then removing selected regions of the first and second oxide films to expose the cathode electrode; And patterning the conductive film to form a gate of the field emission device, a drain electrode of the thin film transistor, and a gate electrode.

Hereinafter, with reference to the accompanying drawings looks at the field emission device of the present invention and its manufacturing method in detail.

First, a field emission device having a control transistor proposed in the present invention will be described in detail with reference to FIG. 2.

As shown in FIG. 2, a silicon field emission device 11 and a thin film transistor 12 are formed on an insulating substrate 10, and a cathode electrode 111 of the silicon field emission device and a source of the thin film transistor ( 122 is electrically connected to each other, and controls emission characteristics of the field emission device by adjusting voltages applied to the gate 125 and the drain 123 of the thin film transistor.

The insulating substrate 10 is formed of an oxide film, a nitride film, quartz, glass, or the like, and the silicon field emission device 11 is composed of one or a plurality of arrays. Each field emission device has a gate insulating film in a region selected to apply an electric field to the cathode electrode 111 and the conical silicon cathode electrode 112 having a column in the selected region of the cathode electrode 111 and the cathode electrode 112. 113 and the gate 114. Meanwhile, the thin film transistor 12 includes a channel 121 made of undoped polycrystalline silicon and a source 122 / drain 123 made of polycrystalline silicon doped on both sides of the channel 121 and the channel 121. And a gate insulating layer 124 formed on the source 122 and the drain 123, and a drain electrode connected to the gate 125 and the drain 123 and the gate 125 formed in the selected region on the gate insulating layer 124, respectively. 126 and the gate electrode 127. The cathode electrode 111 of the field emission device and the source 122 of the thin film transistor are formed on the same layer and are electrically connected to each other.

The anode of the field emission device is made of metal or ITO (Indium Tin Oxide) on a new insulating substrate different from the substrate of FIG. 3, and the cathode on which the anode is formed and the cathode of the field emission element of FIG. Substrates 111 and 112, the gate 114, and the substrate on which the thin film transistors are formed are vacuum-packed with each other to complete a tripolar field emission device.

The method of manufacturing the field emission device according to the present invention will be described with reference to FIGS. 3 (a) to 3 (k) as follows.

First, as shown in FIG. 3 (a), a low pressure chemical vapor deposition (LPCVD) or plasma enhanced chemical vapor deposition method is carried out on an insulating substrate 20 made of an oxide film, a nitride film, quartz, glass, or the like. (Plasma Enhanced Chemical Vapor Deposition: PECVD) is used to form an undoped amorphous silicon thin film 211A.

As shown in FIG. 3 (b), after an oxide film or a nitride film is deposited on the amorphous silicon 211A, the oxide film or the nitride film is formed on the selected region on the amorphous silicon 211A by using photolithography and etching processes. A first insulating film 220 made of a nitride film is formed to a predetermined size. Thereafter, the amorphous silicon is formed using an n-type or p-type impurity element as the mask layer as a mask layer using an ion implantation or an ion shower process. Inject to (211A). Amorphous silicon 211A below the first insulating layer 220 is a region where a thin film transistor is to be formed later. The impurity element is mainly composed of phosphorus (P) when n-type, and boron when p-type. (B).

For example, as shown in FIG. 3 (c), after the process of FIG. 3 (b), the amorphous silicon 211A is converted into polycrystalline silicon by annealing an electric furnace or laser annealing. After activating the impurity element implanted in the silicon 211A, the cathode electrode 211 made of doped polycrystalline silicon and the undoped polycrystalline silicon 221A are formed, and then the cathode electrode 211 and the LPCVD or PECVD are used. An undoped amorphous silicon 212A is formed on the entire surface of the first insulating layer 220. Thereafter, an oxide film or a nitride film is deposited on the amorphous silicon 212A, and a disk-shaped second insulating film 210 made of an oxide film or a nitride film is formed on a region selected on the amorphous silicon 212A by using photolithography and etching processes. Form. The disc-shaped second insulating film 210 is formed so as not to vertically overlap with the first insulating film 220 of FIG. 3 (b), and is used as a mask layer when partially etching the amorphous silicon 212A. .

In FIG. 3 (d), after the process of FIG. 3 (c), the amorphous silicon 212A is etched in two steps of isotropic etching and anisotropic etching (primary: isotropic, Secondary: anisotropic) to form columnar truncated conical silicon 212B. After the etching process, the second insulating layer 210 used as the mask layer may be maintained as it is.

In FIG. 3 (e), the pillared truncated conical silicon 212B is isotropic wet etched to form a pillared and pointed conical silicon 212C (cathode electrode body). The isotropic wet etching is performed with a solution made by properly mixing hydrofluoric acid (HF), acetic acid (CH ₃ COOH), and nitric acid (HNO ₃ ). An end of the cathode electrode body 212C is formed at the neck of the silicon film 212B, and the mask layer 210 is formed of silicon 212B (or a cathode electrode body) when the cathode electrode body 212C is completed. 212C)).

Subsequently, in FIG. 3 (f), after the process of FIG. 3 (e), the first insulating film 220 is removed by wet etching, and then an oxide film 224 is formed on the entire surface of the substrate by chemical vapor deposition. . The oxide film 224 is used as a gate insulating film of a thin film transistor. Thereafter, an undoped silicon thin film is deposited on the gate oxide layer 224, and then patterned to form the undoped silicon thin film using photolithography and etching to form a layer on the undoped polycrystalline silicon film 221A. The gate body 225A of the thin film transistor of the selected size is formed in the selected region of the.

In FIG. 3 (g), after the process of FIG. 3 (f), an n-type or p-type impurity element is formed into the gate of the cathode electrode body 212C and the thin film transistor using ion implantation or an ion shower. After implanting into the selected region of the body 225A and the undoped polycrystalline silicon film 221A and performing heat treatment to activate the impurity element, the channel 221, the source 222 / drain 223 and the gate of the thin film transistor are activated. In addition to forming 225, a cathode electrode 212 is formed. The impurity element is mainly composed of phosphorus (P) in the case of n-type, boron (B) in the case of p-type, and the doping type is the doping type of the cathode electrode 211 of FIG. Do the same. The region near the surface of the cathode electrode 212 is made of doped polycrystalline silicon and the inside is made of undoped polycrystalline silicon. In the process of FIG. 3 (g), the source 222 of the thin film transistor is formed to be connected to the cathode electrode 211 of the field emission device.

In FIG. 3 (h), the oxide film 213 is deposited on the entire surface of the substrate using the chemical vapor deposition method on the structure of FIG. 3 (g). The oxide film 213 is used as a gate insulating film of the field emission device. Thereafter, contact holes are formed by patterning the oxide layers 213 and 224 on the drain 223 and the gate 225 of the thin film transistor using photolithography and an etching process.

In FIG. 3 (i), a metal film or doped silicon 214A is deposited on the structure of FIG. 3 (h) by chemical vapor deposition or physical vapor deposition. Thereafter, a photoresist or spin-on-glass (SOG) material 230 is deposited on the metal layer or the doped silicon 214A. Here, the metal film or doped silicon 214A is used as the gate electrode material of the field emission device, and the photoresist or SOG material 230 is used as the planarization layer.

In FIG. 3 (j), after the process of FIG. 3 (i), an etch-back process is performed by a plasma etching method, and a photoresist or SOG material 230 and a metal film or doped silicon ( 214A) is simultaneously etched. In this case, the etching rate difference and the etching time of the photoresist or the SOG material 230, the metal film or the doped silicon 214A, and the oxide film 213 are controlled to form an upper portion of the cathode electrode 212. The metal film or the doped silicon 214A may be removed to form a gate hole of the field emission device. The oxide films 213 and 224 around the cathode electrode 212 are then removed by wet or vapor phase etch to expose the cathode electrode 212.

Finally, in FIG. 3 (k), after the process of FIG. 3 (j), the metal or doped silicon 214A is patterned by photolithography and etching to form the gate 214 of the field emission device and the thin film transistor. The drain electrode 226 and the gate electrode 227 are formed.

The manufacturing method according to the present invention as described above all the processes can be carried out at a temperature of 600 ℃ or less, it is also compatible with the semiconductor integrated circuit process.

In the present invention, by introducing a control thin film transistor into the field emission device, not only the emission characteristics of the field emission device can be easily controlled, but also effects such as stabilization and uniformity of electron emission characteristics, suppression of element breakage, and the like can be expected. In addition, since the active material of the field emission device and the control transistor is composed of polycrystalline silicon formed on an insulating substrate and the field emission device can be manufactured by a semiconductor process of 600 ° C. or less, a large area and low cost glass can be used as the substrate of the field emission device. In addition, it can significantly increase the manufacturing productivity. Accordingly, by using the present invention, the characteristics of the field emission device can be easily controlled, and the low cost and large area field emission device can be easily manufactured by the semiconductor process.

Claims (17)

Insulating substrate; A first cathode electrode formed horizontally on the insulating substrate; A second cathode electrode formed on a portion of an upper portion of the first cathode electrode and electrically connected to the first cathode electrode; A gate insulating layer formed on the first cathode electrode; A gate electrode formed on the gate insulating layer and extending toward the second cathode without being in electrical contact with the second cathode; And a thin film transistor having a source region formed on an extension line of the first cathode electrode formed horizontally on the insulating substrate and electrically connected to the first cathode electrode. device. The field emission device as claimed in claim 1, wherein the insulating substrate is made of an oxide film, a nitride film, quartz, or glass. 2. The field emission device as claimed in claim 1, wherein the second cathode electrode is made of a conical polycrystalline silicon film having pillars. The field emission device as claimed in claim 1, wherein the thin film transistor has a source, a channel, and a drain made of a polycrystalline silicon film. Forming a undoped first amorphous silicon film on the insulating substrate; Implanting an impurity into the first amorphous silicon film by forming a first mask layer in a selected region over the undoped first amorphous silicon film; After converting the first amorphous silicon film into a polycrystalline silicon film and activating the implanted impurities, a second amorphous silicon film is formed on the entire surface of the substrate, and then a second mask is formed on the selected region above the second amorphous silicon film. Forming a layer; Etching the second amorphous silicon film using the second mask layer to form a pillar-shaped conical silicon cathode electrode body; After removing the first mask layer, forming a first insulating film over the entire structure, and then forming a gate body of a thin film transistor made of an undoped silicon film of a selected size in a selected region of the first insulating film; ; Implanting impurities into the silicon cathode electrode body, the gate body of the thin film transistor, and selected regions of the polycrystalline silicon film to form channels, sources, and drains of the cathode electrode of the field emission device and the thin film transistor; Forming a second insulating layer over the entire structure and exposing portions of the gate and the drain by removing the drain and the first and second insulating layers on the gate of the thin film transistor; Sequentially forming a conductive film and a planarization layer on the entire structure; Performing an etch back process on the conductive film and the planarization layer to remove the conductive film of the cathode electrode portion, and then removing selected regions of the first and second oxide films to expose the conical cathode electrode; And patterning the conductive film to form a gate of the field emission device, a drain electrode of the thin film transistor, and a gate electrode. 6. The method of manufacturing a field emission device having a control transistor according to claim 5, wherein said insulating substrate is made of an oxide film, a nitride film, quartz, or glass. The method of manufacturing a field emission device having a control transistor according to claim 5, wherein the conversion of the amorphous silicon film into a polycrystalline silicon film and activation of impurities are performed by an electric furnace heat treatment or laser annealing. 6. The field emission device as claimed in claim 5, wherein the pillar-shaped cathode electrode body is formed by sequentially performing isotropic dry etching, anisotropic dry etching, and isotropic wet etching. Manufacturing method. 6. The method of claim 5, wherein impurities in the silicon cathode electrode body and the gate body, the source and the drain of the thin film transistor are formed by ion implantation or ion shower. 6. The method of manufacturing a field emission device having a control transistor according to claim 5, wherein the removal of the conductive film of the cathode electrode portion is performed by an etch back process. The method of claim 8, wherein the isotropic wet etching is performed with a mixed solution of hydrofluoric acid (HF), acetic acid (CH ₃ COOH), and nitric acid (HNO ₃ ). Forming a undoped first amorphous silicon film on the insulating substrate; Implanting an impurity into a portion of the first amorphous silicon film and heat treating the first amorphous silicon film to form a first polycrystalline silicon film; Forming a conical silicon cathode electrode body having a column on a portion of the first amorphous silicon film; Forming a first insulating film over the entire structure and forming a gate electrode of a thin film transistor having a predetermined size on the first insulating film; Implanting impurities into the silicon cathode electrode body and a portion of the first polycrystalline silicon film to form a source and a drain of the thin film transistor; Forming a second insulating layer over the entire structure and exposing the gate electrode and the drain of the thin film transistor; Sequentially forming a conductive film and a planarization layer on the entire structure; Performing an etch back process on the conductive film and the planarization layer to remove the conductive film of the cathode electrode portion, and then removing selected regions of the first and second oxide films to expose the cathode electrode; And patterning the conductive film to form a gate of the field emission device, a drain electrode of the thin film transistor, and a gate electrode. The method according to claim 12, wherein the insulating substrate is formed of an oxide film, a nitride film, quartz, or glass. The method according to claim 12, wherein the conversion of the first amorphous silicon film to a polycrystalline silicon film is performed by an electric furnace heat treatment or laser annealing. The method of claim 12, wherein the forming of the conical silicon cathode electrode body having a pillar on the upper part of the first amorphous silicon film comprises forming a second amorphous silicon film on the entire structure after forming the first polycrystalline silicon film. Forming a mask layer on a selected region on the second amorphous silicon film; And etching the second amorphous silicon film using the mask layer. The electric field having a control transistor of claim 15, wherein the etching of the second amorphous silicon layer is performed by performing an etch back process sequentially performing isotropic dry etching, anisotropic dry etching, and isotropic wet etching. Method of manufacturing the emitting device. The method of claim 16, wherein the isotropic wet etching is performed with a mixed solution of hydrofluoric acid (HF), acetic acid (CH ₃ COOH), and nitric acid (HNO ₃ ).