JP2008166201A - Field emission type electron source element, and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field emission type electron source element capable of stably emitting electrons even in high-speed drive required for an imaging operation and high in image quality; and an imaging device. <P>SOLUTION: This field emission type electron source element is provided with: cathode electrodes 3 with a plurality of emitters 2 of a conductive minute structure projected from a board 1 formed thereon; and gate electrodes 5 electrically insulated from the cathode electrodes 3, and is structured such that the cathode electrodes 3 and the gate electrodes 5 are arranged in a matrix-like form, and an emission current is generated by emitting electrons from tip parts of the emitters 2 by applying a voltage between the cathode electrodes 3 and the gate electrodes 5. The electron source element is also provided with high-speed drive semiconductor elements 7 controlling the emission current. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a matrix type field emission electron source element and an imaging apparatus using the same.

  It has a photoconductive film that generates and stores signal charges according to the amount of incident light, and the signal charges generated and stored in the photoconductive film are read out to an external circuit in time series by an electron beam, As an imaging device that generates an electrical signal corresponding to a spatial distribution, there is a photoconductive imaging tube.

  Further, Patent Document 1 proposes an electron tube using a field emission cold cathode element instead of a conventional thermoelectron type as an electron source. This is because the field emission cold cathode device has advantages such as a higher current density than that of the hot cathode and a small velocity distribution of emitted electrons.

  FIG. 2 shows a cross-sectional view of a conventional field emission cold cathode device. A minute conical emitter 202 is formed on a silicon substrate 201. Furthermore, gate electrodes 205 are formed at intervals of about a submicron so as to surround the emitter 202 via the insulating layer 204. When a voltage is applied through the gate electrode 205 and the substrate 201, that is, the cathode electrode 203, an electric field is concentrated on the tip of the emitter 202, and electrons are emitted in a vacuum.

The field emission cold cathode device is manufactured by a normal semiconductor process. In general, a silicon emitter is processed into a trapezoid shape using a circular thermal oxide film as a mask through a photo process. At this time, a method such as reactive ion etching using SF ₆ + O ₂ gas or anisotropic wet etching using KOH or the like is used. Next, thermal oxidation is performed to form an insulating film and a gate electrode (Nb, silicon). Next, lift-off with BHF is completed.

  FIG. 3 is a plan view showing an electrode arrangement of a matrix type field emission electron source element. A strip-shaped cathode electrode 303 extending in the horizontal axis (X-axis) direction and a strip-shaped gate electrode 304 extending in the vertical axis (Y-axis) direction orthogonal to the horizontal axis are arranged in a matrix.

  The cathode electrode 303 is formed by using a part of the silicon substrate 301, and an emitter group 302 that is an aggregate of emitters (electron emission sources) is formed on the cathode electrode 303. The emitter group 302 is shown in a circle. In one emitter group 302, several hundred to several thousand emitters are formed.

  The gate electrode 304 is disposed by being patterned on the upper side of the cathode electrode 303. Therefore, in the example of FIG. 3, the line of the cathode electrode 303 is hidden on the lower surface of the gate electrode 304.

  By driving the cathode electrode 303 and the gate electrode 304 in matrix, electrons can be emitted from the emitter group 302 at the intersection of both electrodes. By selecting each position in the X direction and the Y direction and sequentially driving them, the accumulated charge on the photoelectron surface can be read out and used as an image sensor.

  A potential can be supplied to the gate electrode 304 and the cathode electrode 303 arranged in a matrix from a gate electrode pad 305 and an emitter electrode pad 306, respectively. Both electrode pads are provided on the upper surface side of the silicon substrate 301 which is the same as the electron emission surface of the emitter.

The emitter group 302 corresponding to the intersection of the gate electrode 304 and the cathode electrode 303 has 1
This corresponds to the pixel. The emitter group 302 is separated so that it can be individually driven in units of pixels in time series. Specifically, the emitter groups 302 of the gate electrodes 304 adjacent to the left and right are separated by electrode patterning when the electrodes are formed, and the emitter groups 302 of the cathode electrodes 303 adjacent to the upper and lower sides are separated on the silicon substrate 301. They are separated by a built-in insulating film (not shown).

  In such a configuration, when each pixel is selected and emitted in time series, one of the electrodes in the X direction and Y direction is sequentially selected in time series. Emissions can be obtained from the individual emitter groups 302 by selecting the other electrode group in a time-series manner within the time during which one electrode of the selected one electrode group is selected. it can.

  As another video device using a cold cathode element, there is a display device called FED (Field Emission Display). The FED device has a problem of improving the image quality. In order to solve this problem, first, uniformity of luminance is required. That is, the emission current is stabilized.

  In the conventional FED, in order to stabilize the current output from the emitter, an electric resistor of about 1 MΩ is connected to the cathode electrode, current control by the resistor is performed, and the current itself flowing to the cathode electrode is stabilized. Such a method has been adopted (see Patent Document 2).

In addition to the current stabilization method using such a resistor, a method of stabilizing current using an NMOS transistor has been proposed (see Patent Document 3).
JP 2000-48743 A JP 2001-282179 A Japanese Patent Application Laid-Open No. 2000-323014

  Even in an imaging apparatus that uses the same cold cathode element as the FED, in order to obtain a high-quality image, the uniformity of the screen must be increased. If the uniformity or stability is poor, an erroneous electrical signal is sent to the original image with the same light amount because the emission amount is different. As a result, an image having a luminance different from that of the original image is formed. That is, as in the FED, the imaging apparatus is required to have stable emission.

  However, in the method using a resistor as in Patent Document 2, a current is supplied to the emitter via a resistor, and it is difficult to avoid voltage drop and power loss due to this resistor. For this reason, there is a problem that it is necessary to apply a high voltage to the emitter, and a required amount of current increases, leading to an increase in power consumption.

  In addition, when the configurations of Patent Documents 2 and 3 are used for the imaging tube, there is a problem regarding the operating frequency. Usually, the imaging tube is driven dot-sequentially. This has a photoconductive film that generates and accumulates signal charges according to the amount of incident light, reads the signal charges generated and accumulated in the photoconductive film to an external circuit in time series by an electron beam, This is based on the principle of generating an electrical signal corresponding to the spatial distribution of the incident light quantity.

  In the case of NTSC or VGA, the dot clock becomes 11 MHz. In the case of high-definition HDTV specifications, a dot clock exceeding 60 MHz is required. However, the configuration of each of the above patent documents does not consider the high-speed driving that is point-sequential.

  The present invention solves the conventional problems as described above, and can stably emit electrons even at a high speed required for an imaging operation, and has a high image quality field emission electron source. An object is to provide an element and an imaging device.

  In order to achieve the above object, a field emission electron source device according to the present invention includes a cathode electrode having a plurality of conductive microstructure emitters protruding from a substrate, a gate electrode electrically insulated from the cathode electrode, The cathode electrode and the gate electrode are arranged in a matrix, and when a voltage is applied between the cathode electrode and the gate electrode, electrons are emitted from the tip of the emitter and emitted. A field emission type electron source element for generating a current, comprising a high-speed driving semiconductor element for controlling the emission current.

  An imaging device of the present invention includes a cathode electrode on which a plurality of emitters having a conductive microstructure protruding from a substrate are formed, and a gate electrode electrically insulated from the cathode electrode, wherein the cathode electrode and the gate electrode are A field emission electron source element which is arranged in a matrix and emits electrons from the tip of the emitter by applying a voltage between the cathode electrode and the gate electrode to generate an emission current; An imaging apparatus includes a high-speed drive semiconductor element that controls the emission current.

  According to the present invention, it is possible to stably emit electrons even in high-speed driving required for an imaging operation, and to improve image quality.

  Since the present invention includes a high-speed driving semiconductor element that controls the emission current, it is possible to stably emit electrons even in high-speed driving required for the imaging operation, and to improve image quality. .

  In the field emission electron source element and the imaging apparatus of the present invention, the high-speed drive semiconductor element is preferably a field effect transistor.

  The high-speed driving semiconductor element preferably operates at a driving frequency of 11 MHz or more.

  The imaging apparatus according to the present invention preferably further includes a correction circuit for adjusting a gate voltage of the high-speed drive semiconductor element. According to this configuration, it is possible to make the emission current generated every time when driving sequentially.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configuration of the electrode arrangement shown in FIG. 3 is the same in the following embodiments. Therefore, FIG. 3 is also used as an electrode arrangement diagram in the following embodiment.

(Embodiment 1)
FIG. 1 shows a cross-sectional view of a field emission type electron source device according to Embodiment 1 of the present invention. This figure shows a cross-sectional view in the direction in which element isolation is performed with respect to the emitter (the Y direction in FIG. 3). The number of electron sources is omitted for simplicity. Further, as shown in FIG. 3, the gate electrode is separated in the vertical direction with respect to the dividing line of the emitter.

The silicon substrate 1 is formed with a cathode electrode 3 from which an emitter (electron emission electrode) 2 having a conductive microstructure is projected. The emitter 2 is a tower type (cone type) having a cone shape or a polygonal pyramid shape such as a quadrangular pyramid. A gate electrode 5 is disposed on the silicon substrate 1 via an insulating layer 4 (for example, an SiO ₂ insulating layer). Each emitter 2 corresponds to a pair of openings in the gate electrode 5. More specifically, the opening of the gate electrode 5 corresponds to the periphery of the tip of the emitter 2.

  An insulating film 6 is formed in the groove of the silicon substrate 1. The emitter 2 between the adjacent insulating films 6 corresponds to the emitter 2 for one pixel, that is, the emitter group 302 in FIG. For simplicity, the number of emitters 2 for one pixel is omitted.

  When the configuration of FIG. 1 is made to correspond to the configuration of FIG. 3, the emitter group 302 adjacent in the Y direction in FIG. 3 is separated by the insulating film 6.

  A predetermined potential can be applied to the gate electrode 5. An emission current can be obtained by applying a potential difference between the gate electrode 5 and the emitter 2.

In this embodiment, this current is stably controlled by the high-speed drive semiconductor element 7. In the present embodiment, an FET (Field Effect Transistor), that is, a field effect transistor is used as the high-speed drive semiconductor element 7. More specifically, a power FET formed of AlGaN / GaN was used. The FET was fabricated on the silicon substrate 1 together with the emitter 2.

  As shown in FIG. 1, the cathode electrode 3 is separated by the insulator 6 in the direction parallel to the gate electrode 5. An FET is connected to each separated cathode electrode 3.

  The emission current can be obtained as necessary and stable by changing the gate voltage of the FET. In this embodiment, a maximum current of 20 μA can be stably supplied by operating the gate voltage from the outside at a driving frequency of 11 MHz. Further, the gate voltage value applied to the FET is controlled by a correction circuit 8 that corrects the same current to flow for each line in accordance with the correction value stored in the nonvolatile memory.

In FIG. 3, the driving is performed in a dot-sequential manner in which the gate electrode 304 in the X direction is selected and the cathode electrode 304 in the Y direction is sequentially driven line by line. In the case of NTSC or VGA for this dot sequential drive, the dot clock must be performed at a drive frequency of 11 MHz. Since the FET used in this embodiment has a frequency characteristic of 11 MHz or more, it was possible to perform an emission operation without delaying the signal.

  By using a high-speed driving semiconductor element as in this embodiment, an emission current can be stably obtained even in an imaging device (imaging tube) equipped with a field emission cold cathode element, and a high-quality image is formed. I was able to.

  In this embodiment, as shown in FIG. 3, the cathode electrode 303 is divided only in the column direction (Y direction) and driven at high speed. However, the effect of this embodiment is not limited to this. Instead, the same effect can be obtained in the method of dividing the elements individually.

(Embodiment 2)
In the first embodiment, the high-speed drive semiconductor element 7 is formed on the same silicon substrate 1 as the emitter 2. However, in this embodiment, an FET section is prepared separately from the substrate 1 of the emitter 2, The FET substrate was connected by wire bonding to achieve conduction, and an imaging device was manufactured.

  Also in the present embodiment, an emission current can be stably obtained, and a high-quality image can be formed.

  That is, the high-speed drive semiconductor element 7 does not necessarily have to be provided as a part of the field emission electron source element, and may be provided as a part of the imaging apparatus as in the present embodiment.

  As described above, the present invention is useful as a field emission electron source element or an imaging apparatus that can stably obtain an emission current and can form a high-quality image.

1 is a cross-sectional view of a field emission type electron source device according to an embodiment of the present invention. Sectional drawing of an example of the conventional field emission cold cathode element. The top view which shows electrode arrangement | positioning of a matrix type field emission type electron source element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Emitter 3 Cathode electrode 4 Insulating layer 5 Gate electrode 6 Insulating film 7 High-speed drive semiconductor element 8 Correction circuit

Claims (7)

A cathode electrode formed with a plurality of conductive microstructure emitters protruding from the substrate;
A gate electrode electrically insulated from the cathode electrode,
The cathode electrode and the gate electrode are arranged in a matrix,
A field emission type electron source element that emits electrons from the tip of the emitter by applying a voltage between the cathode electrode and the gate electrode to generate an emission current,
A field emission electron source device comprising a high-speed driving semiconductor device for controlling the emission current.   The field emission electron source device according to claim 1, wherein the high-speed drive semiconductor device is a field effect transistor.   The field emission electron source element according to claim 1, wherein the high-speed driving semiconductor element operates at a driving frequency of 11 MHz or more. A cathode electrode formed with a plurality of conductive microstructure emitters protruding from the substrate;
A gate electrode electrically insulated from the cathode electrode,
The cathode electrode and the gate electrode are arranged in a matrix,
An imaging apparatus including a field emission electron source element that emits electrons from the tip of the emitter by applying a voltage between the cathode electrode and the gate electrode to generate an emission current,
An image pickup apparatus comprising a high-speed drive semiconductor element for controlling the emission current.   The imaging apparatus according to claim 4, further comprising a correction circuit that adjusts a gate voltage of the high-speed driving semiconductor element.   The imaging apparatus according to claim 4, wherein the high-speed driving semiconductor element is a field effect transistor.   The imaging apparatus according to claim 4, wherein the high-speed driving semiconductor element operates at a driving frequency of 11 MHz or more.

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