JP2008097858A - Field emission element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field emission element and its manufacturing method wherein fabrication of a protrusive emitter is made easy and wherein electric field intensity is improved by sharpening the emitter tip. <P>SOLUTION: A metal layer 2 for the emitter is laminated on a glass substrate 1, and furthermore, a resist 3 having an annular opening part 3a is formed on the metal layer 2 for the emitter. Next, by anisotropic dry-etching, it is scraped from an opening part 3a of the resist 3 to the middle of the metal layer 2 for the emitter, and a recessed part is formed. After that, by using isotropic wet-etching, a protrusive part of the metal layer 2 for the emitter is fabricated, and the resist 3 is peeled off. One part of the metal layer 2 for the emitter is formed as the protrusive emitter 2a. The emitter 2a has a pyramid shape and a pyramid surface (side face) has not a linear form but an inwardly curved form. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a field emission device having a minute protruding emitter and a method of manufacturing the same.

  A field emission element having a Spindt-type emitter is used for an electron emission source in a display device and an electron emission source such as an SEM, TEM, or electron beam lithography apparatus. As shown in Patent Document 1 and Non-Patent Document 2, this field emission device is composed of a conical emitter and a gate electrode for electron extraction formed so as to surround the emitter. When a voltage is applied between the electrodes, a large electric field is applied to the tip of the emitter, causing electron emission.

  As one of the methods for manufacturing the Spindt-type emitter, as shown in FIG. 9 of Patent Document 1 and Non-Patent Document 2, an emitter electrode material is deposited using a sacrificial layer (peeling layer) to form an emitter. There is a way to do it.

  However, when the sacrificial layer is formed, there is a special manufacturing process in which evaporation is performed from an oblique direction while rotating the substrate so that it does not adhere to the inner wall surface of the insulating film in the emitter feeding film or the gate opening. There is a problem that a large vapor deposition apparatus having a height several times the diagonal length of the panel is required. In addition, when finishing the emitter in a conical shape, a difficult technique is required in which the emitter metal material must be deposited while rotating the substrate.

On the other hand, when the emitter is formed in a conical shape, as shown in FIG. 1 of Patent Document 1, after forming a cylindrical structure by isotropic dry etching, anisotropic wet etching is performed to form the conical shape. There is a method of forming.
JP 2001-110300 A Latest Trends in Flat Panel Displays (pp. 386-390) Toray Research Center

  Among the above-mentioned conventional techniques, the method of forming a conical shape by performing anisotropic wet etching after forming a columnar structure by isotropic dry etching is specially difficult, unlike the method of providing a sacrificial layer There is no process that requires technology, and manufacturing is easy, but it is difficult to sharpen the tip of the emitter into a needle shape. The same applies to the method of forming a field emission device in which a sacrificial layer is provided.

  If the tip of the emitter is not sharpened, it becomes difficult to concentrate the electric field on the tip of the emitter and the electric field strength is weakened. Therefore, in order to emit many electrons, there is a problem that the drive voltage must be increased. there were.

  The present invention was devised to solve the above-described problems, and provides a field emission device that facilitates the fabrication of a protruding emitter and sharpens the tip of the emitter to increase the electric field strength, and a method for manufacturing the same. The purpose is to do.

  In order to achieve the above object, the invention according to claim 1 is a field emission device including a protruding emitter, wherein the emitter is formed in a pyramid shape with a side surface curved inward. This is a field emission device.

  The invention according to claim 2 is the field emission device according to claim 1, wherein a spread angle of the tip portion of the pyramid shape is 10 degrees or less.

  According to a third aspect of the present invention, a first step of forming a mask having an annular opening in the emitter metal layer, and etching the emitter metal layer halfway through the opening by anisotropic dry etching A field emission device comprising: a second step; and a third step of forming an emitter by forming a part of the emitter metal layer by isotropic wet etching after completion of the second step. It is a manufacturing method.

  The invention according to claim 4 is characterized in that a plurality of openings of the mask in the first step are arranged so as to surround the top vertex of the emitter formed in the third step. This is a method for manufacturing the field emission device.

  According to a fifth aspect of the present invention, there is provided a method of manufacturing a field emission device according to the fourth aspect, wherein the number of openings of a plurality of masks arranged so as to surround the top apex of the emitter is three or four. It is.

  According to the present invention, after forming a mask having a plurality of annular openings on the emitter metal layer, anisotropic dry etching is performed partway through the emitter metal layer, and then isotropic wet etching is performed. Since the emitter is manufactured in this way, a pyramid-shaped emitter is formed, and its side surface (pyramidal surface) is curved inward, and the spread angle of the emitter tip becomes small and very sharp. The electric field strength can be increased and the driving voltage can be reduced.

  In addition, no special manufacturing process or large apparatus is required, and there are no technically difficult operations, so that the emitter can be easily manufactured.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the main steps of the method for manufacturing a field emission device of the present invention and the cross-sectional shape of the side surface of the emitter. As shown in FIG. 1A, an emitter metal layer 2 is laminated on a glass substrate 1, and a resist (mask) 3 having an annular opening 3 a is formed on the emitter metal layer 2.

  Next, as shown in FIG. 1B, by anisotropic dry etching, the resist 3 is shaved from the opening 3a to the middle of the emitter metal layer 2 to form a recess. The concave portion is formed in a truncated cone shape that becomes narrower toward the bottom surface. Thereafter, as shown in FIG. 1 (c), isotropic wet etching is used to produce a protruding portion of the emitter metal layer 2, and the resist 3 is peeled off as shown in FIG. 1 (d). For example, a part of the emitter metal layer 2 is formed as a protruding emitter 2a. The lower region 2b of the emitter metal layer 2 is used as a cathode electrode.

  The emitter 2a has a pyramid shape such as a three-sided pyramid or a four-sided pyramid, and the cone surface (side surface) is not linear but curved inward as shown in FIG. . In this way, by forming a cone surface curved inward, the spread angle of the head apex of the emitter 2a can be made extremely small, and a sharp tip can be formed. The emitter metal layer 2 is used not only for the formation of the emitter 2a but also for the formation of the cathode electrode 2b. As the material, Mo (molybdenum), Cr (chromium) or the like having a low work function is used.

  Specific examples of the resist (mask) 3 having the annular opening 3a shown in FIG. 1 are shown in FIGS. FIG. 16 shows the configuration of a part of a field emission device in which field emission elements are two-dimensionally formed. The stripe-shaped cathode electrode 2b and the stripe-shaped gate electrode 5a are vertically and horizontally arranged. The emitter 2a can be manufactured by using a mask having a square shape as shown in FIGS.

  2 and 3, the opening 3a provided in the resist 3 has a circular shape. The opening 3 may have an elliptical shape, but it is desirable to have a circular shape considering the shape of the finally formed emitter and the spread angle of the tip. 2 and 3 indicate the top vertex position of the protruding emitter 2a. For comparison, in both FIGS. 2 and 3, the area of the resist 3 is the same, and the area of the opening 3a is also the same.

  In FIG. 2, the circular openings 3a are arranged in a square shape, and four openings 3a are arranged so as to surround the head vertex position (x mark) of the emitter 2a. In this way, when the openings 3a are arranged, the etching proceeds from the opening 3a in a circular shape toward the back, so that the emitter shape seen from above is a rectangular shape as shown by the broken line in the figure. Thus, the entire emitter shape is a quadrangular pyramid.

  On the other hand, in FIG. 3, the circular openings 3a are arranged alternately in the upper row and the lower row, and the three openings 3a are arranged so as to surround the head vertex position (x mark) of the emitter 2a. It has a structure. Thus, when the openings 3a are arranged, the etching proceeds from the opening 3a in a circular shape toward the back, so that the emitter shape seen from above is triangular as shown by the broken line in the figure. Thus, the entire emitter shape is a triangular pyramid.

  By the way, the number of top vertex positions (x marks) of the emitter 2a is larger in FIG. 3 than in FIG. This is related to the shape of the emitter to be manufactured, and when the emitter shape is a triangular pyramid, the arrangement density of the openings 3a can be maximized and the number of emitters can be increased. It is.

  Next, a method for manufacturing a field emission device using a resist as shown in FIGS. 2 and 3 will be described in detail with reference to FIGS. 4 to 14 show the regions where the field emission elements of the field emission device shown in FIGS. 15 and 16 are formed.

  First, as shown in FIG. 4, an emitter metal layer 2 for producing an emitter is laminated on a glass substrate 1 by sputtering or the like. The emitter metal layer 2 is finally used for both the production of the emitter and the production of the cathode electrode (cathode). The emitter metal layer 2 is formed in a plurality of stripes in the same manner as the cathode electrode 2b in the field emission device shown in FIG.

An emitter forming resist 3 is applied on the emitter metal layer 2. Thereafter, exposure is performed and the resist 3 is patterned to form a circular opening 3a as shown in FIG. When Mo is used for the emitter metal layer 2, anisotropic dry etching by RIE using CF ₄ as an etching gas is performed, and as shown in FIG. Form. The cross section of the concave portion is as shown in FIG. 6. At this time, an inclination angle θ1 is generated between the side surface of the concave portion and the vertical direction.

Next, isotropic wet etching is performed using a solution in which H ₃ PO ₄ (phosphoric acid) and HNO ₃ (nitric acid) are mixed at a ratio of 1: 1, and the emitter metal layer 2 is formed into the shape shown in FIG. Is processed. A part of the emitter metal layer 2 is formed in a protruding shape, and this protruding portion becomes the emitter 2a.

  By the isotropic wet etching, the side surface of the emitter 2a is formed not in a straight line but in a curved shape inward, so that the spread angle θ2 of the tip of the emitter 2a can be narrowed. Further, since the spread angle θ2 of the tip of the emitter 2a is θ2≈2 × θ1, if θ1 is reduced in the process of FIG. 6, θ2 is also reduced, and the tip of the emitter 2a can be made very sharp. The spread angle θ2 of the tip of the emitter 2a can be manufactured within a range of 10 degrees or less, and can be reduced to about 5 degrees.

Thereafter, as shown in FIG. 8, the resist 3 is removed by ultrasonic cleaning with an organic solvent or the like. Next, as shown in FIG. 9, an insulating film 4 such as SiO ₂ is laminated on the emitter metal layer 2. At this time, deposition is performed so that the base height H1 of the laminated portion of the insulating film 4 is higher than the height H2 up to the top of the emitter 2a. Then, the entire wafer is rotationally polished by CMP (Chemical Mechanical Polishing) to flatten the wafer surface as shown in FIG. In this case, polishing is performed in consideration of the distance between a gate electrode, which will be described later, and the tip of the emitter 2a.

  Next, as shown in FIG. 11, a gate metal layer 5 is deposited on the polished insulating film 4 by sputtering. As with the emitter metal layer 2, Mo or Cr is used for the gate metal layer 5. The gate metal layer 5 and the emitter metal layer 2 are both formed in a stripe shape, and are formed so as to cross vertically and horizontally as shown in FIG.

  A resist 6 is applied on the gate metal layer 5 and exposed, and the resist 6 is patterned to form a circular opening as shown in FIG. Thereafter, wet etching is performed to remove a part of the gate metal layer 5, and further wet etching for exposing the emitter 2a is performed to form an emitter hole 7 as shown in FIG. The tip of 2a is exposed.

Here, when Mo is used for the gate metal layer 5, isotropic wet etching is performed using a solution in which H ₃ PO ₄ (phosphoric acid) and HNO ₃ (nitric acid) are mixed at a ratio of 1: 1. A buffered hydrofluoric acid solution is used for wet etching of the insulating film 4 made of SiO ₂ . Finally, the resist 6 is removed to complete a field emission device including a gate electrode 5a, an emitter 2a, and a cathode electrode 2b as shown in FIG.

Here, a schematic diagram of the entire field emission device in which the field emission elements are arranged two-dimensionally is as shown in FIG. 15, but the portion where the emitter 2a is formed is enlarged in FIG. Show. As shown in FIG. 14, when three emitters 2a are produced in a cross-sectional view, the region where the gate electrode 5a and the cathode electrode 2b cross in FIG. 3 emitter holes 7 and emitters 2a are formed.

It is a figure which shows the main manufacturing processes of the field emission element in this invention, and an emitter shape. It is a figure which shows an example of the mask shape used when producing an emitter. It is a figure which shows an example of the mask shape used when producing an emitter. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows one manufacturing process of the field emission element of this invention. It is a figure which shows the arrangement | positioning state of the metal for emitters in the field emission apparatus, and the metal for gates. It is a figure which shows the field emission apparatus in which the field emission element was formed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Emitter metal layer 3 Resist 3a Opening 4 Insulating film 5 Gate metal layer 6 Resist 7 Emitter hole

Claims (5)

A field emission device having a protruding emitter,
The field emission device according to claim 1, wherein the emitter is formed in a pyramid shape with side surfaces curved inward.   2. The field emission device according to claim 1, wherein a spread angle of the tip portion of the pyramid shape is 10 degrees or less. A first step of forming a mask having an annular opening in the emitter metal layer;
A second step of etching the metal layer for emitter partway through the opening by anisotropic dry etching;
A method of manufacturing a field emission device, comprising: a third step of forming an emitter by forming a part of a metal layer for emitter by isotropic wet etching after the second step is completed.   4. The method of manufacturing a field emission device according to claim 3, wherein a plurality of openings of the mask in the first step are arranged so as to surround a top vertex of the emitter formed in the third step.   5. The method of manufacturing a field emission device according to claim 4, wherein the number of openings of the plurality of masks arranged so as to surround the top vertex of the emitter is three or four.

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