KR101042003B1 - Fabrication method of field emission devices using nano-beads - Google Patents

Abstract

The present invention relates to a method for manufacturing a field emission device, and relates to a method for manufacturing a high power field emission device by simply forming a high-density silicon tip using a nanobead manufacturing method, which is a kind of nanotechnology. More specifically, a single layer of nanobeads having a uniform diameter is formed on a substrate having a gate metal film formation and openings defined therein, and the substrate is directly etched using the nanobeads as an etching mask, or the nanobeads In this state, a method of forming a plurality of silicon tips simultaneously in an opening by forming an etch stop layer, removing nanobeads by a lift-off method, and then etching a substrate. This makes it possible to simplify the overall process because there is no high-level process that requires precise control when manufacturing the field emission device, and it is possible to form several silicon tips in one opening, and thus the electron emission density per unit area compared to the existing field emission device. Increased has the advantage of manufacturing a high density, high output field emission device.

Field Emission Nano Beads Silicon Tip High Power

Description

Fabrication method of field emission devices using nano-beads

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fabricating a field emission device. In particular, a part of the silicon tip manufacturing process is replaced by a nano-ball method to make a field emission device. The present invention relates to a method of fabricating a field emission device using nanotechnology for high power by increasing the number of devices.

The field emission device is a device using a phenomenon in which electrons are emitted when an electric field is applied to the surface of a metal or a semiconductor in a vacuum state, and has a high applicability in fields such as a display.

One of the key technologies of such field emission devices is to form metal or silicon into tips to facilitate the emission of electrons. Among them, the manufacturing process of the field emission device in the case of using the silicon tip is briefly illustrated in FIGS. 1A to 1G.

1) First step: After the insulating film 11 is formed on the silicon substrate 1 of FIG. 1A as shown in FIG. 1B, the insulating film 11 is defined at a position to form a silicon tip as shown in FIG. 1C. A material commonly used as an insulating film is a silicon oxide film, which is usually formed by an oxidation process.

2) Step 2: The silicon substrate 1 isotropically etched using the insulating film 11 defined in FIG. 1C as a mask to form a structure as shown in FIG. 1D. In this case, the isotropic etching method may use a wet etching method using an acid or a base, or may use a dry etching method such as a reactive ion etch (RIE). When the isotropic etching is performed, the side etching is caused to occur below the insulating film 11.

3) Step 3: The silicon substrate 1 is oxidized to form a silicon oxide film 12 so that the silicon tip 41 is formed as shown in FIG.

4) Fourth Step: A gate metal film 21 to be used as a gate electrode is formed as shown in FIG. 1F.

5) fifth step: the silicon oxide film 12 around the silicon tip 41 is partially removed by a wet etching method so that the insulating film 11 on the silicon tip 41 and the gate metal film 21 thereon are removed. If it is to fall off, the process is completed while the silicon tip 41 is exposed as shown in FIG.

2 is an electron micrograph of a silicon field emission device formed by the above method.

The conventional method of manufacturing a silicon field emission device as described above has a relatively complicated manufacturing process and requires precise process control such as isotropic side etching as shown in FIG. 1D, and as shown in FIG. Since only two silicon tips can be formed, there is a disadvantage in that the output power of the field emission device is high.

On the other hand, it is to manufacture a field emission device using a nanosphere (nanosphere) manufacturing method, a kind of nanotechnology, W.N. Ng et al. In Nanotechnology Vol. 19, pp. As disclosed in 255302, when the nanobead manufacturing method is used, as shown in FIG. 3, spherical nanobeads having excellent uniformity of diameter form hexagonal close packing. As the material of nano beads, polymer materials such as polystyrene, latex, and silica are widely used, and a diameter range that can be manufactured is generally known to be about 100 nm to 1 μm. When the spherical beads are concentrated, an interstice is formed between the beads and the beads as shown in FIG. 3. Therefore, it is possible to proceed with subsequent processes such as etching and lift-off by using beads as a natural mask, and in this sense, nanobead manufacturing is sometimes referred to as "natural lithography."

The basic feature of nanotechnology, which is rapidly developing in recent years, is that if the conventional semiconductor processing technology approaches the top-down method to make an extremely fine structure, the nanotechnology inverts it and uses self-assembly. It provides a bottom-up, innovative approach. The decisive weakness of nanotechnology, however, is that they have no means of controlling the self-assembly to occur only at certain locations, even in the case of nanobead manufacturing.

Therefore, by combining the basic semiconductor process and the nano-bead manufacturing method to control such self-assembly to occur only at the specific location we want, it is expected that the production of high power field emission devices can be made by a relatively simple process.

SUMMARY OF THE INVENTION An object of the present invention is to replace a part of the process of fabricating a silicon tip with a nano-ball method to make a field emission device, consequently simplifying the fabrication process of the field emission device and the number of field emission devices per unit area The purpose of the present invention is to provide a method for manufacturing a field emission device using nanotechnology for increasing the power output.

To achieve the above object, the present invention provides a method of manufacturing a field emission device, comprising: a first step of forming an insulating film on an upper side of a substrate; A second step of forming a gate metal film having an opening above the insulating film; Etching the insulating film to expose a substrate through the opening; Forming a nano-bead after etching the insulating film; The manufacturing method of the field emission device using a nano-bead characterized in that it comprises a; a fifth step of forming a tip in the opening by etching the substrate using the nano-bead as a mask.

In addition, the substrate is preferably a silicon substrate or a silicon carbide substrate.

In addition, the material of the gate metal layer is preferably a metal that is not etched in the substrate etching process of the fifth step.

In addition, the present invention provides a method of manufacturing a field emission device, comprising: a first step of forming an insulating film on an upper side of a substrate; A second step of forming a gate metal film having an opening above the insulating film; Etching the insulating film to expose a substrate through the opening; Forming a nano-bead after etching the insulating film; A fifth step of forming an etch stop layer on the entire surface of the substrate on the nanobeads; A sixth step of leaving only an etch stop layer formed in a gap between nano beads through an etching process; Another method of manufacturing a field emission device using a nano-bead comprising a; a seventh step of forming a tip in the opening by etching the exposed substrate except the etch stop layer.

In addition, the substrate is preferably a silicon substrate or a silicon carbide substrate.

In addition, the material of the gate metal layer is preferably a metal that is not etched in the substrate etching process of the seventh step.

Here, the material of the etch stop layer is nickel or titanium, the thickness is formed to 10 nm or less, it is preferable that the etch stop layer is laterally etched in the substrate etching process of the seventh step.

Using the method proposed in the present invention, it is possible to simplify the fabrication process for fabricating the field emission device, and since the silicon tip can be formed in one opening, the electron emission density per unit area is higher than that of the existing field emission device. It becomes high and can manufacture a high density, high output element.

The present invention is to achieve a further result compared to the conventional silicon field emission device manufacturing method by combining the basic semiconductor process and the nano-bead manufacturing method to control the self-assembly to occur only at the specific location we want.

Hereinafter will be described with reference to specific embodiments of the present invention. In the following embodiment, a silicon substrate is taken as an example to facilitate explanation, but the same applies to the use of a material other than silicon, for example, silicon carbide.

Example 1

1) First step: An insulating film 11 is formed on the silicon substrate 1 as shown in FIGS. 4A and 4B. The material of the insulating film is, but is not limited to, a silicon oxide film or a silicon nitride film.

2) Step 2: A gate metal film 21 to be used as a gate electrode is deposited as shown in FIG. 4C and an opening 22 is formed. The opening 22 is a position where a silicon tip is to be formed, and the opening 22 is formed by a method such as a (lithography + etching) process or a lift-off process. As the material of the gate metal film 21 to be used as the gate electrode, it is important to use a material that is not etched when etching the silicon substrate 1 in the fifth step to be described later. For example, when dry etching is performed using raw materials such as SF ₆ and CF ₄ to etch the silicon substrate 1, it is preferable to use a gate metal film material such as nickel.

3) Third Step: As illustrated in FIG. 4D, the insulating layer 11 is etched to expose the silicon substrate 1. When etching the insulating film 11, it is preferable to use an isotropic etching method so that side etching occurs below the gate metal film 21 as shown in FIG.

4) fourth step: forming nanobeads 31 as shown in FIG. Nanobead 31 is generally formed in a single layer, but is not limited thereto, and is uniformly applied to the entire surface. As mentioned above, the material of the nanobead 31 is widely used, such as polystyrene, polymer materials such as latex and silica, and the diameter range that can be produced is usually about 100nm ~ 1㎛. As shown in FIG. 4F, the size of the opening 22 is determined in advance in consideration of the diameter of the nanobead and thus formed so that the nanobeads may also be formed in the opening 22. In FIG. 4F, the seven nanobeads 31 are designed to enter the opening 22, but this is only for illustrating the concept of the present invention and is not limited thereto. In general, since the diameter of the nanobeads 31 can be formed with a very good uniformity of 1 to 2%, by controlling the size of the opening 22 and the size of the nanobeads 31, the desired number of nanobeads 31 is obtained. ) May enter the opening 22. At this time, it is important to properly determine the thickness of the insulating film 11 and the gate metal film 21 in consideration of the diameter of the nanobeads 31. If the thickness is too thick, the thickness of the opening 22 It is possible that the step increases and the nanobead 31 entering the opening becomes a double layer instead of a single layer. On the contrary, when too thin, the step gap of the opening decreases, so that the nanobead 31 in the opening 22 is exactly as shown in FIG. 4F. It may not be located.

5) Step 5: The silicon substrate 1 is etched using the nanobeads 31 as a mask to finally form the silicon tips 41 in the openings 22 as shown in FIG. 4K. The silicon substrate 1 may be etched in various ways. In general, dry etching is performed using raw materials such as SF ₆ , CF ₄ , CHF ₃ , and Cl ₂ , but is not limited thereto. Does not. The core of the fifth step is that the etch rate ratio of the nanobeads 31 and the silicon substrate 1 has an appropriate ratio, so that the nanobeads 31 gradually become as shown in FIGS. 4G to 4J. The silicon substrate 1 is also etched as it is etched down and thus the silicon substrate 1 is finally etched to find a process condition in which the conical silicon tip 41 can be formed as shown in FIG. 4J. Since the silicon substrate 1 is exposed in the gap 32, etching proceeds, and the silicon substrate portion covered with the nanobeads 31 is exposed while the nanobeads are gradually etched and are reduced in size, thereby sequentially etching. . The nano beads 31 located outside the opening 22 are all etched away in this process, and the remaining portions except the opening 22 are etched when the silicon substrate 1 is etched as mentioned in the second step. Since it is covered with the gate metal film 21 of a material which is not made, it is not affected by the etching process of the silicon substrate 1.

Example 2

1) The first to fourth steps are the same as in the first embodiment.

2) 5th step: A thin etch stop layer 51 is formed in the front surface of the silicon substrate 1 as shown in FIG. The etch stop layer 51 is required to use a material that is slowly etched while having a high etch rate ratio for silicon when etching the silicon substrate 1, the thickness is preferably several nm to several tens of nm thin. For example, a method of thinly growing metals such as nickel and titanium to 10 nm or less may be one method. The etch stop layer 51 is deposited on the nanobeads 31 or in the gaps 32 between the nanobeads.

3) Step 6: When the nanobead 31 is lifted off by an appropriate method such as wet etching, only the etch stop layer 51 formed in the gap 32 is left as shown in FIG. 4M. FIG. 4N is a schematic view of FIG. 4M taken from above. The etch stop layer 51 deposited on the nanobeads 31 is removed together with the nanobeads removed. Lifting-off step of the nano-bead is used according to the material of the nano-bead (31), for example, if the nano-bead of silica material using a hydrofluoric acid-containing aqueous solution is easily lift-off by wet etching method It is possible.

4) Step 7: The exposed silicon substrate 1 is etched to finally form the silicon tip 41 in the opening 22 as shown in FIG. The anti-etching layer 51 deposited in the opening 22 is formed of nickel or titanium, and has a thickness of 10 nm or less and a slow etching speed compared to the silicon substrate. As the silicon substrate 1 is etched in the vertical direction, the etch stop layer 51 is slowly etched to the side to reduce the size, and finally, the etch stop layer disappears and the silicon tip 41 is formed. The etch stop layer 51 formed on the remaining portions except for the opening 22 is removed on the gate metal film 21 of a material that is not etched when the silicon substrate 1 is etched, and is removed without causing any change.

1A-1G-a simplified view of a prior art method for forming a silicon tip.

Fig. 2 shows an electron micrograph of a silicon field emission device formed by a conventional method for forming a silicon tip.

Figure 3 shows an electron microscope photograph of nanobeads formed by the nanobeads manufacturing method.

4A to 4E and 4K-Schematic diagrams illustrating a method of fabricating a silicon field emission device according to Example 1 of the present invention.

4A to 4E, 4L, 4M, 4O-schematic diagrams showing a method of fabricating a silicon field emission device according to Example 2 of the present invention.

Figure 4f-a view showing a state in which the nano-bead formed in a single layer on the silicon substrate having an opening according to the present invention seen from above.

4G to 4J-a diagram depicting the formation of a silicon tip over time when the silicon substrate in the opening is etched using nanobeads as an etch mask according to Example 1 of the present invention.

Figure 4n-depicts the state after deposition of a thin etch stop layer after the formation of nanobeads by Example 2 of the present invention and removal of the nanobeads by lift-off.

<Description of Major Symbols Used in Drawings>

1: silicon substrate 11: insulating film

21: gate metal film 22: opening

31: nanobead 32: niche

41: silicon tip 51: etch stop layer

Claims (7)

In the manufacturing method of the field emission device, A first step of forming an insulating film on the upper side of the substrate; A second step of forming a gate metal film having an opening above the insulating film; Etching the insulating film to expose a substrate through the opening; A fourth step of forming nano beads on the upper layer after etching the insulating film; And a fifth step of forming a tip in the opening by etching the substrate by using the nanobeads as a mask. The method of manufacturing a field emission device using nanobeads according to claim 1, wherein the substrate is a silicon substrate or a silicon carbide substrate. The method of claim 1, wherein a material of the gate metal layer is a metal which is not etched during the substrate etching process of the fifth step. In the manufacturing method of the field emission device, A first step of forming an insulating film on the upper side of the substrate; A second step of forming a gate metal film having an opening above the insulating film; Etching the insulating film to expose a substrate through the opening; A fourth step of forming nano beads on the upper layer after etching the insulating film; A fifth step of forming an etch stop layer on the entire surface of the substrate above the nanobeads; A sixth step of leaving only an etch stop layer formed in a gap between nano beads through an etching process; And etching the exposed substrate, except for the etch stop layer, to form a tip in the opening, the method of manufacturing a field emission device using nanobeads. 5. The method of claim 4, wherein the substrate is a silicon substrate or a silicon carbide substrate. 6. The method of claim 4, wherein the gate metal layer is formed of a metal that is not etched during the substrate etching process of the seventh step. The method of claim 4, wherein the material of the etch stop layer is nickel or titanium, the thickness is 10 nm or less, the etch stop layer is etched to the side during the substrate etching process of the seventh step, characterized in that the electric field using nano-beads Method of manufacturing the emitting device.

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