KR101034894B1 - Fabrication method of field emission devices using micro-masking during plasma etching - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a field emission device having a field emission tip composed of a material of a conductive substrate. In particular, a high density field emission tip is very simple by using a micro masking phenomenon generated during a plasma dry etching process. It relates to a method that can be formed. More specifically, when the trench is formed by plasma dry etching on the conductive substrate having the gate electrode formation and the openings defined therein, under certain process conditions, a micro mask is formed on the conductive substrate during the plasma dry etching process to prevent etching of the conductive substrate. The film acts as an anti-etch mask, and consequently a method for forming trenches and field emission tips simultaneously. Using the method proposed in the present invention it is possible to manufacture a high-density, high-output field emission device made of a conductive substrate material through a very simple process.

Micromask Field Emission Plasma Etch Field Emission Tip

Description

Fabrication method of field emission devices using micro-masking during plasma etching

The present invention relates to a method for fabricating a field emission device, and when fabricating a field emission device having a field emission tip made of a conductive substrate, a microdensing phenomenon generated during the plasma dry etching process is used. It relates to a method for manufacturing a field emission device that can be formed easily.

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 where a silicon tip is to be formed as shown in FIG. 1C. The 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) Third step: The silicon substrate 1 is oxidized to form a silicon oxide film 12 so that the field emission tip 41 is formed as shown in FIG.

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

5) fifth step: the silicon oxide film 12 around the field emission tip 41 is partially removed by a method such as wet etching to remove the insulating film 11 on the field emission tip 41 and the gate electrode 21 thereon. If this is to be separated, the process is completed while the field emission 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.

An object of the present invention is to use a micro masking phenomenon generated during the plasma dry etching process when fabricating a field emission device having a field emission tip composed of a material of a conductive substrate micro masking that can form a very dense field emission tip very simply It is an object of the present invention to provide a method for manufacturing a field emission device using the phenomenon.

In order to achieve the above object, the present invention provides a method for manufacturing a field emission device, comprising: a first step of forming an insulating film on an upper side of a conductive substrate; Forming a gate electrode having an opening on the insulating layer; Etching the insulating film to expose a conductive substrate through the opening; A fourth step of forming a micro mask on a surface of the conductive substrate in the opening in the process of etching the conductive substrate by plasma dry etching after the insulating film is etched; And a fifth step of continuing the plasma dry etching process to etch the conductive substrate to form a tip or probe capable of field emission under the micro mask in the opening. The manufacturing method of the field emission device is a technical gist.

Further, after forming the tip or probe capable of field emission in the fifth step, the micromask remaining on the field emission tip or probe through the heat treatment process reacts with the field emission tip or probe of the conductive substrate material, thereby It is desirable to change the tip of the discharge tip or probe to a highly conductive compound.

In addition, it is preferable to further form an insulating film on the side and trench of the field emission tip or probe, wherein the insulating film is manufactured using a cleaning method using a mixed solution of sulfuric acid and hydrogen peroxide, or an ultraviolet irradiation method in an ozone atmosphere. desirable.

In addition, the conductive substrate is preferably silicon or silicon carbide, and the conductive substrate preferably has a multilayer structure in which a conductive material is formed on an upper layer of an arbitrary base material.

In addition, the material of the gate electrode is preferably any one of nickel, titanium and aluminum or alloys thereof.

In addition, the micro mask is preferably formed on the surface of the conductive substrate through the physical sputtering or chemical reaction with the etching species (etchant) and the accompanying redeposition process during the dry etching process.

In addition, the material of the gate electrode is preferably a material that is not etched during the etching process of the conductive substrate by the plasma etching process.

Using the method proposed in the present invention, it is possible to simplify the fabrication process for fabricating the field emission device, and to form a plurality of field emission tips or probes in one opening, electrons per unit area compared to the existing field emission device. As the emission density increases, there is an effect that a high density, high output field emission device can be manufactured.

The present invention relates to a method of manufacturing a field emission device using a micro masking phenomenon that can form a trench and a field emission tip at the same time in a single plasma dry etching process, unlike the complicated manufacturing process of the prior art, in the plasma dry etching process One of the typical process defects that may occur is the use of micromasking.

The plasma dry etching process is a process that is essentially used for manufacturing a semiconductor device. However, depending on the plasma dry etching process conditions, some kind of micro mask is formed on the portion to be etched to prevent dry etching, and thus, after the etching is completed, unwanted structures such as irregularities, probes, or tips may be formed on the surface. This is called a micro masking phenomenon.

This micro masking phenomenon may be caused by the material forming the inner wall of the plasma dry etching equipment, or by a chemical species of some kind that exists on the surface of the specimen to be etched by physical sputtering or plasma. It is a phenomenon caused by being formed on the etched part by changing to a material that is not easily etched through a chemical reaction. For reference, FIG. 3 is an electron micrograph showing the appearance of micro masking phenomenon when the inventors etch a silicon carbide substrate using a nickel mask. As shown in FIG. 3, the micromasking is generally formed in a probe shape, which is very advantageous for forming a field emission device.

This micromasking phenomenon was described by P. Dixit et al. In Journal of the Electrochemical Society, Vol. As mentioned in the paper published in G771, “Effect of clamping ring materials and chuck temperature on the formation of silicon nanograss in deep RIE”, P. Chabert et al., Published in 2000 by Applied Physics Letters No. 76 pp. As mentioned in the 2310 paper, "High rate etching of 4H-SiC using a SF ₆ / O ₂ helicon plasma," when etching silicon carbide substrates, or YP Yin et al. As mentioned in the paper `` Investigation of surface roughening of low-k films during etching using fluorocarbon plasma beams '' published in No. 24 PP.2360, this phenomenon occurs regardless of the material to be etched.

Until now, all the studies have been directed to finding a way to remove such micro masking phenomenon, but the present invention devised a method that can advantageously utilize the micro masking phenomenon in the fabrication of the field emission device by using the reverse direction. It was.

As described above, a method of simply manufacturing the field emission device using the micro masking phenomenon will be described in detail with reference to the following examples. However, this is only one way of actually implementing the core idea presented in the present invention, and the core idea of the present invention is not limited thereto.

Example 1

1) First step: An insulating film 11 is formed on the conductive substrate 2 as shown in FIGS. 4A and 4B. In general, the material of the insulating film 11 is a silicon oxide film or a silicon nitride film, but is not limited thereto. In this case, the conductive substrate 2 may be made of a single conductive material as a whole, or may be formed of a multilayer structure formed of two or more materials and having a conductive material formed on an upper layer of an arbitrary base material.

2) Second step: A gate electrode 21 is formed on the insulating film 11 and an opening 91 is formed as shown in FIG. 4C. The opening 91 is a position at which the field emission tip is to be formed, and the opening is formed by a method such as a (lithography + etching) process or a lift-off process. The gate electrode 21 serves as an electrode for applying a voltage to induce field emission of electrons in the field emission device to be finally formed and at the same time serves as an etch mask in a dry etching process for forming the opening 91. Since it is also performed simultaneously, it is important to use a material that is not etched when etching the conductive substrate 2. For example, when the material of the conductive substrate 2 is silicon, dry etching is generally performed using raw materials such as SF ₆ and CF ₄ , in which case nickel (Ni), titanium (Ti), and aluminum (Al) are used. Or metal film materials such as alloys thereof. The gate electrode 21 may have a single layer or a multilayer structure of a conductive material and an insulating material. In any case, the gate electrode 21 may be a material that can easily cause micro masking.

3) Third Step: As shown in FIG. 4D, the insulating layer 11 is etched to expose the conductive substrate 2. When etching the insulating film 11, it is generally preferable to use an isotropic etching method so that side etching occurs below the gate electrode 21 as shown in FIG. 4D. For example, when the insulating film 11 is a silicon oxide film Wet etching using a solution such as hydrofluoric acid or buffered oxide etch (BOE), or a plasma dry etching process having strong isotropy may be used.

4) Step 4: The conductive substrate 2 is etched by the plasma dry etching process as shown in FIG. 4E. At this time, if the process parameters are properly adjusted, the micro masks 22 and 23 are deposited on the surface of the conductive substrate 2 in the opening 91 in the process of dry etching. In the plasma dry etching process, reference numeral 22 denotes a micro mask incident to an opening, and reference numeral 23 denotes a micro mask deposited on a conductive substrate. Arrow 81 shows the flow of ions (hereinafter referred to as 'ions') incident on the conductive substrate during the plasma dry etching process.

The micro mask 23 deposited on the conductive substrate is not etched well, and the material constituting the inner wall of the plasma etching apparatus is chemically reacted with physical sputtering or etchant during the dry etching process. The material formed on the surface of the conductive substrate through the subsequent redeposition process or present on the surface of the field emission device, for example, the material of the gate electrode 21, is physically sputtered or etched during the dry etching process. It is formed on the surface of the conductive substrate through a chemical reaction with) and subsequent redeposition. Which cause prevails depends largely on the individual equipment or process conditions and the surface structure of the specimen to be etched. The micro mask 23 deposited on the conductive substrate is formed on the conductive substrate to serve as an etch stop mask that prevents etching of the conductive substrate, so that the trench and the field emission tip can be simultaneously formed.

For example, assuming that the micromasking phenomenon is caused by using a material constituting the gate electrode 21 for better understanding, the plasma dry etching process conditions, the material of the conductive substrate 2, and the gate electrode 21 are used. ) Are closely related to each other. For example, when the material of the conductive substrate 2 is silicon (Si) or silicon carbide (SiC), the raw material gas used for the plasma dry etching generally includes CF ₄ or SF ₆ containing fluorine (F). In this case, a mixture of gases such as oxygen (O ₂ ) and argon (Ar) is often used as necessary. In this case, it is common to form the gate electrode 21 made of a material such as nickel or aluminum having high etching resistance to the raw material gas containing fluorine.

Process variables of the plasma dry etching process include pressure, temperature, type and mixing ratio of raw gas, plasma power, and substrate bias. In order to cause micro masking by physical sputtering of the gate electrode 21, a conductive substrate ( In order to increase the energy of the ions 81 incident on 2), the substrate bias is adjusted to have a large negative value, and the ions 81 collide with other gas atoms in the process of being incident on the conductive substrate 2. It is advantageous to lower the pressure in order to minimize scattering. In addition, in order to easily sputter atoms on the surface of the gate electrode 21, it is advantageous that the atomic amount of the incident ions 81 is as large as possible, because the momentum increases. For example, SF ₆ may be more advantageous among CF ₄ and SF ₆ , which are gases containing fluorine ions. In addition, when all process conditions are the same, the micro masks 22 and 23 are more easily formed when the material of the gate metal film 21 is a material having a high sputter yield.

The structure of FIG. 5 uses SF ₆ as described above and applies a large negative substrate bias during plasma dry etching so that ions containing sulfur (S) having a relatively large atomic weight are incident on the silicon substrate 1 with a large energy. It is a shape obtained under the formed process conditions. During the etching of the trench 42 using a mixed gas of SF ₆ and O ₂ , the silicon field emission tips 45 were naturally formed simultaneously by the micro masking phenomenon, and nickel was used as the gate electrode 21 material.

The plasma etching process was performed under a pressure of 30 mTorr, a plasma power of 550 W, and a substrate bias of about -100 V to form a structure as shown in FIG. 5. This is the case where the micro masking phenomenon is caused by utilizing the gate electrode 21 present on the surface of the specimen to be etched, and the same principle is applicable to the case of using the material of the inner wall of the dry etching equipment.

5) Step 5: When the plasma dry etching process is performed by forming the general process conditions as described above, the micro mask 23 deposited on the conductive substrate is formed, which prevents the etching of the conductive substrate 2. As shown in FIG. 4E, a field emission tip or probe (hereinafter, referred to as an 'field emission tip') 41 having a shape favorable to field emission starts to be formed, and finally, as shown in FIG. Field emission tips 41 are formed. At this time, if a micro masking phenomenon is caused by using the gate electrode 21, the micro mask 23 made of a metal film constituting the gate electrode is formed on the top of the field emission tip 41 as illustrated in FIG. 4F. Is likely to remain. In this case, another application is possible as described above in the second embodiment.

Example 2

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

2) 5th step: The micromask 23 remaining on the structure of the field emission tip after the predetermined heat treatment process in the state in which the field emission tip 41 is formed as shown in Figure 4f is a field emission tip of the conductive substrate material React with (41) to change the tip of the field emission tip to a compound with good conductivity. For example, when the material of the micro mask 23 is nickel and the material of the conductive substrate 2 is silicon or silicon carbide, the material of the micro mask 23 is changed to nickel silicide through a heat treatment process. Silicide has excellent conductivity and is widely used as an electrode material in silicon semiconductor devices. This is to change the material of the micro mask 23 to a compound having excellent conductivity such as silicide so that the field emission of electrons at the tip of the field emission tip 41 can occur more smoothly.

After that, a thin insulating film 13 may be formed on the side surface and the trench 42 of the field emission tip 41 through an appropriate process as necessary. For example, the insulating layer 13 may be immersed in a mixed solution of (sulfuric acid + hydrogen peroxide) heated to about 100 ^° C., for example, by dipping the conductive substrate 2 having the field emission tip 41 therein to perform organic cleaning. When the material of (2) is silicon or silicon carbide, a very thin silicon oxide film of about 1 nm is formed. Alternatively, for example, when the conductive substrate 2 on which the field emission tip 41 is formed is exposed while irradiating ultraviolet rays in an ozone (O ₃ ) atmosphere, when the material of the conductive substrate 2 is silicon or silicon carbide, the thickness is about several nm. A very thin silicon oxide film is formed on the side of the field emission tip 41 and the trench 42. In addition, there may be various methods, and further detailed description thereof will be omitted herein.

The purpose of forming the insulating film 13 is to increase the efficiency of the field emission by minimizing the defect states present in the side portions except for the end where the field emission occurs in the field emission tip 41. . In the formation of the insulating film 13, the core concept is that the insulating film 13 is not formed on the micro mask 23 formed at the end of the field emission tip 41, and the side surface and the trench 42 of the field emission tip 41 are not formed. ) Is to ensure the condition that the insulating film 13 can be formed only, the method that can most easily achieve the above object is to use a mixed solution (sulfuric acid + hydrogen peroxide), or low temperature as mentioned above And at a low oxygen partial pressure, the micro mask 23 uses various process technologies capable of oxidizing only the surface of the exposed conductive substrate 2 without being oxidized. The portion of the micro mask 23 reacts with the conductive substrate 2 to form a stable compound, while the sides of the field emission tip 41 and the portion of the trench 42 are thermodynamically due to dangling bonds. This unstable state allows for this selective oxidation.

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 fabricated by the prior art.

FIG. 3 is an electron micrograph showing the appearance of micro masking phenomenon when plasma etching the silicon carbide substrate using a nickel mask. FIG.

Figures 4a-4g-sequentially showing the method proposed in the present invention for producing a field emission device having a field emission tip consisting of a material of a conductive substrate.

5 shows electron micrographs of trenches and silicon field emission tips fabricated from the method presented in the present invention.

<Description of Major Symbols Used in Drawings>

1: silicon substrate 2: conductive substrate

11: insulating film 12: silicon oxide film

13: insulating film 21: gate electrode

23: micro mask deposited on conductive substrate

41: field emission tip 42: trench

45: silicon field emission tips

81: Flow of ions incident on the conductive substrate during the plasma dry etching process

91: opening

Claims (10)

In the manufacturing method of the field emission device, A first step of forming an insulating film on the conductive substrate; Forming a gate electrode having an opening on the insulating layer; Etching the insulating film to expose a conductive substrate through the opening; A fourth step of forming a micro mask on a surface of the conductive substrate in the opening in the process of etching the conductive substrate by plasma dry etching after the insulating film is etched; And a fifth step of continuing the plasma dry etching process to etch the conductive substrate to form a tip or probe capable of field emission under the micro mask in the opening. Method for manufacturing field emission device. The method of claim 1, wherein after forming the tip or probe capable of field emission in the fifth step, a micro mask remaining on the field emission tip or probe through a heat treatment process reacts with the field emission tip or probe of the conductive substrate material. Method for manufacturing a field emission device using a micro masking phenomenon, characterized in that for changing the tip of the field emission tip or probe to a highly conductive compound. The method of manufacturing a field emission device using a micro masking phenomenon according to claim 1 or 2, further comprising an insulating film formed on the side surface and trench of the field emission tip or probe. 4. The method of manufacturing a field emission device using a micro masking phenomenon according to claim 3, wherein the insulating film is manufactured by a cleaning method using a mixed solution of sulfuric acid and hydrogen peroxide or by an ultraviolet irradiation method in an ozone atmosphere. The method of manufacturing a field emission device using a micro masking phenomenon according to claim 1 or 2, wherein the conductive substrate is silicon or silicon carbide. The method of manufacturing a field emission device using a micro masking phenomenon according to claim 1 or 2, wherein the conductive substrate has a multilayer structure in which a conductive material is formed on an upper layer of an arbitrary base material. The method of claim 1, wherein the gate electrode is made of one of nickel, titanium, and aluminum or an alloy thereof. 4. 3. The conductive substrate of claim 1, wherein the micro mask comprises a conductive substrate through a chemical reaction with physical sputtering or an etchant during a dry etching process of the constituent material of the gate electrode and accompanying redeposition. A method of manufacturing a field emission device using a micro masking phenomenon, characterized in that formed on the surface. The process of claim 1 or 2, wherein the micro mask comprises a chemical reaction with physical sputtering or an etchant during the dry etching process of a material constituting the inner wall of the plasma dry etching apparatus and a redeposition process accompanying the same. Method for manufacturing a field emission device using a micro masking phenomenon characterized in that formed on the surface of the conductive substrate via. The method of claim 1, wherein the gate electrode is made of a material that is not etched during an etching process of the conductive substrate by a plasma etching process.

Images