KR101533526B1 - Method for fabricating slanted nanopillar using plasma etching - Google Patents

Abstract

The present invention provides a method of fabricating a leaning nanopillar by using a plasma etching process, comprising the steps of: preparing a material to be etched, formed with a silicon oxide film; forming a carbon fluoride group on the silicon oxide film; processing the silicon oxide film and the carbon fluoride group with plasma generated by fluorine compound gas; and plasma-etching the material.

Description

[0001] METHOD FOR FABRICATING SLANTED NANOPILLAR USING PLASMA ETCHING [0002]

The present invention relates to a method of etching by plasma etching. Specifically, the present invention relates to a method of plasma etching to form a tilted nanopillar.

Silicon nanoparticles have low reflectance and high absorptivity and are used as core devices in various fields such as image sensor, photodetector, terahertz application, and solar cell. Typical methods for fabricating such nano pillars are chemical vapor deposition, plasma etching, and wet etching.

The method using chemical vapor deposition is referred to Korean Patent Application No. 10-2009-0015872, and the method using wet etching is referred to Korean Patent Application No. 10-2010-0073212.

A method of manufacturing a nanopillar using chemical vapor deposition is a method of growing a nanopillar by depositing a silicon particle on a surface of a crucible after forming a metal or a nitride compound or oxide on the surface thereof. The nanocrystals formed by this method have a disadvantage in that the growth direction is always limited to the direction perpendicular to the substrate and the angle of the nanopillar can not be controlled. In the case of inclined nano-columns, it is possible to maximize the absorptivity and reduce the reflectance remarkably.

The nano-pillar fabrication method using the plasma etching method is a method of etching a substrate by forming a SiOxFy nucleus on a silicon surface by mixing a fluorine-containing gas and an O ₂ gas, and using the mask as a mask. This is disadvantageous in that it is difficult to control the process because SiOxFy nucleation is sensitive to plasma parameters. Further, in the case of plasma etching, since the sheath is formed on the surface of the substrate and the ions accelerated perpendicularly to the equipotential line of the sheath are vertically incident on the substrate regardless of whether the substrate is inclined or not, Is formed.

In the wet etching method, a metal group is formed on a silicon substrate, and then the substrate is etched using the metal as a mask. For example, when a silicon substrate is immersed in a HF / AgNO ₃ solution to form an Ag group on a silicon surface, wet etching is performed in the same solution to form a nano-pillar. This method has a merit that the process is very simple, but it has a disadvantage in that it can not produce a high aspect ratio nanopillar with an isotropic satellite and the direction of the nanopillar is generated in a direction perpendicular to the substrate.

An object of the present invention is to provide a new type of plasma etching technique using plasma etching, which overcomes the limitations of the nanopillar forming method developed by the conventional chemical vapor deposition method, the plasma etching method, and the wet etching method.

The present invention relates to a method of manufacturing a nano-column, comprising the steps of: preparing a crucible having a silicon oxide film; Forming a fluorocarbon group on the silicon oxide film; Treating the silicon oxide film and the fluorocarbon group with a plasma by a fluorine compound gas; And a step of plasma-treating the seed grains to etch the seed grains.

The term "nanopillar" as used herein means a nano-sized structure used in various fields such as nano hair, nanowire, and nanostructure in academia. Silicon nanoparticles have low reflectance and high absorptivity and are used as core devices in various fields such as image sensor, photodetector, terahertz application, and solar cell.

The crucible refers to a material, for example a substrate, which is etched by plasma etching.

The fluorocarbon group means a group consisting of a fluorocarbon material in a part of the silicon oxide film without covering the entire silicon oxide film. For example, it may refer to a group of droplets in the form of a droplet having a certain arbitrary size in the silicon oxide film when viewed from above.

In one embodiment, the fluorocarbon group is formed from a plasma of fluorocarbon gas. In order to form a fluorocarbon group from the plasma of fluorocarbon gas on the silicon oxide film, the plasma of the fluorocarbon gas is applied with a bias voltage not exceeding a threshold energy required for etching the silicon oxide film and the silicon oxide film .

When plasma is generated by applying a bias voltage exceeding the threshold energy, there is a possibility that the carbon monoxide or the silicon oxide film may be etched without forming the fluorocarbon group in the seed crystal. Therefore, a bias voltage not exceeding the threshold energy is applied to generate plasma.

In one embodiment, the fluorocarbon gas used to form the fluorocarbon group includes at least one of CF ₄ , C ₄ F ₈ , C ₄ F _6, CH ₂ F _2, and CHF ₃ .

In one embodiment, the crucible is a silicon specimen.

In one embodiment, the silicon oxide film is a silicon natural oxide film in which the silicon specimen is naturally oxidized.

The silicon natural oxide film is formed by oxygen in the air spontaneously reacting with the silicon surface, and is formed, for example, by exposing a silicon wafer to air at room temperature for one day or more. This is merely an embodiment for oxidizing the silicon oxide film. If the silicon oxide film can be obtained, its oxidation form and oxidation method are not limited.

In one embodiment, the plasma of the fluorine compound gas, the silicon oxide film, and the fluorocarbon group react with each other by the plasma treatment with the fluorine compound gas to form a SiOxFy-based mask.

The silicon oxide film forms SiOxFy in the fluorocarbon group formed on the crucible using the plasma generated by the fluorine compound gas. The formed SiOxFy can serve as a mask to prevent the etching of the etching solution during etching.

In one embodiment, the fluorine compound gas used for forming the SiOxFy-based mask includes at least one of SF ₆ , CF ₄ , C ₄ F ₈ , C ₄ F ₆ , CH ₂ F _2, and CHF ₃ .

In one embodiment, the fluorine compound gas may include O ₂ or Ar gas.

It is possible to control the oxygen content of SiOxFy formed through the plasma treatment with the fluorine compound gas according to the content of O ₂ or Ar gas.

In one embodiment, the diameter of the nanopillar can be controlled by controlling the plasma treatment time by the fluorocarbon gas.

As the plasma treatment time by the fluorocarbon gas becomes longer, the size of the fluorocarbon group formed on the silicon oxide film becomes larger. As the size of the fluorocarbon group increases, the size of the SiOxFy-based mask increases, and thus only the portion excluding the mask is etched, thereby increasing the diameter of the nanopillar formed after the etching. Conversely, the shorter the plasma treatment time, the smaller the fluorocarbon group size. Therefore, the diameter of the nanopillar formed by the above principle becomes small.

In one embodiment, the crucible is located within the Faraday cage.

The Faraday cage means a closed space made of a conductor. When a Faraday cage is installed in a plasma, a sheath is formed on the outer surface of the box, and the electric field inside the Faraday cage is kept constant. At this time, replacing the top surface of the Faraday cage with a fine grid, a sheath is formed along the surface of the grid. Therefore, the ions accelerated in the sheath horizontally formed on the grid surface can be arbitrarily adjusted according to the slope of the sample holder since the ions enter the inside of the box and then reach the substrate while maintaining the direction of incidence.

According to an embodiment of the present invention, the nano-pillar manufacturing method is characterized in that the angle between the open face of the Faraday cage and the face of the wedge angle is adjusted to obliquely etch the wedge. Here, the open face means the upper face of the grid form of the Faraday cage, and corresponds to the reference numeral 51 in FIG.

Inside the Faraday cage, you can adjust the angle of each piece by inserting a sample holder to adjust the angle of each part. Accordingly, when the plasma enters perpendicularly to the open surface of the Faraday cage, the angles of the angles can be adjusted by adjusting the angle of the sample holder and the like so that the nano pillars can be inclinedly etched so as to have a certain angle.

In one embodiment, the method further includes depositing a protective film on the etched wall surface by plasma treatment containing carbon fluoride gas after plasma etching and etching the seed crystal.

When a protective film is deposited on the etched wall, the etched protective film is etched on the etched wall surface to etch the nano - pillars, and the nano - pillars become anisotropic.

In one embodiment, the step of plasma etching and etching the seed crystal and the step of depositing a protective film by plasma treatment containing fluorocarbon gas on the etched wall surface are repeated two or more times in order.

That is, plasma etching is performed to plasma etching, and a protective film is deposited on the etched wall surface. Then, plasma etching and plasma etching of the crucible and the protective film maintains the diameter of the etching hole on the protective film wall surface as it is because the protective film is etched instead of the etching surface of the etching film. Then, when a protective film is deposited on the etched wall and etching is performed on the etched wall and the protective film, the depth of the etched hole becomes deeper and the diameter remains unchanged. Repeating two or more times in a row means repeating this process cyclically.

The nano-pillar fabrication method proposed in the present invention is advantageous in that it can realize a high aspect ratio structure of a nano-pillar as compared with the conventional method, can manufacture a large area of a nano-pillar, and has excellent process yield.

In addition, since the angle of the nano pillar can be arbitrarily adjusted, the reflectance of the nano pillar is drastically lowered and the absorption rate is increased.

The present invention is expected to play a key role in various fields such as an image sensor, a photodetector, a terahertz application, and a solar cell.

FIG. 1 is a process diagram illustrating an exemplary method for producing a nanopillar according to the present invention, as one embodiment of the present invention.
FIG. 2 is a side view of a diagonal angle formed with a silicon oxide film in step S1. FIG.
3 is a view showing a side view of an etching solution in which fluorinated groups are formed on the silicon oxide film in step S2.
FIG. 4 is a side view of a plasma etching process in which a silicon oxide film and a fluorocarbon group are treated with a plasma of a fluorine compound gas to form a SiOxFy mask.
FIG. 5 shows the result of the etching in step S4.
FIG. 6 shows a process of plasma etching after placing a crucible in a Faraday cage.
7 is a conceptual diagram of a circulating etching process.
8A is an electron micrograph of a nanopillar formed by different conditions.
8B is an electron micrograph of the generated nanoparticles.

Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the specific embodiments shown and described because the present invention can be variously modified and can take various forms. It is to be understood that the invention is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, the term "comprises" or "having" is intended to designate the presence of stated features, elements, etc., and not one or more other features, It does not mean that there is none.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

FIG. 1 is a process diagram illustrating an exemplary method for producing a nanopillar according to the present invention, as one embodiment of the present invention. As shown in FIG. 1, the present invention includes a step S1 for forming a silicon oxide film, a step S2 for forming a fluorocarbon group, a step S3 for treating the fluorine compound gas, and an etching step S4.

FIG. 2 is a side view of a cruciform with a silicon oxide film formed thereon to exemplify a shape of a cruciform with a silicon oxide film formed in step S1; FIG.

Referring to FIG. 2, step S1 is a step of preparing a crucible 10 on which a silicon oxide film is formed. A silicon specimen was used for the crucible 10. A silicon oxide film 20 having a thickness of about 10 nm or less was formed on the silicon specimen in the form of a native oxide film. The natural oxide film is formed by oxygen in the air spontaneously reacting with the silicon surface, which is formed by exposing the silicon specimen to air at room temperature for one day or more. The silicon oxide film 20 may be formed by adding a SiO ₂ deposition process to the conventional oxide film as well as the native oxide film. Silicon oxide film 20 is SiO _2.

3 is a side view for illustrating the shape of the crucible 10 having the fluorocarbon group 30 formed on the silicon oxide film 20 in step S2.

Referring to FIG. 3, step S2 is a step of forming the fluorocarbon group 30 on the silicon oxide film 20. FIG. Plasma by C ₄ F ₈ carbon fluoride gas was used on the silicon oxide film 20 which is a natural oxide film. However, the fluorocarbon gas may be, for example, CF ₄ , C ₄ F ₈ , C ₄ F ₆ , CH ₂ F ₂ and CHF ₃ . And a gas such as O ₂ may be added to the fluorocarbon gas. When forming the fluorocarbon group 30, the plasma of the fluorocarbon gas was generated by applying a bias voltage not exceeding a threshold energy required for etching the crucible 10. At this time, the fluorocarbon groups 30 are randomly formed on the silicon oxide film 20. The time for exposing the silicon oxide film 20 to the plasma by the fluorocarbon gas can be variously adjusted to 5 to 30 seconds and the size of the fluorocarbon group 30 can be varied to control the diameter of the nano pillars.

The process conditions of step S2 are shown in Table 1 below.

Source power
(w) Bias voltage
(V) Pressure
(mTorr) Flow rate of fluorocarbon gas (sccm) Time
(s) 50 to 1000 0 5 to 50 5-100 5 to 30

FIG. 4 is a side view for illustrating a crucible 10 having a SiOxFy mask 40 formed by treating the silicon oxide film 20 and the fluorocarbon group 30 with a plasma of a fluorine compound gas in step S3.

4, to form a SiOxFy-based mask 40 in place fluorocarbon group 30 is formed on the etching gakmul 10. In step S3 using a plasma by the SF ₆ gas. More specifically, the SiOxFy-based mask 40 is formed by using the energy of the ions transferred to the silicon oxide film 20 and the F radical. In this process, the silicon oxide film 20 on the upper part of the crucible and not formed with the fluorocarbon group 30 was removed by reaction with the plasma.

As the fluorine compound gas, not only SF ₆ but also fluorine-containing CF ₄ , C ₄ F ₈ , C ₄ F ₆ , CH ₂ F _{2 and} CHF ₃ can be used. Can also be the Ar and / or O ₂ was added.

The process conditions in step S3 are shown in Table 2 below.

Source power
(w) Bias voltage
(V) Pressure
(mTorr)  Flow rate of fluorocarbon gas (sccm) Time
(s) 50 to 1000 0 to -500 5 to 50 5-100 5 ~ 60

FIG. 5 shows the result of the etching in step S4.

FIG. 6 shows a process of plasma etching the seed crystal 10 after positioning the seed crystal 10 in the Faraday cage 50.

7 is a conceptual diagram of a circulating etching process.

Referring to FIGS. 5 and 6, in step S4, the crucible 10 is placed inside the Faraday cage 50 and the crucible 10 is etched through a plasma process. In this case, a sample holder 52 is provided in the Faraday cage so that the angle formed by the open face 51 of the Faraday cage 50 and the plane of the angled corners can be adjusted. The inclination angle of the nano pillars can be adjusted by adjusting the angle of the sample holder 52 to 0 to 90 °, preferably 0 to 60 °, after positioning the crucible 10 on the sample holder 52. In the case of a vertically structured nanopillar, when the Faraday cage 50 is not used or when the Faraday cage 50 is used, etching can be performed by setting the angle of the sample holder 52 to 0 °.

Referring to FIG. 7, a circulation etching method in which deposition and etching are repeated is used to stabilize the inclined etching of the crucible 10. More specifically, the step of plasma-treating and etching the crucible 10 is followed by the step of depositing the protective film 60 by plasma treatment containing fluorocarbon gas on the etched wall surface. Thus, the step of depositing the protective film 60 and etching through the plasma treatment is repeatedly performed. This cyclic etching process was carried out 20 times. However, the number of the circulating etching processes proposed in the present invention is only an example, and the length of the nano pillars can be controlled by controlling the number of the circulating etching processes.

Table 3 below shows the conditions of the deposition process in the cyclic etching.

Source power
(w) Bias voltage
(V) Pressure
(mTorr) Flow rate of fluorocarbon gas (sccm) Time
(s) 50 to 1000 0 5 to 50 5-100 5 to 30

Table 4 below shows the etch conditions during the cyclic etching.

Source power
(w) Bias voltage
(V) Pressure
(mTorr)  Flow rate of fluorocarbon gas (sccm) Time
(s) 50 to 1000 0 to -500 5 to 50 5-100 5 ~ 60

8A and 8B are electron micrographs of nano pillars of various angles manufactured through the present invention. The process conditions of the nano pillars produced using the illustrated Faraday cage are as follows. Table 5 shows the process conditions in S2, Table 6 shows the process conditions in S3, Table 7 shows the deposition process conditions in the circulating etching, and Table 8 shows the etching process conditions in the circulating etching.

Source power
(w) Bias voltage
(V) Pressure
(mTorr) Flow rate of fluorocarbon gas (sccm) Time
(s) 400 0 30 30 15

Source power
(w) Bias voltage
(V) Pressure
(mTorr)  Flow rate of fluorocarbon gas (sccm) Time
(s) 400 -100 10 30 15

Source power
(w) Bias voltage
(V) Pressure
(mTorr) Flow rate of fluorocarbon gas (sccm) Time
(s) 400 0 30 30 15

Source power
(w) Bias voltage
(V) Pressure
(mTorr)  Flow rate of fluorocarbon gas (sccm) Time
(s) 400 -100 41 30) 20

인 나노기둥, 나노기둥의 각도는 60°, 길이는 4.2

인 나노기둥, 나노기둥의 각도는 50°, 길이는 3.6

인 나노기둥의 전자현미경 사진이다. 상기 나노기둥은 패러데이 케이지의 각도를 왼쪽부터 차례로 15°, 30°, 40°로 조절하여 제작한 것이다. 도 8a를 참조하면, 패러데이 케이지(50)의 각도를 조절하여 나노기둥의 각도를 조절하고 이를 통해 나노기둥을 제작할 수 있었음을 확인할 수 있다. Referring to FIG. 8A, the angles of the nano pillars are 75 degrees and the length is 3.2

The angle of the nano-pillar and nano-pillar is 60 ° and the length is 4.2

The angle of the nano-pillar, the nano-pillar is 50 °, and the length is 3.6

It is an electron micrograph of the inner nano pillars. The nano pillars are manufactured by adjusting the angle of the Faraday cage from 15 属, 30 属, and 40 属 in order from the left. Referring to FIG. 8A, it can be seen that the angle of the nano pillar was adjusted by adjusting the angle of the Faraday cage 50, and the nano pillar was formed through the adjustment of the angle.

FIG. 8B is a photograph showing a plurality of nanopillar pillars produced in a single crucible 10. FIG. From the left, the diameter of the nanopillar is 48 nm, 40 nm, and 36 nm. Referring to FIG. 8B, it can be seen that the sizes of the group of fluorocarbon 30 formed on one crucible 10 are different from each other, and the diameters of the nano pillars are different from each other.

Claims (13)

Preparing a crucible having a silicon oxide film formed thereon;
Forming a fluorocarbon group on the silicon oxide film;
Treating the silicon oxide film and the fluorocarbon group with a plasma by a fluorine compound gas; And
Comprising the steps of: (a)
How to make nanopillar pillars. The method according to claim 1,
The fluorocarbon group is formed from a plasma of fluorocarbon gas,
Wherein the plasma of the fluorocarbon gas is generated by applying a bias voltage not exceeding a threshold energy required for etching the projected product.
How to make nanopillar pillars. 3. The method of claim 2,
Wherein the fluorocarbon gas comprises at least one selected from the group consisting of CF ₄ , C ₄ F ₈ , C ₄ F _6, CH ₂ F ₂ and CHF ₃ .
How to make nanopillar pillars. The method according to claim 1,
Wherein the pre-crucible is a silicon specimen,
How to make nanopillar pillars. 5. The method of claim 4,
Wherein the silicon oxide film is a silicon oxide film,
How to make nanopillar pillars. The method according to claim 1,
Wherein the plasma of the fluorine compound gas, the silicon oxide film, and the fluorocarbon group react with each other by the plasma treatment with the fluorine compound gas to form a SiOxFy-based mask.
How to make nanopillar pillars. The method according to claim 1,
Wherein the fluorine compound gas comprises at least one selected from the group consisting of SF ₆ , CF ₄ , C ₄ F ₈ , C ₄ F ₆ , CH ₂ F ₂ and CHF ₃ .
How to make nanopillar pillars. 8. The method of claim 7,
Characterized in that the fluorine compound gas comprises O ₂ or Ar gas.
How to make nanopillar pillars. 3. The method of claim 2,
Wherein a diameter of the nanopillar is controlled by adjusting a plasma treatment time by the fluorocarbon gas.
How to make nanopillar pillars. The method according to claim 1,
Characterized in that the crucible is located in a Faraday cage.
How to make nanopillar pillars. 11. The method of claim 10,
Wherein an angle formed by the open face of the Faraday cage and the face of the wedge angle is adjusted so that the wedge angle is inclinedly etched.
How to make nanopillar pillars. The method according to claim 1,
Further comprising depositing a protective film on the etched wall surface by plasma treatment containing carbon fluoride gas,
How to make nanopillar pillars. 13. The method of claim 12,
Wherein the step of plasma etching and etching the seed crystal and the step of depositing a protective film by plasma treatment containing fluorocarbon gas on the etching wall are repeated two or more times in order.
How to make nanopillar pillars.

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