KR20160059760A

KR20160059760A - Carbon nanotube emitter for X-ray source and method of fabricating the same

Info

Publication number: KR20160059760A
Application number: KR1020140161696A
Authority: KR
Inventors: 염경태; 임병직
Original assignee: 주식회사바텍; (주)바텍이우홀딩스
Priority date: 2014-11-19
Filing date: 2014-11-19
Publication date: 2016-05-27

Abstract

The present invention provides a method of manufacturing a carbon nano tube (CNT) emitter comprising the steps of: pressing a stamp mold on a resist layer on a substrate to transfer an uneven pattern of the stamp mold onto the resist layer; forming a resist pattern by etching the resist layer on which the uneven pattern is transferred; forming a catalyst layer on the substrate on which the resist pattern is formed; forming a catalyst pattern by removing the resist pattern and the catalyst layer arranged thereon; and growing a CNT on the catalyst pattern in CNT synthesizing equipment. According to the present invention, the manufacturing efficiency of a CNT emitter can be improved by manufacturing the CNT emitter using a direct growth method.

Description

Technical Field [0001] The present invention relates to a carbon nanotube emitter for X-ray source,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon nano tube (CNT) emitter for an X-ray source, and more particularly, to a CNT emitter using a direct growth method and a manufacturing method thereof .

X-ray source performance plays a decisive role in industrial non-destructive imaging and medical radiographic imaging in order to obtain images with good contrast and resolution.

In the prior art, a thermionic emitter that emits electrons at a high temperature using a filament was used as an electron source of an X-ray source, that is, an electron emitter. However, since the thermoelectromotive emitter has to be raised to a temperature higher than 1000 degrees for electron emission, the power consumption is relatively large and the emitter can not be turned on and off instantly.

In order to improve this, a field emitter type emitter which emits electrons by using quantum mechanical tunneling by an electric field is widely used.

Recently, in order to miniaturize the X-ray source, nanometer-sized materials other than the conventional metal or semiconductor materials are used as field emission emitters. In particular, carbon nanotubes (CNTs) are used as emitters Research is actively underway.

Generally, the CNT emitter is manufactured by a paste method or a direct growth method. In the face method, CNT powder formed through an arc discharge method or the like is dispersed in a solvent to form a CNT paste, which is applied to a substrate and then patterned. However, the CNT emitter formed by the paste method has a problem that the uniformity of the CNT length is poor and the field emission is not uniform.

On the other hand, the direct growth method is a method of directly growing CNT on a substrate. As compared with the paste method, the uniformity of the CNT length is high and the field emission is uniform and stable.

However, in the conventional direct growth method, a photolithography process is indispensable in manufacturing a CNT to a desired size. As a result, a complex photolithography production facility and manufacturing process are required, which causes problems such as an increase in manufacturing cost.

In addition, the conventional direct growth method has a disadvantage in that the CNT density is low, the current density and the field emission characteristic of the CNT emitter are low, and the lifetime is short.

Disclosure of the Invention Problems to be Solved by the Invention The present invention has a problem to provide a method for increasing manufacturing efficiency in manufacturing a CNT emitter by a direct growth method.

Another problem is to provide a way to improve the current density and field emission characteristics of the CNT emitters.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of: pressing a stamp mold onto a resist layer on a substrate to transfer an uneven pattern of the stamp mold to the resist layer; Etching the resist layer to which the concave-convex pattern is transferred to form a resist pattern; Forming a catalyst layer on the substrate on which the resist pattern is formed; Removing the resist pattern and the catalyst layer thereon to form a catalyst pattern; In the CNT synthesis equipment, there is provided a CNT emitter manufacturing method comprising growing CNTs on the catalyst pattern.

Here, before the step of growing the CNTs, an annealing process may be performed on the catalyst pattern.

The annealing process may be performed by injecting carrier gas and hydrogen gas in the CNT synthesis equipment.

The annealing process may proceed for at least 3 minutes but less than 10 minutes.

And curing the resist layer formed with the concave-convex pattern using UV or heat.

And forming a buffer layer made of an oxidized material on the substrate before forming the resist layer.

The catalyst layer may be made of a transition metal.

In another aspect, the present invention provides a semiconductor device comprising: a substrate; A catalyst metal layer formed on the substrate; And a CNT emitter including CNTs formed on the catalytic metal layer.

Here, the buffer layer may further include an oxide film buffer layer interposed between the substrate and the catalyst metal layer.

According to the present invention, a catalyst pattern for CNT growth is formed using an imprint method. Accordingly, the manufacturing facility and the manufacturing process can be simplified and the manufacturing cost can be reduced as compared with the case of using the conventional photolithography method.

In addition, an annealing process is performed on the catalyst pattern to form a catalyst seed having a uniform size and a dense density, followed by growing the CNT. Accordingly, CNTs can be formed to have high density and vertical alignment, so that current density and field emission characteristics of CNT emitters can be improved and lifetime can be increased.

FIGS. 1A to 1F are cross-sectional views schematically showing a method of manufacturing a CNT emitter according to an embodiment of the present invention.
2 is a photograph showing a CNT growth test result according to an annealing time.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In the embodiment of the present invention, an easier imprint method is applied instead of the photolithography method in forming the CNTs by the direct growth method. This will be described in more detail below with reference to Fig.

1A to 1F are cross-sectional views schematically showing a method of manufacturing a CNT emitter according to an embodiment of the present invention.

First, referring to FIG. 1A, a buffer layer 20 is formed on a substrate 11, and a resist layer 30 is formed on a buffer layer 20.

As the buffer layer 20, for example, SiO2 may be used as the oxide film, but the present invention is not limited thereto.

The resist layer 30 may be made of an organic material such as resin. It is preferable that the resist layer 30 is configured to have a property of being cured by heat or ultraviolet rays (UV). In the embodiment of the present invention, a resist layer 30 having properties to be cured by UV is exemplified.

Next, referring to FIG. 1B, the imprint process for the substrate 11 is performed using the stamp mold 100.

The stamp mold 100 has the same structure as the mask of the photolithography process and has a concavo-convex pattern formed of a relief pattern 101a and a relief pattern 101b on the lower surface to be pressed onto the substrate 11. [

Here, the relief pattern 101a is arranged on the substrate 11 in correspondence with a portion for forming a desired CNT pattern.

When the stamp mold 100 constructed as described above is pressed onto the substrate 11, the concavity and convexity pattern of the stamp mold 100 is transferred to the resist layer 30.

Thus, the resist layer 30 is provided with a concave-convex pattern corresponding to the stamp mold 100. That is, the resist layer 30 is provided with a recessed pattern 31a recessed in the direction of the substrate 11 in correspondence to the embossed pattern 101a and a protrusion 31a projecting in the direction opposite to the substrate 11 in correspondence with the recessed pattern 101b A pattern 31b is formed.

Next, the resist layer 30 of the transferred concave-convex pattern is subjected to the curing process. In this regard, the resist layer 30 can be cured by, for example, UV irradiation.

On the other hand, as another example, when the resist layer 30 having thermal curing properties is used, the resist mold layer 30 is hardened by applying hot heat while pressing the stamp mold 100 onto the substrate 11 .

Next, referring to FIG. 1C, after the stamp mold 100 is removed, the dry etching process is performed to remove the thin recessed pattern 31a. As a dry etching process, a reactive ion etching (RIE) process can be used.

Thus, the concave pattern 31a is removed on the substrate 11, and the convex pattern 31b is left. Here, for convenience of explanation, the protruding pattern 31b is referred to as a resist pattern 32, and a portion where the recessed pattern 31a is removed as a space between the protruding patterns 31b is referred to as a resist hole 33. [

Next, referring to FIG. 1D, a catalyst metal is deposited on the substrate 11 on which the resist pattern 32 is formed to form the catalyst layer 40.

The catalyst layer 40 is formed on the upper surface of the resistor pattern 32 and in the resist hole 33, that is, on the upper surface of the buffer layer 20 under the resist hole 33.

As the catalytic metal, a transition metal may be used. For example, it is preferable to use iron (Fe), cobalt (Co), and nickel (Ni), but the present invention is not limited thereto.

Next, referring to FIG. 1E, the resist pattern 32 is stripped and removed.

Thus, the catalyst layer 40 located above the resist pattern 32 is also removed together. That is, the resist pattern 32 and the upper catalyst layer 40 are removed together by performing a lift-off process.

As a result, the catalyst layer 40 located in the resist hole 33 remains on the substrate 11. For the sake of convenience of explanation, the catalyst layer 40 thus left is referred to as a catalyst pattern 41.

That is, the catalyst pattern 41 is formed in correspondence with the relief pattern 101a of the stamp mold 100.

Referring to FIG. 1F, the CNT 51 is grown on the catalyst pattern 41, and thus the emitter 50 composed of the CNTs 51 can be fabricated.

In this regard, a substrate 11 on which a catalyst pattern 41 is formed is placed in a CNT synthesizing apparatus (not shown), and a source gas, for example, carbonization gas for CNT synthesis is introduced. At this time, the synthesis of CNT can proceed by increasing the temperature to about 680 to 780 as the synthesis temperature.

Thus, the CNTs 51 are synthesized and grown on the catalyst pattern 41.

Meanwhile, in the embodiment of the present invention, the annealing process for the catalyst may be performed before the CNT synthesis process.

The annealing process corresponds to a process for catalyst seed crystallization. In this regard, for example, after the substrate 11 on which the catalyst pattern 41 is formed is put into the CNT synthesizing equipment, a carrier gas and hydrogen gas are injected into the synthesis equipment and annealing is performed for about 5 minutes .

As a result, the size of the catalyst seed in the catalyst pattern 41 can be uniformly formed as a whole.

In this connection, FIG. 2 can be referred to, and FIG. 2 is a photograph showing a CNT growth test result according to an annealing time.

In Fig. 2, the case where the annealing time (Tanneal) is 0 minute, 5 minutes, 10 minutes, and 20 minutes is shown from left to right.

The catalyst seeds formed according to the respective annealing times (Tanneal) are shown at the top and center in the drawing, and the CNTs grown on the catalyst seeds formed according to the respective annealing times (Tanneal) are shown in the lower part of the figure.

Referring to FIG. 2, it can be seen that when the annealing is applied for about 5 minutes, the catalyst seed is formed with the most dense density and uniform size. As a result, it can be confirmed that CNTs grown in the catalyst seeds annealed for about 5 minutes grow most vertically aligned with the highest density.

That is, since the catalyst seeds are formed with a uniform size and a dense density, the CNTs can grow densely in the vertical direction due to the pushing force between them during CNT growth.

In comparison, in the case where the annealing process is not performed and the relatively long time annealing is applied, the uniformity and the density of the catalyst seed are relatively lowered, and the vertical alignment and density of the CNT are lowered.

As described above, according to the present embodiment, the density and vertical alignment characteristics of CNTs can be improved by densely and uniformly forming the catalyst seeds by annealing the catalyst pattern for about 5 minutes, preferably for 3 minutes or more and less than 10 minutes . This has the advantage that the current density and the field emission characteristics of the CNT emitter can be improved and the lifetime thereof can be increased.

By arranging the CNT emitter fabricated as described above on the cathode for the X-ray source and combining it with other structures including the anode and the gate electrode, it is possible to manufacture an X-ray source using a CNT emitter do.

Meanwhile, the CNT emitters manufactured as described above can be applied to other field emission devices such as a field emission display (FED) in addition to an X-ray source.

As described above, according to the embodiment of the present invention, the imprint method is used to form a catalyst pattern for CNT growth. Accordingly, the manufacturing facility and the manufacturing process can be simplified and the manufacturing cost can be reduced as compared with the case of using the conventional photolithography method.

The embodiment of the present invention described above is an example of the present invention, and variations are possible within the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and equivalents thereof.

11: substrate 20: buffer layer
30: resist layer 31a: lapping pattern
31b: protruding pattern 32: resist pattern
33: resist hole 40: catalyst layer
41: Catalyst pattern 50: Emitter
51: CNT 100: stamp mold
101a: Embossed pattern 101b: Embossed pattern

Claims

Pressing a stamp mold onto a resist layer on the substrate to transfer the concavo-convex pattern of the stamp mold to the resist layer;
Etching the resist layer to which the concave-convex pattern is transferred to form a resist pattern;
Forming a catalyst layer on the substrate on which the resist pattern is formed;
Removing the resist pattern and the catalyst layer thereon to form a catalyst pattern;
In CNT (carbon nano tube) synthesis equipment, growing CNT on the catalyst pattern
Gt; CNT < / RTI >

The method according to claim 1,
Before the step of growing the CNT, an annealing process is performed on the catalyst pattern
Gt; CNT < / RTI >

3. The method of claim 2,
The annealing process is performed by injecting carrier gas and hydrogen gas in the CNT synthesis equipment
CNT emitter manufacturing method.

The method of claim 3,
Wherein the annealing process is performed for 3 minutes or more and less than 10 minutes.

The method according to claim 1,
Curing the resist layer formed with the concavo-convex pattern using UV or heat
Gt; CNT < / RTI >

The method according to claim 1,
Forming a buffer layer made of an oxidized material on the substrate before forming the resist layer
Gt; CNT < / RTI >

The method according to claim 1,
Wherein the catalyst layer is made of a transition metal.

Claims [1]
A catalyst metal layer formed on the substrate;
The CNTs formed on the catalyst metal layer
Gt; CNT < / RTI >

9. The method of claim 8,
And an oxide film buffer layer interposed between the substrate and the catalyst metal layer.