KR20100072468A - Carbon nano tube using dlc and method for growing thereof - Google Patents

Abstract

PURPOSE: Carbon nanotubes using DLC and a method for growing the same are provided to minimize the amount of foreign materials remaining on a wafer by growing the carbon nanutubes using a DLC thin film instead of catalyst metal and to reduce a manufacturing process of the carbon nanotubes. CONSTITUTION: A method for growing carbon nanotubes using DLC uses a plasma enhanced chemical vapor deposition(PECVD) method. The method comprises: a step of forming a DLC thin film on a wafer which is put into a process chamber; a step(S31) of forming a plurality of DLC nuclei on the wafer by dividing the DLC thin film; and a step(S35) of growing the carbon nanotubes by growing the DLC nuclei into seeds.

Description

Carbon nano tube using DLC and method for growing etc}

The present invention relates to a carbon nanotube (CNT) and a growth method thereof, and more particularly to carbon nanotubes and growth thereof using DLC grown using a diamond-like carbon (DLC) thin film instead of a catalyst metal. It is about a method.

Carbon nanotubes are very small regions of nanometer diameter, and are carbon allotrope composed of a large amount of carbon on earth. Carbon nanotubes refer to a material in which one carbon is combined with another carbon atom in a hexagonal honeycomb pattern to form a tube. Such carbon nanotubes have excellent mechanical properties, electrical selectivity, excellent field emission characteristics, high efficiency hydrogen storage medium characteristics, and are known to be perfect materials with few defects among existing materials.

Such carbon nanotubes are manufactured by a high growth technology, and the growth methods include arc-discharge, laser vaporization, plasma enhanced chemical vapor deposition (PECVD), and thermochemistry. Thermal Chemical Vapor Deposition, Vapor Phase Growth, Electrolysis and Flame Synthesis.

In particular, when growing carbon nanotubes by PECVD, C ₂ H ₂ , CH ₄ , C ₂ H ₄ , C ₂ H ₆ , CO gas is used as the reactor, Ni, Pt and the like are used as the catalyst metal. As a power source for causing plasma discharge, either a direct current or a high frequency power source is used.

In the case of growing carbon nanotubes by PECVD, not only pure carbon nanotubes exist on the wafer, but also other carbon materials such as amorphous and crystalline or catalytic metals such as metal particles. Together, they adversely affect accurate characterization and application. Therefore, after the carbon nanotubes are grown, a purification process is performed.

As a purification method, centrifugation is performed by ultrasonically-assisted microfiltration, filtration, chromatography, and sonication, or oxidation using nitric acid is used. The process of reacting the metal compound with the mixture to reduce the reacted mixture to insert the metal compound into graphite and converting it into a metal element is heat treated and oxidized with H ₂ gas at 150 to 600 ° C. , Metal is converted into metal oxide. Soak it in a solution such as hydrochloric acid or nitric acid and boil it for 6 hours to dissolve the metal.

However, in the process of dissolving the metal in a solution such as hydrochloric acid or nitric acid in the purification process, carbon nanotubes are also dissolved together, there is a problem that does not efficiently remove the catalytic metal.

As such, when the catalyst metal is used to grow the carbon nanotubes, a purification process is required, and thus the manufacturing time of the carbon nanotubes is long and the manufacturing cost is increased.

Therefore, the present invention is to solve such a conventional problem, the carbon nanotubes are damaged due to the purification process proceeds to the subsequent process due to the use of the catalyst metal, the manufacturing process time of the carbon nanotubes are long, An object of the present invention is to provide a carbon nanotube and a growth method using DLC that can solve the problem of rising cost.

Another object of the present invention is to provide a carbon nanotube and a method for growing the same using DLC capable of growing carbon nanotubes without a catalytic metal.

In order to achieve the above object, the present invention is a carbon nanotube growth method using a plasma chemical vapor deposition method, DLC thin film forming step of forming a DLC thin film on the wafer injected into the process chamber, and the DLC thin film is divided into a plurality of on the wafer It provides a carbon nanotube growth method using a DLC comprising a nucleation step of forming a DLC nucleus of the, and a growth step of growing carbon nanotubes with the DLC nucleus (seed).

In the method of growing carbon nanotubes according to the present invention, the DLC thin film forming step includes an ultrasonic cleaning of the wafer using isopropyl alcohol or acetone, followed by a washing step of spraying N ₂ gas to dry the wafer, and a predetermined amount in the process chamber. A first pretreatment step of pretreating the wafer by injecting Ar gas and a deposition step of depositing a DLC thin film on the upper surface of the wafer by injecting a predetermined amount of H ₂ gas and C ₂ H ₂ gas into the process chamber; It is configured by.

In the carbon nanotube growth method according to the present invention, in the first pretreatment step, 30 sccm Ar gas is injected at 5.5 × 10 ⁻² torr and 70 ° C., and a plasma is formed by applying a bias of −800 V to pretreat the wafer.

In the carbon nanotube growth method according to the present invention, the deposition step is 30 sccm injection of H ₂ gas and C ₂ H ₂ gas at 1.4 × 10 ^-1 torr and 70 ℃, respectively, by applying a bias of -600V to -800V A DLC thin film is deposited on the top surface of the wafer.

In the carbon nanotube growth method according to the present invention, in the nucleation step, a predetermined amount of NH ₃ gas is injected into the process chamber to divide the DLC thin film to form an aggregated DLC nucleus on the upper surface of the wafer. And a second pretreatment step of forming and annealing step of injecting a predetermined amount of H ₂ gas into the process chamber to anneal the DLC nuclei in the aggregated state.

In the carbon nanotube growth method according to the present invention, the second pretreatment step is pretreated by applying 70 sccm of NH ₃ gas at 2.0 × 10 ⁻¹ torr and 540 ° C., respectively, and applying a bias of −600 V.

In the carbon nanotube growth method according to the present invention, the annealing step is annealed by injecting 70 sccm of H ₂ gas at 1.3 torr and 580 ° C., respectively.

In the carbon nanotube growth method according to the present invention, the growth step injects a predetermined amount of NH ₃ gas and C ₂ H ₂ gas into the process chamber to grow the carbon nanotubes based on the DLC nucleus.

In the carbon nanotube growth method according to the present invention, the growth step is injecting 40 sccm of NH ₃ gas 60sccm and C ₂ H ₂ gas at 1.3 torr and 500 to 700 ℃, and by applying a bias of -500 to -700V Carbon nanotubes are grown on the basis of DLC nuclei.

In the carbon nanotube growth method according to the present invention, the carbon nanotubes formed in the growth step are grown in a multiwall.

The present invention also provides carbon nanotubes grown by the carbon nanotube growth method using the aforementioned DLC.

According to the present invention, since carbon nanotubes are grown using DLC thin films instead of catalytic metals, foreign matters other than carbon nanotubes can be minimized on the wafer. In addition, since the DLC thin film, which is a kind of carbonitride, is used instead of the catalyst metal as in the related art, the purification process can be improved, and thus the manufacturing process time and manufacturing cost of carbon nanotubes can be reduced.

The carbon nanotubes grown on the basis of the DLC thin film, as shown in Figs. 10 (c) and 10 (d), have a stable bonding structure and have good surface conditions. In other words, carbon nanotubes grown on the basis of DLC thin films have superior characteristics as carbon nanotubes grown on the basis of catalytic metals.

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

Here, DLC (Diamond-Like Carbon) is a kind of carbon compound, and as its name suggests, it is made of carbon and has properties similar to diamond. DLC, like diamond, is a material that has strength, wear resistance, and chemical safety. DLC also has a very low coefficient of friction because it has the same softness as graphite. DLC is an amorphous material mixed with sp1, sp2 and sp3 bonds.

1 is a flowchart illustrating a carbon nanotube growth method using DLC according to an embodiment of the present invention. 2 to 6 are cross-sectional views illustrating each step according to the growth method of FIG. 1.

In the carbon nanotube growth method using DLC according to an embodiment of the present invention, as shown in FIGS. 1 to 6, preparing a wafer 41 (S10), a DLC thin film 43 on the wafer 41 is provided. Forming a step (S20), dividing the DLC thin film 43 into a DLC nucleus 45, and growing the carbon nanotubes 47 with the split DLC nucleus 45 (seed) (S30) Each step is performed sequentially. At this time, carbon nanotube growth according to the present embodiment is performed in a plasma chemical vapor deposition apparatus. The plasma chemical vapor deposition apparatus used in this embodiment has disclosed an example of using a direct current (DC) as the power source.

First, as shown in FIG. 2, a wafer 41, which is a specimen for growing carbon nanotubes, is prepared (S10). Although a p-type silicon wafer was used as the wafer 41, the present invention is not limited thereto. The prepared wafer 41 is thrown into the process chamber of the plasma chemical vapor deposition apparatus.

Next, as shown in FIG. 3, the step of forming the DLC thin film 43 on the wafer 41 is performed (S20). DLC thin film forming step (S20) includes an ultrasonic cleaning and drying step (S21), Ar pre-treatment step (S23) and DLC thin film deposition step (S25), each step is performed sequentially.

The ultrasonic cleaning and drying step S21 is a step performed to remove foreign matter remaining on the wafer 41. That is, in the ultrasonic cleaning and drying step (S21), the wafer 41 is ultrasonically cleaned using isopropyl alcohol (IPA) or acetone for about 5 minutes, and then sprayed with N ₂ gas to dry.

Next, a predetermined amount of Ar gas is injected into the process chamber to perform an Ar pretreatment step S23 of pretreatment of the wafer 41. That is, under process conditions of 5.5 × 10 ⁻² torr and 70 ° C., 30 sccm Ar gas is injected into the process chamber, and a plasma is formed by applying a bias of −800 V to pretreat the upper surface of the wafer 41. The reason for performing the Ar pretreatment step S23 is to improve the surface adhesion of the DLC thin film 43 to the upper surface of the wafer 41.

In addition, a predetermined amount of H ₂ gas and C ₂ H ₂ gas are injected into the process chamber to deposit the DLC thin film 43 on the upper surface of the wafer 41 (S25). That is, under process conditions of 1.4 × 10 ⁻¹ torr and 70 ° C., 30 sccm of H ₂ gas and C ₂ H ₂ gas are injected into the process chamber, respectively, and a bias of -600 V to -800 V is applied to the upper surface of the wafer 41. DLC thin film 43 may be deposited.

For example, in the present embodiment, steps S23 and S25 were performed under the conditions shown in Table 1 below. That is, a plurality of wafers 41 were prepared and the first group of wafers were deposited with DLC thin films for 2 minutes. The second group of wafers deposited the DLC thin film for 4 minutes. The third group of wafers deposited the DLC thin film for 8 minutes. The fourth group of wafers were then deposited with a DLC thin film for 16 minutes.

Pre-treatment Deposition Pressure 5.5 × 10 ^-2 torr 1.4 × 10 ^-1 torr Gas Ar: 30 sccm H ₂ : 30 sccm
C ₂ H ₂ : 30 sccm Bias -800 V -600 V, -700 V, -800 V Temp. 70 ℃ 70 ℃ Time 10min 2min, 4min, 8min, 16min

Next, as shown in FIGS. 4 to 6, the growth of the carbon nanotubes 47 using the DLC thin film 43 is performed. Growing the carbon nanotubes 47 (S40) is a step of forming a DLC nucleus 45 by NH ₃ pretreatment (S31), annealing the DLC nucleus 45 (S33) and DLC nucleus 45 Growing carbon nanotubes 47 based on the step (S35), each step is performed sequentially.

After depositing the DLC thin film 43 in step S25, in order to divide the DLC thin film 43 into the DLC nucleus 45, as shown in FIG. 4, a predetermined amount of NH ₃ gas is first injected into the process chamber. In step S31, the DLC thin film 45 is divided to form the DLC nucleus 45 in the aggregation state on the upper surface of the wafer 41. That is, in step S31, 70 sccm of NH ₃ gas is injected into the process chamber at 2.0 × 10 ⁻¹ torr and 540 ° C., and the DLC thin film 43 is etched by applying a bias of −600 V to the plurality of DLC nuclei 45. Divide by)

Subsequently, as shown in FIG. 5, a predetermined amount of H ₂ gas is injected into the process chamber at step S33 to anneal the DLC nucleus 45 in the aggregated state. That is, the process is performed to stabilize the DLC nucleus 45 in the aggregated state hit in step S31. In the process conditions of 1.3 torr and 580 ° C., 70 sccm of H ₂ gas is injected to inject the DLC nucleus 45 approximately. Anneal for 10 minutes.

As shown in FIG. 6, a predetermined amount of NH ₃ gas and C ₂ H ₂ gas are injected into the process chamber in operation S35 to grow carbon nanotubes 47 based on the respective DLC nuclei (45 in FIG. 5). Let's do it. That is, under process conditions of 1.3 torr and 500 to 700 ° C., 40 sccm of NH ₃ gas and 60 sccm of C ₂ H ₂ gas are injected into the process chamber, and a bias of −500 to −700 V is applied to the DLC nucleus (45 in FIG. 5). The carbon nanotubes 47 are grown on the basis of 5 minutes to 20 minutes.

The reason why the carbon nanotubes 47 are grown at 500 to 700 ° C. is to grow the carbon nanotubes 47 having a stable bonding structure. Specific reasons will be described in the description with reference to FIG. 10.

For example, in the present embodiment, steps S31 and S35 were performed under the conditions shown in Table 2 below. That is, NH ₃ pretreatment was performed on the first to fourth groups of wafers 41 for 3 minutes, 4 minutes, 5 minutes, and 7 minutes. The carbon nanotubes 47 were grown with different growth times and biases for the wafers 41 of the first to fourth groups.

Pre-treatment Annealing Growth Pressure 2.0 × 10 ^-1 torr 1.3 torr 1.3 torr Gas NH ₃ : 70 sccm H ₂ : 70 sccm NH ₃ : 60 sccm
C ₂ H ₂ : 40 sccm Bias -600 V - -500 to -700 V Temp. 540 ℃ 580 ℃ 500 ~ 700 ℃ Time 3 to 7 min 10min 5 to 20min

As described above, the carbon nanotube growth method using the DLC according to the present embodiment may grow the carbon nanotubes 47 without the catalytic metal. In particular, since the carbon nanotubes 47 are grown using the DLC thin film 43 instead of the catalytic metal, foreign matters other than the carbon nanotubes 47 on the wafer 41 may be minimized. In addition, since the DLC thin film 43, which is a kind of carbohydrate, is used instead of the catalyst metal as in the related art, the purification process can be improved, and thus the manufacturing process time and manufacturing cost of the carbon nanotubes 47 can be reduced.

Looking at the characteristics of the carbon nanotubes grown by the growth method according to the present embodiment as follows.

First, as shown in FIG. 7, the diameter of the carbon nanotubes increases as the NH ₃ pretreatment time increases. That is, as the NH ₃ pretreatment time increases, the size of the DLC nuclei split and aggregated in the DLC thin film increases, and thus, the diameter of the carbon nanotubes grown based on the DLC nuclei increases.

Specifically, referring to the SEM (Scanning Electron Microscope) image of the carbon nanotubes of FIG. 8, the carbon nanotubes pretreated with NH ₃ for 3 minutes have a diameter of 15 nm, and the carbon nanotubes pretreated with NH ₃ for 4 minutes have a diameter of 20 nm. The carbon nanotubes having a diameter and NH ₃ pretreated for 5 minutes have a diameter of 25 nm, and the NH ₃ pretreated carbon nanotubes for 7 minutes have a diameter of 30 nm. As such, the carbon nanotubes grow to a diameter of about 5 nm / min according to the NH ₃ pretreatment time, and the diameter of the carbon nanotubes increases in proportion to the NH ₃ pretreatment time.

In addition, looking at the transmission electron microscope (TEM) image of the carbon nanotubes grown using DLC according to the present embodiment, as shown in FIG. 9, the carbon nanotubes were grown in a multiwall without a certain direction. Can be.

FIG. 10 is a Raman spectrum of a DLC thin film according to temperature change. FIG. Through analysis of the Raman spectrum of the DLC thin film according to the temperature change it can be seen that the bonding structure of the carbon nanotubes according to this embodiment is quite stable.

In this embodiment, Raman spectrum was used as a method for analyzing the crystal structure of the DLC thin film or the structure of carbon nanotubes. The Raman method is simpler than the TEM method and can be analyzed in a short time, which is very useful for analyzing surface conditions. In this embodiment, the surface crystal state of the DLC thin film was analyzed using Raman analysis, and then the structure of carbon nanotubes was analyzed.

Generally, Raman peak is generated around 1560 cm ^-1 due to the characteristics of DLC thin film. In addition, the DLC changes the characteristics of the thin film close to graphite due to high temperature instability above 500 ° C. In this embodiment, the carbon nanotubes are grown by using a DLC thin film in a high temperature process using the characteristics of the DLC, the characteristics of the DLC thin film in the low temperature state and the high temperature state of Figure 4 (a) to Figure 4 (d From the Raman spectra).

Raman spectra of DLC thin films grown at 300 ° C. and 400 ° C., as shown in FIGS. 4 (a) and 4 (b), generally showed only G-line in the same manner as diamond peaks.

On the other hand, the Raman spectrum of the DLC thin film subjected to a high temperature process of 500 ° C. or higher has a G-line peak of 1577.0 cm ^−1, which shows a typical graphite structure, as shown in FIGS. 4 (c) and 4 (d). It can be seen clearly that the D-line with carbonaceous particles or defects is apparent at the peak of 1361.6 cm ^-1 . In particular, the peak intensity shows that the peak of the G-line is significantly higher than that of the D-line, and thus, the carbon nanotubes grown on the DLC thin film have a stable bonding structure and have very few surface defects. As a result, it can be seen that the carbon nanotubes grown without the catalytic metal have a fairly stable bonding structure. This is also why carbon nanotubes are grown at 500 to 700 ° C.

On the other hand, the embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples to aid understanding, and are not intended to limit the scope of the present invention. In addition to the embodiments disclosed herein, it is apparent to those skilled in the art that other modifications based on the technical idea of the present invention may be implemented.

1 is a flowchart illustrating a carbon nanotube growth method using DLC according to an embodiment of the present invention.

2 to 6 are cross-sectional views illustrating each step according to the growth method of FIG. 1.

7 is a graph showing a change in diameter of carbon nanotubes with NH3 pretreatment time.

8 is a SEM image of the surface of carbon nanotubes grown for 20 minutes with different NH3 pretreatment times.

9 is a TEM image of carbon nanotubes grown by the growth method of FIG. 1.

10 is a Lehman spectrum of a DLC thin film with temperature change.

Description of the Related Art [0002]

41: wafer

43: DLC Thin Film

45: DLC Nucleus

47: carbon nanotube

Claims (11)

Carbon nanotube growth method using plasma chemical vapor deposition, Forming a DLC thin film on a wafer placed in a process chamber; A nucleation step of dividing the DLC thin film to form a plurality of DLC nuclei on the wafer; And growing the carbon nanotubes by seeding the DLC nuclei. The method of claim 1, wherein the forming of the DLC thin film, Washing the wafer by ultrasonic cleaning with isopropyl alcohol or acetone and then spraying with N ₂ gas to dry the wafer; A first pretreatment step of pretreating the wafer by injecting a predetermined amount of Ar gas into the process chamber; Depositing a DLC thin film on the upper surface of the wafer by injecting a predetermined amount of H ₂ gas and C ₂ H ₂ gas into the process chamber; and growing the carbon nanotubes using DLC. The method of claim 2, wherein the first pretreatment step, A method of growing carbon nanotubes using DLC, in which 30 sccm Ar gas is injected at 5.5 × 10 ⁻² torr and 70 ° C., and a plasma is formed by applying a bias of −800 V. The method of claim 3, wherein the depositing step, DLC thin film is deposited on the upper surface of the wafer by injecting 30 sccm of H ₂ gas and C ₂ H ₂ gas at 1.4 × 10 ^-1 torr and 70 ° C., respectively, and applying a bias of -600V to -800V. Carbon nanotube growth method using. The method of claim 4, wherein the nucleation step, A second pretreatment step of injecting a predetermined amount of NH ₃ gas into the process chamber to divide the DLC thin film to form an aggregated DLC nucleus on the upper surface of the wafer; Annealing step of annealing the DLC nucleus in the aggregated state by injecting a predetermined amount of H ₂ gas into the process chamber. The method of claim 5, wherein the second pretreatment step, A method of growing carbon nanotubes using DLC, characterized in that 70 sccm of NH ₃ gas is injected at 2.0 × 10 ⁻¹ torr and 540 ° C., respectively, and pretreated by applying a bias of -600V. The method of claim 6, wherein the annealing step, Carbon nanotube growth method using a DLC, characterized in that annealing by injecting 70 sccm H ₂ gas at 1.3 torr and 580 ℃. The method of claim 7, wherein the growth step, Injecting a predetermined amount of NH ₃ gas and C ₂ H ₂ gas into the process chamber to grow carbon nanotubes based on the DLC nucleus. The method of claim 8, wherein the growth step, DLC characterized in that the carbon nanotubes are grown based on the DLC nucleus by injecting 40 sccm of NH ₃ gas and 60 sccm of C ₂ H ₂ gas at 1.3 torr and 500 to 700 ° C., and applying a bias of -500 to -700 V. Carbon nanotube growth method using. 10. The method of claim 9, Carbon nanotube growth method using DLC, characterized in that the carbon nanotubes formed in the growth step is grown in a multiwall (multiwall). Carbon nanotubes using DLC grown by the growth method of any one of claims 1 to 10.

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