WO2011036973A1

WO2011036973A1 - Process for production of carbon nanotube film

Info

Publication number: WO2011036973A1
Application number: PCT/JP2010/064351
Authority: WO
Inventors: 貴士松本; 正仁杉浦; 建次郎小泉; 勇作柏木
Original assignee: 東京エレクトロン株式会社
Priority date: 2009-09-25
Filing date: 2010-08-25
Publication date: 2011-03-31
Also published as: JP2011068513A

Abstract

A substrate to be treated, which has a metal catalyst layer formed on the surface thereof, is provided (step 1), the metal catalyst layer is subjected to an oxygen plasma treatment (step 2), the metal catalyst layer which has been treated with an oxygen plasma is subjected to a hydrogen-containing plasma treatment to activate the surface of the metal catalyst layer (step 3), and subsequently a carbon nanotube film is formed on the metal catalyst layer by means of plasma CVD (step 5).

Description

Method for forming carbon nanotube film

The present invention relates to a carbon nanotube film forming method for forming a carbon nanotube film by CVD using a catalytic metal.

Since carbon nanotubes have excellent electrical characteristics, application to applications such as wiring of semiconductor devices is being studied. As a method for forming a carbon nanotube film, a plasma layer is formed by forming a catalyst layer composed of fine particles of a transition metal such as Ni, Fe, Co on a substrate and using hydrocarbon gas and hydrogen gas for the substrate. Has proposed a method for forming a carbon nanotube film on a substrate (Japanese Patent Laid-Open No. 2007-252970: Patent Document 1).

In Patent Document 1, as a technique for preventing the surface of the fine particles from being oxidized and reducing the catalytic activity when the catalyst metal is finely divided, the surface of the catalyst metal is irradiated with radical species to prevent the catalyst surface from being oxidized. It is described to activate.

In order to use the carbon nanotube film as a via wiring, it is necessary to reduce the defects of the carbon nanotube and increase the density per unit area. Since the density of the carbon nanotube depends on the shape of the catalyst metal and the like, it is necessary to form the catalyst metal in a very fine and high density so that the carbon nanotube has a low defect and a high density. However, simply activating the catalyst metal as in Patent Document 1 described above does not make the catalyst metal sufficiently fine and dense, and it is difficult to obtain a desired low defect and high density carbon nanotube film. .

Accordingly, an object of the present invention is to provide a film forming method of a carbon nanotube film that can form a low-defect and high-density carbon nanotube film by forming a catalyst metal in a lower layer into fine particles and a high density. .

According to the present invention, preparing a substrate to be processed having a metal catalyst layer formed on the surface, subjecting the metal catalyst layer to oxygen plasma treatment, and containing hydrogen in the metal catalyst layer after the oxygen plasma treatment. Performing a plasma treatment to activate the surface of the metal catalyst layer; and forming a carbon nanotube film on the metal catalyst layer after the activation by plasma CVD. A method for forming a carbon nanotube film is provided.

It is sectional drawing which shows typically an example of the film-forming apparatus used in order to implement the film-forming method of the carbon nanotube film | membrane concerning the 1st Embodiment of this invention. 3 is a flowchart showing a carbon nanotube film forming method according to the first embodiment of the present invention. It is a schematic diagram which shows the structure of the wafer which has a metal catalyst on the film-forming surface used for the 1st Embodiment of this invention. It is a figure which shows the spatial potential in a chamber when not applying a voltage to a grid electrode. It is a figure which shows the spatial potential in a chamber at the time of applying a voltage to a grid electrode. It is sectional drawing which shows the modification of the apparatus used for the 1st Embodiment of this invention. It is sectional drawing which shows the other modification of the apparatus used for the 1st Embodiment of this invention. It is a schematic diagram which shows the structure of the wafer used for the Example of this invention. It is a figure which shows the process conditions of the Example of this invention. It is a graph which shows the relationship between the grid electrode voltage in each opening diameter of the grid electrode in the Example of this invention, and G / D ratio of the obtained carbon nanotube film | membrane. It is a scanning microscope (SEM) photograph which shows the carbon nanotube film | membrane formed into a film using two grid electrodes with a grid opening diameter of 2 mm. It is sectional drawing which shows typically an example of the film-forming apparatus used in order to enforce the film-forming method of the carbon nanotube film | membrane concerning the 2nd Embodiment of this invention. It is a flowchart which shows the film-forming method of the carbon nanotube film | membrane which concerns on the 2nd Embodiment of this invention.

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

<First Embodiment>
First, the first embodiment will be described.
(Configuration of film forming apparatus for carrying out the method of the first embodiment)
FIG. 1 is a cross-sectional view schematically showing an example of a film forming apparatus used for carrying out the method of forming a carbon nanotube film according to the first embodiment of the present invention. A film forming apparatus 100 shown in FIG. 1 is configured as an RLSA (Radial Line Slot Antenna) microwave plasma type plasma processing apparatus.

The film forming apparatus 100 includes a substantially cylindrical chamber 1, a susceptor (mounting table) 2 provided in the chamber 1 for mounting a semiconductor wafer (hereinafter simply referred to as a wafer) W as a substrate to be processed, and a chamber A charged particle control mechanism 3 that controls charged particles in plasma formed in 1, a microwave introduction mechanism 4 that introduces microwaves into the chamber 1, a gas supply mechanism 5 that guides gas into the chamber 1, An exhaust mechanism 6 that exhausts the inside of the chamber 1 and a control unit 7 that controls each component of the film forming apparatus 100 are provided.

A circular opening 10 is formed at a substantially central portion of the bottom wall 1a of the chamber 1, and an exhaust chamber 11 that communicates with the opening 10 and protrudes downward is provided on the bottom wall 1a. . On the side wall of the chamber 1, a loading / unloading port 17 for loading / unloading the wafer W and a gate valve 18 for opening / closing the loading / unloading port 17 are provided.

The susceptor 2 is made of ceramic such as AlN, and is supported by a support member 12 made of ceramic such as cylindrical AlN that extends upward from the center of the bottom of the exhaust chamber 11. A guide ring 13 for guiding the wafer W is provided on the outer edge of the susceptor 2. Further, elevating pins (not shown) for elevating the wafer W are provided inside the susceptor 2 so as to protrude and retract with respect to the upper surface of the susceptor 2. Further, a resistance heating type heater 14 is embedded in the susceptor 2, and the heater 14 is heated by the heater power supply 15 to heat the wafer W thereon via the susceptor 2. In addition, a thermocouple (not shown) is inserted into the susceptor 2 so that the heating temperature of the wafer W can be controlled in the range of 200 to 650 ° C. Further, an electrode 16 having the same size as the wafer W is embedded above the heater 14 in the susceptor 2, and this electrode 16 is grounded.

The microwave introduction mechanism 4 is provided so as to face the opening at the top of the chamber 1, and includes a planar antenna 21 in which a large number of microwave transmission holes 21a are formed, a microwave generator 22 that generates microwaves, And a microwave transmission mechanism 23 that guides the wave generator 22 to the planar antenna 21. A microwave transmission plate 24 made of a dielectric is provided below the planar antenna 21 so as to be supported by an upper plate 32 provided in a ring shape above the chamber 1, and a shield member 25 is disposed on the planar antenna 21. Is provided. Further, a slow wave material 26 made of a dielectric is provided between the shield member 25 and the planar antenna 21.

The microwave transmission mechanism 23 is a coaxial waveguide comprising a waveguide 27 extending in the horizontal direction for guiding microwaves from the microwave generator 22, an inner conductor 29 extending upward from the center of the planar antenna 21, and an outer conductor 30 outside thereof. A wave tube 28 and a mode conversion mechanism 31 provided between the waveguide 27 and the coaxial waveguide 28 are provided.

The gas supply mechanism 5 is provided in a ring shape along the inner wall of the chamber 1 at a position above the shower plate 41 and a shower plate 41 horizontally provided so as to partition the upper and lower sides above the susceptor 2 in the chamber 1. The shower ring 42 is provided.

The shower plate 41 includes a gas flow member 51 formed in a lattice shape, a gas flow path 52 provided in a lattice shape inside the gas flow member 51, and a number of gases extending downward from the gas flow path 52. It has a discharge hole 53, and a through-hole 54 is formed between the lattice-like gas flow members 51. A gas supply path 55 reaching the outer wall of the chamber 1 extends in the gas flow path 52 of the shower plate 41, and a gas supply pipe 56 is connected to the gas supply path 55. The gas supply pipe 56

branch pipe

56a, 56b, branches into three 56c, these

branch pipes

56a, 56b, the 56c, _{H 2} gas to supply _{H 2} gas supply source 57 as the respective reduction gas supplies ethylene _(C 2 _{H 4)} gas as a raw material gas _C 2 _{H 4} gas supply source 58, _{N 2} gas supply source 59 for supplying _{N 2} gas as a purge gas is connected. Although not shown, the

branch pipes

56a, 56b, and 56c are provided with a mass flow controller for flow rate control and valves before and after the mass flow controller.

The shower ring 42 has a ring-shaped gas flow path therein and a large number of gas discharge holes (none of which are shown) connected to the gas flow path and opening inside thereof. A gas supply pipe 61 is connected to the. The gas supply pipe 61 is branched into three

branch pipes

61a, 61b, and 61c. An Ar gas supply source 62 that supplies Ar gas as a plasma generation gas to each of the

branch pipes

61a, 61b, and 61c, supplying _{O 2} gas as an oxidizing gas _{O 2} gas supply source 63, for supplying _{N 2} gas as a purge _{N 2} gas supply source 64 is connected. The

branch pipes

61a, 61b, and 61c are provided with a mass flow controller for flow rate control and valves before and after that, although not shown.

The charged particle control mechanism 3 includes a grid electrode 71, a support member 72 that supports the grid electrode, a variable DC power source 73 that applies a DC voltage to the grid electrode 71 via the support member 72, and a pulse signal to the variable DC power source 73. And a pulse generator 74. The grid electrode 71 is provided directly below the shower plate 41 so as to cover the wafer W on the susceptor 2 and has a net shape having a large number of openings, and also functions as a shielding member. The outer periphery of the grid electrode 71 reaches the vicinity of the inner wall of the chamber 1, and an insulating ring 75 made of an insulator is provided between the grid electrode 71 and the inner wall of the chamber 1 so as to fill a gap therebetween. Yes. This insulating ring 75 can surely prevent plasma from leaking from the gap between the grid electrode 71 and the chamber 1. However, if there is a gap between the grid electrode 71 and the inner wall of the chamber 1, the insulating ring 75 may not be provided if plasma leakage can be sufficiently prevented.

In this way, the grid electrode 71 functions as a shielding member to prevent transmission of charged particles such as electrons and ions that may damage the surface of the wafer W, thereby suppressing the arrival of charged particles to the wafer W. Further, by applying a DC voltage from the variable DC power source 73 to the grid electrode 71, charged particles such as electrons and ions are repelled or attracted by the grid electrode 71 to prevent these particles from going straight, and the charged particles reach the wafer W. Suppress more effectively. For example, by applying a negative DC voltage to the grid electrode 71, electrons and negative ions can be repelled mainly to prevent the electrons from reaching the wafer W. In this case, by applying a predetermined pulse from the pulse generator 74, the voltage application to the grid electrode 71 can be made pulsed. Of course, it is also possible to apply a normal DC voltage without generating a pulse. In addition, by making the voltage applied to the grid electrode 71 into a pulse shape by the pulse generator 74, there is an effect that even an insulating substrate can be processed without charging the substrate surface.

The exhaust mechanism 6 includes the exhaust chamber 11, an exhaust pipe 81 provided on a side surface of the exhaust chamber 11, and an exhaust device 82 having a vacuum pump, a pressure control valve, and the like connected to the exhaust pipe 81.

The control unit 7 includes a calculation unit 91 including a microprocessor (computer), a user interface 92, and a storage unit 93. Each component of the film forming apparatus 100 is electrically connected to the calculation unit 91 and controlled. The user interface 92 is connected to the calculation unit 91, and a keyboard on which an operator inputs a command to manage each component of the film forming apparatus 100, and an operation status of each component of the film forming device 100. It consists of a display etc. that visualizes and displays. The storage unit 93 is also connected to the calculation unit 91, and the storage unit 93 stores control programs for realizing various processes executed by the film forming apparatus 100 under the control of the calculation unit 91, processing conditions, and the like. Accordingly, a control program for causing each component of the film forming apparatus 100 to execute a predetermined process, that is, a process recipe, various databases, and the like are stored. The processing recipe is stored in a storage medium (not shown) in the storage unit 93. The storage medium may be a fixed medium such as a hard disk or a portable medium such as a CDROM, DVD, or flash memory. Moreover, you may make it transmit a recipe suitably from another apparatus via a dedicated line, for example.

Then, if necessary, a predetermined processing recipe is called from the storage unit 93 by an instruction from the user interface 92 and executed by the calculation unit 91, so that the film forming apparatus 100 can control the control unit 7. Desired processing is performed.

(Method for Forming Carbon Nanotube Film According to First Embodiment)
Next, a carbon nanotube film forming method performed by the film forming apparatus 100 configured as described above will be described with reference to FIG.
FIG. 2 is a flowchart for explaining a carbon nanotube film forming method according to the first embodiment of the present invention.

First, a wafer W having a metal catalyst on the film formation surface is prepared, the gate valve 18 is opened, and the wafer W is loaded into the chamber 1 (step 1). As the wafer W at this time, for example, as shown in FIG. 3, a SiO ₂ film 202 is formed as an insulating film on a Si substrate 201, and a metal catalyst layer 204 is formed thereon via an underlayer 203. Is used.

Examples of the metal constituting the metal catalyst layer 204 include transition metals such as Ni, Co, and Fe, or alloys containing at least one transition metal. As a method for forming the metal catalyst layer 204, a film formation technique generally used in this field, such as a thin film formation technique such as sputtering, vapor deposition, CVD, or plating, can be used. The thickness of the metal catalyst layer 204 is preferably 0.1 to 2.0 nm.

The underlayer 203 functions as a film that prevents coarsening due to aggregation of the metal catalyst, and examples thereof include Al, Si, Ta, Ti, TiN, TiC, Al ₂ O ₃ , and MgO. Similarly, the underlying layer 203 can be formed by a film forming technique generally used in this field. The thickness of the underlayer 203 is preferably 10 to 100 nm.

After the semiconductor wafer W having such a structure is loaded into the chamber 1 and placed on the susceptor 2, the metal catalyst layer 204 is subjected to oxygen plasma treatment (step 2). In step 2, Ar gas and O ₂ gas are introduced into the chamber 1 from the shower ring 42, and the microwave generated by the microwave generation unit 22 is converted into a planar antenna in a predetermined mode via the microwave transmission mechanism 23. 21 is transmitted through the microwave transmitting hole 21 a and the microwave transmitting plate 24 of the planar antenna 21 and supplied uniformly into the chamber 1. Then, Ar gas and O ₂ gas are converted into plasma by the microwave, and oxygen plasma treatment is performed on the surface of the metal catalyst layer 204 on the surface of the wafer W by the microwave plasma.

This treatment is a treatment that removes organic substances and the like attached to the surface of the metal catalyst layer 204 to make a clean surface, and this facilitates migration due to heating on the surface of the metal catalyst layer 204. Appropriate agglomeration occurs in the metal constituting 204, and the formation of fine particles can be facilitated.

The preferable conditions for this oxygen plasma treatment are as follows.
Wafer temperature: 300-600 ° C
Chamber pressure: 67-533Pa
O ₂ gas flow rate: 50 to 200 mL / min (sccm)
Ar gas flow rate: 300 to 600 mL / min (sccm)
Microwave power: 250-2000W
Processing time: 5-10 minutes

At the time of the oxygen plasma treatment in step 2, the grid electrode 71 functions as a shielding member, and electrons and ions in the plasma are suppressed from reaching the metal catalyst layer 204 on the surface of the wafer W. Radicals can mainly act without damaging electrons or ions. For this reason, the effect of aggregating the metal of the metal catalyst layer 204 appropriately can be exhibited more effectively. Then, by applying a voltage to the grid electrode 71, it is possible to prevent the charged particles such as electrons and ions from going straight and to more effectively prevent the charged particles from reaching the wafer W. The effect of appropriately aggregating the metal of the layer 204 can be further enhanced. In this case, the opening diameter of the grid electrode 71 is preferably 2 mmφ or less, and the opening ratio is preferably 40 to 85%. The voltage applied to the grid electrode 71 is preferably −300 to 300V. From the viewpoint of effectively suppressing the arrival of electrons, a negative voltage is good, and −300 to 0 V is more preferable.

The effect when a voltage is applied to the grid electrode 71 will be described with reference to FIGS. 4A and 4B. 4A is a diagram showing the spatial potential in the chamber 1 when no voltage is applied to the grid electrode 71, and FIG. 4B is a diagram showing the spatial potential in the chamber 1 when −100V is applied to the grid electrode 71. . As is apparent from these figures, when no voltage is applied to the grid electrode 71, there is no potential difference between the shower plate 41 and the wafer W, but no electrical action occurs on charged particles such as electrons and ions. When the grid electrode is provided and −100 V is applied thereto, the grid electrode 71 has a negative potential with respect to the grounded shower plate 41 and the wafer W (susceptor 2). It becomes difficult for negatively charged charged particles such as negative ions to reach the wafer W.

As a gas for performing this oxygen plasma treatment, H ₂ O, O ₃ , N ₂ O, or the like can be used in addition to O ₂ gas.

Following the oxygen plasma treatment in step 2 as described above, an activation treatment is performed (step 3). In this activation process, after the end of step 2, the microwave is stopped, the O ₂ gas is stopped, and the Ar gas is kept flowing. Similarly, the microwave generator 22, the microwave transmission mechanism 23, and the planar antenna 21 are used. Then, the microwave is uniformly supplied into the chamber 1 through the microwave transmission plate 24. The Ar gas is turned into plasma by the microwave, and H ₂ gas is introduced into the chamber 1 through the shower plate 41 at the timing when the plasma is ignited, and the H ₂ gas is turned into plasma by Ar plasma. Then, the surface of the metal catalyst layer 204 is activated by the microwave plasma thus formed.

This activation treatment is a treatment for activating the metal catalyst by reducing the surface of the metal catalyst layer 204 oxidized by the oxygen plasma treatment in step 2. That is, by performing the treatment with the hydrogen plasma in this way, the surface of the metal catalyst layer 204 is activated, and the metal constituting the metal catalyst layer 204 can be finely divided and densified.

Preferred conditions for this activation treatment are as follows.
Wafer temperature: 300-600 ° C
Chamber pressure: 67-533Pa
H ₂ gas flow rate: 100 to 1200 mL / min (sccm)
Ar gas flow rate: 300 to 600 mL / min (sccm)
Microwave power: 250-2000W
Treatment time: 5 to 10 minutes The temperature during this activation treatment may be different from the oxygen plasma treatment, but it is preferable to carry out at the same temperature because the throughput can be increased.

Also in the activation process of step 3, the grid electrode 71 functions as a shielding member, and electrons and ions in the plasma are suppressed from reaching the metal catalyst layer 204 on the surface of the wafer W. Radicals can mainly act without damaging electrons or ions. For this reason, the effect of activating the surface of the metal catalyst layer 204 to make the metal constituting the metal catalyst layer 204 fine particles and increasing the density can be more effectively exhibited. Then, by applying a voltage to the grid electrode 71, it is possible to prevent the charged particles such as electrons and ions from going straight, and more effectively prevent the charged particles from reaching the wafer W. The effect of making the surface of the metal catalyst layer 204 fine particles and increasing the density by activating the surface can be further enhanced. In this case, the opening diameter of the grid electrode 71 is preferably 2 mmφ or less, and the opening ratio is preferably 40 to 85%. The voltage applied to the grid electrode 71 is preferably −300 to 300V. From the viewpoint of effectively suppressing the arrival of electrons, a negative voltage is good, and −300 to 0 V is more preferable.

As a gas for performing this activation treatment, other H-containing gas, for example, NH ₃ gas can be used instead of H ₂ gas.

After the activation process of step 3, the microwave and H ₂ gas are stopped, and Ar gas and N ₂ gas are flowed to purge the chamber 1 (step 4). At this time, the inside of the chamber 1 is rapidly exhausted by the exhaust device 82.

The purge is performed under the conditions of, for example, a chamber pressure of 67 to 533 Pa, an N ₂ gas flow rate of 50 to 300 mL / min (sccm), an Ar gas flow rate of 300 to 600 mL / min (sccm), and a temperature of 300 to 600 ° C. Preferably it is performed for 1-2 minutes.

After purging in step 4, a carbon nanotube film is formed (step 5). In the formation of the carbon nanotube film, after purging in Step 4, the N ₂ gas is stopped and the Ar gas is allowed to flow at a predetermined flow rate, and the microwave generator 22, the microwave transmission mechanism 23, the planar antenna 21, A microwave is uniformly supplied into the chamber 1 through the microwave transmission plate 24. By its microwave into a plasma of Ar gas, the C ₂ H ₄ gas and H ₂ gas was introduced into the chamber 1 through the shower plate 41 at the timing when the plasma is ignited, C ₂ H ₄ gas and the Ar plasma H ₂ gas is turned into plasma. Then, a carbon nanotube film is formed on the metal catalyst layer 204 by the microwave plasma thus formed while applying a predetermined voltage to the grid electrode 71.

In the formation of the carbon nanotube film, a carbon nanotube film oriented in a direction perpendicular to the surface of the wafer W can be grown on the surface of the activated metal catalyst layer 204. In this case, the carbon nanotube film grows while maintaining the properties of the metal catalyst layer 204. Accordingly, fine and high-density carbon nanotubes can be formed on the metal catalyst layer 204 that has been activated and refined by the activation treatment in step 3. Further, the grid electrode 71 functions as a shielding member, so that electrons and ions in the plasma are prevented from reaching the metal catalyst layer 204 on the surface of the wafer W, and the metal catalyst layer 204 is not damaged by electrons and ions. Can mainly act on radicals. For this reason, it is possible to suppress the introduction of crystal defects or impurities due to electrons or ions, and it is possible to form a carbon nanotube film with few impurities and good crystallinity. Then, by applying a voltage to the grid electrode 71, it is possible to prevent the charged particles such as electrons and ions from moving straight, and to more effectively suppress the arrival of the charged particles to the wafer W. A carbon nanotube film with good properties can be formed.

The preferable conditions for the film forming process of the carbon nanotube film are as follows.
Wafer temperature: 300-600 ° C
Chamber pressure: 67-533Pa
C ₂ H ₄ gas flow rate: 5 to 150 mL / min (sccm)
H ₂ gas flow rate: 100 to 1200 mL / min (sccm)
Ar gas flow rate: 300 to 600 mL / min (sccm)
Microwave power: 250-2000W
Treatment time: 1 to 60 minutes The temperature during this activation treatment may be different from the oxygen plasma treatment and the activation treatment, but it is preferable to carry out at the same temperature because the throughput can be increased.

Also in this carbon nanotube film forming process, the grid diameter of the grid electrode 71 is preferably 2 mmφ or less, and the aperture ratio is preferably 40 to 85%. The voltage applied to the grid electrode 71 is preferably −300 to 300V. From the viewpoint of effectively suppressing the arrival of electrons, a negative voltage is good, and −300 to 0 V is more preferable.

In the carbon nanotube film forming process, not only ethylene (C ₂ H ₄ ) gas but also methane (CH ₄ ) gas, ethane (C ₂ H ₆ ) gas, propane (C ₃ H ₈ ) gas, propylene Other hydrocarbon gases such as (C ₂ H ₆ ) gas can be used. The reducing gas is not limited to H ₂ gas, and other gases such as ammonia (NH ₃ ) can be used.

After the formation of such a carbon nanotube film, the supply of microwaves and gas is stopped, the pressure in the chamber 1 is adjusted, the gate valve 18 is opened, and the wafer W is unloaded (step 6).

According to the present embodiment, as described above, the wafer W having the metal catalyst layer 204 on the surface is subjected to oxygen plasma treatment, and subsequently subjected to activation treatment using hydrogen plasma, and then the carbon nanotube film is formed by plasma CVD. Is deposited. For this reason, the surface of the metal catalyst layer 204 is cleaned by oxygen plasma treatment to facilitate migration due to heating on the surface of the metal catalyst layer 204, and moderate aggregation occurs in the metal constituting the metal catalyst layer 204, resulting in fine particles. It is possible to facilitate progress. Further, by the activation treatment with hydrogen plasma after that, the surface of the metal catalyst layer 204 can be activated to make the metal constituting the metal catalyst layer 204 fine and dense. For this reason, in the subsequent film formation of the carbon nanotube film, it is possible to grow a carbon nanotube film having a high density and oriented perpendicular to the substrate surface on the finely divided and densified catalyst metal layer 204. it can.

In addition, since the grid electrode functioning as a shielding member is provided between the shower plate 41 and the wafer W, it is possible to suppress electrons and ions in the plasma from reaching the metal catalyst layer 204 on the surface of the wafer W. For this reason, radicals can act mainly on the metal catalyst layer 204 without damaging the electrons and ions, so that the introduction of crystal defects and impurities due to the electrons and ions can be suppressed. A good carbon nanotube film can be formed. Furthermore, such an effect can be further enhanced by applying a voltage to the grid electrode 71.

Furthermore, in this embodiment, since the processing is performed with microwave plasma, plasma processing mainly consisting of radicals having a high density and a low electron temperature can be performed, and the above-described effects can be effectively exhibited. In particular, in the present embodiment, since an RLSA microwave plasma type plasma processing apparatus that forms microwave plasma by radiating microwaves from a number of microwave radiation holes 21 a of the planar antenna 21 is used. Among them, particularly high density and low electron temperature plasma can be generated.

(Another apparatus example of the first embodiment)
Next, another example of the apparatus according to the first embodiment will be described.
In the apparatus of FIG. 1, an example in which one grid electrode 71 is provided in the charged particle control mechanism 3 has been shown. However, as shown in FIG. 5, two

grid electrodes

71a and 71b are provided so as to overlap each other. Also good. Thereby, the effect which shields charged particles, such as an electron and an ion, can be made higher by using these as a shielding member. An insulating ring 75 is provided between the

grid electrodes

71a and 71b and the inner wall of the chamber 1 as in the apparatus of FIG. However, the insulating ring 75 is not essential as in the apparatus of FIG. By connecting

DC power sources

73a and 73b and

pulse generators

74a and 74b to the

grid electrodes

71a and 71b, respectively, an appropriate voltage is applied to at least one of them, and charged particles such as electrons and ions are applied to the wafer W. Reaching can be prevented more effectively. For this reason, in the formation of the carbon nanotube film, it is possible to form a carbon nanotube film with fewer impurities and better crystallinity than in the case of providing one grid electrode. Also in the oxygen plasma treatment and the activation treatment, by providing two grids in this way, the metal of the metal catalyst layer 204 is appropriately aggregated, and the surface of the metal catalyst layer 204 is activated to activate the metal. The effect of making the metal constituting the catalyst layer 204 fine particles and increasing the density can be further enhanced.

In this case, the diameter of the openings of the

grid electrodes

71a and 71b is preferably 2 mmφ or less, and the opening ratio is preferably 40 to 85%. The voltage applied to the

grid electrodes

71a and 71b is preferably −300 to 300V.

Furthermore, as shown in FIG. 6, a variable DC power supply 95 and a pulse generator 96 may be connected to the susceptor 2. Also by this, charged particles such as electrons and ions can be prevented from reaching the surface of the wafer W. For example, by applying a negative DC voltage to the susceptor 2, the wafer W has a negative voltage, and electrons and negative ions are repelled and do not easily reach the surface of the wafer W.

(Example)
Next, specific examples will be described.
Here, as shown in FIG. 7, a blanket in which a TiN underlayer 303 is formed with a thickness of 70 nm on a SiO ₂ film 302 formed on a Si substrate 301 and a Ni catalyst layer 304 is formed thereon with a thickness of 2 nm. A carbon nanotube film was formed using a wafer. At that time, after the wafer is first loaded into the chamber 1 of the apparatus of FIG. 1, oxygen plasma treatment and activation treatment are sequentially performed under the conditions shown in FIG. A nanotube film was formed. At that time, three types of grid electrodes having an opening diameter of 5 mm (opening ratio 61.4%), 2 mm (opening ratio 80.7%), and 1 mm (opening ratio 40.1%) were used, and a carbon nanotube film was used. The voltage applied to the grid electrode 71 during film formation was changed from −100 to + 100V. Carbon nanotubes were also formed in the apparatus of FIG. 5 having two grid electrodes (opening diameter 2 mm (opening ratio 80.7%)). When the carbon nanotube film was formed, a test was performed in which no voltage was applied to the upper grid electrode and the voltage to the lower grid electrode was changed from −100 to + 50V.

The crystallinity of the carbon nanotube film thus formed was evaluated by Raman spectroscopy. Specifically, from the intensity ratio (G / D ratio) of G-band (1585 cm ⁻¹ ) due to the graphene structure in the Raman spectrum and D-band (1350 cm ⁻¹ ) indicating disorder of the crystallinity of the graphene sheet. The crystallinity was evaluated. The higher the G / D ratio, the better the crystallinity.

In the case of a single grid electrode, three types of grid electrodes having a grid diameter of 1 mm, 2 mm, and 5 mm were used, and a voltage was applied in the range of −100 to +100 V to obtain the G / D ratio. In the case of two grid electrodes, a grid electrode having a grid diameter of 2 mm is used, and no voltage is applied to the lower grid electrode, and a voltage to the upper grid electrode is applied in the range of −100 to + 50V. The G / D ratio was determined. The result is shown in FIG. In FIG. 9, the voltage applied to the grid electrode is taken on the horizontal axis and the G / D ratio is taken on the vertical axis, and these relationships are summarized for each grid diameter. As shown in this figure, it was confirmed that the G / D ratio was improved and the crystallinity of the carbon nanotube film was improved as the opening diameter of the grid electrode 71 was reduced, and the opening diameter was preferably 2 mm or less. . It was also confirmed that the G / D ratio was improved when the applied voltage was a negative voltage rather than a positive voltage. In the case of one grid electrode, the G / D ratio was highest when the opening diameter was 1 mm and the applied voltage was −100 V, and the G / D ratio was 0.9. It was also confirmed that using two grid electrodes with an opening diameter of 2 mm resulted in a higher G / D ratio than when using one grid electrode with the same opening diameter. It was also confirmed that when two grid electrodes were used, a high G / D ratio could be obtained without applying a voltage.

A cross section of a sample with a high G / D ratio obtained using two grid electrodes was photographed with a scanning microscope (SEM). The photograph is shown in FIG. As shown in this figure, it was confirmed that a carbon nanotube film having a high density and oriented perpendicular to the substrate surface was obtained.

From the above, the wafer on which the metal catalyst layer is formed is subjected to oxygen plasma treatment using microwave plasma of O ₂ gas and activation treatment using microwave plasma of H ₂ gas, and then the opening diameter and application of the grid electrode are applied. It was confirmed that a carbon nanotube film with good crystallinity can be obtained by adjusting the voltage and forming the carbon nanotube film by microwave plasma CVD.

<Second Embodiment>
Next, a second embodiment of the present invention will be described.
(Configuration of film forming apparatus for carrying out the method of the second embodiment)
FIG. 11 is a schematic view showing an example of a film forming apparatus used for carrying out the carbon nanotube film forming method according to the second embodiment of the present invention. This film forming apparatus is a multi-chamber capable of continuously performing oxygen plasma treatment, activation treatment using hydrogen plasma, and film formation of a carbon nanotube film in separate chambers without breaking the vacuum. Type.

The film forming apparatus 100 ′ includes an oxygen plasma processing unit 101, an activation processing unit 102, and a film forming unit 103 which are maintained in a vacuum. These units 101 to 103 basically have the above-described film forming. It is configured as an RLSA microwave plasma type plasma processing apparatus similar to the apparatus 100, and these are connected via a gate valve G to a transfer chamber 105 held in a vacuum. In addition,

load lock chambers

106 and 107 are connected to the transfer chamber 105 through gate valves G. An air loading / unloading chamber 108 is connected to the side surface of the

load lock chamber

106, 107 opposite to the transfer chamber 105, and on the opposite side of the loading / unloading chamber 108 from the connecting portion of the

load lock chamber

106, 107. Three

carrier attachment ports

109, 110, and 111 for attaching the carrier C capable of accommodating the wafer W are provided.

In the transfer chamber 105, a transfer device 112 that loads and unloads the wafer W with respect to the oxygen plasma processing unit 101, the activation processing unit 102, the carbon nanotube film forming unit 103, and the

load lock chambers

106 and 107 is provided. ing. The transfer device 112 is provided at substantially the center of the transfer chamber 105, and has two

support arms

114a and 114b that support the semiconductor wafer W at the tip of a rotatable / extensible / retractable portion 113 that can be rotated and extended. These two

support arms

114a and 114b are attached to the rotation / extension / contraction section 113 so as to face opposite directions.

In the loading / unloading chamber 108, a transfer device 116 for loading / unloading the wafer W into / from the carrier C and loading / unloading the wafer W into / from the

load lock chambers

106 and 107 is provided. The transfer device 116 has an articulated arm structure, and can run on the rail 118 along the arrangement direction of the carrier C. The wafer W is placed on the support arm 117 at the tip thereof and transferred. I do.

This film forming apparatus includes a control unit 120 that controls each component, and thereby each component of the oxygen plasma processing unit 101, each component of the activation processing unit 102, and each of the carbon nanotube film forming unit 103. Control is performed such as opening / closing of each component, the

transfer devices

112 and 116, the exhaust system (not shown) of the transfer chamber 105, and the gate valve G. The control unit 120 is configured similarly to the control unit 7 of the first embodiment.

(Method for Forming Carbon Nanotube Film According to Second Embodiment)
Next, a method of forming a carbon nanotube film according to this embodiment using the film forming apparatus configured as described above will be described.
FIG. 12 is a flowchart for explaining a carbon nanotube film forming method according to the second embodiment of the present invention.

First, a wafer W having a metal catalyst on a film formation surface similar to that shown in FIG. 3 is prepared and carried into the film formation apparatus 100 ′ (step 11). Specifically, the wafer W is taken out from the carrier C by the transfer device 116 in the loading / unloading chamber 108 and transferred to one of the

load lock chambers

106 and 107.

Next, after evacuating the load lock chamber, the wafer W is taken out by the transfer device 112 of the transfer chamber 105 and transferred to the oxygen plasma processing unit 101 to perform oxygen plasma treatment on the metal catalyst layer of the wafer W. (Step 12). The oxygen plasma treatment at this time is performed in the same manner as in step 2 of the first embodiment.

Thereafter, the wafer W after the oxygen plasma processing is taken out from the oxygen plasma processing unit 101 by the transfer device 112 and transferred to the activation processing unit 102 where the metal catalyst layer of the wafer W is activated by hydrogen plasma. Processing is performed (step 13). The activation process at this time is performed in the same manner as in step 3 of the first embodiment.

Thereafter, the wafer W after the activation process is taken out from the activation process unit 102 by the transfer device 112 and transferred to the film formation unit 103, where the film formation process of the carbon nanotube film is performed (step 14). The film forming process at this time is performed in the same manner as in step 5 of the first embodiment.

Thereafter, the wafer after the carbon nanotube film is formed is taken out from the film forming unit 103 by the transfer device 112, transferred to one of the

load lock chambers

106 and 107, and the load lock chamber is returned to atmospheric pressure. It is carried out to one of the carriers C by the transport device 116 (step 15).

In the first embodiment, an apparatus that can efficiently and continuously perform oxygen plasma treatment, activation treatment, and carbon nanotube film formation treatment in one chamber is used. However, when the conditions of these three processes are different, the efficiency is not always good, and when it is desired to divide the gas supply system of the apparatus into each process, or an apparatus having a slightly different apparatus configuration between these three processes. In some cases (for example, the presence or absence of a grid electrode). This embodiment is suitable for such a case.

11 shows an example in which each process is performed in separate units (chambers). For example, the oxygen plasma process and the activation process are performed in one unit (chamber) to form a carbon nanotube film. At least one process may be performed in a separate unit (chamber), such as in another unit (chamber).

<Other applications of the present invention>
The present invention can be variously modified without being limited to the above embodiment. For example, in the above-described embodiment, the example in which the oxygen plasma treatment, the activation treatment, and the carbon nanotube film formation treatment are performed by the plasma treatment apparatus of the RLSA microwave plasma method is shown. A method may be used, and not only microwave plasma but also inductively coupled plasma or capacitively coupled plasma may be used. However, microwave plasma is preferable because it is low electron temperature plasma mainly composed of radicals. Further, the structure of the wafer is not limited to that of FIG. 2 as long as the metal catalyst layer is formed on the surface, and the substrate to be processed is not limited to the semiconductor wafer.

Claims

Preparing a substrate to be processed having a metal catalyst layer formed on the surface;
Performing oxygen plasma treatment on the metal catalyst layer;
Subjecting the metal catalyst layer after the oxygen plasma treatment to a hydrogen-containing plasma treatment to activate the surface of the metal catalyst layer;
A method of forming a carbon nanotube film, comprising: forming a carbon nanotube film on the metal catalyst layer after the activation by plasma CVD.
2. The method of forming a carbon nanotube film according to claim 1, wherein the substrate to be processed is heated to 300 to 600 ° C. during the oxygen plasma treatment, the activation treatment, and the formation of the carbon nanotube film.
When forming the carbon nanotube film, a shielding member having a large number of openings is provided so as to shield the substrate to be processed immediately above the substrate to be processed, and the generated plasma is passed through the shielding member through the shielding member. The method of forming a carbon nanotube film according to claim 1, wherein the carbon nanotube film is made to reach a treatment substrate.
4. The method of forming a carbon nanotube film according to claim 3, wherein at least two shielding members are provided in the vertical direction.
4. The method of forming a carbon nanotube film according to claim 3, wherein a DC voltage is applied to the shielding member when forming the carbon nanotube film.
The method of forming a carbon nanotube film according to claim 5, wherein a negative DC voltage is applied to the shielding member.
The method of forming a carbon nanotube film according to claim 4, wherein a DC voltage is applied to at least one of the shielding members when forming the carbon nanotube film.
The method of forming a carbon nanotube film according to claim 3, wherein the opening of the shielding member has a diameter of 2 mm or less.
When performing the oxygen plasma treatment, a shielding member having a large number of openings is provided so as to shield the substrate to be treated immediately above the substrate to be treated, and the generated plasma is passed through the shielding member to the substrate to be treated. The method of forming a carbon nanotube film according to claim 1, wherein
10. The method of forming a carbon nanotube film according to claim 9, wherein at least two shielding members are provided so as to overlap each other in the vertical direction.
The method of forming a carbon nanotube film according to claim 9, wherein a DC voltage is applied to the shielding member when the oxygen plasma treatment is performed.
The method of forming a carbon nanotube film according to claim 11, wherein a negative DC voltage is applied to the shielding member.
The method of forming a carbon nanotube film according to claim 10, wherein a DC voltage is applied to at least one of the shielding members when the oxygen plasma treatment is performed.
The method of forming a carbon nanotube film according to claim 9, wherein the opening of the shielding member has a diameter of 2 mm or less.
When performing the activation process, a shielding member having a large number of openings is provided so as to shield the substrate to be processed immediately above the substrate to be processed, and the generated plasma is supplied to the substrate to be processed through the shielding member. The method of forming a carbon nanotube film according to claim 1, wherein
The carbon nanotube film forming method according to claim 15, wherein at least two of the shielding members are provided so as to overlap each other in the vertical direction.
The method of forming a carbon nanotube film according to claim 15, wherein a DC voltage is applied to the shielding member when performing the activation treatment.
The method of forming a carbon nanotube film according to claim 17, wherein a negative DC voltage is applied to the shielding member.
The method of forming a carbon nanotube film according to claim 16, wherein a DC voltage is applied to at least one of the shielding members when performing the activation treatment.
The carbon nanotube film forming method according to claim 15, wherein the opening of the shielding member has a diameter of 2 mm or less.
The method for forming a carbon nanotube film according to claim 1, wherein the plasma during the oxygen plasma treatment, the activation treatment, and the carbon nanotube film formation is microwave plasma.
The method of forming a carbon nanotube film according to claim 1, wherein the oxygen plasma treatment, the activation treatment, and the carbon nanotube film are continuously formed in the same chamber.
The method of forming a carbon nanotube film according to claim 1, wherein at least one of the oxygen plasma treatment, the activation treatment, and the carbon nanotube film formation is performed in a chamber different from the others.