JP3836797B2 - Particle deposition layer forming apparatus and particle deposition layer forming method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a particle deposition layer forming apparatus and a particle deposition layer forming method.
[0002]
[Prior art]
Nanometer-sized particles have a large specific surface area (surface area per unit volume), and have characteristics that are not found in conventional fine particles, such as a quantum size effect. Therefore, these nanometer-sized particles have been attracting attention as a new form of material in recent years, and their application to recording media, battery electrodes, visible light LED elements, display phosphors, and the like are being studied.
[0003]
Nanometer-sized particles can be produced, for example, by a gas phase method using plasma. For example, E.I. Bertran et al. Have the following reaction formula:
SiH ₄ + CH ₄ → SiC + 4H ₂
As shown in FIG. 1, a method of generating SiC particles by using monosilane and methane as raw material gases and reacting them using plasma is disclosed (see Non-Patent Document 1 below).
[0004]
However, the particles obtained by this method have a large variation in particle size. In order to utilize the features described above for nanometer-sized particles, it is necessary to align their particle sizes.
[0005]
Therefore, in this method, the following steps are sequentially performed in order to form the particle deposition layer. That is, first, particles generated together with exhaust gas from the reaction vessel are collected while generating particles using plasma. Next, the collected particles are classified to make the particle sizes uniform. Thereafter, particles having a uniform particle diameter are dispersed in the liquid, and this dispersion is applied onto the substrate. Thus, in the prior art, a number of processes are required to form a particle deposition layer having a uniform particle size.
[0006]
[Non-Patent Document 1]
E. Bertran et al., “Journal of Vacuum Science & Technology A”, USA, March / April 1996, Vol. 14, No. 2, p. 567
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a particle deposition layer forming apparatus and a particle deposition layer forming method capable of forming a particle deposition layer having a uniform particle size with a relatively small number of steps.
[0008]
[Means for Solving the Problems]
According to the present invention, a reaction chamber to which a source gas is supplied, a rear chamber provided with an exhaust port, a holder disposed in the rear chamber and capable of holding a substrate, and plasma generation for generating plasma in the reaction chamber An apparatus and a control unit that controls the operation of the plasma generator so that generation and extinction of the plasma are alternately and repeatedly switched while holding the substrate in the holder, and reacting the source gas Thus, there is provided a particle deposition layer forming apparatus characterized in that particles are generated and the particles are deposited on the substrate while maintaining the shape as the particles.
[0009]
According to the present invention, the source gas is supplied to the reaction chamber and the plasma is generated in the reaction chamber while exhausting from the rear chamber located downstream of the reaction chamber, so that the reaction of the source gas is generated in the plasma. And growing the particles as an object, and depositing the particles grown in the plasma by extinguishing the plasma on a substrate disposed in the rear chamber, the growing step and the deposition And a step of depositing the particles on the substrate while maintaining the morphology of the particles as a particle.
[0010]
In the present invention, the time t _ON during which the plasma is generated is set to be shorter than the time t _c calculated by dividing the volume V of the region in the reaction chamber where the plasma is formed by the flow rate F of the gas flowing through the reaction chamber. May be. Further, the substrate may be charged prior to the particle growth step and the particle deposition step. In the particle deposition step, the particles supplied from the reaction chamber may be mass separated and deposited on the substrate. The particle growth step may be performed while supplying an etching gas for etching particles into the reaction chamber.
[0011]
In the present invention, the source gas may contain, for example, at least one element selected from the group consisting of iron, cobalt and chromium and platinum. The source gas is, for example, a compound containing iron, a compound containing platinum, or a compound containing iron and platinum, and copper, silver, tin, antimony, lead, gallium, mercury, molybdenum, and tungsten. And a compound containing at least one element selected from the group consisting of:
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same referential mark is attached | subjected to the same or similar component, and the overlapping description is abbreviate | omitted.
[0013]
FIG. 1 is a diagram schematically showing a particle deposition layer forming apparatus according to a first embodiment of the present invention. The particle deposition layer forming apparatus 1 includes a reaction vessel 2. The reaction vessel 2 has, for example, a tubular shape, and a front chamber 21, a reaction chamber 22, and a rear chamber 23 are defined therein. A source gas supply port 24 communicating with the front chamber 21 is provided at one end of the reaction vessel 2, and the source gas is supplied to the front chamber 21 through the source gas supply port 24. Further, an exhaust port 25 communicating with the rear chamber 23 is provided at the other end of the reaction vessel 2, and exhaust is performed through the exhaust port 25. Note that the exhaust gas discharged through the exhaust port 25 is cooled by the cooler 8.
[0014]
A holder 3 is arranged in the rear chamber 23 of the reaction vessel 2. The holder 3 holds the substrate 4 in a detachable manner with the substrate 4 facing the reaction chamber 22. In addition, the reaction vessel 2 is provided with a plasma generator 5 for generating plasma in the reaction chamber 22.
[0015]
The plasma generator 5 is connected to the controller 6. The controller 6 controls the operation of the plasma generator 5. Specifically, the control unit 6 can control the operation of the plasma generator 5 so that the generation and extinction of plasma are alternately and repeatedly switched at an extremely high speed, for example, on the order of milliseconds.
[0016]
In this reaction vessel 2, rectifying plates 7 a and 7 b are provided between the front chamber 21 and the reaction chamber 22 and between the reaction chamber 22 and the rear chamber 23. The rectifying plates 7a and 7b are not necessarily provided. However, if the rectifying plates 7a and 7b are provided, it is possible to prevent the turbulent flow from occurring in the reaction chamber 22 and the rear chamber 23, and the flow velocity in the cross-sectional direction The variation can be suppressed. Further, when the rectifying plates 7a and 7b are installed, the rectifying plates 7a and 7b can be used as a part of the plasma generator by connecting at least one of the rectifying plates 7a and 7b to the control unit 6. Thereby, the volume of the reaction container 2 can be utilized more effectively.
[0017]
The reaction vessel 2 can be provided with a heater (not shown) for heating the atmosphere in the reaction chamber 22. By providing the heater, it is possible to promote the decomposition reaction caused by the plasma described later.
[0018]
When this particle deposition layer forming apparatus 1 is used, for example, a particle deposition layer can be formed by the following method. Here, as an example, the case where the particles to be deposited are FePt particles that can be used as a magnetic catalyst or the like will be described.
[0019]
First, the carrier gas stored in a carrier gas tank (not shown) is supplied to the front chamber 21 of the reaction vessel 2 through the gas supply port 24. As a result, an air flow is generated from the gas supply port 24 to the cooler 8 via the front chamber 21, the reaction chamber 22, the rear chamber 23, and the exhaust port 25. At the same time, the temperature in the reaction chamber 22 is raised to about 600 ° C. to 700 ° C. by a heater (not shown). As the carrier gas, for example, argon, helium, xenon, nitrogen, hydrogen, and the like can be used.
[0020]
Next, the source gas stored in the source gas tank (not shown) is supplied to the front chamber 21 of the reaction vessel 2 through the source gas supply port 24. At this time, for example, the atmospheric pressure in the reaction vessel 2 is set to 1 torr, and the temperature of the source gas is set to about room temperature. Here, for example, (C ₅ H ₅ ) ₂ Fe (ferrocene) and CH ₃ C ₅ H ₄ (CH ₃ ) ₃ Pt ((methylcyclopentadienyl) trimethylplatinum) are used as the source gas. .
[0021]
At substantially the same time as the supply of the source gas, the plasma generator 5 is operated to generate plasma in the reaction chamber 22. At the same time, the controller 6 controls the operation of the plasma generator 5 so that the generation and extinction of plasma are alternately and repeatedly switched.
[0022]
When plasma is generated in the reaction chamber 22, for example, a decomposition reaction represented by the following reaction formula occurs in a region excited by plasma discharge (hereinafter referred to as a reaction region).
Iron raw material → iron atom + product gas Platinum raw material → platinum atom + product gas By such a reaction, iron atoms and platinum atoms as particle materials and a product gas as a decomposition by-product are generated. The generated gas is exhausted from the exhaust port 25 together with the carrier gas and cooled by the cooler 8.
[0023]
The produced iron atoms and platinum atoms collide with each other to form FePt particles. In the plasma discharge space, these particles are instantaneously negatively charged, and the charged particles are trapped in the plasma electric field. That is, it is trapped in the reaction region. Therefore, iron atoms and platinum atoms generated by decomposition of the source gas are further deposited on the particles trapped in the reaction region. Since this growth proceeds isotropically, almost spherical particles are obtained.
[0024]
When the plasma in the reaction chamber 22 is extinguished by the control unit 6, the electric field that has captured the charged particles disappears or weakens. Therefore, the FePt particles generated and grown in the reaction chamber 22 are moved toward the downstream by the air flow formed by the carrier gas, and are deposited on the substrate 4.
[0025]
By alternately and repeatedly generating and extinguishing the plasma as described above, a deposited layer of FePt particles can be formed on the substrate 4.
[0026]
According to the above-described method, it is possible to suppress variation in the particle size of particles contained in the deposited layer by sufficiently shortening the time during which plasma is generated. This is considered to be due to the following reasons.
[0027]
FIG. 2 is a graph showing an example of the particle size distribution in the particle deposition layer obtained by the method according to the first embodiment of the present invention. In the figure, curve 101 shows data obtained when plasma generation and extinction are alternately and repeatedly performed, and curve 102 shows data obtained when plasma is continuously generated.
[0028]
As described above, while plasma is generated in the reaction chamber 22, particle generation and growth occur in the reaction region. The particle size of the particles increases as the time during which they stay in the reaction region (hereinafter referred to as stay time) is longer.
[0029]
As described above, since an air flow is formed in the reaction vessel 2 by the carrier gas or the like, the particles generated in the reaction chamber 22 receive a force directed from the front chamber 21 side to the rear chamber 23 side. Further, the particles generated in the reaction chamber 22 try to stay in the reaction region due to the electric field generated when the plasma is generated.
[0030]
Therefore, when plasma is continuously generated in the reaction chamber 22, the residence time of the particles is affected by the air current and the electric field. Therefore, when plasma is continuously generated in the reaction chamber 22, it is extremely difficult to make the residence time of each particle almost constant, and as shown by a curve 102 in FIG. Variations in particle size cannot be suppressed.
[0031]
On the other hand, if the time during which plasma is generated is sufficiently shortened, the influence of the trapping by the electric field on the residence time can be reduced. That is, the residence time of each particle can be made to substantially coincide with the time during which plasma is generated. Therefore, as shown by the curve 101 in FIG. 2, it is possible to suppress the variation in the particle size of the particles contained in the deposited layer.
[0032]
In the present embodiment, the time t _ON during which plasma is generated in the reaction chamber 22 is set shorter than the time t _c (= V / F) calculated by dividing the volume V of the reaction region by the gas flow rate F. It is desirable to do. In this case, the influence of the capture by the electric field on the stay time can be almost completely eliminated. Therefore, the particle sizes of the particles contained in the deposited layer can be made extremely high. However, the time t _ON may be longer than the time t _c . For example, if the time t _ON is three times or less than the time t _c , the variation in the particle size of the particles contained in the deposited layer can be sufficiently suppressed.
[0033]
As described above, according to the present embodiment, particles having a relatively uniform particle size can be generated in the reaction chamber 22, so that particle classification is not necessary. Therefore, it is not necessary to collect the particles, and the particles generated in the reaction chamber 22 can be directly deposited on the substrate 4 disposed in the rear chamber 23 as shown in FIG. Therefore, it is not necessary to prepare a dispersion of classified particles or to apply the dispersion. That is, according to the present embodiment, a particle deposition layer having a uniform particle size can be formed with a relatively small number of steps, and therefore the cost required for forming the particle deposition layer can be reduced.
[0034]
In the present embodiment, it is desirable that the substrate 4 is sufficiently separated from the reaction region so that the generated particles are deposited on the substrate 4 while maintaining the form as the particles. Usually, if the substrate 4 is separated from the reaction region by the same length as the length of the plasma generation region (for example, 10 mm or more), the generated particles can be deposited on the substrate 4 while maintaining the form as the particles.
[0035]
Next, a second embodiment of the present invention will be described.
FIG. 3 is a diagram schematically showing a particle deposition layer forming apparatus according to the second embodiment of the present invention. The particle deposited layer forming apparatus 1 shown in FIG. 3 has the same structure as the particle deposited layer forming apparatus 1 shown in FIG.
[0036]
The charging processing device 9 includes a casing 91 and defines a charging processing chamber therein. In this charging processing chamber, a holder 93 that detachably holds the substrate 4 and a charging processing apparatus main body 92 are disposed so as to face each other. The main body 92 of the charging processing unit charges the surface of the substrate 4 positively and / or negatively by, for example, a contact method or glow discharge. The charge processing chamber of the charge processing device 9 is connected to the rear chamber 23 of the reaction vessel 2 through a transport path, and is partitioned by a door that can be opened and closed.
[0037]
When this particle deposition layer forming apparatus 1 is used, for example, a particle deposition layer can be formed by the following method. Here, as an example, the case where the particles to be deposited are FePt particles will be described.
[0038]
First, the surface of the substrate 4 is charged positively and / or negatively by the charging device 9. If the surface of the substrate 4 is charged in the opposite direction to the charged polarity of the particles generated in the reaction chamber 22 later, the particles can be efficiently deposited on the substrate 4. Further, if the surface of the substrate 4 is partially charged to the same polarity as the charged polarity of the particles generated in the reaction chamber 22 later, it is possible to suppress the deposition of particles on that portion. Therefore, if the distribution of the charged state is formed on the surface of the substrate 4, the particle deposition layer can be formed in a pattern corresponding to the distribution.
[0039]
Such a distribution of the charged state can be generated, for example, by previously forming regions of different materials on the surface of the substrate when glow discharge is used. In addition, in the case of charging by a contact method, such a distribution of the charged state may be, for example, by previously forming regions with different materials on the surface of the substrate or forming irregularities on the surface of the substrate. Alternatively, a region where the materials are different from each other is formed in advance on the contact surface with the substrate 4 of the charge processing apparatus main body 92, or unevenness is formed on the contact surface with the substrate 4 of the charge processing apparatus main body 92. Can be generated. Here, a silicon substrate having a silicon oxide film pattern formed on the surface is used as the substrate 4 and is charged by glow discharge to form a distribution of charged states on the surface of the substrate 4.
[0040]
Next, the substrate 4 subjected to the charging process as described above is transported from the holder 93 in the charging process chamber to the holder 3 in the rear chamber 23 via the transport path, and is held by the holder 3. Here, only the substrate 4 is moved between the charging chamber and the rear chamber 23, but the substrate 4 may be moved for each holder 93.
[0041]
After closing the door between the charging chamber and the rear chamber 23, a process similar to that described in the first embodiment is performed. That is, the deposition layer of FePt particles is formed on the substrate 4 by alternately and repeatedly generating and extinguishing the plasma.
[0042]
As described above, since the distribution of the charged state is previously formed on the surface of the substrate 4 prior to this process, the particle deposition layer is formed in a pattern corresponding to the distribution of the charged state. As described above, according to the present embodiment, in addition to obtaining the effects described in the first embodiment, it is possible to deposit particles more efficiently and deposit particles in a desired pattern. Become.
[0043]
In the present embodiment, after forming the particle deposition layer, a plasma discharge may be generated between the substrate 4 and the charge processing device 9 to form a protective film on the particle deposition layer. At this time, the adhesion between the particle deposition layer and the protective film may be improved by heating the substrate.
[0044]
In the first and second embodiments described above, FePt particles are generated using a raw material gas containing a compound containing Fe and a compound containing Pt. However, the composition of the generated particles is limited to FePt. It is not something that can be done. That is, various materials can be used as the source gas. For example, the source gas may contain platinum and at least one element selected from the group consisting of iron, cobalt, and chromium. The source gas includes, for example, a compound containing iron, a compound containing platinum, or a compound containing iron and platinum, and copper, silver, tin, antimony, lead, gallium, mercury, molybdenum, and tungsten. And a compound containing at least one element selected from the group. In the first and second embodiments, the decomposition products of a plurality of types of compounds are reacted to generate particles, but the particles may be generated from the decomposition products of one type of compound.
[0045]
In the first and second embodiments, at least one of the rectifying plates 7a and 7b may be made of a conductive material and a voltage may be applied. For example, when the particles are grown, the particles can be prevented from moving from the reaction chamber 22 to the rear chamber 23 by applying a voltage having the same polarity as the charged polarity of the particles to the rectifying plate 7b. . Further, when the particles are deposited on the substrate 4, for example, the particles move from the reaction chamber 22 to the rear chamber 23 by applying a voltage having the same polarity as the charged polarity of the particles to the rectifying plate 7a. Can be promoted.
[0046]
In the first and second embodiments, the particles generated in the reaction chamber 22 may be deposited on the substrate 4 after mass separation. For example, when removing particles having a large particle size from particles generated in the reaction chamber 22, the particles having a large particle size are dropped to the bottom of the reaction vessel 2 in the process of moving from the reaction chamber 22 to the rear chamber 23. May be. At this time, for example, the falling of large particles may be promoted by increasing the distance from the reaction region to the substrate 4 or designing the shape of the rectifying plate 7b so that the particles easily collide. In this case, the reaction vessel 2 may be provided with a structure for collecting the dropped large particles.
[0047]
In the first and second embodiments, when particles are generated in the reaction chamber 22, an etching gas for etching the particle surface may be supplied into the reaction chamber 22 together with a raw material gas and a carrier gas. In this case, it can suppress that the particle size of particle | grain becomes large too much.
[0048]
In the first and second embodiments, a window may be provided in the reaction vessel 2 and a light source such as an ultraviolet lamp may be disposed outside the reaction vessel. In this case, the chemical reaction can be promoted by exciting the source gas by irradiating light from the previous light source.
[0049]
【The invention's effect】
As described above, according to the present invention, there are provided a particle deposition layer forming apparatus and a particle deposition layer forming method capable of forming a particle deposition layer having a uniform particle diameter with a relatively small number of steps.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a particle deposition layer forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a graph showing an example of a particle size distribution in a particle deposition layer obtained by the method according to the first embodiment of the present invention.
FIG. 3 is a diagram schematically showing a particle deposition layer forming apparatus according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Particle deposition layer forming apparatus, 2 ... Reaction container, 3 ... Holder, 4 ... Substrate, 5 ... Plasma generator, 6 ... Control part, 7a ... Current plate, 7b ... Current plate, 8 ... Cooler, 9 ... Charging process Apparatus, 21 ... Front chamber 21, 22 ... Reaction chamber 22, 23 ... Rear chamber, 24 ... Raw material gas supply port, 25 ... Exhaust port, 91 ... Housing, 93 ... Holder, 92 ... Charge treatment device main body, 101 ... Curve 102 ... curve.

Claims (6)

A reaction chamber to which a source gas is supplied;
A rear chamber provided with an exhaust port;
A holder disposed in the rear chamber and capable of holding a substrate;
A plasma generator for generating plasma in the reaction chamber;
A control unit for controlling the operation of the plasma generator so that generation and extinction of the plasma are alternately and repeatedly switched while holding the substrate in the holder;
A particle deposition layer forming apparatus, wherein particles are generated by reacting the source gas, and the particles are deposited on the substrate while maintaining the shape of the particles. While supplying the source gas to the reaction chamber and exhausting from the rear chamber located downstream of the reaction chamber, plasma is generated in the reaction chamber to grow particles as reaction products of the source gas in the plasma Process,
Depositing the particles grown in the plasma by extinguishing the plasma on a substrate disposed in the back chamber;
A method for forming a particle deposited layer, wherein the growing step and the depositing step are alternately and repeatedly performed, and the particles are deposited on the substrate while maintaining the shape of the particles. The time t _ON during which the plasma is generated is set shorter than the time t _c calculated by dividing the volume V of the region in the reaction chamber where the plasma is formed by the flow rate F of the gas flowing through the reaction chamber. The method for forming a particle deposited layer according to claim 2. 4. The particle deposition layer forming method according to claim 2, further comprising a step of performing a charging process on the substrate prior to the growing step and the depositing step. 5. The particle deposition layer formation according to claim 2, wherein in the deposition step, the particles supplied from the reaction chamber are mass-separated and deposited on the substrate. Method. 6. The particle deposition layer forming method according to claim 2, wherein the growing step is performed while supplying an etching gas for etching the particles into the reaction chamber.

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