KR102545659B1 - Diamond synthesis method by plasma cvd - Google Patents

Abstract

The present invention relates to a method for growing diamond in a large area and at high speed without defects by plasma CVD. The diamond synthesis method is characterized in that the flow rate and plasma activation for each of hydrocarbon and hydrogen are independently controlled, and the supply flow rate for each hydrocarbon and hydrogen has a predetermined cyclic pattern in a unit of process time. According to this plasma CVD, while independently performing a plasma activation process for each of a plurality of reaction gases, while performing a flow rate in a process time unit for each of a plurality of reaction gases in a predetermined cyclic pattern, related to diamond formation By independently controlling the power and ratio of reactive species in units of processing time, it is possible to simultaneously satisfy the demands for high quality and high-speed growth during diamond synthesis, which were previously difficult to coexist with.

Description

Diamond synthesis method by plasma CVD {DIAMOND SYNTHESIS METHOD BY PLASMA CVD}

The present invention relates to a method for synthesizing diamond, and more particularly, to a method for growing defect-free, large-area, high-speed diamond by plasma CVD.

Diamond's electrical, thermal, mechanical, and optical properties are at the highest level among materials, and its performance index as a power semiconductor material is known to be superior to those of Si, SiC, and GaN. In addition, since diamond has excellent optical properties, thermal properties, and mechanical properties, it is expected to be applied in various fields such as mechanical tools and jewelry, including electronic engineering fields including power semiconductors.

As a conventional method of synthesizing diamond, CVD (Chemical Vapor Deposition: Chemical Vapor Deposition) plasma processing using hot filament (HT), direct current (DC), microwave (MW), etc. according to the type of excitation source ) law is known. Plasma CVD is a method of growing diamond on a substrate by generating a mixed plasma of hydrogen and methane and using the decomposition and synthesis of gaseous molecules by electrons, ions, and radical reactive species in the plasma. In order to do this, a mixed gas of hydrocarbon gas such as methane and hydrogen gas is supplied as a raw material gas for generating plasma and reactive species, and generally, the smaller the ratio of hydrocarbons in the mixed gas, that is, the higher the dilution ratio, the better the quality of synthetic diamond. It is known that diamond is synthesized by CVD in a small area, usually less than 5% (EP 2 656 370 B1).

In this case, methane gas is mainly used as a carbon source, but there are many cases in which other types of carbon-containing gases are used as raw material gases. In either case, in a CVD process capable of growing diamond, atomic hydrogen must be produced to participate in the diamond-forming surface reaction. In particular, hydrogen gas among mixed gases is known to play the following important roles in the diamond growth process. That is, hydrogen is converted into atomic hydrogen by being activated by plasma, and this atomic hydrogen diffuses into the substrate to help C-H species find their place, and also to form secondary phases other than diamond such as graphite, nanocrystals or polycrystals. It serves to ensure that defects are not included in the growing diamond by selectively etch-reducing.

On the other hand, in the case of the conventional diamond synthesis method using plasma CVD, hydrogen gas and a mixed gas of the hydrogen gas are introduced into the reaction chamber through a single supply line, and the mixed gas is introduced into the upper space of the substrate disposed in the chamber using a single excitation source. Diamond growth is induced by converting into plasma at the same location to generate C-H and atomic H reactant species, and these reactive species diffuse to the upper surface of the substrate.

However, since this conventional plasma CVD method adopts a simple method of simultaneously converting a source reaction gas diluted with a hydrocarbon such as methane into plasma using a single excitation source, the gas ratio for each reaction type involved in the reaction is the plasma formation temperature and It is uniformly determined according to the pressure conditions and the flow rate of the mixed gas and cannot be independently controlled, and other process variables that can be independently controlled are extremely limited. Accordingly, there is a problem in that the degree of freedom in selection of various process conditions required according to the purpose of diamond growth, use, and individual demand, as well as high quality and high-speed growth of diamond, is significantly reduced.

For example, in order to improve the growth rate of synthetic diamond and reduce defects formed in diamond grown by the plasma CVD method to secure the economic feasibility of synthetic diamond, the above, which is one of the causes of defects without reducing the growth rate of diamond It is necessary to intensify the etching process for removing one secondary phase from the diamond surface during film formation. That is, the supply of carbon must be increased for high-speed deposition of diamond and the supply of hydrogen to etch and remove the secondary phase formed on the surface and included inside must be increased to reduce defects. Since the reactive species related to can not be independently controlled, it is not possible to simultaneously satisfy the requirements of high-speed growth (high carbon source concentration) and defect-free (high hydrogen concentration), which are compatible with each other as a trade-off.

In addition, the diamond thin film grown by plasma CVD is a meta-stable phase and has a difference from the bond length or angle of the ideal diamond crystal lattice, and this difference exists as residual stress in synthetic diamond and grows to a predetermined thickness When the yield strength of the diamond is exceeded, micro-cracks are caused inside, thereby acting as another defect for the synthetic diamond apart from the above-mentioned secondary phase, thereby deteriorating the optical, electrical and mechanical properties. Therefore, in order to prevent this, it is necessary to artificially relieve the residual stress by forming a growth layer having residual stress in the opposite direction to the growth layer having residual stress in a certain direction. Since it is related to, in order to form high-quality diamond, selective and independent control of the carbon concentration in units of processing time is required, but there is a limitation that the conventional plasma CVD process cannot implement this.

EP 2 656 370 B1

The present invention reflects the problems of the prior art described above, and provides a method for synthesizing diamond by plasma CVD of a new process concept, which can simultaneously satisfy the requirements for high-speed growth and high quality, which were compatible with each other during diamond synthesis.

In the process of researching and developing a diamond synthesis method by plasma CVD related to the above problem, the present inventors independently perform a plasma activation process for each of a plurality of reaction gases, while in a process time unit for each of a plurality of reaction gases When the flow rate of is performed in a predetermined cyclic pattern, the present invention has been reached by discovering that it is possible to simultaneously satisfy the requirements for high quality and high-speed growth, which were difficult to achieve in a conventional plasma CVD process. The gist of the present invention based on the recognition and knowledge related to the above problems is the same as the following content described in the claims.

(1) A method for synthesizing diamond performed by supplying a plurality of reaction gases containing hydrocarbons and hydrogen, and performing chemical vapor deposition on a substrate using plasma generated by exciting the plurality of reaction gases, wherein the hydrocarbon and a flow rate of hydrogen and plasma activation are independently controlled, and the supply flow rate of each of the hydrocarbon and hydrogen has a predetermined cyclic pattern in a unit of processing time.

(2) The method of synthesizing diamond by plasma CVD of (1), characterized in that the hydrogen is alternately and continuously supplied at flow rates of upper and lower limits set in advance in processing time units.

(3) The method of synthesizing diamond by plasma CVD of (2), characterized in that the hydrocarbon is continuously supplied at a constant flow rate in units of processing time.

(4) The diamond synthesis method by plasma CVD of (2), characterized in that the hydrocarbon is supplied only when the hydrogen is supplied at the lower limit flow rate in the unit of processing time, but is supplied alternately at the upper and lower limit flow rates set in advance.

(5) The diamond synthesis method by plasma CVD of (2) above, characterized in that the time during which the hydrogen is supplied at the lower limit flow rate is longer than the time during which the hydrogen is supplied at the upper limit flow rate.

(6) The supply of dopant gas and plasma activation are additionally performed, but the supply of dopant gas and plasma activation are performed only while the hydrocarbon is supplied. Diamond synthesis by plasma CVD of (1) above. method.

(7) Diamond synthesis by plasma CVD of (1), characterized in that the excitation source of the plasma CVD is any one of hot filament, DC, microwave, RF (Radio Frequency), Laser Assisted, and Photo Assisted method.

(8) The method of synthesizing diamond by plasma CVD of (1), characterized in that it includes at least one pre-activation step for the reaction gas before activating with plasma.

According to the method for synthesizing diamond by plasma CVD of the present invention, the plasma activation process for each of a plurality of reaction gases is independently performed, while the flow rate in the unit of process time for each of the plurality of reaction gases is performed in a predetermined cyclic pattern By independently controlling the power and ratio of the reactive species related to diamond formation in a process time unit in a way to do so, it is possible to simultaneously satisfy the demands of high quality and high-speed growth during diamond synthesis, which have been difficult to coexist in the past. In addition, as a result, the freedom to select various process conditions required according to the purpose of diamond growth, use, and individual demand, as well as high quality and high-speed growth of diamonds, can be excellent.

1 is a longitudinal cross-sectional structural diagram of a plasma CVD apparatus according to an embodiment of the present invention;
2 is a cross-sectional structural diagram of a plasma CVD device according to an embodiment of the present invention.
3 and 4 are graphs showing hydrogen flow patterns according to embodiments of the present invention.
5 and 6 are graphs showing hydrocarbon flow patterns according to embodiments of the present invention.
7 is a graph showing a dopant gas flow pattern according to an embodiment of the present invention.
8 and 9 show hydrogen according to embodiments of the present invention; And a mixed gas of hydrogen and methane; a graph showing a flow pattern for the case of supplying a separate reaction gas group.

Hereinafter, preferred embodiments of the present invention will be described in detail. In describing the present invention, if it is determined that a detailed description of related known technologies may obscure the gist of the present invention, the detailed description will be omitted. Throughout the specification, when a part "includes" a certain component, it means that it may further include other components, not excluding other components, unless otherwise stated.

Diamond synthesis according to the present invention is basically performed by plasma CVD, and in particular, in order to simultaneously satisfy mutually compatible requirements for high-speed growth and high quality, the flow rate and activation in the unit of process time for each of a plurality of reaction gases for plasma CVD It is characterized in that it is independently controlled and performed in a predetermined cyclic pattern at the same time. Hereinafter, an embodiment of the device concept for independent control of the flow rate and activation and an embodiment of the cyclic pattern will be sequentially described.

Plasma CVD device

First, an embodiment of the concept of the plasma CVD apparatus 10 for independently controlling the flow rate and activation of the reaction gas will be described. 1 and 2 show a longitudinal and cross-sectional structural diagram of a plasma CVD apparatus 10 in which a reaction gas flow rate and activation can be independently controlled in a process time unit according to an embodiment of the present invention. In the present invention, the plasma CVD excitation source may be formed in various forms such as a hot filament, DC, microwave, RF (Radio Frequency), Laser Assisted, and Photo Assisted, and the plasma CVD device according to the drawing uses microwave as an excitation source. A microwave plasma CVD apparatus (hereinafter referred to as 'CVD apparatus') was taken as an example. However, regardless of the embodiment, the inventive concept of independent control of flow rate and activation in a process time unit for each of a plurality of reaction gases described below can be equally applied to a plasma CVD device using a different type of excitation source. there is.

1 and 2, the CVD device 10 is basically a device 10 for synthesizing diamond, and includes a substantially tubular reaction chamber 100; and a microwave plasma 40A in the reaction chamber 100. 40B); and a gas supply line 100A, 110B for supplying the plurality of reaction gases and plasmas 40A, 40B in the reaction chamber 100. The microwave oscillators 200A and 200B for forming are provided separately for each of a plurality of reaction gases. Accordingly, since the plasmas 40A and 40B for each reaction gas are separately formed, various process variables including the relative ratio of reactive species activated by the plasmas 40A and 40B can be independently controlled.

This CVD apparatus 10 schematically supplies a plurality of reaction gases containing hydrocarbons and hydrogen to the reaction chamber 100 in which the substrate 50 is placed, and at the same time introduces microwaves into the reaction chamber 100 to The plurality of reaction gases are excited to generate plasmas 40A and 40B, and diamond synthesis is performed on the substrate 50. Components of the plurality of reaction gases include hydrocarbons and hydrogen for diamond synthesis, and in the case of the embodiment, pure hydrogen gas as a specific method of supplying these reaction gas components; A mixed gas of hydrogen and hydrocarbon gas; may be supplied by separating the reaction gas group. As the hydrocarbon, methane may be mainly used, but is not limited thereto, and the concentration of the hydrocarbon in the mixed gas may be diluted to 5% or less.

A susceptor 120 for horizontally supporting a substrate 50 on which diamonds are to be grown is provided in the chamber 100, and the susceptor 120 can be rotated by an external power mechanism (not shown). . An exhaust port 130 is provided at the bottom of the chamber 100, and an external exhaust device including a vacuum pump is connected to the exhaust port 130. A microwave introduction window 140 is provided in the upper part of the chamber 100, and gas supply lines 100A and 110B for a plurality of reaction gas groups involved in diamond synthesis are separately provided for each reaction gas group from the upper side of the chamber 100 do. In this case, each reaction gas flow rate through the gas supply lines 100A and 110B is independently controlled in a process time unit.

Above the chamber 100, microwave oscillators 200A and 200B are provided as excitation sources used to form the microwave plasma 40A and 40B in the reaction chamber 100. It is provided separately for each reaction gas group supplied through the gas supply lines 100A and 110B. Each of the plurality of microwave oscillators 200A and 200B is provided in a set form including a waveguide 210 and a tuner 220 . As shown in FIG. 2, each waveguide 210 may be installed in a form crossing the upper central portion of the reaction chamber 100, and each microwave transmitted through the waveguide 210 is transmitted to each antenna. It is guided by the microwave 230 and introduced into the space within the chamber 100 through the microwave introduction window 140 made of quartz. Each antenna 230 is installed where each reaction gas is introduced into the chamber 100 through the gas supply lines 100A and 110B. In this case, the positions where the plasmas 40A and 40B are formed for each reaction gas by the introduced microwaves are different, and in FIGS. 1 and 2, these ball-shaped plasmas 40A and 40B are simplified for understanding. It is shown diagrammatically. A shielding wall 60 may be provided between the waveguides 210 of each of the plurality of microwave oscillators 200A and 200B to prevent interference between microwaves.

In the case of the CVD apparatus 10, regardless of whether a mixed gas or a pure gas is used, in order to separate the hydrogen and carbon source gas and independently set the process conditions, the gas supply lines 100A and 110B It is important to activate process gas from the separated gas supply lines 100A and 110B as independent plasmas 40A and 40B, respectively, along with separating the . By doing this, it is possible to independently set and control the power of the plasmas 40A and 40B and the flow rate of the gas in a pressure state determined by sharing the same susceptor 120 in the same reaction chamber 100 .

Optionally, when synthesizing diamond using the CVD device 10, one or more preliminary activation means and steps performed before plasma activation may be further included. This preliminary activation step means that energy is applied at a level before a full-fledged decomposition reaction of the reaction gas occurs, rather than activation at the level of decomposing the reaction gas. Conventionally, this preliminary activation step can be performed in a single step, but in the present invention, it is easier to optimize process conditions by implementing various activation methods for the reaction gas by combining these preliminary activation steps in multiple steps according to process conditions or purposes. can be achieved effectively.

For example, in the first step preliminary activation step (S1), heating tape (not shown) is wound around the gas supply line to apply heat to increase the temperature of the reaction gas, or in the second step preliminary activation step (S2) In the range where the decomposition reaction of the reaction gas does not occur by installing an activation device (not shown) such as a DC arc or RF plasma, the process gases are individually activated under different conditions, and the third stage preliminary In the activation step (S3), process gases may be preliminarily activated before entering the reaction chamber with a CO ₂ Continuous Wave (CW) Laser (not shown). Through such one or more preliminary activation steps, by preliminary activating the reaction gas for the process, activation energy of chemical species required for diamond growth can be obtained without increasing the plasma power in the reaction chamber 100, and in the reaction chamber 100 When the plasma power is lowered, not only can the equipment price be lowered, but also the advantage of improving the life span of the power supply can be obtained when plasma is generated at the existing high power. In addition, by generating plasma with low power, there is an advantage in equipment flexibility, such as obtaining a side effect outside the process of increasing equipment up time due to less damage to the microwave introduction window 140 and the like. Meanwhile, the combination of the above-described preliminary activation device and method may be combined with various methods depending on the type of reaction gas for process and the purpose of the process, and is not limited to the present embodiment.

On the other hand, in the above-described embodiment, the group of reaction gases is pure hydrogen gas; Although illustrated as two mixed gases of hydrocarbon and hydrogen, these reactant gas groups can be added as needed to achieve other desired properties for diamond. For example, when it is necessary to inject dopants into a synthesized diamond, a dopant gas selected from PH ₃ , BH ₃ , B ₂ H ₆ , and the like may be added as a reaction gas group. In this case, of course, a gas supply line (not shown) and a microwave generator (not shown) as an excitation unit may be separately provided for the dopant gas group to be added.

Embodiments Regarding Reactant Gas Flow Patterns

Next, various flow patterns related to the reaction gas flow rate that can be implemented using the plasma CVD apparatus 10 according to the embodiment of FIGS. 1 and 2 will be described. Basically, this flow pattern is characterized by having a cyclic pattern in a process time unit of a certain period, and each pattern can be described by the flow rate and supply time of the corresponding reaction gas.

3 and 4 are graphs showing hydrogen flow patterns according to embodiments of the present invention.

The flow pattern according to the embodiment of FIG. 3 relates to hydrogen among the reaction gases, and in this case, hydrogen is alternately and continuously supplied at flow rates of upper and lower limits preset in the unit of process time, and the holding time for each flow rate ( supply time) is of the same form. As the flow rate and supply time of hydrogen involved in the diamond synthesis process are adjusted according to this flow pattern, the amount of plasma-activated atomic hydrogen can be controlled in units of process time. Specifically, when a large amount of atomic hydrogen is required for etching or surface treatment, a large amount of hydrogen is supplied at an upper limit flow rate, and in a film formation step following etching or surface treatment, hydrogen is supplied at a lower limit flow rate.

The flow pattern according to the embodiment of FIG. 4 also relates to hydrogen among the reaction gases. In this case, hydrogen is alternately and continuously supplied at the flow rate of the upper and lower limits preset in the process time unit, as in FIG. 3, but Unlike , the time supplied at the lower limit flow rate is longer than the time supplied at the upper limit flow rate. In FIG. 4 , the purpose of adjusting the upper and lower limit flow rates of hydrogen is basically the same as that of FIG. 3 . In the case of FIG. 4 , the overall film formation speed is increased by extending the time during which the flow rate is maintained at the lower limit in the film formation step after the etching resistance surface treatment. 4 differs from FIG. 3 in that the film formation time by the mixed gas of hydrocarbons and hydrogen is increased compared to the cycle time by the hydrogen plasma. In the film formation step of flowing the mixed gas, by adjusting the flow rate small when film formation is performed for a long time, the film formation speed is reduced to minimize the formation of secondary phases that may be formed during film formation, thereby reducing the concentration of crystal defects that may be incorporated into diamond. represents the process. On the other hand, if the flow rate of the mixed gas increases, the growth rate increases, but since crystal defects can relatively increase inside the diamond, the flow pattern of FIG. 4 can be applied as a gas flow pattern that can be used in mass production of low-quality diamonds .

5 and 6 are graphs showing hydrocarbon flow patterns according to embodiments of the present invention.

The flow pattern according to the embodiment of FIG. 5 relates to hydrocarbons in the reaction gas, and the hydrocarbons are continuously supplied at a constant flow rate in units of process time. In the hydrocarbon flow pattern of FIG. 5, the hydrogen flow pattern (FIG. 5(a)) overlaid in the corresponding process time unit was scheduled for FIG. At this time, the amount of the activated carbon (C-H species) source on the surface where the diamond grows is mainly determined by the flow rate of the carbon source gas. On the other hand, the effect of etching the secondary phase by atomic hydrogen increases in a portion where the hydrogen flow rate is kept high as an upper limit, thereby reducing defects compared to the conventional case of forming a film using only a hydrogen-diluted hydrocarbon source gas. In addition, the flow rate and supply time of hydrogen may be varied according to the required quality level of diamond, that is, the level of crystal defects in the diamond, and the flow rate of hydrocarbon supplied may be adjusted according to the required productivity of diamond. As a result, when the flow rate and supply time of hydrogen and hydrocarbons are adjusted according to the flow pattern of FIG. 5, it is possible to adjust the relative concentrations of hydrogen and hydrocarbons involved according to the nature of each process step of etching and film formation. As a result, the concentration and efficiency of each process step of etching and film formation can be improved in the unit of process time, and accordingly, the effect of quality improvement by etching and high-speed growth of diamond can be realized at the same time.

The flow pattern according to the embodiment of FIG. 6 also relates to hydrocarbons in the reaction gas, and hydrocarbons are discontinuously supplied at upper and lower flow rates in a process time unit. In the hydrocarbon flow pattern of FIG. 6, the hydrogen flow pattern (FIG. 6(a)) overlaid in the corresponding process time unit was scheduled for FIG. 3 as in FIG. If the hydrocarbon flow pattern of FIG. 6 is explained in more detail in conjunction with the hydrogen flow pattern of FIG. 3, the hydrocarbon is performed only when hydrogen is supplied at the lower limit flow rate in the process time unit, but is supplied alternately at the preset upper and lower limit flow rates. It is a form. Adjusting the flow rate and congestion time of hydrocarbons including hydrogen according to the flow pattern of FIG. 6 will be examined from the viewpoint of film formation and treatment on the surface thereof. Referring to (b) of FIG. 6, first, a process for facilitating nucleation on the surface of a growing substrate using an excess hydrogen plasma is performed, and a mixed gas of hydrocarbons and hydrogen according to (b) of FIG. Cyclic diamond growth in which compressive stress and tensile stress are alternately induced is repeated by controlling the flow rate. That is, compressive stress occurs in a diamond thin film grown slowly by lowering the C-H concentration to a preset lower flow rate value, and conversely, tensile stress occurs in a diamond thin film grown quickly by increasing the C-H concentration to a preset upper limit flow rate value. By alternately performing these film formation processes, if the directionality of the residual stress in the diamond is offset from each other, even if the diamond grows thick, the possibility of defects due to the residual stress in the thin film or bulk is minimized and high quality can be maintained. On the other hand, in the flow pattern of FIG. 6, as in the flow pattern of FIG. 5, it is possible to adjust the relative concentrations of hydrogen and hydrocarbons involved according to the nature of each process step of etching and film formation, so that the corresponding It goes without saying that high-speed growth and high-quality (removal of defects by etching) effects can be achieved by improving the concentration and efficiency of each process step of etching and film formation.

7 is a graph showing a dopant gas flow pattern according to an embodiment of the present invention. As described above, other types of reactant gases other than hydrogen and hydrocarbons may be added to the synthetic diamond to realize the physical properties of other demands, and FIG. 7 shows PH ₃ , BH ₃ or B ₂ H as other types of reactant gases. A flow pattern is shown in the case where dopant gases such as ₆ are injected. In the dopant gas flow pattern of FIG. 7, the hydrogen and hydrocarbon flow patterns ((a) and (b) of FIG. 7) overlaid in the corresponding process time unit were previously scheduled for FIG. 6. In this case, the dopant gas supply and plasma activation are additionally performed, but the dopant gas supply and plasma activation are performed only while the hydrocarbon is supplied.

The flow pattern including the dopant gas according to FIG. 7 , for example, in the case of doping diamond with impurities and applying it to an electronic device, artificially doping through ion implantation from the outside. Possibility of occurrence of defects in the crystal can be avoided. there can be useful Specifically, according to the flow pattern of FIG. 7, BH ₃ or B ₂ H ₆ containing p-type impurities is independently introduced along with other reaction gases such as hydrogen and methane, activated by plasma, and boron is moved to the diamond surface When activated, BH*-activated boron is adsorbed and diffuses into the diamond surface or inside the diamond bulk through a solid phase diffusion process. In this case, gas containing impurities is uniformly, intermittently, and regularly introduced into the place where the plasma ball is formed. It decomposes and activates impurities such as boron activated by the plasma to diffuse to the surface where the diamond is growing. And, through processes such as adsorption-diffusion-fixation-nucleation-growth on the surface, the in-situ doping reaction is performed while impurities occupy carbon sites in diamond.

8 and 9 are graphs showing flow patterns in the case of supplying a mixed gas of hydrogen for etching, hydrogen for film formation, and methane as separate reaction gas groups according to embodiments of the present invention.

The flow pattern of FIG. 8 is an example of supplying a process gas in a flow pattern close to the gas partial pressure in an actual reaction chamber. First, a cycle for the reaction gas flow rate is started with the step of treating the surface of the diamond substrate with atomic hydrogen by hydrogen plasma to form more diamond nucleation sites with the effect of cleaning the surface of the substrate. Next, while gradually reducing the hydrogen flow rate, the flow rate of methane gas diluted in hydrogen is gradually increased, and when it reaches the maximum value, it is decreased again, and then a series of processes of gradually increasing the hydrogen flow rate are repeated. The flow pattern according to FIG. 8 is effective in suppressing the formation of the second phase that can deteriorate the film formation quality of growing diamond. Although the growth rate of diamond can be slightly reduced, the concentration of crystal defects in diamond can be significantly reduced.

On the other hand, in the flow pattern of FIG. 9, in order to overcome the disadvantage that the growth rate of diamond is lowered in the case of FIG. Indicates a flow pattern.

It can be understood that the cyclic flow pattern accompanying the supply and activation process of the reaction gas according to the embodiments of FIGS. 3 to 9 described above is presented as an applicable representative example, and has independent process gas lines for high-speed growth And for the purpose of synthesizing high-quality diamond, it is possible to satisfy various characteristics required according to the diamond for each use by combining or applying it in various forms based on the presented examples as needed.

As described above, according to the method for synthesizing diamond by plasma CVD of the present invention, the plasma activation process for each of a plurality of reaction gases is independently performed, while the flow rate in the unit of process time for each of the plurality of reaction gases is set to a predetermined cyclic By independently controlling the power and ratio of reactive species related to diamond formation in a process time unit in a patterned manner, it is possible to simultaneously satisfy the demands for high quality and high-speed growth during diamond synthesis, which were previously difficult to coexist. In addition, as a result, the freedom to select various process conditions required according to the purpose of diamond growth, use, and individual demand, as well as high quality and high-speed growth of diamonds, can be excellent.

The above description relates to specific embodiments of the present invention. As described above, the embodiments according to the present invention are disclosed for explanatory purposes and are not to be understood as limiting the scope of the present invention, and those skilled in the art will not deviate from the essence of the present invention. It should be understood that various changes and modifications are possible. Accordingly, all such modifications and changes may be understood to fall within the scope of the invention disclosed in the claims or equivalents thereof.

10: microwave plasma CVD device
100: reaction chamber
110A, 110B: gas supply line
120: susceptor
130: exhaust port
140: microwave introduction window
200A, 200B: microwave oscillator
210: waveguide
220: tuner
230: antenna
40A, 40B: Plasma
50: substrate
S1: first preliminary activation step
S2: Second preliminary activation step
S3: Third preliminary activation step

Claims (8)

A method for synthesizing diamond performed by supplying a plurality of reaction gases containing hydrocarbons and hydrogen, and performing chemical vapor deposition on a substrate using plasma generated by exciting the plurality of reaction gases, wherein the hydrocarbon and hydrogen The flow rate and plasma activation for each are independently controlled, but the supply flow rate for each of the hydrocarbon and hydrogen has a predetermined cyclic pattern in a unit of process time,
The supply of hydrogen in the cyclic pattern includes a first hydrogen supply process in which hydrogen is supplied at a predetermined upper limit flow rate for a first time, and a second hydrogen supply process in which hydrogen is supplied at a predetermined lower limit flow rate for a second time. Consisting of, hydrogen is supplied while the first hydrogen supply process and the second hydrogen supply process are alternately repeated,
In the cyclic pattern, hydrocarbon is supplied only during the second time when the hydrogen is supplied at the lower limit flow rate,
The supply of hydrocarbons is a first hydrocarbon supplying process in which hydrocarbons are supplied at a predetermined lower limit flow rate during any one of the second times during the second hydrogen supplying process, and any one of the second time It consists of a second hydrocarbon supplying process in which hydrocarbons are supplied at a predetermined upper limit flow rate for a neighboring time,
Supply of dopant gas and plasma activation are additionally performed,
The supply of the dopant gas is performed only in the first hydrocarbon supply process and the second hydrocarbon supply process in which the hydrocarbon is supplied,
The supply of the dopant gas includes the first dopant gas supply process in which the dopant gas is supplied at a flow rate of a preset lower limit in the first hydrocarbon supply process, and the dopant gas is supplied at a flow rate of a preset upper limit in the second hydrocarbon supply process. A method for synthesizing diamond by plasma CVD, characterized in that it consists of a second dopant gas supply process. delete According to claim 1,
A method for synthesizing diamond by plasma CVD, comprising a preliminary activation step for the reaction gas in a step before activation with plasma. The method of claim 3, wherein the preliminary activation step,
A first stage preliminary activation step (S1) of increasing the temperature of the reaction gas by applying heat by winding a heating tape around the gas supply line;
A second preliminary activation step (S2) of installing an activation device such as a DC arc or RF plasma to pre-activate the process gases individually under different conditions within a range where the decomposition reaction of the reaction gas does not occur; and
A third preliminary activation step (S3) in which process gases are activated by CO ₂ CW (Continuous Wave) Laser before entering the reaction chamber; including, to obtain activation energy required for diamond growth in advance Method for synthesizing diamond by plasma CVD. delete delete delete delete

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