JP4217522B2 - Diamond film-forming silicon and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to silicon formed from conductive diamond and a method for manufacturing the same.
[0002]
[Prior art]
Diamond is one of the hardest materials known on the earth, and has excellent physical properties such as wear resistance, chemical resistance and pressure resistance. It is a substance that exhibits chemical stability. Familiar products applying this physicochemical stability include many applied products such as glass diamond cutters, drill blades, and grinder blades.
[0003]
Still further, diamond carbon is the same group IV element as silicon. For this reason, when carbon forms a diamond structure (sp3 crystal system), it exhibits semiconductor characteristics similar to silicon, has strong bonding strength between atoms, corresponds to the binding energy of valence electrons, and is as large as about 5.5 eV at room temperature. Have a band gap. Similarly to silicon, a group III element such as boron is used as a dopant to form a p-type semiconductor, and a group V element such as nitrogen or phosphorus is used as a dopant to form an n-type semiconductor. Therefore, applied research on diamond electronic devices is underway (see Non-Patent Document 1). Pure diamond is an excellent insulator, but by adjusting the amount of this dopant, the material can be changed from an insulator to a metal-like conductivity to any conductivity.
[0004]
In recent years, it has begun to be revealed that this diamond has specific electrochemical characteristics in addition to the physicochemical characteristics and semiconductor characteristics. When diamond is used as an electrode, it has been clarified that both oxygen and hydrogen are generated in an aqueous solution only at a large absolute overvoltage value, and thus show a wide thermodynamic window. From the thermodynamic calculation, the hydrogen generation overvoltage is 0V with respect to the hydrogen standard reference electrode (SHE), and the oxygen generation overvoltage is + 1.2V, so the thermodynamic window is 1.2V wide. Depending on the conditions of the electrolyte, this thermodynamic window is 1.6-2.2 V when using a platinum electrode, for example, and about 2.8 V when using a glassy carbon electrode. In the case of a diamond electrode, it is 3.2 to 3.5V. This wide thermodynamic window means that the electrode is unsuitable for generating oxygen and hydrogen, but other reactions can proceed at the electrode. For example, when this diamond electrode is used for wastewater treatment, it is known that chemical oxygen demand (COD) of wastewater can be removed with high efficiency (see Patent Document 1). This is considered that many OH radicals generate | occur | produce on the surface of a diamond electrode, and the mechanism in which this OH radical mineralizes COD component to a carbon dioxide gas etc. is concerned (refer patent document 2). Since many of these OH radicals are generated on the electrode surface, water sterilization methods using diamond electrodes such as for beverages, pools, and cooling buildings are being developed.
[0005]
Furthermore, as a specific electrochemical characteristic of diamond, the background current (residual current) is very low compared to other electrodes. Due to its low background current and wide thermodynamic window, diamond is expected to be used as an electrode for trace sensors of metals and ecosystem substances contained in aqueous solutions.
[0006]
By the way, as a method of producing a diamond electrode by forming a diamond film on a base material, chemical vapor deposition (CVD) is used, and currently, two types of methods, hot filament CVD and microwave plasma CVD, are mainly used. ing. Both of these methods are methods for synthesizing artificial diamond under reduced pressure without applying high pressure.
[0007]
In microwave plasma CVD, plasma is generated by irradiating an organic gas which is carbon source of several hundred ppm to several percent of methane, acetone, and other diamonds with a microwave of about 2.4 GHz in a hydrogen atmosphere. When a substrate maintained at a temperature of 600 to 1000 ° C. is placed in the vicinity of the generated plasma, a tiremond film grows on the substrate. If a boron source such as diborane or boron oxide is mixed in a hydrogen atmosphere in addition to methane gas in order to make the diamond film conductive, a p-type semiconductor diamond film grows. Diamond is mainly formed on a silicon wafer substrate by microwave plasma CVD, and development of applications such as sensors is expected. Since silicon and diamond are the same Group IV elements, the crystal structure is close, and therefore the adhesion of the diamond film to the silicon substrate is said to be good. When diamond is deposited on silicon, a very thin silicon carbide intermediate layer (interlayer) is naturally generated, and the diamond film is brought into close contact with the silicon wafer substrate by this interlayer. It is known that the diamond film produced by the microwave plasma CVD is relatively stable and of high quality (see Patent Document 3).
[0008]
On the other hand, in hot filament CVD, carbon source contains several percent of methane, ethane, propane, butane, unsaturated hydrocarbons such as unsaturated hydrocarbons, alcohols such as ethanol, or ketones such as acetone. When a filament of tungsten, tantalum, ruthenium or the like is heated to about 2000 ° C. in a hydrogen gas atmosphere, a diamond film grows on the substrate installed in the vicinity of the filament. By disposing a long filament on this substrate, a large-area diamond film can be manufactured. For example, 1m ² When the substrate is formed, 20 filaments each having a length of 1 m may be installed on the substrate inserted in the deposition chamber at intervals of 5 cm. Similar to microwave plasma CVD, when a boron source is supplied together with methane or the like, a diamond film grows on a p-type semiconductor. The substrate temperature at this time is maintained at about 800.degree. Since hot filament CVD enables such large-area film formation, a technique for forming a film on a metal substrate without size limitation has been developed (see Patent Document 4).
[0009]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-299467
[Patent Document 2]
JP 2000-254650 A
[Patent Document 3]
Japanese Patent Laid-Open No. 10-167888
[Patent Document 4]
JP-A-9-124395
[Non-Patent Document 1]
Ogushi Hideyo, “Future Materials”, 2002, Vol. 2, No. 10, p. 6-13
[0010]
[Problems to be solved by the invention]
However, many silicon substrates used for diamond electrodes use silicon wafers, and their surface area is extremely small. That is, the mainstream size of silicon wafers currently on the market is 8 inches (200 mm) in diameter, and the largest silicon wafer size is 300 mm in diameter. Therefore, there is a limit to manufacturing a diamond electrode having a large surface area based on silicon. Furthermore, when microwave plasma CVD is used, diamond can be formed on a small substrate of several centimeters square without problems, but when a large-sized substrate, for example, a meter-angle substrate is formed, a diamond film is formed on the entire surface of the substrate. This is very difficult at present. That is, the difficulty in increasing the area is due to the technical difficulty of generating plasma that covers the entire surface of the meter-sized substrate.
[0011]
Furthermore, since the thickness of these silicon wafers is usually about 725 μm or more, even if an attempt is made to produce a large area electrode by bonding a silicon wafer formed with diamond to a conductive support base having a large area, Since the flexibility is low, bonding is not easy, and the conductivity of the silicon wafer has to be lowered due to its thickness, and there is a problem in using it as an electrode.
[0012]
In addition, if single crystal diamond is used for the substrate, diamond having a homoepitaxial structure can be grown by microwave plasma CVD, but the diamond film formed on a silicon wafer is almost always a polycrystalline diamond film. there were.
[0013]
On the other hand, as described above, a technique for forming a film on a metal substrate having no size limitation in hot filament CVD has been developed, and tantalum, niobium, and tungsten are used as the metal substrate.
[0014]
However, the crystal structure of these substrate metals is completely different from the epitaxial crystal structure of diamond. Therefore, in order for diamond to adhere to the metal substrate, a strong interlayer (intermediate layer) for joining the metal and the tiremond is essential. For example, when forming a diamond film on niobium, which is a metal plate, it is necessary to create a niobium carbide interlayer, but this niobium carbide layer is not easily formed like silicon carbide. Before starting, it is necessary to provide a separate step of forming a niobium carbide layer. Such metal carbide film formation conditions are greatly influenced by the pretreatment of the substrate metal, the film formation temperature, and the gas composition conditions, the operation conditions are complicated, and the influence of each operation factor on the metal carbide formed is The current situation is not yet fully understood. And there existed a problem that the quality of diamond layer formed into a film by the state of a metal carbide layer, especially stability (durability) was influenced greatly. Further, even when diamond is directly formed on the metal carbide layer by hot filament CVD, crystallization is slow, and it is usually necessary to embed diamond fine powder as a seed crystal in the metal carbide layer.
[0015]
Furthermore, for example, when manufacturing a diamond electrode of a niobium substrate, a conductive support substrate having the same shape as the final electrode was prepared, and a diamond film was directly formed thereon. Since this film formation is performed at a high temperature of 800 ° C. or higher, there is a problem that heat distortion or the like occurs in the conductive support base material, and an electrode as designed cannot be obtained. And if an electrode is a three-dimensional thing, the deformation | transformation by this heat will become still more remarkable.
[0016]
Furthermore, the conventional diamond electrode manufacturing method is basically a batch type. That is, a silicon wafer or a metal base material is carried into a CVD apparatus for each lot, and the CVD apparatus is repeatedly reduced in pressure, raised in temperature, formed into a film, lowered in temperature, raised in pressure, and the production method has a great energy loss. For this reason, these problems have hindered mass production of diamond electrodes, and have become one of the reasons why diamond electrodes are not popularized.
[0017]
The present invention has been made to solve these problems, and an object of the present invention is to provide diamond-deposited silicon used for a diamond electrode that can be used industrially, and a method for producing the same.
[0018]
[Means for Solving the Problems]
The present inventors have found that the above-mentioned problems can be solved by using silicon obtained by forming a conductive diamond film on a silicon substrate having a certain thickness, and have completed the present invention.
[0019]
That is, the present invention relates to diamond-coated silicon in which at least a part of a silicon substrate having a thickness of 500 μm or less is formed with conductive diamond, and the silicon substrate is manufactured by a plate-like crystal growth method. It is a diamond film silicon characterized.
[0020]
In addition, the present invention is a method for producing diamond-coated silicon, characterized in that at least a part of a silicon substrate having a thickness of 500 μm or less is formed with conductive diamond by chemical vapor deposition.
[0021]
Furthermore, the present invention provides a process for producing a silicon substrate having a thickness of 500 μm or less by a plate crystal growth method,
Depositing at least one part of the manufactured silicon substrate with conductive diamond by chemical vapor deposition;
A method for producing diamond-deposited silicon.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
The plate-like crystal growth method used in the present invention means a method for obtaining a plate-like silicon substrate, and is not particularly limited as long as a silicon substrate having a thickness of 500 μm or less can be obtained. Specific examples of the plate-like crystal growth method include an EFG method (Edge-defined Film-fed Growth method), a string ribbon method, a dendritic web method, and the like. Among these, the dendritic web method is a preferred example. More preferable examples can be given. Here, the EFG method raises the silicon melt by raising the slit of the die, which is a mold that defines the supply of the melt and the crystal shape, by capillarity, and bringing the seed crystal into contact therewith and solidifying it. Thus, a silicon substrate is obtained. In the string ribbon method, a plurality of strings (strings) are pulled up in a vertical direction from a silicon melt, and a film obtained by solidifying a film supported by surface tension between the strings is pulled up. How to get. In the dendritic web method, the seed crystal is directly contacted with the silicon melt without using a die, and a thin film (web) supported by surface tension between a plurality of dendrites (dendritic crystals) extending from the seed crystal. This is a method of obtaining a silicon substrate by pulling up a solidified material (see Japanese Patent Laid-Open Nos. 63-144187 and 2000-319088).
[0023]
According to these plate-like crystal growth methods, it is easy to obtain a silicon substrate having a large surface area, particularly when the diamond-coated silicon of the present invention is used for an electrode having a large surface area that is used industrially. It will be advantageous.
[0024]
The lower limit of the thickness of the silicon substrate used in the present invention is not particularly limited, but is preferably 0.1 μm or more from the viewpoint of ease of handling. That is, the thickness of the silicon substrate used in the present invention is preferably 0.1 to 500 μm, more preferably 10 to 300 μm, and still more preferably 50 to 200 μm. In addition, when the thickness exceeds 500 μm, the electrical resistance increases, which is disadvantageous when used for an electrode. Further, when the thickness exceeds 500 μm, the flexibility is reduced, and therefore, there is a problem that it is fragile, and cannot easily absorb thermal expansion caused by heat generated when used at a high current density, and is easily broken.
[0025]
The silicon substrate used in the present invention may be single crystal, polycrystalline, or amorphous, but a single crystal is preferable from the viewpoint that a diamond film can be easily formed and adhesion is excellent.
[0026]
In the case of producing a diamond film having a long length, the embodiments shown in FIGS. 2 and 4 described later may be used. In addition, when a smaller diamond-deposited silicon used for a sensor or the like is necessary, it can be obtained by arbitrarily cutting it with a diamond cutter or the like.
[0027]
The diamond-coated silicon of the present invention can be produced by depositing at least a part of a silicon substrate having a thickness of 500 μm or less with conductive diamond by CVD. Below, the manufacturing method of the diamond film formation silicon | silicone of this invention is demonstrated with reference to drawings.
[0028]
In FIG. 1, an example of embodiment of the manufacturing method of this invention is shown. In this embodiment, the method includes a manufacturing process of a silicon substrate having a thickness of 500 μm or less by the plate crystal growth method 1, a pretreatment process 2 for CVD diamond film formation, and a diamond film formation process 3. Then, when manufacturing an electrode, the pretreatment process 4 of a conductive support base material, the diamond deposition silicon | silicone and conductive support base material joining process 5 using an electroconductive joined body, and the electrode assembly process 6 are performed. Is called.
[0029]
A silicon raw material and a dopant are introduced, and a silicon substrate having a thickness of 500 μm or less is manufactured by the plate crystal growth method 1 (step (a)). When producing a p-type silicon substrate, a boron raw material, a gallium raw material, or an indium raw material is preferably used as a dopant. When manufacturing an n-type silicon substrate, a phosphorus raw material, an antimony raw material, and an arsenic raw material are preferably used as a dopant. The dopant is desirably added so that the electric resistance (volume resistivity) of the silicon substrate is 10 Ωcm or less, preferably 50 mΩcm or less, more preferably 15 mΩcm or less. In addition, after pulling up a silicon base material from a melting furnace, you may dope by an ion implantation method. In this case, it is not necessary to put a dopant in a melting furnace.
[0030]
The width | variety of a silicon base material is 1 mm-300 mm normally, Preferably it is 5 mm-200 mm, More preferably, it is 10 mm-150 mm. When the width is less than 1 mm, the diamond film formation may be difficult because the mechanical strength is weak. If the width exceeds 300 mm, it may be difficult to obtain a uniform silicon substrate. Since the length of the silicon base material produced here is endless, the diamond pretreatment step 2 is continuously performed, and further, the step of depositing at least a part of the silicon base material with conductive diamond by CVD ( You may send to a process (e)) with a conveyor. In this case, the step (a) and the step (e) are performed continuously.
[0031]
In addition, since the drawing speed of the silicon substrate is constant, the film forming speed may not be able to catch up depending on the thickness of diamond to be formed. That is, since the film formation speed when forming a tiremond film by CVD is usually about 0.1 to 5 μm / h, for example, when a 3 μm diamond film is formed at 1 μm / h, the residence of the CVD chamber Approximately 3 hours are required. In such a case, it is preferable to cut the silicon substrate into a predetermined length with a diamond cutter or the like immediately after taking out from the melting furnace. In addition, the length cut | disconnected here can also be matched with the shape of a final electrode, a use, or the structure of the CVD apparatus mentioned later. The silicon substrate cut to a predetermined length is sent to the pretreatment step 2 in a batch manner.
[0032]
In addition, since the silicon substrate immediately after being pulled out from the melting furnace is still at a high temperature, it is preferable that the silicon substrate is once cooled at a moderate temperature decrease rate of 50 ° C./h or less. The silicon substrate cooled to a temperature close to room temperature is sent to the pretreatment step 2 where the metal impurities and silicon oxide film adhering to the vicinity of the surface of the silicon substrate are cleaned and etched. An aqueous hydrochloric acid solution or the like is usually used for removing metal impurities, and an aqueous hydrofluoric acid solution is usually used for removing the silicon oxide film. In addition, since the silicon oxide film is naturally formed by being left for several hours after the etching, it is preferable to perform the silicon oxide removal operation immediately before sending it to the diamond film forming step 3.
[0033]
In the present invention, the diamond film forming step can be performed either continuously or batchwise. When performing by a continuous system, it is preferable to use microwave plasma CVD, and when performing by a batch system, it is preferable to perform by hot filament CVD, but it is not limited to these combinations.
[0034]
FIG. 2, FIG. 4, and FIG. 5 show an example of a tire base film forming process of a silicon substrate. FIG. 2 is an example suitable for forming a diamond film on a silicon substrate having a length of 1 m to 20 m, FIG. 4 is 20 m to 300 m, and FIG. 5 is a length of 2 m or less. There is no need to protect.
[0035]
FIG. 2 shows an example suitable for forming a diamond film on a silicon substrate having a length of 1 m to 20 m by microwave plasma CVD. The microwave generation unit includes a microwave generation source 20, a microwave waveguide 21, and a window 22 that transmits the microwave. The microwave generation source 20 may be a commonly used 2.45 GHz one or a higher frequency one. The window 22 is not particularly limited as long as it can transmit microwaves such as sapphire and quartz and can be blocked by pressure. When a reaction gas 24 composed of a carbon source such as hydrogen and methane and a dopant source is inserted into the CVD chamber 23 at a predetermined temperature and pressure, and a microwave irradiation is performed, a plasma ball 26 is generated and a silicon substrate 27 is formed. The film formation of diamond proceeds on the surface.
[0036]
The temperature of the silicon substrate during diamond film formation is preferably controlled to a predetermined temperature of 600 to 1000 ° C. A heater 33 may be provided to control the temperature of the silicon substrate.
[0037]
The CVD chamber is connected to a vacuum pump via a path 25 in order to maintain the CVD chamber 23 at a constant pressure at the time of diamond film formation, or to perform a high vacuum at the start-up of the apparatus. Yes. In the CVD apparatus, it is preferable to separately provide vacuum chambers 30 and 31 in a portion where the silicon base material 27 is carried in and out in addition to the microwave generating portion. The vacuum chamber 30 is divided into 30a, 30b, and 30c, and the vacuum chamber 31 is divided into 31a, 31b, and 31c, and three partitions having different pressures and temperatures. The partitions 30a, 30b, 31b and 31c are provided with a vacuum pump and a pressure control mechanism for individually adjusting the pressure. The chambers 30 and 31 are separated by the CVD chamber 23 and the opening 32, and the pressures of the partitions 30c and 31a are the same as those of the CVD chamber 23. The pressures of the partitions 30 b and 31 b are maintained at a higher pressure than the CVD chamber 23. For example, the CVD chamber 23 1.3 kPa When operating on, the pressure in partitions 30b and 31b is 13.3 kPa To maintain. At this time, the pressure of the partitions 30a and 31c is, for example, 43.2kPa Set to Thus, it is preferable to provide a mechanism for reducing the pressure of the CVD chamber 23 and the external atmospheric pressure stepwise through the partition. This is to prevent air or the like from leaking into the CVD chamber 23 along with the silicon substrate. The adjustment of the pressure by any of the partitions 30a, 30b, and 30c constitutes the step (d) of adjusting the pressure at least once according to the present invention, and the adjustment of the pressure by any of the partitions 31a, 31b, and 31c. Constitutes step (f) of adjusting the pressure at least once according to the present invention.
[0038]
These partitions are further provided with rubber dampers 29 to prevent air from entering. FIG. 3 shows details of the rubber damper portion. The rubber damper 29 is composed of two rubber plates 29a and 29b attached up and down, and is bonded to the wall surface of the partition 30a and further screwed. The upper and lower rubber plates 29a and 29b have overlapping portions, and the silicon base material 27 is sandwiched between the overlapping portions. Further, since the rubber plates 29a and 29b are spaced apart by about 90 degrees, this portion is sealed with the tapper 29c. Since the rubber damper 29 is depressurized on one side, the rubber damper 29 comes into close contact with the silicon base material 27 due to the pressure difference and functions as a mechanism for preventing air from entering. Various rubber materials such as natural rubber and silicon rubber can be used as the material of the rubber damper 29. Preferably, fluorine-based rubber having excellent heat resistance and chemical resistance is used. The air blocking mechanism using the rubber damper 29 is only possible when a silicon substrate having a thickness of 500 μm or less is used. This cannot be realized with a conventional round silicon wafer having a thickness of nearly 1 mm and a diameter of 300 mm. The lengths of the partitions 30c and 31a are appropriately determined depending on the carry-in speed of the silicon base material, but are usually about 50 cm. If the lengths of the partitions 30c and 31a are extremely shortened, even when these rubber materials are used, the sealing performance may be lowered when the temperature is 150 ° C. or higher. In the example of this embodiment, there is no need to provide a mechanism for controlling the temperature of these partitions, but a temperature control mechanism may be provided when precise temperature control is performed.
[0039]
The vacuum chambers 30 and 31 have a silicon substrate to be introduced as thin as 500 μm or less, so the height can be reduced to, for example, 1 mm or less, and a compact device structure is possible. The opening 32 can be provided with a gate structure that can block microwaves and is high enough to insert a silicon substrate, and can vary depending on the thickness of the silicon substrate on which the diamond film is formed. The width of the opening 32 can be appropriately adjusted to the silicon substrate to be formed, and is usually 300 mm or less. Since this opening width is relatively wide but low in height, there is no fear that microwaves leak into the outside air or the vacuum chambers 30 and 31. The opening 32 and the CVD chamber 23 are preferably metallic in order to block microwaves. Further, since the silicon base material has flexibility, it is preferable to provide a support of a wire net or a slat structure on the heater 33 of the CVD chamber 23.
[0040]
The passing speed of the silicon base material through the CVD chamber 23 is adjusted by a rotation mechanism 28 located before and after the CVD chamber 23. At the start of film formation, the entrance-side rotation mechanism 28a pushes the tip of the silicon base material 27 to the bottom of the plasma ball 26, and after the diamond film formation silicon reaches the exit-side rotation mechanism 28b, the exit-side rotation mechanism 28b. May adjust the chamber passing speed. The residence time of the silicon base material 27 in the CVD chamber 23 can be changed by the rotating mechanism 28, and the thickness of the diamond film can be adjusted. For example, the passing speed of the silicon base material 27 can be 1 mm / h to 500 mm / h. Of course, if a CVD technique capable of growing diamond at a higher speed is developed in the future due to the development of the technique, this passage speed can be further increased. The silicon substrate 27 reaches the lower side of the plasma ball 26 in the CVD chamber 23, and diamond film formation is started for the first time. Therefore, it may be inserted at a higher speed until the silicon base material 27 reaches below the plasma ball. An observation window made of quartz or the like may be separately provided on the wall surface of the CVD chamber 23 to confirm that the plasma ball 26 has been reached. In this case, it is preferable that the window be provided with a wire mesh used for a microwave oven or a microwave blocking mechanism in which metal is printed in a wire mesh shape.
[0041]
In microwave plasma CVD, since it is difficult to generate and control a plasma having a particularly large area, the width of the silicon substrate used in the example of this embodiment is usually 300 mm or less, preferably 200 mm or less, more preferably. Is 150 mm or less.
[0042]
In the present invention, by using a silicon substrate having a thickness of 500 μm or less as a film formation substrate, diamond film formation can be continuously and easily performed by microwave plasma CVD, which contributes to mass production of electrodes described later. It is.
[0043]
FIG. 4 shows a preferred embodiment for forming a diamond film of a silicon substrate having a length of 20 m or more. In FIG. 4, the CVD chamber 23 and the microwave generation unit are the same as those in FIG. 2, but the silicon substrate carry-in and discharge mechanisms are different. After the silicon substrate 27 is manufactured by the plate crystal growth method, the silicon substrate 27 is wound around the drum 41 by the step (b) of winding the silicon substrate. The diameter of the drum 41 is usually 50 mm or more, preferably 300 mm or more, more preferably 600 mm or more. When the diameter is less than 50 mm, a crack due to bending is likely to occur particularly in a single crystal silicon substrate. The diamond-coated silicon is collected as a roll on the drum 43, and the diameter of the drum 43 is preferably 50 mm or more. The thickness of the diamond film to be formed is usually 20 μm, preferably 10 μm or less, more preferably 5 μm or less. Since the diamond film is recovered by the drum 42, if the thickness of the diamond film is 20 μm or more, the diamond film portion is likely to crack. Further, as a method of installing the drum 42, it is preferable that the surface on which the diamond film is formed be on the outside. This is because diamond has a lower coefficient of thermal expansion than silicon. That is, the silicon substrate is stretched in a 600 to 1000 ° C. CVD chamber where diamond is deposited. When the temperature is lowered to near room temperature, the diamond layer is in a pressurized state due to the shrinkage of the silicon substrate. When the surface on which the diamond film is formed is wound in the drum box 42 so as to face the surface, the diamond film formation layer is further pressurized, which causes instability to the diamond layer.
[0044]
The loading and unloading of the silicon base material 27 is a batch type, but once set, a long silicon base material can be continuously formed, so that it sufficiently plays a role in mass production of electrodes described later. The pressures in the drum boxes 40 and 42 and the passages 44 and 45 are basically the same as those in the CVD chamber 23, and can be separated from the outside air in terms of pressure. When starting the film formation, the drum boxes 40 and 42 are opened, the drum 41 having the silicon base material 27 as a roll is installed, and the tip of the silicon base material is stretched up to the drum 43 in order to start winding. . At this time, the silicon base material from the lower side of the plasma ball 26 to the drum 43 is not formed and is untitled. Therefore, a dummy of another material may be joined to the tip of the silicon base material 27 here. After installing the drum 41, using a vacuum pump connected to the path 25 0.013 kPa Depressurize the entire system to remove air. Next, the reaction gas 24 is inserted into the CVD chamber 23, the gas flow rate and the vacuum pump are adjusted, the microwave generator is operated under a predetermined reduced pressure, and the film forming operation is started. Note that the passing speed of the silicon base material 27 in the CVD chamber 23 is preferably controlled using the rotation mechanism 46. The rotation of the drum 43 is applied with a torque sufficient to wind the silicon substrate without sagging, and is adjusted by the number of rotations of the rotation mechanism 46 for controlling the residence time. This is because even if the rotation speed of the drum 43 is kept constant, the diameter increases as the diamond film-forming silicon is wound up, and the passage speed cannot be controlled to be constant. The passing speed can be adjusted by the thickness of the diamond film to be formed, but is usually 1 mm / h to 500 mm / h. Of course, if a CVD technique capable of growing diamond at a higher speed is developed in the future due to the development of the technique, this passage speed can be increased. The step of carrying the silicon substrate 27 into the CVD by the rotation mechanism 46 constitutes the step (c) of supplying the wound silicon substrate of the present invention to the CVD apparatus. Further, the step of winding the diamond-coated silicon around the drum 43 is performed by winding the diamond-coated silicon of the present invention. Step (h) Configure.
[0045]
In the present invention, as is apparent from the examples shown in FIG. 2 and FIG. 4, continuous diamond film formation is possible even using microwave plasma CVD, which is usually difficult to form in a large area, This will greatly contribute to the mass production of electrodes described later.
[0046]
Next, FIG. 5 shows an example of an embodiment of the present invention when hot filament CVD is used. This is a film forming method and apparatus suitable when the length of the silicon substrate is 2 m or less. The film forming apparatus includes a CVD chamber 51, a load chamber 52, an unload chamber 53, a heating chamber 54, and a cooling chamber 55, and the load and unload chambers can be completely isolated in pressure by a gate 56 and a gate 57. It has become. Further, the load chamber 52 has a gate 58 for carrying in the silicon base material 27, and the unload chamber 55 has a gate 59 for taking out diamond-coated silicon. Metal conveyors 60, 61, and 62 for conveying the silicon base material 27 are installed at the bottom of each chamber. A tungsten filament 50 for CVD film formation is installed on the upper portion of the CVD chamber 51 so as to be perpendicular to the length direction of the silicon substrate 27. The tungsten filament is not necessarily installed at a right angle, but is preferably installed at a right angle. That is, when the length of the silicon base material 27 is 1 m or more, it is necessary to install a filament having a length of 1 m or more when attempting to install in the same direction. The filament itself becomes too hot and the filament itself becomes slack. For this reason, it is preferable to be positioned at a right angle so that it can be installed with as short a filament as possible. The CVD chamber 51 is provided with a piping for inserting the reaction gas 24 and a path 25 for evacuation. In the load chamber 52 and the unload chamber 53, hydrogen insertion lines 63 and 64 are installed, and lines 65 and 66 for vacuuming are installed. The CVD chamber 51 is provided with a heater 33 for controlling the temperature of the silicon substrate at the time of diamond film formation, and the silicon substrate temperature at the time of diamond film formation is controlled in the range of 600 ° C. to 1000 ° C. .
[0047]
As shown in FIG. 6, the heating chamber 54 and the cooling chamber 55 are formed of a silicon substrate temperature (T _CVD ) To room temperature (RT) so that the temperature does not increase or decrease rapidly. This is because the silicon base material 27 is not damaged by a temperature shock or the like. Furthermore, in diamond-coated silicon, it is necessary to relieve the stress caused by the temperature lowering operation caused by the difference in thermal expansion coefficient between the diamond layer and silicon. The temperature drop or temperature rise rate is preferably set so that the change in the silicon substrate temperature is 50 ° C./h or less. In the heating chamber 54 and the cooling chamber 55, such a temperature distribution is normally formed naturally due to heat radiation and heat retention of the CVD chamber 51. However, in order to maintain a more accurate temperature distribution, an auxiliary heater or indirect cooling is used. A mechanism may be provided below the heating chamber 54 and / or the cooling chamber 55.
[0048]
Next, the film forming operation of the silicon substrate in this embodiment will be described. In the steady state, in the CVD chamber 51, the heating chamber 54 and the cooling chamber 55, hydrogen gas, several percent methane, several hundred to several thousand ppm dopant source are 0.67 to 13.3 kPa Is maintained at a pressure of In the CVD chamber 51, the temperature of the filament 50 is maintained near 2000 ° C. and the substrate temperature is maintained near 800 ° C., and diamond film formation is performed. The gate 56 is closed and the gate 57 is open. To insert the silicon base material 27, first, the load chamber 52 is evacuated ( 0.013 kPa Until the reaction gas is removed from the load chamber 52. Next, air is inserted into the load chamber 52 through a path (not shown) separate from the hydrogen line to bring it to normal pressure. The gate 58 is opened only after the atmospheric pressure is reached, and the silicon substrate 27 is inserted into the load chamber 52. Although only one silicon substrate is loaded in FIG. 5, a plurality of inserts may be inserted. After inserting the silicon substrate 27, the gate 58 is sealed and evacuated to remove air from the load chamber 52. Next, hydrogen is inserted from the line 63 to maintain the same pressure as the pressure in the CVD chamber 51, and in this state, a film formation standby is performed. The silicon substrate 27 is sequentially formed in the CVD chamber 51, and the diamond-deposited silicon after the film formation is transferred to the connected cooling chamber 55, and the temperature is lowered to a temperature close to room temperature by gentle cooling. Since the gate 57 is open, the unloading operation is started when the diamond deposited silicon that has finished cooling approaches the unload chamber 53. When the diamond deposited silicon approaches the unload chamber 53, first, the conveyor 60 is fed so that the diamond deposited silicon completely enters the unload chamber 53. The approach of the diamond-deposited silicon to the unload chamber 53 can be detected by various commercially available position sensors such as lasers. When the diamond deposited silicon is completely inserted into the unload chamber 53, the gate 57 is closed and the reaction gas is removed by evacuation of the line 66. Next, air is inserted into the unload chamber 53 through a path (not shown) different from the hydrogen line, and the gate 59 is opened to take out the diamond-formed silicon. When the gate 57 for starting the unload operation is closed, the load operation of the silicon base material 27 that has been in the standby state in the load chamber 52 is performed. In the loading operation, the gate 56 is opened and the conveyor 61 is fed. At this time, since the conveyor 60 of the heating chamber 54 is constantly moving at a constant speed, it takes time for the silicon substrate 27 to completely move to the temperature raising chamber. It is preferable to confirm with a position sensor such as a laser that the temperature has been completely transferred to the temperature raising chamber. When the silicon substrate is completely transferred to the heating chamber 54, the gate 56 is closed. When the diamond film formation silicon is taken out from the unload chamber 53, the gate 59 is sealed, and the air in the unload chamber 53 is removed by evacuation. Next, hydrogen gas is introduced from the line 64 and is brought to the same pressure as the CVD chamber 51. After confirming that the pressure is the same, the gate 57 is opened. While repeating such operations, diamond film formation is performed semi-continuously by hot filament CVD. In the example of this embodiment, hydrogen gas is filled in order to obtain the same pressure during loading and unloading operations, but the reaction gas itself may be filled instead of hydrogen gas. In addition, since there exists a tendency for a soot to generate | occur | produce when the reaction gas containing a carbon source is put in 300-600 degreeC medium temperature atmosphere, Preferably hydrogen gas is used by loading and unloading operation. The size of the load and unload chambers can be reduced because the silicon substrate 27 only needs to be able to enter the conveyor. For this reason, the capacity for vacuuming and filling with hydrogen gas is small, and a compact load and unload chamber can be designed. That is, unlike the conventional hot filament CVD apparatus, there is no need to vacuum the entire CVD chamber. Further, according to the present embodiment, the temperatures of the CVD filament and the CVD chamber are always substantially constant. Unlike conventional hot filament CVD equipment and methods, there is no need to repeat heating, cooling, and evacuation for each substrate, film formation costs such as electricity bills can be significantly reduced, and filament life is also extended. .
[0049]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the diamond film formation silicon | silicone for using for a diamond electrode can be manufactured easily. Further, by using the diamond-deposited silicon of the present invention, a large-area electrode or a three-dimensional electrode can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a process for producing diamond-coated silicon and electrodes according to the present invention.
FIG. 2 is a diagram showing a manufacturing process of diamond-deposited silicon using microwave plasma CVD.
FIG. 3 is a diagram showing details of a rubber damper portion.
FIG. 4 is a diagram illustrating a manufacturing process of diamond-coated silicon using microwave plasma CVD.
FIG. 5 is a diagram showing a manufacturing process of diamond-deposited silicon using hot filament CVD.
FIG. 6 is a diagram showing a temperature change in each process using hot filament CVD.
[Explanation of symbols]
20 Microwave source
21 Microwave waveguide
23 CVD chamber
24 reaction gas
26 Plasma Ball
27 Silicone substrate
28 Rotating mechanism
29 Rubber damper
29a Rubber plate
29b Rubber plate
29c Tapper
30 Vacuum chamber
30a partition
31c partition
33 Heater
41 drums
42 drums
46 Rotating mechanism
50 Tungsten filament
51 CVD chamber
52 Load chamber
53 Unload chamber
54 Heating chamber
55 Cooling chamber
56-58 gate
60-62 conveyor
63, 64 Hydrogen insertion line
65, 66 Vacuuming line

Claims (5)

A method for producing diamond-coated silicon,
(A) A single crystal silicon group having a thickness of 0.1 μm to 500 μm and a width of 10 mm to 150 mm by at least one plate crystal growth method selected from the group consisting of EFG method, string ribbon method and dendritic web method The process of manufacturing the material,
(D) The silicon substrate manufactured in the step (a) is inserted into a loading vacuum chamber having at least one partition, and at least once from the atmospheric pressure to the operating pressure of the CVD (chemical vapor deposition) chamber. Adjusting the pressure to a reduced pressure;
(E) The silicon substrate is inserted into the CVD chamber maintained at a constant pressure and supplied with the reaction gas from the vacuum chamber for loading reduced in the step (d), and continuously or semi-continuously CVD A step of forming a conductive diamond film having a film thickness of 20 μm or less on a silicon substrate,
(F) The silicon substrate formed of conductive diamond in the step (e) is inserted from the CVD chamber into an unloading vacuum chamber having at least one partition, and at least from the operating pressure of the CVD chamber to the external pressure. A step of adjusting the pressure once,
(G) The step of taking out the conductive diamond film-formed silicon substrate whose pressure has been increased in the step (f) from the vacuum chamber for carrying out,
A method comprising the steps of: It is a manufacturing method of the diamond film formation silicon according to claim 1,
In the step (d) of adjusting the pressure at least once from the external pressure to the operating pressure of the CVD chamber and / or the step (f) of adjusting the pressure at least once from the operating pressure of the CVD chamber to the external pressure, The method further includes an air intrusion prevention method in which a rubber damper including two rubber plates overlapped with at least one partition is provided, and a silicon base material is carried in or diamond-formed silicon is carried out through the rubber damper. A method characterized by. It is a manufacturing method of the diamond film formation silicon according to claim 1,
After the step (a)
(B) a step of winding the single crystal silicon substrate manufactured in the step (a) around a drum having a diameter of 50 mm or more;
(C) inserting the single crystal silicon substrate wound up in the step (b) into the carrying-in vacuum chamber in the step (d);
Further, after the step (g), (h) a drum having a diameter of 50 mm or more, with the diamond-coated surface of the conductive diamond-coated silicon substrate unloaded in the unloading vacuum chamber in the step (f). The process of winding
A method characterized by comprising. It is a manufacturing method of the diamond film formation silicon according to claim 1,
In the step (e), the CVD method is a hot filament CVD method, and a tungsten filament is provided above the CVD chamber so as to be perpendicular to the length direction of the silicon substrate. It is a manufacturing method of the diamond film formation silicon according to claim 1,
The length of the silicon substrate produced in the step (a) is 1 m to 300 m.

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