JP4930974B2 - Saw wire, saw wire manufacturing method, semiconductor ingot cutting method, and wire saw - Google Patents

Description

  The present invention relates to a saw wire for cutting hard and brittle materials such as semiconductor ingots, ceramics, and glass substrates and a manufacturing method thereof, and more particularly to a saw wire suitable for slicing a semiconductor ingot and the like, a manufacturing method thereof, and the like.

  As a method of slicing a wafer from a semiconductor ingot or the like, a method of simultaneously slicing a plurality of wafers using a steel wire saw wire (multi-slice) is known. Specifically, the method includes arranging a plurality of tensioned saw wires in a row, traveling toward an ingot, and spraying a slurry containing free abrasive grains such as silicon carbide abrasive grains on the traveling saw wire. In this method, loose abrasive grains are drawn between the ingot and the saw wire, and a plurality of wafers are sliced while the ingot is worn away (also referred to as a loose abrasive grain system).

  The saw wire used in the above method is easily worn by free abrasive grains during slicing, and such wear reduces the cutting efficiency over time, and when wear occurs unevenly. However, there is a problem that warping and undulation occur in the sliced wafer, resulting in a decrease in the dimensional accuracy of the wafer.

  As means for solving the above-mentioned problems due to wear, for example, the following patent document 1 discloses a saw wire having a ceramic surface coated with a saw wire, and the following patent document 2 discloses a carbonaceous material having a hardness similar to a diamond coating or diamond. A saw wire provided with a membrane is disclosed. Each of the disclosed technologies aims to increase the hardness of the saw wire and improve the durability by increasing the surface hardness of the saw wire and suppressing the wear of the saw wire.

  As the slurry used for slicing by the free abrasive grain method using the saw wire in the prior art, an oily slurry in which free abrasive grains are dispersed in mineral oil, also called coolant, is used. The oily slurry is flammable because it uses oil as a dispersion medium, and is not suitable for long-time unattended operation in a multi-slice process. In addition, the oily slurry has a problem that it is unfavorable in terms of working environment such as strong odor. Furthermore, since oil and abrasive grains adhere to the wafer after slicing, it is necessary to clean them, but the process is complicated. Further, in the waste slurry treatment obtained by the cleaning, although the abrasive grains can be recovered, it is difficult to reuse the oil and the load on the environment is large.

  Further, in order to solve the problem of the slicing process in the free abrasive grain method using an oily slurry, an aqueous slurry using a non-flammable aqueous coolant has also been proposed. A wafer obtained by a slicing process using an aqueous slurry does not necessarily require an organic solvent for cleaning, and has an advantage that it can be cleaned only with water. However, there is a problem that it is difficult to stably disperse the abrasive grains in a high content ratio in the aqueous slurry and to maintain the dispersed state of the abrasive grains.

  As means for solving the problems in the loose abrasive grain system, a fixed abrasive grain system has been proposed in which teeth are formed by bonding diamond abrasive grains to the wire itself (for example, Patent Document 3).

The fixed abrasive method is a method in which diamond abrasive grains are bonded to a wire with a resin. In the slicing of a silicon wafer by such a fixed abrasive method, the ingot can be sliced only with water containing no free abrasive grains or water containing a small amount of a surfactant or the like.
JP-A-62-251061 JP 63-11274 A WO98 / 35784 brochure

  However, the saw wire formed by adhering diamond abrasive grains to the surface of the wire with a resin has a weak adhesive strength, and the abrasive grains may fall off from the wire surface during slicing. There was a problem that it was low and the lifetime was short.

  The present invention provides the above-mentioned various problems, that is, without using an oily slurry containing free abrasive grains, an aqueous slurry with a low content of free abrasive grains, or an ingot only with an aqueous solution containing no free abrasive grains. A saw wire using a fixed abrasive method capable of slicing, and having a high surface hardness, a long life and high durability, a method for cutting a semiconductor ingot using the same, and a wire saw using the saw wire The task is to do. And it makes it a subject to provide the manufacturing method suitable for manufacture of the said saw wire.

  The saw wire of the present invention is a saw wire in which a diamond thin film or a diamond-like thin film (hereinafter also simply referred to as a diamond-like thin film) is deposited on a wire base material, and a convex portion is formed on the surface of the saw wire. It is characterized by. By depositing a diamond-like thin film or the like on the surface in this way, and forming a convex portion on the surface of the saw wire, the convex portion functions as a tooth, so that an ingot or the like can be obtained without using a slurry containing free abrasive grains. Can be sliced. Further, since a diamond-like thin film or the like is deposited on the surface of the saw wire, a saw wire having a high surface hardness, a long life and high durability can be obtained.

  The convex portion on the surface of the saw wire is formed by a method of depositing a diamond-like thin film or the like on a wire substrate having a convex portion formed on the surface in advance, or a diamond-like thin film or the like on a wire substrate having a relatively smooth surface. It can be formed by growing it. The schematic diagram is shown in FIG.

  1A and 1B are schematic views showing an enlarged cross section of the saw wire of the present invention. 1A and 1B, 1A and 1B are wire base materials, 2 is a diamond-like thin film, and the like, and the diamond-like thin film 2 is attached to the surfaces of the wire base materials 1A and 1B. . And the convex part R is formed in the saw wire. And the wire base material 1A in FIG. 1 (A) is a wire base material with a smooth surface, and the wire base material 1B in FIG. 1 (B) is a wire base material with a rough surface. In addition, the wire base material with a smooth surface is a wire base material having a surface state with a ten-point average roughness (Rz) of less than about 0.5 μm, and the wire base material with a rough surface is a ten-point average. It is a wire base material having a surface state with a roughness (Rz) of about 0.5 to 25 μm.

  The saw wire of the present invention has a form in which a diamond-like thin film or the like 2 is deposited so as to form a convex portion on the surface of a wire base 1A having a smooth surface as shown in FIG. The surface of the wire base material 1B having a rough surface as shown in FIG. 2) may be any of a form in which a diamond-like thin film 2 or the like is deposited along the surface state, or a combination thereof. Good.

The diamond thin film in the present invention is a diamond thin film having a crystal structure of Sp ³ structure, and the diamond-like thin film is an Sp ³ structure called DLC (Diamond like Carbon), diamond-like hard carbon, and amorphous carbon, and / or Or it is a thin film containing the Sp ² structure and other carbonaceous materials.

  The film thickness of the diamond-like thin film or the like is preferably about 0.01 to 25 μm, and more preferably about 0.02 to 5 μm.

  In addition, the wire base material in the present invention is a metal wire having a high tensile strength, which has been conventionally used as a saw wire, and specifically, a Fe wire such as a piano wire and a hard steel wire. Metal wires such as metal wires and tungsten wires, so-called Inconel (Ni—Cr—Fe alloy), are used without particular limitation.

The saw wire of the present invention can be obtained by forming a diamond-like thin film or the like on the surface of a wire base material by a known thin film forming method. Examples of the thin film forming method include various CVD methods such as a plasma CVD (Chemical Vapor Deposition) method using a carbon-containing gas made of an organic substance such as CH ₄ , C ₂ H ₂ , CO, and lower alcohol as a carbon source, Vacuum deposition method using graphite or the like as a carbon source, DC magnetron sputtering method, RF magnetron sputtering method, ion beam sputtering method, plasma ion implantation method, superposition type RF plasma ion implantation method, ion plating method, arc ion plating method, Examples thereof include PVD (Physical Vapor Deposition) method such as laser ablation method. In the case of using the CVD method, a diamond-like thin film containing these elements may be formed by introducing a gas containing elements such as Si, B, F, N together with the carbon-containing gas. it can. Examples of the raw material gas containing elements such as Si, B, F, and N include monosilane, disilane, tetramethylsilane, dimethylsilane, CF ₄ , HFC, diborane, tetraborane, hexaborane, N ₂ , NH ₃ , and pyrrole. Contains five-membered rings. These gases may be introduced by mixing with a carbon-containing gas in advance, or may be introduced separately.

  Further, by introducing a compound containing a metal element such as V, Nb, Ta, Cr, Mo, W, Ti, and Zr, the diamond-like thin film or the like can contain the metal element as described above. The inclusion of these elements is preferable from the viewpoint that the hardness of the diamond-like thin film and the like can be further increased and the adhesion to the wire substrate can be increased. The content ratio of such a metal element in the diamond-like thin film or the like is preferably less than 30% in the atomic weight composition ratio in the thin film.

  In addition, as the surface roughness of the wire base material used for the saw wire of the present invention, a wire base material having a smooth surface with a 10-point average roughness (Rz) of less than about 0.5 μm as described above, or a 10-point average A wire base material having a rough surface with a roughness (Rz) of about 0.5 to 25 μm is used.

  The wire substrate having a rough surface can be obtained by etching a wire substrate having a smooth surface, polishing with abrasive grains, or scratching with a dice tool in a wire drawing process during wire production. When a wire base material having such a rough surface is used, saw wire teeth are formed by the convex portions of the wire base material formed by the roughening. Moreover, in the convex part of the said wire base material, thin film growth occurs preferentially at the time of thin film formation, and there exists an effect | action which enlarges a convex part further.

  As the etching treatment applied to the surface of the wire base material, a method of etching the wire base material with ions or radicals generated in plasma (plasma etching method) or a corrosive liquid such as acid or ferric chloride was used. Etching by a wet method, etching by a dry method using a corrosive gas, and the like can be given. In the plasma etching method, if a plasma CVD method is used for film formation, a plasma CVD apparatus can be used to perform an etching process as a pre-process of the film formation process, so that the manufacturing process can be simplified. Particularly preferred.

  Examples of the polishing using the abrasive grains include surface roughening using diamond abrasive grains, silicon carbide abrasive grains, cubic boronite (c-BN) abrasive grains, or a combination thereof, and the die. Examples of the damaging process using a tool include a method of roughening the wire surface by a damaging process using a die used in a wire drawing process. As the die, it is preferable to use a die having a surface made of diamond, silicon carbide, cubic boron knight (c-BN), or tungsten carbide. Furthermore, in the wire drawing step, the above-described die and diamond abrasive grains, silicon carbide abrasive grains, cubic boronite (c-BN) abrasive grains, or the like may be used in combination.

  As the surface roughness of the saw wire having a convex portion formed on the surface of the present invention, the ten-point surface roughness (Rz) is 0.05 to 40 μm, and further about 2 to 15 μm, which cuts the ingot or the like. This is preferable because the cutting speed can be kept high. In addition, the diamond-like thin film or the like is applied to an area of 85 to 100% with respect to the entire surface area of the wire base material, so that the diamond-like thin film or the like is more difficult to peel from the wire base material when cutting an ingot or the like. This is preferable.

  In the saw wire of the present invention, an intermediate layer 3 is further formed between the surface of the wire base 1A and the diamond-like thin film 2 as shown in FIG. Preferably it is.

  The intermediate layer 3 is formed by, for example, sputtering, DC magnetron sputtering, RF magnetron sputtering, CVD, plasma CVD, thermal spraying, ion plating or arc ion plating, plasma ion implantation, superposition RF plasma. 4A group elements such as titanium (Ti), 5A group elements, 6A group elements such as chromium (Cr), iron group elements, silicon, etc. obtained by film formation methods such as ion implantation, ion beam evaporation, or laser ablation (Si), Al or an amorphous film containing at least one of these carbides, nitrides, and carbonitrides, specifically, for example, silicon (Si) and carbon (C), titanium (Ti) and carbon (C ) Or an amorphous film containing chromium (Cr) and carbon (C). More specifically, a silicon carbide film formed using an ion beam evaporation method is particularly preferable. In this case, examples of the Si source and C source include monosilane, disilane, tetramethylsilane, dimethylsilane, methane, and acetylene. Propane, butane, benzene and the like can be used, and among these, monosilane, tetramethylsilane, acetylene and benzene are particularly preferable. These are preferably selected according to the type of the wire substrate 1. The thickness of the intermediate layer 4 is not particularly limited, but is preferably about 0.005 to 0.3 μm, and more preferably about 0.01 to 0.1 μm.

The saw wire of the present invention preferably has a tensile strength of 3000 N / mm ² or more. With such strength, the mechanical strength for use as a saw wire is sufficiently satisfied. Further, the Vickers hardness on the surface of the saw wire is preferably 1000 to 4500 Hv from the viewpoint of having particularly excellent machinability, longer life, and higher durability.

  The saw wire of the present invention described above, when cutting a semiconductor ingot, has a low abrasive content or no abrasive at all, instead of a slurry with a high abrasive content, which was conventionally required. A wafer can be efficiently cut out from a semiconductor ingot only with water or an aqueous solution in which a water-soluble additive such as a surfactant is dissolved in water.

  In order to manufacture the saw wire of the present invention, as a particularly preferable manufacturing method, a diamond-like thin film or the like is formed on the surface of the wire base material by the following film forming method using PVD and plasma CVD in combination. preferable.

  That is, it is a chamber for storing a plurality of carbon rods, and these carbon rods are arranged at a position around the specific central axis at an equal distance from the central axis and at an equal interval in the circumferential direction. Inserting the wire base material into a chamber arranged in a parallel posture, fixing the wire base material at a position matching the central axis, and applying tension to the wire base material; Applying a discharge voltage for generating a plasma of the carbon-containing gas to each of the carbon rods in the atmosphere, and reducing the pressure into the atmosphere containing the carbon-containing gas. By applying a bias voltage for trapping cations in the plasma to the wire fixed inside, the diamond surface is subjected to PVD and plasma CVD on the surface of the wire. It includes manufacturing method characterized by comprising the step of forming the de thin film or the diamond-like thin film. By such a manufacturing method, the diamond-like thin film formed on the wire base material is easy to form a particle-like (particle-like) film, so that it is easy to form a convex portion made of a diamond-like thin film, etc. The size of the convex portion is easy to control. In addition, since the film forming speed is high, the production efficiency is also excellent.

  In the manufacturing method, as described above, a plurality of carbon rods are arranged at equal distances and at equal intervals around the wire base material. The plurality of carbon rods function as a discharge electrode in the plasma CVD method and a carbon source in the PVD method. By applying a discharge voltage to the carbon rods, the carbon-containing gas existing between the carbon rods that are the discharge electrodes is turned into plasma, and carbon jumps out of the carbon rods. Then, by applying a bias voltage for capturing cations to the wire base, the cations of the carbon-containing gas plasma generated by the application of the discharge voltage are attracted to the surface of the wire base. In addition, since a plurality of carbon rods are arranged at equal distances and at equal intervals around the wire substrate to be treated as described above, a thin film is deposited almost uniformly on the surface of the wire substrate. Can do. Thus, in this manufacturing method, a thin film is uniformly formed on the surface of the wire base material with good adhesion.

  Further, in the saw wire manufacturing method, it is preferable that a magnetic field for locally increasing the plasma density as compared with other regions is formed in a region surrounded by the carbon rods. Thus, by forming a magnetic field to increase the plasma density around the wire base material and surrounded by each carbon rod, the generation speed of the thin film is increased, and the thin film grows in the form of particles. It becomes easy to do.

  Hereinafter, preferred embodiments of the method for producing a saw wire according to the present invention will be described in detail with reference to FIGS.

  FIG. 2 is a schematic view showing the configuration of the thin film forming apparatus for a wire substrate of the present invention. FIG. 3 (A) is a schematic diagram showing the arrangement of carbon rods, wire base materials, etc. arranged in the thin film forming apparatus for wire base materials, and FIG. 3 (B) is the right side of FIG. 3 (A). The side view seen from is shown. Further, FIG. 4 shows a circuit diagram of an AC discharge circuit for applying a discharge voltage to the carbon rod.

  The wire substrate thin film forming apparatus 4 shown in FIG. 2 is an apparatus that can use both the plasma CVD method and the PVD method.

  In FIG. 2, 6 is a chamber, 7 is a carbon rod and wire substrate fixing means, 7A is a carbon rod fixing jig, 8A is a gas introduction port, 8B is an exhaust port, F1 and F2 are gas flow adjustment mass flow controllers, T1 , T2 is a gas tank, P is pressure reducing means, M is a solenoid coil, V is a power supply for discharge voltage, B is a bias power supply, and S1 and S2 are springs.

  And as shown in FIG. 3 (A) and FIG. 3 (B), in the carbon rod 5A-5D and the wire base material fixing means 7 for fixing the wire base material 1 provided in the chamber, The carbon rods 5A to 5D are fixed to a carbon rod fixing jig 7A made of an insulating material such as ceramics, and the carbon rods 5A to 5D are positioned around the wire substrate 1 at an equal distance from the wire substrate 1 and The wire base material 1 is disposed in a position parallel to each other at a position at equal intervals in the circumferential direction. Moreover, the wire base material 1 is fixed with appropriate tension applied by springs S1 and S2. Further, a bias power source B for applying a bias voltage is connected to the wire base material 1.

  In the present embodiment, four carbon rods are used, but the number of carbon rods is not particularly limited as long as it is a plurality of numbers that can form a diamond-like thin film or the like almost uniformly on the entire surface of the wire substrate 1. In addition, by disposing a plurality of carbon rods in such a positional relationship, the carbon popping out from each carbon rod adheres to the surface of the wire base material 1 substantially uniformly, and the plasma of the carbon-containing gas in the vicinity of the wire base material 1. By generating the cation, the cations in the plasma are also attracted to the wire base material 1 to form the film efficiently. In the present embodiment, among the four carbon rods 5A to 5D, diagonally located 5A and 5C, 5B and 5D are made of conductive materials 5E and 5F such as copper wires and copper plates so as to be equipotential. Conducted.

  The solenoid coil M is excited by flowing an electric current, and forms a magnetic field for locally increasing the plasma density in the region surrounded by the carbon rods 5A to 5D in the chamber 6 as compared with other regions. is there. By forming a magnetic field for increasing the plasma density around the wire base 1 and surrounded by each carbon rod, the generation rate of the thin film is increased, and the thin film is likely to grow in the form of particles. . In the present embodiment, the solenoid coil M is provided on the outer peripheral portion of the chamber 6 in order to form a magnetic field as described above, and the wire base 1 has a single magnetic field at the center in the chamber 6. It is arranged in the part that becomes.

  A wire film forming process using the thin film forming apparatus 4 for a wire base material configured as described above will be described with reference to FIGS.

  First, in the chamber 6, the carbon rods 5 </ b> A to 5 </ b> D and the wire base material 1 are arranged in the arrangement as described above, and the chamber 6 is sealed.

The sealed chamber 6 is decompressed by the decompression means P. As the decompression means P, a rotary pump (oil rotary pump), an oil diffusion pump, or a combination thereof is used. Note that the decompression by the decompression means P is preferably as close to a vacuum as possible, and specifically, the decompression is preferably performed until it is about 10 ⁻³ Pa or less.

  Then, a carbon-containing gas is introduced into the decompressed chamber 6 from the gas introduction port 8A to make an atmosphere containing the carbon-containing gas. As the gas introducing means, a gas introducing device or the like provided with a flow rate adjusting means such as a mass flow controller is used. The gas pressure at this time is not particularly limited as long as plasma can be generated and maintained, but is preferably about 1 to 10 Pa from the viewpoint of film formation efficiency. At this time, gas components other than the carbon-containing gas may be mixed with the carbon-containing gas or introduced separately.

  Next, a discharge voltage is applied to the carbon rods 5A to 5D by the discharge voltage power source V to generate plasma of the carbon-containing gas. At this time, as shown in FIG. 4, the diagonally located 5A and 5C, 5B and 5D are made equipotential by the conductive materials 5E and 5F. In FIG. 4, TR is a transformer, K1 and K2 are protective resistors, and Vn and Vd are voltmeters.

The discharge voltage is not particularly limited as long as plasma can be generated and maintained, but is preferably 200 to 500V, and more preferably 250 to 400V. Further, the discharge current density is not particularly limited as long as the plasma can be generated and maintained, but is preferably about 0.01 to ¹ mA / cm ² , more preferably about 0.1 to 1 mA / cm ² . The discharge voltage at this time is, for example, a potential difference between voltage application terminals measured by a voltmeter Vd as shown in FIG. 4, and the discharge current density Id is between the protective resistors K1 measured by the voltmeter Vn. It is calculated from the potential difference.

  When a bias voltage is applied to the wire base material 1, cations derived from plasma generated by the discharge are attracted to the surface of the wire base material 1. Moreover, carbon jumps out from each carbon rod by the principle of PVD, and adheres to the surface of the wire base material 1. Then, by holding for a certain period of time, a diamond-like thin film or the like is formed on the surface of the wire substrate 1.

  The bias voltage is not particularly limited as long as the thin film formed by attracting the cation to the surface of the wire base material is not re-sputtered, but is preferably −50 to −250V.

  It is to be noted that when a solenoid excitation power source (not shown) connected to the solenoid coil M is turned on and a magnetic field for increasing the plasma density is formed in the region surrounded by each carbon rod in the chamber 6, the film formation speed is increased and the convexity is increased. From the viewpoint of promoting the formation of a thin film. The magnetic flux density of the magnetic field is not particularly limited as long as it forms a magnetic field that increases the plasma density as described above, but the magnetic flux density is, for example, 100 to 600 gauss, and further 300 to 600 gauss. It is preferable.

  In the saw wire manufacturing method of the present embodiment, the wire base material to be processed is cut discontinuously, but the wire base material feeding means to be processed is inside or outside the chamber. And a winding means is provided, and a long saw wire having a desired length is obtained by sequentially feeding a part of a continuous long wire base material to a predetermined position arranged as described above with respect to each carbon rod. You can also.

  As a characteristic of the saw wire obtained by such a manufacturing method, a convex shape such as a diamond-like thin film having a high hardness is deposited on the surface of the saw wire. This part becomes a tooth part and can be cut with high cutting efficiency. Furthermore, since the form of the convex portion can be controlled, a workpiece such as a semiconductor ingot can be cut with high accuracy. Further, since a diamond-like thin film having a high hardness is deposited on the surface of the saw wire, the surface of the saw wire has a hardness higher than the hardness of the workpiece, and therefore has a long life and high durability. In addition, when using a slurry containing loose abrasive grains, it is possible to maintain high cutting efficiency even when using an aqueous slurry having a low loose abrasive content ratio compared to conventional slurries. By forming a gap between the part and the workpiece, the loose abrasive grains are easily held by the wire, and a highly efficient cutting is possible due to a synergistic effect with the convex part.

  When cutting a semiconductor ingot with a wire saw using a saw wire, the saw wire of the present invention has a slurry with a low content of abrasive grains, or water or water that does not contain abrasive grains or a water-soluble additive such as a surfactant in water. The wafer can be efficiently cut out from the semiconductor ingot using the contained liquid.

  Next, a method for cutting out a plurality of wafers from a semiconductor ingot using the saw wire of the present invention will be described below.

  The saw wire of the present invention is an ingot cutting region in which the saw wire is stretched over a plurality of guide rollers a plurality of times, and the saw wires are arranged in a plurality of rows in parallel between specific guide rollers of the guide rollers. And driving the saw wire in the axial direction of the saw wire, and in a state where the saw wire is driven, the cutting region is substantially orthogonal to the axial direction of the saw wire and substantially orthogonal to the arrangement direction of the saw wires. And a step of cutting the semiconductor ingot at a plurality of locations with the saw wire.

  Moreover, the following is preferable as a wire saw that embodies the above method. That is, a wire saw for cutting a plurality of wafers from a semiconductor ingot, the saw wire of the present invention, a plurality of guide rollers on which the saw wire is stretched a plurality of times, and a wire for driving the saw wire in the axial direction of the saw wire Driving means, and the saw wire is wired so as to form an ingot cutting region by being arranged across a plurality of rows in a parallel state between the specific guide rollers of the guide rollers, and The semiconductor ingot is transferred by transferring the semiconductor ingot in a direction substantially perpendicular to the axial direction of the saw wire and substantially perpendicular to the arrangement direction of the saw wire in a state where the saw wire is driven by the wire driving means. Ingot transfer hand cut by the saw wire Include a wire saw, characterized in that it comprises a.

  A method of cutting a workpiece such as a semiconductor ingot using the saw wire and a wire saw will be described in detail with reference to FIG.

  The wire saw shown in FIG. 5 includes a pair of wire feeding / winding devices 10A and 10B and four guide rollers 24A, 24B, 26A and 26B arranged therebetween. Among these guide rollers, the guide rollers 24A and 24B are arranged at the same height position, and the guide rollers 26A and 26B are arranged at positions below the guide rollers 24A and 24B, respectively.

  Between the wire feeding / winding device 10A and the guide rollers 24A, 24B, 26A, and 26B, the fixed pulleys 12A, 14A, and 16A, the wire length operating device 18A, and the movable pulley are arranged in this order from the side near the wire feeding device 10A. 20A and a fixed pulley 22A are provided. Similarly, between the wire feeding / winding device 10B and the guide rollers 24A, 24B, 26A, 26B, in order from the side closer to the wire winding device 10B, fixed pulleys 12B, 14B, 16B, a wire length manipulating device. 18B, a movable pulley 20B, and a fixed pulley 22B are provided.

  Each of the wire feeding / winding devices 10A and 10B includes bobbins 9A and 9B around which the saw wire W is wound, and bobbin driving motors 11A and 11B that rotationally drive the bobbins. The saw wire W fed from the bobbin 9A of one wire feeding / winding device 10A is hung in the order of the fixed pulleys 12A, 14A, 16A, the movable pulley 20A of the wire length operating device 18A, and the fixed pulley 22A. 24A, 24B, 26B, and 26A, after being wound a plurality of times, the fixed pulley 22B, the movable pulley 20B of the wire length operating device 18B, and the fixed pulleys 16B, 14B, and 12B are hung in this order, and the other wire is fed and wound. The wire is wound around the bobbin 9B of the take-up device 10B, and an appropriate tension is applied to the saw wire W by both wire length operation devices 18A and 18B. The saw wire W is wound around a plurality of guide rollers so as to maintain a parallel state over a plurality of rows, thereby forming a cutting region C.

  Of the guide rollers 24A, 24B, 26B, and 26A, the rotation shafts of the lower guide rollers 26A and 26B are respectively connected to a main motor 25A (first drive motor) that individually rotates the guide rollers 26A and 26B. A main motor 25B (second drive motor) is connected. Then, the saw wire W is fed out from the bobbin 9A by switching the rotational drive direction of the bobbins 9A, 9B by the bobbin drive motors 11A, 11B and the rotational drive direction of the guide rollers 26A, 26B by the main motors 25A, 25B. Thus, the state can be switched between a state where it is wound around the bobbin 9B and a state where the saw wire W is unwound from the bobbin 9B and wound around the bobbin 9A.

  That is, in this wire saw, a large number of wires W are stretched between the guide rollers 24A and 24B in parallel with each other while being reciprocated in the longitudinal direction.

  Above the saw wire W stretched between the guide rollers 24A and 24B, a work feeding device 30 for moving a cylindrical work (for example, a semiconductor ingot) 28 is provided. The workpiece feeding device 30 includes a workpiece holding unit 32 and a workpiece feeding motor 34. The workpiece holding unit 32 holds the workpiece 28 in a direction in which a target crystal orientation can be obtained based on the crystal axis. The workpiece feeding motor 34 is combined with a ball screw (not shown), 32 and the workpiece 28 are moved up and down integrally (that is, cut and fed). In this embodiment, the work feed motor 34 is constituted by a servo motor and also serves as a feed position detecting means for detecting the cutting feed position of the work 28.

  Above the saw wire W stretched between the guide rollers 24A and 24B, machining fluid supply devices 36A and 36B are provided at positions on the left and right sides of the work 28. These machining liquid supply devices 36A and 36B supply the machining liquid simultaneously to the saw wires W that are driven at high speed, and attach them to the surface of the saw wire W.

  In this wire saw, a plurality of saw wires W stretched between the guide rollers 24A and 24B are simultaneously driven in the longitudinal direction at a high speed, and the machining fluid is supplied to the saw wires W from the machining fluid supply devices 36A and 36B. However, the workpiece 28 is cut and fed in the cutting region C direction by transferring the workpiece 28 in a direction substantially perpendicular to the axial direction of the saw wire W and substantially perpendicular to the arrangement direction with respect to the saw wire W. A large number of wafers are cut out simultaneously.

  Since the wire saw of the present invention uses a saw wire having a convex portion on the surface of the wire and having a diamond-like thin film or the like formed on the surface thereof, an aqueous slurry with a small content of abrasive grains, or frictional heat not containing abrasive grains is used. Even when a machining fluid intended for the cooling effect is used, the workpiece can be cut with high cutting efficiency. Moreover, since the content rate of abrasive grains is low, or processing can be performed with high cutting efficiency without containing abrasive grains, wear of the saw wire itself can be reduced. Therefore, the saw wire of the present invention has a long life and high durability.

  When slicing a wafer from an ingot or the like using the saw wire of the present invention, the ingot can be efficiently sliced using only an aqueous slurry having a low content of free abrasive grains or water containing no free abrasive grains. Therefore, it is possible to realize a cutting environment in which there is a risk of ignition due to volatilization of the slurry dispersion medium and generation of malodor. Moreover, also when using the slurry containing a free abrasive grain, cutting efficiency can be maintained even if the quantity of the free abrasive grain in a slurry is reduced rather than before. Further, since the surface of the saw wire is hard, it is a long-life saw wire in which the cutting efficiency is hardly lowered with time.

  Hereinafter, the present invention will be described in more detail based on examples.

  A saw wire of the present invention was manufactured by the following method using the thin film forming apparatus 4 for a wire substrate as shown in FIGS. In this example, the wire base material has a diameter of 0.3 mm and a ten-point average roughness (Rz) of 2.78 μm piano wire (a rough surface of the wire base material A) and a diameter of 0.3 mm and a ten-point average. A piano wire (wire base material B having a smooth surface) having a roughness (Rz) of 0.47 μm was used.

  2 and 3, 6 is a chamber, 5A to 5D are cylindrical carbon rods (diameter 3 mm, length 300 mm, carbon purity 99.9995%), F1 and F2 are gas flow control mass flow controllers (MFC), T1 and T2 are gas tanks, P is a pressure reducing means comprising an oil diffusion pump P1 and a rotary pump P2, 8A is a gas inlet, 8B is an exhaust port, V is a power supply for discharge voltage, B is a bias power supply, and M is a solenoid coil. .

A current source (MODEL: PAD 70-15L) is connected to the solenoid coil M, and a magnetic field is formed by applying an excitation current. The discharge voltage power supply V is for applying a discharge voltage, and an AC power supply of AC 600 Hz was used. Furthermore, the discharge voltage power source V is connected to a circuit as shown in FIG. 4, and an AC voltage (1φ200V) is amplified by a transformer TR (WTC-1K: MATSUNAGA MFG. CO., LTD). A 1 kΩ resistor (RWH200G) was provided as the protective resistors K1 and K2, and the discharge current was measured from the potential difference of the protective resistor K1. Further configured to measure a discharge voltage by the voltage meter V _d provided between voltage terminal to be applied to the carbon rod 5A-5D.

  As shown in FIGS. 3A and 3B, the wire base 1 is disposed at an equal distance from the carbon rods 5A to 5D, and the tension is maintained by using the springs S1 and S2.

  The carbon rods 5A to 5D are arranged such that each carbon rod is positioned at four vertices of a square of 5 mm each so that the axis center of the cylinder is located, and the wire base material is located at the intersection of the diagonal lines of the square. The ceramic carbon rod and the wire base fixing means 7A thus formed were arranged. And the wire base material 1 and the carbon rods 5 </ b> A to 5 </ b> D arranged as described above were installed in the central portion of the chamber 6 having a uniform magnetic field distribution. The carbon bars 5A and 5C, 5B and 5D located diagonally were made equipotential by conducting with a copper plate having a width of about 1 cm.

  One end of the wire base 1 was connected to a bias power source B via a spring S2 and the other end was connected to a spring S1 in order to apply a bias for drawing sputtered ions.

  In the apparatus 4 configured as described above, after the chamber 6 was decompressed, methane gas was introduced from the gas inlet 8A. Then, a discharge voltage was applied to the carbon rods 5A to 5D and maintained for 10 minutes while a bias voltage was applied to the wire substrate 1, and a saw wire W having a diamond-like thin film deposited on the surface was obtained. The film forming conditions at this time are shown in Table 1.

  Scanning electron microscope micrographs of the surface of the saw wire W thus obtained are shown in FIGS. 6 (A) to 6 (C).

  6A is a photograph of a surface of a saw wire obtained by coating a thin film on a wire base A having a rough surface at a magnification of 200. FIG. 6B is a thin film on a wire base B having a smooth surface. FIG. 6C is a photograph of the surface of a saw wire with a thin film deposited on a wire base material B having a smooth surface taken at a magnification of 2000 times. It is a photograph.

  Further, the ten-point average roughness (Rz) of the surface of the saw wire obtained by depositing a thin film on the wire base A having a rough surface was measured with a surface shape measuring microscope (VF-7500, manufactured by CERSA-MCJ). .1 μm. On the other hand, the ten-point average roughness (Rz) of the surface of the saw wire obtained by depositing a thin film on the wire base B having a smooth surface was 3.1 μm.

FIG. 7 shows the spectrum of Raman spectroscopy obtained by evaluating the thin film deposited on the surface of the saw wire in FIG. In the spectrum, a broad peak indicating the presence of a DLC film having a peak at 1541.8 cm ⁻¹ was confirmed.

  Since the saw wire thus obtained has a convex portion that functions as a tooth on the surface, an ingot or the like can be sliced only with an aqueous solution without using a slurry containing abrasive grains. Therefore, it is possible to realize a cutting operation in which the risk of ignition due to volatilization of the slurry dispersion medium and the generation of malodors are suppressed. Even when a slurry containing loose abrasive grains is used, the cutting efficiency can be maintained even if the amount of loose abrasive grains in the slurry is significantly reduced as compared with the prior art. Further, since the surface of the saw wire is hard, it is a long-life saw wire in which the cutting efficiency is hardly lowered with time.

1A to 1C are schematic views showing an enlarged cross section of the saw wire of the present invention. FIG. 2 is a schematic view showing the configuration of the thin film forming apparatus for a wire substrate of the present invention. FIG. 3 is a schematic diagram showing the arrangement of carbon rods, wire substrates, and the like arranged in the thin film forming apparatus for wire substrates. FIG. 4 is a circuit diagram of an AC discharge circuit for applying a discharge voltage to the carbon rod. FIG. 5 is a schematic view showing a wire saw of the present invention. FIG. 6 is an enlarged photograph of the surface of the saw wire of the present invention obtained in the example by an electron microscope. FIG. 7 is a spectrum of Raman spectroscopy in which the surface of the saw wire is evaluated by Raman spectroscopy.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A, 1B Wire base material 2 Diamond-like thin film etc. 3 Intermediate layer 4 Wire base material thin film forming apparatus 5A-5D Carbon rod 5E, 5F Conductive material 6 Chamber 7 Carbon rod and wire base material fixing means 7A Carbon rod fixing treatment Tool 8A Gas introduction port 8B Exhaust port 9A, 9B Bobbin 10A, 10B Wire feeding / winding device 11A, 11B Bobbin drive motor 12A, 12B, 14A, 14B, 16A, 16B, 22A, 22B Fixed pulley 18A, 18B Wire length operation Device 20A, 20B Movable pulley 24A, 24B, 26A, 26B Guide roller 25A, 25B Main motor 28 Work 30 Work feed device 32 Work holding unit 34 Work feed motor 36A, 36B Working fluid supply device C Cutting area Id discharge current K1, K2 Protection resistance V Power supply for discharge voltage V _d , V _n Voltmeter TR Transformer S1, S2 Spring M Solenoid coil B Bias power supply P Pressure reducing means P1 Oil diffusion pump P2 Rotary pump R Convex W Saw wire F1, F2 Gas flow adjustment mass flow controller T1, T2 Gas tank

Claims (7)

A method for producing a saw wire by depositing a diamond thin film or a diamond-like thin film on the surface of a wire substrate,
A chamber for storing a plurality of carbon rods, and these carbon rods are parallel to each other at a position around the specific central axis at an equal distance from the central axis and at equal intervals in the circumferential direction. Inserting the wire base into a chamber arranged in a posture, fixing the wire base at a position matching the central axis, and applying tension to the wire base;
Reducing the pressure in the chamber and creating an atmosphere containing a carbon-containing gas;
Under the atmosphere, a discharge voltage for generating a plasma of the carbon-containing gas is applied to each carbon rod, and cations in the plasma are captured by the wire fixed inside the carbon rod. Forming a diamond thin film or the diamond-like thin film on the surface of the wire by PVD and plasma CVD by applying a bias voltage for the purpose of manufacturing a saw wire. 2. The saw wire manufacturing method according to claim 1 , wherein a magnetic field for locally increasing a plasma density in a region surrounded by each carbon rod is formed in the chamber as compared with other regions. Saw wire manufacturing method. A saw wire manufactured by the manufacturing method according to claim 1 or 2,
Ri diamond thin film or diamond-like thin film on a wire substrate name is deposited, the saw wire, characterized in that projections on the saw wire surface is formed. The saw wire according to claim 3 , wherein the surface roughness (ten-point average roughness Rz) of the saw wire is 0.05 to 40 µm. Saw wire according to claim 3 or claim 4 wherein the surface roughness of the wire substrate (ten-point average roughness Rz) is equal to or is 0.5 to 25. A method of cutting a plurality of wafers from a semiconductor ingot,
The saw wire according to any one of claims 3 to 5 is spanned a plurality of times on a plurality of guide rollers, and the saw wires are parallel to each other between a plurality of guide rollers among the guide rollers. Forming an arrayed ingot cutting region and driving the saw wire in the axial direction of the saw wire;
In a state where the saw wire is driven, the semiconductor ingot is transferred to the cutting region in a direction substantially orthogonal to the axial direction of the saw wire and substantially orthogonal to the arrangement direction of the saw wire. A method for cutting a semiconductor ingot, comprising: a step of cutting. A wire saw for cutting a plurality of wafers from a semiconductor ingot,
The saw wire according to any one of claims 3 to 5 ,
A plurality of guide rollers on which the saw wire is wound a plurality of times;
Wire driving means for driving the saw wire in the axial direction of the saw wire,
The saw wire is wired so as to form an ingot cutting region by being arranged over a plurality of rows in parallel between specific guide rollers of the guide rollers,
The semiconductor ingot is transferred by transferring the semiconductor ingot in a direction substantially orthogonal to the axial direction of the saw wire and substantially orthogonal to the arrangement direction of the saw wire with the saw wire driven by the wire driving means. A wire saw comprising an ingot transfer means for cutting the wire with the saw wire.