JP2010046792A - Cutting apparatus and cutting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus capable of solving the problems such as a relatively slow cutting speed, wire breakage proneness, and a large cutting margin, when cutting a wafer out of an ingot. <P>SOLUTION: Upon cutting the ingot 102 to cut out the wafer, the ingot 102 is rotated centering around a rotary shaft perpendicular to a cutting plane and cut by electric discharge machining by a wire 101 or a rotary blade. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a cutting apparatus and method, and more particularly to a configuration suitable for application to an apparatus for cutting an ingot to cut a wafer.

  An example in which a wafer is cut from an ingot by wire electric discharge machining will be described with reference to FIG. The wire 101 is one, the wire 101 is sent in the direction of the arrow, and at the same time, the gantry supporting the ingot moves, the wire 101 substantially moves in the cutting direction, and finally the wafer is cut. Done. In the cutting by electric discharge machining, when the wire 101 and the ingot 102 are close to each other, an electric discharge is generated there, whereby the ingot and a part of the wire become plasma, and the ingot evaporates or breaks due to thermal stress. Finally, cutting is performed.

  Therefore, the place where the discharge occurs is generated at many points in a line shape in contact with the ingot 102 on the line along the wire 101. That is, in the entire linear shape, no discharge occurs at a time, and a discharge occurs only at a point.

  In general, electric discharge machining is performed in water or oil (Patent Document 1, etc.). This is because the cutting process is performed due to the electrical breakdown of the electrical insulating fluid. However, it may be performed in the air.

  This process can be cut without contact. Since the mechanical force generated in the wafer being cut out is not large, there is a possibility that the wafer can be cut thinly.

  In Patent Document 1, an inert gas is filled in an upper space of a highly insulating oil injected into a sealed container, and a semiconductor crystal rod is discharged between a wire immersed in the highly insulating oil and the semiconductor crystal rod. As a method for cutting, a configuration is disclosed in which high-insulating oil is heated and maintained at a temperature of 150 ° C. or higher, and the semiconductor crystal rod is cut in a reduced resistivity.

  Further, Patent Document 2 discloses a cutting apparatus and method that suppresses damage to a workpiece when cutting an ingot with a wire, during grooving, and accurately matches the cut surface with the crystal plane. For ingot cutting, Patent Documents 3-5 and the like are also referred to.

Japanese Patent Laid-Open No. 10-217036 JP 2004-66734 A JP 2003-332273 A JP 2006-75952 A JP 2007-237348 A

Cutting by electric discharge machining
Cutting speed is relatively slow,
The wire is easy to break,
There is a problem.

  Thin wires are used to narrow the cutting allowance, but thin wires are easy to break.

  Further, when cutting a wafer from an ingot, it is desired to reduce the cutting allowance. Even with the same thickness of wire, the cutting allowance may vary greatly depending on operating conditions.

  This is a number of important issues when cutting from an ingot to a wafer.

  Accordingly, it is an object of the present invention to provide a cutting apparatus and method that solves the problems that the cutting speed is relatively slow, the wire is easily cut, and the cutting allowance becomes large.

  In order to solve the above-described problems, the invention disclosed in the present application is generally configured as follows.

  According to one aspect of the present invention, there is provided a cutting apparatus that, when cutting an ingot and cutting a wafer, rotates the ingot around a rotation axis orthogonal to the cutting surface and cuts the ingot by electric discharge machining. .

  In the present invention, the ingot is cut by electric discharge machining using a wire or a rotary blade.

  In the present invention, the feeding direction of the wire and the ingot rotation direction at the contact portion between the wire and the ingot are forward directions (including the same direction, not the reverse direction).

  In the present invention, there is provided means for discharging the facet coming out from the cutting portion of the ingot.

  In this invention, it is good also as a structure provided with the rotating disk for discharging | emitting the facet of the said ingot of the cutting location by the said wire electric discharge machining. The rotating disk rotates in the rotation direction for discharging the ingot facet in the cutting allowance of the ingot, and discharges the ingot facet at the cutting position by the wire electric discharge machining.

  In this invention, it is good also as a structure provided with the means (suction pipe) to attract | suck for discharging | emitting the said facet.

  In this invention, it is good also as a structure provided with the supporting member which supports the lower part of the wafer cut | disconnected (cut off) from the said ingot. The support member may be configured to support the ingot and the wafer while rotating.

  In this invention, it is good also as a structure provided with the means to light-irradiate the contact part of the said wire or rotary blade, and the said ingot.

  In the present invention, the rotary blade may be an outer blade. Alternatively, an inner blade method may be used. The rotary blade may include a hard material powder such as diamond or silicon carbide.

  In this invention, it is good also as a structure provided with the slit on the said rotary blade surface. In the present invention, the rotary blade has an electrical insulating layer on the front and back surfaces of the metal layer, and the electrical insulating layer is removed from the slit portion. Alternatively, in the slit portion, the electrical insulating layer may be configured to be thinner than other than the slit portion.

  In this invention, it is good also as a structure provided with the some rotating blade in common with the rotating shaft.

  In the present invention, electric discharge machining may be performed in an insulating fluid in which active chlorofluorocarbon molecules and fluorine ions are generated in plasma.

  In this invention, it is good also as a structure which makes the site | part containing the insulating fluid in which electric discharge machining is performed airtight, and prevents the diffusion from the said insulating fluid to the atmosphere. In the present invention, cooling means for controlling the temperature of the insulating fluid is provided. Or it is good also as a structure provided in the apparatus with the means to solidify the gas from an insulating fluid again.

  In the present invention, the ingot may be processed into a columnar shape before the wafer is cut out so that the cross section of the ingot has the same diameter.

  According to the present invention, when cutting an ingot and cutting a wafer, there is provided a cutting method in which the ingot is rotated around a rotation axis orthogonal to the cutting surface and the ingot is cut by electric discharge machining. In the present invention, the ingot is cut by electric discharge machining using a wire or a rotary blade. In the method according to the present invention, the feeding direction of the wire and the ingot rotation direction at the contact portion between the wire and the ingot are forward directions.

  According to the present invention, it is possible to solve the problems that the cutting speed is relatively slow, the wire is easily cut, and the cutting margin is increased.

It is a figure explaining the cutting | disconnection of a wafer from the ingot by an electric discharge machine. It is a figure explaining the 1st Example of this invention. It is a figure explaining the 2nd Example of this invention. It is a figure explaining the 2nd Example of this invention. It is a figure explaining the 3rd Example of the present invention. It is a figure explaining the 4th Example of this invention. It is a figure explaining the 5th Example of this invention. It is a figure which shows the structure of the rotary blade of the 5th Example of this invention. It is a figure which shows the groove structure of the rotary blade (outer blade) surface of the 5th Example of this invention. It is a figure which shows the groove | channel structure cross section of the rotary blade (outer blade) surface of the 5th Example of this invention. It is a figure explaining the rotary blade (inner blade) of the 6th Example of this invention. It is a figure which shows the structure (multi-outer blade) of the 7th Example of this invention. It is a figure which shows the structure of the 8th Example of this invention. It is a figure which shows the ribbon cross-sectional shape of the 9th Example of this invention. It is a figure which shows the ribbon cross-sectional shape of the 9th Example of this invention. It is a figure which shows an example of the ribbon feed mechanism of the 9th Example of this invention. It is a figure explaining the 10th Example of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 2 is a diagram for explaining an embodiment of the present invention. In cutting the ingot 102 along a plane orthogonal to the longitudinal direction, the ingot is rotated around a rotation axis orthogonal to the cutting plane, and the ingot is cut by electric discharge machining.

  While rotating the ingot 102, the wire 101 is sent as shown in FIG. 2, and the work (structure system supporting the ingot: not shown in FIG. 2) is moved and cut. The part where the wire 101 and the ingot 12 come into contact is one place.

  In the example shown in FIG. 1, the wire 101 is sent, but after the discharge is performed upstream of the wire 101, the discharge may occur at a location quite close to the discharge portion of the wire 101 even downstream. Then, it was observed in several experiments that the damage of the wire 101 of the said part became large and eventually cut | disconnected.

  Wire electric discharge machining can be understood as a stochastic process in a sense. Managing wire damage is difficult in principle and is expected to break with some probability.

  According to experiments, when the wire feed is slow, the wire is frequently cut, and when it is fast, it is difficult to cut. However, if the wire feed speed is increased, more wires are required, which deteriorates the economy.

  If the wire feed is set at the same speed and the cutting speed is increased, wire breakage is likely to occur, and damage caused by electric discharge can be observed with a wire microscope.

  Thus, it can be understood that the wire easily breaks when the wire and the workpiece are in line contact.

  Therefore, in order to avoid this problem, the damage of the wire due to the discharge can be managed by setting the portion where the wire and the ingot are in contact with each other (point contact). That is, it is possible to prevent the discharge at the same place or very close place of the wire from occurring a plurality of times.

  As a result, it is expected that the probability of wire cutting is greatly reduced and stable electric discharge machining is performed.

  Furthermore, the facets are easily discharged because of point contact.

  As shown in FIG. 2, the wire feed, the direction, and the movement of the ingot tangent direction at the ingot contact portion may be aligned so as to be in the same direction (forward direction). This is because the generated facet moves with respect to the insulating fluid, and the insulating fluid moves along the movement of the ingot and the wire, so it is more smooth if the direction of movement of the wire at the contact point matches the direction of movement of the ingot. This is because the discharge is easily performed.

  Although not shown, the cutting device by electric discharge machining is provided with a control system that performs control for moving the wire or moving the ingot or the entire wire in the cutting direction.

  Next, speeding up cutting (cutting quickly) will be described. Furthermore, a countermeasure for reducing the cutting allowance will be described.

  As shown in FIG. 3, the rotating disk 104 for assisting the discharge of the facet is used to assist the discharge of the facet.

  When the diameter of the wire 101 is large, the cutting margin width is increased. Until now, experiments have been performed at 200 microns or less. Insulation fluid such as water or oil enters the cutting margin, but since the gap is narrow, the insulation fluid that enters between them moves almost the same as the movement of the object that is in contact therewith. For this reason, the facet generated at the point contact between the wire 101 and the ingot 102 which is the workpiece is moved along the rotation direction of the ingot 102 and moves as indicated by the arrow of the facet movement. If the face is left as it is, it is predicted that the face will wrap around and will again wrap around to the point where the cutting process is being performed. When the face reaches the place where the electric discharge machining is performed again, the energy of the electric discharge is absorbed by the face, so that the cutting speed is reduced, and the electric discharge is easily made to other places in the ingot, so that the cutting allowance is reduced. This is because of the increase.

  In the experiment, the cutting allowance increased as the number of facets attached to the wafer sample increased.

  When the cutting allowance increases, the energy from the power source is the same, so the actual cutting speed decreases.

  Therefore, before the cutting piece reaches the electric discharge machining point again, it is inserted between the cutting allowances using the rotating disk 104, and the cutting piece is discharged.

  The rotating disk 104 moves to keep the distance from the uncut portion of the ingot 102 constant as the cutting of the ingot 102 progresses.

  The rotating disk 104 is provided with a control system for synchronizing with the wire 101 for cutting. FIG. 3 shows the direction of operation of the rotating disk shaft.

  FIG. 4 is a view of the positions of the cutting allowance 106, the ingot 102, and the rotating disk 104 as viewed from the feeding side of the wire 101. The wire 101 moves in the direction perpendicular to the figure, and the cutting direction is the direction of the rotation axis of the ingot 102. A rotating disk 104 for discharging the facet is disposed on the opposite side of the wire 101, and proceeds in the direction of the arrow of the rotating disk traveling direction as the cutting progresses, and is generated from the point where the wire 101 and the ingot 102 are in contact with each other. The facet to be discharged is discharged.

  Since the rotary disk 104 is used for discharging the facets, the thickness needs to be thinner than the cutting allowance. The direction of rotation is taken to be easy to discharge.

  Furthermore, it is desirable to control the rotating disk 104 so that it does not contact the uncut portion of the ingot 102 and the ingot 102 itself. Accordingly, it is predicted that the cutting speed increases and the cutting allowance decreases.

  Next, in order to facilitate face discharge, introduction of a suction pipe and light for facilitating maintenance of discharge are performed.

  FIG. 5 shows another embodiment of the present invention. First of all, it has not been an experiment so far that the places where the facets come out are widely distributed.

  For this reason, the mouth of the pipe 107 for sucking the facet is placed at the place where the facet comes out, and a device for sucking the facet is installed. In general, when impurities are mixed in the insulating fluid, for example, pure water reduces the electrical resistivity, and the electrical discharge machining is any good.

  Therefore, it is not good to leave the facet in the insulating fluid as it is, so place the suction pipe port where the facet comes out, suck the facet together with the insulating fluid, and the facet is not widely distributed in the insulating fluid. Like that.

  And after attracting | sucking, if a face is adsorb | sucked through a filter and a pure water, insulating oil, etc. will be returned, the operating cost can be reduced.

  Next, what is indicated by the light guide 108 in FIG. 5 will be described. In general, a semiconductor ingot has been considered to be unsuitable for electric discharge machining because of its high electrical resistivity.

  However, it is known that irradiation with light having energy higher than the band gap of the semiconductor induces photoelectric conductivity and significantly improves electrical conduction. The inventor of the present application has performed electric discharge machining of SiC using this property, and has so far made a plurality of papers, conference presentations, and patent applications (Patent Document 3).

  As you can see from a simple analysis, when a large electrode is attached to an ingot and electric discharge machining is performed, most of the total resistance is concentrated in a narrow area of the ingot near the wire during electric discharge. This is because the current density in this portion is extremely high. Therefore, the most effective way to improve the electrical conductivity by light irradiation is to irradiate the ingot close to the wire.

  Furthermore, in the light irradiation experiments so far, stabilization of plasma generated by light irradiation is also a significant effect.

  Generally, plasma used in electric discharge machining is called “Z pinch”, and the plasma is extremely unstable. For this reason, even when electric discharge machining is performed, it can be said that the scratches on the face and the wire surface are not constant. However, irradiation with light stabilizes the plasma discharge and improves the processed surface state.

  In this embodiment, the light guide 108 is shown in the drawing, but the light guide needs to be thinner than the cutting margin, and an optical fiber or the like is used.

  Further, a small LED (Light Emitting Diode) has been developed, and in addition to the light guide, an LED may be inserted between the cutting margins, and may be arranged near the portion to be cut and irradiated.

  As the cutting progresses, the place where the facet comes out changes and the place where the cutting process is performed changes, so the light guide that performs light irradiation and the suction port of the suction pipe move accordingly. A control mechanism is provided.

  At the end of the cut, care must be taken when cutting the wafer. The wafer has a constant weight. When the wafer is cut off from the ingot, the uncut portion (the portion that supports the cut wafer) becomes gradually smaller. It has been observed several times in previous experiments that the stress due to gravity applied to the portion increases and, in some cases, the wafer breaks.

  In this embodiment, since the center of the wafer is the last place to be cut off, if the wafer is broken here, it becomes a very serious problem.

  Therefore, in this embodiment, a configuration as shown in FIG. 6 is adopted. A silicon wafer support rod 109 is provided. When there are fewer uncut parts for cutting off the wafer, the rotation of the ingot 102 is stopped, the rotating disk 104 (see FIGS. 4 and 5) is removed, and silicon (Si) is formed under the wafer to support the weight of the wafer itself. ) A wafer support bar 109 is provided to support the load of the wafer. In addition to this configuration, it is needless to say that any method for supporting the weight of the wafer may be used.

  In this way, if the wafer's own weight is supported, a large stress can be prevented from being generated in the uncut portion. For this reason, it can prevent that a crack generate | occur | produces in the wafer center part at the time of cutting off.

  Furthermore, as a method for dealing with such wafer cracking, the entire ingot may be submerged in water or oil.

  This is because buoyancy is generated in the wafer or ingot, which is lower than the stress applied to the uncut portion in the air.

  For example, since the density of silicon is 2.6 g / cm ^ 3 (^ is a power symbol cm ^ 3 is cubic cm) and the density of water is 1.0 g / cm ^ 3, the effective weight is , About 40% lower than in the air, and the stress is reduced accordingly. Furthermore, this stress can be further reduced by using an insulating fluid having a higher density than water. This will be described later.

  If the size of the uncut portion is about 5 mm or less, in the experience so far, the cutting process is performed without rotating the ingot. This is because the wafer support structure is facilitated. At this time, the wire and the ingot are in linear contact with each other, but since the length is as short as 5 mm or less, it is considered that the problem described above does not occur.

  Here, it returns to the problem that the wire is broken again.

  If a thin wire is used in order to narrow the cutting allowance, the problem that the wire is broken (easy to break) will be raised again.

  As a countermeasure, the rotating blade 110 is used without using a wire as shown in FIG. The ingot 102 is rotating.

  Then, since the ingot 102 and the rotary blade 110 are in point contact, plasma is generated in this portion and cutting by electric discharge machining is performed. In this case, it is not necessary to machine the cutting edge like a “round saw”.

  Then, as cutting proceeds, the rotary blade 110 is moved toward the ingot 115 as a whole.

  In this way, you don't have to worry about the wires breaking. A rotating blade with a thickness of about 30 um (micrometer) can be used (no fear of disconnection like a wire). With a 30um wire, it is necessary to keep an eye on the disconnection.

  In the following discussion, it is assumed that both the rotary blade and the ingot are installed in an insulating fluid. Although not shown in FIG. 7, a light guide or the like is provided for irradiating the contact portion with light.

  Furthermore, it is not necessary to bring in a rotating disk for discharging the facets as described in FIG.

  As shown in FIG. 7, it will be important to match the rotational tangent direction of the cut portion of the ingot 102 with the tangential direction of the rotary blade. What is the effect of discharging the facet? It is thought that it will be better than FIG. In the example of FIG. 3, the rotation direction of the uncut portion of the ingot is directed to the upper part of the drawing, but the rotation direction of the rotating disk 104 is. Each direction is different because it goes to the bottom of the figure.

  In such a case, the flow of the insulating fluid becomes complicated, and accordingly the movement of the facet becomes extremely complicated, and it is assumed that the facet is not easily discharged in the same direction. In both cases, since the rotational tangent directions of the contact points are aligned, the facet is discharged naturally.

  Furthermore, when the rotary blade 110 is used, it can be expected that the cutting allowance is narrower than when a wire is used. If a wire is used, the part which supports a wire will be provided in two places on both sides of a cutting part. This part (the part that supports the wire) is an extremely important part in order to obtain processing accuracy. Usually, the accuracy is 1 micron or less. A structure like a pantograph of a train called “power lead” for flowing current at the same time is used.

  However, it is necessary to install the portion supported by these two points in a space where there is no intersection due to the rotation of the ingot, and the distance between the two support points needs to be longer than the cross-sectional diameter of the ingot.

  On the other hand, since a small force is constantly applied to the wire by plasma generated by electric discharge machining, the wire vibrates slightly.

  On the other hand, when the two-point support interval of the wire becomes long, the amplitude of the minute vibration increases even when the same minute force is applied. For this reason, it is assumed that the cutting allowance is widened by this amplitude.

  In fact, when using a copper alloy with a low elastic modulus as the material of the wire and a wire with a high elastic modulus such as molybdenum Mo, the cutting allowance is narrowed by 40% or more even if cutting is performed under the same discharge conditions. Has been observed in experiments.

  This is considered to be because the Mo wire has a small amplitude that vibrates even when an external force due to discharge plasma is applied to the wire.

  On the other hand, in the rotary blade 110 as shown in FIG. 7, it is equivalent to that the cross-sectional direction of the rotary blade 110 is significantly thicker in one direction (the cross-sectional direction of the rotary blade) than the wire having a circular cross section. Therefore, it is considered that the vibration due to such an external force is much smaller than that of the wire. As a result, the cutting allowance becomes narrow. In addition, when cutting off, it is necessary to take measures to support the weight of the wafer as in FIG.

  In this case, only cutting off may be performed using a wire as shown in FIG. 6, or the rotary blade may be used as it is. However, in both cases, the rotation of the ingot is stopped. The round blade may rotate as necessary, and may stop rotating in some cases. Such operating conditions are determined by examining various conditions such as ingots and insulating fluids.

  Further, in order to estimate the stress of the cut portion that has become thinner, a wafer may be managed by inserting a sensor between the wafer support bar and the wafer and measuring the wafer weight.

  Furthermore, although the line blade used in the present invention includes a diamond rotary blade, basically, since it is cut without contact or by plasma, the rotational speed of the rotary blade is significantly slower than that of a diamond saw. It will be. Therefore, I think that it has little influence on the ingot. Moreover, cutting edge processing is not necessary in principle. This is because it is considered that it is sufficient to have a circulation speed that is about the wire feed speed in a conventional experiment. In addition, the material of a rotary blade should just be able to flow electricity fundamentally. Recently, in ELID (Electrolytic In-process Dressing) grinding, a material in which diamond powder is mixed in a conductive grindstone is used, but in this embodiment, this may be used as a rotary blade.

  Next, the structure of the rotary blade 110 in FIG. 7 will be described. As described above, this does not require a structure like a “saw blade”, but if a structure in the blade thickness direction as shown in FIG. 8 is used, electric discharge machining can be performed smoothly. The rotary blade may include a hard material powder such as diamond or silicon carbide. Hard material powder is slightly shaved with silicon.

  In the portion where electric discharge machining is to be performed, electricity needs to flow, so the metal layer needs to be exposed. However, since electric discharge does not occur in the portion of the ingot that has been cut, the surface of the rotary blade 110 is electrically An insulating layer 111 is provided. As the electrical insulating layer 111, the surface of the rotary blade itself may be oxidized to form an insulating layer, or a resist (= insulating agent) may be applied. As the resist (= insulating agent), a resist used in a semiconductor process may be used.

  As a result, the surface of the wafer that has been cut is not damaged by excessive discharge, and at the same time, energy for performing discharge other than cutting is not used without causing excessive damage to the rotary blade 110.

  It should be noted that the parameters such as thickness described in FIG. 8 are values referring to parameters currently being tested, and it is also assumed that the thickness is less than half this.

  In general, the voltage is applied only in a pulsed manner, and can be made thinner than normal electrical insulation.

  In FIG. 8, the electrical insulation layer 113 is thinner than the metal layer 112, and the electrical insulation layer 113 on the surface of the metal layer 112 is peeled off from the rotary blade as a face by the electric discharge machining. As you go, they will peel off together. Therefore, if this electrical insulating layer 113 is thin, it is considered that only this layer does not remain.

  As a structure of such a rotary blade 110, as shown in FIG. 9, a thin portion (slit 114) may be formed partially on the blade surface. This is a groove for discharging the facet, as in “saw blade” and the like. Therefore, the slit width must be wider than the facet dimensions.

  FIG. 10 is a view showing a cross section of the rotary blade 110 provided with slits (grooves) 114. The slit (groove) 114 is configured by removing the electrical insulating layer 113. Therefore, from now on, the thickness of the electrical insulating layer 113 must be thicker than the size of the facet. This is because when the metal layer 112 is thinned, the strength of the rotary blade 110 is lowered. However, in the case where the cutting process is seriously affected, the structure shown in FIG. 10 is required.

It will be apparent from the reason that the electrical insulating layer 113 is first attached that it is necessary to eliminate the electrical insulating layer 113 so that no discharge occurs in this portion.
Therefore, the electrical insulating layer 113 may be partially thinned instead of completely removing the electrical insulating layer 113 in the slit 114 portion.

  The spatial period such as the length of the electrical insulating layer 113 and the slit 114 is comprehensively determined by the rotational speed of the rotary blade 110 and the ingot 102, the pulse interval of the discharge power source, and the like.

  Although the straight slit 114 has been shown as a groove for discharging the facet, it is not always necessary to be constituted by only a straight line.

  Moreover, you may provide many small holes in the whole rotary blade.

  A facet may enter into this small hole by electric discharge machining, and it may be rotated when it comes out of the cross section of the ingot. Of course, such a structure may be used together.

  The rotary blade 110 uses an outer blade (indicating that the ingot is cut by the outer circumference of the rotary blade). Usually, when cutting a semiconductor material ingot such as silicon, the inner blade method is used. There are many cases.

  This will be described with reference to FIG. In this case, the rotary blade 110 becomes large, and cutting is performed inside the rotary blade 110 so as to surround the ingot 102. The ingot 102 rotates in the same manner as in the above embodiment.

  And the rotation direction of the ingot 102 and the rotary blade 110 makes the discharge | emission of a facet easy by aligning the motion of the tangent direction in a contact point in the same direction like illustration.

  Further, when the ingot 102 is cut off, a structure that supports the weight of the wafer, such as a wire or a rotating outer blade, is required. In addition, although not shown in figure, in order to light-irradiate a contact part, it is good also as a structure provided with the light guide. As described above, a slit groove or a small hole may be disposed on the rotary blade for discharging the facet. Alternatively, a suction pipe port may be attached in the direction of face discharge for discharging the facet, and the face may be removed with a filter and then returned to the insulating fluid.

  In the case of the inner blade method, the portion where the ingot does not hit the outside of the rotary blade can be thickened. Therefore, the rotary blade can be rotated stably. In a cutting apparatus that applies a large external force when cutting as compared to electric discharge machining, such as a diamond saw, the stability of the rotary blade is important, and the inner blade method is used. Since it is an electric discharge machining, there is a high possibility that even an outer blade method can sufficiently cope with the operation conditions.

  In the above embodiment, one wire or one rotary blade is used, but it is needless to say that the present invention can be applied to a multi-wire configuration and a configuration using a plurality of rotary blades. FIG. 12 shows an example of a configuration using a plurality of rotary blades. In this embodiment, a plurality of rotary blades 110 are attached to one rotary blade shaft 111, and cutting is performed while rotating the plurality of rotary blades 110 together. In this case, one power source for performing one electric discharge machining is attached to one rotary blade. However, the ingot 102 is common as a ground potential. Thereby, electric discharge machining can be performed more stably than using a single power source.

  Although there are Patent Documents 4 and 5 for cutting a silicon ingot by multi-wire in electric discharge machining, this method uses a single wire and is used to cut the ingot many times. Disconnection is a critical issue. In the configuration shown in FIG. 12, such a problem does not need to be substantially examined, and the cutting process can be performed with peace of mind. In addition, although not shown in figure, performing light irradiation to the part which is performing each electric discharge machining is performed as needed.

  In addition, a suction pipe port is installed at each facet discharge portion, and a control mechanism is provided that controls movement according to the progress of the cutting process. The same applies to the mechanism for irradiating the electric discharge machining portion with light. For wafer cutting (cutting), as shown in FIG. 6, a wafer indicating rod 109 or the like is used. Further, in this example, the outer blade method is used, but it is needless to say that a similar multi-rotating blade may be used as the inner blade method.

  Next, the insulating fluid will be described. In conventional electric discharge machining, pure water or insulating oil is used. A part of gas is used in electric discharge machining such as SiC. When cutting silicon or SiC ingots by electrical discharge machining using gas, mixing argon or gas and reducing gas such as hydrogen or methane in part will give good results in promoting electrical discharge machining. It is coming. This is mainly because the object to be processed is at a high temperature, so that oxidation by oxygen in the air can be prevented.

  When the Freon gas was mixed with the argon gas, the cutting speed was increased several times. This is considered to be because the fluorocarbon gas is decomposed by the plasma, and chemically active fluorocarbon molecules and fluorine ions are generated, which advances the cutting. Such a phenomenon has been observed in plasma etching of wafers and the like, and a chlorofluorocarbon gas may be mixed to increase the etching rate. In this case, it is used as a surface process, and the surface roughness is higher than that of normal electric discharge machining.

  Even in electric discharge machining in liquid, if active chlorofluorocarbon molecules and fluorine ions are generated in plasma, the machining speed can be increased and the surface roughness can be expected to be improved. Now, a solution that can be expected to do this will be described.

An example is shown below. This is a hydrofluoroether (HFE) marketed by Sumitomo 3M Ltd., a product called Novec. This is used as a cleaning or fire extinguishing liquid for electronic components. There are currently four types, and the chemical formula is
C4F9OCH3
C4F9OC2H5
C4F13OCH3
C3HF6-CH (CH3) O-C3HF6
It is.

Boiling point is 61 ℃ to 131 ℃,
Density is 1.43g / cm ^ 3 to 1.66g / cm ^ 3
There is.

  Therefore, buoyancy greater than water acts on the ingot. Since the electrical resistivity is almost equal to or higher than that of water, it can be used for electric discharge machining. Since the relative dielectric constant is about 6-7, it is lower by one digit or more than water, so even with a method using a rotary blade, it is possible to suppress an increase in current that is not subjected to electric discharge machining due to an increase in floating capacitance due to an increase in the facing area Yes (see the Sumitomo 3M website for details).

  Alternatively, a fluorine-based inert liquid called perfluorocombound (trade name: fluorine-based inert liquid, fluorinate) may be used (http://www.mmm.co.jp/emsd/product/pdt_01_02.html). Compared with water, its electrical resistivity is extremely high and its dielectric strength is high. For this reason, a high voltage can be applied. Moreover, since the relative permittivity is 2 or less, it is 1/4 that of Novec and 1/40 that of water. Contributes to reducing power consumption.

  Such a hydrofluoroether is used as an insulating fluid. In addition, in order to keep such liquid characteristics constant during electric discharge machining, a device for controlling the liquid temperature is provided. In addition, in order to use an insulating fluid stably, it is made to take the structure which seals an electric discharge machining apparatus in order to filter a facer with a filter and to prevent the spreading | diffusion to air | atmosphere. The filter also has a function of adsorbing HFE decomposition products due to plasma generation. This product has low human toxicity and is approved for use as a digestive agent in the event of a fire. The ozone depletion coefficient, which has become a hot topic as a global environmental problem, is zero, and its global warming potential is lower than that of fluorocarbon gases that have been used in electronic parts so far. It is good also as a structure which makes the part with an insulating fluid airtight, and prevents the gas from an insulating fluid from diffusing to air | atmosphere.

  There are insulating liquids having a boiling point of 100 ° C. or lower, and such liquids also have a high vapor pressure. If the entire device is released and used, such as when water or oil is used, a large amount of insulating liquid gas is mixed into the atmosphere. In order to avoid this, it is desirable to make the whole apparatus a closed system or apply a negative pressure.

  Furthermore, in the present embodiment, a configuration in which a refrigerating machine head is provided in order to re-condense the gas from the liquid in a case surrounding the apparatus may be provided.

  Another embodiment of the present invention will be described.

  FIG. 13 is a diagram showing the configuration of another embodiment of the present invention. In the example shown in FIG. 13, a wire for cutting flows along a rotating disk made of an insulating material, thereby cutting the ingot. In FIG. 13, the wire is sent from the top and the direction in which the wire is sent through the pulley changes, and turns along the rotating disk to perform electric discharge machining. Then, it is sent out. And ceramic etc. are used as an insulator which makes a disk. In addition, grooves and the like are formed on the circumference of the disk so that the rotating disk can easily guide the wire. If it does in this way, a rotary blade will not be worn out by discharge.

  Moreover, even if the ingot becomes large and the distance between the guides supporting the wire becomes long, the wire is less likely to vibrate. Furthermore, since the rotary blade is not conductive, it is not necessary to insulate the surface. Toxic gas may be generated when processing using chlorofluorocarbon liquid.

  In the present embodiment, an apparatus for collecting this toxic gas without leaking into the atmosphere is installed. And after collection | recovery, it is sent to a toxic gas processing process.

  FIG. 14 is a diagram showing the configuration of this embodiment. In this embodiment, the discharge wire is formed into a ribbon shape. The cross section of the discharge wire of the electric discharge machine is generally a circle. In the case of a circle, it can be bent in either direction. Since silicon ingots and SiC ingots are expensive, it is preferable that the cutting margin is narrow. For this reason, disconnection frequently occurs when a thin wire is used. Therefore, it is required to use a wire that has a narrow cutting margin and is difficult to break. One solution to this problem is to use ribbon-shaped wires.

  In the example shown in FIG. 14, the ribbon cross section has a thickness of 50 microns (μm) but a width of 300 microns (μm). Since the side corresponding to the cutting margin is 50 microns, the cutting margin is narrow and the cross section is large, so that the wire is difficult to cut. The use of such a ribbon-shaped wire solves the above problem.

  However, the wide 300 micron side faces the ingot for cutting. For this reason, if a discharge occurs here, the cutting allowance becomes wide, so that a measure for attaching an insulating layer to the surface on the 300 micron side may be required.

  FIG. 15 is a sectional view showing an example of the countermeasure. Enamel or the like is used as a material for the insulating layer. Since it becomes an insulating layer simply by coating the surface with a thickness of several microns, it is easy to process. In addition, since it is considered that this insulating layer is automatically removed when the ribbon is thinned due to damage caused by electric discharge machining, there is no major problem in electric discharge machining.

  Further, when the electric discharge machining is performed, the wire is also damaged and decreases, but as shown in FIG. 15, the place where the arc plasma is generated is on the 50 micron side, so that it can be used any number of times. Ribbon processing is more expensive than wire processing, and thus, it is preferable to use it many times in terms of economy.

  FIG. 16 is a diagram showing an example of ribbon processing as another embodiment of the present invention. In general electric discharge machining, the wire is one through that is thrown through the electric discharge machining portion only once.

  On the other hand, in the present embodiment, as shown in FIG. 15, discharge occurs on the 50 micron side, and even if damage occurs, it is still as thick as 300 microns. In the example shown in FIG. 16, the wire (ribbon) is circulated and the ingot is fixed. However, the ingot may be rotated. By rotating the ingot, the contact portion with the ribbon becomes a point, facilitating electrical discharge machining.

  Further, such a structure is further improved in characteristics by changing the ribbon material from a copper alloy or the like to tungsten or molybdenum. In the case of a copper alloy, once a discharge occurs, the wire is severely damaged. In general electric discharge machining, tungsten and molybdenum, which are refractory metals, are used in special cases. When tungsten or the like, which is a refractory metal, is used, the surface damage is small compared to copper alloy wires.

  Also in this embodiment, when a refractory metal is used as the ribbon material, the cutting process can be stably performed even if it is passed through many.

  In the case of the ribbon shape, since the cross-sectional area becomes large, the tension can be increased. The positioning accuracy can be increased when cutting. Alternatively, the cutting allowance can be prevented from spreading due to wire vibration.

  It is desirable to join both ends of the ribbon of this embodiment. In general, in the case of a wire, special attention is not paid to the end portion because it is one through. In some band saws and the like, both ends are joined to form a ring. The same applies to a diamond saw for cutting an ingot.

  Note that the joint portion may not have sufficient strength. Therefore, during electrical discharge machining, when the joint is in the ingot, control is performed to temporarily stop the electrical discharge. When the joint is inside the ingot, no cutting process is performed. Control is performed so that the relative position between the ingot and the ribbon is not temporarily changed.

  As a modification of the present embodiment, when it is difficult to join both ends of the ribbon, the wire feeding mechanism of the electric discharge machining apparatus is improved, and even when both ends of the ribbon are not joined, Of course, a mechanism for feeding a wire (ribbon) in the same situation may be provided.

  Further, when no joint is provided, cutting is performed by reciprocating the ribbon as shown in FIG. In this case, refractory metal is used because it passes through the same place many times. The ribbon is straight and does not have a bent portion as shown in FIG. For this reason, there is little fatigue deterioration. However, tension is applied to make the ribbon straight.

  Further, it is necessary to provide a guide for guiding in a straight line, and FIG. 17 shows an example in which the ingot is rotated in accordance with the movement of the ribbon in order to make the cutting portion one point (dot shape). . The rotation is a reciprocating motion. Such a configuration facilitates cutting control and facilitates face discharge. In addition, you may control to discharge and to cut | disconnect, when moving to one direction. In FIG. 17, discharge may be performed only when the ribbon moves from right to left, and discharge may be stopped when the ribbon moves from left to right. On the other hand, the ingot may be controlled to rotate in the same direction. In this case, rotation is performed from right to left.

  Of course, the cutting apparatus using the ribbon can be applied to an electric discharge machining apparatus that includes a plurality of ribbons and simultaneously performs wafer processing using the plurality of ribbons.

  It should be noted that the disclosures of the above patent documents are incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiments and examples can be changed and adjusted based on the basic technical concept. Various combinations and selections of various disclosed elements are possible within the scope of the claims of the present invention. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

DESCRIPTION OF SYMBOLS 101 Wire 102 Ingot 103 Ingot rotating shaft 104 Rotating disk 105 Rotating disk shaft 106 Cutting allowance 107 Pipe 108 Light guide 109 Silicon wafer support rod 110 Rotating blade 111 Rotating blade shaft 112 Metal layer 113 Electrical insulating layer 114 Slit

Claims (41)

  When cutting an ingot and cutting a wafer, the cutting apparatus characterized by rotating the said ingot centering | focusing on the rotating shaft orthogonal to a cut surface, and cut | disconnecting the said ingot by electric discharge machining.   The cutting apparatus according to claim 1, wherein the ingot is cut by electric discharge machining using a wire or a rotary blade.   The cutting apparatus according to claim 1, wherein a feeding direction of the wire and an ingot rotation direction at a contact portion between the wire and the ingot are forward directions.   The cutting device according to any one of claims 1 to 3, further comprising means for discharging a facet coming out from the cutting portion of the ingot.   The cutting device according to claim 4, further comprising a rotating disk for discharging the facet of the ingot at a cutting position by the wire electric discharge machining.   The said rotating disk rotates in the rotation direction which discharges the face of the said ingot in the cutting allowance of the said ingot, and discharges the face of the said ingot of the cutting location by the said wire electric discharge machining. Cutting device.   The cutting apparatus according to any one of claims 3 to 6, further comprising a suction unit for discharging the facet.   The cutting apparatus according to any one of claims 1 to 7, further comprising a support member that supports a lower portion of a wafer cut from the ingot.   The cutting apparatus according to claim 8, wherein the support member supports the ingot and the wafer while rotating.   The cutting device according to any one of claims 1 to 9, further comprising means for irradiating the contact portion between the wire or the rotary blade and the ingot.   The cutting apparatus according to claim 2, wherein the rotary blade is an outer blade or an inner blade system.   The cutting device according to claim 11, wherein a slit is provided on the surface of the rotary blade.   The rotary blade has an electrical insulating layer on the front surface and the back surface of a metal layer, and the electrical insulating layer is removed from the slit portion or is set thinner than the portion other than the slit portion. Item 13. The cutting device according to Item 12.   The cutting apparatus according to claim 2, comprising a plurality of rotary blades having a common rotation axis.   The cutting device according to any one of claims 1 to 14, wherein electric discharge machining is performed in an insulating fluid in which active chlorofluorocarbon molecules and fluorine ions are generated in plasma.   The cutting device according to claim 14, wherein the rotary blade includes a hard material powder.   The cutting device according to claim 14, wherein a power source is individually connected to each of the plurality of rotary blades.   The cutting device according to any one of claims 1 to 17, wherein a part including an insulating fluid to be subjected to electric discharge machining is hermetically sealed to prevent diffusion of gas from the insulating fluid into the atmosphere.   19. The cutting apparatus according to claim 18, further comprising a cooling unit that controls a temperature of the insulating fluid.   20. The cutting device according to claim 19, further comprising means for solidifying the gas from the insulating fluid again.   21. The cutting apparatus according to claim 1, wherein the ingot is processed into a columnar shape so that a cross section of the ingot has the same diameter before the wafer is cut out.   When cutting an ingot and cutting a wafer, the cutting method characterized by rotating the said ingot centering on the rotating shaft orthogonal to a cut surface, and cutting the said ingot by electric discharge machining.   The cutting method according to claim 22, wherein the ingot is cut by electric discharge machining using a wire or a rotary blade.   The cutting method according to claim 22 or 23, wherein a feeding direction of the wire and an ingot rotation direction at a contact portion between the wire and the ingot are forward directions.   The cutting method according to any one of claims 22 to 24, wherein a facet coming out from a cutting portion of the ingot is discharged.   26. The cutting method according to claim 25, wherein a face of the ingot at a cutting position by the wire electric discharge machining is discharged with a rotating disk.   27. The cutting method according to claim 25 or 26, wherein suction is performed to discharge the facet.   The cutting method according to any one of claims 22 to 27, wherein a lower part of a wafer to be cut from the ingot is supported.   A cutting device characterized in that a wire is sent along a rotary blade made of an insulating material, the rotary blade is rotated around a rotation axis perpendicular to the cutting surface, and the ingot is cut by electric discharge machining.   30. The cutting device according to claim 29, wherein a feeding direction of the wire and an ingot rotation direction at a contact portion between the wire and the ingot are forward directions.   When cutting an ingot and cutting a wafer, the cutting apparatus characterized by rotating the said ingot centering | focusing on the rotating shaft orthogonal to a cut surface, and cut | disconnecting the said ingot by electric discharge machining.   The cutting device according to claim 15, further comprising means for removing toxic gas generated by electric discharge machining in a fluorocarbon insulating fluid.   The cross-sectional shape of a wire for electric discharge machining is a ribbon shape, and an insulating material is provided on the surface on the long side of the cross-section of the wire surface, according to any one of claims 2, 3, and 30. The cutting device as described.   A cutting device characterized in that a cross-sectional shape of a wire for electric discharge machining is a ribbon shape, and an insulating material is provided on a surface on a long side of the cross-section of the wire surface.   35. The ingot is cut by electric discharge machining using the wire or rotary blade, the ingot is rotated around a rotation axis orthogonal to a cutting plane, and the ingot is cut by electric discharge machining. Cutting device.   36. A cutting device according to claim 34 or 35, wherein the wire comprises a refractory metal.   37. The cutting device according to any one of claims 34 to 36, wherein discharge occurs on the short side of the cross-section of the ribbon-shaped wire.   The cutting device according to any one of claims 34 to 37, wherein both end portions of the wire having a ribbon-shaped cross section are joined.   39. The cutting device according to claim 38, wherein the discharge is stopped at the joint at both ends of the wire.   39. The cutting device according to claim 38, wherein the ribbon-shaped wire is circulated, and discharge is stopped at the joints at both ends of the wire.   41. The cutting apparatus according to claim 40, wherein the ribbon-shaped wire feed direction is one direction with respect to the cutting object and / or the opposite direction, and discharge is performed in one direction of the wire feed direction.

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