JP5962614B2 - Work cutting method and wire saw - Google Patents

Description

  The present invention relates to a cutting method and a wire saw for detecting wear or peeling of a resin layer of a resin-coated wire used for cutting a workpiece such as a semiconductor ingot by a wire saw.

  One of the cutting devices for cutting hard and brittle materials such as semiconductor ingots into thin plate wafers is a wire saw. The wire saw forms a wire row with wires wound at a predetermined pitch, and reciprocates the wires at high speed. The workpiece is cut into a number of wafers by pressing the workpiece against the wire row while supplying the machining fluid to each contact portion between the workpiece and the wire.

  Patent Document 1 describes a resin-coated wire in which an outer peripheral surface of a base wire is coated with an abrasive carrier resin film as a wire used for cutting a workpiece. In Patent Document 1, if this resin-coated wire is used, since the abrasive grains (free abrasive grains) in the working fluid bite into the abrasive carrier resin film, the wire and the workpiece are in stable contact with the abrasive grains. It is stated that it can be pulled into the part.

JP 2006-179677 A JP 2003-004646 A

  In a wire saw using a resin-coated wire, the resin layer on the surface of the resin-coated wire may be worn or peeled during the cutting of the workpiece. If the resin layer is left worn or peeled off, the resin-coated wire is broken during the cutting of the workpiece. When the breakage of the resin-coated wire occurs, it takes a long time to recover, and the shape quality of the cut wafer is adversely affected.

  Patent Document 2 describes an inspection apparatus for confirming the surface state of a fixed abrasive wire with a CCD camera in the production inspection of a resin bond wire in which abrasive particles are fixed to a peripheral surface of a base wire with a resin. It is described that this inspection apparatus can detect the peeling of the resin bond layer of the resin bond wire. Furthermore, it is described that by installing this inspection device in a wire saw, it is possible to detect sharpness reduction or disconnection of the resin bond wire.

  In the inspection apparatus described in Patent Document 2, an abnormality such as abrasion or peeling of the resin bond layer of the resin bond wire can be detected by installing the inspection apparatus between the wire guides (wire row) and the winding bobbin. . However, when the forward / reverse cycle time in the running direction of the resin bond wire is short, the wear or peeling part of the resin bond layer reciprocates only between the wire guides, and the resin bond wire Disconnection occurs. In addition, the CCD camera which is an abnormality detection means of this inspection apparatus is not suitable for an environment in which a large amount of slurry mist is generated during workpiece cutting because it is vulnerable to dirt.

  The present invention has been made in view of the above-described problems, and is capable of detecting in advance a disconnection of a resin-coated wire by sensitively detecting wear or peeling of the resin layer of the resin-coated wire. It is an object to provide a method and a wire saw.

  In order to achieve the above object, according to the present invention, a wire row is formed by a wire that is spirally wound between a plurality of wire guides and reciprocally travels in an axial direction, and the wire is a resin on the surface of a base wire. A method of cutting a workpiece by pressing the workpiece against the wire row and cutting the workpiece while supplying a machining fluid to a contact portion between the workpiece and the wire using a resin-coated wire coated with an eddy current, A measuring step of periodically measuring a voltage value of the eddy current type displacement sensor detected by setting the wire displacement sensor to be close to the wire row and detecting the wire after contacting the workpiece; It has the determination process which determines whether abrasion or peeling of the resin layer has occurred from the voltage value, and the determination process uses the voltage value measured in the measurement process and the moving average value of the voltage value. The difference percentage was calculated by the following formula (1), and the calculated difference percentage was out of the range of the threshold value determined from the standard deviation of the difference percentage when the resin layer had no wear determined in advance. The method for cutting a workpiece is characterized in that it is determined that the resin layer is worn or peeled.

  With such a cutting method, wear and delamination of the resin layer of the resin-coated wire can be detected sensitively, so appropriate measures such as interrupting the cutting of the workpiece before the breakage of the resin-coated wire occurs. Can take.

  Further, according to the present invention, the wire row formed by the wire traveling in the axial direction wound spirally between the plurality of wire guides, and the processing for supplying the processing liquid to the contact portion between the workpiece and the wire A liquid supply mechanism; and a workpiece feeding means for pressing the workpiece against the wire row by pressing the workpiece while holding the workpiece, and the wire is a resin-coated wire in which a surface of a base wire is coated with a resin The workpiece is held by pressing the workpiece held by the workpiece feeding means against the wire row while supplying the machining fluid to the contact portion between the workpiece and the wire from the machining fluid supply mechanism. An eddy current type displacement sensor that periodically detects a voltage value using the wire after contact with the workpiece as a measurement object; Determining means for determining whether the resin layer is worn or peeled from a voltage value, wherein the eddy current displacement sensor is disposed so as to be close to the wire row; The percentage difference is calculated by the following formula (1) using the moving average value of the voltage value, and the calculated percentage difference is determined from a standard deviation of the percentage difference when the resin layer is not worn in advance. The wire saw is characterized in that it is determined that the resin layer is worn or peeled when it falls outside the range of the threshold value.

  With such a wire saw, it is possible to sensitively detect the wear and delamination of the resin layer of the resin-coated wire, and therefore take appropriate measures such as interrupting the cutting of the workpiece before the disconnection of the resin-coated wire occurs. Will be able to.

  With the workpiece cutting method and wire saw of the present invention, appropriate measures such as detecting the abrasion and peeling of the resin layer of the resin-coated wire sensitively and interrupting the workpiece cutting before the breakage of the resin-coated wire occurs. Can take. Moreover, the deterioration of the shape of the wafer can be prevented by preventing disconnection of the resin-coated wire during workpiece cutting.

It is the schematic which showed an example of the wire saw of this invention. It is the perspective view which showed an example of the resin coating wire which the wire saw of this invention has. It is a SEM photograph which shows an example of the resin coating wire to which the abrasive grain has adhered to the surface previously. It is a figure which shows an example of the change of the difference percentage when the disconnection of the resin-coated wire occurs. It is a figure which shows an example of the change of the voltage value which an eddy current type displacement sensor detects.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to this.
When the workpiece is cut by the wire saw, wear or peeling of the resin layer of the resin-coated wire used for cutting occurs. If the use of the resin-coated wire that is worn or peeled off is continued, the resin-coated wire is disconnected. When the resin-coated wire is disconnected during the cutting of the workpiece, there is a problem that the shape of the wafer after cutting is significantly deteriorated.

  Therefore, the present inventor has intensively studied to solve such problems. As a result, the inventors have conceived that wear and delamination of the resin layer can be detected by utilizing the change amount of the difference percentage of the voltage value measured by the eddy current displacement sensor as described above, and the present invention has been completed.

  That is, the present inventor conceived of using an eddy current type displacement sensor for detection of wear and peeling of the resin layer of the resin-coated wire, and performed the following considerations. In the eddy current displacement sensor, the detected voltage value changes according to the distance to the metal to be measured and the size of the metal. Further, if there is a non-metal such as resin between the eddy current displacement sensor and the measurement object, the detected voltage value is different from that when there is no non-metal such as resin.

  Therefore, the eddy current displacement sensor detects a different voltage value between a metal base wire alone and a resin-coated wire in which the base wire is coated with a resin, and the detected voltage value is a resin layer of the resin-coated wire. It also changes depending on the state. The inventor has come up with the idea of detecting wear and delamination of the resin layer of the resin-coated wire during workpiece cutting by utilizing the change in the voltage value.

Therefore, the present inventor considered that the voltage value detected by the eddy current displacement sensor in the cutting in which the resin layer of the resin-coated wire is not worn or peeled off, and that the resin-coated wire is broken due to the wear of the resin layer We compared the voltage values detected by the eddy current displacement sensor during cutting, and examined as follows. FIG. 5 shows an example of voltage values detected when the above-described two types of cutting are performed.
As shown in FIG. 5, in the cutting in which the resin layer is not worn and peeled off, the voltage value has a small fluctuation width and a stable waveform. On the other hand, it can be seen that in the cutting where the resin layer is worn and the resin-coated wire is disconnected, an unstable waveform in which the swing width gradually increases is drawn. From the above, it has been found that it is sufficient to take measures for avoiding the disconnection of the resin-coated wire when the deflection width becomes larger than a certain value.

  Hereinafter, the workpiece cutting method and the wire saw according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these.

  First, the wire saw of this invention is demonstrated using FIGS. 1-3. As the resin-coated wire used for cutting, either a resin-coated wire 3 in which abrasive grains are not fixed in advance on the surface or a resin-coated wire 3 ′ in which abrasive grains are fixed in advance on the surface can be used. Here, the case where the resin-coated wire 3 in which abrasive grains are not fixed to the surface in advance is used will be described.

  As shown in FIG. 1, a wire saw 1 of the present invention includes a wire row 4 formed by a resin-coated wire 3 spirally wound between a plurality of wire guides 2 and traveling in an axial direction, and a workpiece W at the time of cutting. A machining fluid supply mechanism 5 that supplies a machining fluid to a contact portion with the resin-coated wire 3, a workpiece feeding unit 6 that presses the workpiece W while holding the workpiece W, and tension is applied to the resin-coated wire 3. It is comprised by the tension | tensile_strength provision mechanisms 7 and 7 'for providing.

  As shown in FIG. 2, the resin-coated wire 3 is obtained by coating the surface of the base wire 13 with a resin that does not contain abrasive grains. As the base wire 13 constituting the resin-coated wire 3, for example, a piano wire having a diameter of 40 to 200 μm is used, and the resin layer 14 is entirely formed on the outer peripheral surface of the piano wire. As a resin for forming the resin layer 14 on the surface of the base wire 13, for example, a phenol resin, a polyamide resin, an epoxy resin, a urethane resin, or the like can be used. The thickness of the resin layer 14 is preferably in the range of 0.5 to 15 μm. The resin layer 14 can draw the abrasive grains between the workpiece W and the resin-coated wire 3 by causing the abrasive grains in the working fluid sprayed onto the resin-coated wire 3 to bite into the surface of the resin layer 14.

  The resin-coated wire 3 is fed from one wire reel bobbin 8 and enters the wire guide 2 via a traverser and a tension applying mechanism 7 including a constant torque motor, a dancer roller (dead weight), and the like. The resin-coated wire 3 is wound around a wire reel bobbin 8 'through another tension applying mechanism 7'. Further, the tension applied to the resin-coated wire 3 by the tension applying mechanisms 7 and 7 ′ is limited to the tensile strength of the base wire 13 or less, and is preferably in the range of 40 to 70% of the tensile strength of the base wire 13.

  The wire guide 2 is a roller in which a polyurethane resin is press-fitted around a steel cylinder and grooves are cut at a predetermined pitch on the surface thereof, and the resin-coated wire 3 wound by the drive motor 12 is axially moved. It is possible to travel back and forth. Here, when the resin-coated wire 3 is reciprocated, the travel distance in one direction is not the same as the travel distance in both directions of the resin-coated wire 3, but a new wire is supplied. Try to be long. In this way, a new line is supplied in the direction of a long travel distance while reciprocating the resin-coated wire 3.

  The machining fluid supply mechanism 5 includes a slurry chiller 9, a slurry tank 10, a nozzle 11, and the like. The nozzle 11 is disposed above the resin-coated wire 3 wound around the wire guide 2. The nozzle 11 is connected to a slurry tank 10, and the processing liquid is stirred in the slurry tank 10 and the temperature is adjusted by the slurry chiller 9, and then can be supplied from the nozzle 11 to the resin-coated wire 3. Then, the machining fluid rides on the wire row 4 and is sent to the contact portion between the workpiece W and the wire row 4. Further, the supplied machining fluid is returned to the slurry tank 10 for circulation.

  The working fluid is composed of abrasive grains and coolant, and for example, silicon carbide abrasive grains or diamond abrasive grains can be used as the abrasive grains. In particular, in order to smooth the cut surface of the workpiece W, it is desirable to use diamond abrasive grains. In addition, abrasive grains having an average particle diameter of 2 to 15 μm can be used. A water-soluble or oil-based coolant can be used as the coolant, and it is particularly preferable to use a glycol-based coolant, which is a typical water-soluble coolant. And the processing liquid whose abrasive grain concentration is 0.5-30 mass% and whose temperature is 5-30 degreeC can be used.

  Here, the wire saw 1 of the present invention includes an eddy current displacement sensor 15 and a determination means 16 at a position close to the wire row 4. The eddy current displacement sensor 15 periodically detects a voltage value with the resin-coated wire 3 after contacting the workpiece W as a measurement target. And the detected voltage value is sent to the determination means 16, and the determination means 16 determines the presence or absence of generation | occurrence | production or abrasion of the resin layer 14 based on this voltage value.

  Specifically, the determination of the presence or absence of occurrence of wear or delamination first calculates the percent difference by the following equation (1) using the voltage value detected by the determination means 16 and the moving average value of the voltage value. Next, the calculated difference percentage is compared with a threshold range determined from a standard deviation of the difference percentage when the resin layer 14 is not worn and peeled in advance. When the calculated difference percentage is outside the threshold range, the determination unit 16 determines that the resin layer 14 is worn or peeled off. The range of this threshold can be, for example, within 3 times the standard deviation of the percentage difference when there is no wear and delamination.

  With such a wire saw, the wear and delamination of the resin layer 14 of the resin-coated wire 3 are sensitively detected, and appropriate measures are taken such as interrupting the cutting of the workpiece before the breakage of the resin-coated wire 3 occurs. Will be able to. For example, when the wear or delamination of the resin layer 14 is detected, the operation of the wire saw is automatically stopped and the operator is called by an operator call or the like. Then, the operator can take measures such as manually feeding the resin-coated wire 3 by a predetermined distance to draw out a new line and not using the worn portion or the peeled portion of the resin layer 14 for processing the workpiece W.

Next, the wire saw 1 provided with the resin-coated wire 3 ′ having abrasive grains fixed in advance on the surface will be described.
As shown in FIG. 3, the resin-coated wire 3 ′ is obtained by fixing abrasive grains 17 with a resin layer 14 ′ on the outer peripheral surface of the base wire.
As a base wire constituting the resin-coated wire 3 ′, a piano wire having a wire diameter of 40 to 200 μm can be used. The material of the resin layer 14 'is alkyd resin, phenol resin, formalin resin, polyurethane resin, polyester resin, polyimide resin, epoxy resin, melamine resin, urea resin from the viewpoint of elastic modulus, softening temperature, moldability, and physical characteristics. Use of unsaturated polyester resin, acrylic resin, polyesterimide resin, polyamideimide resin, polyester urethane resin, bismaleimide resin, bismaleimide triazine resin, cyanate ester resin, polyetherimide, polyparabanic acid, aromatic polyamide, etc. Is preferred. As the abrasive grains 17, silicon carbide abrasive grains, cubic boron nitride abrasive grains, diamond abrasive grains, and the like can be used. In consideration of wear resistance in particular, it is preferable to use diamond abrasive grains. The abrasive grains 17 having an average particle diameter of 2 to 30 μm can be used, and the resin layer 14 is preferably ¼ to ¾ of the average particle diameter of the abrasive grains 17 to be used.

  As the coolant for the working fluid, tap water or water-soluble coolant can be used. It is preferable to use a water-soluble glycol coolant in terms of wafer quality and workability. The temperature of the working fluid can be in the range of 5-30 ° C. Moreover, the tension | tensile_strength applied to resin-coated wire 3 'is limited to the tensile strength or less of a base wire, Preferably the range of 40 to 70% of tensile strength is preferable. The apparatus configuration other than these can be the same as when using a resin-coated wire in which abrasive grains are not fixed to the surface in advance.

  If it is such, like the wire saw 1 provided with the resin-coated wire 3 on which the abrasive grains are not fixed in advance on the surface, the wear and delamination of the resin layer 14 ′ of the resin-coated wire 3 ′ are sensitively detected. Thus, it is possible to take appropriate measures such as interrupting the cutting of the workpiece before the disconnection of the resin-coated wire 3 ′ occurs.

Next, the workpiece cutting method of the present invention will be described. Here, a case where a wire saw 1 including a resin-coated wire 3 in which abrasive grains are not fixed in advance on the surface of the present invention as shown in FIG. 1 will be described.
First, the workpiece W is held by the workpiece feeding means 6. The resin-coated wire 3 is reciprocated in the axial direction while applying tension by the tension applying mechanisms 7 and 7 '. At this time, the traveling speed of the resin-coated wire 3 can be set to 300 m / min or more. Next, the workpiece W is relatively pushed down by the workpiece feeding means 6, and the workpiece W is pressed against the wire row 4 to cut the workpiece W into a wafer shape. At this time, the workpiece cutting speed can be set to 0.02 to 0.35 mm / min.

  Here, the workpiece cutting method of the present invention includes a measurement step of periodically measuring the voltage value of the eddy current displacement sensor 15 detected with the resin-coated wire 3 after contact with the workpiece W as a measurement target, It has the determination process which determines whether abrasion or peeling of the resin layer has generate | occur | produced from the value. In this determination step, the percent difference is calculated by the above formula (1) using the voltage value measured in the measurement step and the moving average value of the voltage value, and the wear of the resin layer 14 that is calculated in advance is calculated. When it is outside the range of the threshold value determined from the standard deviation of the difference percentage when there is no difference, it is determined that the resin layer is worn or peeled off.

  With such a cutting method, appropriate measures such as detecting the abrasion and peeling of the resin layer 14 of the resin-coated wire 3 sensitively and interrupting the cutting of the workpiece before the disconnection of the resin-coated wire 3 occurs. Can take. For example, when the wear or delamination of the resin layer 14 is detected, the operation of the wire saw is automatically stopped and the operator is called by an operator call or the like. And an operator can take countermeasures, such as drawing out a new line by sending the resin-coated wire 3 by a certain distance by manual operation and not using a worn part or a peeled part of the resin layer 14 for processing the workpiece W.

  Further, even when the workpiece W is cut using the resin-coated wire 3 ′ whose abrasive grains are fixed to the surface in advance, the same effect as the cutting method of the present invention described above can be obtained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples of the present invention, but the present invention is not limited to these.

(Example)
Using the wire saw of the present invention as shown in FIG. 1, the workpiece was cut according to the workpiece cutting method of the present invention. As a workpiece to be cut, as shown in Table 1, rod-shaped single crystal silicon having dimensions of a wire travel direction W: 80 mm, a wire row direction D: 100 mm, and a workpiece feed direction H: 25 mm was used. As the resin-coated wire, a wire on which the abrasive grains were not fixed in advance was used. This resin-coated wire was used by coating a resin layer with a thickness of 6 μm on the entire outer periphery of a base wire having a diameter of 0.13 mm.

  The tension of the resin-coated wire of the wire saw was 30 N, the new wire supply amount was 3 m / min, the forward reversal cycle in the traveling direction in the reciprocating traveling was 60 sec, and the average linear velocity was 650 m / min. The workpiece feed speed was 0.10 mm / min. As a working fluid, a diamond abrasive grain having an average abrasive grain size of 5.5 μm was prepared and used in a glycol-based water-soluble coolant so as to have an abrasive grain concentration of 5 mass%. Further, the flow rate of the processing liquid was set to 80 mL / min per one resin-coated wire. The flow rate of the working fluid was set to a higher flow rate than usual in order to perform the example under conditions where the resin layer was easily worn or peeled off.

Moreover, the measurement interval of the voltage value of the eddy current type displacement sensor whose measurement object is the resin-coated wire after contact with the workpiece was 10 seconds. The moving average value of the voltage values was calculated using the voltage values for the past 19 points (the past 3 minutes) from the detected voltage values.
In order to obtain the standard deviation σ of the difference percentage of the resin layer without wear or delamination, the voltage difference percentage of the resin layer without wear or delamination was calculated in advance many times. The deviation σ was about 0.23% on average. From this value, the threshold range of the percentage difference was determined to be within 3σ, that is, within ± 0.7%. When the difference percentage calculated from the detected voltage value and the moving average value falls outside this threshold range, the determination means determines that wear or delamination has occurred in the resin layer, automatically stops the wire saw, and performs cutting. Set to cancel. The determination means is an arithmetic unit and is provided in the wire saw.

The workpiece was repeatedly cut, and after automatically stopping the wire saw, three resin-coated wires that contributed to the cutting were sampled, and the diameter was measured with a micrometer. The wear amount of the wire resin layer was calculated from the difference between the diameter measured with a micrometer and the wire diameter before use.
The above cutting was repeated 10 times, and the average wear amount of the resin layer of the resin-coated wire was calculated. As a result, the average wear amount of the resin layer was 5.4 μm, and since the thickness of the resin layer before use was 6 μm, it was possible to detect the state where the resin layer was almost worn away and to automatically stop the wire saw. It will be. In the embodiment, the resin-coated wire has never been broken, and it is possible to prevent the resin-coated wire from being broken by determining the presence or absence of wear or peeling before the wire break occurs and taking appropriate measures. Was confirmed.

(Reference example)
FIG. 4 shows an example of a measured value of the difference percentage when the resin-coated wire is disconnected. As shown in FIG. 4, the percentage difference shows a value exceeding the threshold value of 0.7% at about 23 minutes from the start of cutting. Then, if the workpiece is continuously cut as it is, the resin-coated wire is broken around 30 minutes. For example, when the cutting method of the embodiment is applied in the case of FIG. 4, it is determined that the resin layer is worn or peeled off at about 23 minutes from the start of cutting, and the wire saw is automatically stopped.

(Comparative example)
The workpiece was cut under the same conditions as in the example except that a wire saw without an eddy current displacement sensor and determination means was used.
As a result, the occurrence of wear or peeling of the resin layer could not be detected, and the cutting was continued in a state where the wear or peeling of the resin layer was occurring, so that the resin-coated wire was broken.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

DESCRIPTION OF SYMBOLS 1 ... Wire saw, 2 ... Wire guide, 3, 3 '... Resin coated wire,
4 ... wire row, 5 ... working fluid supply mechanism, 6 ... work feeding means,
7, 7 '... tension applying mechanism, 8, 8' ... wire reel bobbin,
9 ... Slurry chiller, 10 ... Slurry tank, 11 ... Nozzle,
12 ... Drive motor, 13 ... Base wire, 14, 14 '... Resin layer,
15 ... Eddy current type displacement sensor 16 ... Determination means 17 ... Abrasive grains
W ... Work.

Claims (2)

A wire row is formed by a wire that is reciprocated in an axial direction wound spirally between a plurality of wire guides, and the wire uses a resin-coated wire in which a resin is coated on the surface of a base wire, and the workpiece, the wire, A workpiece cutting method of cutting the workpiece by pressing the workpiece against the wire row while supplying a machining fluid to the contact portion of
A measurement step of installing an eddy current displacement sensor close to the wire row and periodically measuring the voltage value of the eddy current displacement sensor detected by measuring the wire after contacting the workpiece. And a determination step for determining whether the resin layer is worn or peeled from the voltage value, and the determination step uses the voltage value measured in the measurement step and a moving average value of the voltage value. The difference percentage is calculated by the following formula (1), and the calculated difference percentage is out of the threshold range determined from the standard deviation of the difference percentage when the resin layer is not worn in advance. A workpiece cutting method, wherein it is determined that the resin layer is worn or peeled off.

A wire array formed by wires running in an axial direction spirally wound between a plurality of wire guides, a machining fluid supply mechanism for supplying a machining fluid to a contact portion between the workpiece and the wire, and the workpiece A workpiece feeding means for pressing the workpiece against the wire row by pressing the workpiece while holding the wire is a resin-coated wire in which a surface of a base wire is coated with a resin, and the machining fluid supply mechanism A wire saw that cuts the workpiece into a wafer shape by pressing the workpiece held by the workpiece feeding means against the wire row while supplying the machining fluid to a contact portion between the workpiece and the wire ,
An eddy current displacement sensor that periodically detects a voltage value using the wire after contact with the workpiece as a measurement object, and a determination unit that determines whether the resin layer is worn or peeled from the voltage value; And the eddy current displacement sensor is disposed so as to be close to the wire row, and the determination means calculates a percentage difference by the following equation (1) using the voltage value and a moving average value of the voltage value. When the calculated percentage difference falls outside the predetermined threshold range from the standard deviation of the percentage difference when there is no wear of the resin layer determined in advance, wear or delamination of the resin layer occurs. A wire saw characterized in that it is determined that

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