JP2014083671A - Manufacturing method of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a wafer capable of securing a sufficient processing distance even when a cutting process is advanced, concerning a method for cutting a workpiece to obtain a wafer by bringing the workpiece into pressure contact with a traveling wire.SOLUTION: In a manufacturing method for cutting a workpiece to obtain a wafer by bringing a workpiece into pressure contact with a traveling wire, the workpiece is subjected to oscillatory movement by an oscillation mechanism having the center of oscillation on the opposite side to the arrangement side of the workpiece with respect to a traveling wire.

Description

  The present invention relates to a method for manufacturing a wafer. Specifically, the present invention relates to a wafer manufacturing method for slicing a crystal lump while securing a sufficient processing distance even during or at the end of cutting.

Conventionally, a method of cutting a crystal lump such as a semiconductor crystal into a certain thickness using a wire saw is known. This cutting method using a wire saw is a method in which a wire and a workpiece are brought into contact and sliced using abrasive grains fixed to the wire, free abrasive grains contained in a dispersion, or the like.
Since a wire saw can use a wire having a small diameter, the workpiece can be sliced with high accuracy, and generation of cutting waste (cutting loss) of the workpiece can be minimized. It has been. Further, since a plurality of flat plate substrates can be sliced simultaneously from the workpiece, there is an advantage that the production efficiency can be greatly increased.

  In the case of slicing a workpiece with a wire saw, a method of slicing while swaying the wire or workpiece is known in order to smoothly advance the cutting process. For example, Patent Documents 1 and 2 disclose a wire saw that advances a cutting process while swinging a workpiece. By swinging the workpiece, the workpiece and the wire come into contact with each other in a circular arc, so that it becomes easy to supply the dispersion liquid or coolant containing abrasive grains to the inside, and the cutting speed can be increased.

JP-A-10-202499 JP-A-8-85053

  However, in the wire saw disclosed in Patent Document 1, since the center of the workpiece and the oscillation center coincide with each other, there is a case where the machining point to be sliced coincides with the oscillation center in the progress of the cutting process. The cutting process proceeds in the same state as when there is no oscillation. That is, in a part of the cutting process, there is a problem that a processing distance cannot be sufficiently secured and the effect of swinging cannot be obtained. If a sufficient swinging effect is not obtained in the cutting process, the wafer cutting accuracy may be inferior or the speed of the cutting process may be reduced.

  Further, in the wire saw disclosed in Patent Document 2, the center of the workpiece and the swing center are arranged at different positions, but since the center of the workpiece and the swing center are close as the cutting process proceeds, There has been a problem that the machining distance becomes shorter as the cutting process proceeds. In particular, when the workpiece has a large diameter, if a sufficient processing distance cannot be secured at the final stage of the cutting process, a long time is required for the cutting process, which is a problem. On the other hand, when trying to slice a large-diameter workpiece using the wire saw disclosed in Patent Document 2, there arises a problem that the apparatus itself becomes large.

  Accordingly, the inventors of the present application provide a cutting method and a wire saw capable of ensuring a sufficient processing distance without reducing the processing distance in the middle or at the end of the cutting process in order to solve the problems of the conventional technology. The study was advanced as a purpose.

As a result of intensive studies to solve the above problems, the inventors of the present application have provided a swing center at a position where the distance between the machining point and the swing center increases as the cutting process proceeds. The present inventors have found that an excellent rocking effect can be obtained without reducing the processing distance during or at the end of cutting.
Specifically, the present invention has the following configuration.

[1] In a manufacturing method of cutting a workpiece by pressing the workpiece against a traveling wire to obtain a wafer, the workpiece is arranged with respect to the traveling wire. A method for manufacturing a wafer, characterized by performing a swing motion by a swing mechanism having a swing center on the opposite side to the side.
[2] The wafer manufacturing method according to [1], wherein the workpiece is cut by moving the swing center away from the traveling wire.
[3] The wafer manufacturing method according to [1] or [2], wherein a swing angle of the swing motion is ± 2 to ± 30 ° with respect to a swing center axis.
[4] The wafer manufacturing method according to any one of [1] to [3], wherein the workpiece is attached to a swinging frame, and the swinging frame swings and moves up and down.
[5] The wafer manufacturing method according to any one of [1] to [4], wherein the traveling wire forms a wire row in which a plurality of traveling wires are arranged substantially parallel to each other.
[6] The wafer manufacturing method according to any one of [1] to [5], wherein the workpiece is a periodic table group 13 nitride crystal.
[7] A swing frame that attaches a wire and a workpiece is provided, and the swing frame is provided with a swing center on the opposite side of the wire from the side on which the workpiece is disposed. A wire saw having a swing mechanism.

  According to the present invention, since the cutting process proceeds by moving the swing center away from the traveling wire, a sufficient working distance can be ensured in the cutting process. For this reason, the cutting resistance does not increase in the middle of the cutting process or in the final stage, and there is no cutting unevenness on the surface of the wafer, so that a wafer having a uniform film thickness can be obtained. Furthermore, since it is possible to suppress warping of the wafer, a high-quality wafer can be obtained.

  Further, according to the present invention, even when the cutting process proceeds, a sufficient processing distance can be ensured, so that the cutting speed does not decrease. Therefore, the workpiece can be cut efficiently. For this reason, the manufacturing method of this invention can be used suitably also for a large diameter workpiece.

FIG. 1 is a front view showing a wire saw according to the present invention. FIG. 2 is a front view showing the swing unit of the wire saw. FIG. 3 is a cross-sectional view taken along the line A-A ′ in FIG. 2. FIG. 3A is a schematic diagram illustrating how the workpiece swings, and FIG. 3B is a schematic diagram illustrating the positional relationship between the machining point and the swing center. FIG. 4 is an image diagram showing a state of cutting the workpiece.

  Hereinafter, modes for carrying out the present invention will be described. The present invention is not limited to the embodiments described below, and includes those appropriately modified by those skilled in the art from the following embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  The present invention relates to a manufacturing method in which a workpiece is cut (sliced) into a certain thickness by pressing the workpiece against a running wire to obtain a wafer. The wire is wound around a plurality of guide rollers so as to have a constant tension, and the guide roller moves at a high speed, whereby the wire travels in a certain direction. In the specification of the present application, the traveling wire refers to a wire traveling in a certain direction as the guide roller rotates, and in particular, a wire in a straight portion between the guide rollers that can be pressed against the workpiece. Point to.

(Basic configuration of wire saw)
Hereinafter, a wire saw which is an apparatus used for carrying out the manufacturing method of the present invention will be described with reference to the drawings. The drawings described below are examples of a wire saw used in the present invention, and a wire saw of another aspect appropriately modified may be used in the present invention.

  FIG. 1 illustrates a front view of a wire saw 100 used in the manufacturing method of the present invention. As shown in FIG. 1, the wire saw 100 includes a swing unit 10 and a lifting unit 40. The swing unit 10 includes a swing frame 20, a support frame 21, a rotating shaft 22, and a swing drive motor 23. The workpiece 1 is attached to the swing frame 20 of the swing unit 10. The lift unit 40 includes a work feed table 41 and a lift drive motor 42 that drives the work feed table 41. Since the wire saw 100 includes the lifting unit 40, the entire swing unit 10 can be moved up and down.

  The wire saw 100 further includes a traveling wire 2 and a guide roller 4 for winding the wire. The guide roller 4 can run the wire by rotating at high speed. For example, the guide roller 4 rotates at high speed by obtaining a driving force from the rotation driving motor 5.

  The swing frame 20 to which the workpiece 1 is attached swings and moves up and down in FIG. In the case of proceeding with the cutting process, a downward movement is performed out of the vertical movement. As a result, the workpiece 1 descends to the position of the traveling wire 2 and is pressed against the traveling wire 2 to start cutting.

As a crystal cutting method using a running wire for crystal cutting, for example, a kind of polishing cutting is performed by supplying a dispersion liquid in which water, oil, or the like and abrasive grains are mixed to a contact portion between the running wire 2 and a workpiece. A method for cutting (free abrasive grain method) or a method for cutting a crystal by using a wire for crystal cutting with abrasive grains made of diamond or the like fixed on the surface as the traveling wire 2 (fixed abrasive). Any of which can be used.
In the case of the free abrasive grain method, when the workpiece 1 and the traveling wire 2 are pressed against each other, a dispersion liquid containing abrasive grains is continuously supplied to the contact portion. The dispersion containing abrasive grains not only promotes cutting of the workpiece 1 but also functions to prevent excessive heating due to friction of the contact portion. On the other hand, in the case of the fixed abrasive method, it is preferable that the coolant is continuously supplied to the contact portion between the workpiece 1 and the traveling wire 2. The coolant can cool the heat generated in the cutting process or promote lubrication of the contact portion to reduce friction and facilitate cutting.

(Oscillating unit)
FIG. 2 is an enlarged view of the swing unit 10 in FIG. Due to the swing mechanism of the swing unit 10, the swing frame 20 swings so as to swing repeatedly in the front and back directions of FIG. 2. Thereby, the to-be-processed object 1 can also perform the same rocking | fluctuation motion.

  A support frame 21 is provided outside the swing frame 20. The support frame 21 is fixed to the main body of the wire saw 100. For this reason, the support frame 21 can maintain a stationary state without swinging even when the swing frame 20 is swinging.

  As shown in FIG. 2, the swing frame 20 and the support frame 21 are preferably composed of an upper wall and a pair of side walls connected to both ends of the upper wall. In this case, the upper wall and the pair of side walls need not be configured to be clearly distinguished, and each frame may be formed so as to draw a circular arc in a series.

  The wall surface of the swing frame 20 and the wall surface of the support frame 21 do not contact each other. Thereby, the swing frame 20 can smoothly swing inside the fixed support frame 21. As shown in FIG. 3, the upper surface of the upper wall of the swing frame 20 is preferably formed with a convex arc surface, and the lower surface of the upper wall of the support frame 21 is preferably formed with a concave arc surface. Thereby, even if it is a case where the rocking | fluctuation frame 20 and the support frame 21 are arrange | positioned adjacently, it can prevent that wall surfaces contact.

  The end region of the side wall of the swing frame 20 and the end region of the side wall of the support frame 21 have a connecting portion that connects the rotating shaft 22. That is, the swing frame 20 and the support frame 21 are connected by the rotation shaft 22. The rotating shaft 22 is a cylindrical shaft that is horizontal with respect to the mounting surface of the wire saw 100, and the rotating shaft 22 is supported via a bearing. Thereby, the swing frame 20 is rotatably supported and can swing on the inner side with respect to the support frame 21.

The rotating shaft 22 serves as a rocking center O when the rocking frame 20 performs a rocking motion. The rotating shaft 22 exists on the opposite side of the traveling wire 2 from the side on which the workpiece 1 is disposed. The rotation shaft 22 needs to be connected to the swing frame 20 and the support frame 21 at appropriate positions so that the rotation shaft 22 is disposed at such a position. That is, the rotating shaft 22 is provided below the traveling wire 2.
Further, the lengths of the side walls of the swing frame 20 and the support frame 21 can be adjusted so that the rotation shaft 22 is disposed at the position as described above. For example, it is preferable that the side walls of the swing frame 20 and the support frame 21 have such a length as to extend below the traveling wire 2.

  A rotating shaft 22 that connects the swing frame 20 and the support frame 21 is provided with a swing drive motor 23. The swing drive motor 23 can swing and move by applying a reciprocating rotational force to the swing frame 20 inside the fixed support frame 21. The swing distance and swing angle of the swing frame 20 can be adjusted as appropriate by adjusting the output of the swing drive motor 23.

The swing unit 10 according to the present invention has a swing center O on the opposite side of the traveling wire 2 from the side on which the workpiece 1 is disposed. Here, the oscillation center O refers to the center point of the cross section of the rotary shaft 22 described above.
3 shows a cross-sectional view taken along the line AA ′ in FIG. 2. As shown in FIG. 3, the swing center O is the side on which the workpiece 1 is disposed with respect to the traveling wire 2. It is located on the opposite side. As shown in FIG. 3 (a), when the distance between the horizontal line including the swing center O and the horizontal line including the center of the workpiece 1 is R, before the cutting of the workpiece 1 is started. R is
It is preferable that it is 30-300 mm, and it is more preferable that it is 50-150 mm. Further, R is preferably 30 to 300 mm, more preferably 50 to 150 mm, from the start to the end of cutting of the workpiece 1.
By setting R within the above range, it is not necessary to increase the size of the apparatus, and an appropriate swinging motion can be performed.

As shown in FIG. 3A, the swing angle can be represented by θ. The swing angle is an angle formed between a line connecting the center of the workpiece 1 and the swing center O and the swing center line P when swinging to the maximum amplitude. Here, the rocking center line P is a line that passes through the rocking center O and is perpendicular to a horizontal line including a processing point existing on the wire.
θ is preferably ± 2 ± 30 °, more preferably ± 3 ± 15 °. Here, the + value representing the angle θ represents the swing angle when swinging in the right direction from the line connecting the center of the workpiece 1 and the swing center O in FIG. 3A. It is assumed that the value of-representing the angle of θ represents the swing angle when swinging in the left direction.
By setting θ within the above range, the workpiece 1 can perform an appropriate swinging motion. Further, when θ is equal to or greater than the above upper limit value, it is necessary to widen the interval between the guide rollers 4 holding the wire. If this interval is too wide, it is not preferable because sufficient tension cannot be applied to the wire.

  In FIG. 3A, the distance that the workpiece 1 moves by the swing motion is defined as a swing distance and is represented by S. The swing distance S indicates the distance drawn by the locus moved by the swing motion at the point closest to the swing center O. S is preferably 2 to 315 mm, more preferably 5 to 79 mm. By setting S within the above range, the workpiece 1 can perform an appropriate swinging motion, and the cutting efficiency can be increased.

In the present specification, the processing distance refers to a distance between two processing points formed on the wire when the swing swing is maximum.
When the traveling wire 2 is viewed from the direction of FIG. 3A, the processing points present on the traveling wire 2 are present at the left and right ends of the traveling wire 2 when the swinging swing width is maximized. Will do. In the specification of the present application, the machining point when the swing amplitude is maximized is the left end machining point and the right end machining point, and the distance between the left end machining point and the right end machining point is the machining distance.

In the present invention, the workpiece is cut by moving the swing center away from the traveling wire 2.
FIG. 3B illustrates the positional relationship between the machining point and the oscillation center in the cutting process of the workpiece 1. Here, the processing point at the start cutting of the workpiece 1 and G _1, the working point in the middle of cutting is set to G _2. Further, the swing center at the start of cutting is O _1, and the swing center in the middle of cutting is O ₂ . In the present invention, when the horizontal line containing the G _1, the distance between the horizontal line containing O ₁ and K _1, and the horizontal line containing G _2, the distance between the horizontal line containing O ₁ and K _2, K ₂ > K ₁ Thereby, in this invention, the distance between the left end processing point and the right end processing point, that is, the processing distance can be increased as the cutting of the workpiece 1 proceeds. Thereby, cutting | disconnection can be advanced efficiently.

In the prior art, since the swing center is provided on the workpiece 1 side, the distance between the horizontal line including the machining point and the horizontal line including the swing center is reduced as the cutting process proceeds. . For this reason, as the cutting process proceeds, the processing distance becomes insufficient, and problems such as a reduction in cutting speed and warping of the wafer have occurred. In particular, when a large-diameter wafer is obtained, a reduction in processing distance has been a serious problem.
However, in the present invention, the workpiece 1 swings about a point provided below the traveling wire 2 as a swing center. That is, in the present invention, the swing center O is provided on the opposite side of the traveling wire 2 from the side on which the workpiece 1 is disposed. The distance between the horizontal line including the machining point and the horizontal line including the center of oscillation does not decrease. Thereby, even if the cutting process proceeds, a sufficient processing distance can be ensured, and it is possible to suppress a decrease in cutting speed and the occurrence of warping of the wafer. As a result, a high-quality wafer can be produced efficiently.

(Elevating unit)
The oscillating frame 20 constituting the oscillating unit 10 performs an oscillating motion and also an elevating motion. That is, members such as the swing frame 20, the support frame 21, the rotating shaft 22, and the swing drive motor 23 to which the workpiece 1 is attached integrally move up and down. Thereby, the workpiece 1 is pressed against the traveling wire 2 while performing a swinging motion, and the cutting process can be advanced.

  The members constituting the lifting unit 40 are not particularly limited as long as the members can move up and down the above-described members. As a member constituting the lifting mechanism, for example, a work feed table 41 and a lift drive motor 42 that moves the work feed table 41 up and down can be cited. As shown in FIGS. 1 and 2, the work feed table 41 is provided on the upper surface of the upper wall of the support frame 21, and can move up and down by driving a lift drive motor 42. The driving force of the lifting drive motor 42 is preferably adjusted as appropriate depending on the material and hardness of the workpiece 1. Also, the driving force may be adjusted so as to adjust the lifting speed even during the cutting process of the workpiece 1. For example, when the workpiece 1 and the traveling wire 2 come into contact with each other, the driving force can be adjusted so as to reduce the speed of the downward movement and increase the speed of the downward movement as the cutting progresses.

  4A and 4B show a cross section of the workpiece 1 being cut by a wire. In FIG. 4A, G indicates a machining point, and the shaded portion indicates a portion where cutting has been performed. FIG. 4B schematically shows a locus drawn by the processing point G in FIG. As can be seen from FIGS. 4A and 4B, in the present invention, the workpiece 1 is cut by combining the swinging motion and the lifting motion, so the locus of the machining point on the cut surface is the wire. Draw a convex arc with respect to.

(Wire)
The wire is held by a plurality of guide rollers 4 capable of rotating, and a certain tension is applied to the wire. The wire is preferably held by at least two guide rollers 4. As the plurality of guide rollers 4 rotate at a high speed, the wire travels, and the traveling wire 2 and the workpiece 1 are brought into contact with each other to cut. In this case, the plurality of guide rollers 4 are preferably adjusted so as to rotate at the same speed.
The guide roller 4 is preferably provided with a groove parallel to the tension direction. The wire is stably arranged using this groove as a guide. Thereby, even if it is a case where it drive | works at high speed, a wire does not shift | deviate to an unpreferable direction or wires do not overlap.

  The guide roller 4 is preferably provided with a plurality of grooves substantially in parallel. The wires are preferably arranged by the plurality of grooves to form the wire row 3. The number of wires constituting the wire row 3 can be 2 to 30, for example. As a result, a plurality of wafers can be cut at the same time, and the wafer production efficiency can be greatly increased.

The diameter of the wire is preferably 70 to 200 μm, and more preferably 80 to 180 μm. It is preferable that the wire is as thin as possible because cutting loss can be reduced. However, if the wire cannot withstand the tension, the wire is damaged. For this reason, it is preferable to consider the material of the workpiece 1 and the like, calculate the tension necessary for cutting, and change the diameter of the wire as appropriate. A well-known thing can be utilized for a wire and there is no restriction | limiting in particular in the material.
In the present invention, a method such as a loose abrasive method or a fixed abrasive method can be used, but a fixed abrasive-type crystal cutting wire is used in that the cutting speed is high and the time and effort of cleaning are not required. preferable.
The fixed abrasive grains can be fixed to the surface of the wire for crystal cutting by, for example, electrodeposition. It is preferable to use an abnormally protruded abrasive grain or a sharp-angled part of the abrasive grain that has been reshaped by grinding after the electrodepositing and fixing of the abrasive grains, because cracks due to cutting are less likely to enter the workpiece. Examples of the abrasive grains of the grindstone include alundum (A), white alundum (WA), pink alundum (PA), dismantled alumina (HA), artificial emery (AE), alumina zirconia (AZ), and carborundum ( C), green carborundum (GC), cubic boron nitride (CBN), diamond and the like.

  A dispersion liquid in which abrasive grains are dispersed is continuously supplied to a contact portion where the traveling wire 2 comes into contact with the workpiece 1. The dispersion liquid may be supplied so as to ooze out from the groove of the guide roller 4 or may be supplied so as to be applied from above the guide roller 4.

(Workpiece)
The workpiece 1 is attached to the swing frame 20. A swing drive motor 23 is attached to the swing frame 20, and the workpiece 1 swings when the swing frame 20 swings by the swing drive motor 23.

  Examples of the workpiece 1 include semiconductor crystals, quartz, and oxide single crystals. The production method of the present invention is preferable because the effect of the present invention becomes remarkable when used for cutting periodic table group 13 nitride crystals which are hard and difficult to cut, among semiconductor crystals. More preferred are nitrides containing Ga, such as GaN, AlGaN, InGaN, and even more preferred is GaN. By using the manufacturing method of the present invention, a periodic table group 13 nitride wafer having a certain thickness can be obtained efficiently.

  The shape of the workpiece 1 is not particularly limited, but preferably has a size and a shape that can be attached to the work holding unit 30 described later. The cross section of the workpiece 1 can be a circle, an ellipse, a quadrangle, a hexagon, a triangle, or a trapezoid, and among them, a circle with good cutting efficiency is preferable.

  The workpiece 1 may be attached to the swing frame 20 by a fixing member such as a work holding unit 30. The workpiece holding unit 30 can hold and fix both end portions of the workpiece 1. Since the workpiece 1 is pressed against the traveling wire 2 that travels at a high speed, the workpiece 1 is preferably held firmly by the workpiece holding unit 30.

(Wafer)
The wafer obtained by the manufacturing method according to the present invention is preferably a periodic table group 13 nitride wafer, and the thickness of the wafer is preferably 200 to 1000 μm. According to the manufacturing method of the present invention, it is possible to obtain a high-quality wafer having a uniform film thickness and suppressing warpage, and thus is preferably used for a semiconductor device or the like. Moreover, in the manufacturing method of this invention, since the manufacturing efficiency of a wafer can be improved, manufacturing cost can be held down.

  According to the present invention, it is possible to obtain a high quality wafer free from uneven cutting and warping. Moreover, according to this invention, since cutting speed can be raised, manufacturing efficiency can be raised. The present invention can be suitably used for manufacturing a semiconductor wafer, and has high industrial applicability.

DESCRIPTION OF SYMBOLS 1 Workpiece 2 Traveling wire 3 Wire row 4 Guide roller 5 Rotation drive motor 10 Oscillation unit 20 Oscillation frame 21 Support frame 22 Rotating shaft 23 Oscillation drive motor 30 Work holding unit 40 Elevation unit 41 Work feed table 42 Elevation drive Motor 100 Wire saw O Oscillation center P Oscillation center line G Machining point

Claims (7)

In a manufacturing method of cutting a workpiece and obtaining a wafer by pressing the workpiece against a traveling wire,
The method of manufacturing a wafer, wherein the workpiece is oscillated by an oscillating mechanism having an oscillating center on a side opposite to the side where the workpiece is disposed with respect to the traveling wire.   The wafer manufacturing method according to claim 1, wherein the workpiece is cut by moving the swing center away from the traveling wire.   3. The wafer manufacturing method according to claim 1, wherein a swing angle of the swing motion is ± 2 ± 30 ° with respect to a swing center axis. The workpiece is attached to a swing frame,
The method of manufacturing a wafer according to claim 1, wherein the swing frame performs a swing motion and a lift motion.   5. The wafer manufacturing method according to claim 1, wherein the travel wires form a wire row in which a plurality of travel wires are arranged substantially parallel to each other.   6. The wafer manufacturing method according to claim 1, wherein the workpiece is a periodic table group 13 nitride crystal. It has a swing frame that attaches the wire and the workpiece,
The rocking frame is a wire saw having a rocking mechanism in which a rocking center is provided on a side opposite to a side on which the workpiece is disposed with respect to the wire.

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