JPH10272621A - Wire saw and method for cutting ingot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire saw by which irregularities in the inner face thickness of a cut wafer can be reduced and a method for cutting an ingot for the wafer. SOLUTION: An ingot 29 is cut by moving back and forth and also fluctuating a wire line 11 with the help of a shuttle motion means 13 and a fluctuating means 14, while supplying a whetting liquid (a) to an area near the cut part of an ingot 29 by a whetting liquid supply means 12. At the time of cutting, the fluctuation angle (α) of the wire line 11 proportional to the contact length between the wire line 11 and the ingot 29 is controlled by the fluctuation angle control means 15a of a control part 15. Therefore, it is possible to stably cut even the cut starting part or the cut ending part of the ingot 29. Consequently, irregularities in the inner face thickness of a wafer can be reduced and the high-quality wafer can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire saw and an ingot cutting method, and more particularly, to a wire saw capable of reducing in-plane thickness unevenness of a cut wafer and an ingot cutting method using the wire saw.

[0002]

2. Description of the Related Art In a wire saw, a slurry-like abrasive liquid in which free abrasive grains are mixed in lapping oil is supplied to a traveling wire row, and the traveling wire row is supplied to an ingot such as a single crystal silicon rod as a work. This is an apparatus for relatively pressing and cutting an ingot by the grinding action of the abrasive grains. When cutting an ingot using a conventional wire saw, the wire row is reciprocated and the wire row is largely swung at a set swing angle from a standby time before the start of cutting the ingot. This swing is performed with the center of the cut surface of the ingot as a fulcrum, and a large amount of slurry is supplied to the center portion of the ingot. Thereafter, the ingot is brought close to the wire row, and the ingot is cut. At this time, the swing angle of the wire row is constant over the entire cutting length of the ingot cutting (for example, see line c in FIG. 3).

[0003]

However, the following problems have been caused by the above-mentioned conventional cutting method using a wire saw. That is, the swing angle of the wire row is constant over the entire period from the start of the ingot cutting to the end of the cutting. For this reason, for example, even when cutting the cutting start portion or the cutting end portion where the contact length between the wire row and the ingot is short, the wire row is the same as when cutting the central portion of the ingot where the contact length is long. Swings at a large swing angle. As a result, the supply of the slurry is excessive at the cutting start portion and the cutting end portion, and the cutting is performed excessively. In other words, there is a tendency that the width of the cut groove of the ingot becomes large, and both end portions in the cutting direction of the obtained wafer are thinner than the central portion. That is, the in-plane thickness unevenness of the cut wafer was increased.

Accordingly, the present inventors have conducted intensive studies and found that the reason why the wafer becomes thinner at the cutting start portion and the cutting end portion of the ingot is caused by excessive supply of slurry due to rocking. The present invention has been completed.

[0005]

That is, an object of the present invention is to provide a wire saw and an ingot cutting method capable of reducing the in-plane thickness unevenness of a cut wafer.

[0006]

According to the present invention, there is provided a wire saw for cutting a cylindrical ingot substantially perpendicularly to its axis by reciprocating a wire row while supplying an abrasive liquid. Swinging means for swinging the ingot and the wire row relatively, with a substantially central portion of the ingot as a fulcrum within a cut surface of the ingot,
A wire saw having swing angle control means for controlling a swing angle between the ingot and the wire row according to a contact length between the wire row and the ingot.

There is no limitation on the type of wire saw to which the present invention is applied. For example, a wire saw may be of a type in which an ingot is pressed against an ingot and cut, or a type in which an ingot is pressed against an ingot and cut. Further, the ingot may be pressed against the upper part of the wire row or may be pressed against the lower part of the wire row. However, the latter type, which is in contact with the lower part of the wire row, allows the abrasive liquid to be put on the upper surface of the wire row and can be brought into the cut groove of the wafer satisfactorily. Here, controlling the swing angle of the wire array in accordance with the contact length between the wire array and the ingot means, for example, that when the contact length between the wire array and the ingot increases, the swing angle of the wire array increases. Conversely, it refers to control for reducing the swing angle of the wire row as the contact length decreases. The supply portion of the abrasive liquid may be on the wire row near the ingot as described above, or may be directly supplied to the ingot.

[0008] The supply of the polishing liquid may be either automatic adjustment of the supply rate of the polishing liquid or manual adjustment of the supply rate of the polishing liquid according to the cutting progress. The swing angle of the wire row by the swing means is 1 ° to 4 °, particularly 1.0 ° to 1.
5 ° is preferred. If the angle is less than 1 °, the cutting speed does not increase so much because the abrasive grains are insufficiently penetrated into the center of the ingot. If it exceeds 4 °, the thickness of the central portion of the cut wafer becomes thin and its flatness deteriorates. Note that the rocking here means rocking about a point on a line that is in a plane perpendicular to the axis of the ingot and that passes through the center of the ingot.

According to a second aspect of the present invention, there is provided a wire saw for cutting a cylindrical ingot substantially perpendicularly to its axis by reciprocating a wire row while supplying an abrasive liquid. A swinging means for relatively swinging the ingot and the wire row around a substantially central portion of the ingot, and a swing stopping means for stopping the swinging when the cutting start portion of the ingot is cut. It has a wire saw. The swing stop means may stop the swing of the wire array not only at the cutting start portion of the ingot but also at both the cutting start portion and the cutting end portion. The cutting start portion and the cutting end portion refer to portions extending from the outer surface to, for example, about １ ／ of the diameter of the ingot.

According to a third aspect of the present invention, a wire row is reciprocated in a cutting plane substantially perpendicular to the axis of the ingot while the abrasive liquid is supplied to the vicinity of the cutting section of the ingot. An ingot cutting method for cutting the ingot into a number of wafers by relatively swinging the wire row and the ingot with the substantially central portion as a fulcrum, wherein a contact length between the wire row and the ingot is reduced. An ingot cutting method for controlling the swing angle of the wire row accordingly. Specifically, for example, when the contact length between the wire row and the ingot increases, the swing angle of the wire row increases, and when the contact length decreases, the swing angle of the wire row decreases.

According to a fourth aspect of the present invention, a wire array is reciprocated in a cutting plane substantially perpendicular to the axis of the ingot while supplying the abrasive fluid to the vicinity of the cutting part of the ingot. An ingot cutting method for cutting the ingot into a number of wafers by swinging the wire row and the ingot relatively with the substantially central portion as a fulcrum, from the start of cutting the ingot to a predetermined cutting range, This is an ingot cutting method for stopping the swing.

[0012]

In the wire saw and the ingot cutting method according to the first to fourth aspects, the wire row is reciprocated while the abrasive liquid is supplied to the vicinity of the cut portion of the ingot, and the wire is swung at a predetermined swing angle. By doing so, the ingot is cut. However, for example, when cutting the cutting start portion or the cutting end portion where the contact length between the wire row and the ingot is short, according to the contact length between the wire row and the ingot,
Either control the swing angle of the wire array to be small or completely stop swinging the wire array. Thereby, usually, since the abrasive liquid easily enters the cutting groove, even in the cutting start portion or the cutting end portion of the ingot where the groove width of the cutting groove of the ingot tends to be large, relatively does not laterally swing. The wire row can be cut stably. Thereby, in-plane thickness unevenness of the cut wafer can be reduced. If the swing at the end of cutting is reduced or stopped, the cut amount of the carbon bed supporting the wafer is reduced accordingly. This allows the use of relatively thin carbon beds.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First, a wire saw according to a first embodiment of the present invention and a method for cutting an ingot thereof will be described. FIG. 1 is a schematic view showing a wire saw according to a first embodiment of the present invention. FIG. 2A is an enlarged sectional view of a main part showing a cutting state of a cutting start portion of the ingot. FIG.
(B) is a principal part expanded sectional view which shows the cutting state of the cutting center part of an ingot. FIG. 2C is an enlarged sectional view of a main part showing a cut state of a cut end portion of the ingot. FIG.
Is a graph showing a relationship between a cutting position of an ingot and a swing angle of a wire row.

In FIG. 1, reference numeral 10 denotes a wire saw,
The wire saw 10 includes an abrasive liquid supply unit 12 that supplies the abrasive liquid a to a wire array 11 composed of many wires, a reciprocating unit 13 that reciprocates the wire array 11,
And a control unit 15 for controlling these operations and the like. Abrasive liquid supply means 12
Is the abrasive fluid a pumped by the built-in slurry pump
Is discharged onto the wire array 11 through a pair of abrasive fluid nozzles 16 and is put on the wire array 11. The reciprocating means 13 mainly includes a wire supply / recovery motor 17 serving as a driving unit, a first wire reel 18, and a second wire reel 19. Two groove rollers 2
0 and large and small weights 21 and 22.

First and second wire reels 18, 19 and 2
As shown in FIG. 1, the groove rollers 20 are connected by a long wire row 11 via a number of guide rollers. A drive reel 23 is fixed to an output shaft of the wire supply / recovery motor 17. When the drive reel 23 is rotated right or left by the wire supply / recovery motor 17, the first and second
When the wire reels 18 and 19 rotate, the wire array 11 is drawn out or wound up.

The oscillating means 14 has an oscillating disk 25 in which the ends of a pair of groove rollers 20 are pivotally mounted and a pulley is formed on the outer periphery, and an oscillating motor 26 as a driving unit. doing. When the drive motor 27 rotates the drive pulley 27 fixed to its output shaft, the rotational force is transmitted to the swing disk 25 via the timing belt 28, whereby the swing disk 25 is moved to the right or left. Swing to the left by a predetermined angle. The oscillating disk 25 oscillates in a plane including the disk surface in a predetermined angle range clockwise or counterclockwise in FIG. The swing angle at this time is
It is controlled by the swing angle adjustment of the control unit 15.

The control unit 15 mainly comprises: a supply amount of the abrasive liquid supply means 12 to the wire array 11; a reciprocating speed of the wire array 11 by the reciprocating means 13;
1 is controlled. Moreover, the control unit 15 includes
Swing angle control means 15a for controlling the swing angle α of the wire array 11 in accordance with the contact length between the wire array 11 and the ingot 29
have. Here, as ingot 29, CZ
A block of single-crystal silicon having a diameter of 200 mm pulled up by a method is used.

The control of the swing angle α by the swing angle control means 15a specifically means that the swing angle is gradually increased as the contact length between the wire row and the ingot becomes longer, and conversely, This is to gradually reduce the swing angle as the contact length becomes shorter (see FIGS. 2A to 2C and line a in FIG. 3). In the case of the ingot 29 having a circular cross section, the contact length with the linear wire row 11 is reduced at the cutting start portion and the cutting end portion of the ingot 29. 1 and 2, reference numeral 30 denotes a carbon bed for fixing the ingot 29.

Next, an ingot cutting method using the wire saw 10 according to the first embodiment of the present invention will be described. As shown in FIG. 1, the first and second wire reels 18 and 19 are rotated by a wire supply / recovery motor 17.
The wire row 11 is led out from both reels 18 and 19,
It is wound up. Thereby, the wire row 11 becomes 1 /
Run to the right or left at a speed of 300 to 1000 m / min every 30 minutes.

At the time of reciprocation of the wire row 11, 1/1
A swing direction switching command is issued from the control unit 15 every five minutes, and the swing direction of the wire array 11 is switched by the swing means 14. That is, the oscillating disk 25 is driven by the oscillating motor 26.
In the opposite direction to the predetermined swing angle α (FIG. 2 (a)
To (c) swing angles α1 to α3), and the pair of groove rollers 20 disposed opposite to each other is rotated in the opposite direction by the same angle. The ingot 29 abuts on the running wire array 11 in a state where the abrasive fluid a is supplied onto the wire array 11 from the abrasive fluid supply means 12 and is gradually cut. Hereinafter, the cutting state of the ingot 29 will be described in more detail with reference to FIGS.

At the time of cutting the ingot 29, as described above, the swing angle control means 15a of the control unit 15
The swing angle α of the wire array 11 is controlled according to the contact length between the wire array 11 and the ingot 29. Specifically, FIG.
As shown in the semi-elliptical line a, the wire row 11 is in contact with the ingot 29, and the wire row 1 extends from the cutting start portion of the ingot 29 to the central portion of the ingot 29.
The swing angle is gradually increased as the contact length between 1 and ingot 29 becomes longer. On the contrary, ingot 2
As the contact length between the wire array 11 and the ingot 29 becomes shorter from the central portion of 9 to the cut end portion of the ingot 29, the swing angle is gradually reduced.

This situation is shown in FIGS. 2 (a) to 2 (c).
FIG. 2A shows a cutting operation state of a cutting start portion of the ingot 29 where the swing angle of the wire row 11 is as small as α1.
FIG. 2B shows a cutting operation at the same central portion where the swing angle of the wire array 11 is as large as α2, and FIG. 2C shows a cutting operation at a cutting end portion of the ingot 29 where the swing angle of the wire array 11 is as small as α3. The work situation. Accordingly, the abrasive liquid is usually easy to enter, and even at the cutting start portion or the cutting end portion of the ingot 29 where the width of the cutting groove of the ingot 29 tends to be large, the lateral direction does not relatively swing and is stable. Wire row 1
Since 1 can be cut, the in-plane thickness unevenness of the cut wafer can be reduced, and a good quality wafer can be obtained.

Next, a wire saw and an ingot cutting method according to a second embodiment of the present invention will be described with reference to FIGS. 1, 3 and 4. FIG. 4A is an enlarged sectional view of a main part showing a cutting state of a cutting start portion of an ingot in a wire saw according to a second embodiment of the present invention, and FIG. 4B is a cutting state of a cutting central portion of the ingot. FIG. 4C is an enlarged sectional view of a main part showing a cut state of a cut end portion of the ingot. As shown in FIG.
Reference numeral 0 'denotes a wire saw according to the second embodiment. A wire saw 10' is provided in the control unit 15 for stopping the swing of the wire row 11 when the cutting start portion and the cutting end portion of the ingot 29 are cut. It has a stopping means 15b. Note that the swing angle control means 15a of the first embodiment is omitted.

In the use of the wire saw 10 ', when the cutting start portion of the ingot 29 is cut, as shown by the line b in FIG. The swing of the wire array 11 is stopped at a distance of 25 mm from the start end, and then the rocking means 14 is moved between 25 and 175 mm of the central portion of the cut until reaching the cut end portion (25 mm from the cut end end).
Swings the wire array 11 by an angle of 1 °, and then stops swinging the wire array 11 at the end of cutting. As described above, since the swing of the ingot 29 at the cutting start portion and the cutting end portion is stopped, similarly to the first embodiment, at the time of cutting the cutting start portion and the cutting end portion, it is relatively small. It is possible to stably cut the wire row 11 without lateral deflection, and thus it is possible to reduce in-plane thickness unevenness in the cut wafer.

[0025]

As described above, according to the wire saw and the ingot cutting method according to the present invention, when the contact length between the wire row and the ingot is short, for example, when the cutting start portion and the cutting end portion of the ingot are cut. According to the contact length between the wire row and the ingot, the swing angle of the wire row is controlled or the swing of the wire row is completely stopped. As a result, even in the cutting start portion or the cutting end portion where the groove width of the cutting groove is likely to be large, relatively no lateral deflection,
It is possible to stably cut the wire row and reduce in-plane thickness unevenness in the cut wafer.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a wire saw according to a first embodiment of the present invention.

FIG. 2A is an enlarged sectional view of a main part showing a cutting state of a cutting start portion of the ingot according to the first embodiment of the present invention. (B) is an enlarged sectional view of a main part showing a cut state of a cut central portion of the ingot according to the first embodiment of the present invention.
FIG. 3C is an enlarged sectional view of a main part showing a cut state of a cut end portion of the ingot according to the first embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a cutting position of an ingot and a swing angle of a wire row according to the first embodiment of the present invention.

FIG. 4A is an enlarged sectional view of a main part showing a cutting state of a cutting start portion of an ingot in a wire saw according to a second embodiment of the present invention. (B) is an enlarged sectional view of a main part showing a cut state of a cut center portion of the ingot.
(C) It is a principal part expanded sectional view which similarly shows the cutting | disconnection state of the cutting completion part of an ingot.

[Explanation of symbols]

 10, 10 'wire saw, 11 wire rows, 12 abrasive liquid supply means, 13 reciprocating means, 14 swing means, 15 control unit, 15a swing angle control means, 15b swing stop means, 29 ingot, a grinding fluid.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tatsuyoshi Kobayashi Inside Mitsubishi Materials Silicon Co., Ltd., 1-1-5 Otemachi, Chiyoda-ku, Tokyo

Claims (4)

[Claims] 1. A wire saw for cutting a columnar ingot substantially perpendicularly to an axis thereof by reciprocating a wire row while supplying an abrasive liquid, wherein the ingot is substantially cut within a cut surface of the ingot. Swinging means for relatively swinging the ingot and the wire row with the center as a fulcrum; and controlling a swing angle between the ingot and the wire row according to a contact length between the wire row and the ingot. A swing angle control means. 2. A wire saw for cutting a columnar ingot substantially perpendicularly to an axis thereof by reciprocating a wire row while supplying an abrasive liquid, wherein the ingot is substantially cut within a cut surface of the ingot. A wire saw comprising: a rocking means for relatively rocking the ingot and the wire row around a center portion; and a rocking stop means for stopping the rocking when cutting the ingot cutting start portion. 3. A wire array is reciprocated in a cutting plane substantially perpendicular to the axis of the ingot while supplying the abrasive fluid to the vicinity of the cutting part of the ingot, and a substantially central portion of the ingot is supported in the cutting plane. And an ingot cutting method of cutting the ingot into a number of wafers by relatively swinging the wire row and the ingot, wherein the wire is connected to the wire row and the ingot according to a contact length of the ingot. An ingot cutting method for controlling the row swing angle. 4. A wire train is reciprocated in a cutting plane substantially perpendicular to the axis of the ingot while supplying the abrasive fluid to the vicinity of the cutting part of the ingot, and a substantially central portion of the ingot is supported in the cutting plane. An ingot cutting method for cutting the ingot into a number of wafers by relatively swinging the wire row and the ingot, wherein the swing is stopped from a start of cutting the ingot to a predetermined cutting range. How to cut ingots.