JP3692703B2 - Wire saw and ingot cutting method - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
The wire saw supplies a slurry-like abrasive liquid, in which loose abrasive grains are mixed into wrapping oil, to the traveling wire array, while pressing the traveling wire array relatively against an ingot such as a single crystal silicon rod as a workpiece. A device for 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 from the standby state before the ingot is cut, and the wire row is swung at a set swing angle. This swing is performed using the center of the ingot cut surface as a fulcrum, and a large amount of slurry is supplied to the central 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 length of the ingot cutting length (see, for example, line c in FIG. 3).
[0003]
[Problems to be solved by the invention]
By the way, depending on the conventional cutting method using a wire saw, the following problems have occurred. In other words, the swing angle of the wire row is constant over the entire period from the start of cutting the ingot cutting to the end of cutting. For this reason, for example, even when cutting a cutting start portion and a 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 having a long contact length. Oscillate at a large oscillation angle.
As a result, the supply of slurry is excessive in the cutting start part and the cutting end part, and the cutting is excessive. That is, there is a tendency that the groove width of the cutting groove of the ingot is increased, and both end portions in the cutting direction of the obtained wafer are thinner than the center portion. That is, the in-plane thickness unevenness in the cut wafer increased.
[0004]
Therefore, as a result of extensive research, the present inventor has found that the thinning of the wafer at the cutting start portion and the cutting end portion of the ingot is caused by excessive supply of slurry due to rocking. Was completed.
[0005]
OBJECT OF THE INVENTION
That is, an object of the present invention is to provide a wire saw and an ingot cutting method that can reduce in-plane thickness unevenness of a cut wafer.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 is a wire saw that cuts a cylindrical ingot substantially perpendicularly to its axis by reciprocating a wire row while supplying an abrasive liquid, and within the cutting surface of the ingot, Based on a point on a straight line including the center of the ingot as a fulcrum, swing means for relatively swinging the ingot and the wire row, and the ingot and wire according to the contact length between the wire row and the ingot A wire saw having swing angle control means for controlling the swing angle between the rows so as to change along a semi-elliptical curve having the cut position as an elliptical long axis and the swing angle as an elliptical short axis. It is.
[0007]
The wire saw to which the present invention is applied is not limited in variety, and may be of a type that cuts by pressing the ingot against the wire row, or a type that cuts the wire row against the ingot on the contrary. Further, the ingot may be pressed against the upper part of the wire row or the lower part of the wire row. However, the latter type that presses against the lower part of the wire row can carry the abrasive liquid on the upper surface of the wire row and can bring it into the cutting groove of the wafer better.
The supply portion of the abrasive liquid may be on the wire row near the ingot as described above, or may be supplied directly to the ingot.
[0008]
In addition, the supply of the abrasive liquid may be either automatically adjusting the abrasive liquid supply amount in accordance with the cutting progress state or manually adjusting the abrasive liquid supply amount.
The rocking angle of the wire row by the rocking means is preferably 1 ° to 4 °, particularly 1.0 ° to 1.5 °. When the angle is less than 1 °, the abrasive grains are not sufficiently penetrated into the center of the ingot and the cutting speed is not improved so much. On the other hand, if the angle exceeds 4 °, the thickness of the center portion of the cut wafer becomes thin, and the flatness becomes worse. The swinging here means swinging around a point on a line passing through the center of the ingot in a plane perpendicular to the axis of the ingot.
[0009]
The invention according to claim 2, while supplying the polishing liquid in the vicinity of the cutting portion of the ingot, with reciprocating the wire row substantially in a vertical cutting plane to the axis of the ingot, in this cut surface, of the ingot An ingot cutting method for cutting the ingot into a plurality of wafers by relatively swinging the wire array and the ingot with a point on a straight line including the center as a fulcrum, wherein the wire array and the ingot Ingot cutting that controls the swing angle of the wire array according to the contact length so as to change along a semi-elliptical curve with the cutting position as the elliptical long axis and the swinging angle as the elliptical short axis. Is the method.
[0010]
[Action]
In the wire saw and the ingot cutting method according to claim 1 or 2, by supplying the abrasive liquid to the vicinity of the cutting portion of the ingot, the wire row is reciprocated and is swung at a predetermined swing angle. Go, cut the ingot.
As a result, since the abrasive liquid tends to easily enter the cutting groove, the ingot cutting groove tends to have a large groove width. , Can cut the wire row stably. Thereby, the in-plane thickness unevenness in the cut wafer can be reduced.
Note that if the oscillation of the cutting end portion is reduced or stopped, the cut amount of the carbon bed that supports the wafer is reduced accordingly. Thereby, a relatively thin carbon bed can be used.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. First, a wire saw and its ingot cutting method according to a first embodiment of the present invention will be described.
FIG. 1 is a schematic view showing a wire saw according to a first embodiment of the present invention. Fig.2 (a) is a principal part expanded sectional view which shows the cutting state of the cutting start part of an ingot. FIG. 2B is an enlarged cross-sectional view of a main part showing a cutting state of a cutting center portion of the ingot. FIG.2 (c) is a principal part expanded sectional view which shows the cutting state of the cutting | disconnection end part of an ingot. FIG. 3 is a graph showing the relationship between the cutting position of the ingot and the swing angle of the wire row.
[0014]
In FIG. 1, reference numeral 10 denotes a wire saw. The wire saw 10 includes a polishing liquid supply means 12 for supplying a polishing liquid a to a wire row 11 composed of a plurality of wires, and a reciprocating means 13 for reciprocating the wire row 11. A swinging means 14 for swinging the wire row 11 and a control unit 15 for controlling these operations and the like are provided.
The abrasive liquid supply means 12 discharges the abrasive liquid a pumped by a built-in slurry pump onto the wire row 11 via a pair of abrasive liquid nozzles 16 and puts it on this.
The reciprocating means 13 mainly includes a wire supply / recovery motor 17 serving as a drive unit, a first wire reel 18, a second wire reel 19, and a plurality of wire grooves formed on the outer peripheral surface thereof. And two groove rollers 20 and large and small weights 21 and 22.
[0015]
As shown in FIG. 1, the first and second wire reels 18 and 19 and the two groove rollers 20 are connected by a long wire row 11 via a large number of guide rollers.
A driving reel 23 is fixed to the 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 wire reels 18 and 19 are rotated via the power transmission belt 24, whereby the wire row 11 is led out. Or rolled up.
[0016]
The oscillating means 14 includes an oscillating disk 25 in which ends of a pair of groove rollers 20 are pivotally attached and a pulley is formed on the outer peripheral portion, and an oscillating motor 26 serving as a drive unit. . When the driving pulley 27 fixed to the output shaft is rotated by the swinging motor 26, the rotational force is transmitted to the swinging disc 25 via the timing belt 28, whereby the swinging disc 25 is moved to the right or Swing left by a predetermined angle. The oscillating disc 25 oscillates within a predetermined angle range in a clockwise direction or a counterclockwise direction in FIG. 1 within a plane including the disc surface around the central axis. The swing angle at this time is controlled by the swing angle adjustment of the control unit 15.
[0017]
The control unit 15 mainly determines the supply amount of the abrasive liquid supply means 12 to the wire row 11, the reciprocating speed of the wire row 11 by the reciprocating means 13, and the swing angle of the wire row 11 by the swinging means 14. Control. In addition, the control unit 15 includes a swing angle control means 15 a that controls the swing angle α of the wire row 11 according to the contact length between the wire row 11 and the ingot 29. Here, a block of single crystal silicon having a diameter of 200 mm pulled up by the CZ method is used as the ingot 29.
[0018]
More specifically, the control of the swing angle α by the swing angle control means 15a means that the swing angle is gradually increased as the contact length between the wire row and the ingot becomes longer. As the length becomes shorter, the swing angle is gradually reduced (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 shortened at the cutting start portion and the cutting end portion of the ingot 29.
In FIGS. 1 and 2, reference numeral 30 denotes a carbon bed for fixing the ingot 29.
[0019]
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 the wire supply / recovery motor 17, whereby the wire row 11 is led out or taken up from both reels 18 and 19. . As a result, the wire row 11 travels to the right or left at a speed of 300 to 1000 m / min every 1/30 minutes.
[0020]
During the reciprocating motion of the wire row 11, a swing direction switching command is issued from the control unit 15 every 1/15 minutes, and the swing direction of the wire row 11 is switched by the swing means 14. That is, the oscillating motor 26 rotates the oscillating disk 25 in a direction opposite to that of the oscillating disk 25 by a predetermined oscillating angle α (the oscillating angles α1 to α3 in FIGS. 2A to 2C). The pair of groove rollers 20 arranged is rotated in the opposite direction by the same angle.
The ingot 29 is in contact with the traveling wire row 11 and is gradually cut in a state where the abrasive fluid a is supplied onto the wire row 11 from the abrasive fluid supply means 12. Hereinafter, the cutting state of the ingot 29 will be described in more detail with reference to FIGS.
[0021]
At the time of cutting the ingot 29, the swing angle α of the wire row 11 is controlled by the swing angle control means 15a of the control unit 15 according to the contact length between the wire row 11 and the ingot 29 as described above. .
Specifically, as shown by a semi-elliptical line a in FIG. 3, the wire row 11 and the ingot 29 are arranged from the cutting start portion of the ingot 29 to the central portion of the ingot 29 where the wire row 11 contacts the ingot 29. As the contact length increases, the swing angle is gradually increased. On the other hand, the swing angle is gradually reduced from the central portion of the ingot 29 to the end of cutting of the ingot 29 as the contact length between the wire row 11 and the ingot 29 becomes shorter.
[0022]
This situation is shown in FIGS. FIG. 2 (a) shows a cutting work situation at a cutting start portion of the ingot 29 where the swing angle of the wire row 11 is α1, and FIG. 2 (b) shows the same central portion where the swing angle of the wire row 11 is larger than α2. FIG. 2C shows a cutting work situation at a cutting end portion of the ingot 29 having a small swing angle α3 of the wire row 11.
As a result, the abrasive fluid can easily enter, and the ingot 29 has a tendency to increase the width of the cutting groove. Since the wire row 11 can be cut into the wafer, the in-plane thickness unevenness in the cut wafer can be reduced, and a high-quality wafer can be obtained.
[0023]
Next, a wire saw and ingot cutting method according to a reference example of the present invention will be described with reference to FIGS. 1, 3, and 4.
4A is an enlarged cross-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 reference example of the present invention, and FIG. 4B is a main part showing a cutting state of a cutting center portion of the ingot. Fig. 4 (c) is an enlarged sectional view of a main part showing a cutting state of a cutting end portion of the ingot.
As shown in FIG. 1, reference numeral 10 ′ is a wire saw according to a reference example. There is a rocking stop means 15b for stopping the movement. The swing angle control means 15a of the first embodiment is deleted.
[0024]
In the use of the wire saw 10 ', when the cutting start portion of the ingot 29 is cut, the cutting start portion (from the cutting start end) is placed on the ingot 29 having a diameter of 200 mm as shown by a line b in FIG. (Between 25 mm), the swinging of the wire row 11 is stopped, and the wire row is then moved by the swinging means 14 between 25 and 175 mm in the central portion of the cut until reaching the end of cutting (between 25 mm from the end of cutting) 11 is swung by an angle of 1 °, and then the swing of the wire row 11 is stopped at the end of cutting.
As described above, since the swinging at the cutting start portion and the cutting end portion of the ingot 29 is stopped, as in the first embodiment, at the time of cutting the cutting start portion and the cutting end portion, It is possible to stably cut the wire row 11 without lateral shaking, and therefore, in-plane thickness unevenness in the cut wafer can be reduced.
[0025]
【The invention's effect】
As described above, according to the wire saw and ingot cutting method according to the present invention, when the contact length between the wire row and the ingot is short, for example, when cutting the cutting start portion or the cutting end portion of the ingot, 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 according to the contact length. As a result, even if it is a cutting start portion or a cutting end portion where the groove width of the cutting groove tends to be large, the wire row is stably cut without relatively sideways, and the in-plane thickness unevenness in the cut wafer is uneven. Can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a wire saw according to a first embodiment of the present invention.
FIG. 2A is an enlarged cross-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 a principal part expanded sectional view which shows the cutting state of the cutting center part of the ingot which concerns on 1st Example of this invention.
(C) is a principal part expanded sectional view which shows the cutting state of the cutting | disconnection end part of the ingot which concerns on 1st Example of this invention.
FIG. 3 is a graph showing the relationship between the cutting position of the ingot according to the first embodiment of the present invention and the swing angle of the wire row.
FIG. 4A is an enlarged cross-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 reference example of the present invention.
(B) is the principal part expanded sectional view which similarly shows the cutting state of the cutting center part of an ingot.
(C) It is a principal part expanded sectional view which similarly shows the cutting state of the cutting | disconnection end part of an ingot.
[Explanation of symbols]
10, 10 'wire saw,
11 Wire row,
12 Abrasive liquid supply means,
13 reciprocating means,
14 rocking means,
15 control unit,
15a rocking angle control means,
15b rocking stop means,
29 Ingot,
a Abrasive fluid.

Claims (2)

In a wire saw that cuts a cylindrical ingot substantially perpendicular to its axis by reciprocating the wire row while supplying the abrasive fluid,
Rocking means for relatively rocking the ingot and the wire row with a point on a straight line including the center of the ingot as a fulcrum within the cut surface of the ingot;
According to the contact length between the wire row and the ingot, the swing angle between the ingot and the wire row is a semi-elliptical curve with the cutting position as the elliptical long axis and the swinging angle as the elliptical short axis. A wire saw having swing angle control means for controlling so as to change along the axis. While supplying the abrasive fluid near the cutting part of the ingot, the wire row is reciprocated in a cutting plane substantially perpendicular to the axis of the ingot, and a point on a straight line including the center of the ingot is supported in this cutting plane. As an ingot cutting method for cutting the ingot into a plurality of wafers by relatively swinging the wire row and the ingot ,
Depending on the contact length between the wire row and the ingot, the swing angle of the wire row changes along a semi-elliptical curve with the cutting position as the elliptical long axis and the swing angle as the elliptical short axis. To control the ingot cutting method.

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