JPH10138230A - Wire saw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire saw which is capable of further improving cutting accuracy compared with a conventional wire saw. SOLUTION: This wire saw consists of a wire bobbin 12 for holding wire 11 and at least, two rollers 24 around which the wire 11 to be supplied from the wire bobbin 12 is wound. Rows 14 of wire are formed between the two rollers 24 and are fed in the longitudinal direction to cut a work to be fabricated through pressing the work against the rows 14 of wire while supplying a cutting liquid. In this case, a temperature control device 15 is mounted on the wire bobbin 12 to control the temperature of the wire 11 held in the wire bobbin 12 through the wire bobbin 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a wire saw.

[0002]

2. Description of the Related Art A wire saw is a cutting device for cutting a long workpiece into a thin plate. According to the wire saw, a large number of thin plates having a predetermined thickness can be simultaneously sliced, so that the cutting efficiency can be greatly improved.

In the field of semiconductors, a wire saw is used when slicing a wafer from an ingot. According to the wire saw, for example, about 180 wafers can be sliced simultaneously from one ingot.

The wire saw has a pair of rollers arranged in parallel, and has a configuration in which a wire row is formed at a predetermined pitch therebetween. Then, the roller is rotated to feed the wire in the longitudinal direction, and the workpiece is pressed against the wire row to perform cutting. At that time, a processing liquid containing abrasive grains is appropriately supplied between the workpiece and the wire.

[0005] A single cut of a silicon semiconductor ingot requires several hours, for example, even for a 5-inch ingot. For this reason, in order to improve the cutting accuracy, that is, the surface accuracy of the wafer, the cutting conditions must be kept constant for a long time.

Conventionally, various wire saws and cutting methods have been proposed to keep the cutting conditions constant for a long time. Examples thereof are disclosed in JP-A-5-154831,
Japanese Patent Application Laid-Open Nos.

The roller support device for a wire saw disclosed in Japanese Patent Application Laid-Open No. 5-148331 is configured to cool the support device and suppress the heating thereof.

[0008] The wire saw and its cutting method disclosed in Japanese Patent Application Laid-Open No. 5-147023 have a configuration in which a processing liquid is also applied to a roller support device to control the temperature thereof.

The wire saw disclosed in Japanese Patent Application Laid-Open No. 5-146968 has a structure in which a synthetic resin is attached to a guide groove of a roller to reduce fluctuations in the groove pitch due to heating.

[0010]

The heat generated during the operation of the wire saw may be caused by the following frictional heat. These include frictional heat generated between the wire and the workpiece, frictional heat generated between the wire and the roller, and frictional heat of the roller support mechanism.

[0011] Under the influence of these heats, the pitch of the wire row changes delicately, or the wire expands and contracts locally, causing a cutting error. Such a cutting error has become a greater problem in the case of a wire saw having a large number of wire rows and a large number of cuts at one time.

According to the wire saw and the cutting method disclosed in the above-mentioned publication, it is possible to suppress the cutting error caused by the frictional heat to some extent. However, the conventional wire saw still has the following problems.

Reference is now made to FIGS. 3 to 5, which show the cutting accuracy of a silicon wafer cut with a conventional wire saw. FIG.
Is the variation of the “center thickness”, and FIG.
FIG. 5 shows the variation of “sludge”. The numbers on the horizontal axis in the figure indicate the number counted from one end of the ingot.

As can be seen from FIGS. 3 to 5, the conventional wire saw has a problem that the cutting accuracy at both ends of the workpiece is extremely poor.

Further, in order to provide a high-accuracy wafer corresponding to high integration at a low cost, it is also required to further improve the ingot cutting accuracy.

[0016] In view of such problems of the prior art, an object of the present invention is to provide a wire saw capable of further improving the cutting accuracy as compared with a conventional wire saw.

[0017]

According to a first aspect of the present invention, a wire bobbin (12) accommodating a wire (11) and at least two rollers (24) for winding the wire (11) supplied from the wire bobbin (12). And a wire row (14) is formed between the two rollers (24), the wire (11) is fed in the longitudinal direction, and the workpiece is pressed against the wire row (14) while supplying a working liquid to cut. In the wire saw configured as described above, a temperature controller (15) is set on the wire bobbin (11), and the temperature of the wire (11) housed in the wire bobbin (12) is controlled by the temperature controller (15) via the wire bobbin (12). The gist of the present invention is a wire saw characterized by having such a configuration.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of a wire saw according to the present invention.

The wire saw 10 includes a wire bobbin 12 for accommodating the wire 11 and at least two rollers 24 around which the wire 11 supplied from the wire bobbin 12 is wound. The two rollers 24 form the roller pair 13.

The wire bobbins 12 are provided one by one on one side and the other side of the roller pair 13. When the wire bobbin 12 on one side supplies the wire 11, the other side performs an operation of collecting the wire 11 sent from the wire pair 13. Each wire bobbin 12 is driven at a predetermined speed by a drive motor 22.

Below the roller pair 13, a main roller 2 is provided.
6 are arranged. The main roller 26 is a drive motor 4
0 and is driven at a predetermined speed. Wire 1
1 has three rollers (main roller 26 and roller pair 1)
It is wound around 3).

Above the roller pair 13, a working liquid supply means 23 is arranged. From the working fluid supply means 23, a working fluid containing abrasive grains is appropriately supplied. A box-shaped collection container 32 is arranged between the roller pair 13. Collection container 32
Is provided with a temperature sensor 39. The temperature of the working fluid is adjusted to a desired temperature by temperature adjusting means (not shown) based on the temperature of the collected working fluid and the temperature of the wire 11 near the roller 24.

A tension adjusting mechanism 1 for controlling the tension of the wire 11 is provided between the roller pair 13 and each wire bobbin 12.
9 are provided.

A large number of wire rows 1
4 are formed at a constant pitch in parallel with each other. The two rollers 24 and the main roller 26 constituting the roller pair 13 are cylindrical, and a guide groove (not shown) for guiding the wire 11 is formed on the outer periphery thereof. The guide groove is lined with a synthetic resin as necessary for heat insulation and prevention of breakage of the wire.

A holder 21 for setting a workpiece 20 such as an ingot is disposed above the wire row 14.
The holding unit 21 is movable perpendicularly to a plane formed by the wire row 14. The holding unit 21 is moved while the wire 11 is fed in the longitudinal direction, and the workpiece 20 is pressed against the wire row 14 and cut.

The roller 24 is provided with a temperature sensor 38 and a cooling means (not shown), so that the temperature of the roller and the wire around the roller can be controlled. The temperature of each roller is controlled so that there is no temperature difference between both ends and the center, and the temperature does not change until the end of cutting. The temperature control of the main roller 26 can be similarly performed.

As shown in FIG. 2, each wire bobbin 12 is provided with a temperature control device 15 so that the temperature of the wire 11 accommodated in the wire bobbin 12 can be appropriately controlled.

The temperature control device 15 comprises a heating means 16 having a heater wire 36, a water-cooling type cooling means 17, a temperature sensor 28, and a control means 25 for controlling these. The control means 25 is also connected to a temperature sensor 38 of the roller 24 (main roller 26) and a temperature sensor 39 of the collected working fluid.

The wire bobbin 12 has a thread winding shape as a whole, and large diameter portions 27 for preventing the wire from falling off are formed at both ends. Temperature sensors 2 are provided inside the large diameter portions 27 at both ends.
8 is embedded. The temperature sensor 28 is a control unit 25
It is connected to the.

The cooling means 17 comprises a cooling pipe 37, a cooler 31, a water tank 32, and a pump 33.
The cooling pipe 37 is arranged on the central axis of the wire bobbin 12. The cooling means 17 is controlled by the control means 25.

The inner surface of the wire bobbin 12 has a heater wire 3
6 are arranged. The heater wire 36 is heated by the heater 35. The heater 35 is controlled by the control means 25.

The temperature of the wire housed in the wire bobbin 12 is preferably adjusted to be substantially equal to the temperature of the wire in the wire row 14. For this purpose, the wire 1 stored in the wire bobbin 12 is referred to the temperature of the wire 11 detected by the temperature sensor 38 provided on the roller 24.
1 may be controlled. At this time, the temperature detected by the temperature sensor 39 for the collected working fluid can also be referred to in an empirical manner. For example, the wire temperature can be controlled to be the same as the abrasive grain temperature.

The point of the present invention is that by performing such temperature control in accordance with the instruction of the control means 25, the temperature of the wire 11 itself which is directly in contact with the workpiece 20 is controlled and the temperature of the entire wire 11 is kept constant. It is.

As described above, by controlling the temperature of the entire wire 11, the cutting conditions near both ends of the wire row 14 can be made substantially the same as the cutting conditions inside the wire row 14.

Further, since the temperature of the wire 11 is controlled through the wire bobbin 12, the temperature of the wire bobbin itself is also controlled, so that the overall temperature control and the stabilization of the wire feed can be achieved.

In FIG. 2, the heater wire 16 is provided only in the cylindrical portion, but the heater wire 16 may partially extend to the large diameter portion 27. Similarly, the installation position of the temperature sensor 28 can be changed and may be embedded near the surface of the cylindrical portion of the wire bobbin 12.

Further, the heating means 16 can be constituted by a hot water system. In that case, the cooling means and the heating means can be combined into one.

Now, using the wire saw of the present invention shown in FIG. 1, a silicon wafer was cut out from a silicon ingot, and the cutting accuracy of the wafer was measured in the same manner as in the case of obtaining FIGS. The wire temperature at the wire bobbin was controlled with reference to the temperature of the temperature sensor 38.

As a result, the variation of “thickness” was 97.8% within ± 15 μm in the conventional wire saw (see FIG. 3). On the other hand, in the embodiment of the present invention, ± 1
Good results were obtained with 100% within 5 μm. FIG.
See FIG.

The variation of "TTV" was 97.3% within 25 μm in the conventional example (see FIG. 4), whereas 99.6% was within 25 μm in the embodiment of the present invention.
And was good.

The variation of "warp" was as good as 86.9% within 20 μm in the conventional example, and 98.8% within 20 μm in the embodiment of the present invention.

The temperature of the abrasive grains (working liquid) was set to 28 ° C. in both the embodiment and the conventional example. When the wire temperature was measured, it was 15 to 35 ° C. in the conventional example, and 25 to 35 ° C. in the example.
32 ° C.

As described above, according to the wire saw of the present invention, it was confirmed that the temperature change of the wire can be suppressed to a small value, and therefore, the wafer can be cut with high accuracy.

[0044]

The wire of the present invention is a wire bobbin (1
Since the temperature control device is set in 2) and the temperature of the wire (11) housed in the wire bobbin (12) is controlled by the temperature control device (15) via the wire bobbin (12), the wire train (14) is used. Wire (1)
The temperature of 1) can be controlled.

Therefore, the temperature of the entire wire (11) can be appropriately controlled, and the cutting accuracy particularly near both ends of the workpiece (20) can be improved.

In order to control the temperature of the wire (11) via the wire bobbin (12), the wire bobbin (1)
2) The temperature itself is also controlled, so that overall temperature control and stabilization of the wire feed can be achieved.

The present invention is not limited to the above embodiment. For example, a configuration may be adopted in which the workpiece is moved upward to perform cutting. Further, the number of rollers is not limited to three.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram showing a wire bobbin and a temperature control device of FIG. 1;

FIG. 3 is a graph showing the accuracy of a wafer cut by a conventional wire saw.

FIG. 4 is a graph showing the accuracy of a wafer cut by a conventional wire saw.

FIG. 5 is a graph showing the accuracy of a wafer cut by a conventional wire saw.

FIG. 6 is a graph showing the accuracy of a wafer cut by the wire saw of the present invention.

FIG. 7 is a graph showing the accuracy of a wafer cut by the wire saw of the present invention.

FIG. 8 is a graph showing the accuracy of a wafer cut by the wire saw of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Wire saw 11 Wire 12 Wire bobbin 14 Wire row 15 Temperature control device 16 Heating means 17 Cooling means 28 Temperature sensor 24 Roller 25 Control means 26 Main roller 38 Temperature sensor 39 Temperature sensor

Claims (4)

[Claims] 1. A wire bobbin (12) for receiving a wire (11) and at least two rollers (2) for winding the wire (11) supplied from the wire bobbin (12).
4) is provided between the two rollers (24).
4), the wire (11) is fed in the longitudinal direction, and the workpiece (20) is pressed against the wire row (14) while supplying the working fluid to cut the wire bobbin (11). A wire saw, wherein a control device (15) is set, and the temperature of the wire (11) housed in the wire bobbin (12) is controlled by the temperature control device (15) via the wire bobbin (12). 2. A configuration in which a temperature sensor (38) is provided at or near the roller (24) and the temperature of the wire (11) housed in the wire bobbin (12) is controlled with reference to the detection result. The wire saw according to claim 1, wherein: 3. A temperature sensor (39) for detecting the temperature of the collected machining fluid is provided, and the temperature of the wire (11) housed in the wire bobbin (12) is controlled with reference to the detection result. The wire saw according to claim 1, wherein: 4. The temperature control device (15) includes a heater wire (3).
The wire saw according to claim 1, further comprising a heating means (16) utilizing the method (6), a water-cooling type cooling means (17), and a temperature sensor (28) installed on the wire bobbin (12).