JP2571488B2 - Method and apparatus for cutting workpiece by wire saw - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for cutting a workpiece into a wafer by a wire saw.

[0002]

2. Description of the Related Art For example, in the field of semiconductor manufacturing, a plurality of silicon semiconductor wafers are obtained by thinly cutting a silicon single crystal ingot pulled up by a single crystal pulling apparatus in a direction perpendicular to an axis by an inner peripheral slicer. .

[0003] The recent tendency to increase the diameter of semiconductor wafers has made it difficult to cut ingots using conventional inner peripheral blade slicers. In addition, the cutting method using the inner peripheral blade slicer has a problem in that productivity is poor because the wafer is cut out one by one.

Therefore, a cutting method using a wire saw (particularly, a multi-wire saw) has been attracting attention in recent years.
In this cutting method, the work is cut into a wafer by pressing the work on a wire spirally wound between a plurality of rollers and moving the wire while supplying slurry to a contact portion between the work and the wire. According to this method, a large number (for example, several hundreds)
Wafers can be cut out.

[0005]

However, in the above-described cutting method using a wire saw, since a large number of wafers are cut at a time as described above, the amount of heat generated by friction between the wire and the work or the roller at the time of cutting is reduced. The friction heat generated in the bearing that supports the roller is transmitted to the roller, so that the roller extends in the axial direction due to thermal expansion, which cuts the pitch of the wire spirally wound around the roller. However, there is a problem that the thickness of the cut wafer becomes non-uniform, and large undulation occurs in the wafer, so that high processing accuracy cannot be secured. In particular, when the roller is formed by press-fitting a hollow resin cylinder into a cast iron core, the linear expansion coefficient of the resin cylinder is larger than that of the core, so that the roller is formed on the surface of the resin cylinder. Groove (groove into which wire should fit)
Is greatly changed during cutting, and the processing accuracy is further deteriorated.

Here, the undulation is shown in FIGS.
This will be described below with reference to FIG.

[0007] As shown in FIG.
When the workpiece W is cut by the wire 5, the cutting depth of the work W is x as shown in the figure, and the unevenness (displacement of the wire 5) in the vertical direction on the cut surface of the work W is measured by a contact type roughness measuring device (Perthen Co., Ltd.). Using a Pertometer or Kosaka roughness meter. As a result of this measurement, FIGS. 7 (b), (c),
When unevenness of the cut surface as shown in (d) is obtained, the undulation is defined as follows for each.

That is, in the graphs shown in FIGS. 7 (b), 7 (c) and 7 (d), the starting point S and the ending point E are connected by a straight line. Is a concave side, and for the result shown in FIG.
The sum (a + b) of the maximum value a on the convex side and the maximum value b on the concave side is defined as undulation. Similarly, for the results shown in FIGS. Value a, concave side maximum value b
Is defined as the swell for each.

The present invention has been made in view of the above problems, and an object thereof is to provide a method and a method for cutting a workpiece by a wire saw, which can always stably obtain a wafer having a small undulation and a uniform thickness. It is to provide a device.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, a work is pressed against a wire spirally wound between a plurality of rollers, and slurry is supplied to a contact portion between the work and the wire. In the cutting method of cutting the workpiece into a wafer by moving the wire while moving,
An axial displacement of the roller is detected, and the supply temperature of the slurry is controlled based on the detected value.

[0011] Further, the present invention provides a method in which a work is pressed against a wire spirally wound between a plurality of rollers and the wire is moved while supplying slurry to a contact portion between the work and the wire. In a cutting device for cutting the roller into a wafer, a displacement detecting means for detecting the axial displacement of the roller, a temperature adjusting means for adjusting the temperature of the slurry, and the axial displacement of the roller detected by the displacement detecting means. A control means for controlling the temperature adjusting means based on the control means is provided.

[0012]

In the cutting method using a wire saw, a slurry is supplied to a contact portion between the work and the wire during cutting, and the slurry also functions as a cooling medium for cooling the wire and the rollers.

Incidentally, it has been confirmed that there is a certain correlation between the slurry supply temperature and the axial displacement of the roller. Therefore, the axial displacement of the roller is detected as in the present invention, and this detection is performed. If the slurry supply temperature is controlled based on the value, the axial displacement of the roller can be kept constant. As a result, even if a large number of wafers are cut out at once, without being affected by frictional heat,
The pitch of the wire row wound between the rollers (wafer cutout thickness) can be kept constant, and a large number of wafers with a constant thickness and small undulation can be cut out at a time from the work. , High processing accuracy can be secured.

[0014]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of a cutting apparatus according to the present invention. In the drawing, reference numeral 1 denotes a wire saw main body, and details of the configuration of the wire saw main body 1 are shown in FIGS.
Is shown in

Here, the configuration of the wire saw main body 1 is shown in FIG.
A description will be given based on FIG.

FIG. 2 is a perspective view of a main part of the wire saw main body 1, and the wire saw main body 1 has three rollers 2,
A special piano wire having a wire diameter of about 0.08 to 0.25 mm is formed between the rollers 2, 3, and 4 by arranging the rollers 3, 4 in parallel and rotatably at respective apexes of the triangle. One wire 5 is spirally wound at a predetermined pitch.

A work W such as a single crystal ingot held by a work holder 6 is set between the upper two rollers 2 and 3 and above these rollers 2 and 3. The work W moves up and down together with the work holder 6 when the work holder 6 is moved up and down by driving means (not shown).

The lower roller 4 is a driving roller, which is rotated by a driving motor 7 in the forward and reverse directions.

The configuration of the end of the roller 2 is shown in FIG. 3. The roller 2 is formed by press-fitting a hollow resin cylinder 9 into a core 8 made of cast iron. The main body frame 11 is rotatably supported via a bearing 10. Grooves 12 are spirally formed on the outer periphery of the resin cylinder 9 at a predetermined pitch (desired wafer thickness + cut allowance), and the wire 5 is fitted into the groove 12. Although the configuration of the roller 2 has been particularly described above, the configuration of the other rollers 3 and 4 is the same as that of the roller 2.

As shown in FIG. 3, the end surface of the resin cylinder 9 of the roller 2 is made of metal (SS41, SUS31).
6), a ring-shaped measuring plate 13 is attached, and an eddy current type non-contact displacement meter 14 is attached to the main body frame 11 side in close proximity to the measuring plate 13.

Further, as shown in FIG.
A nozzle 16 for ejecting a slurry (abrasive liquid) 15 (see FIG. 4) is provided above the roller, and a slurry reservoir 17 for receiving the slurry 15 ejected from the nozzle 16 is provided between the rollers 2 and 3. Have been. The slurry 15 is
This is a mixture of lapping abrasive grains and a grinding fluid, which is stored in a slurry tank 18 shown in FIG.

By the way, as shown in FIG.
A pump 22 is provided in the middle of 1, and these slurry supply pipes 20 and 21 are connected to the nozzles 16 provided in the wire saw main body 1, respectively.
A slurry recirculation pipe 23 extending from the slurry reservoir 17 is connected to a slurry tank 18. Further, the slurry pipe 2 drawn out of the slurry tank 18
In the middle of 4, a pump 25 is interposed, the slurry pipe 24 is connected to the inlet side of the heat exchanger 26, and the slurry pipe 27 led out from the outlet side of the heat exchanger 26 is connected to the slurry tank 18. ing.

On the other hand, in FIG. 1, reference numeral 28 denotes a cooling water tank, and 29 denotes a chiller (refrigerator).
The cooling water in 8 is sent to the chiller 29 by the pump 30 to be cooled, and then returned to the cooling water tank 28. A cooling water is supplied from a cooling water tank 28 by a pump 31 to a cooling water pipe 32 through a flow control valve 33 and a flow meter
The cooling water whose temperature has been increased by the heat exchange with the slurry 15 in the heat exchanger 26 returns to the cooling water tank 28 from the cooling water pipe 35.
Note that a part of the cooling water from the cooling water tank 28 is supplied from the bypass pipe 36 to the flow control valve 33 without passing through the heat exchanger 26.
, Is returned directly to the cooling water tank 28 and is not used for cooling the slurry 15.

The cooling water pipes 32, 35, the slurry pipes 24, 27, the slurry recirculation pipe 23, and the slurry supply pipe 21 have temperature sensors 37, 38, 3 respectively.
9, 40, 41, and 42 are provided, respectively. The cooling water temperature detected by these temperature sensors 37 to 42 and the cooling water amount detected by the flow meter 34 are input to a CPU 50 as control means. Further, the axial displacement of the roller 2 detected by the non-contact displacement meter 14 provided on the wire saw main body 1 is also input to the CPU 50.

Next, the operation of the present cutting device will be described.

In the wire saw main body 1, the work W held by the work holder 6 moves down and is pressed by the wire 5 stretched between the rollers 2 and 3. Then, in this state, the drive motor 7 is driven to drive the drive roller 4.
Are alternately rotated in the forward and reverse directions, and simultaneously, when the slurry 15 is supplied from the nozzle 16 to the contact portion between the work W and the wire 5, the work W is reciprocated as shown in FIG. The workpiece W is cut into a predetermined thickness by the lapping action, and a plurality of wafers are cut out from the work W at a time.

By the way, in the cutting of the work W by the present cutting device, the slurry 15 is supplied to the contact portion between the work W and the wire 5 during the cutting as described above, and the slurry 15 is supplied to the rollers 2, 3, 4 and It also functions as a cooling medium for cooling the wire 5.

Incidentally, it has been confirmed that there is a certain correlation between the supply temperature of the slurry 15 and the axial displacement of the rollers 2, 3, and 4, as shown in FIG. That is, FIG. 5 shows the temporal change of the axial displacement of the roller when the supply temperature of the slurry is changed with time as shown in the drawing. It can be seen that the directional displacement follows a relatively slow change.

In this embodiment, the axial displacement of the roller 2 is detected by the non-contact displacement meter 14 as described above, and the detected value is input to the CPU 50. And C
The PU 50 controls the supply temperature of the slurry 15 so that the input axial displacement of the roller 2 is constant. Specifically, the supply temperature of the slurry 15 is controlled by adjusting the refrigerating capacity of the chiller 29 and adjusting the amount of cooling water by the flow control valve 33. In other words, chiller 2
The cooling water temperature is adjusted by adjusting the refrigerating capacity and the cooling water amount of the slurry 9, and the cooling capacity of the slurry 15 in the heat exchanger 26 is adjusted by adjusting the cooling water temperature, whereby the supply temperature of the slurry 15 is controlled. In this embodiment, the supply temperature of the slurry 15 is controlled by adjusting both the refrigerating capacity of the chiller 29 and the amount of cooling water, but may be adjusted by adjusting either one of them.

FIG. 6 is a diagram showing the change over time in the axial displacement of the roller 2 when the supply temperature of the slurry 15 is controlled in the present embodiment. It can be seen that the axial displacement can be kept substantially constant. Therefore, as shown in FIG. 6, the cutting of the workpiece W may be started at a time when the axial displacement of the roller 2 starts to be constant.

As described above, the axial displacement of the roller 2 (that is, all the rollers 2, 3, and 4) can be kept constant during the cutting, so that even if a large number of wafers are cut out from the work W at one time. The pitch of the wire 5 wound between the rollers 2, 3, and 4 (the thickness of the cut out wafer) can be kept constant without being affected by frictional heat.
Thus, a large number of wafers having a constant thickness and small undulation can be stably cut out at a time, and high processing accuracy can be secured.

[0033]

As is apparent from the above description, according to the present invention, a work is pressed against a wire spirally wound between a plurality of rollers, and slurry is supplied to a contact portion between the work and the wire. In the cutting method of cutting the workpiece into a wafer by moving the wire while moving,
Displacement detecting means for detecting the axial displacement of the roller, controlling the supply temperature of the slurry based on the detected value, detecting the axial displacement of the roller, and temperature adjusting means for adjusting the temperature of the slurry. Since a work cutting device is configured by providing a control means for controlling the temperature adjusting means based on the axial displacement of the main roller detected by the displacement detecting means, a wafer having a small waviness and a uniform thickness is always stable. Thus, the effect that the processing accuracy can be further improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a cutting device according to the present invention.

FIG. 2 is a perspective view of a main part of a wire saw main body.

FIG. 3 is a cutaway side view of a roller end.

FIG. 4 is an explanatory diagram showing a work of cutting a workpiece by a cutting device.

FIG. 5 is a diagram showing a correlation between a slurry supply temperature and an axial displacement of a roller.

FIG. 6 is a diagram showing a temporal change in axial displacement of a roller due to control of a slurry supply temperature.

FIGS. 7A to 7D are diagrams for explaining the definition of undulations.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wire saw main body 2, 3, 4 Roller 5 Wire 13 Measuring plate 14 Non-contact displacement meter (Displacement detecting means) 15 Slurry 29 Chiller (Temperature adjusting means) 50 CPU (Control means) W Work

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuo Hayakawa 762, Ashikado, Gunma-cho, Gunma-gun, Gunma Prefecture Inside Sanmasumi Hanko Kogyo Co., Ltd. (56) References JP-A-5-200734 (JP, A)

Claims (3)

(57) [Claims] 1. A work is pressed into a wire spirally wound between a plurality of rollers, and the wire is moved while supplying slurry to a contact portion between the work and the wire, so that the work is formed into a wafer shape. In the cutting method for cutting, the axial displacement of the roller is detected, and the supply temperature of the slurry is controlled based on the detected value. 2. A work is pressed into a wire spirally wound between a plurality of rollers, and the wire is moved while supplying slurry to a contact portion between the work and the wire, thereby forming the work into a wafer shape. In a cutting device for cutting, a displacement detecting means for detecting an axial displacement of the roller, a temperature adjusting means for adjusting a temperature of the slurry, and the temperature based on an axial displacement of the roller detected by the displacement detecting means. A cutting device, further comprising control means for controlling an adjusting means. 3. The displacement detecting means comprises an eddy current type non-contact displacement meter, wherein the non-contact displacement meter detects a displacement of a metal measuring plate attached to an end face of the roller. 3. The cutting device according to claim 2, wherein