JP2571489B2 - 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, as described above, a large load is applied to the bearing portion that supports the journal portions at both ends of the roller in order to cut out a large number of wafers at once.
Therefore, large frictional heat is generated in the bearing portion. Then, since this frictional heat is transmitted from the journal portion to the roller, the temperature at both ends of the roller increases, and the amount of thermal expansion at both ends becomes larger than that at the center portion. The thickness of the wafer cut by the cut wire row becomes thick, the thickness of the cut wafer becomes uneven, and the thickness of the wafer cut by the wire row on both ends of the roller becomes non-uniform. There is a problem that large swells occur. In particular, when the roller is formed by press-fitting a hollow resin cylinder into a cast iron core, the above-described problem becomes more remarkable because the linear expansion coefficient of the resin cylinder is larger than that of the core. .

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. 8 (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. 8B, 8C, and 8D, the starting point S and the ending point E are connected by a straight line, and the upper part of the straight line is defined as a convex side, and the lower part is defined as a convex side. Is defined as the concave side, and for the result shown in FIG. 8B, 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. For the results shown in FIGS. 8C and 8D, the maximum value a on the convex side and the maximum value b on the concave side are defined as undulations for each.

The present invention has been made in view of the above problems, and an object thereof is to stably obtain a large number of wafers having a small undulation and a uniform thickness without variation. An object of the present invention is to provide a method and an apparatus for cutting a work using a wire saw.

[0010]

According to a first aspect of the present invention, a work is pressed against a wire spirally wound between a plurality of rollers, and slurry is applied to a contact portion between the work and the wire. In the cutting method of cutting the work into a wafer by moving the wire while supplying the work, the work is pressed to a central portion of the wire row stretched between the rollers excluding both ends in the roller axial direction, and the wire row is stretched. The workpiece is cut at the center in the roller axial direction.

[0011] In a second aspect of the present invention, 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 apparatus for cutting a workpiece into a wafer, a pitch of both ends in a roller axial direction of a wire row stretched between the rollers is set smaller than that of a central part in a roller axial direction.

Further, the third invention is to press a work against a wire spirally wound between a plurality of rollers, and to move the wire while supplying slurry to a contact portion between the work and the wire. In a cutting device for cutting a work into a wafer, a heat insulating material is interposed between journal portions at both ends of the roller.

[0013]

[Function] Since the center of the roller is far from the bearing, which is a heat source, and the frictional heat generated in the bearing is conducted from both ends of the roller, the temperature at both ends of the roller is sharply increased, and the temperature at the center of the roller is small. And it is constant. Therefore, the amount of thermal expansion at the center of the roller is small and constant. As a result, the pitch of the wire row stretched at both ends of the roller gradually increases, while the pitch of the wire row stretched at the center of the roller is kept substantially constant.

Therefore, as in the first invention, a wire row stretched at both ends of the roller having a large thermal expansion amount is used as a dummy. In this case, the workpiece is not cut, and the wire row stretched at the center of the roller. When the workpiece is cut by the method, a large number of wafers having a constant thickness and a small undulation can be stably cut out from the work at a time, and the thickness of the cut wafer does not vary.

Further, if the pitch of both ends in the roller axis direction of the wire array is set smaller than that of the center portion in the roller axial direction as in the second aspect of the present invention, the thermal expansion of both ends of the roller due to frictional heat causes Since the pitch at both ends in the roller axial direction becomes larger with time and becomes equal to the pitch of the wire row at the center of the roller, the pitch of the wire row becomes uniform over the entire width in the roller axial direction. As a result, similarly to the first invention, a large number of wafers having a constant thickness and a small undulation can be stably cut out at once from the work, and the thickness of the cut out wafers does not vary.

Further, according to the third invention, the conduction of frictional heat generated in the journal portion to the roller itself is blocked by the heat insulating material, so that the temperature of the roller is maintained substantially uniform over the entire width in the axial direction. Accordingly, the pitch of the wire row is also substantially uniform over the entire width in the roller axial direction, and the same effects as those of the first and second aspects can be obtained.

[0017]

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

FIG. 3 shows the present invention (first, second and third inventions).
FIG. 1 is a perspective view of a main part of a wire saw main body 1 of a cutting apparatus to which the present invention is applied. In the wire saw main body 1, three rollers 2, 3, and 4 are arranged at respective apexes of a triangle in a parallel and rotatable manner. A single wire 5 made of a special piano wire having a wire diameter of about 0.08 to 0.25 mm is spirally wound at a predetermined pitch between these rollers 2, 3, and 4. .

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 the 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 forward and reverse by a driving motor 7.

Further, a nozzle 16 for ejecting a slurry (abrasive liquid) 15 (see FIG. 2) is provided above the rollers 2 and 3. A slurry pool 17 for receiving the slurry 15 is provided. The slurry 15 is a mixture of lapping abrasive grains and a grinding fluid, and is stored in a slurry tank (not shown).

Here, the embodiment of the first invention is shown in FIG.
A description will be given based on (b) and (c) and FIG. FIG.
(A) is a cutaway view of the roller 2 portion of the wire saw main body 1, FIG. 1 (b) is a diagram showing an axial temperature distribution of the roller 2,
FIG. 1C is a diagram illustrating the axial displacement of the roller 2, and FIG. 2 is an explanatory diagram illustrating a work of cutting a workpiece by a cutting device.

As shown in FIG. 1 (a), the roller 2 is formed by press-fitting a hollow resin cylinder 9 into a core 8 made of cast iron.
0 and rotatably supported on the main body frame 11. 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.

Next, the cutting method according to the first invention 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 (see FIG. 3). Then, in this state, when the drive motor 7 is driven to alternately rotate the drive roller 4 forward and backward, and at the same time, the slurry 15 is supplied from the nozzle 16 to the contact portion between the work W and the wire 5, as shown in FIG. Thus, the work W is
The workpiece is cut into a predetermined thickness by the lapping action of the reciprocating wire 5 and the slurry 15, and a plurality of wafers are cut out of the work W at a time.

In cutting the work W, the frictional heat generated in the bearing 10 supporting the journal 8a of the cored bar 8 of the roller 2 is transmitted to the roller 2 from both ends through both the journals 8a. Therefore, the amount of conduction of frictional heat to the center of the roller 2 is small, and as shown in FIG. 1B, the temperature at both ends of the roller 2 is high, and the temperature distribution at the center except for both ends is constant and substantially constant. It is uniform. Accordingly, as shown in FIG. 1 (c), the axial displacement due to the thermal expansion of both ends of the roller 2 is large, but the axial displacement at the central portion is kept constant and substantially uniform. As a result, the pitch of the wires 5 stretched at both ends of the roller 2 gradually increases, while the pitch of the wires 5 stretched at the center of the roller 2 is kept substantially constant. This is the same for the other rollers 3 and 4.

Therefore, in the first invention, a row of fifteen to twenty turns of the wire 5 stretched at both ends of the roller 2 having a large thermal expansion is used as a dummy. The work W is cut by a row of wires 5 stretched in the center of the work 2. Therefore, according to the first aspect of the present invention, the pitch of the rows of the wires 5 to be cut can always be kept constant. As a result, a large number of wafers having a constant thickness and a small undulation can be removed from the workpiece W once. And the thickness of the cut wafer does not vary.

Here, the variation σ of the thickness and the undulation actually measured for the wafer cut by the method of the present invention.
Are shown in the following table in comparison with those of wafers cut by the conventional method.

[0029]

[Table 1] Next, an embodiment of the second invention will be described with reference to FIG.
FIG. 4 is a cutaway view of the roller portion of the wire saw main body. In this figure, the same elements as those shown in FIG. 1A are denoted by the same reference numerals.

In the second aspect of the present invention, the work W is pressed over the entire width of the row of the wires 5, but as shown in FIG.
The pitch P1 of the wire 5 (groove 12) at both axial end portions a of the rollers 2 (3, 4) is the pitch P2 at the axial center portion b.
(P1 <P2).

By the way, as in the first embodiment of the present invention, the frictional heat generated in the bearing 10 during the cutting of the work W is transmitted to the rollers 2 (3, 4) from both ends through the two journal portions 8a. Therefore, as in the first embodiment of the present invention (see FIG. 1B), the temperature at both ends a of the roller 2 (3, 4) is high, and the temperature distribution at the center b excluding both ends a is It is constant and almost uniform. Therefore, the high temperature roller 2
The axial displacement due to the amount of thermal expansion at both ends a of (3, 4) becomes larger than that at the center b (see FIG. 1C), and the pitch P1 of the wires 5 stretched at both ends a gradually increases. On the other hand, the pitch P2 of the wire 5 stretched at the central portion b of the roller 2 (3, 4) is slightly increased, but is kept substantially constant.

However, in the second invention, as described above, the pitch P1 of the wire 5 (groove 12) at both axial end portions a of the rollers 2 (3, 4) is larger than the pitch P2 at the axial center portion b. Since it is set to be small (P1 <P2), the wire 5 is expanded due to thermal expansion of both ends a of the roller 2 due to frictional heat.
The pitch P1 of both ends a in the roller axial direction increases with time, and eventually becomes equal to (P1 ≒ P2) the pitch P2 of the wire 5 in the central portion b of the roller 2 (3, 4). , P2 become substantially uniform over the entire width in the roller axial direction. As a result, similarly to the first invention, a large number of wafers having a constant thickness and a small undulation can be stably cut out from the work W at a time, and the thickness of the cut out wafers does not vary.

Next, an embodiment of the third invention will be described with reference to FIGS. 5 is a cutaway view of a roller portion of the wire saw main body, FIG. 6 is an enlarged detailed view of a portion A in FIG. 5, and FIG.
FIG. 7 is a sectional view taken along the line BB in FIG. 6, and in these figures, the same elements as those shown in FIG.

In the third invention, the roller 2 (3, 4)
The grooves 12 are formed at the same pitch P, so that the pitch of the wires 5 is also kept at a constant value P. However, a heat insulating material such as ceramic is provided in the middle of the journal portion 8a of the roller 2 (3, 4). Material 18 is interposed. That is, as shown in FIG. 6, the journal portion 8a of the roller 2 (3, 4) is divided into two pieces 8a-1 and 8a-2, and between the divided pieces 8a-1 and 8a-2. The heat insulating material 18 is interposed, and the two split pieces 8a-1 and 8a-2 are connected to the flanges 19 and 20 bonded to their opposite ends by a plurality of bolts 21 and nuts 22, respectively. The connection is integrated. Then, both end surfaces of the heat insulating material 18 (contact surfaces of the journal portion 8a with the divided pieces 8a-1 and 8a-2).
7, ring-shaped grooves 23 and 24 and a circular groove 25 are formed concentrically.

According to the third aspect of the present invention, the conduction of the frictional heat generated in the bearing 10 to the rollers 2 (3, 4) is blocked by the heat insulating material 18, so that the rollers 2
The temperature of (3, 4) is maintained substantially uniform over the entire width in the axial direction, so that the pitch P of the wire 5 is also substantially uniform over the entire width in the axial direction of the roller, and the same effects as those of the first and second inventions are obtained. can get. Particularly, in the present embodiment, since the grooves 23, 24, and 25 are formed on both end surfaces of the heat insulating material 18 as described above, the heat insulating material 18 and the journal portion 8a (the divided pieces 8a-
1, 8a-2), and the air in the grooves 23, 24, 25 constitutes a heat insulating layer, so that heat conduction to the roller 2 is more reliably blocked.

[0036]

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,
The work is pressed to the center of the wire row stretched between the rollers except for both ends in the roller axis direction, and the work is cut at the center in the roller axis direction of the wire row, or spirally formed between a plurality of rollers. In a cutting device that cuts a work into a wafer by pressing the work on a wire wound around and moving the wire while supplying slurry to a contact portion between the work and the wire, the work is stretched between the rollers. The pitch of both ends of the wire row in the roller axis direction is set to be smaller than that of the center part in the roller axis direction, or a heat insulating material is provided at the journals at both ends of the roller, so that undulation is small and the thickness is uniform. There is an effect that a large number of wafers having no variation can be stably obtained at once.

[Brief description of the drawings]

1 (a) is a broken sectional view of a roller portion of a wire saw main body of a cutting device for explaining a first invention, FIG. 1 (b) is a diagram showing an axial temperature distribution of the roller, and FIG. It is a figure which shows an axial direction displacement.

FIG. 2 is an explanatory view showing a work of cutting a workpiece by a cutting device.

FIG. 3 is a perspective view of a main part of a wire saw main body.

FIG. 4 is a cutaway view of a roller portion of the cutting device according to the second invention.

FIG. 5 is a cutaway view of a roller portion of the cutting device according to the third invention.

FIG. 6 is an enlarged detail view of a portion A in FIG. 5;

FIG. 7 is a sectional view taken along the line BB of FIG. 6;

FIGS. 8A to 8D are diagrams for explaining the definition of undulation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wire saw main body 2, 3, 4 Roller 5 Wire 15 Slurry 18 Heat insulating material 23-25 Groove formed in heat insulating material P1, P2 Wire pitch W Work

 ──────────────────────────────────────────────────続 き Continuing on 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-62-150663 Hei 2-198759 (JP, A)

Claims (4)

(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 work is pressed to a central portion of the wire row stretched between the rollers except for both ends in the roller axial direction, and the work is cut at the central portion in the roller axial direction of the wire row. Characteristic method of cutting work with wire saw. 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. A cutting device for cutting, wherein a pitch of both ends in a roller axis direction of a wire row stretched between the rollers is set smaller than that of a central portion in a roller axis direction. 3. 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 a cutting device for cutting, a heat insulating material is interposed between journal portions at both ends of the roller, wherein a cutting material is cut. 4. The apparatus according to claim 3, wherein a plurality of grooves are formed concentrically on both end surfaces of the heat insulating material.