JPH05220732A - Multi-channel roller for multi-wire saw - Google Patents

Abstract

PURPOSE:To control the variation of wire channel positions due to the temperature variation generated during cutting and ensure the flatness of a wafer by using a material of small linear expansion coefficient for a part o thermal expansion in the axial direction and varying the wire channel positions. CONSTITUTION:Cylindrical holder 13, rotating shafts 16 and shafts 17 of multi- channel rollers 1, 2 and 3 constituted of sleeves with ring channels on the outer peripheries formed at the given interval, cylindrical holders 13 fitted over the sleeves, rotating shafts 16 supporting the cylinders 13 and shafts 17 fixing the rotating shafts 16 and the holders 13 in the axial direction are manufactured by the Invar or Super-Invar respectively. The movement of the sleeves with channels in the axial direction is protected by preventing the thermal deformation generated by the temperature rise, and as a result, twisting and bending of the cut channels are eliminated to ensure the flatness of a product wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-wire saw multi-groove roller for cutting brittle materials such as semiconductor materials, magnetic materials and ceramics into a large number of thin wafers with wires.

[0002]

2. Description of the Related Art A multi-wire saw used to cut an ingot of a brittle material such as a semiconductor material into a wafer is composed of a wire row and a cut object (hereinafter referred to as a "workpiece") which are multiply threaded at a predetermined pitch. It is a device that cuts while supplying a grinding liquid containing abrasive grains in between. FIG. 1 exemplifies a cutting part of a general multi-wire saw, in which one wire is provided in a large number of grooves engraved on the outer peripheral surfaces of three multi-groove rollers 1, 2 and 3 which are rotatably held. 4 is wound to form a wire row 5 having a predetermined pitch, the wire row is run, and the abrasive liquid 3 supplied to the work 6 from the nozzle 7
0 is interposed between the wire row 5 and the work 6, and the work push-up base 10 is gradually pushed up and cut by the grinding action. The work 6 is adhered to a dummy plate 8 made of carbon, ceramics, glass or the like, and the dummy plate 8 is fixed to the work push-up base 10 by a method such as adhesion to a metal base 9 which is detachably fixed by screws 11. ing.

FIG. 2 shows the state of the work after cutting is completed.
Figure (A) is a perspective view, and Figure (B) is a partially enlarged side view.
The cutting by the wire 4 is performed halfway through the dummy plate 8, and the work 6 is cut into a large number of product wafers 6-1 and extra length portions 6-2 at both ends. The wafer 6-1 is required to have thickness accuracy and flatness of the cut surface, and in particular, flatness which is not expected to be greatly improved in the subsequent polishing step needs to have a high level at the cutting stage. For example, a silicon wafer, which is a material for an IC chip, is required to have a flatness with a height difference of 20 μm or less, and its level tends to become severe with the development of the semiconductor industry.

Here, the flatness of the wafer cut by the wire saw will be described. FIG. 3 shows the product wafer 6-1.
It is a perspective view showing one sheet taken out. Y in the wire traveling direction
The -Y 'line is almost flat at any position, whereas "waviness" occurs in the XX' line in the wire cutting direction. This waviness is caused by the temporal movement of the position of the wire stretched between the groove rollers 2 and 3 in the space. The greatest cause of this movement is that the groove positions of the groove rollers 2 and 3 that determine the spatial position of the wire move in the axial direction due to thermal deformation of the groove rollers 2 and 3 that occurs during the cutting process. The wire traveling method of the wire saw includes a reciprocal method in which the wire row between the groove rollers 2 and 3 is reciprocated and gradually wound up on a reel, and a unidirectional method in which the wire travels in only one direction. The one-way type, which can increase the running speed of the rows and the cutting speed into the work to improve the cutting efficiency, has a larger thermal deformation of the groove rollers.

FIGS. 4 and 5 show typical examples of the structure of the groove roller. FIG. 4 shows a type in which the entire groove roller rotates,
FIG. 5 shows a type in which the groove roller rotates around the central axis. In case of the type that the whole groove roller rotates,
As shown in FIG. 4 (B) by enlarging the dotted circle in FIG. 4 (A),
A grooved sleeve 12 in which a ring-shaped groove 11 having a V-shaped cross section for accommodating the wire 4 is engraved at a predetermined pitch is a cylindrical holder 1
3, one end surface abuts on the holder flange 13-1, and the other end surface is tightened by a nut 14 screwed into the holder screw portion 13-2. The cylindrical holder 13 is fixed to a rotary shaft 16 via a key 15, and is fixed to a core rod 17 screwed to the rotary shaft 16 with a nut 19 via a washer 18. The rotary shaft 16 is rotatably supported by the main body frame 18 via a bearing 22, and the bearing 22 is composed of a flange 19 fixed to the main body frame 18 by a bolt 21 and a nut 20 screwed to the rotary shaft 16. It is fixed in the axial direction.

In the groove roller of the type shown in FIG. 5, a cylindrical holder 13 to which a grooved sleeve 12 is fitted is rotatably fitted to a fixed shaft 24 via a bearing 32. It is fixed to the body frame 18 with bolts 26 via the flange portion 24-1. On the other hand, the bearing 32 is axially fixed by the nut 20 screwed to the other end of the fixed shaft 24 and the inner nut 25 screwed to the inner surface of the end of the tubular holder 13, and the grooved sleeve 12 is It is tightened by a nut 14 screwed to the outer surface of the end of the cylindrical holder 13. 28 is a spacer.

[0007]

However, the groove roller having the structure shown in FIGS. 4 and 5 has the following problems. In the case of the groove roller having the structure shown in FIG.
First, the temperature of the rotating shaft 16 is raised by the heat generated in the bearing 22 that supports the rotating shaft 16. When the rotating shaft 16 thermally expands in the axial direction due to this temperature rise, the tightening force of the nut 20 decreases, and when loosening occurs, the rotating shaft 16 moves in the axial direction. That is, when the entire groove rollers 2 and 3 move in the axial direction, as shown in FIG. 6, a phenomenon occurs in which all the wire cutting grooves 23 of the work 6 undulate in parallel.

Further, the heat passing through the rotary shaft 16 receives the core rod 17.
And transmitted to the cylindrical holder 13, and each expands in the axial direction.
At this time, if the thermal expansion of the core rod 17 is larger than that of the holder 13, the tightening force of the nut 19 is reduced and loosening occurs. As a result, the cylindrical holder 13 is allowed to move in the axial direction, and the undulation of the cut groove as shown in FIG. 6 occurs. On the contrary, when the thermal expansion of the cylindrical holder 13 is larger than that of the core rod 17, the tensile force acting on the core rod 17 increases and the nut 19
Never slacks. However, due to this pulling force, the core rod 1
7 yields, and when the temperature of the cylindrical holder 13 decreases from that state, the nut 19 is loosened, and the cylindrical holder 13 is allowed to move in the axial direction.

Further, in the case of the grooved roller having the structure shown in FIG. 5, the heat generated in the bearing 32 is transmitted to the fixed shaft 24 and the cylindrical holder 13 and expanded in the axial direction. When the thermal expansion of the fixed shaft 24 is larger than that of the cylindrical holder 13, the nut 20
Is slackened, the cylindrical holder 13 moves in the axial direction, and the undulation of the cut groove as shown in FIG. 6 occurs. On the contrary, when the thermal expansion of the tubular holder 13 is larger than that of the fixed shaft 24, the inner nut 25 is loosened and the tubular holder 13 moves in the axial direction.
The undulation of the cut groove occurs as shown in FIG.

In any of the above states, when the cylindrical holder 13 is thermally expanded in the axial direction, the groove position of the grooved sleeve 12 is affected. First, when the grooved sleeve 12 is made of resin, the coefficient of linear expansion is much larger than that of the cylindrical holder 13, so that the holder 14 extends in accordance with the thermal expansion of the holder 13, and the nut 14 does not loosen. However, the position of the groove 11 changes due to the expansion of the grooved sleeve 12. Since the movement of the groove 11 of the grooved sleeve 12 is larger in the vicinity of the nut 14 at the end portion, the bending of the wire cutting groove 23 becomes larger as it is closer to the nut 14 as shown in FIG. 7. Next, when the thermal expansion of the grooved sleeve 12 is smaller than that of the cylindrical holder 13, the nut 14 is loosened, and when the grooved sleeve 12 moves in the axial direction in this state, a cutting groove similar to that of FIG. 6 is formed. Swell occurs.

As described above, in order to improve the flatness of the cut wafer, it is necessary to prevent thermal expansion of the groove roller. However, in addition to bearings, the heat source is the heat transmitted from the wire saw body frame, the heat transmitted from the wire whose temperature has risen due to sliding with the workpiece through the grooved sleeve, the heat transmitted from the abrasive liquid, and the surroundings of the groove roller. There is heat, etc. transmitted from the atmosphere, and it is almost impossible to completely block them.

In view of such circumstances, the present invention can suppress thermal expansion as much as possible by changing the material of the groove roller as a measure for preventing the influence of heat transmitted to the groove roller from appearing in the grooved sleeve. It proposes a multi-groove roller.

[0013]

DISCLOSURE OF THE INVENTION According to the present invention, among parts constituting a groove roller, a material having a small coefficient of linear expansion is used for a part which thermally expands in the axial direction to change the wire groove position. The flatness of the wafer is ensured by suppressing the change in the wire groove position due to the temperature change that occurs in the inside, and the gist thereof is a sleeve in which ring-shaped grooves are formed on the outer periphery at a predetermined pitch, and the sleeve. A cylindrical holder for externally fitting the holder, a rotary shaft for supporting the holder, and a core rod for fixing the rotary shaft and the holder in the axial direction. A sleeve having a ring-shaped groove formed at a predetermined pitch on the outer periphery, a cylindrical holder for externally fitting the sleeve, and a fixing member for rotatably supporting the holder. Axis The cylindrical holder and the fixed shaft are made of a material having a small linear expansion coefficient, and the material having a small linear expansion coefficient contains nickel 36 ± 1%, and the balance is iron and unavoidable. The present invention is characterized by using an alloy consisting of toxic impurities, or an alloy containing 32 ± 1% of nickel and 5 ± 1% of cobalt, and the balance consisting of iron and unavoidable impurities.

[0014]

A sleeve having ring-shaped grooves formed on the outer periphery at a predetermined pitch, a cylindrical holder for externally fitting the sleeve, a rotary shaft for supporting the holder, and the rotary shaft and the holder fixed in the axial direction. In the case of a grooved roller configured with a core rod, the thermal expansion of the cylindrical holder, the rotating shaft and the core rod has a great influence on the cutting accuracy, and a ring-shaped groove is formed on the outer periphery at a predetermined pitch. In the case of a groove roller including a sleeve, a cylindrical holder that fits the sleeve over the sleeve, and a fixed shaft that rotatably supports the holder, thermal expansion of the cylindrical holder and the fixed shaft greatly affects cutting accuracy. Therefore, in the present invention, these constituent members are made of a material having a small linear expansion coefficient.

An alloy containing 36 ± 1% of nickel used as a material having a small linear expansion coefficient and the balance of iron and unavoidable impurities is generally Invar (also called Amber).
Also called nickel 32 ± 1%, cobalt 5 ± 1%
An alloy that contains, with the balance being iron and unavoidable impurities, is called superinvar (super invariant steel),
The linear expansion coefficient of Invar is 2.0 × 10 ⁻⁶ / ° C. (30 to 1
00 ° C) or less, the coefficient of linear expansion of Super Invar is 1.3.
It is not more than × 10 ⁻⁶ / ° C. (30 to 100 ° C.).

A sleeve having ring-shaped grooves formed on the outer periphery thereof at a predetermined pitch, and a cylindrical holder for externally fitting the sleeve.
A cylindrical holder of a groove roller composed of a rotary shaft that supports the holder and a core rod that fixes the holder in the axial direction, the rotary shaft and the core rod, and rotatably supports the cylindrical holder. When the cylindrical holder of the groove roller and the fixed shaft, which are composed of the fixed shaft and the fixed shaft, are made of Invar or Super Invar, respectively, the thermal deformation due to the temperature rise during cutting is prevented, so that the axial direction of the grooved sleeve is reduced. Is prevented, and as a result, the waviness and bending of the cut groove are eliminated, and the flatness of the product wafer is secured.

[0017]

EXAMPLE For example, in the case of the grooved roller having the structure shown in FIG. 5, it was found that the temperature of the fixed shaft 24 changes as shown in FIG. Here, the temperature T rapidly rises with the start of cutting,
The temperature reaches saturation after a certain time t _s . The temperature rise ΔT varied depending on the load acting on the groove roller, that is, the material of the work, the number of wire rows, the cutting speed, and the wire speed, and was in the range of 10 to 40 ° C. in the experiment. It is estimated that the cylindrical holder 13 also has an equivalent temperature rise. As a matter of course, it is considered that the longer the groove rollers 2 and 3, the larger the thermal expansion, and that the thermal expansion is substantially proportional to the length 1 of the grooved sleeve 12.

The cylindrical holder 13 has a linear expansion coefficient of 11 × 10.
^When manufactured from ^-6 / ° C steel, a 1 ° C increase in temperature increases the length 1 of the grooved sleeve 12 by 1.1 x 10 ^-3 %. For example, in the case of 1 = 300 mm, if the temperature rises by 40 ° C., the length of the grooved sleeve 12 increases by 132 μm.

As described above, the movement of the groove 11 due to the increase in the length of the grooved sleeve 12 is large at the end portion on the side of the nut 14, and the flatness (difference in height of the surface) of the product wafer 6-1 is shown in FIG. To be distributed. In the case of the groove roller having the structure shown in FIG. 5, the increase amount of the length 1 of the grooved sleeve 12 calculated from the temperature rise and the maximum value of the flatness of the product wafer 6-1 are almost equal. That is, in order to set the maximum value of the flatness to, for example, 20 μm or less, it is necessary to suppress the increase amount of 1 to 20 μm or less. For example, in order to suppress the increase of 1 to 20 μm or less for a temperature rise of 40 ° C. at 1 = 300 mm, the linear expansion coefficient of the fixed shaft 24 and the cylindrical holder 13 is 3 × 10 ⁻⁶ / ° C.
It must be made of the following materials. The Invar and Super Invar satisfy this condition, and by using such a material having a small linear expansion coefficient, the increase of 1 can be suppressed to 20 μm or less with respect to the temperature rise of 40 ° C.

Example 1 In the groove roller having the structure shown in FIG. 4, the rotary shaft 16, the core rod 17, and the cylindrical holder 13 contained Ni 32% and Co 5%, and the balance was Fe and inevitable impurities. Made of alloy with coefficient 0.8 × 10 ⁻⁶ / ° C., l = 300 mm
The groove 11 made of ultra-high molecular weight polyethylene is stretched over the groove 11 with a pitch of 2 mm over almost the entire length to form a piano wire having a diameter of 0.2 mm to form a total of 121 wire rows, with an average particle diameter of 28 μm. While applying an abrasive liquid prepared by mixing the above silicon carbide abrasive grains in lapping oil, the wire array was run at a speed of 600 m / min to obtain a cross-sectional dimension of 2
A 40 mm square quartz ingot was raised at a speed of 0.8 m / min to simultaneously cut 120 wafers of 240 mm square and 1.7 mm thick. As a result of measuring the flatness of all the wafers,
The maximum height difference between the cut surfaces was 11 μm. On the other hand, for comparison, the flatness of the wafer obtained by cutting under the same conditions as above was measured using a steel rotating shaft, a core rod, and a cylindrical holder. Has occurred.

[0021] Example 2 in groove rollers having the structure shown in FIG. 5, the fixed shaft 24 and the cylindrical holder 13, containing Ni36%, a linear expansion coefficient of 1.5 × 10 the balance of Fe and unavoidable impurities ^{- 6} /
Made of an alloy of 1 ° C, and a piano wire having a diameter of 0.16 mm is stretched in a groove 11 formed by engraving a groove sleeve 12 made of ultra-high molecular weight polyethylene of l = 100 mm at a pitch of 0.7 mm over almost the entire length, for a total of 101 rows. Forming a wire row and applying a polishing liquid in which silicon carbide abrasive grains having an average particle diameter of 16 μm are mixed with lapping oil to the wire row of 400 m.
The diameter of the single crystal silicon ingot having a diameter of 125 mm was increased to 0.7 m / min and the diameter was increased to 12 mm.
100 wafers of 5 mm square and 0.5 mm thick were simultaneously cut. As a result of measuring the flatness of all the wafers, the height difference between the cut surfaces was 15 μm at the maximum. On the other hand, for comparison, as a result of measuring the flatness of a wafer obtained by cutting under the same conditions as above using a steel fixed shaft and a tubular holder, a maximum difference in height of 70 μm was generated on the cut surface. ..

[0022]

As described above, in the multi-groove roller according to the present invention, the axial deformation of the grooved sleeve is prevented by suppressing the thermal deformation of the constituent members due to the temperature rise during cutting, and the cut groove is formed. As a result of eliminating the waviness and bending, the excellent effect that the flatness of the product wafer can be ensured is exhibited. Further, the improvement of the flatness of the product wafer leads to the improvement of the flatness of the finished product wafer that has undergone the polishing process in the subsequent step as it is, and for example, in the case of a semiconductor chip, a product having a higher cumulative degree can be manufactured. , Has a great effect in the electronics industry.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cutting portion of a general multi-wire saw.

2A and 2B are explanatory views showing a state in which a wire is cut into a dummy material in the above-mentioned multi-wire saw cutting, FIG. 2A is a perspective view, and FIG. 2B is a partially enlarged side view.

FIG. 3 is a perspective view showing a cut product wafer.

FIG. 4 is a structural example of a groove roller of a multi-wire saw,
(A) is a vertical sectional side view of the entire groove roller, and (B) is a diagram (A).
It is an enlarged view of a dotted circle part of.

FIG. 5 is a vertical cross-sectional side view showing a structural example of another groove roller of the multi-wire saw.

FIG. 6 is a cross-sectional view showing an example of a trajectory of a wire being cut by the same multi-wire saw.

FIG. 7 is a cross-sectional view showing another example of the trajectory of the wire being cut by the multi-wire saw.

FIG. 8 is an explanatory diagram showing an example of a change with time in temperature of a rotary shaft of the grooved roller during cutting.

FIG. 9 is an explanatory diagram of a groove roller axial direction distribution of flatness of a product wafer.

[Explanation of symbols]

 1, 2, 3 Multi-groove roller 4 Wire 5 Wire row 6 Work 7 Nozzle 8 Dummy plate 9 Base 10 Work push-up base 11 Groove 12 Groove sleeve 13 Cylindrical holder 16 Rotating shaft 17 Core rod 18 Body frame 24 Fixed shaft

Claims (3)

[Claims] 1. A sleeve in which ring-shaped grooves are formed on the outer periphery at a predetermined pitch, a cylindrical holder for externally fitting the sleeve, a rotary shaft for supporting the holder, an axial direction of the rotary shaft and the holder. A multi-groove roller for a multi-wire saw, characterized in that the cylindrical holder, the rotating shaft, and the core rod are each made of a material having a small linear expansion coefficient. 2. A tubular body comprising a sleeve having ring-shaped grooves formed on the outer periphery thereof at a predetermined pitch, a tubular holder for externally fitting the sleeve, and a fixed shaft for rotatably supporting the holder. A multi-groove roller for a multi-wire saw, wherein the holder and the fixed shaft are made of a material having a small linear expansion coefficient. 3. An alloy containing 36 ± 1% nickel with the balance being iron and unavoidable impurities, or nickel 32 ± 1%, cobalt 5 as a material having a small linear expansion coefficient.
3. A multi-groove roller for a multi-wire saw according to claim 1, wherein an alloy containing ± 1% and the balance iron and unavoidable impurities is used.