JP3656317B2 - Work cutting method and apparatus using wire saw - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement in technology for cutting, for example, a semiconductor silicon ingot into a wafer.
[0002]
[Prior art]
Conventionally, for example, in a workpiece cutting method in which a wafer is cut from a semiconductor silicon ingot, the ingot is pressed against a plurality of thin steel wire wires that move simultaneously at a constant width interval in the longitudinal direction between a pair of rollers, and the pressure contact portion is fine There is known a cutting method such as a wire saw in which a plurality of wafers are simultaneously cut while supplying an abrasive slurry in which various abrasive grains are suspended with an oily or water-soluble coolant. And since this method can cut out many wafers at the same time, it is frequently used in place of a conventional inner peripheral edge slicer or the like.
[0003]
At this time, as a method of moving the wire, a method of cutting by moving the wire at a constant linear velocity from the wire sending portion to the wire receiving portion (one-way feeding cutting of the wire), and keeping the wire linear velocity constant There is a method of cutting by reversing the wire moving direction at a predetermined timing (wire reciprocating cutting). In the latter case, for example, when the wire linear velocity is 500 m / min, the wire moves 36 seconds in the forward direction. After moving, it is moved in the reverse direction for 24 seconds, and this is repeated to move in the forward direction at a speed of substantially 100 m / min (500 m / min × (36-24) / (36 + 24)). The actual feed speed is called the new line supply speed, and is generally kept constant.
Incidentally, in the former one-way cutting of the wire as in the former, the wire speed is the same as the new wire supply speed. However, this method consumes a lot of new wire and increases the cost. A cutting method is common.
[0004]
[Problems to be solved by the invention]
However, when cutting by the conventional method, there is a problem that the cutting surface changes in a taper shape along the cutting direction, and the thickness of the cut wafer changes along the cutting direction.
And the tendency that the thickness of this wafer is different is particularly remarkable when it is cut with a wire saw compared to when it is cut with a conventional inner blade slicer or the like, for example, it reaches 10 μm or more with one wafer, There were problems such as a large lapping allowance in the subsequent process.
[0005]
As a factor for changing the thickness of the wafer in this way, a change in the wear amount of the wire itself was considered. That is, the wire itself is also worn by the action of the abrasive grains, and the amount of wear of this wire affects the cutting width d as shown in FIG. 9, and the cutting surface or thickness changes in a taper shape depending on the width of the cutting width d. It may be that. In general, if the wire wear amount is large and the wire diameter is thin, the cutting width d tends to be narrowed and the wafer thickness tends to be thick. If the wire wear amount is small, the cutting width d is widened and the wafer is widened. It seems that the thickness of will tend to be thin.
[0006]
Therefore, it is considered that such a change in the amount of wear of the wire is greatly influenced by a cutting load (work cutting length × work processing feed speed) applied to the wire, so that the cutting load applied to the wire is kept constant. For example, if the workpiece feed rate is controlled to keep the cutting load constant, it is considered that the amount of wear of the wire becomes constant. Therefore, for example, if the processing is performed while adjusting the processing feed rate so as to make the cutting load constant, the thickness difference is 8 even if the taper sudden change portion at the cutting start portion and the end portion is removed as shown in the typical example of FIG. It was cut out with a taper shape reaching 10 μm, and the taper shape could not be improved. And this taper shape was considered to be the influence by the abrasion of an abrasive grain.
In FIG. 8, the vertical axis represents the thickness of the wafer, and the horizontal axis represents the cutting depth (the left side starts cutting and the right side ends cutting).
[0007]
In view of this, there has been a demand for means for correcting a problem such that the thickness of the workpiece or the cut surface changes in a taper shape along the cutting direction in cutting using a wire saw.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention presses a workpiece against a wire to which a new line is supplied at a predetermined speed from the wire sending side toward the wire receiving side, and supplies the abrasive slurry to the pressure contact portion. In the method of cutting workpieces to be cut, the new wire supply speed is controlled by the amount of wear of the wire and the degree of wear of the abrasive grains. By this control, the amount of wear of the wire is linearly compensated for the amount of wear of the abrasive grains. To change.
In addition, as this device , a wire supply driving means for supplying a new wire at a predetermined speed from the wire sending side to the wire receiving side, a work pressure contacting means for pressing the workpiece against the wire, and supplying abrasive slurry to the pressure contact portion And a control means for controlling the wire supply driving means, and the new line supply speed is controlled by the control means.
[0009]
That is, for example, if the wire wear amount is made constant by making the cutting load constant, as shown in FIG. 8, the thickness of the wafer increases as the processing proceeds, and this means that the cutting width is narrow. It shows that the machining allowance will be reduced. The cause of this was thought to be wear of abrasive grains. That is, generally, while the diameter of the abrasive grains is large, the cutting width is wide (the machining allowance is large), and conversely, if the abrasive grains are crushed and the diameter of the abrasive grains is reduced, the cutting width is reduced (the machining allowance is reduced). ) It is also conceivable that the amount of abrasive slurry that sticks to the wire as it progresses into the cutting groove decreases.
[0010]
Therefore, the cutting speed (machining allowance) is kept constant by controlling the new line supply speed according to the amount of wire wear and the degree of wear of the abrasive grains, which greatly affect the cutting width (machining allowance).
Here, as a method for keeping the new line supply speed constant, for example, in the case of reciprocating cutting of the wire, the ratio of the time in the forward direction and the reverse direction is changed in a constant reciprocating cycle.
[0011]
In the cutting method and cutting apparatus of the present invention, the new line supply speed is
Wire wear amount = k x (cutting load / new line supply speed)
Control based on the relational expression.
Here, cutting load = (work cutting length) × (work processing feed rate), k is a coefficient.
[0012]
The above relational expression has been found by the present inventor. This expression indicates that the wire wear amount increases in proportion to the cutting load and increases in proportion to the new line supply speed. It shows that it decreases.
Therefore, if the cutting load is determined, and the ideal wire wear amount that compensates for the abrasive wear is obtained, the ideal new line supply speed can be obtained from the above relational expression. If the new line supply speed is controlled by approximating this ideal new line supply speed, the cutting width (processing allowance) can be kept constant.
[0013]
In the cutting method and the cutting apparatus of the present invention , as a new line supply method, a reciprocating supply method for supplying a wire while reciprocating at a predetermined timing is adopted.
And the consumption of a wire can be efficiently suppressed by such a reciprocating system.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the accompanying drawings. Here, FIG. 1 is a schematic configuration diagram of a wire saw cutting device, FIG. 2 is an explanatory diagram for explaining an ideal workpiece cutting method, FIG. 3 is an explanatory diagram of an embodiment of the workpiece cutting method, and FIG. 4 is for explaining a cutting load. FIG. 5 is an explanatory diagram for explaining the new line supply speed.
[0015]
The workpiece cutting device using a wire saw of the present invention is configured as a device for cutting a wafer from a silicon ingot manufactured by, for example, a single crystal pulling method, and as shown in FIG. The steel wire 1 is spirally wound around the three rollers 2, 3, 4 at a predetermined pitch and then extended toward the wire receiving portion B, and the lower roller 2 is used as a driving roller. The wire 1 is moved at a predetermined linear velocity, and the two upper rollers 3 and 4 are arranged at the same height, and a processing section 5 is formed between the rollers 3 and 4.
[0016]
That is, a workpiece holder 6 as a workpiece pressing means and an abrasive slurry (a slurry in which fine abrasive grains are suspended in an oily or water-soluble coolant) are supplied to the processing unit 5 and above the processing unit 5. Nozzles 7 and 7 are disposed, and the work holder 6 can hold the ingot W, and can be moved up and down by lifting means (not shown).
A slurry receiver 8 for receiving the abrasive slurry is disposed below the processing unit 5.
[0017]
The drive roller 2 is rotatable by a drive motor 10 as a wire supply drive means, and this drive motor 10 is connected to a control means 11 for controlling according to a preprogrammed method. Then, the control means 11 causes the rotation direction of the drive motor 10 to be reversed at a predetermined timing, and the wire 1 is moved from the wire delivery section A at a substantially predetermined movement speed (new line supply speed) while reciprocating. It is made to supply toward the receiving part B.
[0018]
The new line supply speed is controlled, for example, as shown in FIG. That is, when the wire linear velocity is 500 m / min, for example, as shown in (A), after moving 36 seconds in the forward direction, it is moved 24 seconds in the reverse direction, and by repeating this, it is substantially 100 m / min (500 m / min / min × (36−24) / (36 + 24)) can be moved in the forward direction, and this becomes the new line supply speed.
Next, while keeping the linear velocity constant (500 m / min), for example, as shown in (B), after moving 32.4 seconds in the forward direction, it is moved 27.6 seconds in the reverse direction, and this is repeated. Thus, it can be moved in the forward direction at a speed of substantially 40 m / min (500 m / min × (32.4-27.6) / (32.4 + 27.6)), which becomes the new line supply speed.
Thus, the new line supply speed can be arbitrarily changed by adjusting the reverse rotation timing in the rotation direction. The new wire supply speed is controlled based on an ideal wire wear amount described later.
[0019]
In the processing section 5, the work holder 6 is lowered and pressed against the wire 1 moving the ingot W, and cutting is performed while supplying abrasive slurry to the pressing section. In this embodiment, FIG. As shown in FIG. 5, the glass backing plates G and G are bonded to the upper and lower surfaces of the ingot W for cutting. Of these glass backing plates G, G, for example, the glass backing plate G on the work holder 6 side (upper side) has a function of holding the cut wafer after cutting so that it does not fall downward. In the example, the function of avoiding a sudden change in the cutting load at the start of cutting and at the end of cutting is also performed. This cutting load will be described with reference to FIG.
[0020]
The cutting load is a load applied to the wire 1 when the ingot W is cut by the wire 1. When cutting the ingot W having a circular cross section, the cutting chord length as shown in FIG. It is a multiplier with a machining feed rate (ingot feed rate) as shown in FIG. In this embodiment, the cutting load is made constant as shown in (C) by changing the machining feed rate (ingot feed rate) in (B). In some cases, the machining feed rate cannot be made infinite, so the cutting load at the start of cutting and at the end of cutting cannot be made constant, and a sudden change in the cutting load is inevitable.
[0021]
Therefore, in the case of the present plan, in order to avoid a sudden change in the cutting load at the start and end of cutting as described above, the glass backing plates G and G are bonded up and down as described above, and the glass backing plates G and G are cut together. Like to do. Incidentally, the upper glass backing plate G holds the cut wafer, so that the cutting is stopped in a state where only a part of the lower surface is cut.
[0022]
By the way, the present inventor has found that the relationship of wire wear amount = k × (cutting load / new line supply speed) is established among the cutting load, the new line supply speed, and the wire wear amount as described above. Here, k is a coefficient.
That is, as the cutting load increases, the amount of wire wear increases in proportion to it, and as the new wire feed rate increases, the amount of wire wear decreases in inverse proportion.
[0023]
At this time, the cutting width d (FIG. 9) varies depending on the wire wear amount. For example, when the wire wear amount is large, the diameter of the wire 1 is narrowed and the cut width d is narrowed. Since the cutting width d increases until the diameter of the wire is thick, it is preferable to cut without causing a change in the amount of wire wear. However, if the wire wear amount is kept constant, a certain taper is generated in the wafer thickness as shown in FIG. 8 depending on the amount of wear of the abrasive grains. Therefore, it is necessary to compensate for the depleted portion of the abrasive grains.
[0024]
Therefore, in this proposal, as shown in FIG. 2 (C), a concept of a theoretical ideal amount of wire wear was introduced. This ideal amount of wire wear is a straight line with a downward slope so as to reduce the amount of wire wear according to the progress of the cutting depth of the horizontal axis in order to compensate for the amount of abrasive grain wear. is there. Incidentally, when the wire wear amount is only made constant without considering the depletion amount of the abrasive grains, the straight line of the wire wear amount becomes horizontal.
[0025]
Further, the cutting load in FIG. 2A is maintained substantially constant by adjusting the workpiece machining feed rate as shown in FIG.
Therefore, if the cutting load of FIG. 2 (A) and the ideal wire wear amount of (C) are applied to the above-described calculation formula of wire wear amount = k × (cutting load / new line feed rate), An ideal new line supply speed as shown in (B) is required.
[0026]
Therefore, FIG. 3 is an embodiment approximated to the ideal state of FIG. 2, and for the cutting load of FIG. 3 (A), FIG. 2 (A) is faithfully reproduced as is, and FIG. As for the new line supply speed, the ideal new line supply speed in FIG. 2B is approximated by dividing into four sections. The theoretical wire wear amount in FIG. 3C is obtained from the above calculation formula from FIGS. 3A and 3B.
[0027]
That is, in this proposal, the machining is performed while controlling the drive motor 10 by the control means 11 so as to change the new line supply speed in four stages while adjusting the machining feed rate so as to keep the cutting load constant. The wafer actually cut at this time was in a state where there was almost no influence of the taper on the cutting direction, as shown in FIG.
[0028]
Further, when the taper degree at the time of cutting is compared with the conventional case and the case of the inner peripheral blade slicer, for example, as shown in FIG. 7, the taper degree is improved to a level slightly inferior to the inner peripheral blade slicer. confirmed.
[0029]
The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
[0030]
For example, in this embodiment, the ideal new line supply speed is approximated and switched by dividing into four sections. However, in order to make it closer to the ideal, continuously or at least about 8 to 10 steps or more. It is desirable to switch.
[0031]
【The invention's effect】
The present invention as described above, controls the new linear feed speed of the wire, due to so as to linearly vary the amount of wear of the wire in consideration of the depletion amount of the abrasive grains, the work of cutting width (machining allowance) For example, the thickness can be made uniform on a wafer or the like.
For this reason, for example, there is an effect that the chamfering width in the subsequent process can be made uniform and the lapping allowance can be reduced.
Further , by controlling the new line supply speed based on a predetermined relational expression , the new line supply speed can be controlled based on the ideal wire wear amount.
Furthermore , if the wire reciprocating system is adopted as the new line supply system, the wire consumption can be efficiently suppressed.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a cutting apparatus using a wire saw.
FIG. 2 is an explanatory diagram for explaining an ideal workpiece cutting method, in which (A) is a cutting load, (B) is an ideal new wire feed rate, and (C) is an (theoretical) ideal wire. It is the amount of wear.
FIG. 3 is an explanatory diagram of an embodiment of a workpiece cutting method, where (A) is a cutting load, (B) is a new wire supply speed, (C) is a (theoretical) wire wear amount, and (D) is an actual one. The wafer taper.
4A and 4B are explanatory diagrams for explaining a cutting load, in which FIG. 4A is a cutting string length, FIG. 4B is an ingot feed speed, and FIG. 4C is a cutting load.
FIG. 5 is an explanatory diagram for explaining a new line supply speed, (A) when the new line supply speed is 100 m / min, and (B) when the new line supply speed is 40 m / min. It is a control method.
FIG. 6 is an explanatory diagram of a state where a glass backing plate is bonded to an ingot.
FIG. 7 is a comparative diagram for comparing the effects of the present scheme.
FIG. 8 is an explanatory diagram showing a typical example of the influence of abrasive grain wear when cutting with a constant cutting load.
FIG. 9 is an explanatory diagram of a cutting width.
[Explanation of symbols]
1 ... wire, 2 ... drive roller,
3 ... Roller, 4 ... Roller,
5 ... Machining part, 6 ... Work holder,
7 ... nozzle, 8 ... slurry receiver,
10 ... Drive motor, 11 ... Control means,
A ... Wire feeding part, B ... Wire receiving part,
d: Cutting width, G: Glass plate,
W ... Ingot.

Claims (4)

In a workpiece cutting method in which a workpiece is pressed against a wire to which a new line is supplied at a predetermined speed from the wire sending side to the wire receiving side, and the workpiece is cut while supplying abrasive slurry to the pressure contact portion. , While adjusting the machining feed rate to keep the cutting load ((work cutting length) x (work feed speed)) constant, the new wire supply speed of the wire will be processed when the cutting load is kept constant A method of cutting a workpiece with a wire saw, wherein the workpiece linearly changes so as to compensate for an increase in the thickness of the wafer along with the wire saw. 2. The work cutting method using a wire saw according to claim 1 , wherein the supply of the new line is a reciprocating supply system that supplies the wire while reciprocating at a predetermined timing. Wire supply driving means for supplying a new line at a predetermined speed from the wire sending side toward the wire receiving side, work pressure contacting means for pressing the workpiece against the wire, and slurry supplying means for supplying abrasive slurry to the pressure contact portion A workpiece cutting apparatus comprising a control means for controlling the wire supply driving means, wherein the control means compensates for an increase in wafer thickness as the processing proceeds when the cutting load is constant. A workpiece cutting device using a wire saw that linearly controls a new line supply speed. 4. The workpiece cutting apparatus using a wire saw according to claim 3 , wherein the supply of the new line by the wire supply driving means is a reciprocating supply system that supplies the wire while reversing the wire feeding direction at a predetermined timing. Work cutting device with wire saw.

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