JPH09262826A - Method and device for cutting work with wire saw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut wafers in the constant thickness with a wire saw for cutting the wafers from, for instance, a semiconductor silicone ingot. SOLUTION: When a wire is moved substantially at the given speed (new wire feed speed) from a wire delivery section A toward a wire receiving section B while the wire 1 is moved reciprocatingly by a driving motor 10 and an ingot W is brought into contact with the wire 1, and the wire is cut while abrasive grain slurry is fed to a contact section, the new wire feed speed is controlled by a control means 11. In the constitution, the wear amount of the wire 1 is reduced linearly following the progress of processing, and the natural decrease amount of abrasive grains is compensated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a technique for cutting a semiconductor silicon ingot into wafers.

[0002]

2. Description of the Related Art Conventionally, for example, in a work cutting method for cutting a wafer from a semiconductor silicon ingot,
An ingot is pressed against a plurality of thin steel wire wires that simultaneously move at a constant width in the longitudinal direction between a pair of rollers, and an abrasive slurry in which fine abrasive particles are suspended in an oil-based or water-soluble coolant at this contact portion. A cutting method such as a wire saw is known in which a plurality of wafers are simultaneously cut while being supplied.
Since this method can cut out a large number of wafers at the same time, it has been widely used instead of the conventional inner peripheral blade slicer or the like.

At this time, as a method of moving the wire, a method of moving the wire at a constant linear velocity from the wire feeding portion to the wire receiving portion to cut it (one-way feed cutting of the wire) and a linear velocity of the wire are used. There is a method of cutting while reversing the moving direction of the wire while keeping it constant (reciprocating cutting of the wire). In the latter case,
For example, when the wire linear velocity is set to 500 m / min, the wire is moved 36 seconds in the forward direction and then 24 seconds in the reverse direction.
By repeating this, the actual 100m / min (500m / mi
In a system in which the material is moved in the forward direction at a speed of n × (36−24) / (36 + 24)), this actual feed speed is called a new line supply speed, and generally this is kept constant. By the way, in the case of the one-way feed cutting of the former wire, the linear velocity of the wire becomes the new wire supply speed as it is, but in this method, the consumption of the new wire is extremely high and the cost is high. The cutting method is generally used.

[0004]

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 more remarkable especially when it is cut with a wire saw than when it is cut with a conventional inner peripheral blade slicer or the like, for example, since it reaches 10 μm or more for one wafer, There was a problem such as a large lapping allowance in the subsequent process.

As a factor causing such a change in the thickness of the wafer, a change in the amount of wear of the wire itself was considered. That is, the wire itself also wears due to the action of the abrasive grains, and the wear amount 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. That is to say. Generally, if the wire wear amount is large and the wire diameter is thin, the cutting width d tends to be narrow and the wafer thickness tends to be thick. If the wire wear amount is small, the cutting width d is widened. It seems that the thickness of is likely to be thin.

Therefore, it is considered that such a change in the wear amount of the wire is greatly influenced by the cutting load (work cutting length × work machining feed rate) applied to the wire. Therefore, the cutting load applied to the wire is kept constant. It is considered that the wear amount of the wire becomes constant if the cutting load is kept constant and the work is performed so as to keep the work, for example. Therefore, for example, when machining is performed while adjusting the machining feed rate so as to keep the cutting load constant, for example, as shown in the typical example of FIG. It was cut out in a tapered shape reaching up to -10 μm, and the tapered shape could not be improved. It was considered that this taper shape might be due to the wear of the abrasive grains. In FIG. 8, the vertical axis represents the thickness of the wafer, and the horizontal axis represents the cutting depth (the left side is the cutting start and the right side is the cutting end).

Therefore, there has been a demand for a means for correcting the problem that the thickness of the work or the cut surface changes in a taper shape along the cutting direction in the cutting using the wire saw.

[0008]

In order to solve the above-mentioned problems, the present invention according to claim 1 presses a work onto a wire to which a new wire is supplied at a predetermined speed from the wire sending side to the wire receiving side. In the work cutting method in which the work is cut while supplying the abrasive slurry to the press contact portion, the new wire supply speed of the wire is controlled by the wear amount of the wire and the degree of wear of the abrasive, and the wire is controlled by this control. The amount of wear was adjusted so as to change linearly while compensating for the wear of the abrasive grains. As this device, as in claim 4,
Wire supply driving means for supplying a new wire from the wire sending side to the wire receiving side at a predetermined speed, a work pressing means for pressing a work against the wire, and a slurry supplying means for supplying abrasive slurry to the press contact portion. A control means for controlling the wire supply driving means is provided, and the new wire supply speed is controlled by this control means.

That is, if the amount of wire wear is made constant by making the cutting load constant, for example, the thickness of the wafer increases as the processing progresses, as shown in FIG. It shows that the width becomes narrower (the machining allowance is smaller). The cause of this was considered to be abrasion 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). Conversely, when the abrasive grains are crushed and the diameter of the abrasive grains is small, the cutting width is narrowed (the machining allowance is reduced. ) Thought to be. In addition, it is conceivable that the amount of abrasive grain slurry that adheres to the wire viscously decreases in the cutting groove as the machining progresses.

Therefore, the new wire feed rate is controlled by the amount of wear of the wire and the degree of wear of the abrasive grains, which greatly affects the cutting width (working allowance), to keep the cutting width (working allowance) constant. Here, in the method of keeping the new wire supply rate constant, for example, in the case of reciprocating cutting of the wire, the ratio of time in the forward direction and the time in the reverse direction is changed within a constant reciprocating cycle.

In the cutting method according to claim 2 and the cutting device according to claim 5, the new wire supply speed is controlled based on the relational expression of wire wear amount = k × (cutting load / new wire supply speed). I chose Here, cutting load = (work cutting length) × (work processing feed rate), and k is a coefficient.

The above relational expression was found by the present inventor. This expression shows that the wire wear amount increases in proportion to the cutting load, and increases as the new wire feeding speed increases. It shows that it decreases in inverse proportion. Therefore, if the cutting load is determined and the ideal amount of wire wear that compensates for the wear of the abrasive grains is found, the ideal new wire feed rate can be found from the above relational expression. If the new line supply speed is controlled so as to approximate the ideal new line supply speed, the cutting width (machining allowance) can be kept constant.

Further, in the cutting method according to claim 3 and the cutting device according to claim 6, the reciprocating supply system for supplying the wire while reciprocating the wire at a predetermined timing is used as the supply system for the new wire. Then, the wire consumption can be efficiently suppressed by such a reciprocating method.

[0014]

Embodiments of the present invention will be described with reference to the accompanying drawings. Here, FIG. 1 is a schematic diagram of the structure of a cutting device using a wire saw, FIG. 2 is an explanatory view for explaining an ideal work cutting method, FIG. 3 is an explanatory view for an embodiment of the work cutting method, and FIG. 4 is for explaining cutting load. FIG. 5 is an explanatory diagram for explaining the new line supply speed.

The work cutting device with 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 extends from a wire feeding portion A as shown in FIG. One steel wire 1 is spirally wound around the three rollers 2, 3 and 4 at a predetermined pitch, and then is extended toward the wire receiving portion B. As the drive roller, the wire 1 is moved at a predetermined linear velocity, and the upper two rollers 3 and 4 are arranged at the same height, and the space between the rollers 3 and 4 is a processing section 5.

That is, above the processing part 5, a work holder 6 as a work pressure contact means, and an abrasive grain slurry (slurry in which fine abrasive grains are suspended with an oily or water-soluble coolant) toward the processing part 5. ) Is provided, the work holder 6 can hold the ingot W, and can be moved up and down by an elevating means (not shown). A slurry receiver 8 for receiving the abrasive slurry is disposed below the processing unit 5.

The drive roller 2 is rotatable by a drive motor 10 as a wire supply drive means, and the drive motor 10 is connected to a control means 11 for controlling according to a preprogrammed method. . Then, by the control means 11, the drive motor 1
In the case of 0, the rotation direction is reversed at a predetermined timing, and the wire 1 is reciprocated and is fed from the wire sending portion A to the wire receiving portion B at a substantially predetermined moving speed (new wire feeding speed). I am trying.

The new line supply speed is controlled as shown in FIG. 5, for example. That is, the wire linear velocity is 500 m / mi
When n, for example, 3 in the forward direction as shown in (A)
After moving for 6 seconds, move for 24 seconds in the opposite direction, and repeat this to get 100m / min (500m / min x
It can be moved in the forward direction at a speed of (36-24) / (36 + 24)), which is the new line supply speed. Next, while keeping the linear velocity constant (500 m / min), for example, as shown in (B), after moving in the forward direction for 32.4 seconds, moving in the reverse direction for 27.6 seconds, and repeating this , 40m / min (500m / min x (32.4-2
It can be moved in the forward direction at a speed of (7.6) / (32.4 + 27.6)), which is the new line supply speed. By adjusting the reverse rotation timing of the rotation direction in this way,
The new line supply speed can be changed arbitrarily. The new wire supply speed is controlled based on an ideal wire wear amount described later.

Further, in the processing section 5, the work holder 6 is lowered to press the ingot W against the moving wire 1, and cutting is performed while supplying the abrasive grain slurry to the pressing section. As shown in FIG. 6, the glass contact plates G, G are adhered to the upper surface and the lower surface of the ingot W for cutting. Among the glass contact plates G, G, for example, the glass contact plate G on the side of the work holder 6 (upper) also has a function of holding the cut wafer after cutting so as not to drop downward. In the example, the function of avoiding a sharp change in the cutting load at the start of cutting and at the end of cutting is also performed. Therefore, this cutting load will be described with reference to FIG.

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, a cutting chord length as shown in FIG. It is a multiplier with the machining feed rate (ingot feed rate) as shown in B) and is represented as shown in FIG. In the present embodiment, the cutting feed rate (ingot feed rate) is changed in (B) so that the cutting load becomes constant as shown in (C), but at the start of cutting and the end of cutting. Since it is impossible to make the machining feed rate infinite at times, it is not possible to make the cutting load constant at the start of cutting and at the end of cutting, and sudden changes in cutting load cannot be avoided.

Therefore, in the case of the present invention, in order to avoid the abrupt change of the cutting load at the start and end of cutting as described above, the glass contact plates G, G are bonded to each other as described above, and the glass contact plates G, G are adhered to each other. I try to cut it with G. Incidentally, in order to hold the cut wafer, the upper glass backing plate G stops cutting with only a part of the lower surface cut.

By the way, the inventor of the present invention has found that the relationship of wire wear amount = k × (cutting load / new wire supply speed) is established between the above cutting load, new wire supply speed and wire wear amount. I found it. Here, k is a coefficient. That is, when the cutting load increases, the wire wear amount increases in proportion to it, and when the new wire supply speed increases, the wire wear amount decreases in inverse proportion to it.

At this time, the cutting width d (FIG. 9) changes depending on the amount of wire wear. For example, when the amount of wire wear is large, the diameter of the wire 1 becomes thin and the cutting width d becomes narrow, and when the amount of wire wear is small. Since the cutting width d is widened until the diameter of the wire 1 is large, it is preferable to cut without changing the amount of wear of the wire. However, if the amount of wire wear is kept constant, the amount of wear of the abrasive grains causes a constant taper in the thickness of the wafer, as shown in FIG. 8. Therefore, it is necessary to compensate for the worn portion of the abrasive grains.

Therefore, in the present invention, as shown in FIG. 2 (C), the concept of theoretically ideal amount of wire wear is introduced. This ideal wire wear amount is obtained by giving a downward slope to the straight line so as to reduce the wire wear amount according to the progress of the cutting depth on the horizontal axis in order to compensate for the wear loss of the abrasive grains. is there. Incidentally, when the amount of wire wear is simply made constant without considering the amount of wear of the abrasive grains, this straight line of the amount of wire wear is horizontal.

Further, the cutting load of FIG. 2 (A) is maintained substantially constant by adjusting the work 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 wire supply speed), An ideal new line supply rate as shown in (B) is required.

Therefore, FIG. 3 shows an embodiment approximated to the ideal state of FIG. 2, and the cutting load of FIG. 3A is faithfully reproduced as it is in FIG. Regarding the new line supply speed in (B), the ideal new line supply speed in FIG. 2 (B) is approximated by dividing into four sections. And FIG.
The theoretical amount of wire wear in (C) is calculated from the above formula from FIGS. 3 (A) and 3 (B).

That is, according to the present invention, the machining feed speed is adjusted so as to keep the cutting load constant, and machining is performed while controlling the drive motor 10 by the control means 11 so as to change the new wire feed speed in four stages. The wafer actually cut out at this time was in a state where there was almost no influence of the taper on the cutting direction, as shown in FIG.

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, it is as shown in FIG. 7, which is improved to a degree slightly inferior to the inner peripheral blade slicer. It was confirmed that

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and has substantially the same configuration as the technical idea described in the scope of the claims of the present invention. It is included in the technical scope of the invention.

For example, in the present embodiment, the ideal new line supply speed is approximated in four sections and switched, but in order to make it more ideal, it is continuous or at least 8 to 10 steps. It is desirable to switch to a higher level.

[0031]

As described above, according to the present invention, as in claims 1 and 4, the new wire feeding speed of the wire is controlled to linearly determine the wear amount of the wire in consideration of the wear of the abrasive grains. The cutting width (working allowance) of the work can be made constant, and the thickness can be made uniform in, for example, a wafer. Therefore, for example, the chamfering width in the subsequent process can be made uniform, and the lapping margin can be reduced. Further, as in claims 2 and 5, by controlling the new wire supply speed based on a predetermined relational expression, the new wire supply speed can be controlled based on the ideal wire wear amount. Further, if the wire reciprocating method is adopted as the new wire supplying method as in the third and sixth aspects, the consumption of the wire can be efficiently suppressed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a cutting device using a wire saw.

FIG. 2 is an explanatory diagram for explaining an ideal work cutting method, in which (A) is a cutting load, (B) is an ideal new wire supply speed, and (C) is an (theoretical) ideal wire. The amount of wear.

FIG. 3 is an explanatory diagram of an embodiment of a work cutting method,
(A) is a cutting load, (B) is a new wire supply speed, (C) is a (theoretical) amount of wire wear, and (D) is an actual wafer taper.

FIG. 4 is an explanatory diagram for explaining a cutting load,
(A) cut string length, (B) ingot feed rate,
(C) is a cutting load.

FIG. 5 is an explanatory diagram for explaining a new line supply speed,
(A) is (B) when the new line supply speed is 100m / min.
Is a control method when the new line supply speed is set to 40 m / min.

FIG. 6 is an explanatory diagram showing a state where a glass patch plate is bonded to an ingot.

FIG. 7 is a comparative diagram comparing the effects of the present invention.

FIG. 8 is an explanatory diagram showing a typical example of the effect of abrasion of abrasive grains when cutting with a constant cutting load.

FIG. 9 is an explanatory diagram of a cutting width.

[Explanation of symbols]

1 ... Wire, 2 ... Driving roller, 3 ... Roller, 4 ...
Roller, 5 ... Processing part, 6
… Work holder, 7… Nozzle,
8 ... Slurry receiver, 10 ... Drive motor,
11 ... Control means, A ... Wire sending part, B ... Wire receiving part, d ... Cutting width, G ... Glass patch, W ... Ingot.

Claims (6)

[Claims] 1. A work is pressed against a wire to which a new wire is supplied from a wire sending side toward a wire receiving side at a predetermined speed, and the work is cut while supplying abrasive grain slurry to the pressure contact portion. In the work cutting method, the new wire feeding speed of the wire is controlled by the wear amount of the wire and the degree of wear of the abrasive grains, and by this control, the wear amount of the wire changes linearly while compensating for the wear amount of the abrasive grains. A method for cutting a work with a wire saw, which is characterized in that 2. The method of cutting a work with a wire saw according to claim 1, wherein the new wire supply speed is a cutting load =
(Work cutting length) × (work feed speed), where k is a coefficient, it is controlled based on the relational expression of wire wear amount = k × (cutting load / new wire supply speed) A work cutting method with a wire saw. 3. The work cutting method using the wire saw according to claim 1, wherein the new wire is supplied.
A work cutting method using a wire saw, which is a reciprocating supply system for supplying a wire while reciprocating it at a predetermined timing. 4. A wire feeding drive means for feeding a new wire from a wire sending side to a wire receiving side at a predetermined speed, a work pressing means for pressing a work against the wire, and an abrasive grain slurry for supplying a pressing portion. And a control means for controlling the wire supply driving means, wherein the control means controls the new wire supply speed according to the wear amount of the wire and the degree of wear of the abrasive grains. A work cutting device using a wire saw. 5. The work cutting device using the wire saw according to claim 4, wherein the new wire supply speed is a cutting load =
(Work cutting length) × (work feed speed), where k is a coefficient, it is controlled based on the relational expression of wire wear amount = k × (cutting load / new wire supply speed) Work cutting device with wire saw. 6. The work cutting device using the wire saw according to claim 4 or 5, wherein the supply of the new wire by the wire supply driving means is a reciprocating motion in which the wire feeding direction is reversed at a predetermined timing. A work cutting device using a wire saw, which is a supply system.