WO2011141543A1

WO2011141543A1 - Wire sawing device for producing wafers

Info

Publication number: WO2011141543A1
Application number: PCT/EP2011/057688
Authority: WO
Inventors: Thomas Vogel
Original assignee: Thomas Vogel
Priority date: 2010-05-12
Filing date: 2011-05-12
Publication date: 2011-11-17
Also published as: DE102010028931A1

Abstract

The present invention relates to a wire sawing device (10) for producing wafers, in particular for the semiconductor and photovoltaic industry, wherein the wire sawing device (10) comprises a wire field (18) of a sawing wire (16) that can be moved in the longitudinal extent, wherein the movable sawing wire (16) runs around at least two spaced-apart guiding rollers (12), provided with guiding grooves (14), to form the wire field (18), whereby the sawing wire (16) is taken repeatedly back and forth parallel to itself and defines the wire field (18), wherein the sawing wire (16) is a continuous wire and wherein the sawing wire (16) is led back from a last guiding groove (14) to a first guiding groove (14) over precisely two deflecting rollers (20).

Description

Wire saw apparatus for producing wafers

The invention relates to a wire saw apparatus for producing wafers for the semiconductor industry, the wire saw apparatus comprising a wire field of a longitudinally movable saw wire, wherein the movable saw wire runs around at least two guide grooves provided with guide grooves to form the wire field, whereby the saw wire multiple times is guided parallel to each other in the wire field, and the saw wire is an endless wire.

As a wafer, in the semiconductor, photovoltaic and micromechanical industries, a circular or square slice about 0.2 mm to 1 mm thick, e.g. silicon, which constitutes a substrate (base plate) on which electronic components, in particular integrated circuits, micromechanical components or photoelectric coatings, are produced by various technical processes. The largest part, however, is used for photovoltaic systems. In a production, several wafers are generally combined into one lot and preferably produced in parallel by sawing a material blank into individual slices. The wafer preferably consists of monocrystalline or multicrystalline silicon.

Silicon and comparable semiconductor materials are characterized by a comparatively high brittleness, to which a machining process must be adapted. Therefore, for cutting semiconductor wafers, for example, a silicon ingot which may be formed with a round or square cross-section, a wire sawing machine designed as a multiwire saw is usually used.

The sawing function of the well-known multiwire saw results from the fact that from a wire spool up to 100 km saw wire over guide rollers several thousand times is deflected and thus forms a wire field or a wire grid with mutually parallel cutting wires (similar to an egg cutter). At the end, the saw wire is rewound onto another spool. The guide rollers must have an identical speed, so that the saw wire does not crack. The wire field formed in this way allows several thousand wafers to be cut simultaneously. EP 1 955 813 B1 shows a method with such a wire saw apparatus.

To this day, some are still sawed with bare wire and loose cutting material (slurry), more specifically, lapped. After a pass, the wire is so damaged that it is unusable. Conventionally, therefore, a saw wire coated with diamond is becoming increasingly common. This can be used several times. When sawing in only one direction, lengths of up to 100 km of wire are required, otherwise sawing direction changes are unavoidable. These disadvantageously cause deep notches in the raw material. In addition, brake and acceleration changes in the direction changes lead to high wear in the wire saw device. Another disadvantage is that the diamond saw wire destroys itself on the spool itself without touching the workpiece.

From JP 11-138411 A and JP 11-188602 A a sawing device is known, in which an endless wire is used. The return of the wire via a clamping device with a plurality of small pulleys, whereby the saw wire is bent several times in different directions. This bending load is disadvantageous for the saw wire.

DE 35 32 717 A 1 shows a wire saw with an endless saw wire, in which the saw wire is guided over two or three guide rollers and the saw wire is additionally tensioned by a tensioner. The device requires no pulleys for returning the saw wire.

The invention is therefore an object of the invention to provide a wire saw, can be moved with the saw wire with small wire lengths of the saw wire in only one direction and in which the wear is reduced both in the wire saw device and the saw wire.

The object is achieved by means of a wire saw device of the type mentioned above in that the Endlossägedraht is returned via exactly two pulleys from a last guide groove to a first guide.

The saw wire thus continuously traverses during a sawing process in the wire saw device. As a result, the saw wire can be made relatively short in contrast to the saw wire in a wire saw apparatus according to the prior art. The known unwinding of a first coil before the sawing process and the subsequent winding of the saw wire on a second coil after the sawing process can be omitted advantageously. Thus, the saw wire, in particular the diamond saw wire, during winding advantageously can no longer destroy itself. In addition, when using the endless wire rod, the direction of movement of the saw wire can be maintained during the sawing operation. Change of direction of the saw wire are not necessary. As a result, caused by changes in direction of the saw wire notches in the raw material can be avoided. In addition, the wear in the wire saw device is reduced by the no longer necessary brake and acceleration changes in the direction changes.

The saw wire in the wire saw apparatus according to the invention must have substantially only the length which is necessary to guide the saw wire through all the guide grooves of the guide rollers sequentially, so that the desired wire field is formed. To this length then only a short piece of saw wire must be added to merge the two saw wire ends to Endlossägedraht. The Endlossägedraht can be produced easily and inexpensively by known cohesive and load-bearing method, such as a welding method for connecting the two saw wire ends.

According to the Endlossägedraht is returned via exactly two pulleys from a last guide groove to a first guide groove of the guide rollers. The Endlossägedraht is preferably returned to the wire field in such a long distance that the return of the saw wire does not interfere with the sawing process in the Drahtsägevorrichtung.

The pulleys can be arranged such that the two pulleys lead the saw wire diagonally across the wire field. However, it is also possible for the two deflection rollers to guide the saw wire in an area outside the wire field of the wire saw device. In both versions, the additional saw wire requirement is low. The pulleys are inexpensive devices, so that no increased costs.

Advantageously, the drive of the wire saw device via the guide rollers. But also the pulleys drive the saw wire or at least support its drive.

Also, the necessary tensioning of the saw wire in the wire field can be done via the guide rollers. This is done e.g. by a rotation angle difference between the guide rollers. About the pulleys can advantageously but also the saw wire stretched or clamping at least be supported. For this purpose, at least one of the deflection rollers, for example via a force acting on the deflection roller weight, spring element and / or a hydraulically or pneumatically operated cylinder, the saw wire held on train. At least the affected pulley is arranged on a vertical support. Of course, the weight, the spring element and / or the hydraulically or pneumatically operated cylinder can also engage other parts of the wire saw device and tension the saw wire. These measures are used to reduce disturbances during the sawing process and possibly completely avoid them.

Advantageously, a wire breakage control is provided to prevent major damage during the sawing process. The wire breakage control device comprises at least two electromagnetically acting coils. For this purpose, a coil in Endlossägedraht generates an electric current, which in turn induces a current through its magnetic field in the other coil. In a wire break, the current flow is interrupted, so that the magnetic field, for example in a control device of the wire saw device, is no longer detectable. This leads to a rapid detection of the wire breakage, so that in this case immediately measures to prevent major damage and to remedy the wire break can be initiated.

Further advantages, features and details of the invention will become apparent from the subclaims and the following description in which two preferred variants of the invention are described in detail with reference to the drawing. The features shown in the drawing and mentioned in the description and in the claims may each be essential to the invention individually or in any combination.

In the drawing show:

FIG. 1 shows a wire saw apparatus according to the invention in a first embodiment;

FIG. 2 shows a wire saw apparatus according to the invention in two different second embodiments;

FIG. 3 shows the wire saw apparatus according to FIG. 1 installed in a frame;

FIG. 4 shows an embodiment of the wire breakage control;

Figure 5 is a detail view of a saw wire;

FIG. 6 shows two inner mandrels arranged in the frame according to FIG. 3 for supporting guide rollers; and

Figure 7 shows two arranged in a drawer guide rollers.

1 shows a perspective view of a first embodiment of the wire saw apparatus 10 according to the invention. The wire saw apparatus 10 comprises two guide rollers 12 which have a multiplicity of guide grooves 14 parallel to one another. In the guide grooves 14, a Endlossägedraht 16, preferably a diamond saw wire, guided by being successively looped through all the guide grooves 14 of the guide rollers 12, so that a wire field 18 results from a plurality of parallel to each other saw wire 16 parts.

Of the first guide groove 14 of the first guide roller 12 of Endlossägedraht 16 is guided over two guide rollers 20 to the last guide groove 14 of the second guide roller 12 diagonally across the wire array 18. The guide rollers 20, like the guide rollers 12, also each have a guide groove.

During the sawing process, the guide rollers 12 move in the direction of rotation 22 and thus continuously move the entire wire field 18 in the longitudinal direction of the saw wire 16 in a predetermined direction. In order to ensure reliable spreading of the wire saw apparatus 10, there is the possibility that the guide rollers 12 in the wire saw apparatus 10 may be ground and / or re-profiled. The direction of movement of the wire field 18 does not have to be changed or changed during the sawing process. The saw wire 16 circulates in the wire saw apparatus 10 in one direction. A first above the wire array 18, e.g. Material block 24 consisting of silicon is pressed onto the wire panel 18 during the movement of the wire field 18, so that the individual saw wire parts or sections of the endless wire 16 cut the block 24 into individual slices, which can subsequently be used, for example, as wafers for the semiconductor industry.

Figures 2a and 2b show a perspective view of the wire saw apparatus 10 according to the invention in a second embodiment. The essential difference to the wire saw device 10 according to FIG. 1 is the lateral arrangement of the two deflection rollers 20. In the second embodiment, the wire field 18 is freely accessible. The deflection rollers 20 are arranged outside the wire field 18, so that the endless wire 16 is guided next to the wire field 18. In this case, the Endlossägedraht 16 is guided by the first guide groove 14 of the first guide roller 12 via two pulleys 20 to the last guide groove 14 of the same guide roller 12 on the wire array 18 substantially tangentially.

In both embodiments, it may additionally be provided that at least one of the deflection rollers 20 is used for tensioning the wire field 18. For this purpose holds at least one of the deflection rollers 20, for example via a force acting on the guide roller 20 weight, spring element and / or a hydraulically or pneumatically operating cylinder (not shown), the saw wire 16 to train. At least the affected deflecting roller 20 is arranged on a vertical support 28 (see FIG. 3) and displaceably mounted in the vertical direction, wherein it is urged upwards by the clamping force.

FIG. 3 shows a cuboid cabinet-shaped frame 26 into which the wire saw apparatus 10 of the first embodiment (FIG. 1) is installed. The frame 26 has one or more windows in order to observe the operations of the wire saw apparatus 10 from the outside. The pulleys 20 protrude above the frame 26 and are rotatably mounted on vertical brackets 28.

In addition, on the outside of the frame 26, a device 30 for mounting the saw wire 16 for generating the wire array 18 is arranged, which comprises a rotatably mounted unwinding roll 32 for the saw wire to be wound, which is not shown in Figure 3, and two rotatably mounted guide rollers 34 for bringing the saw wire 16 to the wire sawing apparatus 10. The two guide rollers 34 are arranged transversely to each other, wherein one of the guide rollers 34 is slidably mounted on a laterally projecting bracket 36 so that they can follow the saw wire. The guide rollers 34 are arranged on the frame 26, that the guide rollers 20 can be used for mounting the saw wire 16 by directing the saw wire 16 directly into the first or last guide groove 14 of the guide rollers 12.

FIG. 4 shows a variant of a wire break check 48 for saw wire 16. For this purpose, two magnet coils 38, 38 'are arranged around a saw wire 16 leading to a guide roller 20 and saw wire 16 coming from the other guide roller 20. A preferred running direction of the saw wire 16 is indicated by the arrows 22. To operate the wire breakage control 48, an alternating electrical current I is passed through the magnetic coil 38. The magnetic coil 38 generates in the Endlossägedraht 16 an induction current that flows in non-torn Endlossägedraht 16 taking into account an ohmic resistance through the Endlossägedraht 16. The current flowing through the sawing wire 16 could also be fed in another way, for example by means of an electrically conductive roller spring-mounted on the sawing wire 16. This current then induces a current I 'in the magnetic coil 38'. If no current I 'generated, the current flow in Endlossägedraht 16 is interrupted; Endlosägedraht 16 is torn and appropriate measures can be initiated.

A possible measure could be a complete replacement of the saw wire 16. Possible and possibly time-saving is an assembly of the torn ends of the saw wire 16 within the wire saw apparatus 10, for example by welding. This process must be carried out already after the saw wire 16 has been wound up to form the end-of-wire saw wire. This is preferably possible outside of the wire field 18, for example between the deflection rollers 20. For better weldability of the saw wire 16 may be at least partially uncoated.

FIG. 5 shows, in an enlarged view, a section of the sawing wire 16 which has, for example, diamond-coated regions 40 and uncoated regions 42.

For a rapid replacement of the guide rollers 12 is provided in the wire saw apparatus 10 in a preferred embodiment that the guide rollers 12 are each mounted on an inner mandrel 44. FIG. 6 shows the frame 26 with two inner mandrels 44 arranged therein. A further simplification for dismantling and assembling the guide rollers 12 is realized in that the guide rollers 12 are arranged in an extendable, drawer-like device 46, which is shown in FIG.

Claims

Wire saw apparatus (10) for producing wafers, in particular for the semiconductor and photovoltaic industry, wherein the wire saw apparatus (10) comprises a wire field (18) of a longitudinally movable saw wire (16), wherein the movable saw wire (16) by at least two from each other spaced, provided with guide grooves (14) guide rollers (12) for forming the wire field (18) runs, whereby the saw wire (16) is guided several times parallel to each other and the wire field (18) spans, wherein the saw wire (16) is an endless wire, characterized in that the sawing wire (16) via exactly two deflection rollers (20) from a last guide groove (14) is returned to a first guide groove (14).
Wire saw apparatus according to claim 1, characterized in that at least one guide roller (12) drives the saw wire (16).
Wire saw apparatus according to claim 1 or 2, characterized in that at least one deflection roller (20), a weight, a mechanical spring and / or a hydraulically or pneumatically operated cylinder tension the saw wire (16).
Wire saw apparatus according to claim 1 or 2, characterized in that at least one deflection roller (20) for tensioning the saw wire is acted upon by a weight, a mechanical spring and / or a hydraulically or pneumatically operating cylinder.
Wire saw device according to one of the preceding claims, characterized in that the two deflection rollers (20) the saw wire (16)

- lead diagonally across the wire panel (18); or

- Pass in an area outside the wire field (18).
Wire saw apparatus according to one of the preceding claims, characterized in that the saw wire (16) continuously rotates in one direction.
Wire saw apparatus according to one of the preceding claims, characterized in that a rotation angle difference between the at least two guide rollers (12) biases the saw wire (16).
Wire sawing device according to one of the preceding claims, characterized in that the sawing wire (16) over the two deflection rollers (20)

- Is guided by the one guide roller (12) to the other guide roller (12); or

- From the one guide roller (12) to the same guide roller (12) is guided back.
Wire saw apparatus according to one of the preceding claims, characterized in that the wire saw device (10) comprises a wire breakage control device (48) comprising at least two electromagnetically acting coils (38, 38 '), the current based on the Endlossägedraht (16) a current from the transfer one to the other coil.
Wire saw apparatus according to one of the preceding claims, characterized in that the saw wire (16) is partially uncoated.
Wire saw apparatus according to one of the preceding claims, characterized in that it comprises a device (30) for mounting the saw wire (16), wherein the device (30) has at least two guide rollers (34) for at least one unwind roll (32).
Wire saw apparatus according to claim 11, characterized in that the wire roller (16) supplying wire roll is arranged perpendicular or parallel to the guide rollers (12).
Wire saw device according to one of the preceding claims, characterized in that the at least two guide rollers (12) are each mounted on an inner mandrel (44).
Wire saw apparatus according to one of the preceding claims, characterized in that the guide rollers (12) are arranged in a drawer-like device (46).
Wire saw apparatus according to one of the preceding claims, characterized in that at least one of the deflection rollers (20) can be used for mounting the saw wire (16).