Method for simultaneously slicing a plurality of slices from a workpiece by a wire saw

Abstract

A method for simultaneously slicing a plurality of slices from a workpiece by a wire saw is a slice grinding process in which the workpiece is moved perpendicular to the longitudinal axis of the workpiece towards a wire web of a sawing wire stretched between two wire guide rollers, the sawing wire is moved in the longitudinal direction of the sawing wire, a coolant lubricant is supplied to the wire web, fixed to the beam material, and a slice having a slice gap therebetween is generated between the wire sections of the wire web, the slice grinding process; including removal of the beam material and the slice from the wire web, characterized in that during removal of the beam material and the slice, fluid is sprayed into the slice gap by a spraying device until the wire section leaves the slice gap, the fluid being supplied at high pressure through a nozzle fixed to a nozzle bracket that moves so as to vibrate parallel to the longitudinal axis of the workpiece, the fluid and entrained air sometimes stimulating the vibration of the slice.

Description

Technical Field

[0001] The object of the present invention is a grinding and cutting process in which a workpiece is fed perpendicular to the longitudinal axis of the workpiece towards a wire web of a sawing wire passed between two wire guide rollers, the sawing wire moves in the longitudinal direction of the sawing wire, a cooling lubricant is supplied to the wire web, slices are formed between the wire sections of the wire web, the slices are fixed to the beam material, and a slice gap exists therebetween; and removal of the beam material and slices from the wire web and is a method for simultaneously slicing a plurality of slices from a workpiece by means of a wire saw.

[0002] For a plurality of applications, uniform slices with few crystal defects and structural defects and good planar parallelism on their front and back sides are required. An example is the slicing of single-crystal semiconductor materials for the structuring of microelectronic components. This type of slice is obtained, for example, by cutting from a cylindrical workpiece.

Background Art

[0003] Prior Art / Problems Methods and devices for wire sawing are known, for example, from DE 10 2016 211 883 A1. In wire sawing, the sawing wire is guided in a spiral around at least two wire guide rollers so that they span the wire web facing the workpiece, which is made up of wire sections extending parallel to one another. The sides of the wire guide rollers are provided with a number of annular closed grooves which extend in a plane perpendicular to the axis of the wire guide rollers and guide the sawing wire. When the wire guide rollers are rotated in the same direction, a relative movement occurs between the wire sections and the workpiece. The wire saw also has a feed device, in which the workpiece is fixed via a beam to which the workpiece is adhesively bonded, and which feeds the workpiece perpendicularly to the wire web. The relative movement and the presence of the abrasive cutting means result in the removal of material from the workpiece when contact is made between the workpiece and the wire web. With continued feeding, the wire sections form slice gaps in the workpiece and the wire web is worked slowly over the entire workpiece until the wire web is completely located in the saw beam. The workpiece is then cut completely into slices that hang from the beam like teeth of a comb held only by adhesive joints.

[0004] Once the cutting process is finished, the workpieces that have been cut into slices must be withdrawn from the wire web by reversing the direction of movement of the feed device (ingot withdrawal).

[0005] Wire sawing can be differentiated between wire slice lapping and wire slice grinding. In wire slice lapping, the sawing wire is initially free of abrasives and the cutting means is supplied in the form of a slurry as freely moving particles dispersed in a carrier fluid. In wire slice grinding, an abrasive cutting agent is fixed to the surface of the sawing wire and a cutting fluid is supplied, which acts as a cooling lubricant and does not contain abrasive substances.

[0006] The sawing wire is usually composed of hypereutectoid pearlite steel (piano wire). Straight (ordinary) sawing wire and structured (crimped) sawing wire are used.

[0007] In the case of wire slice lapping, the cutting agent is usually composed of silicon carbide (SiC:silicon carbide), and the carrier fluid is usually composed of oil or glycol. In the case of wire slice grinding, the cutting agent is usually composed of water, which may contain a wetting agent and an antifoaming additive in some cases, and the abrasive fixed in the sawing wire is usually diamond.

[0008] In wire sawing, the sawing wire is usually taken from a first stock in the form of a first spool around which the sawing wire is wound, and after use, it is usually sent to a second stock in the form of a second spool. The first spool is called the unused wire spool, and the second spool is called the used wire spool. Wire sawing may involve one-way or two-way wire movement. In the case of one-way wire sawing, the sawing wire moves in the longitudinal wire direction from the unused wire spool to the used wire spool throughout the slicing process. In the case of wire sawing with two-way wire movement, the sawing wire moves during the slicing process by at least a pair of direction reversals, and the pair of direction reversals includes a first movement of the sawing wire in the longitudinal direction of the first wire by a first length and a second movement of the sawing wire in a second direction opposite to the first direction by a second length. Specifically, wire sawing with two-way wire movement may include a plurality of pairs of wire reversals of this kind of direction, and the first length is selected to be greater than the second length, so that the entire wire stock moves from the unused wire spool to the used wire spool during the slicing process. The aforementioned method is called pilgrim mode slicing or wire reciprocating slicing.

[0009] A wire saw is also known for a technique that can rotate a workpiece around an axis parallel to the longitudinal axis of the workpiece during the slicing process. Specifically, this rotational movement can be executed in the form of a continuous sequence composed of multiple pairs of rotational changes. A pair of rotational changes includes a clockwise rotation at a first angular velocity around a first angle and a subsequent counterclockwise rotation at a second angular velocity around a second angle. In this case, the first and second angular velocities as well as the first and second angles may also change during the slicing process, for example, according to the cutting depth or the instantaneous length of the sawing wire within the workpiece. This repetitive swaying motion of this type of workpiece is also called the swaying of the workpiece. An apparatus suitable for this purpose is described, for example, in U.S. Patent Application Publication No. 2022 / 0134600 A1.

[0010] During the slicing process, the material is mainly removed along the contact surface. Along the contact surface, the sawing wire makes material-removing contact with the workpiece and extends in the direction opposite to the workpiece feed direction. This contact surface is called the main cutting surface. The contact surface that takes in the workpiece in the direction perpendicular to this direction, in other words, in the direction of the workpiece axis, is here called the secondary cutting surface because no force acts as a result of the workpiece feed and thus the material is not removed first. The sum of all the instantaneous secondary cutting surfaces of the slice gap throughout the slicing process forms the front and rear sides of adjacent slice pairs.

[0011] During wire sawing without swaying, the main cutting surface extends along the entire arc length from the entry of the sawing wire into the slice gap to the exit of the sawing wire from the slice gap. During wire sawing with swaying, the main cutting surface is always composed of only short arc sections, whereby the sawing wire contacts the slice line between the workpiece and the slice gap, and the slice line curves due to the swaying. Swaying improves the supply of cooling lubricant or slurry to the slice gap even in the case of workpieces with a large diameter.

[0012] In slice lapping, the material removal rate is proportional to the pressure on the primary cutting surface. In slice grinding, the material removal rate rises disproportionately to the pressure on the primary cutting surface. Therefore, slice grinding (not slice lapping) can be carried out with the aid of oscillation more quickly than without oscillation.

[0013] The removal of the workpiece cut from the wire web by slicing is carried out after wire sawing by reversing the workpiece feed. In this case, the sawing wire draws the cutting fluid into the slice gap as lubrication and slowly moves in the wire longitudinal direction to prevent the friction of the sawing wire in the slice gap and the sticking of the individual wire sections between the secondary cutting surfaces of the slice gaps facing each other, and the cutting fluid is added. In ingot recovery after wire slice lapping, most of the slurry drops off the sawing wire due to the low-speed wire movement before the sawing wire enters the slice gap. As a result, the thickness of the slurry film surrounding the sawing wire in the slice gap is substantially smaller than the thickness of the slurry film during the preceding slicing process. Therefore, there is play in the sawing wire in the slice gap during ingot recovery after wire slice lapping, and it does not stick. This is advantageous for the uniform sliding of the wire web that finally exits the gap through the slice gap without the sawing wire sticking between the secondary cutting surfaces of the gap or causing the removal of material from the secondary cutting surfaces.

[0014] In the case of wire slice grinding, there is no slurry of the cutting means surrounding the sawing wire. Therefore, the width of the slice gap is the same as the wire diameter including the diamond incorporated in the sawing wire. Therefore, during ingot recovery, there is no play in the sawing wire within the slice gap, which means that it frequently adheres at different cutting depths. Therefore, a slow longitudinal movement of the wire means that further material removal is immediately performed and a cut is formed on the wall of the slice gap. Since the walls of the slice gap form the front side of one slice and the rear side of the immediately adjacent slice, the cut is thereby formed within the wafers obtained separately. Slices having cuts on the surface are not suitable for demanding applications.

[0015] The sawing wire remains fixed at the cutting depth during ingot recovery after wire slice grinding, but the feeding device is further reset. Therefore, the sawing wire bends in the wire transverse direction, thereby being elastically stretched in the wire longitudinal direction. Thereby, the sawing wire encounters an increasing restoring force. When this grows sufficiently, the sawing wire jumps from the cutting depth at which it was fixed during recovery to a smaller cutting depth at which it becomes fixed again, and so on (stick and slip motion of the sawing wire). Due to the elongation of the wire in the longitudinal direction caused by the transverse bending of the sawing wire, if the tension exceeds the material strength of the sawing wire, the sawing wire breaks during ingot recovery. In this case, the workpiece has to be completely removed from the defective wire web, the remaining wire is manually removed from the slice gap, and the wire web is repaired before the next slicing process. This is time-consuming and costly.

[0016] The sawing wire sometimes breaks during the slicing process due to overload or material defects within the sawing wire. Subsequently, the partially sliced workpiece must be removed from the defective wire web by resetting the feeding device, the remaining wire is removed from the slice gap, the wire web is repaired, the wire section is screwed back into the existing slice gap, and the workpiece is sent again to the cutting depth at which the wire break occurred, so that the slicing process can be completed. In the case of wire slice lapping, the screwing and feeding of the workpiece within the wire web is easily done and the sawing wire is not involved in the given cutting depth because the sawing wire has sufficient play within the slice gap due to the surrounding slurry film. In the case of wire slice grinding where the sawing wire has no freedom of movement, the sawing wire gets stuck during the feeding of the workpiece and a cut is generated.

[0017] Even if the diamond-coated sawing wire gets caught in an unpredictable way during the feeding of the workpiece after the wire breaks or when the feeding is reset from the wire web during ingot recovery, in either case, since there is no freedom of movement, material is further removed from the side walls defining the gap, and thus the front and back sides of the relevant slice are damaged. This type of damage causes material stress within the damaged surface that causes elastic deformation in the slice when the stresses on the front and back sides of the slice are not balanced with each other (which is usually not the case). This elastic deformation due to surface damage overlaps with plastic deformation, and since plastic deformation cannot be determined alone by measuring the slice shape after wire sawing, it cannot be selectively removed by appropriate means either. The latter is necessary because the elastic deformation disappears when the damaged layer is removed in subsequent material removal processes, but the plastic deformation remains if it is not removed by selective material removal.

[0018] U.S. Patent Application Publication No. 2009 / 0223539 A1 describes a method for cleaning wafers for photovoltaic applications. For example, the wafers are immersed in a cleaning bath at the end of the slicing process and upon removal from the wire saw, still suspended from the saw beam (sacrificial beam) by their adhesive joints. The slice gaps are exposed to rinsing fluid from a plurality of separate spray nozzles. At the point where the rinsing fluid is sprayed, the slice gaps widen within the water tank, enhancing the cleaning action. By moving the nozzles relative to the workpiece, all the slice gaps can be widened successively, thereby enabling continuous cleaning. The described method does not contribute to avoiding the stick and slip motion of the sawing wire during ingot recovery.

[0019] JP-A-2006-66793 describes a similar method in which, at the completion of the slicing process and upon removal from the wire saw, spray fluid is sprayed onto a block of cut slices and the sides are cleaned by spray nozzles.

[0020] U.S. Patent Application Publication No. 2011 / 0168212 describes a similar method for cleaning thin and easily breakable solar wafers after sawing and removal of the sliced workpiece from the wire saw.

[0021] JP-A-2004-106360 describes a method in which, after wire slicing lapping and ingot recovery of the workpiece, rinsing fluid is sent through channels present within the beam to clean the slice gaps. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0022] An object of the present invention is to avoid the stick and slip motion of the sawing wire and its adverse consequences. MEANS FOR SOLVING THE PROBLEM

[0023] The object of the present invention is a slicing grinding process in which the workpiece is moved in a direction perpendicular to the longitudinal axis of the workpiece towards a wire web of a sawing wire stretched between two wire guide rollers, the sawing wire is moved in the longitudinal direction of the sawing wire, a cooling lubricant is supplied to the wire web, fixed to the beam material, and a slice having a slice gap therebetween is generated between the wire sections of the wire web, the slicing grinding process, including the removal of the beam material and the slice from the wire web, characterized in that fluid is sprayed into the slice gap by a spraying device during the removal of the beam material and the slice until the wire section leaves the slice gap, the fluid is supplied at high pressure through a nozzle fixed to a nozzle bracket that moves so as to vibrate parallel to the longitudinal axis of the workpiece, and the fluid and air intermittently stimulate the vibration of the slice. It is achieved by a method for simultaneous cutting of a plurality of slices from a workpiece by a wire saw.

[0024] During removal, the nozzle sprays fluid into the slice gap. During this time, the surrounding air swirls and the slice is vibrated by the Bernoulli effect. The nozzle bracket performs a vibrating stroke motion parallel to the workpiece axis, which is why fluid from at least one nozzle in the plane of the corresponding slice gap sometimes encounters each slice gap. In this way, the fluid penetrates deeply into the slice gap, and the change in the spray pressure caused by the vibrating motion gradually causes continuous periodic fanning of all the slice gaps during the removal of the strip and the slice from the slice gap.

[0025] The pressure at which the fluid is supplied through the nozzle is preferably selected such that the outlet velocity of the rinsing agent corresponds to the velocity at which the wire moves relative to the workpiece.

[0026] The nozzle is preferably a component of a spraying device with at least one nozzle bracket in each case. The nozzle bracket is arranged on the side of the wire guide roller of the wire web between each wire guide roller and the workpiece. The nozzle bracket can perform a stroke movement parallel to the workpiece axis and is preferably arranged parallel to the axis of rotation of the wire guide roller.

[0027] Particularly preferred is exactly two nozzle brackets. For the nozzle brackets, when viewed in the direction of the workpiece axis, unused wire is arranged on the inlet side of the workpiece and used wire is arranged on the outlet side. The nozzle is preferably oriented such that each nozzle generates a partial flow of fluid oriented tangentially to the wire web in one of the planes in which the slice gap extends. The amplitude of the oscillating movement in which each nozzle bracket moves parallel to the longitudinal axis of the workpiece is preferably at least half of the space between two adjacent nozzles. Thus, the total stroke corresponding to twice the amplitude is at least the space between two nozzles. In this way, after the period of the oscillating movement, it is ensured that each nozzle covers all the slice gaps located between this nozzle and the adjacent nozzles.

[0028] The number of nozzles per nozzle bracket is preferably between 10 and 50. The maximum possible number of nozzles is particularly preferred. The upper limit of the number is determined only by the dimensions of the nozzles. Thus, the required stroke of the oscillating movement of the nozzle bracket is smaller and the covering of the slice gaps takes place at shorter intervals.

[0029] During the slice grinding process, the workpiece is fed by a feeding device. Since the wire guide rollers rotate in the same direction, the wire section describes a relative movement with respect to the workpiece and material removal takes place during engagement with the workpiece as a result of the feeding movement.

[0030] At the end of the slice grinding process, the workpiece is completely sliced, a plurality of slice gaps extending parallel to each other between the slices are created, and the slices are held by the beam material.

[0031] Removal of the beam material and slices from the slice gaps includes resetting the feed device while the wire section moves in the longitudinal direction of the wire in the presence of a coolant lubricant.

[0032] The workpiece is preferably a cylindrical rod composed of a single crystal semiconductor material. The method also preferably includes turning the workpiece about an axis parallel to the longitudinal axis of the workpiece during the slice grinding process, the workpiece performing a plurality of pairs of turning movements, and a pair of turning movements including a first turn about a first angle at a first angular velocity and a subsequent second turn about a second angle at a second angular velocity. The first and second angular velocities and the first and second angles of two pairs of successive pairs of turning movements are preferably different.

[0033] The sawing wire is preferably a hypereutectoid pearlitic steel wire (piano wire) having cutting means fixed to its surface. The cutting means is preferably diamond.

[0034] The longitudinal movement of the sawing wire during the slice grinding process can be performed with or without a reversal of direction. During the longitudinal movement of the sawing wire with a reversal of direction, the sawing wire moves by a plurality of pilger steps, and each pilger step includes a first movement of the sawing wire of a first length in a first longitudinal direction and a second movement of the sawing wire of a second length in a second longitudinal direction opposite to the longitudinal direction of the first wire, the first length being greater than the second length.

[0035] Cooling lubricants and fluids are preferably made from water, optionally containing liquid additives. They may both have the same or different compositions. The liquid additives are preferably wetting agents, corrosion inhibitors, viscosity modifiers such as glycols and / or methylcellulose, defoamers, or any mixture of these agents.

[0036] The procedure according to the invention is also preferably used to appropriately react to an interruption of the slicing grinding process, particularly as a result of the breaking of the sawing wire. It prevents the wire section from sticking and grooves or elastic deformations from adversely affecting the quality of the slice during the removal of the workpiece after the wire breaks and during the reverse movement of the workpiece back to the position before the wire break.

[0037] The interruption of the slicing grinding process is carried out while the longitudinal movement of the sawing wire continues and includes the removal of the workpiece from the slice gap, the return of the workpiece to the slice gap, and the continuation of the slicing grinding process. During the return of the workpiece, the fluid is sprayed into the slice gap through the nozzle, and the nozzle bracket moves parallel to the longitudinal axis of the workpiece.

[0038] The longitudinal movement of the sawing wire during the slicing grinding process is preferably carried out at a speed at least 10 times faster than the speed of the longitudinal movement of the sawing wire during the removal and return of the workpiece when the slicing grinding process is interrupted.

[0039] The present invention is presented below with reference to the drawings in a preferred exemplary embodiment of a wire saw.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2(A)

Figure 2(B)

DETAILED DESCRIPTION OF THE INVENTION

[0041] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION As shown in FIG. 1, during wire sawing, the sawing wire 4 is spirally guided around at least two wire guide rollers 5 and 6 such that the two wire guide rollers span a wire web 24 facing a workpiece 1 composed of wire sections extending parallel to each other. The wire guide rollers are oriented parallel to each other and have a straight cylindrical shape with rotation axes 7 and 8 around which they can rotate in direction 11. On the side surfaces of the wire guide rollers, a plurality of annular closed grooves 23 are provided which extend in a plane perpendicular to the rotation axes 7 and 8 and guide the sawing wire 4. When the wire guide rollers are rotated in the same direction, a relative movement occurs between the wire section and the workpiece. In this case, the unused sawing wire is taken from a first wire stock, a so-called unused wire spool (direction 9), and the used sawing wire is sent to a second wire stock, a so-called used wire spool (direction 10). The wire saw also has a feeding device by which the workpiece 1 is fixed thereto by an adhesive joint 25 with a beam material 2 and the workpiece is fed perpendicular (direction 3) to the wire web. The presence of the relative movement and the abrasive cutting means results in the removal of material from the workpiece upon contact between the workpiece and the wire web. Through the continuous feeding, relative movement, and supply of the cutting means, each wire section of the wire web 24 forms a slice gap 22 by continuous material removal from the workpiece. The side walls of the slice gap 22 each define the rear side and the front side of a second slice 34 of a pair of directly adjacent wafers.

[0042] The cutting means is the diamond 33 fixed and incorporated on the surface of the wire 1. During the slice grinding process, the cooling lubricant 15 is supplied to the wire web 24 through the two nozzle brackets 12 and 13 on the left and right of the workpiece provided with the nozzle 14, and the cooling lubricant itself does not contain abrasive cutting means (hard substances). The slice grinding process ends when the entire wire web has completely processed the workpiece and comes to rest within the beam material 2. Then, the slices 34 of the completely cut workpiece hang down like the teeth of a comb from the half-slice through-beam material connected only to the beam material 2 by the adhesive joint 25.

[0043] The illustrated wire saw is provided with a left nozzle bracket 16 and a right nozzle bracket 17. The nozzle brackets 16 and 17 have a plurality of nozzles 20 for spraying the fluid 21 into the slice gap 22 in the workpiece 1. The axes 18 and 19 of the nozzle brackets are arranged parallel to each other, perpendicular to the slice gap 22 of the workpiece 1, or parallel to the rotation axes 7 and 8 of the wire guide rollers 5 and 6 that stretch the wire web 24 parallel to the longitudinal axis 26 of the workpiece 1. The nozzle brackets perform oscillating motions 27 and 28 in the directions of their axes 18 and 19. Due to this periodic displacement, the flow of the fluid 21 exiting each nozzle 20 covers the slice gap 22 of the workpiece 1 at periodic intervals.

[0044] The preferred arrangement according to FIG. 1 shows, when viewed from the direction of the feeding device, the nozzle bracket 16 on the left side of the workpiece 1, which is both below the wire web 24, in other words, on the inlet side of the unused wire, and the nozzle bracket 17 on the right side of the workpiece 1, in other words, on the outlet side of the used wire. Deviating from this, the nozzle brackets may be arranged above the wire web 24.

[0045] As already stated, the method according to the invention may also be carried out using a wire saw, in which the workpiece can rotate around an axis parallel to the longitudinal axis of the workpiece during the slicing process. During this oscillation, only a partial section of the entire wire section extending within the slice gap is in material-removing contact with the workpiece at any given time. When viewed in the wire longitudinal direction, gaps are formed in front of and behind this momentary contact surface between the sawing wire and the workpiece extending in the workpiece feed direction. When the nozzle bracket is arranged above the wire web, the fluid can enter particularly well between the sawing wire and the workpiece. When the nozzle bracket is arranged below the wire web, the fluid can substantially not enter between the sawing wire and the workpiece, regardless of the oscillation. On the other hand, in this case, the cut portion of the workpiece (subsequent wafer) protruding below the wire web is vibrated particularly effectively by the Bernoulli effect of the fluid flow, causing a periodic expansion and contraction of the slice gap width thereby.

[0046] Figures 2(A) and 2(B) show details of a spraying device comprising nozzle brackets 16 and 17 in a plan view (seen from the direction of the feed device) on the left nozzle bracket 16, and a part of the workpiece 1 having slice gaps 22 and a longitudinal axis 26 of the workpiece.

[0047] Figure 2(A) shows a nozzle bracket 16 having an axis 18 parallel to the longitudinal axis 26 of the workpiece at the start of the oscillatory movement 27 parallel to the axis 18. There is a nozzle 31, and a part of the flow of fluid 21 therefrom flows exactly within the plane of the slice gap 22 in any case, and as a result, the fluid 21 is deeply pushed into the slice gap 22. During this process, a pair of adjacent slices 34 divided by the slice gap 22 are pressed to elastically move away from the slice gap in the moving direction 29, and as a result, the slice gap is elastically expanded to an expanded slice gap 30. Moreover, there is a nozzle 32 from which none of the flow of fluid 21 flows within the plane of the slice gap 22 and thus does not elastically expand the slice gap. The flow of fluid 21 entrains air 35 from the environment by momentum exchange.

[0048] When the left nozzle bracket 16 executes the oscillatory movement 27 in the direction of the axis 18, it reaches the position shown in Figure 2(B) at the other end of the oscillatory movement. The nozzle 31, from which a part of the flow that pushes fluid into the slice gap and expands it, is in a different position from that in the arrangement according to Figure 2(A), and expands other slice gaps. The amplitude of the oscillatory movement 27 is the value of the space between at least two adjacent nozzles.

[0049] During the oscillatory movement 27, the flow of fluid 21 (incompressible fluid) and the flow of air 35 (compressible air / gas) entrained by the flow spread beyond the slices 34 and the slice gap 22. Since they flow around slices and slice gaps in different planes during the oscillatory movement, the slices 34 are stimulated by the dynamic air pressure changes of the air entrained by the flow to generate vibrations (Bernoulli effect). In other words, elastic deflection of the slices and periodically expanding and tapering slice gaps are caused.

[0050] An investigation based on the present invention, which aims to avoid the sticking and slipping of the sawing wire during ingot recovery and during the repositioning of the workpiece after the slicing grinding process is interrupted, has shown that in order to reduce the frictional force of the sawing wire in a narrow slice gap, stimulation of vibration in the slice is necessary. The expansion of the slice gap by forcibly pushing a fluid when changing the slice gap, and the cleaning effect associated with this as a single means, is carried out very slowly. Therefore, it is not possible to prevent the sawing wire from generating grooves or warping due to distortion during ingot removal or during the repositioning of the workpiece after interruption.

[0051] Only the stimulation of vibration in the slice by the Bernoulli effect through the flow of fluid and entrained air has been proven to be an appropriate means to achieve the objective.

Explanation of Signs

[0052] List of reference signs used 1 Workpiece 2 Beam material 3 Feed direction 4 Sawing wire 5 Left wire guide roller 6 Right wire guide roller 7 Rotation axis 8 Rotation axis 9 Wire supply direction 10 Wire removal direction 11 Rotation direction of wire guide roller 12 Bracket 13 Bracket 14 Nozzle 15 Cooling lubricant 16 Left nozzle bracket 17 Right nozzle bracket 18 Axis of left nozzle bracket 19 Axis of right nozzle bracket 20 Nozzle 21 Fluid 22 Slice gap 23 grooves 24 wire web 25 adhesive joint 26 longitudinal axis of workpiece 27 oscillatory motion 28 oscillatory motion 29 direction of movement 30 enlarged slice gap 31 nozzle 32 nozzle 33 diamond 34 slice 35 entrained air

Claims

1. A method for simultaneously slicing a plurality of slices from a workpiece by a wire saw, comprising: A slicing grinding process in which the workpiece moves in a direction perpendicular to the longitudinal axis of the workpiece toward a wire web of a sawing wire stretched between two wire guide rollers, the sawing wire moves in the longitudinal direction of the sawing wire, a cooling lubricant is supplied to the wire web, a slice fixed to a beam material and having a slice gap therebetween is generated between wire sections of the wire web, the slicing grinding process; Removing the beam material and the slice from the wire web; Characterized in that during removal of the beam material and the slice until the wire section leaves the slice gap, fluid is sprayed into the slice gap by a spraying device, the fluid being supplied at high pressure through a nozzle fixed to a nozzle bracket that moves so as to vibrate parallel to the longitudinal axis of the workpiece, the fluid and air intermittently stimulating the vibration of the slice.

2. The method according to claim 1, characterized in that the amplitude of the vibration is equal to or greater than the entire space between two adjacent nozzles.

3. Characterized in that the slicing grinding process is interrupted while the sawing wire is continuously moving in the longitudinal direction, Removing the workpiece from the slice gap, Returning the workpiece into the slice gap, Continuing the slicing grinding process, during which return of the workpiece, fluid is sprayed into the slice gap through the nozzle, and the nozzle bracket moves parallel to the longitudinal axis of the workpiece, the method according to claim 1 or claim 2.

4. Characterized by turning of the workpiece around an axis parallel to the longitudinal axis of the workpiece during the slicing grinding process, the workpiece performing a plurality of turning motions, one turning motion including a first turn of a first angle at a first angular velocity and a second turn of a second angle at a subsequent second angular velocity, the method according to any one of claims 1 to 3.

5. The method according to claim 4, characterized in that the first and second angular velocities and the first and second angles of two of the successive turning motions are different. Claim 6 The method according to any one of claims 1 to 5, characterized in that the coolant lubricant contains water and a first liquid additive, and the fluid contains water and a second liquid additive. Claim 7 The method according to claim 6, characterized in that the first and second liquid additives are the same and contain a wetting agent or a corrosion inhibitor or a viscosity modifier, an antifoaming agent, or a mixture thereof. Claim 8 The method according to any one of claims 1 to 7, characterized in that the sawing wire is composed of a hypereutectoid pearlitic steel wire having a diamond fixed to the surface as a cutting means. Claim 9 The method according to any one of claims 1 to 8, characterized in that the workpiece is a cylindrical rod of a single crystal semiconductor material. Claim 10 The method according to claim 3, characterized in that the longitudinal movement of the sawing wire during the slicing grinding process is at least 10 times faster than the longitudinal movement speed of the sawing wire during the removal and return of the workpiece. Claim 11 The method according to any one of claims 1 to 10, characterized in that the longitudinal movement of the sawing wire without reversal of direction. Claim 12 The method according to any one of claims 1 to 10, characterized in that the longitudinal movement of the sawing wire involves reversal of direction, and the sawing wire moves by a plurality of pilger steps, each pilger step including a first movement of the wire of a first length in a first longitudinal direction and a second movement of the sawing wire of a second length in a second longitudinal direction opposite to the longitudinal direction of the first wire of the second length, and the first length is greater than the second length.

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