FIELD OF THE INVENTION

This invention relates to a cutting machine and a method of cutting and refers particularly, though not exclusively, to a cutting machine for cutting a blank such as, for example, an ingot of a semiconductor or other material, and a method of cutting such a blank.

BACKGROUND OF THE INVENTION

The cutting of blanks such as, for example, ingots, of semiconductor material is normally performed by using a large number of parallel fine wires to perform the cutting action in the presence of a slurry that is sprayed onto the wires as they commence the cutting action. A spray of air is used immediately after the cutting action in an attempt to clean the wires. The ingot may be, for example, of silicon and the cutting may be to produce individual wafers for fabrication of devices for various industries such as semiconductors, solar and many others.

The use of a slurry necessitates a slurry recycling plant, which due to its cost is not feasible for cutting processes carried out by small to medium scale enterprises. Slurry-based processes also require ancillary systems such as chillers, temperature management systems, and pumps that are not only complex and costly but are also energy inefficient.

Although diamond wires are preferred due to their superior cutting action, they cannot normally be used as they clog with the semiconductor material. That will often require them to be regularly replaced, thereby making their use very expensive. Furthermore, the use of normal cutting wires can slow the cutting speed, and result in cuts that are inconsistent thereby providing less useful results. It also results in lower yield, more waste and low throughput. This may mean, for example, fewer useable wafers from a given ingot, and inconsistent thickness of the wafers. Wafers that are uneven in thickness may result in reduced or uneven quality of semiconductors.

SUMMARY OF THE INVENTION

According to a first exemplary aspect, there is provided a machine to be used in the cutting of a blank into individual items, the machine comprising a cutting station configured to receive a plurality of parallel cutting wires for cutting the blank, the cutting station comprising at least one container for receiving therein a liquid to allow the cutting of the blank to take place in the liquid.

As used herein, the term "cutting" in relation to a blank includes slicing, grinding or other such operations to reduce the blank into individual items.

As used herein, the term "blank" denotes any mass of material having a shape, which is relatively easy to handle and transport. Non-limiting examples include silicon or sapphire in the form of ingots or bars.

As used herein, the term "takes place in the liquid' in relation to cutting denotes that the areas of the blank being cut are immersed or submerged (i.e. under the level of the liquid in the container) during cutting. The blank as a whole need not be immersed or submerged throughout the cutting process. The applicant has found that by carrying out the cutting process in the liquid (as opposed to merely spraying a slurry over the wires), clogging of the wires is reduced. Also, heat resulting from the cutting process is more efficiently dissipated into the larger volume of liquid in the container. This reduces the energy demands in terms of the cooling requirements of the system, and represents an advancement in green technology in this area. The applicant has also found an unexpected advantage in that the finish of the individualised items is significantly improved, especially in the initial cut regions (typically the first 2mm of the cut), as compared to the conventional spray-based cutting process. This has been attributed to improved wetting of the cutting area in the present invention even at the start of the cutting process. In the conventional spray-based process, it has been found that the slurry does not enter the slots of the cuts in the early cutting stages due to surface tension and so the cuts in the early stages take place without the required presence of the slurry. This adversely affects the cut quality. In the present invention, the cutting takes place in the liquid. The abundance and pressure of the liquid on the submerged or immersed cutting area means sufficient liquid is present in the cutting area from the start of the cutting process.

As used herein, the term "liquid" denotes substances in a liquid state at room temperature, including water, oil or a solution, with or without additives such as coolants, lubricants and the like.

According to a second exemplary aspect, there is provided a machine to be used in the cutting of a blank into individual items, the machine comprising a cutting station configured to receive a plurality of parallel cutting wires for cutting the blank, the cutting station comprising at least one container for receiving therein a liquid, the at least one container having two spaced apart side walls, there being two spaced apart end walls joining ends of the side walls; each of the plurality of wires passing through an opening in the side walls in a non-fluid-tight manner to allow the liquid to pass through the opening during operation of the machine. According to a third exemplary aspect, there is provided a machine to be used in the cutting of a blank into individual items, the machine comprising a cutting station configured to receive a plurality of parallel cutting wires for cutting the blank, the cutting station comprising at least one container for receiving therein a liquid, the at least one container being configured to allow all cutting of the blank to take place in the liquid, with the liquid having a laminar flow in the at least one container.

According to a fourth exemplary aspect, there is provided a machine to be used in the cutting of a blank into individual items, the machine comprising a cutting station configured to receive a plurality of parallel cutting wires for cutting the blank, the cutting station comprising at least one container for receiving therein a liquid; and a carrier for holding the blank during the cutting process, the carrier being receivable in a support assembly comprising a plurality of rollers on which the carrier is able to move, the support assembly further comprising a locking mechanism configured to lock the carrier relative to the support assembly when the carrier is correctly placed relative to the cutting station.

According to a fifth exemplary aspect, there is provided a method to cut a blank into individual items, the method comprising:

(a) attaching the blank to a bottom of a carrier;

(b) engaging the carrier with a support assembly;

(c) moving the carrier with the blank longitudinally relative to the support assembly until the blank is directly above a cutting station;

(d) lowering the support assembly with the carrier and the blank until a bottom of the blank contacts a plurality of cutting wires and is below a top of a container containing a liquid; and

(e) cutting the blank into the individual items while at least a relevant portion of the wires is in the liquid in the container. For one or more of the above exemplary aspects, the machine may further comprise a wire feeder and a wire receiver, the wire feeder and the wire receiver being generally parallel and spaced apart. In this form, the machine may be able to operate in a forwards mode where the wire feeder supplies the plurality of cutting wires to the cutting station and the wire receiver receives the plurality of cutting wires from the cutting station, and also be able to operate in a reverse mode where the wire feeder is the wire receiver and the wire receiver is the wire feeder. This is advantageous as it allows the machine to operate in the forwards mode until all of the cutting wires spooled on the wire feeder have been spooled on the wire receiver, at which point the machine may seamlessly switch into reverse mode to continue cutting. This obviates the need to stop the machine and manually substitute the drums of the wire feeder and receiver, which necessitates a laborious and complicated rewiring of the cutting wires through the cutting station.

Each of the plurality of cutting wires may be a diamond wire.

The wires may be configured to be in the liquid at all times during the cutting process. Alternatively, the wires may be configured to not be in the liquid when contacted by the blank, the pressure of the blank forcing a relevant portion of the wires into the liquid for the cutting to take place in the liquid; the relevant portion being for at least the full width of the blank.

The at least one container may have two spaced apart and generally parallel side walls, there being two spaced apart and generally parallel end walls joining ends of the side walls; each of the plurality of wires may pass through an opening in the side walls in a non-fluid- tight manner such that the liquid can pass through the openings during operation of the machine. Each of the side walls may be double walled and may comprise an inner side wall and an outer side wall parallel to and spaced from the inner side wall to form a side wall gap therebetween; the flow of the liquid into the at least one container being via the side wall gap and over the top edge of the inner side wall. Each of the end walls may be double walled and may comprise an inner end wall and an outer end wall parallel to and spaced from the inner end wall to form an end wall gap therebetween; a partial flow of the liquid out of the container being over the upper edge of the inner end wall and via the end wall gap.

A rate of supply of the liquid may be equal to a sum of the liquid outflow through the openings and over the upper edges of the end wall. The opening is selected from: one opening for each wire, a plurality of openings each being for a group of wires, one opening in each of the side walls with all wires passing through that one opening and an opening for all wires defined by a separation between an upper portion and a lower portion of the container. The one opening in each of the side walls may be through each of the inner side walls and the outer side walls. The openings may be below the top edge of the inner side wall.

The machine may be configured such that, in use, the liquid has a laminar flow in the at least one container. A laminar flow is advantageous as it reduces turbulence in the cutting station, thus improving the quality and accuracy of the cutting process. The top edge of the inner side wall may be serrated or scalloped for this purpose. The inner side wall may be of a lower height than the outer side wall. The inner end wall may be of a lower height than the outer end wall. The upper edge of the inner end wall may be serrated or scalloped to maintain a laminar flow in the container.

The machine may further comprise a carrier for holding the blank during the cutting process. The carrier may be receivable in a support assembly comprising a plurality of rollers on which the carrier is able to move. The support assembly may further comprise a locking mechanism configured to lock the carrier relative to the support assembly when the carrier is correctly placed relative to the cutting station. The carrier may be substantially T-shaped and may have a flange with stepped side walls. The carrier may be supported by the support assembly and may be able to move longitudinally relative to the support assembly and may be able to have a small lateral relative movement relative to the support assembly. The support assembly may have side walls that are correspondingly-shaped to the side walls of the carrier. The rollers may project inwardly from the side walls of the support assembly at a lower end thereof. The rollers may engage under lowermost surfaces of the stepped side walls of the carrier. The locking mechanism may comprise a downwardly- angled end configured to engage under a correspondingly-angled upper portion of the side walls of the carrier to lift the lower surface of the side walls of the carrier off the rollers and to move the carrier laterally relative to the support assembly such that the opposite side wall of the carrier locks against its corresponding side wall of the support assembly. The use of a carrier and support assembly arrangement allows a consistent and accurate blank loading method. Operator error in loading the blank is accordingly reduced and the accuracy of the cutting process is accordingly improved.

The blank may be an ingot of a semiconductor or other material.

For the fifth exemplary aspect, at (d) the wires may be in the liquid. Alternatively, at (d) the wires may be slightly above the liquid and the support assembly continues to move downwardly at a controlled rate until the wires deform slightly under the applied pressure of the blanks such that the wires are in the liquid at least for the full width of the blanks. All cutting of the blank by the wires may take place in the liquid. The relevant portion of the wires may be in the liquid during all stages of the cutting action. The relevant portion may be that portion of the wires in a cutting station and being at least for the full width of the blank. As with the earlier exemplary aspects, the wires may be able to operate in a forwards and a reverse mode, and the wires may be diamond wires.

The longitudinal movement in (c) may be a rolling movement.

According to a sixth exemplary aspect, there is provided a machine to be used in the cutting of a blank into individual items, the machine comprising a container having an upper portion and a lower portion, the upper portion being configured to receive a liquid from a source and to flow the liquid into the lower portion, the lower portion being removable from the machine independently of the upper portion, and a cutting station configured to receive a plurality of parallel cutting wires, the plurality of parallel cutting wires extending between the upper portion and lower portion of the container during operation of the machine to allow the cutting of the blank to take place in the liquid in the lower portion of the container.

According to a seventh exemplary aspect, there is provided a machine to be used in the cutting of a blank into individual items, the machine comprising a container having an upper portion and a lower portion, the upper portion comprising two channels being generally parallel, spaced apart and not in liquid communication with each other, the channels being configured to receive a liquid from a source and to flow the liquid into the lower portion, and a cutting station configured to receive a plurality of parallel cutting wires to allow the cutting of the blank to take place in the liquid in the lower portion of the container.

According to an eighth exemplary aspect, there is provided a machine to be used in the cutting of a blank into individual items, the machine comprising a container having an upper portion and a lower portion, the upper portion being configured to receive a liquid from a source and to flow the liquid into the lower portion, a cutting station configured to receive a plurality of parallel cutting wires to allow the cutting of the blank to take place in the liquid in the lower portion of the container, and a height adjustment mechanism configured to adjust the distance between the lower portion of the container and the plurality of cutting wires.

For the sixth to eighth exemplary aspects, the machine may further comprise a carrier for holding the blank during the cutting process, the upper portion of the container and the carrier being movable relative to the lower portion of the container. The upper portion of the container and the carrier may be movable along a first axis (e.g. a Z-axis or vertical axis) towards and away from the lower portion of the container, and the lower portion of the container may be movable along a second axis (e.g. an X-axis or horizontal axis), the second axis being perpendicular to the first axis.

The upper portion of the container may include walls that have an edge that is serrated or scalloped, the serrated or scalloped edge being configured to allow liquid in the upper portion of the container to flow over the serrated or scalloped edge into the lower portion of the container. The serrated or scalloped edge promotes a laminar flow into the lower portion, thus reducing turbulence in the lower portion.

The upper portion of the container may comprise channels defined by side walls, and the ower portion of the container may be arranged below and between the channels in use. This ensures most, if not all, of the liquid overflowing the upper portion is received in the bwer portion.

The lower portion of the container may be arranged on a base that is slidable on guide rails. This is advantageous as it allows an operator to pull the lower portion out of the cutting station (e.g. for cleaning) without having to exert excessive force. The source may be a supply tank including an inlet, an outlet and an internal wall arranged between the inlet and outlet, the internal wall having a plurality of through holes configured to allow a liquid from the inlet to form a plurality of streams and to dissipate heat as the liquid passes through the plurality of through holes. This is advantageous as the liquid is able to be cooled without having to employ active cooling mechanisms, consequently reducing the energy demands of the system and making a positive contribution towards green technology.

The internal wall may be a plate arranged substantially parallel to a base of the supply tank.

The machine may further comprise a collection tank for containing liquid exiting the cutting station, the collection tank including one or more filters configured to minimise contaminants in the liquid exiting an outlet of the collection tank. In one non-limiting form, at least two filters are provided parallel to each other and defining a gap therebetween, the collection tank being configured to receive liquid from the cutting station in the gap, and to detect an overflow of liquid over the at least two filters. More filters (e.g. six filters as described later) may be provided if desired.

The machine may further comprise a height adjustment mechanism configured to adjust the distance between the lower portion of the container and the plurality of cutting wires. In one non-limiting form, the height adjustment mechanism may comprise one or more support pads on which the lower portion of the container is located, and to which one or more rollers are attached, the one or more support pads being movable towards and away from the plurality of cutting wires by the one or more rollers travelling along corresponding ramp portions. The ramp portions may be attached to a slidable plate, the slidable plate being configured to slide in response to rotation of a hand wheel. The height adjustment mechanism is advantageous because it not only allows an adjustment of the gap through which the cutting wires pass (thus allowing accurate orientation based on wire size or drum size) but also allows offsetting of any drop in cutting wire height as a result of the wires cutting into their drums after prolonged use (i.e. due to the wear taking place on the grooves on the drums).

The upper portion may comprise two channels that are parallel, spaced apart and not in liquid communication with each other, each channel having a separate inlet. This arrangement further reduces turbulence since liquid flowing in one channel is prevented from interacting with and thus agitating liquid in the other channel.

A plate may be provided in each of the two channels, the plate being generally parallel to and spaced apart from a base of the channels, the plate including a plurality of apertures. The provision of the plate further reduces turbulence since liquid entering the machine via the inlets has to pass through the plurality of apertures to fill the channels, which in turn produces a laminar flow in the channels.

The lower portion may be provided with concave external side walls. This is beneficial where cylindrical drums are provided for the wire feeder and wire receiver since it allows the drums to be placed close to the container, thus ensuring the cutting wires (which extend between the wire feeder and receiver) are taut and are able to make accurate cuts.

The lower portion may have one or more openings on its base, the one or more openings being configured to allow some of the liquid in the lower portion to flow out of the bottom of the lower portion. This is advantageous as it allows fine debris that are not captured by an inner basket to flow out of the lower portion, thus avoiding any adverse effects arising from the fine debris being in the vicinity of the cutting area and jeopardizing the cut quality. One or more angled surfaces may be provided on the base of the lower portion, the one or more angled surfaces being angled towards the one or more opening on the base. This improves the flow of liquid out of the openings and thus promotes the egress of fine debris that may otherwise adversely affect the accuracy of the cutting process.

The above features and advantages, along with other related features and advantages, will be readily apparent to skilled persons from the description below.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments of the invention will now be described with reference to the accompanying figures in which:

Figure 1 is a front perspective view from above of a first exemplary embodiment,

Figure 2 is a front view of the first exemplary embodiment of Figure 1 ,

Figure 3 is a front view of the carrier and support assembly of the first exemplary embodiment of Figures 1 and 2 and when in a first state,

Figure 4 is a view corresponding to Figure 3 when in a second state,

Figure 5 is a view corresponding to Figure 1 on an enlarged scale and in partial breakaway,

Figure 6 is a view corresponding to Figure 5 in further breakaway,

Figure 7 is a longitudinal cross-sectional view of the container of Figures 1 to 6,

Figure 8 is a lateral cross-sectional view of the container of Figures 1 to 7,

Figure 9 is a front view of the cutting machine at a first stage of the cutting process,

Figure 10 is a front view of the cutting machine at a second stage of the cutting process,

Figure 11 is a front view of the cutting machine at a third stage of the cutting process,

Figure 12 is a front view of the cutting machine at a fourth stage of the cutting process, Figure 13 is a front perspective view from above of a second exemplary embodiment in a closed state,

Figure 14 is a side view of the machine of Figure 13,

Figure 15 is a view corresponding to Figure 13 in an open state,

Figure 16 is a side view of the machine of Figure 15,

Figure 17 is a front perspective view from above of a height adjustment mechanism,

Figure 18 is a view corresponding to Figure 17 on an enlarged scale and in partial breakaway,

Figure 19A is a side view of the height adjustment mechanism in a low state, with an inset showing a detailed view of the height adjustment mechanism,

Figure 19B is a front perspective view from above of the height adjustment mechanism in the low state in partial breakaway,

Figure 2OA is a side view of the height adjustment mechanism in a high state, with an inset showing a detailed view of the height adjustment mechanism,

Figure 2OB is a front perspective view from above of the height adjustment mechanism in the high state in partial breakaway,

Figure 21 is a front perspective view from above of the container showing the inlets and channels of the upper portion,

Figure 22 is a view corresponding to Figure 21 with the inlet details and diffuser plates of the channels removed,

Figure 23 is a partial breakaway front perspective view of a channel of the upper portion including a diffuser plate,

Figure 24 is a front perspective view from the bottom of the second exemplary embodiment,

Figure 25 is a partial breakaway front perspective view from the bottom of the second sxemplary embodiment,

Figure 26 is a schematic cross-section view of the container of the second exemplary

9mbodiment, Figure 27 is a front perspective view from above of the collection tank,

Figure 28 is a front perspective view from above of the supply tank, and

Figure 29 is an exploded view of the cooling chamber of the supply tank of Figure 28.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

To first refer to Figures 1 and 2, there is shown a cutting machine 10 that has a carrier 12 For one or more blanks 14 (two as shown) of a material to be cut into a number of separate components. As shown the blanks 14 are of a silicon material to be cut into separate wafers for use in semiconductor fabrication. However, the invention is not limited to that use. The blank 14 is attached to the carrier 12 by an epoxy, adhesive, or the like, in a known manner. It is attached to the bottom surface 15 of the carrier 12 (see Figures 3 and 4).

The carrier 12 is mounted for longitudinal movement relative to a support assembly 16 until the blank is correctly located above a plurality of cutting wires 22 that form a wire web. The wires 22 are supplied to a cutting station 17 by a wire feeder 18 and are received by a wire receiver 20. As shown, both the wire feeder 18 and the wire receiver 20 are cylindrical drums. However, the invention is not so limited. Preferably, the cylindrical drums 18, 20 are of sufficient diameter that only the two drums 18, 20 are required and no idler drum is required. This will enable the return path for the wires 22 to be substantially parallel to the supply path for the wires 22.

The machine may operate in a forwards mode where the wires 22 are supplied to the cutting station 17 by the wire feeder 18 and are received from the cutting station by the wire receiver 20; and in a reverse mode where the wires 22 are supplied to the cutting station 17 by the wire receiver 20 (now acting as a wire feeder) and are received from the cutting station 17 by the wire feeder 18 (now acting as a wire receiver).

The wire feeder 18 and the wire receiver 20 may be of known construction and operation. They may be in accordance with the wire feeding/receiving system of the wire saw as available from Meyer Burger Technology AG of Grabenstrasse 25, 6340 Baar, Switzerland.

The cutting station 17 is at the upper end of a container 24 configured to hold a liquid of a cutting liquid of any suitable and known form, including water. The machine has a liquid supply and filtration system (not shown) of known construction.

An outer housing 26 may be used to house the machine 10 components.

For the sake of clarity only a small number of wires 22 are shown. There may be any suitable number of wires 22 with the number being determined by the number and thickness of the wafers required. In use there may be in excess of 1 ,000 wires 22. The wires 22 may be of any suitable, known form including, but not limited to, diamond wire.

As shown in Figures 3, 4 and 5, the carrier 12 is approximately T-shaped and has a flange 28 with stepped side walls 30. The carrier 12 is supported by the support assembly 16 and is able to move longitudinally relative to the support assembly 16. A small lateral relative movement is also enabled. The support assembly 16 has side walls 36 that are correspondingly-shaped to the side walls 30. To assist the longitudinal movement of the carrier 12 relative to the support assembly 16, the side walls 36 of the support assembly 16 have projecting inwardly therefrom at a lower end thereof a plurality of opposed rollers 34 that engage under the lowermost surfaces 32 of the stepped side walls 30 of the carrier 12 (Figure 3) so that the carrier 12 can roll on the rollers 34 when moving longitudinally relative to the support assembly 16. This will reduce the operator force required for such a movement compared to the sliding relative movement that has previously been required. To prevent unwanted movement of the carrier 12 such as during the cutting operation, the support assembly 16 has at least one locking mechanism 37 that, as shown, is a hydraulic ram 38. Other forms of locking mechanism may be used where necessary or desired. When the hydraulic ram 38 is operated its downwardly-angled end 39 engages under a correspondingly-angled upper portion 40 of the side walls 30 of the carrier 12 to lift the lower surface 32 off the rollers 34 and moves the carrier 12 laterally relative to the support assembly 16 such that the opposite side wall 30a of the carrier jams against its corresponding side wall 36a of the support assembly 16 (Figure 4). For this reason, it is preferred that the locking mechanisms 37 are all on one side 36b of the support assembly 16.

Figures 5 to 8 show the details of the container 24 in more detail. The container 24 is generally cuboid with a base 42, parallel side walls 44 and parallel end walls 46 joining the ends of the side walls 44. The side walls 44 are each double walled and have an inner side wall 44a and an outer side wall 44b forming a side wall gap 44c (i.e. side wall channel 44c) therebetween. The inner side wall 44a is of a lower height than the outer side wall 44b. The inner side wall 44a has a top edge 48a that is serrated or scalloped along its length. The outer side wall 44b has a top edge 48b that is plain or flat. The end walls 46 are each double walled and have an inner end wall 46a and an outer end wall 46b forming an end wall gap 46c (i.e. end wall channel 46c) therebetween. The inner end wall 46a is of a lower height than the outer end wall 46b. The inner end wall 46a has an upper edge 50a that is serrated or scalloped along its length. The outer end wall 46b has an upper edge 50b. It is preferred that the height of the inner end wall 46a is less than or equal to the height of the inner side wall 44a such that the top edge 48a is above or at least equal to the upper edge 50a. During operation, the liquid level in the container 24 will be defined by the height of the upper edge 50a.

Alternatively, the side walls 44 may be single walled for the lower portion, and double walled for the upper portion.

A liquid inlet 52 is provided for each side wall gap 44c adjacent the top of the side wall gap 44c so that the liquid can be input into the side wall gaps 44c. The liquid will fill the side wall gaps 44c and flow over the top edge 48a of the inner side walls 44a. The serrated or scalloped top 48a assists in providing a laminar flow of the liquid into and within the container 24. When the container 24 is filled, the liquid will flow over the upper edges 50a and into the end wall gaps 46c. The serrated upper edge 50a will assist in providing a laminar flow of the liquid out of, and also within, the container 24.

A liquid outlet 54 is provided through the outer end wall 46b and adjacent the bottom of each end wall gap 46c to enable the liquid flowing over the upper edge 50a to be recovered, filtered and recycled in a known manner. Alternatively, the liquid that passes over the upper edge 50a may be separately removed from the machine 10 and the outlets 54 may be for removing liquid directly from the lower regions of the container 24. This may aid in the removal of fine debris from the cutting action.

A removable basket or plate 56 may be fitted in the container 24 for collecting debris of the cutting action. The basket or plate 56 may have a large number of small holes 58.

Each of the wires 22 passes through an opening 60 in each of the side walls 44a and 44b. The opening 60 in the inner side wall 44a is located below the top edge 48a and, preferably, is below the upper edge 50a of the inner end walls 46a so that the wires 22 are in the liquid at all times during the cutting process. The opening 60 is such that, during operation, the liquid may be able to flow through the opening 60 and out of the container 24. This is acceptable provided the rate of supply of the liquid through the liquid inlets 52 is equal to the sum of the liquid outflow through: the openings 60 and over the upper edges 50a and/or through outlets 54. As the liquid will flow over the upper edges 50a only when the container 24 is full, this will allow the container 24 to fill. The liquid outlets 54 are for removing any liquid that passes over the upper edges 50a and/or for directly removing liquid from the container 24. There may be an opening 60 for each wire 22, a plurality of openings 60 each being for a group of wires 22, or one opening 60 in each of the inner side walls 44a and outer side walls 44b, all wires 22 passing through that one opening 60. If the side walls are single walled at their lower portion and double walled at their upper portion, the openings 60 may be in the single walled portion, or may be in the double-walled portion.

Figures 9 to 11 illustrate the process. After the blank 14 (in this case two ingots of a silicon material) are secured to the bottom of the carrier 12, the carrier 12 is engaged with the support assembly 16 and moved longitudinally relative to the support assembly 16 until the blank 14 is directly above the cutting station 17. The locking mechanism 37 is then engaged. The wires are then activated and move from the wire feeder 18 to the wire receiver 20 when in the forwards mode, and the reverse when in reverse mode (Figure 9). The support assembly 16 with the carrier 12 and the blank 14 are lowered until the bottom of the blanks 14 contact each of the wires 22 (Figure 10). At this stage the wires may be in the liquid, or may be slightly above the liquid. The support assembly 16 continues to move downwardly at a controlled rate until the wires deform slightly under the applied pressure of the blanks 14. If the wires were out of the liquid at the initial contact between the blanks 14 and the wires 22, the wires 22 will now be in the liquid at least for the full width of the blanks 14 (Figure 11). The downwards movement of the support assembly 16 with the carrier 12 and the blanks 14 continues at a controlled rate that matches the cutting speed of the wires 22 until the blanks 14 are cut completely through (Figure 12). All cutting of the blanks 14 by the wires 22 takes place in the liquid. The relevant portion of the wires 22 (that portion in the cutting station and being at least for the full width of the blanks) is in the liquid during all stages of the cutting action. Due to the epoxy or adhesive layer 13, the separated wafers will remain attached to the carrier 12. The support assembly 16 is then moved upwardly thus removing the separated wafers and the carrier 12 from the container 24. The separated wafers can then be removed in the normal manner.

A second exemplary embodiment of the invention will now be described with reference to Figures 13 to 16. The cutting machine 10 shown includes a container 24 having an upper portion 24a and a lower portion 24b. Although similar in appearance to the first exemplary embodiment, the container 24 in this embodiment comprises a lower portion 24b that is separable from the upper portion 24a.

During operation of the machine 10, a plurality of parallel cutting wires would extend between the upper portion 24a and the lower portion 24b (i.e. through a gap 61 defined by the distance between the upper portion 24a and the lower portion 24b - see Figure 14). The cutting wires have been omitted in the figures for clarity.

The upper portion 24a primarily includes two parallel and spaced apart channels 44c defined by gaps between side walls of the upper portion 24a. The lower portion 24b comprises a generally cuboid tank having concave external side walls, and is generally arranged below the two channels 44c of the upper portion 24a such that a substantial t/olume of the lower portion 24b is between the two channels 44c.

The upper portion 24a, along with the support assembly, carrier and blank to be cut, is xiovable in a Z-axis (i.e. vertically) toward and away from the lower portion 24b. The positioning of the upper portion 24a is determined by sensing the position of one or more surfaces 63 of the upper portion 24a. The upper portion 24a is also configured to receive, via inlets 52, liquid from a source and to flow the liquid into the lower portion 24b. In the embodiment shown, the inlets 52 are both on one side of the machine 10 for convenient connection to a source.

The lower portion 24b is configured to collect the liquid to allow the cutting of the blank to take place in the liquid. As explained earlier, the lower portion 24b collects the liquid and maintains the liquid at a height sufficient to substantially submerge a relevant length of the cutting wire in use. This ensures cutting can take place in the liquid and further improves cooling of the system since heat in the cutting wires is able to dissipate immediately into the liquid.

In this embodiment, the lower portion 24b is arranged on a container base 62 that is slidable in an X-axis (i.e. horizontally) in and out of the cutting station by virtue of rollers 64 on the sides of the container base 62 that are movable along parallel guide rails 66 that form part of a frame of the machine. Figures 13 and 14 show the position (i.e. a closed position) of the lower portion 24b during operation of the cutting machine 10, while Figures 15 and 16 show the position (i.e. an open position) of the lower portion 24b once pulled out of the cutting station. Stoppers 68 are provided adjacent the ends of the guide rails 66 to prevent the container base 62 from sliding out of the machine completely.

The second exemplary embodiment allows the lower portion 24b to be removable from the machine 10 independently of the upper portion 24a, which reduces the time and effort required to clean the lower portion 24b or to access the removable basket or plate in the lower portion 24b to remove debris collected from the cutting action. Specifically, when cleaning of the basket or plate is required, the cutting operation is stopped, and the upper portion 24a, the support assembly, the carrier and the blank, are moved upwardly away from the lower portion 24b. No removal of the cutting wires is required since the cutting wires are provided above the lower portion 24b, rather than through the lower portion 24b or the upper portion 24a. As a result, once the upper portion 24a and the support assembly, the carrier and the blank have been retracted upwardly, the lower portion 24b can be drawn out for cleaning whilst leaving the cutting wires on the wire feeder and receiver drums. By obviating the removal of the cutting wires, not only is the cleaning process made simpler but the likelihood of damaging the wires from repeated removal and re-installation is also significantly reduced, and a considerable amount of time is also consequently saved.

Referring now to Figures 17 and 18, a height adjustment mechanism for adjusting the height of the lower portion 24b relative to the cutting wires (and thus the distance between the lower portion 24b and the cutting wires) will be described. For the sake of clarity, the lower portion 24b of the container 24 has been omitted in the figures. Skilled persons will appreciate that the lower portion 24b will, in use, be placed on support pads 71. The height adjustment mechanism includes a hand wheel 70 that is attached to a shaft 72, which is connected to a slidable plate 78 via a nut 74 fixedly attached to the slidable plate 78. The slidable plate 78 is configured to translate the rotational movement of the hand wheel into linear movement. The slidable plate 78 is slidably attached to a base plate 79, and includes ramp portions 80 that each receives a roller 82 provided on one end of a support post 84. The opposite end of each of the support posts 84 slidably projects through a cover plate 73 and is attached to the support pads 71. Further support posts 84a are provided at corners of the cover plate 73. Each of the further support posts 84a is attached at one end to the base plate 79 via a spring 86, and extends through the cover plate 73 and attaches at an opposite end to a support pad 71 in a similar manner as the support posts 84. The provision of the springs 86 ensures all support pads 71 are biased towards the lowest position (by virtue of all support pads 71 being attached in use to a support plate 77 - see Figures 19B and 20B), which in turn ensures the rollers 82 have intimate contact with the ramp portions 80. In addition to the support plate 77, the mechanism as a whole is covered (e.g. with stainless steel plates) to avoid ingress of liquid during operation of the machine.

The operation of the height adjustment mechanism will now be described with reference to Figures 19A, 19B, 2OA and 2OB. Figures 19A and 19B show the height adjustment mechanism in its lowest position, while Figures 2OA and 2OB show the height adjustment mechanism in its highest position. Starting with the lowest position, rotation of the hand wheel 70 in a first direction results in the nut 74 urging the slidable plate 78 and thus the ramp portions 80 along the X-axis (i.e. horizontally), which urges the rollers 82 up the ramp portions 80, and which in turn pushes the corresponding support posts 84 and the lower portion 24b of the container 24, upwardly in the Z-axis (i.e. vertically). The resulting vertically-adjusted position is shown in Figures 2OA and 2OB. The position can be returned to that of Figures 19A and 19B by turning the hand wheel in a second direction opposite to the first direction, which urges the rollers 82 down the ramp portions 80. In the preferred embodiment, the ratio of hand wheel turn to vertical movement of the container is known to the operator. This can be achieved, for example, by providing a gear on the hand wheel such that one revolution of the hand wheel amounts to a predetermined vertical movement. For example, by using a 20-tooth gear that provides a 1 mm vertical adjustment for one revolution of the gear, an operator would be able to adjust the vertical height to an accuracy of 50 microns (representing the vertical adjustment for every tooth of the gear).

The height adjustment mechanism allows an operator not only to tailor the distance between the cutting wires and the liquid in the lower portion 24b of the container 24, but also provides a means by which cutting wire movement may be offset. In particular, it has been found that prolonged use of the cutting machine may result in the cutting wires cutting into their drums. This may in turn cause the cutting wires to drop relative to their initial height and introduce inaccuracies in the cutting process. Rather than unwinding the cutting wires and replacing or reorienting the drums, which is a time-consuming and complex process, the height adjustment mechanism can be used to drop the height of the lower portion of the container by a corresponding amount so that the relative position of the cutting wires and the container remains the same. It will be appreciated that the specific embodiment of the height adjustment mechanism shown is not limiting, and variants using a cam or the like mechanism may be used instead.

Figure 21 shows a further feature of the second exemplary embodiment of the present invention. As noted earlier, liquid from a source enters the cutting machine via inlets 52 (see Figure 13). In the present embodiment, each inlet 52 directs fluid into only one side wall gap or channel 44c. This reduces turbulence in the side wall channels 44c, which in turn reduces turbulence in the lower portion of the container 24b since the side wall channels 44c are configured so that liquid in the side wall channels 44c overflow into the lower portion 24b.

To further reduce turbulence, the embodiment includes a laminar plate 88 in each side wall channel 44c. The laminar plate 88 is a plate having an array of apertures configured to receive the liquid from the inlets 52 and allow the liquid to pass through the apertures to improve the laminar nature of the liquid. Referring to Figure 22, liquid from the inlets is first flowed into a lower portion of the side wall channels 44c. As shown in Figure 23, once the liquid fills the lower portion of the side wall channels 44c, it flows through the laminar plate 88, where it fills the remaining volume of the side wall channels 44c before flowing over the serrated/scalloped edges 48a into the lower portion 24b of the container.

In the exemplary embodiments, two side wall channels are provided that each allow liquid to overflow their inner serrated/scalloped edges. This is desirable as it allows the machine to operate efficiently in both a forwards mode and reverse mode. In particular, during operation in a forwards mode, the cutting wires move in a first direction across the cutting station and distribute the liquid overflowing the first side wall channel over the wire web. During operation in a reverse mode, the cutting wires move in a second direction and distribute the liquid overflowing the second side wall channel over the wire web.

Details of the container 24 will now be described with reference to Figure 24, which shows a bottom perspective view of the upper portion 24a and the lower portion 24b. The upper portion 24a includes attachment points 90 for moving the upper portion 24a along the Z- axis independently of the lower portion 24b, and location pins 63 for accurate positioning of the upper portion 24a in the Z-axis. The lower portion 24b includes diverging channels 94 on a front and rear surface thereof. The diverging channels 94 are configured to channel liquid overflowing the lower portion 24b to a collection tank. A splash panel 96 is overlapped on the diverging channels 94 on the front surface to prevent overflowing liquid from splashing the operator. The lower portion 24b also includes concave external side walls to allow a closer placement of the cylindrical drums of the wire feeder and wire receiver. A close placement of the drums is important to ensure the cutting wires are taut about the cutting station for cutting accuracy.

As shown in Figure 24 and more clearly in Figures 25 and 26, the bottom surface of the lower portion 24b includes openings or slits 98 to allow some of the liquid collected in the lower portion 24b to flow out to maintain the level of liquid in the lower portion 24b. The slits 98 also allow fine debris that pass through the basket 56 to exit the lower portion 24b. This arrangement is similar to the outlet 54 of the first exemplary embodiment and is desirable to prevent the fine debris from circulating in the liquid and adversely affecting the cutting process. In the form illustrated in Figure 25 and Figure 26, angled surfaces 100 are provided on the bottom surface of the lower portion 24b to form sloping pathways towards the slits 98 and to improve the flow towards the slits 98.

Referring now to Figures 27 to 29, the flow of the liquid to and from a source will now be described. Figure 27 shows the arrangement provided underneath the cutting machine. The arrangement includes a collection tank 102 that receives the liquid exiting the lower portion 24b. The collection tank 102 includes multiple filters 104a-f (having a filter size of 100μm, for example) that are arranged in parallel and configured first to receive the liquid in the gap 106 between the first and second filters 104a and 104b. Assuming these filters are not blocked, the collected liquid will pass through the filters and move towards the ends of the collection tank 102, where it is pumped out. If the first and second filters 104a and 104b are blocked, the liquid in the gap 106 will collect and rise until it overflows into gaps 108 and 110 defined by the separation between the first filter 104a and a third filter 104c, and the second filter 104b and a fourth filter 104d respectively. The process then repeats as before provided there is no blockage of the third and fourth filters 104c and 104d. If, however, the third and fourth filters 104c and 104d are blocked, the liquid once again collects in the gaps 108 and 110 and overflows into gaps 112 and 114 defined by the third filter 104c and a fifth filter 104e, and the fourth filter 104d and a sixth filter 104f respectively. The process then repeats as before provided there is no blockage of the fifth and sixth filters 104e and 104f. If, however, the fifth and sixth filters 104e and 104f are blocked, the liquid once again collects in the gaps and rises until it contacts sensors 116, triggering an alarm to have the filters cleaned.

Once the liquid is pumped out of the collection tank 102, in the exemplary embodiment, it is passed through further filters that are external to the collection tank 102. In a non-limiting example, two filters are used having filter sizes of 10μm and 3μm respectively. Once filtered, the liquid is flowed back to the source. Figure 28 shows the source tank 118, which stores the liquid to be flowed to the cutting machine and liquid received from the collection tank 102 via inlets 120. The source tank 118 is provided with a passive cooling chamber 122 that receives the liquid from the inlets 120. The cooling chamber 122, shown in detail in Figure 29, includes a diffuser plate 124 having an array of through holes or apertures. The diffuser plate 124 forms the base of the cooling chamber 122 and forms part of an internal wall of the source tank 118. In the form illustrated, the diffuser plate 124 is arranged substantially parallel to the base of the source tank 118. Liquid received in the cooling chamber 122 via an inlet 126 (only one is shown for clarity) is made to pass naturally through the apertures of the diffuser plate 124 and form multiple streams of liquid. In so doing, the liquid is cooled by convection. The cooled liquid exiting the apertures is then collected in the source tank 118, ready to be flowed to the cutting machine via outlet 128. Skilled persons will appreciate that the use of the diffuser plate 124 obviates the need for active cooling systems and thus reduces the power consumption and the cost of the cutting system as a whole.

Whilst the foregoing description has described exemplary embodiments, it will be understood by those skilled in the technology concerned that many variations in details of design, construction and/or operation may be made without departing from the present invention. For example, although the present invention has been described in relation to the production of wafers from silicon ingots, this is not limiting. Skilled persons will appreciate that the cutting machine and process of the invention described above may be used in any process requiring similar cutting such as solar cell cutting, for example. Similarly, while embodiments have been described where the lower portion of the container includes slits and so is 'lossy' in terms of its liquid retention, a 'lossless' lower portion may be provided where desired since excess liquid may still exit the lower portion by overflowing the edges of the lower portion. It will also be appreciated that the features described in relation to the second exemplary embodiment may be implemented in the first exemplary embodiment and vice versa. The above variations, for instance, are intended to be covered by the scope of the claims.