TW201331010A - Wafer cutting sacrificial substrate for use in wafer cutting - Google Patents

Abstract

The invention relates to a sacrificial substrate (1) having a mounting surface (2) for holding a piece of material (3), such as an ingot, brick or core, for cutting a plurality of wafers from the piece of material (3), wherein the sacrificial substrate (1) has an E-modulus smaller than 6000MPa, more preferably smaller than 5000MPa, most preferably smaller than 4000MPa. The invention relates to a method of making a plurality of wafers of a piece of material (3), such as an ingot, brick or core, comprising the steps of: mounting the piece of material (3) to a sacrificial substrate (1), preferably by gluing; mounting the sacrificial substrate (1) with the piece of material (3) in a cutting device; and cutting the piece of material (3) into a plurality of wafers.

Description

Sacrificial substrate for wafer cutting

The present invention relates to a wafer-cut sacrificial substrate (also referred to as "beam") for cutting from a brick or ingot (photovoltaic/semiconductor industry) or column (optical industry) to a majority or a majority of wafers .

In the following description, wafer cutting processing in the prior art will be described. The sawing device for cutting a wafer has a wire web formed between at least two wire guiding rolls. A block of material (ingot, brick or column) is lowered into the wire web, while the movement of the previous and subsequent rotations causes the wire to circulate, thereby performing a sawing action, thereby cutting the material block into a plurality of wafers. The same method is also used to cut one ingot into a plurality of bricks. Here, the number of wires is low and the wire extends between the majority of the pulleys. The sacrificial panels of the present invention are equally applicable to the wire saw (referred to as a brick or cutter, or Meyer Burger's "Brick Master"). The term wire saw used herein is any form of wire saw, and the bricks can have any shape. The cutting of the bricks is as disclosed in WO 2010/128011 A1, which is incorporated herein in its entirety by reference.

Polycrystalline ingots are cut into a number of bricks. In order to make it square, a (circular) single crystal ingot is placed on a holder. Now, like the line field illustrated in Figure 3 of WO 2010/128011 A1, the cross section of the circular ingot is made approximately square or any other desired form in the manner described above. The ingot is also cut into a plurality of blocks, thus giving the blocks The required length. In order to cut the tip of the single crystal, the crucible is removed.

Today, for wafer processing in semiconductor applications, solar cells, or light-emitting diodes, more and more fixed-grain is used for cutting. A cutting method using a abrasive particle suspended in a polishing liquid and transported by a metal wire to perform cutting becomes less common. In the fixed abrasive method, the abrasive particles are directly attached to the metal wire. The wire system can be a diamond wire.

These sawing technologies are used in the semiconductor, electronic components, optoelectronics and optics industries. Typical materials are gallium arsenide, germanium, polycrystalline or single crystal or monocrystalline germanium, indium phosphide, quartz, sapphire or other ceramic materials.

When a piece of material is cut, such as a brick, ingot or column, the piece of material is attached to a sacrificial plate. The sacrificial plate is then attached to a clamp attachment, which is typically made of metal. The clamp attachment is used to secure the assembly to the fixture of the sawing machine.

In the subsequent description, the function of the sacrificial substrate will be described in detail. As the wire guide rolls rotate, the bricks are pushed through the wire field, causing the wire saw to bend downward. As the depth of cut increases, the wire saw becomes a so-called "bow". Because of this arcuate shape, the (upper) edge of the block of material is cut before it is completely cut through the intermediate portion of the block of material. The purpose of the sacrificial substrate is to keep the jig attachment at a distance from the block of material so that it is not cut (and therefore not damaged). Therefore, the sacrificial substrate is a disposable portion. Once the wafers have been cut, the fixture attachment, the sacrificial substrate, and the wafers are removed from the sawing machine. In the next processing step, the individual wafers are suspended from the fixing component in a comb-like manner, and are separated from the sacrificial substrate and the component system. from. The term "fin" as used herein describes the structure formed in the sacrificial substrate (or "beam") when the wire saw portion saws the substrate. Today, fins have a thickness that approximates the thickness of the sawed wafers.

The sacrificial substrate may have various shapes depending on the shape of the material block. Ingots, bricks or columns can also have a variety of shapes and sizes. For example, the sacrificial substrate may have a rectangular shape or have a curved shape on one side for receiving a cylinder and the other side is flat. For sapphire, both forms of shape can occur. For semiconductors, the beam is mostly curved on one side; for photovoltaic applications, the sacrificial substrate is mostly rectangular.

Ethylene glycol and water based wafer processing: A cutting fluid is used during sawing. The cutting fluid has at least a cooling and lubricating function. When using diamond wire, consider two systems that are primarily used for wafer processing cutting fluids: a purely water-based cutting fluid that contains water and additives such as Synergy DWS500 (by Diamond Wire Materials Technology, US) The supplied cutting fluid, or a cutting fluid containing an organic fluid other than water, is known as a glycol-based cutting fluid such as Yumark® (available from Yushiro Manufacturing America Inc., US). The invention is related to both water based and ethylene glycol based processing methods and is associated with any other processing method. In fact, water-based processing has more requirements for the properties of the sacrificial substrate, mainly related to expansion and deformation.

Continuous wafer processing (sometimes) Circular machining: Compared to the wire used in wafer processing using grinding, the wire saw used in cutting is generally 400 km (km). In wafer processing using diamond wire, cutting The length of the wire saw used during the period is limited to 1-10km. The diamond wire has a longer life than the normal grinding line, so the length of the wire used is shorter. However, the processing is a pilgrim procedure in which a portion of the diamond wire web moves toward a lifting scroll, but the main portion of the wire used in the cutting remains on the wire, so Continue to use in subsequent cuts. Therefore, in order to function properly, the sacrificial substrate should not adversely affect the cutting energy of the diamond wire. Otherwise this will affect the cutting performance of the wire saw in subsequent cuts.

This is in contrast to a so-called single cut, which means that the line is used only in a single cut and updates the remaining portion of the line in the net before cutting the next ingot, brick or column. It has been demonstrated that the total amount of lines consumed in a single single cut is much higher than the continuous cut back to back. Back-to-back continuous cutting is more cost effective because it optimizes the life of the diamond line.

Other terms are stated below: the wire mesh is supported by a plurality of wire guiding rolls. Typically these rolls are coated with polyurethane and have a groove pattern for receiving the wire. The diamond strands are interlaced in the grooves to the equal line guide rolls. The spacing of the trenches (in other words, the distance over which the trench pattern itself repeats) determines the thickness of the wafer being diced by the diameter of the line it uses.

Line hopping and line pairing are disadvantages associated with the repeating wire pattern, both of which deviate from the thickness of the desired wafer. difference. When two wafers are glued together in the web, this is called a pair of wires. When the line is not in its groove, it is called a line jump.

The total thickness variation (abbreviated as TTV) is the difference between the minimum and maximum thickness of a wafer. Is a measure of cutting quality.

Edge defects can be damaged edges, cracked corners of the wafer, or irregular edges. The chip is a sheet-shaped edge defect on only one side of the wafer. Microcracks are another important defect that may be due to improper cutting or the use of improper bundles.

If even if a portion of the wire mesh has been used in a previous cut, the residual sawing capacity of the used wire is not excessively degraded, and the fixed abrasive wire can be continuously used in subsequent cutting, which is obvious. Reduce the cost of the fixed abrasive wafer processing method. The sawing ability can be measured by the case where the line is deformed in the cutting process (determining the shape of the "bow" of the line during cutting). Lines that lose sawing ability will be more deformed (and have a higher or more pronounced bow) than the new unused line.

At the end of the slicing process, to form the wafer, the sacrificial substrate is partially cut until all wafers are fully sliced to compensate for the effect of the bow due to the sawing process. The sacrificial substrate should be as inexpensive as possible and have no effect on the quality of the wafer slice.

In the prior art, the sacrificial substrate interacts with the wire, which is machined in such a way that the line deformation in the subsequent cut is a higher degree of deformation than the deformation at the end of the first cut. Therefore, the wafer quality obtained from the subsequent dicing is lower than the absence of interaction with the sacrificial substrate. according to As a result, its output will be lower as more wafers will be out of specification. And because the line is used more quickly, the risk of forming line cracks is also increased.

In the following description, the sacrificial substrate of the prior art is described. The sacrificial substrates currently used for grinding liquid crystal round processing are mainly made of glass. The advantage is not expensive. It also does not absorb moisture and has a thermal coefficient comparable to that of bismuth or sapphire, which is also geometrically and thermally stable in the general case observed in wafer processing. However, its disadvantage is that it has an adverse effect on the quality of the diamond wire. When the diamond line begins to cut into the glass sheet, the wire saw cannot remove the formed swarf from the sawing channel (i.e., the channel formed when the material is cut). Therefore, the quality of the wire saw is impaired, and if the movement of the work block through the net is not reduced, the force applied to the wire saw will be increased.

Other sacrificial substrates available on the market are made of synthetic materials, such as thermoplastics, thermosets or blends, most often based on epoxy resins and filled with various additives. material.

One of the currently available sacrificial substrates is DMT111GB (available from Diamond Wire Materials Technology, US); phenolic based substrates are relatively inexpensive compared to other synthetic solutions and are based on ethylene glycol. Good results in sawing. A disadvantage of such a bundle is that it is difficult to control the phenomenon of moisture and expansion in water-based wafer processing, such that the wafer may fall and/or be damaged from the sacrificial fixed plate.

Another alternative is the Valtron® 190 Clean Beam (available from Valtech Corp, US), a mineral-filled thermoset that has the advantage of geometric stability to form straight, non-deformable fins. The part between adjacent cutting lines). However, because of the interaction between the sacrificial substrate and the diamond line, the cutting performance of the diamond line is severely degraded in subsequent cuts. Therefore, more lines are consumed in subsequent cuts. Therefore, the processing cost is increased.

EP 2111960 A1 discloses a fixing plate having a hollow tube instead of a standard glass and a more expensive polymer plate, but which is made of a ceramic material, which is difficult for diamond wire cutting processing, and in early diamond lines Failure when cutting.

US2009199836A1 discloses a carbon nanotube-reinforced wire saw bundle for use in wire saw slicing in which an ingot is cut into a wafer. It is proposed - in addition to other physical properties of the wire saw bundle - to strengthen the Young's modulus of the bundle with conventional epoxy resins reinforced with carbon nanotubes (CNTs). However, a bundle having a strengthened Young's modulus has a reverse effect on the cutting properties of the wire saw and also has an adverse effect on cleaning the wire saw or wire guiding rolls. This has a reverse effect on the quality of the cut and can cause damage to the wafer.

WO200940109A1 discloses a method of cutting an ingot into a wafer using a wire saw device. The ingot is bonded to a spindle holder prior to cutting the ingot. In order to completely remove the glue from the ingot holder, and at the same time the glue remains on the cut wafer, the surface of the ingot holder has a (SiO)x layer.

DE 20 44 482 A1 discloses a method of having a large size (greater than 1 meter x 0.50 meter) ceramic plate. Prior to cutting, the ceramic plates are stacked one on another and filled with a solidified flowable material (polyurethane foam) between the ceramic plates. The material has a lower modulus of elasticity relative to the ceramic plate. The ceramic stack is cut using a device that cools the cutting wheel. DE2044482A1 is related to a completely different technical field. Moreover, the present invention is not related to the cutting of the board, but rather to cutting the ingot, brick or column to obtain the wafer.

US2011162504A1 discloses a multi-knife cutting machine for performing most of the cutting of rare earth magnetic bricks using a machine, in particular a jig for holding and holding the magnetic brick during a multi-knife cutting process with a machine. Therefore US2011162504A1 is also related to a completely different technical field.

The object of the present invention is to overcome the problems derived from prior art solutions and to provide a cost-effective sacrificial substrate for wafer dicing that does not adversely affect the sawing quality of the wire saw, Cleaning the wire saw or wire guide rolls adversely affects, is cost effective, forms high quality wafers and high throughput, does not harm the wafers, and is fully suitable for water-based or glycol-based cutting machining.

Compared to the prior art, the solution of the invention follows a completely different approach. In the following description, the principles of the present invention will be discussed.

In this field, for sacrificial substrates, the trend is toward a material that is more stable in thermal, geometric, and mechanical properties. All prior art solutions have attempted to provide a stiff, straight and stable fin in the sacrificial substrate during use in wafer processing. Therefore, a compact material having a very high Young's modulus is used. Mechanical stability is considered a fundamental requirement to maintain the integrity of the wafer mechanics and maintain high yields during wafer processing.

However, the sacrificial substrate according to the present invention is characterized by a large degree of geometric deformability and has a low Young's modulus, so that the applied force on the wafers is kept small, and even if it is dropped The wafer is not damaged at all.

The object of the present invention is achieved by a wafer-cut sacrificial substrate (also referred to as a wafer-cut beam) having a fixed surface for supporting a cluster of ingots, bricks or pillars. The selected block of material is cut from the block of material into a plurality of wafers, wherein the sacrificial substrate has a modulus of elasticity or Young's modulus of less than 6000 MPa, preferably less than 5000 MPa, according to ISO 178. The best system is less than 4000 MPa.

The use of a more elastic material as defined above has a beneficial effect on the life of the quality wire saw of the finished wafer, as will be described in more detail below.

The object of the present invention is also achieved by a wafer-cut sacrificial substrate made of a porous material. The porosity of the material having open and/or closed cells makes the sacrificial substrate relatively soft to the wire saw. There is also less material deposited on the wire saw and the wire guiding rolls (due to the influence of the holes).

In one embodiment, the wafer-cut sacrificial substrate has a porosity greater than 0.15 (or 15%), preferably greater than 0.30 (or 30%), and most preferred is greater than 0.40 (or 40%).

In a specific embodiment, the porous material is a foam, preferably a polymeric foam. It is a preferred embodiment because it is shown to be superior in performance and can be easily produced in a cost effective manner. Foam means any substance formed by means of capture, more precisely by trapping bubbles in solids. The foam may also be filled with a filler (i.e., another solid) to alter or support certain functional properties of the bundle, such as, for example, changing its coefficients, thermal properties, and the like.

The object of the present invention is also achieved by a wafer-cut sacrificial substrate made of a polymer base material having a water absorption of less than 2%, preferably less than 1.5%. The best system is less than 0.7%. Water absorption is a property of a material that is related to the ability of the material to absorb water due to diffusion. The water absorption of a material is determined under a specific measurement. The water content or water absorption rate is related to the mass of water absorbed in a material relative to the mass of the material sample. The unit of water absorption is milligrams (mg) or percentage (%). The measurement procedures and conditions are as specified in DIN 53495. Suction according to the application of the present invention The water rate is related to the measurement conditions in which the material sample is immersed in distilled water of 23 degrees Celsius for 24 hours to absorb water.

The object of the present invention is also achieved by a wafer cutting sacrificial substrate having a heat distortion temperature greater than 50 degrees Celsius, preferably greater than 60 degrees Celsius, and more preferably greater than 70 degrees Celsius. degree.

In a specific embodiment, the wafer-cut sacrificial substrate is made of a duroplast material.

In one embodiment, the wafer-cut sacrificial substrate is made of a foam such as a polymer foam, ceramic foam or metal foam.

In a specific embodiment, the wafer cutting sacrificial substrate is made of polyurethane

In one embodiment, the wafer-cut sacrificial substrate is made from a foamed polyurethane, and wherein preferably the foamed polyurethane has a water absorption of less than 0.7%.

Preferably, the wafer dicing sacrificial substrate has an attachment surface for attaching the wafer dicing sacrificial substrate to the cutting device (eg, to a fixture attachment or a sacrificial base of the cutting device) A material holder, wherein preferably the attachment surface - for the fixed surface - is on the opposite side of the sacrificial substrate. Alternatively, other surfaces of the sacrificial bundle can be used as the attachment surface.

The object of the present invention is also achieved by a method of fabricating a plurality of wafers from a block of material, wherein the block of material is constructed from ingots, bricks or columns. Selected by the cluster, the method comprises the steps of: fixing the ingot, brick or column to a wafer cutting sacrificial substrate by bonding; cutting the sacrificial substrate with the ingot, brick or column Fixed in a cutting device, wherein the cutting device is a wire saw; and the ingot, brick or column is cut into a plurality of wafers by moving the ingot, brick or column through the wire mesh of the wire saw The wafer dicing sacrificial substrate is the wafer dicing sacrificial substrate described in any one of the foregoing embodiments.

Preferably, the step of fixing the wafer cutting sacrificial substrate to a cutting device is performed by fixing the wafer cutting sacrificial substrate to a fixture attachment, and then attaching the fixture attachment to the cutting The way in which one of the devices is supported is achieved.

Preferably, the wafer dicing sacrificial substrate is attached to the two bricks.

Preferably, the wire mesh is formed by a diamond wire. The substrate of the present invention provides the diamond wire with maximum use and thus the lowest cost for the diamond wire wafer processing method.

These advantages and principles of the present invention are discussed in detail in the following description.

The sacrificial substrates according to the present invention have the advantage that they do not degrade the cutting performance of the wire saw (fixed grinding line, the wire processing method of the abrasive used in the polishing liquid), and subsequent cutting Wafers that are stable and meet TTV and saw mark specifications. Note that the diamond line may also be damaged at the end of the cut when cutting a bundle. Therefore some of the cuts may have been completed, but the work block must still be cut when the line may have passed the bundle and the next cycle in the web.

It is well known to those skilled in the art that the processing of the sawing process tends to cause the wafers to bunch together due to the capillary forces of the coolant.

The ideal conditions illustrated in Figure 2 were not observed in the actual case, and the ideal condition is that the wafers are not affected by capillary forces. In effect, the wafers are suspended to the fixture attachment and the sacrificial substrate after being cut, which is similar to that illustrated in FIG. Most of the wafers tend to get together because of the capillary force. Figure 8 shows a typical photo of this situation.

This can create a large amount of deformation of the wafers and stress the wafers, which can cause micro-cracks and chip or even wafer loss.

With the finite element model, we have completed a better understanding of the strength of the deformation and stresses that are formed on a single wafer under a particular force.

Therefore, we adopt the system model as shown in Fig. 13: a fully cut wafer has a thickness t, a length l and a width w; it is suspended to a bundle by adhesion. The beam is then cut to a specific depth h.

At the end of the process, when the line has been cut into the bundle, the calculation tells us that under the same deformation, the stress on the wafers suspended from the bundle with a lower Young's coefficient is compared It is lower when suspended to a bundle with a higher Young's modulus.

In order to describe this phenomenon in more detail, an example of both will be explained. For these examples, we use the following parameters: the Young's modulus of the germanium wafer (159000 MPa); wafer length (156 mm); wafer width (156 mm); wafer thickness (0.180 mm); adhesive thickness (0.300 mm); adhesive strength (14 MPa); height h (7 mm) cut into the bundle.

In Example 1, a bundle having a higher Young's modulus (Young's modulus of 12000 MPa) in the prior art was used. Figure 12 shows that the typical force F expected to be applied at the bottom of the wafer is 0.0342 Newtons (N), resulting in a wafer deformation Δd of 9.1 mm, and the tension σ formed on the wafer and the bonding interface is 10N/mm2.

In Example 2, a bundle having a Young's modulus of 6000 MPa according to the present invention was used. For applying the same force F to 0.0342N at the bottom of the wafer as shown in Fig. 12, the wafer deformation Δd is 14.8 mm, and the same tension is formed on the wafer and the bonding interface (σ is 10N/mm2).

The basic calculation for the above-described dimensional analysis using the finite element model yielded a deformation distance of Δd of 3.6 mm in the wafer end side direction at a force F of 0.0342 N. The end of the wafer is attached to a bundle.

This is only a basic example, and it is actually believed that the tension and deformation produced are varied over a wide range. However, the results of these calculations show that materials with lower Young's modulus are advantageous for variations in materials with higher Young's modulus because the beam will withstand more deformation and thus reduce the wafer due to capillary forces. The stress that is formed.

We therefore recommend the use of materials with a lower Young's modulus. In other preferred embodiments, it is shown that we should look for materials with relatively low water absorption to enhance the positive effect to avoid over-morphing of the fin geometry. The shape causes excessive shear stress on the wafers. It has been found that as long as the deformation due to expansion is limited, the fins (the fins produced on the substrate by the wire saw) are allowed to undergo a certain degree of geometric deformation.

The sacrificial substrate may have a Young's modulus of less than 6000 MPa (according to the standard of ISO 178); preferably a Young's modulus of less than 5000 MPa; and an optimum Young's modulus of less than 4000 MPa. The substrate used in conventional wafer processing using a polishing liquid is glass having a Young's modulus in the range of 50 GPa to 90 GPa. For glass-reinforced plastic materials, the Young's modulus is greater than 15 GPa; ceramic substrates generally have high coefficients, such as calcite (CaCO3 coefficient is 70 GPa to 90 GPa), so ceramic-filled plastic materials are usually strengthened. The tendency of the matrix plastic material to have a coefficient. There are already such reinforced epoxy sheets having a Young's modulus of 10,000 MPa or more in the field.

In order to avoid damage to the diamond wire, the present invention suggests the use of materials having a specific porosity while still providing sufficient geometric stability of the matrix.

The present invention provides the following advantages:

A low cost substrate solution compared to prior art such bundles (based on composites, ceramics, epoxy rubber, materials with or without filler).

The substrate of the present invention maximizes the use of the diamond wire and thus achieves the lowest cost for the diamond wire wafer processing method.

Since the material of the sacrificial substrate is softer than the materials of the prior art in the art, the diamond wire does not form a bow in the sacrificial plate. shape. This ensures that the cutting process in the sawing (that is, the time required for all the wires to completely leave the work block) is faster.

The wafers formed are mechanically stable, forming low-level chips and minimal micro-cracks. Thus, a high throughput thin wafer slice can be obtained with the substrate according to the present invention.

The material can be easily shaped into the desired shape and size (for sapphire examples, 2, 4, 6 inch columns can be formed), holes can be drilled, and the material can be easily softened Get other shapes.

The substrate is lightweight and therefore easy to handle and transport.

The substrates provided are fully suitable for water-based and/or glycol-based cutting processes.

Because of these circumstances, the sacrificial substrate of the present invention is a porous material (softer) than the substrate of the prior art (for example, glass), so that the wire saw can more easily enter the sacrificial substrate. Therefore, in the soft bonding layer, the risk of the wire saw sliding (or deforming) in the lateral direction is reduced, and the soft bonding layer is located between the sacrificial substrate and the working block. This positive effect allows for the use of more glue, which in turn reduces the transmission force between the sacrificial substrate and the wafers. The edge of the sacrificial plate has been cut away before the wire saw moves completely through the work block. Due to the effect of this depth penetration, the wire saw is effectively guided in the substrate. Therefore, the risk of lateral movement of the wire saw on the surface of the substrate is greatly reduced.

Another advantage of the present invention is described below: since the substrate relaxes the bow of the wire saw (i.e., there is no arcuate shape in the substrate), the substrate does not require the thickness of the substrate as in the prior art. Therefore less material can be used as a sacrificial substrate, which is more economical and ecologically friendly.

1 shows a cutting device 5 for cutting from a working block 3 into a plurality of wafers which are bonded to a wafer cutting sacrificial substrate 1. The wafer cutting sacrificial substrate 1 is fixed to a jig attachment 8 which is then joined to a holder 9 of the cutting device 5. A line 7, which forms a wire web, is supported and driven by a plurality of wire guiding rolls 6. In the cutting process, the work block 3 moves through the wire web.

FIG. 2 illustrates the comb-like structure of the plurality of wafers 4, and the wafers are suspended from the sacrificial substrate 1 after the cutting process.

Figure 3 illustrates that the saddle of the sacrificial substrate can vary depending on the shape of the work block 3. In the particular embodiment of Figure 3, the working block 3 is cylindrical and the sacrificial plate has a corresponding curved securing surface 2. Any other shape of the sacrificial substrate 1 is possible.

Figure 4 illustrates a test setup for testing the effectiveness of the sacrificial substrate material. The clamp attachment 8 is coupled to the cutting device 5, which loads an alternating sequence of the sacrificial substrate 1 and the work block 3 (brick). The details of these experiments will be described below:

To mimic back-to-back wafer processing in a single cut test (after the cut of the brick, ingot, or column load is completed, the net is not updated until the start of the cut to the new brick, ingot, or column load), Design an experiment called "Sandwich Test". Figure 4 outlines the test arrangement. In this test, a 20mm high single-brick 3 system was glued to a 12mm high sacrificial substrate 1 using Delo-Duopox RM855, and this was glued again to a 20mm high single-brick 3, and sequentially The sandwich structure in which the majority of the sacrificial substrate 1 and the plurality of single-branched bricks 3 are finally established is performed, so that the conversion to the substrate 1 and the substrate 1 to the crucible is three times (see Fig. 4).

The settings used in the above experiments are also advantageous in the general process.

All ten pieces were executed on the Meyer Burger DS264; the line speed was 15 m/s; the table speed was 0.9 mm/s; the line tension was 25 N, and a 5% water-based coolant was used. Synergy DWS500. The thread used was from the diamond line of Asahi Diamond Industrial, which was a 10-20 grid with a 0.12 mm core. The material used was a single crucible that was ground to 125 mm x 100 mm x 20 mm.

As the line moves through the sandwich structure, the line bow of the line is measured. (For the results illustrated in Figure 5, this is the use of the substrate of the present invention; for the results illustrated in Figure 6, it is the use of prior art Valtrom® 190 Clean Beam. )

For the sandwich test in which the sacrificial beam is currently invented, in this example it is a foamed polyurethane bundle that is located when the wire is cut to the sacrificial substrate 1 and returned to its beginning in the subsequent bracts. At the position of the end of the first slab 3, the wire saw deformation is reduced to almost zero. This process optimizes the life of the diamond line used and achieves the most cost-effective results.

In fact, its additional advantage includes the fact that the final step of the sawing process, that is, the cutting process, can be completed more quickly because of the "zero" bow shape in the sacrificial substrate 1.

The deformation of the substrate 1 (see Fig. 2) can be examined by examining the fins produced in the substrate 1 after de-bonding and separating the wafers 4. In general, it is believed that the fins should not be deformed until now (refer to Figure 7c), as this deformation will increase the risk of wafer damage, wafer loss, and thickness variations of the wafers. However, it can be confirmed by the present invention that it can allow certain deformations (refer to Fig. 7a).

Because of this deformation, we can expect some mechanical stress to be generated on the wafers. In general, we can expect that this perseverance is not expected because it may affect the mechanical consistency of the wafers. However, it has been found that if the sacrificial substrate is very elastic and has a low Young's modulus, it does not affect the wafers being sawed. The wafers are glued to the sacrificial substrate and the quality of the wafer is not adversely affected. The sacrificial substrate may have a coefficient of yang of less than 6000 MPa (according to the ISO 178 standard), preferably less than 5000 MPa, and most preferably less than 4000 MPa.

An important feature is the thickness distribution of the fins produced. The thickness of the fins is an indication that the fins expand due to the coolant system used. If the fins over-expand due to interaction with the cooling fluid, the risk of wafer loss and wafer damage is again increased. The measurement of the standard deviation of the fin thickness is performed on many materials. According to the prior art phenolic resin bundle DMT1111GB (Fig. 7b) material, it can be used well in an ethylene glycol based system, but forms excessive expansion in a water based system. The standard deviation of the petals is greater than 10 μm (Table 1). (According to the prior art) Valtron® 190 Clean Beam provides very good wafer quality in a single cut with very little distortion and very thickness variations. However, such a bundle (substrate) has an excessive requirement for the diamond wire. The substrate of the present invention has a significant deformation as shown in Figure 7a, and the standard deviation of the thickness of the fin is less than 10 μm (Table 1). The polymer used in a specific embodiment of the invention having a water absorption of less than 2%, preferably less than 1.5%, and most preferably less than 0.7% (based on DIN 53495, at room temperature) The water was absorbed in distilled water at 23 ° C for 24 hours. The plastic's resistance to water is primarily related to the chemical nature of the material, and in the case where the plastic contains a filler, this property is also related to the filler form. More hydrophilic materials generally absorb more material than hydrophobic materials. In general, the water absorption rate is measured by immersing a material of a specific mass in an increased mass after 24 hours of Celsius 23 hours of distilled water. This measurement is described in DIM Standard 54395.

Another important parameter is the contamination of the wire saw and the wire guiding rolls, which has a large impact on the life of the (diamond) wire.

During this slicing, the material removed by the wire saw must exit with the wire and desirably must be removed by the cleaning procedure in the cut.

A porous material has the advantage for a solid or filler material that less material is sawed and removed from the sawing channel (the groove formed in the material as the wire saw action). However, it has been observed that in water-based diamond wire wafer processing, this removal and cleaning is preferred because the substrate material tends to deposit in the sawing machine, particularly on the pulley and wire guide rolls. The program is extra complicated. This deposition will block the grooves that should guide the line to guide the rolls and pulleys, thus creating the risk of line jumps and line pairing, resulting in wafer thickness variations and poor wafer quality. In order to avoid this problem, the sacrificial substrate must be made of a material having the following properties, which are not deposited in The lines guide the rolls or any other location of the cutting machine, but can be cleaned/removed using the water-based cleaning system used.

Since most sacrificial substrates are typically made from a polymer matrix containing a filler, there are two possible sources of contamination: the filler and/or the matrix material. Most of the filler is added to a base rubber to make the material less expensive or to improve the properties of the material, such as a modified Young's modulus (as previously described). Moreover, both the (and the) filler and the matrix material may have a negative interaction with the diamond line. Therefore, the material selection and the density of the filler are very important to the substrate. It has now been found that the preferred sacrificial substrate according to the present invention has a filler content of less than 30% by weight; preferably less than 15% by weight; the most preferred is no filler.

In this application, the hardness of the filler has a property of Mohs hardness less than or equal to 2 (e.g., gypsum) in order not to damage the wire; the optimum is less than or equal to 1.5 (e.g., graphite).

The thermal stability of the material is another important condition for two reasons.

The first reason is that the typical temperature range (measured by an infrared camera) measured in water-based diamond wire wafer processing is approximately 40 degrees Celsius. For glycol-based processing, it is believed that higher temperatures (mostly 50 degrees Celsius) are conceivable. I can imagine higher temperatures in local areas, especially in the sawing channel. . Therefore, it is important that the bundle material remains dimensionally stable at higher temperatures. The heat distortion temperature is measured by a three-point bending test, wherein Sample heating is performed under a fixed bending load. According to ISO 75 (ISO 75 - Method B), the heat distortion temperature is the temperature at which a particular deformation is reached. Therefore, the thermal stability of the substrate, especially the heat distortion temperature thereof, should be greater than 50 degrees Celsius, preferably greater than 60 degrees Celsius, and even more preferably greater than 70 degrees Celsius, so as not to be produced in the cutting process. The heat is deformed.

The second reason is also because the deposition tendency of the polymer matrix has been confirmed. One reason for this deposition may be due to the heat generated in the sawing process. In particular, thermoplastics have proven to be very sensitive to this phenomenon. This is due to the thermal energy generated when the wire is cut into the sacrificial substrate, thereby softening the polymeric substrate, causing contaminated polymer to deposit on the wire. Therefore, thermosetting plastics are preferred.

Experimental proof of process conditions:

A continuous diamond wire sawing process is performed to demonstrate the use of the sacrificial substrate in a class process. Eight consecutive cuts were performed on the Meyer Burger DS271 using a Asahi diamond line in a frame of less than 48 hours. The Asahi diamond line was a 10-20 diamond grid of 0.12 mm core. The material used was a single 156 mm x 156 mm wafer, and the target was a wafer that was cut to a thickness of 180 μm. The sacrificial substrate is a polyurethane foam having a porosity of 50%, a Young's modulus of 900 MPa, a heat distortion temperature of 77 degrees Celsius, and a water absorption rate of 0.6%. The coolant was Synergy DWS500 at a concentration of 5% using Pall Corporation's inline membrane filtration system to reuse the coolant during the complete test sequence. In order to evaluate the impact of the beam on the quality of the wafer Ringing, showing the median total thickness variation of the plurality of wafers for each subsequent cut, relative to the median of the total thickness of the first cut (see Figure 10). The total thickness variation (TTV) of the first cut is minimal because it is the only cut that begins with the use of a completely new diamond net. In this second and all subsequent cutting steps, at least a portion of the wire web has been used in the previous cut. For these subsequent cuts, the increase in TTV is kept to a minimum and remains stable. In contrast, the same data was set for three consecutive cuts made using the DW111GB on a sacrificial substrate of the prior art in a water-based environment (Fig. 11). The sacrificial substrate is not stable and the subsequent cut formed shows that this will translate into a poor TTV result. The same experiment with the Valtrom® 190 Clean Beam (also using prior art substrates) has been eliminated because it poses a too high bow in the second cut and creates a risk of wafer cracks.

For the sacrificial substrate of the present invention, there are four mechanisms that have advantages:

1. Because of the low Young's modulus, the force applied to these wafers remains low

2. The substrate material does not contaminate the quality of the cutting line

3. The density of the sacrificial plate is small, making the wire saw easier to enter the substrate and avoiding "squeezing" on the surface of the substrate.

4. Because the bow is smaller, the bundle can be thinner

By connecting these observations and for different cooling fluids (for example, based on water with respect to glycol) and in the form of a wire (diamonds are cut relative to the immersion in the slurry with abrasives), the following can be understood. The specific embodiments and combinations are solutions of the invention that achieve the objectives of the invention.

A sacrificial substrate having a Young's modulus of less than 6000 MPa (million Pa), preferably less than 5000 MPa, and most preferably less than 4000 MPa.

A sacrificial substrate made of a porous material having a closed and/or open cell.

A sacrificial board made of a foam process (polymer foam such as polyurethane, polyisocyanate, polystyrene, polyolefin, polyvinyl chloride, epoxy compound, latex, siloxane, fluoropolymer, phenolic foam or composite) Foamed plastic (spheroid), or ceramic foam or metal foam).

The matrix can be used in both diamond lines (using lines with fixed abrasive particles) and cutting processes based on slurry.

Preferred material:

The preferred material is a polyurethane which has the advantage of being inexpensive and not deposited on the polyurethane coated wire guide rolls or pulleys. Therefore, a foamed polyurethane having a water absorption of less than 0.7% (DIN 53495) is the optimum material.

The polyurethane may be foamed, having a porosity greater than 0.15, preferably greater than 0.30, most preferably greater than 0.40; having a Young's modulus less than 6000 MPa (according to ISO 178), preferably less than 5000 MPa, preferably The system is less than 4000 MPa.

Porosity:

Any form of void space in a solid material is considered to be a void, that is, a closed and/or open cell. Porosity, or pore body The integral ratio is defined as xp = (d0 - dp) / d0, which is the difference between the density d0 of the solid material (when no pores are included) and the density dp of the porous material with respect to d0. The porous material may be a foam (polymer foam such as polyurethane, polyisocyanate, polystyrene, polyolefin, polyvinyl chloride, epoxy compound, latex, siloxane, fluoropolymer, phenolic foam) Or composite foamed plastic (spheroid), or ceramic foam or metal foam). Polymer-based sacrificial substrates for diamond wire wafer processing, preferably having a porosity greater than 0.15 (in percent; multiplied by 100%) or 15%, preferably greater than 0.30 or 30%, the best system is greater than 0.40 or 40%.

Water absorption:

The polymer substrate of the present invention may have a water absorption of less than 2% (according to DIN 53495, water absorption at 23 ° C for 23 hours at room temperature), preferably less than 1.5%, and the optimum system is less than 0.7%. This is a typical measurement for polymer materials. The glass does not absorb water. The solid epoxy rubber may have a water absorption of about 0.1% or even lower. While the logical trend of the prior art is to maintain a minimum water absorption of the substrate, we have found flexibility at the edge of the reference because the mechanical properties of the substrate (Young's modulus) can be compensated for by water absorption. Deformation, also because it is a porous material, the foam structure it contains generally has a high water absorption.

Mechanical strength:

The sacrificial substrate has a Young's modulus of less than 6000 MPa (ISO 178, for a block having a size of 80 mm x 10 mm x 4 mm The material is subjected to a short-term (Kurzzeit bending test) at room temperature of 23 degrees Celsius; preferably having a Young's modulus of less than 5000 MPa; and the most preferred having a Young's modulus of less than 4000 MPa. According to prior art conventional substrates used in wafer processing using a polishing fluid, glass generally has a Young's modulus in the range of 50-90 GPa (MPa). For glass reinforced plastics, the correlation report for Young's coefficient values is greater than 15 GPa. Ceramic substrates generally have a high Young's modulus, such as calcite (the range of CaCO3 is in the range of 70-90 GPa), while plastics made from the ceramics generally have a tendency to strengthen the matrix plastic material. It has been found in the prior art that such reinforced epoxy sheets have a Young's modulus of 10 GPa or more.

The heat distortion temperature ( http://www.matweb.com/reference/deflection-temperature.aspx ) should be greater than 50 degrees Celsius (ISO75), preferably greater than 60 degrees Celsius, and more preferably even greater than 70 degrees Celsius , so as not to be deformed by the heat generated in the cutting process. The deformation temperature is a measure of resistance to distortion of a material under known load at a gradually rising temperature. This deformation temperature is also referred to as "deformation temperature under load".

Thermoset plastics are the best materials for this particular embodiment.

The invention is not limited to the specific embodiments above. Any material that meets the specifications of the present invention can be used. The above specifications describing the specific embodiments may be used alone or in combination with other specific embodiments of the invention.

1‧‧‧ wafer cutting sacrificial substrate

2‧‧‧Fixed surface

3‧‧‧Material block

4‧‧‧ Wafer

5‧‧‧ Cutting device

6‧‧‧Line guide rolls

7‧‧‧ wire saw

8‧‧‧Clamp attachments

9‧‧‧Support

Other embodiments of the invention are indicated in the drawings and the scope of the related claims. The list of reference signs constitutes the present invention Reveal the content. The invention will be described in detail below by means of the drawings. In the drawings: Figure 1 illustrates a portion of a wire saw machine for cutting from a work block into a plurality of wafers, and Figure 2 is a schematic representation of the sacrificial substrate after the cutting process An ideal pattern of a plurality of wafers supported, FIG. 3 illustrates a sacrificial substrate having a curved fixed surface, FIG. 4 illustrates a sandwich assembly, and FIG. 5 illustrates the use of the sandwich assembly in accordance with the present invention. The program test results of the sacrificial substrate, FIG. 6 illustrates the results of the test of the sandwich assembly using a sacrificial substrate according to one of the prior art, and FIG. 7a illustrates the removal of the wafers of the substrate of the present invention. Fins, Figures 7b and 7c illustrate the fins of a prior art substrate after removal of the plurality of wafers, and Figure 8 illustrates the support of the sacrificial substrate after the cutting process The actual pattern of a plurality of wafers, FIG. 9 schematically shows a pattern of a plurality of wafers supported by the sacrificial substrate after the cutting process, and has a pattern due to the capillary force of the coolant. Expected wafer deformation, Figure 10 illustrates the use of the sacrificial substrate of the present invention A pattern relating to the number of subsequent test cuts and the total thickness variation (TTV) of the wafers, and FIG. 11 illustrates the use of a prior art sacrificial substrate for the relevant The number of subsequent test cuts dies the total thickness variation (TTV) pattern of the wafer, and FIG. 12 illustrates a deformed wafer suspended from a sacrificial substrate, and FIG. 13 illustrates the suspension on the sacrificial substrate. One single wafer.

1‧‧‧ wafer cutting sacrificial substrate

3‧‧‧Material block

6‧‧‧Line guide rolls

7‧‧‧ wire saw

8‧‧‧Clamp attachments

9‧‧‧Support

Claims (15)

A wafer-cut sacrificial substrate (1) having a fixed surface (2) for supporting an ingot, brick or column for cutting a plurality of wafers from the ingot, brick or column in a wire saw (4) Wherein the wafer-cut sacrificial substrate (1) has an Young's modulus (E-modulus) of less than 6000 megapascals (MPa), preferably less than 5000 MPa, and most preferably less than 4000 MPa. The wafer-cut sacrificial substrate of claim 1, wherein the wafer-cut sacrificial substrate (1) is made of a porous material. A wafer-cut sacrificial substrate according to claim 2, wherein the wafer is sacrificed. The substrate (1) has a porosity greater than 0.15 (or 15%), preferably greater than 0.30 (or 30%). The best system is greater than 0.40 (or 40%). A wafer-cut sacrificial substrate according to claim 2 or 3, wherein the porous material is a foam, preferably a polymer foam. A wafer-cut sacrificial substrate according to any one of the preceding claims, wherein the wafer-cut sacrificial substrate (1) is made of a polymer base material having a water absorption of less than 2%, preferably The system is less than 1.5%, and the optimum system is less than 0.7% (based on DIN 53495, water is absorbed in distilled water at 23 degrees Celsius for 24 hours). A wafer dicing sacrificial substrate according to any one of the preceding claims, wherein the wafer dicing sacrificial substrate (1) has a heat distortion temperature greater than 50 degrees Celsius, preferably greater than 60 degrees Celsius, more preferably The system is greater than 70 degrees Celsius. A wafer-cut sacrificial substrate according to any one of the preceding claims, wherein the wafer-cut sacrificial substrate (1) is made of a duroplast material. A wafer-cut sacrificial substrate according to any one of the preceding claims, wherein the wafer-cut sacrificial substrate (1) is made of or contains a foam, such as a polymer foam, ceramic Foam or metal foam. A wafer-cut sacrificial substrate according to any one of the preceding claims, wherein the wafer-cut sacrificial substrate (1) is made of or contains a polyurethane. A wafer-cut sacrificial substrate according to any one of the preceding claims, wherein the wafer-cut sacrificial substrate (1) is made of a foamed polyurethane, and wherein the foamed polyurethane is preferably A water absorption of less than 2%, preferably less than 0.7%. A wafer-cut sacrificial substrate according to any one of the preceding claims, wherein the wafer-cut sacrificial substrate (1) is made of a foamed polyurethane, and wherein the foamed polyurethane is preferably Water absorption greater than 0.1%. A method for manufacturing a plurality of wafers of ingots, bricks or columns, the method comprising the steps of: fixing the ingot, brick or column to a wafer to cut a sacrificial substrate (1); The wafer cutting sacrificial substrate (1) of the ingot, brick or column is fixed in a cutting device (5), wherein the cutting device (5) is a wire saw; And cutting the ingot, brick or column into a plurality of wafers by moving the ingot, brick or column through the wire mesh of the wire saw, wherein the wafer cutting the sacrificial substrate (1) is the aforementioned application Any of the patented wafer cutting sacrificial substrates. The method of claim 12, wherein the step of fixing the wafer cutting sacrificial substrate (1) to a cutting device (5) is performed by fixing the wafer cutting sacrificial substrate (1) to a The clamp attachment (8) is then achieved by attaching the clamp attachment to one of the support portions (9) of the cutting device (5). The method of claim 12, wherein the wafer cutting sacrificial substrate (1) is attached to the two bricks (3). The method of any one of claims 12 to 14, wherein the wire mesh is formed by a diamond wire.