TWI494981B - Modified microgrinding process - Google Patents

Description

Improved micro-grinding method Cross-reference to related applications

The present application claims priority to Rizzuto et al., entitled "Improved Grinding Method", U.S. Application Serial No. 61/707,528, filed on Sep. The assignee will be hereby incorporated by reference in its entirety.

The present disclosure generally relates to semiconductor substrates, and in particular to sapphire substrates and methods of making such substrates.

In many types of manufacturing, including, for example, manufacturing sapphire substrates for use in LED production, grinding, polishing, or polishing a substrate such that its two major surfaces (faces) meet flatness, smoothness, or Some of the lowest levels of both are common. Generally, milling can be defined as the rapid removal of material by using a relatively coarse abrasive (>40 μm) (typically in the form of a polishing pad or disk) to reduce it to a suitable size or to remove from the surface. Big irregularities. The term "fine grinding" is generally used to mean the removal of material using free abrasive particles such as an abrasive slurry. Finally, the polishing system uses fine (< The 3 micron) abrasive particles remove material to create a scratch-free, mirror-like surface. All of these material removal methods can utilize a wide variety of abrasive materials such as abrasive slurries or fixed abrasive pads or discs, and in practice the boundaries between such different categories tend to be blurred. Collectively, all such methods may be referred to herein collectively as "grinding methods."

One example of a wafer or substrate processing tool is a typical double sided lapping machine 100, shown schematically in FIG. Such a tool can include two superposed platens or lapping plates 102 disposed above or below a substrate 104, respectively, such that the opposing surfaces of the substrate can be processed simultaneously. An abrasive slurry, typically containing abrasive particles 106 in the range of 5 microns to 180 microns, is applied directly to the lapping plates. As shown in FIG. 2, the double-sided lapping machine 100 includes a plurality of carriers 202, each of which holds a plurality of substrates or wafers 204. Each lapping plate may have an inner ring gear 206 surrounding the outer circumference of the plate and an inner sun gear 208. Each of the carriers may also have a toothed outer circumference 210 that engages the inner and outer gears. The internal gears (as indicated by arrow 212) and the external gears (as indicated by arrow 214) are rotated in opposite directions to cause each carrier to surround the axis of each carrier (as indicated by arrow 216) and surround the fine The axis of the plate (as indicated by arrow 218) is rotated. The resulting relative motion between the rotating carrier and the lapping plate forms a cycloid curve similar to the operation of the planet, such as the planets rotating on their own axes while traveling around the sun. This rotation in the presence of the abrasive slurry grinds off the material on the two major surfaces of the substrates.

Single-sided lapping machines are also known, but such machines only process one side of the substrates at a time. Moreover, similar planetary double-sided grinders are sometimes used Use different types of fixed abrasives or pads to remove material from the wafer or substrate.

Typically, a method of making a suitably flat substrate (such as a wafer or a sapphire wafer) involves a number of grinding, fine grinding, or polishing steps, regardless of the type of method or abrasive material used. For example, when a double sided grinder is used, the substrate is initially treated with a coarse fixed abrasive to quickly remove excess material and the worst surface damage caused by sawing the substrates from an ingot. Depending on the application, the first coarse grinding step can then be one or more fine grinding steps to produce a suitably smooth and flat surface. Fine grinding can then be a polishing step to create a very smooth mirror on the substrate. Often, the smoothest surface is only required on one side of the substrate. On other surfaces, a relatively rough surface would be acceptable or even desirable. However, a more elaborate grinding step is required to prepare this surface for polishing. Since the different grinding steps are performed sequentially, when double-sided grinding is used, the fine grinding steps are applied to both facets anyway. This leads to unnecessary costs in terms of time and extra wear and tear on materials and equipment.

Thus, an improved method of substrate material removal would be desirable.

The embodiments described herein are applicable to the preparation (processing) of any hard substrate, such as an oriented single crystal substrate, by grinding a substrate wafer using an abrasive such that the two major surfaces of the substrate satisfy the flatness Smoothness or both Some minimum levels. In a specific embodiment, a coarser abrasive is used to grind one major surface of the wafer while a thinner abrasive is used to simultaneously polish the other major surface of the wafer. As a result, a single grinding step can produce a wafer having opposing surfaces of different surface roughness. This allows the coarser abrasive to be used for preferential material removal to thin the wafer, while the fine abrasive produces a sufficiently smooth surface for many uses or for further polishing - thereby eliminating or reducing for prior art The need for a typical second downstream fine polishing step. Particular embodiments can be used with a wide variety of substrates, including sapphire, tantalum carbide, and gallium nitride single crystal structures grown by different techniques.

The above features and technical advantages of the specific embodiments have been described broadly, and the following detailed description may be better understood. Additional features and advantages of the embodiments are described below. It will be appreciated by those skilled in the art that the present invention may be readily utilized as a basis for modification or design of other structures for the same purpose as the embodiments described herein. Those skilled in the art should also appreciate that such equivalent constructions do not depart from the scope of the invention as set forth in the appended claims.

100, 300‧‧ ‧ double-sided lapping machine

102‧‧‧ platen or lapping plate

104, 204, 304‧‧‧ substrates

106‧‧‧Abrasive particles

202, 301‧‧‧ carrier

206‧‧‧ Inner ring gear

208‧‧‧Internal sun gear

210‧‧‧With tooth outer circumference

212‧‧‧Internal gear

214‧‧‧External gear

216‧‧‧Axis of the carrier

218‧‧‧ axis of the lapping plate

302, 303‧‧‧ grinding plate

308, 310‧‧‧ abrasive plates

402‧‧‧Supply pipeline

404‧‧‧Return line

406‧‧‧ coolant storage tank

407‧‧‧ centrifugal filtration

408‧‧‧ cartridge filter

The disclosure may be better understood by reference to the appended drawings, and the <RTIgt;

Figure 1 is a schematic illustration of a prior art double side lapping machine.

Figure 2 is a diagram showing the lower lapping plate and wafer carrier of the double-sided lapping machine of Figure 1. Schematic diagram.

3 is a cross-sectional view of a double-sided lapping machine in accordance with an embodiment.

4 is a schematic illustration of a slurry filtration system in accordance with an embodiment.

Figure 5 is a photograph of a double-sided lapping machine suitable for implementing the embodiment.

The drawings are not intended to be drawn to scale. In the figures, each identical or nearly identical component that is described in the different figures is represented by a similar numeral. For the sake of clarity, not every component is labeled in every figure.

The invention can be applied to the preparation (processing) of a substrate, such as an oriented single crystal substrate, by grinding and polishing a substrate wafer using a fixed abrasive so that the two main surfaces of the substrate satisfy flatness and smoothness. Degree or some minimum level of both. The specific embodiments as described herein can be used in a wide variety of substrates, including sapphire, tantalum carbide, and gallium nitride single crystal structures grown by different techniques.

All technical and scientific terms used herein have the same meaning as understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. The materials, methods, and examples are illustrative only and are not intended to be limiting. Many of the details regarding specific materials and processing behaviors are conventional and can be found in textbooks and other sources within the art of crystal formation and processing, to the extent not described herein.

Abrasives can generally be classified as free or loose abrasives as well as fixed abrasives. Loose abrasives are generally in the form of powder or particulate abrasive particles or sand in a liquid medium that forms a suspension (often referred to as a slurry). Gravel. The fixed abrasive utilizes abrasive grit in a material matrix that holds the opposing locations of the abrasive grits relative to each other. The fixed abrasive generally includes a coated abrasive such as sandpaper, bonded abrasive or the like. In bonded abrasives, the abrasive grit is fixed in positions opposite each other by using a matrix material in which the grit is distributed. The specific embodiments described herein utilize a fixed abrasive component in the form of a coated or bonded abrasive. Loose Abrasives and Fixed Abrasives "Micro-grinding" (also known as grinding with fine grinding kinematics, grinding with planetary kinematics, and fixed abrasive grinding) for single or polycrystalline materials (eg Batch processing operations of sapphire and tantalum carbide, ceramics, glass, metal components, etc.).

Typically, in order to form a substrate suitable for use as a substrate for a semiconductor device, in particular, a light-emitting diode/laser diode (LED/LD) application, the method begins with a bulk of material, The final processed substrate will be formed from the bulk material. A prior art method of forming a sapphire substrate suitable for LED/LD applications is described in "Sapphire substrates and methods of making same" by Tanikella et al., U.S. Patent No. 8,197,303. The present invention is hereby incorporated by reference in its entirety in its entirety in its entirety in the the the the the the the the the the

For sapphire substrates, the method can be initiated by forming an ingot or ribbon of single crystal sapphire. As will be appreciated, the sapphire can be formed into a blank, ingot or ribbon of any size or shape suitable for use as a substrate for a semiconductor device, in particular, an LED/LD application. Thus, a common shape is an ingot having a substantially cylindrical profile. For a ribbon, a common shape is a piece of wood. Use techniques such as the Czochralski Method), Edge-Defined Film Fed Growth (EFG), or Kyropoulos Method or other techniques, depending on the desired size and shape of the ingot or ribbon, and the crystal The orientation can complete the formation of single crystal sapphire.

After forming the single crystal sapphire, the ingot or blank may be sawed to slice the sapphire and form a plurality of wafers. The wire sawing of the sapphire ingot provides a plurality of unfinished sapphire wafers. Typically, the duration of the wire sawing process can vary from about a few hours, such as from about 2.0 hours to about 3.0 hours. In general, the desired thickness of the unfinished sapphire is from 1.0 mm to 10 mm. The wire sawing can be performed by using one or more fixed abrasive wire elements, such as an array of wires plated or coated with abrasive particles. An example of such a technique is a non-wound type wire sawing, such as FAST (Fixed Abrasive Slicing) supplied by Crystal Systems Inc. of Salem, Mass. ). Another example is a spool-to-spool wire sawing system. In the case of a single crystal raw material produced by the EFG method, typically in the form of a strip or sheet, the wire sawing process may not be necessary, and a cored-out (formed) wafer A grinding step can be carried out directly.

After forming a plurality of sapphire wafers by sawing, the surfaces of the unfinished sapphire wafers can be processed. Typically, the two major opposing surfaces of the unfinished sapphire wafers are subjected to grinding or fine grinding to improve the surface finish. Conventional rough grinding processes involve grinding two major surfaces of an unfinished sapphire substrate, for example using double-sided grinding or fine grinding. Typically, the coarse grinding process removes the foot at a reasonably high material removal rate. A sufficient amount of material to eliminate major surface irregularities caused by sawing by the wire saw. Thus, the rough grinding process typically removes at least 30 microns to 50 microns of material from the major surfaces (faces) of the unfinished sapphire wafers.

When a fixed abrasive is used, the coarse abrasive particles may comprise conventional abrasive particles, such as crystalline or ceramic materials, including alumina, ceria, strontium carbide, zirconia-alumina, another suitable abrasive, or Any combination of them. Additionally or alternatively, the coarse abrasive particles can include superabrasive particles including diamond, cubic boron nitride, or mixtures thereof. The coarse abrasive particles may have an average particle diameter of, for example, 60 to 300 μm. For bonded abrasives, the bonded material matrix can comprise a metal or metal alloy. A suitable metal includes iron, aluminum, titanium, bronze, nickel, silver, zirconium, alloys thereof or the like. Examples of specific grinding wheels include those described in US 6,102, 789, US 6,093, 092, and US 6, 019, 668, the entire disclosure of each of which is incorporated herein by reference.

The typical rough grinding process includes providing an unfinished sapphire wafer on a holder and rotating the sapphire wafer relative to a coarse abrasive surface. A double-sided grinder can be used, similar to the double-sided lapping machine shown in Figures 1 to 2. By way of example, the abrasive plates can be rotated at a speed of 60 rpm to 500 rpm. Typically, a liquid coolant or slurry is also used. After rough polishing, the sapphire wafer has an average surface typically 0.2 micrometers to 1 micrometer roughness R _a.

Once the coarse grinding has been completed, the sapphire wafers can be subjected to a fine grinding step to produce a smoother surface. This fine grinding step removes less material from the surface of the substrate, typically from 10 microns to 15 microns.

The fine abrasive particles may be the same general materials as the coarse abrasive particles and the same type of bonding material may be used. Of course, the difference is that the fine abrasive particles are smaller than the coarse abrasive particles. For example, the fine abrasive particles may have an average particle diameter of from 2 micrometers to 75 micrometers. Typically, the difference in average particle size between the coarsened abrasive and the finely fixed abrasive is at least 20 microns.

A double-sided grinder, similar to that shown in Figures 1 through 2, can be used with a bonded abrasive for fine grinding or polishing. By way of example, the abrasive plates can be rotated at a speed of 60 rpm to 1000 rpm. Typically, a liquid coolant or slurry is also used. After fine grinding the sapphire wafers typically have an average surface of about 0.10 microns to 1.0 microns roughness R _a.

After fine grinding, the sapphire wafers can be subjected to a stress relief treatment such as those disclosed in EP 0 221 454 B1. As described, stress relief can be performed by etching or annealing. Annealing can be carried out at temperatures above 1000 ° C for several hours.

After the fine grinding step, the sapphire wafers can be subjected to a polishing step to produce an even smoother surface. This polishing step removes even less material from the surface of the substrate, typically from 1 micron to 4 microns. This polishing step typically employs an abrasive slurry having abrasive particles having an average particle size of less than 1 micrometer, typically less than 200 nanometers. A particularly useful loose abrasive for use in such polishing processes is alumina, such as gamma-alumina in polycrystalline or single crystal form.

Typically, polishing is performed on only one surface, as opposed to the above-described grinding step which typically involves grinding the two major surfaces of the unfinished sapphire wafers. After polishing, the sapphire wafer surface typically has an average of approximately 10 angstroms to 400 angstroms (0.001 micrometers to 0.04 micrometers) roughness R _a.

Significantly, in the prior art, at least two separate grinding steps (one thick and one fine) were required prior to final polishing. However, for many applications, only one rough grinding step will be required on one surface, while the other surface requires at least an additional fine grinding step followed by polishing. In the prior art, the substrate processing operation is designed such that the grinding process performed on the top surface of the component is the same as those performed on the bottom surface. Thus, the final surface finish or texture on the top or bottom surface is the same (before a final polishing step, if any). Some substrates, such as C-plane sapphire or single crystal SiC used in LED fabrication, require a subsequent polishing step to improve surface quality on only one side of the wafer.

Embodiments as described herein may utilize a novel micro-grinding method as an alternative to the conventional fine grinding method for any hard substrate, such as the finishing of oriented single crystals. In micro-grinding, the abrasive slurry used in the fine grinding is replaced with a fixed abrasive product. Micro-grinding using bonded fixed abrasives provides a number of advantages over the use of abrasive slurries, most notably the material removal rate can be achieved by applying a higher load (pressure) between the abrasive and the substrate. Substantially increased. Replacing the abrasive slurry with the fixed abrasive disposed on the working surface of the abrasive plates also reduces maintenance costs and associated unproductive time associated with the necessary degree of trimming the plates to flatness and coplanarity. Micro-grinding using bonded fixed abrasives will also result in less subsurface damage (when optimizing the instruction order) than fine grinding using an abrasive slurry.

The design of at least one of the fixed abrasive plates or wheels for use in the micro-grinding method is improved to produce opposing substrates having different qualities (smoothness, subsurface damage, texture, etc.) in accordance with the specific embodiments described herein. The surface, such that the need for the second downstream fine grinding process can be eliminated or reduced. In some instances, the need for a final polishing step can also be eliminated or at least greatly reduced. In the case of a sapphire wafer to be used as a substrate in LED production, for example, the top plate or wheel used in the micro-polishing method preferably uses a finer abrasive grit than the bottom plate to allow for a single operation The desired surface finish on each side of the wafer is achieved, or nearly achieved. In some applications, a downstream fine grinding process will still be required, but the need for such a fine grinding process can be substantially reduced, which is significant because such processes are time consuming and expensive.

The specific embodiment as described herein utilizes a double side grinding with planetary kinematics, using a grinder similar to the double side lapping machine of Figures 1 and 2. The abrasive slurry typically used in fine grinding is replaced by two fixed abrasive plates or wheels that are mounted on the upper and lower coaxial polishing plates. The abrasive particles in the bonded abrasive plates can include diamond, cubic boron nitride, tantalum carbide, alumina, zirconia, another suitable abrasive material, or any combination thereof. The abrasive particles can also have different regular or irregular shapes (circles, squares, hexagons, etc.) and dimensions. The abrasive particles are bonded together in a resin, vitreous or metal matrix to form a rigid substrate or sheet for the micro-polishing process.

3 is a cross-sectional view of a double sided lapping machine 300 in accordance with an embodiment. Prior art fine grinding method as described above, to be processed The substrate 304 is preferably held in a carrier 301 which is disposed between two polishing plates 302, 303 on which the fixed abrasive plates 308 are mounted. 310. Having the abrasive plates together apply a predetermined pressure to the substrates while rotating the plates, carriers, substrates, or any combination thereof, thereby planarizing, polishing, thinning, or Or a combination of them. Preferably, the two abrasive plates each have a fixed abrasive (having abrasive particles of different sizes). In other words, one abrasive plate has an abrasive that is coarser than the abrasive of the other abrasive plate. As described in more detail below, the coarser grit abrasive sheet 310 can be on the lower or bottom abrasive plate 303, while the finer grit abrasive plate 308 is on the upper or top abrasive plate 302. In various embodiments, the abrasive-containing abrasive plates can be rotated in the same direction or in opposite directions. It is also possible to hold one plate in a fixed position and rotate the other plate. In this way, one surface of the substrate can be machined to a smoother surface than its opposite surface, and at least a portion of the grinding of the two surfaces can occur simultaneously.

Figure 5 is a photograph of a double-sided lapping machine suitable for implementing the embodiments described herein.

According to a specific embodiment, when a different roughness (texture) is desired between the top and bottom surfaces of the substrate to be processed, in this case one abrasive plate can use one fine gravel abrasive product while the other plate can Use a coarser grit abrasive product. For example, the top plate can be made from a fine grit abrasive product to create a surface with very low roughness to reduce or eliminate any downstream polishing process time required to achieve the final surface features. The bottom plate may contain a coarser grit abrasive product to produce a more typical A surface with a fine grinding or grinding operation. The size of the selected grit is preferably determined by the desired roughness/texture of the face to be processed and by the amount of substrate material to be removed.

By using two fixed abrasive plates having different grit sizes, the coarser grit abrasive can be used for most material removal, for example if it is desired to thin the substrate. The surface exiting from the coarser abrasive will be rougher than the surface produced by the finer grit, but in many cases this is not significant or actually desirable. For example, in the case of a sapphire wafer, the polished upper surface is advantageous for promoting the growth and equipment of the compound thin semiconductor film, whereas a rougher bottom surface is considered to promote heat transfer.

The finer grit abrasive plate will not remove as much material, but will produce a smoother surface ready for any additional polishing steps. Significantly, because the two faces of the substrate can be processed simultaneously by the abrasive plates having different grit sizes, the process of producing the desired substrate is much faster than the prior art (requiring multiple sequential grinding steps) .

The elimination of sequential separate rough and fine abrasive processing steps saves a significant amount of time even in applications where more than one or more polishing steps are still required. Each grinding process step typically requires 15 minutes to 30 minutes to complete, and it is often required for each grinding step to move the substrates to a completely different mill. By grinding the top surface with a fine abrasive while treating the bottom surface with a coarser abrasive, the steps in the process are eliminated, less equipment is required, and the supply cost is reduced (due to smoothing the bottom surface without wasting more than required) Abrasives).

Material removal rate as will be appreciated by those skilled in the art The smoothness of the resulting surface is largely determined by the size and shape of the abrasives used in the grinding process. The relative material removal between the two different abrasive plates and the extent of surface damage caused by the grinding process can also be adjusted by varying the speed or direction of rotation of the two different plates or the carriers. For example, the faster rotation of the rough abrasive plate will allow the desired material to be removed from the bottom surface of the wafer while completing the finer abrasive grinding process. For example, by adjusting the relative velocities of the coarse and fine abrasive abrasive plates, the coarse abrasive can be used to remove, for example, 40 micron to 50 micron material, while at the same time, the fine abrasive abrasive plate is used. To remove only 15 microns of material. In some prior art double side grinding or finishing mills, one plate is fixed and the other plate is rotated to create a relative speed between the fixed and rotating plates. In such machines, the relative speed between the rotating and non-rotating plates can also be adjusted to achieve the same desired material removal rate for the coarse and thin plates.

The rough abrasive plate can be the lower or bottom plate and the fine abrasive plate can be the upper plate. In this embodiment, gravity will account to prevent any loose abrasive particles or chips from the coarse abrasive from damaging or damaging the surface of the substrate treated with the finer abrasive. As will be appreciated by those skilled in the art, the presence of such finer particles will not adversely affect the surface finish of the coarser abrasive surface of the substrate.

In a specific embodiment, a slurry (coolant) is circulated to remove particulates (chips) from the surface of the abrasive plates during processing. The slurry can be recycled, and as a result, there is a possibility that abrasive particles and chips may be inadvertently introduced between the substrate body and the finer abrasive plate. Sex. If the slurry is recycled, the slurry can be filtered to substantially reduce or prevent coarse abrasive particles or chips from damaging the smoother surface of the substrate treated with the finer abrasive.

4 schematically illustrates a filtration system that can be used to substantially reduce or prevent coarse abrasive materials from inadvertently damaging a surface of a further polished substrate, in accordance with a particular embodiment. In the filtration system of Figure 4, a clean coolant is delivered using a coolant supply line 402 that can extend through the top abrasive plate. In a specific embodiment, the coolant flows during the entire grinding operation. A suitable coolant flow rate will provide sufficient lubricity to substantially reduce or prevent the substrates from being damaged by friction buildup and will wash away the abrasive debris. The coolant will flow (via gravity) down through the bottom grinding plate and out of the grinding machine via a coolant return line 404. This coolant can then flow into the coolant reservoir 406 for recycling. The coolant in the reservoir may first be subjected to centrifugal filtration 407 to separate the chips and grinding debris and then flow through a bag or cartridge filter 408. The bag or cartridge filter 408 will filter out any abrasive particles larger than the fine abrasive particles to substantially reduce or prevent the coarse abrasive particles from damaging or damaging the smoother upper surface of the substrates. The size of this final filtration can be determined by the specific application.

Applicants have also noted that the use of different abrasives on the upper or lower abrasive plate may tend to increase the likelihood that the processed substrate will exhibit unacceptable warpage or bending. The abrasive grit used, along with the rotational speed and direction, can be optimized to reduce any stress differential within the substrate body that can produce such variations in wafer shape.

The sapphire substrate produced by the above method is not only better than the use The prior art methods are faster and less expensive to produce, and the finished substrates also have improved geometries over those produced by conventional processing. In a particular aspect, a high surface area sapphire substrate produced in accordance with the embodiments described herein includes a generally planar surface having an a-plane orientation, an r-plane orientation, an m-plane orientation, or a c-plane. Orientation, and includes controlled dimensions. As used herein, "x-plane orientation" refers to a substrate having a major surface that extends generally along the x-plane of the crystal, typically having a specific substrate specification (such as those specified by the end customer) from x. - The slight orientation deviation of the plane. Specific orientations include r-plane and c-plane orientation, and certain embodiments utilize c-plane orientation.

As indicated above, the substrate can have a controlled dimension. A measure of the controlled dimension is the total thickness change, including TTV (total thickness variation) or nTTV (normalized total thickness variation).

For example, in one example, the TTV is generally about 3.00 microns, such as no greater than about 2.85 microns, or even no greater than about 2.75 microns. These aforementioned TTV parameters are associated with large size wafers, and in particular large size wafers having a controlled thickness. For example, embodiments can have a diameter of no less than about 6.5 cm, and a thickness of no more than about 490 microns. According to some embodiments, the aforementioned TTV parameters are associated with particularly large size wafers, including those having a diameter of no less than 7.5 cm, no less than 9.0 cm, no less than 9.5 cm, or no less than 10.0 cm. Wafer size may also be defined in terms of surface area on and above those TTV values may be not less than about 40cm ² and having a surface area not less than about 70cm ^2, not less than about 80cm ^2, or even less than about 115cm ² of the substrate Associated. Additionally, the thickness of the wafers can be further controlled to a value of no greater than about 500 microns, such as no greater than about 490 microns.

It should be noted that the term "diameter" as used in relation to wafer, substrate or ingot size means the smallest circle within the wafer, substrate or ingot. Thus, insofar as such components have a flat or multiple planes, such planes do not affect the diameter of the component.

Different embodiments have well controlled nTTV, such as no greater than about 0.037 [mu]m/cm^&lt;2&gt;. Particular embodiments have even excellent nTTV, such as no more than 0.035 μm/cm ² , or even no more than 0.032 μm/cm ² . Large-sized substrates have in particular achieved such controlled nTTVs, such as those having a size of not less than about 9.0 cm, and even not less than about 10.0 cm. Wafer size may also be defined in terms of surface area on and above those nTTV values may be not less than about 90cm ² and having a surface area not less than about 100cm ^2, about 115cm ² of the substrate is not less than associated.

Referring to the total thickness variation of the sapphire substrate, TTV is the absolute difference between the maximum thickness and the minimum thickness of the sapphire substrate (ignoring an edge exclusion zone, which typically includes the wafer from the wafer circumference) An edge-extending 3.0 mm ring), and nTTV is a value obtained by normalizing the surface area of the sapphire substrate by this value (TTV). A method for measuring the total thickness variation is given in ASTM Standard F1530-02.

In general, the nTTV value, as well as all other standardized features disclosed herein, may be normalized to a sapphire substrate having a generally planar surface and a substantially circular perimeter, the sapphire substrate may include one for A plane that identifies the orientation of the substrate is identified. In a specific embodiment, the sapphire substrate has a surface area of not less than about 25 cm ² , such as not less than about 30 cm ² , not less than 35 cm ² , or even not less than about 40 cm ² . Nonetheless, the substrate can have a larger surface area such that the generally planar surface has a surface area of no less than about 50 cm ² , or still no less than about 60 cm ² , or no less than about 70 cm ² . The sapphire substrates can have a diameter greater than about 5.0 cm (2.0 inches), such as no less than about 6.0 cm (2.5 inches). However, such sapphire substrates typically have a diameter of 7.5 cm (3.0 inches) or greater, and in particular include 10 cm (4.0 inches) wafers.

With further reference to the features of the sapphire substrate, in one embodiment, a generally planar surface of the sapphire substrate has a surface roughness Ra of no greater than about 100.0 Å, such as no greater than about 75.0 Å, or about 50.0 Å. Or even no more than about 30.0 Å. Even better surface roughness can be achieved, such as no more than about 20.0 Å, such as no more than about 10.0 Å, or no more than about 5.0 Å. The other major surfaces of a sapphire substrate will have a much higher surface roughness since the second surface has only undergone coarse or fine grinding rather than any fine grinding or polishing. The second, rougher surface will preferably have a surface roughness of at least 7000 Å, at least 5000 Å, or at least 4000 Å.

The generally planar surface of the sapphire substrate processed according to the above methods can also have excellent flatness. The flatness of a plane is typically understood as the maximum deviation of a surface from a best-fit reference plane (see ASTM F 1530-02). In this regard, normalized flatness is a measure of the surface flatness normalized by the surface area on the generally planar surface. In one embodiment, the normalized flatness (n-flatness) of the generally planar surface is greater than about 0.100 μm/cm ² , such as no greater than about 0.080 μm/cm ² , or even no greater than about 0.070 μm/cm. ² . Nonetheless, the planarized surface of the generally planar surface can be smaller, such as no greater than about 0.060 μm/cm ² , or no greater than about 0.050 μm/cm ² .

A sapphire substrate treated in accordance with the methods provided herein can exhibit a reduced warpage characterized by a standardized warpage, hereinafter n-warp. The warpage of a substrate is generally understood to be the deviation of the central surface of the substrate from a best-fit reference plane (see ASTM F 697-92 (99)). Regarding the measurement of the n-warpage, the warpage was normalized to take into account the surface area of the sapphire substrate. In one embodiment, the n-warpage is no greater than about 0.190 μm/cm ² , such as no greater than about 0.170 μm/cm ² , or even no greater than about 0.150 μm/cm ² .

The generally planar surface also exhibits reduced curvature. As is typically understood, the curvature of a surface is an absolute measure of the concavity or deformation of the surface, or a portion of the surface, as measured from a centerline of the substrate that is independent of any thickness variation present. The generally planar surface of the substrate treated in accordance with the methods provided herein exhibits reduced normalized curvature (n-bend) that is normalized to normalize the surface area of the generally planar surface. The degree of bending within. Thus, in one embodiment, the generally planar surface has an n-bendness of no greater than about 0.100 [mu]m/cm^&lt;2&gt;, such as no greater than about 0.080 [mu]m/cm^&lt;2&gt;, or even no greater than about 0.070 [mu]m/cm^&lt;2&gt;. In another embodiment, the substrate has an n-bend of between about 0.030 μm/cm ² and about 0.100 μm/cm ² , and particularly between about 0.040 μm/cm ² and about 0.090 μm/cm. Within the range between ² .

Many different aspects and implementations are possible. Some of those aspects and embodiments are described herein. After reading this manual, skilled Those skilled in the art will appreciate that the aspects and embodiments are merely illustrative and are not limiting of the scope of the invention. Embodiments may be based on any one or more of the items listed below.

Item 1. A method of machining a wafer having first and second opposing major surfaces, the method comprising: grinding a first major surface of a wafer using a first anchoring abrasive; and using a second anchoring abrasive Grinding a second major surface of the wafer, the second fixed abrasive having a grit size that is coarser than a grit size of the first fixed abrasive, wherein at least a portion of the first and second major surfaces of the wafer are ground At the same time.

Item 2. The method of item 1, wherein the wafer is a sapphire substrate.

The method of any of items 1 or 2, wherein the first fixed abrasive has an average abrasive particle size of no greater than 5 microns, no greater than 20 microns, no greater than 35 microns, or no greater than 75 Micron.

The method of any of the preceding claims, wherein the second fixed abrasive has an average abrasive particle size of at least 60 microns, at least 80 microns, at least 100 microns, or at least 200 microns.

The method of any one of the preceding claims, wherein the difference between the average abrasive particle size in the upper fixed abrasive disk and the average abrasive particle size in the lower fixed abrasive disk It is at least 20 microns, at least 50 microns, or at least 100 microns.

The method of any of the preceding claims, wherein grinding the first major surface of a wafer and grinding the second major surface of the wafer comprises pairing a first abrasive sheet and a second abrasive sheet Grinding between wafers, the first The two abrasive sheets have a coarser abrasive than the first abrasive sheet, wherein the first abrasive sheet grinds a first major surface of the wafer and the second abrasive sheet grinds a second major surface of the wafer.

The method of item 5, wherein the second abrasive sheet is located below the first abrasive sheet such that the second abrasive sheet grinds a bottom surface of the wafer and the first abrasive sheet grinds the wafer The top surface.

The method of any of items 1 to 4, wherein grinding a first major surface of the wafer and grinding a second major surface of the wafer comprises placing a wafer in the first and the first Between the two abrasive plates such that the top surface of the wafer is in flat contact with the abrasive surface of the first abrasive plate and the bottom surface of the wafer is in planar contact with the abrasive surface of the second abrasive plate; The abrasive plates, the wafer, or any combination thereof are rotated to polish the top and bottom surfaces of the wafer.

The method of any one of items 1 to 4, wherein grinding a first major surface of the wafer and grinding a second major surface of the wafer comprises placing at least one wafer into the first a circular carrier between the first and second abrasive plates such that a top surface of the wafer is in planar contact with the abrasive surface of the first abrasive plate and a bottom surface of the wafer is planar with the abrasive surface of the second abrasive plate The abrasive plates are contacted, rotated, and rotated to rotate the wafer between the rotating abrasive plates.

Item 9. The method of item 8, wherein a plurality of wafers are placed in the circular carrier.

The method of any one of clauses 8 or 9, wherein rotating the carrier comprises causing the carrier to surround its own axis and surround the The central axis of the abrasive plate is rotated.

Item 11. The method of any of items 5 to 10 further comprising applying a predetermined pressure to the top and bottom surfaces of the wafer having the abrasive surfaces of the abrasive plates when ground.

The method of any of items 5 to 11, wherein the relative material removal and the degree of any subsurface damage caused by the grinding can be varied by changing the rotational speed of the wafer relative to the at least one abrasive plate. Or direction to adjust.

The method of any one of clauses 5 to 12, wherein the second abrasive sheet removes material from 40 micrometers to 50 micrometers while the first abrasive panel removes material from 10 micrometers to 15 micrometers during the process. .

The method of any of items 5 to 13, further comprising applying a slurry to cool the abrasive surfaces and to remove loose abrasive material or chips.

Item 15. The method of item 14, further comprising, after the slurry has been used to cool the abrasive surfaces and for removing loose abrasive material or chips, recycling it, and using the used Prior to reintroduction of the slurry, it is filtered to prevent loose coarse abrasive particles in the recycled slurry from damaging the surface of the wafer during the grinding process.

The method of any of the preceding claims, wherein the polishing of the wafer with the second anchoring abrasive removes material from 30 microns to 50 microns during the grinding process.

The method of any of the preceding claims, wherein the first fixed abrasive is used to grind the wafer to remove 10 micrometers during the grinding process Meter to 15 micron material.

The method of any of the preceding claims, wherein when the polishing process is completed, the surface roughness of the wafer from the second fixed abrasive surface will be at least 4000 Å, at least 5000 Å, Or at least 7000 Å.

The method of any one of the preceding claims, wherein, when the grinding process is completed, the surface roughness of the surface on which the wafer is ground by the first fixed abrasive will be no more than 1000 Å, no more than 500Å, or no more than 100Å.

The method of any of the preceding claims, wherein the wafer comprises a single crystal substrate.

The method of any of the preceding claims, wherein the wafer comprises a polycrystalline material.

The method of any of the preceding claims, wherein the wafer comprises sapphire, tantalum carbide or gallium nitride.

The method of any of the preceding claims, wherein the wafer comprises glass, ceramic, or a metal compound.

Item 24. A device for double-side grinding of a flat substrate, the device comprising: an upper and a lower abrasive plate, the two abrasive plates being coaxially mounted such that a substrate can be disposed in both Between the abrasive plates and the two abrasive plates are rotatable about their coaxial central axis by a grinding plate drive mechanism; a substrate carrier disposed between the two abrasive plates, the carrier comprising a a carrier drive mechanism for rotating the carrier about its own central axis and about a coaxial central axis of the upper and lower abrasive plates; an upper fixed abrasive mounted to the inner surface of the upper abrasive plate a disk and a lower fixed abrasive disk mounted to an inner surface of the lower abrasive plate, wherein the lower fixed abrasive disk has a coarser abrasive grit than the upper fixed abrasive disk to cause both sides of a substrate Substrate grinding will remove material from the opposite substrate surface at different rates, and such that double-sided substrate grinding will result in opposing substrate surfaces having different surface roughness.

Item 25. The device of item 24, wherein the substrate comprises a single crystal substrate.

Item 26. The device of item 24, wherein the substrate comprises a polycrystalline material.

Item 27. The device of item 24, wherein the substrate comprises sapphire, tantalum carbide or gallium nitride.

Item 28. The device of item 24, wherein the substrate comprises glass, ceramic, or a metal compound.

Item 29. The item of any one of items 24 to 28, wherein the upper fixed abrasive disk, the lower fixed abrasive disk, or both comprise abrasive particles.

Item 30. The device of item 29, wherein the abrasive particles comprise a polycrystalline material or a ceramic material.

Item 31. The device of item 29, wherein the abrasive particles comprise alumina, ceria, strontium carbide, zirconia-alumina, or any combination thereof.

Item 32. The device of item 29, wherein the abrasive particles comprise diamond, cubic boron nitride, or any combination thereof.

The device of any one of items 29 to 32, wherein a difference between an average abrasive particle size in the upper fixed abrasive disk and an average abrasive particle size in the lower fixed abrasive disk The value is at least 20 microns, at least 50 microns, or at least 100 microns.

The device of any one of items 29 to 33, wherein the abrasive particles are irregular in shape.

The device of any one of items 29 to 34, wherein the abrasive particles are circular, square, or hexagonal in shape.

The device of any one of items 29 to 35, wherein the upper fixed abrasive disk, the lower fixed abrasive disk, or both comprise a bonded fixed abrasive.

The device of item 36, wherein the bonded fixed abrasive comprises abrasive particles fixed in a matrix.

Item 38. The device of item 37, wherein the substrate comprises a metal or metal alloy.

Item 39. The device of item 37, wherein the substrate comprises iron, aluminum, titanium, bronze, nickel, silver.

The device of item 36, wherein the bonded fixed abrasive comprises abrasive particles fixed in a resin, vitreous, or metal matrix.

Item 41. The device of item 36, wherein the bonded fixed abrasive comprises a grind that is bonded together in a resin, vitreous, or metal matrix. The granules are granulated to form the abrasive disc.

Item 42. A method of machining a sapphire substrate comprising: grinding a first surface of a sapphire substrate (having a diameter no less than) using a first anchoring abrasive; and grinding the sapphire substrate using a second anchoring abrasive The second surface, the second fixed abrasive has a grit size different from the grit size of the first fixed abrasive, wherein at least a portion of the grinding of the first and second faces of the sapphire substrate occurs simultaneously.

Item 43. A method of machining a wafer having first and second opposing major surfaces, the method comprising: grinding a first major surface of a wafer using a first anchoring abrasive; and grinding using a second fixed abrasive a second major surface of the wafer, the second fixed abrasive having a grit size that is coarser than a grit size of the first fixed abrasive, wherein at least a portion of the first and second major surfaces of the wafer are simultaneously occur.

Item 44. A method of simultaneously processing a flat substrate on both sides, the method comprising: placing a flat substrate between a first abrasive sheet and a second abrasive sheet, the first and second abrasive sheets being coaxial and Each having an abrasive surface, the abrasive surface of the second abrasive sheet comprising abrasive particles having a coarser grit size than the abrasive particles on the abrasive surface of the first abrasive sheet; the abrasive surface of the first abrasive sheet and the The top surface of the substrate is in planar contact and the abrasive surface of the second abrasive sheet is in planar contact with the bottom surface of the substrate; and the first abrasive sheet, the second abrasive sheet, the substrate, or any combination thereof Rotating to grind the top and bottom surfaces of the substrate, the second abrasive plate The coarse grit size results in a greater material removal rate and results in a rougher surface on the bottom surface of the substrate as compared to the top surface of the substrate.

Item 45. A method of removing material from a wafer by double-sided grinding with planetary kinematics, the method comprising: sandwiching the substrate between a first and a second bonded fixed abrasive plate The first and second abrasive plates each have an inwardly facing abrasive surface, the abrasive surface of the first abrasive plate has a finer grit than the second abrasive plate, and the second abrasive plate has a first a coarser grit of the abrasive sheet; rotating the first and second abrasive sheets, the wafer, or any combination thereof to simultaneously remove material from both the top and bottom surfaces of the wafer, the second abrasive sheet The coarser grit causes a higher material removal rate than the first abrasive plate and the finer grit of the first abrasive plate results in a smoother wafer surface than the second abrasive plate.

The method of any one of items 42, 43 or 45, wherein the first fixed abrasive has an average abrasive grain size of no greater than 5 microns, no greater than 20 microns, no greater than 35 microns, or no More than 75 microns.

The method of any of items 42, 43, 45, and 46, wherein the second fixed abrasive has an average abrasive particle size of at least 60 microns, at least 80 microns, at least 100 microns, or at least 200 microns.

Item 48. The item of any of the above, wherein the first and second surfaces of the abrasive wafer or sapphire substrate comprise a sapphire substrate ground between a first abrasive sheet and a second abrasive sheet, the The two abrasive sheets have a coarser abrasive than the first abrasive sheet.

Item 49. Any one of the above items, wherein the grinding The first and second surfaces of the round or sapphire substrate comprise a sapphire substrate ground between a first abrasive sheet and a second abrasive sheet, the second abrasive sheet having a coarser abrasive than the first abrasive sheet And the second abrasive plate is positioned below the first abrasive plate such that the second abrasive plate grinds the bottom surface of the wafer or sapphire substrate, and the first abrasive plate grinds the top surface of the wafer or sapphire substrate .

Item 50. The method of any one of the preceding claims, wherein the grinding the first and second surfaces of a wafer or sapphire substrate comprises: placing a sapphire wafer between the first and second abrasive sheets such that a top surface of the sapphire wafer is in planar contact with the abrasive surface of the first abrasive sheet and a bottom surface of the sapphire wafer is in planar contact with the abrasive surface of the second abrasive sheet; and the abrasive sheets, the sapphire wafer, Or any combination thereof to rotate to grind the top and bottom surfaces of the sapphire wafer.

Item 52. The item of any of the preceding claims, wherein a plurality of wafer or sapphire substrates are loaded into a circular carrier between the first abrasive sheet and the second abrasive sheet.

Item 52. The item of any of the preceding claims, wherein the grinding the first and second surfaces of a wafer or sapphire substrate comprises placing at least one sapphire wafer into a circle between the first and second abrasive plates a top surface of the sapphire wafer in planar contact with the abrasive surface of the first abrasive sheet and a bottom surface of the sapphire substrate in planar contact with the abrasive surface of the second abrasive sheet; rotating the abrasive plates And rotating the carrier to rotate the sapphire wafer between the rotating abrasive plates.

Item 53. The item of any of the preceding claims, wherein the substrates to be processed are held in a carrier disposed between the abrasive surfaces of the two abrasive sheets, and wherein a wafer or The first and second surfaces of the sapphire substrate include causing the carrier to rotate about its own axis and about the central axis of the abrasive plates.

Item 54. The method of any of the above, further comprising applying a predetermined inward pressure to the top and bottom surfaces of the wafer or sapphire substrate having the abrasive surface of the abrasive plates while the carrier, The abrasive plates, or any combination thereof, rotate.

Item 55. Any one of the preceding items, wherein the relative material removal between the two different abrasive plates and the extent of surface damage caused by the grinding process can also be varied by varying the two different plates or the carriers Speed or direction of rotation to adjust.

Item 56. Any one of the preceding items, wherein the second abrasive sheet removes from 40 microns to 50 microns of material while the first abrasive sheet removes from 10 microns to 15 microns of material during the process.

Item 57. Any one of the preceding items, further comprising applying a slurry to the abrasive surfaces of the first and second abrasive sheets to cool the abrasive surfaces and to remove loose abrasive material or chips.

Item 58. Item 57, further comprising, after the slurry is used to cool the abrasive surfaces and for removing loose abrasive material or chips, recycling it, and reintroducing the used slurry to the Prior to the first abrasive plate, it is filtered to prevent coarse abrasive particles from the second abrasive plate from damaging the surface of the wafer or sapphire substrate, the wafer or sapphire substrate The surface is ground to a smoother finish by the first abrasive sheet.

Item 59. A device for double-side grinding of a flat substrate, the device comprising: an upper and a lower abrasive plate, the two abrasive plates being coaxially mounted such that a substrate can be mounted on the two Between the grinding plates and the two grinding plates are rotatable by a driving mechanism; a carrier for holding the substrate disposed between the two polishing plates, the carrier comprising a driving mechanism, the driving mechanism For rotating the carrier about its own central axis and about a coaxial central axis of the abrasive plates; an upper fixed abrasive plate mounted to the inner surface of the upper abrasive plate and mounted within the lower abrasive plate The lower portion of the surface holds the abrasive plate, wherein the lower fixed abrasive plate has abrasive grit coarser than the upper fixed abrasive plate such that the double-sided substrate grinding of a substrate will at a different rate of material from the The opposing substrate surfaces are removed and the double-sided substrate is ground to produce opposing substrate surfaces having different surface roughnesses.

Item 60. The item of any of the above, wherein the substrate comprises a single crystal substrate.

Item 61. The item of any of the above, wherein the substrate comprises a polycrystalline material.

Item 62. The item of any of the above, wherein the substrate comprises sapphire, tantalum carbide or gallium nitride.

Item 63. The item of any of the above, wherein the substrate comprises glass, ceramic, or a metal compound.

Item 64. Any of the above items, wherein the first and the first The two abrasives include abrasive particles.

Item 65. Item 64, wherein the abrasive particles comprise a polycrystalline material or a ceramic material.

Item 66. Item 64, wherein the abrasive particles comprise alumina, ceria, strontium carbide, zirconia-alumina, or any combination thereof.

Item 67. Item 64, wherein the abrasive particles comprise diamond, cubic boron nitride, or any combination thereof.

Item 68. Item 64 wherein the difference between the average abrasive particle size in the first abrasive and the average abrasive particle size in the second abrasive is at least 20 microns, at least 50 microns, or at least 100 microns.

Item 69. Item 64, wherein the abrasive particles are irregular in shape.

Item 70. Item 64, wherein the abrasive particles are circular, square, or hexagonal.

Item 71. The item of any of the above, wherein the at least one of the first and second abrasives comprises a coated fixed abrasive.

Item 72. The item of any of the above, wherein the first and second abrasives comprise bonded abrasive particles.

Item 73. Item 72, wherein the bonded fixed abrasive comprises abrasive particles fixed in a matrix.

Item 74. Item 72, wherein the bonded fixed abrasive comprises abrasive particles fixed in a resin, vitreous, or metal matrix.

Item 75. Item 72, wherein the bonded fixed abrasive comprises abrasive particles bonded together in a resin, vitreous or metal matrix, A rigid abrasive plate for the micro-grinding process is formed.

The item 76, wherein the first and second abrasives comprise bonded fixed abrasives comprising abrasive particles fixed in a matrix.

Item 77. Item 73, wherein the substrate comprises a metal or metal alloy.

Item 78. Item 73, wherein the substrate comprises iron, aluminum, titanium, bronze, nickel, silver, or any combination thereof.

Item 79. The item of any of the above, wherein, in the grinding, material from 30 microns to 50 microns is removed by coarse grinding of the second abrasive sheet.

Item 80. The item of any of the above, wherein, in the grinding, material from 10 microns to 15 microns is removed by fine grinding of the first abrasive sheet.

Item 81. The item of any of the above, wherein when the grinding process is completed, the surface roughness of the rough abrasive surface of the wafer or sapphire substrate will be at least 4000 Å, at least 5000 Å, or at least 7000 Å.

Item 82. The item of any of the above, wherein when the grinding process is completed, the surface roughness on the fine abrasive surface will be no more than 1000 Å, no more than 500 Å, or no more than 100 Å.

Item 83. A finished sapphire substrate having a first side having a surface roughness of no greater than 1000 Å and a second side having a surface roughness of at least 4000 Å.

Item 84. A method prepared using the method of any of the above items Finished sapphire substrate.

By way of example, a C-plane sapphire wafer having a diameter of 4 inches is processed according to an embodiment by applying processing parameters as described below.

As described above, starting from processing a cut or sliced ingot or ingot. The ingot is typically sliced using a one-line sawing technique. The wire sawing process can last for several hours, typically in the range of between about 4 hours and 8 hours. It will be appreciated that the duration of the wire sawing process depends, at least in part, on the diameter of the ingot being sliced and thus may last for more than 8 hours.

After sawing on the wire, the wafers have an average thickness of about 1.0 mm or less. Typically, the wafers have an average surface roughness (Ra) of less than about 1.0 microns, an average total thickness variation of about 30 microns, and an average bend of about 30 microns.

After the ingot is sawed on-line to produce a wafer, the wafers are subjected to a grinding process in accordance with an embodiment as described herein. The wafers can be loaded into a double-sided micro-grinding machine such as an AC 1000 by Peter Wolters or a RC 5400 of PR Hoffman. The bottom grinding plate can use a rough vitrified grinding wheel having an average grit size in the range of about 80 microns to 200 microns. The coarse grinding plate will rotate at approximately 60 rpm to 500 rpm.

The top abrasive plate preferably uses a thinner vitrified abrasive wheel having an average grit size in the range of from about 10 microns to 80 microns. Preferably, the fine abrasive plate will be rotated at a slower rate than the roughened plate such that the substrate material will preferably be removed from the bottom surface of the substrate.

Any typical synthetic slurry can be used as the coolant/grinding liquid.

In a specific embodiment, the above processing parameters should result in a material removal rate (MPR) of about 5 μm/min to 10 μm/min for the rough abrasive sheet and an MPR of 1 μm/min to 5 μm/min for the fine abrasive sheet. The sapphire substrate will preferably be about 1 mm thick after the grinding is completed. The surface roughness on the fine abrasive surface will be about 0.1 μm (1000 Å), but can be as low as 500 Å. The surface roughness on the rough abrasive surface will be about 4000 Å, but can be as high as 7000 Å or larger for some applications.

Once the grinding step is complete, the sapphire substrates can be further polished on the fine abrasive surface using conventional polishing methods to reduce the surface roughness to a mirror finish of 10 Å to 400 Å.

Although most of the previously discussed embodiments are directed to sapphire wafers, the embodiments described herein can be applied to any substrate production process that utilizes a coarse or fine grinding followed by a second finer polishing step. Improve surface finish or reduce surface damage required only on one side of the substrate. For example, embodiments of the present invention can be applied to finishing (production) of oriented single crystals including sapphire and tantalum carbide, other polycrystalline materials, ceramics, glass, metals, plastics, and the like. Moreover, embodiments of the present invention can be applied to any substrate or part currently processed in a grinding operation or a fixed abrasive operation to produce a desired geometry and surface finish, which is referred to as a grinding operation or a fixed abrasive operation. “Micro-grinding”, “grinding with fine grinding kinematics”, “grinding with planetary kinematics” or “fixed abrasive grinding”.

As used herein, the terms "wafer" and "base" are used synonymously herein. "Plate" refers to a sapphire material that is being formed or processed into a sheet, which is used as a substrate on which a semiconductor layer is epitaxially grown, such as for forming an optoelectronic device. Often, it will be unfinished. It is common for processed sapphire sheets to be referred to as wafers and to refer to finished sapphire sheets as substrates, however, as used herein, such terms do not necessarily imply such a distinction.

The invention described herein has broad applicability and can provide many of the benefits shown above and in the examples above. These embodiments will vary widely depending on the particular application, and not every embodiment will provide all of the benefits and all of the objectives achievable by the present invention. It should be noted that not all of the activities described above throughout the description or examples are required, a portion of a particular activity may not be required, and one or more additional activities may be performed in addition to those described. Still further, the order in which the activities are listed does not have to be the order in which they are performed.

In the above description, a number of concepts have been described with respect to a number of specific embodiments. However, it will be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be construed in the It will be understood by those skilled in the art <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; Contrary to this, various features that are described in the context of a single embodiment can be provided separately or in any sub-combination. In addition, references to specified range values include each of the ranges value.

As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", or Any other changes to them are intended to cover non-proprietary inclusions. For example, a process, method, article, or instrument that comprises a list of features is not necessarily limited to those features, but may include other features not specifically listed or inherent to such a process, method, article, or instrument. In addition, "or" means inclusive - or not exclusive - or, unless explicitly stated to the contrary. For example, Condition A or B meets any of the following: A is true (or exists) and B is false (or non-existent), A is false (or non-existent) and B is true (or exists), and A and B Both are true (or exist). In addition, "a/an" is used to describe the elements and components described herein. This is done merely for convenience and gives a general meaning of the scope of the invention. This description should be read to include one or a plurality of singular, and the singular includes the plural unless it is clearly indicated otherwise.

Benefits, other advantages, and solution to problems have been described above with respect to specific embodiments. However, the benefits, advantages, solutions to problems, and any one or more features that may result in any or all of the benefits, advantages, or solutions may not be construed as critical or essential to any or all of the scope of the claims. Or necessary features.

Although the present invention and its advantages are described in detail, it is understood that various modifications may be made in the embodiments described herein without departing from the spirit and scope of the invention. Replace, and change. In addition, the scope of the invention is not intended to limit the specific embodiments of the process, machine, manufacture, composition, means, methods, and steps described in the specification. As will be readily appreciated by those skilled in the art from this disclosure, it is possible in accordance with the present invention to perform substantially the same functions as the ones described herein or substantially achieve the same results present or Process, machine, manufacturing, material composition, means, method or step to be developed in the future. Therefore, the scope of the appended claims is intended to cover such a process, machine, manufacture, composition, means, method, or step.

300‧‧‧ double-sided lapping machine

301‧‧‧ Carrier

302, 303‧‧‧ grinding plate

304‧‧‧Substrate

308, 310‧‧‧ abrasive plates

Claims (10)

A method for processing a wafer having first and second opposing major surfaces, the method comprising: grinding a first major surface of a wafer using a first anchoring abrasive; and grinding using a second fixed abrasive a second major surface of the wafer, wherein: the second fixed abrasive has a grit size that is coarser than a grit size of the first fixed abrasive, and an average abrasive grain size of the upper fixed abrasive disk is at the lower portion The difference between the average abrasive particle sizes of the fixed abrasive disc is at least 20 microns, and at least a portion of the grinding of the first and second major surfaces of the wafer occurs simultaneously. The method of claim 1, wherein the wafer is a sapphire substrate. The method of claim 1, wherein the difference between the average abrasive particle size of the upper fixed abrasive disk and the average abrasive particle size of the lower fixed abrasive disk is at least 50 microns, or At least 100 microns. The method of any one of claims 1 to 3, wherein grinding the first major surface of a wafer and grinding the second major surface of the wafer comprises pairing a first abrasive plate with a first Grinding the wafer between the two abrasive plates, the second abrasive plate having a coarser abrasive than the first abrasive plate, Wherein the first abrasive plate grinds the first major surface of the wafer and the second abrasive plate grinds the second major surface of the wafer. The method of any one of claims 1 to 3, wherein grinding a first major surface and a second major surface of the wafer comprises: placing a wafer on the first and second abrasives Between the plates such that the top surface of the wafer is in planar contact with the abrasive surface of the first abrasive plate and the bottom surface of the wafer is in planar contact with the abrasive surface of the second abrasive plate; and the abrasive plates, The wafer, or any combination thereof, is rotated to polish the top and bottom surfaces of the wafer. The method of any one of claims 1 to 3, wherein grinding a first major surface and a second major surface of the wafer comprises: placing at least one wafer in a first a circular carrier between the second abrasive plates; placing a top surface of the wafer in planar contact with the abrasive surface of the first abrasive plate and a bottom surface of the wafer in planar contact with the abrasive surface of the second abrasive plate; Rotating the abrasive plates; and rotating the carrier to rotate the wafer between the rotating abrasive plates. The method of claim 5, further comprising applying a slurry to cool the abrasive surfaces and to remove loose abrasive materials Material or chips. A double-side grinding apparatus for a flat substrate, the apparatus comprising: an upper and a lower abrasive plate, the two abrasive plates being coaxially mounted such that a substrate can be disposed on the two abrasive plates And the two abrasive plates are rotatable about their coaxial central axis by a grinding plate drive mechanism; a substrate carrier disposed between the two abrasive plates, the carrier comprising a carrier drive mechanism, a carrier drive mechanism for rotating the carrier about its own central axis and about a coaxial central axis of the upper and lower abrasive plates; and an upper fixed grinding disk mounted to the inner surface of the upper abrasive plate and a mounting to The lower portion of the lower surface of the lower abrasive plate holds the abrasive disk, wherein the difference between the average abrasive particle size of the upper fixed abrasive disk and the average abrasive particle size of the lower fixed abrasive disk is at least 20 microns And the lower fixed abrasive disc has a coarser abrasive grit than the upper fixed grinding disc, such that the double-sided substrate of one substrate is ground at different rates Such opposing surface of the substrate is removed, and the substrate so that the double-sided polishing of the substrate to produce opposing surfaces with different surface roughness. The apparatus of claim 8 wherein the difference between the average abrasive particle size in the upper fixed abrasive disk and the average abrasive particle size in the lower fixed abrasive disk is at least 50 microns, or At least 100 microns. The device of claim 8 or 9, wherein the upper fixed abrasive disk, the lower fixed abrasive disk, or both comprise a bonded fixed abrasive.