Carrier wafer and method for manufacturing a carrier wafer

Abstract

A method for manufacturing a carrier wafer includes the steps of lapping a first surface and a second surface of a carrier wafer, the carrier wafer comprising a glass, glass ceramic, or ceramic material, so that the carrier wafer is substantially flat, wherein after the lapping step, the carrier wafer has a diameter of 250 mm to 450 mm and a thickness of 0.5 mm to 2 mm; and polishing the first surface of the carrier wafer with at least one of a pressure differential, a speed differential, or a time differential between a center and an edge of the carrier wafer, so that the first surface has a convex or concave shape.

Description

Related Applications

[0001] This application claims the benefit of priority of Chinese Patent Application No. 201811147777.5, filed on September 29, 2018, the content of which is relied upon herein and incorporated herein by reference in its entirety.

Technical Field

[0002] The present disclosure generally relates to a method for manufacturing a carrier wafer, a polishing apparatus therefor, and a carrier wafer.

Background Art

[0003] Thickness uniformity across a substrate is typically an important characteristic that affects the suitability of the substrate for use. In many cases, after the manufacture of the substrate, final mechanical polishing and / or chemical polishing and / or cleaning of the substrate is required to provide a sufficiently clean and uniform surface (i.e., for depositing, growing, or bonding additional layers onto the surface). Final chemical polishing and / or mechanical polishing often removes a predetermined thickness of the substrate. Removal of material from the substrate during final polishing often causes the substrate to deviate from the predetermined specifications and renders the substrate unusable.

Summary of the Invention

[0004] According to a first aspect of the present disclosure, a method for manufacturing a carrier wafer includes a step of lapping a first surface and a second surface of the carrier wafer such that the carrier wafer including a glass, glass ceramic, or ceramic material is substantially flat, wherein after the lapping step, the carrier wafer has a diameter of 250 mm to 450 mm and a thickness of 0.5 mm to 2 mm, and a step of polishing the first surface of the carrier wafer with at least one of a pressure difference, a speed difference, or a time difference between a central portion and an edge portion of the carrier wafer such that the first surface has a convex shape or a concave shape.

[0005] According to the second embodiment, the method of embodiment 1 is configured such that the step of polishing the first surface of the carrier wafer includes a step of polishing the first surface of the carrier wafer with a pressure difference between the center and the edge, and further, the pressure difference is 5 psi (approximately 34.5 kPa) to 20 psi (approximately 138 kPa).

[0006] According to a third embodiment, the method of embodiment 1 is configured such that the first surface of the carrier wafer is polished to a substantially flat shape through a finish polishing step performed after the polishing step.

[0007] According to a fourth aspect, the method of aspect 1 further includes, after the polishing step, a step of finishing polishing the center and edges of the first surface to a substantially flat shape, wherein at least one of the carrier wafer and the polishing pad is rotated relative to each other during the finishing polishing step so that the center and edges of the first surface are polished simultaneously at different speeds.

[0008] According to the fifth embodiment, the method of embodiment 1 is configured such that a convex shape is defined by the step of polishing the first surface of the carrier wafer.

[0009] According to the sixth aspect, the method of aspect 1 is configured such that a concave shape is defined by the step of polishing the first surface of the carrier wafer.

[0010] According to the seventh aspect, the method of aspect 1 is configured such that the step of polishing the first surface further includes the step of rotating a polishing head relative to the first surface of the carrier wafer.

[0011] According to the eighth aspect, the method of aspect 1 is configured such that the first surface and the second surface are on opposite sides of the carrier wafer.

[0012] According to the ninth aspect, the method of aspect 8 is configured such that the wrapping of the first surface and the wrapping of the second surface are performed substantially simultaneously.

[0013] According to the tenth embodiment, the method of embodiment 1 is configured such that, after performing the step of polishing the first surface of the carrier wafer with a pressure difference, the difference between the thickness of the center and the thickness of the edge of the carrier wafer is 1 μm to 5 μm.

[0014] According to the eleventh embodiment, the method of embodiment 1 is configured such that the carrier wafer is substantially circular.

[0015] According to the twelfth embodiment, the method of embodiment 11 is configured such that the carrier wafer has an outer diameter of 200 mm to 400 mm.

[0016] According to a thirteenth aspect of the present disclosure, the polishing apparatus comprises an adjustable weight, a polishing head connected to a motor, a turntable, and a lever connected to the motor and a counterweight, the motor and the counterweight being located at opposite ends of the lever's pivot point. The adjustable weight and the counterweight are configured to vary the force applied to the polishing head.

[0017] According to the 14th embodiment, the polishing apparatus of embodiment 13 is configured such that the pivot point of the lever is connected to a support structure.

[0018] According to the 15th embodiment, the polishing apparatus of embodiment 13 is configured such that the stepper motor is positioned on an adjustable weight.

[0019] According to the 16th aspect, the polishing apparatus of aspect 13 is configured such that the polishing head is tilted.

[0020] According to a 17th aspect of the present disclosure, a carrier wafer comprises a body defining a first surface having a central part and an edge, and a second surface opposite to the first surface, wherein the first surface defines a substantially convex or concave shape, and the second surface is substantially flat. The first surface is configured to be polished to a substantially flat shape under different polishing speeds between the central part and the edge.

[0021] According to the 18th aspect, a carrier wafer according to aspect 17 is configured such that the difference between the thickness of the central portion and the thickness of the edge portion of the carrier wafer is 1 μm to 5 μm.

[0022] According to the 19th aspect, a carrier wafer according to aspect 17 is configured such that the carrier wafer contains glass.

[0023] According to the 20th aspect, a carrier wafer according to aspect 17 is configured such that the first surface defines a concave shape.

[0024] These and other features, advantages, and objects of the present disclosure will be further understood and interpreted by those skilled in the art by reference to the following specification, claims, and accompanying drawings.

Brief Description of the Drawings

[0025] The following is a description of the figures in the accompanying drawings. The drawings are not necessarily to scale, and certain features and specific views of the drawings may be shown exaggerated in scale or concept for clarity and brevity. [Figure 1A] It is a cross-sectional view of a carrier wafer according to at least one example. [Figure 1B] It is a cross-sectional view of a carrier wafer according to at least one example. [Figure 2] It is a flowchart of a method for manufacturing a carrier wafer according to at least one example. [Figure 3A] It is a schematic top view of a polishing apparatus according to at least one example. [Figure 3B] It is a cross-sectional view taken along line IIIB-IIIB of FIG. 3A according to at least one example.

Modes for Carrying Out the Invention

[0026] Further features and advantages of the present invention will be described in the following detailed description and will be apparent to those skilled in the art from this description or will be recognized by carrying out the invention as described in the following description together with the claims and accompanying drawings.

[0027] As used herein, the term "and / or" means that when used to list two or more items, any one of the listed items may be used alone, or any combination of two or more of the listed items may be used. For example, if a composition is described as containing components A, B and / or C, the composition may contain A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B and C.

[0028] In this specification, relational terms such as first and second, upper and lower are used solely to distinguish one entity or action from another, and do not necessarily require or imply any actual relationship or order between such entities or actions.

[0029] Those skilled in the art will understand that the disclosures and other components described herein are not limited to any particular material. Other exemplary embodiments of the disclosures disclosed herein may be formed from a wide range of materials unless otherwise specified herein.

[0030] For the purposes of this disclosure, the term “connection” (in all its forms, such as connecting, connecting, being connected, etc.) generally means the direct or indirect joining of two components to each other (electrically or mechanically). Such joining may be inherently static or inherently dynamic. Such joining may be achieved by the two (electrically or mechanically) components and any additional intermediate members being formed integrally with each other or with the two components as a single, integrated body. Such joining may be inherently permanent or inherently detachable or removable, unless otherwise specified herein.

[0031] Where used herein, the term “approximately” means that quantities, sizes, formulations, parameters, and other quantities and characteristics do not need to be exact, but may be approximate and / or greater or less, taking into account tolerances, conversion factors, rounding, measurement errors, and other factors known to those skilled in the art, as necessary. Where the term “approximately” is used to describe a range value or endpoint, this disclosure should be understood to include the specific value or endpoint being referenced. Numerical values ​​or endpoints of ranges in this specification are intended to include two embodiments: one embodiment prefixed with “approximately” and another embodiment not prefixed with “approximately.” It should be further understood that each endpoint of a range is evident both in relation to the other endpoint and independently of the other endpoint.

[0032] As used herein, the terms “substantial,” “substantially,” and their variations are intended to indicate that the described feature is equal to or approximately equal to a value or description. For example, a “substantially flat” surface is intended to refer to a flat or nearly flat surface. Furthermore, “substantially” is intended to mean that two values ​​are equal to or approximately equal to each other. In some embodiments, “substantially” is intended to mean values ​​within about 10% of each other. As used herein, the term “substantially flat” means that the body defining a substantially flat surface has a total thickness variation of 1 μm or less.

[0033] It is also important to note that the configuration and arrangement of the components in this disclosure are merely illustrative, as shown in the exemplary embodiments. Although only a few embodiments of this innovation are described in detail in this disclosure, a person skilled in the art who has read this disclosure will readily understand that a variety of modifications (e.g., changes in the size, dimensions, structure, shape and proportions, parameter values, mounting arrangement, material use, color, orientation, etc.) are possible without substantially departing from the novel teachings and advantages of the enumerated subject matter. For example, a component shown as being integrally formed may be composed of multiple parts, or a component shown as multiple parts may be integrally formed, the behavior of the boundary may be reversed or otherwise modified, the length or width of the structure and / or members or connections or other components of the system may be changed, and the nature or number of adjustment positions provided between components may also be changed. It should be noted that the components and / or assemblies of the system may be composed of any of a wide range of materials that provide sufficient strength or durability, and in any of a wide range of colors, textures and combinations. Accordingly, all such modifications are intended to fall within the scope of this innovation. Other substitutions, modifications, changes, and omissions can be made in the design, operating conditions, and arrangement of the desired and other exemplary embodiments without departing from the spirit of this innovation.

[0034] From here, with reference to Figures 1A and 1B, the carrier wafer 10 is shown. The carrier wafer 10 has a body 14 defining two main surfaces opposite to each other, referred to as a first surface 18 and a second surface 22. In various examples, the carrier wafer 10 may further define one or more secondary surfaces 24 arranged along the edge of the body 14. In yet another example, the portions of the first surface 18 and the second surface 22 may be in contact or intersect. The body 14 of the carrier wafer 10 includes a central part 26 located inside or within the edge 30. The edge 30 of the carrier wafer 10 is positioned close to the edge of the body 14 of the carrier wafer 10. The edge 30 may further surround the central part 26. The body 14 of the carrier wafer 10 may have a circular, elliptical, oblong, triangular, square, rectangular, pentagonal, or higher-order polygonal shape.

[0035] The carrier wafer 10 may have an outer diameter or maximum outer width of 200mm to 450mm or 250mm to 450mm. For example, the outer diameter or maximum outer width may be 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, 320mm, 330mm, 340mm, 350mm, 360mm, 370mm, 380mm, 390mm, or 400mm, or any and all of these values ​​and ranges as endpoints. It should be understood that a circular example of the carrier wafer 10 has a diameter, while a polyhedral example of the carrier wafer 10 may have the longest length measured from the corners of the body 14.

[0036] The first surface 18 of the carrier wafer 10 can take on or be defined in various shapes. For example, the first surface 18 can be defined as substantially convex (i.e., Figure 1A). In the convex example, the first surface 18 has a positive principal radius of curvature such that the portion of the first surface 18 extending over the central part 26 can be generally higher than the portion of the first surface 18 extending over the edge 30. That is, in the convex example, the first surface 18 extends away from the second surface 22 such that the body 14 of the carrier wafer 10 can be thicker at the central part 26 than at the edge 30. The apex of the convex shape of the first surface 18 may be located at the center of the carrier wafer 10 or may be offset from the center of the carrier wafer 10. In yet another example, the first surface 18 can have a concave shape (i.e., Figure 1B). The first surface 18 has a negative principal radius of curvature, in the concave example, such that the portion of the first surface 18 extending over the central 26 can be generally lower than the portion of the first surface 18 extending over the edge 30. That is, the concave example of the first surface 18 extends toward the second surface 22 of the body 14, such that the carrier wafer 10 can be thinner at the central 26 than at the edge 30. The thinnest point of the concave first surface 18 may be located at the center of the carrier wafer 10 or may be offset. It should be understood that the principal radius of curvature of the first surface 18 may be the same across the first surface 18 or may vary without deviation from the teachings provided herein (i.e., intentionally and / or due to manufacturing differences).

[0037] According to various examples, the carrier wafer 10 may have a thickness in the range of 50 μm to 5 mm at its thickest point (i.e., measured from the first surface 18 to the second surface 22). The carrier wafer 10 may have a thickness in any range having 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, 2 mm, 3 mm, 4 mm, 5 mm, or any two of these values ​​as endpoints. The thickness of the carrier wafer 10 may be in the range of 1 μm to 1000 μm or 100 μm to 500 μm. It should be understood that the thickness of the carrier wafer 10 may vary over its length (i.e., periodically or randomly).

[0038] The carrier wafer 10 may have a total thickness variation over the first surface 18. The total thickness variation is defined as the difference between the thickest point and the thinnest point of the carrier wafer 10 while the carrier wafer 10 is clamped in place. The total thickness variation over the first surface 18 may be 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3.0 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4.0 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, or 5.0 μm, or any range having any two of these values ​​as endpoints or any range having any one of these values ​​as an upper limit. The total thickness variation can be 0.1 μm to 50 μm, or 0.1 μm to 40 μm, or 0.1 μm to 30 μm, or 0.1 μm to 20 μm, or 0.1 μm to 10 μm, or 1 μm to 5 μm. In various examples, the total thickness variation can be between the edge of the carrier wafer 10 (i.e., the furthest or outermost part of the first surface 18) and the thickest point of the carrier wafer 10 (i.e., the apex of the convex first surface 18) or the thinnest point of the carrier wafer 10 (i.e., the lowest point of the concave first surface 18). Thus, the difference between the thickness of the central part 26 and the thickness of the edge 30 of the carrier wafer 10 (i.e., the total thickness variation) can be 1 μm to 5 μm.

[0039] As described above, in the example of a convex shape, the first surface 18 has a positive principal radius of curvature. In the example of a convex shape of the first surface 18, the principal radius of curvature can be 2m, 4m, 10m, 100m, 1000m, 2000m, 3000m, 4000m, or 5000m, or any range having any and all values ​​and / or any two of these values ​​as endpoints, or any range having any one of these values ​​as an upper limit. In the example of a concave shape of the first surface 18, the principal radius of curvature can be negative. In the example of a concave shape of the first surface 18, the principal radius of curvature can be -2m, -4m, -10m, -100m, -1000m, -2000m, -3000m, -4000m, or -5000m, or any range having any and all values ​​and / or any two of these values ​​as endpoints, or any range having any one of these values ​​as an upper limit.

[0040] As will be described in more detail below, the first surface 18 of the carrier wafer 10 can be configured such that when a polishing pad is applied to the first surface 18, it is polished to a substantially flat shape (i.e., the body 14 of the carrier wafer 10 has a total thickness variation of 1 μm or less). Conventional substrates often undergo one or more polishing steps after being purchased and delivered to the customer. In applications where the tolerance for total thickness variation of the substrate is particularly narrow, even a cleaning or polishing step can remove a lot of material from the substrate, leading to the substrate falling outside the tolerance. Often, the cause of tolerance errors in such polishing is the difference in polishing speed of the rotary polishing (i.e., due to different rotation speeds of the circular polishing structure). The use of the carrier wafer 10 and the first surface 18 disclosed herein may be advantageous in compensating for expected polishing steps by utilizing a concave or convex first surface 18. The concave or convex shape of the first surface 18 allows for the equalization of subsequent speed differences in polishing and material removal on the first surface 18, so that the first surface 18 becomes substantially flat or planar after polishing.

[0041] In various examples, the second surface 22 of the carrier wafer 10 is substantially flat. For example, the second surface 22 may have a height deviation of 0.1 μm to 1 μm. In yet other examples, the second surface 22 may be cut into a curved shape (i.e., concave and / or convex), faceted, and / or have other shapes, without departing from the teachings provided herein.

[0042] The carrier wafer 10 may include glass, glass ceramic, ceramic material, and / or combinations thereof. Exemplary glass-based examples of the carrier wafer 10 may include soda-lime glass, alkali aluminosilicate glass, alkali-containing borosilicate glass, and / or alkali aluminoborosilicate glass. For the purposes of this disclosure, the term “glass-based” may mean glass, glass ceramic, and / or ceramic material. According to various examples, the carrier wafer 10 can be a glass-based carrier wafer 10. In glass-based examples of the carrier wafer 10, the carrier wafer 10 may be reinforced or high-strength. For example, an example of glass in the carrier wafer 10 may be thermally reinforced (e.g., for a high-strength carrier wafer 10) or may have ion-exchange regions (e.g., for a reinforced carrier wafer 10). Furthermore, the carrier wafer 10 may include sapphire and / or polymer material. Examples of suitable polymers include, but are not limited to, polystyrene (PS) (including styrene copolymers and blends), polycarbonate (PC) (including copolymers and blends), polyester (including copolymers and blends, including polyethylene terephthalate and polyethylene terephthalate copolymers), polyolefin (PO) and cyclic polyolefin (cyclic PO), polyvinyl chloride (PVC), acrylic polymers (including copolymers and blends) including polymethyl methacrylate (PMMA), thermoplastic urethane (TPU), polyetherimide (PEI), and thermoplastic resins including blends of these polymers. Other exemplary polymers include epoxy, styrene, phenol, melamine, and silicone resins. Furthermore, the carrier wafer 10 can be composed of one or more crystalline materials. For example, the carrier wafer 10 may be composed of one or more silicon crystals (i.e., silicon wafers).

[0043] In various examples, the carrier wafer 10 can be configured to be used for forming or supporting one or more semiconductor panels. In such examples, the carrier wafer 10 can be made of glass or glass ceramic and can be used to transport or support one or more semiconductors, electrical sensors and / or other electrical components. Thus, the carrier wafer 10 can be utilized in a "semiconductor on glass" process.

[0044] Referring here to Figure 2, a method 40 for manufacturing a carrier wafer 10 is shown. Method 40 can begin with step 44, in which the first surface 18 and the second surface 22 of the carrier wafer 10 are lapped so that the carrier wafer 10 is substantially flat. As described above, the carrier wafer 10 can be made of glass, glass ceramic, or ceramic material. Furthermore, after lapping, the carrier wafer 10 can have a diameter of 250 mm to 450 mm and a thickness of 0.5 mm to 2 mm. As used herein, lapping is a machining process in which two surfaces are rubbed together with a plurality of loose or free-rolling abrasives. Lapping can be performed using a lapping machine configured to utilize one or more abrasives that are harder than the material of the carrier wafer 10. The abrasives are placed between the lapping plate and the first surface 18 of the carrier wafer 10 so that the first surface 18 is polished. The abrasives used in the lapping process of step 44 may include aluminum oxide, emery, silicon carbide, boron carbide, diamond, and / or tungsten carbide. In various examples, both the first surface 18 and the second surface 22 can be lapped simultaneously or substantially simultaneously. In such examples, the carrier wafer 10 can be placed in and / or passed through a lapping machine so that both the first surface 18 and the second surface 22 are lapped. Lapping the first surface 18 and / or the second surface 22 can result in the first surface 18 and / or the second surface 22 being substantially flat. Thus, the carrier wafer 10 may have curvature, warping, roughness and / or other aspects that are reduced or removed by lapping both the first surface 18 and the second surface 22. In addition to lapping the first surface 18 and / or the second surface 22, the first surface 18 and / or the second surface 22 can be polished.

[0045] Next, step 48 is performed to clean the first surface 18 of the carrier wafer 10. As used herein, cleaning is defined as the removal of particulate matter and / or contaminants from the first surface 18 that tend to impair, degrade or otherwise reduce the optical quality of the first surface 18. Cleaning of the carrier wafer 10 can be performed using polar liquids, surfactants, nonpolar liquids and / or combinations thereof. For example, the carrier wafer 10 can be rinsed and cleaned in water and a surfactant, and then rinsed with alcohol. Furthermore, cleaning of the carrier wafer 10 can be performed with the help of ultrasonic pulses and / or compressed gas. In examples where the first surface 18 and the second surface 22 are each lapped, it should be understood that both the first surface 18 and the second surface 22 can be cleaned either indirectly or simultaneously. Cleaning the first surface 18 and / or the second surface 22 may be advantageous in removing large or coarse abrasives present on the first surface 18 and / or the second surface 22 that may interfere with subsequent polishing steps.

[0046] Referring to Figures 2, 3A, and 3B, step 52 is performed to polish the first surface 18 of the carrier wafer 10 by at least one of a pressure difference, speed difference, or time difference between the center 26 and the edge 30 of the carrier wafer 10 such that the first surface 18 has a convex or concave shape. As used herein, polishing is defined as the process in which a plurality of abrasive grains are packed into a fibrous polishing cloth and the cloth is applied to a workpiece. It should be understood that polishing can both reduce the roughness of a surface (e.g., the first surface 18) and remove a small amount of material (e.g., 0.2 μm to about 10 μm) from the surface. Step 52 can be performed using a polishing apparatus 56. Although referred to as polishing apparatus 56, it should be understood that the slurry, pad and abrasive can be modified so that the polishing apparatus 56 can be used as a lapping apparatus in step 44. In the example shown, the polishing apparatus 56 is a single-sided contouring or polishing apparatus 56, but it should be understood that the polishing apparatus 56 can polish multiple surfaces at once. Furthermore, two or more carrier wafers 10 can be polished at once by the polishing apparatus 56. The polishing apparatus 56 includes a support structure 60 to which a lever 64 is pivotally connected via a pivot 68. One end of the lever 64 has a counterweight 72. The opposite end of the lever 64 has an arm 76 connected to a polishing head 80. The support structure 60 supports a stepper motor 84, which is connected via a crankshaft 92 to an adjustable weight 88. The adjustable weight 88 is located above the polishing motor 96 that rotates the polishing head 80. The polishing motor 96 is connected to the lever 64. According to various examples, the polishing head 80 is smaller than the carrier wafer 10 and / or the first surface 18. The polishing head 80 contacts and polishes the first surface 18 of the carrier wafer 10, which is placed on a turntable 100 mounted on a shaft 104. The polishing head 80 can have a diameter of 25 mm to 75 mm or 50 mm. Therefore, the polishing head 80 may have a smaller diameter than the carrier wafer 10.

[0047] In the operation of the polishing apparatus 56, the carrier wafer 10 is loaded into or on the turntable 100. In various examples, the first surface 18 of the carrier wafer 10 is exposed and faces the polishing head 80. On the other hand, the second surface 22 is positioned on the turntable 100. The carrier wafer 10 and / or the second surface 22 can be fixed in place by vacuum assistance or chuck. In the vacuum example, a vacuum can be generated between the second surface 22 and the turntable 100 so that the carrier wafer 10 is held in place. In the chuck example, a locking pin can be used that can grip the periphery of the carrier wafer 10 and / or connect to a groove in the 10.

[0048] Once the carrier wafer 10 is fixed to the turntable 100, the turntable 100 rises toward the polishing head 80 and begins to spin or rotate. The turntable 100 starts at a relatively slow revolutions per minute (RPM) in a low position and gradually increases in speed to bring the first surface 18 into contact with the polishing head 80. The polishing head 80 can be rotated at speeds of 3,000 RPM to 10,000 RPM using a polishing motor 96. In various examples, the polishing head 80 can be tilted relative to the first surface 18 of the carrier wafer 10 so that the polishing head 80 remains in contact with the first surface 18 while the polishing head 80 rotates around the carrier wafer 10. That is, the polishing head 80 is configured to tilt. In various examples, the polishing head 80 can be a ring with a hollow center so as to minimize the speed difference across the polishing head 80. A slurry containing one or more abrasives (i.e., having a smaller size than the abrasive used for lapping) is supplied to the interface between the first surface 18 and the polishing head 80. For example, the abrasive grain size used for lapping can be in the range of 5 μm to 20 μm, and the abrasive grain size used for polishing can be in the range of 3 μm or less. The polishing head 80 can utilize a mixture of CeO2 and a carrier medium (e.g., water) while polishing the first surface 18.

[0049] The relative position of the polishing head 80 and the first surface 18 of the carrier wafer 10 can be changed by translating the turntable 100 by moving the shaft 104 using a stepper motor 84 (i.e., the crankshaft 92 which moves the polishing head 80). The polishing head 80 can start by polishing the first surface 18 near the edge (i.e., the edge portion 30) and move toward the center (i.e., the center portion 26). Alternatively, the polishing head 80 can be understood to start polishing the first surface 18 at the center and move toward the edge.

[0050] As described above, the first surface 18 can be polished into a convex or concave shape by using a pressure difference, speed difference, or time difference between the center 26 and the edge 30. In the example of a pressure difference for a convex shape, the polishing pressure between the polishing head 80 and the first surface 18 increases as the polishing head 80 moves from the center 26 towards the edge 30. To produce a concave first surface 18, the polishing pressure between the polishing head 80 and the first surface 18 decreases as the polishing head 80 moves from the center 26 towards the edge 30. The polishing head 80 can reciprocate between the center 26 and the edge 30 of the carrier wafer 10 and / or move in a circular motion around the first surface 18 of the carrier wafer 10.

[0051] Depending on the degree of curvature (i.e., both convex and concave) of the first surface 18, the weights of the adjustable weight 88 and the counterweight 72 can be changed. By adding or subtracting the weight of the adjustable weight 88 and / or changing the weight of the counterweight 72, the force applied by the polishing head 80 to the first surface 18 of the carrier wafer 10 can be changed. By changing the force between the polishing head 80 and the carrier wafer 10 and the duration for which this force is applied, the amount of material that can be removed from the carrier wafer 10 can be changed, allowing the first surface 18 to be machined into the shape described above. That is, by applying differential polishing pressure across the first surface 18, the first surface 18 can be shaped into the above shape. Once the second surface 22 is positioned relative to the turntable 100, the second surface 22 can maintain the shape formed during step 44 (i.e., flat).

[0052] As used herein, the term “absolute pressure” is defined as the pressure applied by the polishing head 80 to any point on the first surface 18 of the carrier wafer 10. The absolute pressure applied to any point on the first surface 18 of the carrier wafer 10 is approximately 0.1 psi (approximately 690 Pa), 0.5 psi (approximately 3.45 kPa), 1 psi (approximately 6.9 kPa), or 2 psi (approximately 13.8 kPa), or 3 psi (approximately 20.7 kPa), or 4 psi (approximately 27.6 kPa), or 5 psi (approximately 34.5 kPa), or 6 psi (approximately 41.4 kPa), or 7 psi (approximately 48.3 kPa), or 8 psi (approximately 55.2 kPa), or 9 psi (approximately 62.1 kPa), or 10 psi (approximately 69 kPa), or 11 psi (approximately 75.9 kPa), or 12 psi (approximately It can be 82.8kPa, or 13psi (approximately 89.7kPa), or 14psi (approximately 96.6kPa), or 15psi (approximately 103.5kPa), or 16psi (approximately 110.4kPa), or 17psi (approximately 117.3kPa), or 18psi (approximately 124.2kPa), or 19psi (approximately 131.1kPa), or 20psi (approximately 138kPa), or 25psi (approximately 172.5kPa), or 30psi (approximately 207kPa), or any range having any two of these values ​​as endpoints, or any range having any one of these values ​​as an upper limit. For example, the absolute pressure applied to any one point on the first surface 18 of the carrier wafer 10 can be 0.5 psi (approximately 3.45 kPa) to 30 psi (approximately 207 kPa), or 0.5 psi (approximately 3.45 kPa) to 25 psi (approximately 172.5 kPa), or 0.5 psi (approximately 3.45 kPa) to 20 psi (approximately 138 kPa), or 1 psi (approximately 6.9 kPa) to 20 psi (approximately 138 kPa), or 1 psi (approximately 6.9 kPa) to 15 psi (approximately 103.5 kPa), or 1 psi (approximately 6.9 kPa) to 10 psi (approximately 69 kPa), or 1 psi (approximately 6.9 kPa) to 5 psi (approximately 34.5 kPa).

[0053] As used herein, the term “pressure difference” is defined as the difference between the absolute pressures of the polishing head 80 at the lowest pressure point and the highest pressure point. The pressure difference is 0.1 psi (approximately 690 Pa) or 0.5 psi (approximately 3.45 kPa) or 1 psi (approximately 6.9 kPa) or 2 psi (approximately 13.8 kPa) or 3 psi (approximately 20.7 kPa) or 4 psi (approximately 27.6 kPa) or 5 psi (approximately 34.5 kPa) or 6 psi (approximately 41.4 kPa) or 7 psi (approximately 48.3 kPa) or 8 psi (approximately 55.2 kPa) or 9 psi (approximately 62.1 kPa) or 10 psi (approximately 69 kPa) or 11 psi (approximately 75.9 kPa) or 12 psi (approximately 82.8 kPa) or It can be 13 psi (approximately 89.7 kPa), 14 psi (approximately 96.6 kPa), 15 psi (approximately 103.5 kPa), 16 psi (approximately 110.4 kPa), 17 psi (approximately 117.3 kPa), 18 psi (approximately 124.2 kPa), 19 psi (approximately 131.1 kPa), 20 psi (approximately 138 kPa), 25 psi (approximately 172.5 kPa), or 30 psi (approximately 207 kPa), or any range having any two of these values ​​as endpoints, or any range having any one of these values ​​as an upper limit. For example, the pressure difference can be 0.5 psi (approximately 3.45 kPa) to 30 psi (approximately 207 kPa), or 0.5 psi (approximately 3.45 kPa) to 25 psi (approximately 172.5 kPa), or 0.5 psi (approximately 3.45 kPa) to 20 psi (approximately 138 kPa), or 1 psi (approximately 6.9 kPa) to 20 psi (approximately 138 kPa), or 1 psi (approximately 6.9 kPa) to 15 psi (approximately 103.5 kPa), or 1 psi (approximately 6.9 kPa) to 10 psi (approximately 69 kPa), or 1 psi (approximately 6.9 kPa) to 5 psi (approximately 34.5 kPa). In the example of the pressure difference, it should be understood that the pressure can be changed gradually between the highest and lowest pressure points of the first surface 18, rather than in steps.

[0054] In the example of a convex shape of the first surface 18, a low pressure may be applied to the center 26 of the carrier wafer 10, or it may not be subject to any pressure at all, while a higher pressure (e.g., 20 psi (approximately 138 kPa)) may be applied to the edge 30. In this example, the absolute pressure applied to the center 26 may be 0 psi (0 Pa) or 0.5 psi (approximately 3.45 kPa), and the absolute pressure applied to the edge 30 may be 20 psi (approximately 138 kPa). As a result, the pressure difference between the center 26 and the edge 30 is approximately 20 psi (approximately 138 kPa). It should be understood that the absolute pressure values ​​for the center portion 26 and the edge 30 can be reversed in the example of a concave shape of the first surface 18. Furthermore, it should be understood that any combination of the above absolute pressures can be used between the center 26 and the edge 30 to achieve the pressure difference without departing from the teachings provided herein.

[0055] In the example of step 52, which uses a speed difference to shape the first surface 18, the speed of the polishing motor 96 (i.e., the polishing head 80) can be adjusted to create a polishing difference between the center 26 and the edge 30. In the example of a convex shape, as the polishing head 80 moves from the center of the first surface 18 toward the edge, the speed of the polishing motor 96 can be increased so that more material is removed from the first surface 18 closer to the edge 30. In the example of a concave shape, as the polishing head 80 moves from the edge 30 of the first surface 18 toward the center 26, the speed of the polishing motor 96 can be increased so that more material is removed from the first surface 18 closer to the center 26.

[0056] As used herein, the term “absolute speed” is defined as the number of revolutions per minute at which the polishing head 80 is moving at any point on the first surface 18 of the carrier wafer 10. The absolute speed of the polishing head 80 at any point on the first surface 18 of the carrier wafer 10 can be 60 RPM, 100 RPM, 500 RPM, 1000 RPM, 2000 RPM, 3000 RPM, 4000 RPM, 5000 RPM, 6000 RPM, 7000 RPM, 8000 RPM, 9000 RPM, or 10000 RPM, or any range having any two of these values ​​as endpoints, or any range having any one of these values ​​as an upper limit. For example, the absolute velocity applied to any one point on the first surface 18 of the carrier wafer 10 can be 60 RPM to 10000 RPM, 3000 RPM to 10000 RPM, 4000 RPM to 9000 RPM, 5000 RPM to 8000 RPM, or 6000 RPM to 7000 RPM.

[0057] As used herein, the term “speed difference” is defined as the difference between the lowest speed point, the highest speed point, and the absolute speed of the polishing head 80. The speed difference may be 1 RPM, 10 RPM, 50 RPM, 100 RPM, 200 RPM, 300 RPM, 400 RPM, 500 RPM, 1000 RPM, 3000 RPM, 4000 RPM, 5000 RPM, 6000 RPM, 7000 RPM, 8000 RPM, or 9000 RPM, or any range having any two of these values ​​as endpoints, or any range having any one of these values ​​as an upper limit. For example, the velocity difference applied to any point on the first surface 18 of the carrier wafer 10 can be 10 RPM to 9000 RPM, 100 RPM to 8000 RPM, 1000 RPM to 7000 RPM, 2000 RPM to 6000 RPM, or 3000 RPM to 5000 RPM. In the example of velocity differences, it should be understood that the velocity can be gradually changed between the fastest and slowest velocity points on the first surface 18, rather than in steps.

[0058] In the example of step 52, which uses a time difference to shape the first surface 18, the residence time of the polishing head 80 on the center 26 relative to the edge 30 can be varied to preferentially remove material from the first surface 18. In the example of a convex shape, as the polishing head 80 moves from the center to the edge of the first surface 18, the residence time of the polishing head 80 on a certain point on the first surface 18 can be lengthened so that more material is removed from the first surface 18 closer to the edge 30. In the example of a concave shape, as the polishing head 80 moves from the edge 30 to the center 26 of the first surface 18, the residence time of the polishing head 80 on a certain point on the first surface 18 can be lengthened so that more material is removed from the first surface 18 closer to the center 26.

[0059] For the purposes of this disclosure, the term “absolute time” is the time that a point on the first surface 18 of the carrier wafer 10 is exposed to the polishing pad 80. The absolute time can be 1 second, 30 seconds, 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 120 minutes, or any range having any two of these values ​​as endpoints or any range having any one of these values ​​as an upper limit. For example, the absolute time can be 1 second to 120 minutes or 1 second to 60 minutes or 1 minute to 60 minutes or 10 minutes to 60 minutes or 10 minutes to 30 minutes or 10 minutes to 20 minutes. As used herein, the term “time difference” is defined as the difference between the absolute time spent by the polishing head 80 at the shortest time point and the absolute time spent at the longest time point. The time difference can be 1 second, 30 seconds, 1 minute, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 120 minutes, or any range having any two of these values ​​as endpoints or any range having any one of these values ​​as an upper limit. For example, the time difference can be 1 second to 60 minutes or 1 minute to 60 minutes or 10 minutes to 60 minutes or 10 minutes to 30 minutes or 10 minutes to 20 minutes. In the examples of time differences, it should be understood that the time can be changed gradually between the longest time point and the shortest time point on the first surface 18, rather than stepwise.

[0060] In the example of a convex shape of the first surface 18, the absolute time the polishing head 80 is applied to the center 26 of the carrier wafer 10 can be shorter, while the absolute time the polishing head 80 is applied to the edge 30 can be longer. In such an example, the absolute time the polishing head 80 is applied to the center 26 can be between 1 second and 1 minute, and the absolute time for the edge 30 can be 60 minutes. As a result, the time difference between the center 26 and the edge 30 is approximately 60 minutes. It should be understood that the absolute time values ​​for the center 26 and the edge 30 can be reversed in the example of a concave shape of the first surface 18.

[0061] After step 52 of polishing the first surface 18, the carrier wafer 10 may have a curved (i.e., convex or concave) first surface 18. As described above, a curved first surface 18 can be advantageous in that it is configured to undergo a finish polishing step against a substantially flat first surface 18. Such a feature can be advantageous in that the carrier wafer 10 can be sold to a customer as is (i.e., after step 52) or transported in some way, and when the customer performs a finish polishing step (i.e., to clean or smooth the carrier wafer 10), the first surface 18 is substantially flat and ready for immediate use. In yet another example, the carrier wafer 10 can then be stored or otherwise maintained, and the finish polishing step can be performed by the manufacturer of the carrier wafer 10. That is, the next step 110 after polishing step 52 is to finish polish the center 26 and edges 30 of the first surface 18 to a substantially flat shape. During the finishing polishing step 110, at least one of the carrier wafer 10 and the polishing pad is rotated relative to each other so that the center 26 and edges 30 of the first surface 18 are polished simultaneously at different speeds. Step 110 can be performed by either the original manufacturer of the carrier wafer 10 or a subsequent user or customer. The polishing pad can be a component of a chemical, mechanical, and / or chemomechanical polishing step. In chemomechanical polishing, an abrasive and a corrosive chemical slurry (e.g., colloid) are used on the carrier wafer 10 along with the polishing pad. The polishing pad is pressed against the first surface 18 of the carrier wafer 10 and rotated to polish the first surface 18. According to various examples, the polishing pad is rotated around different axes of rotation (i.e., not concentric) so that material is removed from the first surface 18. In addition to or instead of rotating the polishing pad, the carrier wafer 10 may also be rotated so that relative motion between the polishing pad and the first surface 18 is achieved.

[0062] As a result of step 110, polishing of the center 26 and edge 30 of the first surface 18 occurs simultaneously at different speeds so that the first surface 18 is polished to a substantially flat shape. As described above, the first surface 18 of the carrier wafer 10 can be convex or concave, and these shapes result in variations in total thickness between the center 26 and the edge 30, respectively. In the example of a convex shape of the first surface 18, when the polishing pad of chemical mechanical polishing contacts the first surface 18, the relatively high center 26 of the first surface 18 is preferentially polished by the polishing pad due to the increased force associated with the rise of the center 26. The increased rise results in a greater force being applied to the center 26. As a result, the center 26 of the first surface 18 is polished at a faster speed than the edge 30. As described above, the relative heights of the center 26 and the edge 30 are adjusted so that the difference in polishing speed between the center 26 and the edge 30 results in a substantially flat first surface 18.

[0063] Similar to the example of the convex shape of the first surface 18, the example of the concave shape of the first surface 18 also utilizes the advantage of the polishing speed difference to produce a substantially flat first surface 18. In the example of the concave shape, the edges 30 of the first surface 18 rise relative to the center 26. As a result, the edges 30 are polished preferentially at a faster speed than the center 26. Thus, due to the concave shape of the first surface 18, the polishing speed difference between the center 26 and the edges 30 results in a substantially flat first surface 18.

[0064] Once the first surface 18 is polished to a substantially flat shape, the first surface 18 can be cleaned and prepared for subsequent use of the carrier wafer 10. According to various examples, the carrier wafer 10 can be used as a carrier for a silicon wafer. In such examples, the silicon wafer can be bonded (e.g., reversibly or irreversibly) to the first surface 18 of the carrier wafer 10. In such examples, a first surface 18 that is very uniformly flat can be advantageous.

[0065] The use of this disclosure can offer various advantages. First, the method 40 and polishing apparatus 56 described above can be used for both silicon wafers and optical lenses. For example, since both silicon wafers and optical lenses often undergo additional polishing steps by the customer, using the above disclosure can enable downstream manufacturing techniques that result in higher yields. Also, conventional manufacturing techniques often result in conventional substrates having irregular surfaces, and by providing a carrier wafer 10 having a known curvature configured to produce a substantially flat first surface 18, the complexity associated with correcting the irregular surface of conventional substrates can be reduced.

[0066] Secondly, by using method 40 and the polishing apparatus 56, the total thickness variation, total display reading, local focal plane deviation, and local thickness variation of the carrier wafer 10 can be reduced and / or eliminated. For example, the above-mentioned potential defects of the carrier wafer 10 can be reduced by lapping the first surface 18 and the second surface 22, and then polishing the first surface 18 with the polishing apparatus 56.

[0067] Thirdly, the use of the polishing apparatus 56 enables flexible and precise control of the first surface 18 of the carrier wafer 10. With conventional substrates, it can be difficult to cut and polish the substrate to the appropriate profile. By using the polishing apparatus 56 and its adjustable weight 88 disclosed herein, precise control of the first surface 18 becomes possible.

[0068] Fourth, the polishing apparatus 56 provides a low-cost fixture for polishing the carrier wafer 10. For example, by using an adjustable weight 88, a lever 64 and a counterweight 72, a simple, adjustable, and mechanically robust method is provided for adjusting the force that the polishing head 80 applies to the carrier wafer 10, thereby allowing a pressure difference to be applied to the first surface 18 of the carrier wafer 10.

[0069] Fifth, the polishing apparatus 56 provides a system that can be scaled up to improve the production of carrier wafers 10. For example, multiple polishing heads 80 can be mounted on a single polishing apparatus 56, and / or the number of carrier wafers 10 produced simultaneously can be increased by utilizing multiple polishing apparatuses 56.

[0070] Sixth, since the lapping of the carrier wafer 10 performed in step 44 can produce a very uniform first surface 18 and / or second surface 22, a high yield of the carrier wafer 10 can be achieved by supplying a very homogeneous material to the polishing apparatus 56.

[0071] Modifications to this disclosure will be conceivable to those skilled in the art and to those who manufacture or use this disclosure. Accordingly, it will be understood that the embodiments shown in the drawings and described above are for illustrative purposes only and are not intended to limit the scope of this disclosure as defined by the following claims, to be interpreted in accordance with the principles of patent law, including the doctrine of equivalents.

[0072] Those skilled in the art will understand that the configurations of the disclosed features and other components are not limited in any way to specific materials. Other exemplary embodiments of the disclosures disclosed herein may also be formed from a wide range of materials unless otherwise specified herein.

[0073] Any method or step described herein can be combined with other disclosed methods or steps to form a structure within the scope of this disclosure. The exemplary structures and methods disclosed herein are for illustrative purposes only and should not be construed as limiting.

[0074] Furthermore, it should be understood that modifications and alterations may be made to the aforementioned structures and methods without departing from the concepts of this disclosure, and that these concepts are intended to be included in the claims below, to the extent that otherwise such claims are specified in the same wording.

[0075] Preferred embodiments of the present invention are described below in separate sections.

[0076] Embodiment 1 A method for manufacturing a carrier wafer, A step of wrapping the first and second surfaces of a carrier wafer, which includes glass, glass ceramic, or ceramic material, so that the carrier wafer is substantially flat, wherein, after the wrapping step, the carrier wafer has a diameter of 250 mm to 450 mm and a thickness of 0.5 mm to 2 mm, The first surface of the carrier wafer is polished by a pressure difference, speed difference, or time difference between the center and edge of the carrier wafer, such that the first surface has a convex or concave shape. Methods that include...

[0077] Embodiment 2 The method according to Embodiment 1, wherein the step of polishing the first surface of the carrier wafer includes a step of polishing the first surface of the carrier wafer with a pressure difference between the center and the edge, and further wherein the pressure difference is 5 psi (approximately 34.5 kPa) to 20 psi (approximately 138 kPa).

[0078] Embodiment 3 The method according to Embodiment 1 or 2, wherein the first surface of the carrier wafer is polished to a substantially flat shape through a finish polishing step performed after the polishing step.

[0079] Embodiment 4 The method further includes, after the polishing step, a step of finishing and polishing the central and edge portions of the first surface to a substantially flat shape. During the finish polishing step, at least one of the carrier wafer and the polishing pad is rotated relative to each other so that the center and the edges of the first surface are polished simultaneously at different speeds. The method according to Embodiment 1 or 2.

[0080] Embodiment 5 A method according to any one of embodiments 1 to 4, wherein a convex shape is defined by the step of polishing the first surface of the carrier wafer.

[0081] Embodiment 6 The method according to any one of embodiments 1 to 4, wherein a concave shape is defined by the step of polishing the first surface of the carrier wafer.

[0082] Embodiment 7 The method according to any one of embodiments 1 to 6, wherein the step of polishing the first surface further includes the step of rotating a polishing head relative to the first surface of the carrier wafer.

[0083] Embodiment 8 The method according to any one of embodiments 1 to 7, wherein the first surface and the second surface are on opposite sides of the carrier wafer.

[0084] Embodiment 9 The method according to any one of embodiments 1 to 8, wherein the wrapping of the first surface and the wrapping of the second surface are performed substantially simultaneously.

[0085] Embodiment 10 The method according to any one of Embodiments 1 to 9, wherein, after performing the step of polishing the first surface of the carrier wafer with the pressure difference, the difference between the thickness of the center and the thickness of the edge of the carrier wafer is 1 μm to 5 μm.

[0086] Embodiment 11 The method according to any one of embodiments 1 to 10, wherein the carrier wafer is substantially circular.

[0087] Embodiment 12 The method according to Embodiment 11, wherein the carrier wafer has an outer diameter of 200 mm to 400 mm.

[0088] Embodiment 13 A polishing device, Adjustable weights, A polishing head connected to a motor, A turntable and The lever connected to the motor and the counterweight The motor and the counterweight are positioned at opposite ends of the lever's pivot point, A polishing device in which the adjustable weight and the counterweight are configured to change the force applied to the polishing head.

[0089] Embodiment 14 The polishing apparatus according to embodiment 13, wherein the pivot point of the lever is connected to a support structure.

[0090] Embodiment 15 The polishing apparatus according to embodiment 13 or 14, wherein the stepper motor is positioned on the adjustable weight.

[0091] Embodiment 16 The polishing apparatus according to any one of claims 13 to 15, wherein the polishing head is configured to be inclined.

[0092] Embodiment 17 It is a carrier wafer, It comprises a body that defines a first surface having a central part and an edge, and a second surface opposite to the first surface, The first surface defines a substantially convex or concave shape, and the second surface is substantially flat. A carrier wafer in which the first surface is configured to be polished to a substantially flat shape under different polishing speeds between the center and the edge.

[0093] Embodiment 18 The carrier wafer according to Embodiment 17, wherein the difference between the thickness of the central part of the carrier wafer and the thickness of the edge is 1 μm to 5 μm.

[0094] Embodiment 19 The carrier wafer according to embodiment 17 or 18, wherein the carrier wafer includes glass.

[0095] Embodiment 20 The carrier wafer according to any one of claims 17 to 19, wherein the first surface defines a concave shape.

Claims

1. A method for manufacturing a carrier wafer, A step of wrapping a first surface and a second surface of a carrier wafer, which includes glass, glass ceramic, or ceramic material, so that the carrier wafer is substantially flat, wherein, after the wrapping step, the carrier wafer has a diameter of 250 mm to 450 mm and a thickness of 0.5 mm to 2 mm, The first surface of the carrier wafer is polished by a pressure difference, speed difference, or time difference between the center and edge of the carrier wafer, such that the first surface has a convex or concave curve shape. Includes, A method comprising the step of polishing the first surface of the carrier wafer, wherein the total thickness variation across the first surface having a convex or concave curve shape is 1 μm to 5 μm.

2. The method according to claim 1, wherein the step of polishing the first surface of the carrier wafer includes a step of polishing the first surface of the carrier wafer with a pressure difference between the center and the edge, and further wherein the pressure difference is 5 psi (about 34.5 kPa) to 20 psi (about 138 kPa).

3. The method according to claim 1 or 2, wherein the first surface of the carrier wafer having the convex or concave curve shape is polished to a substantially flat shape through a finish polishing step performed after the polishing step.

4. The method further includes, after the polishing step, a step of finishing and polishing the central and edge portions of the first surface having the convex or concave curve shape to a substantially flat shape, During the finish polishing step, at least one of the carrier wafer and the polishing pad is rotated relative to each other so that the center and the edges of the first surface having the convex or concave curve shape are polished simultaneously at different speeds. The method according to any one of claims 1 to 3.

5. The method according to any one of claims 1 to 4, wherein a convex curve shape is defined by the step of polishing the first surface of the carrier wafer.

6. The method according to any one of claims 1 to 4, wherein a concave curve shape is defined by the step of polishing the first surface of the carrier wafer.

7. The method according to any one of claims 1 to 6, wherein the carrier wafer is substantially circular.

8. It is a carrier wafer, It comprises a body that defines a first surface having a central part and an edge, and a second surface opposite to the first surface, The first surface defines a substantially convex or concave curve shape, and the second surface is substantially flat. A carrier wafer in which the total thickness variation across the first surface defining the convex or concave curve shape is 1 μm to 5 μm.

9. The carrier wafer according to claim 8, wherein the carrier wafer includes glass.

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