Method for manufacturing substrate, and grinding device

Abstract

This method for manufacturing a substrate is applied to a grinding device having a grindstone capable of rotationally grinding the substrate. In this method, a surface of a bonded substrate obtained by bonding a plurality of substrates is ground, at least one among the bonded substrate and the grindstone is relatively inclined, and an outer peripheral portion on the surface side of the bonded substrate is ground.

Description

Substrate manufacturing method and grinding device

[0001] The technology of the present disclosure relates to a substrate manufacturing method and a grinding apparatus.

[0002] BACKGROUND ART When manufacturing substrates including semiconductor wafers typified by silicon wafers, it has been conventional to grind the front or back surface of the substrate using a grinding device in order to flatten the front or back surface of the substrate.

[0003] For example, Japanese Patent Application Laid-Open No. 2016-201422 discloses a grinding device that grinds a wafer mounted on a rotatable chuck table using a grinding wheel rotatably arranged on the chuck table. This grinding device measures the thickness profile of the wafer before grinding, adjusts the tilt amount of the chuck table and the grinding wheel based on the measurement results, and grinds the wafer by pressing the arc-shaped edge of the grinding wheel against the wafer.

[0004] By the way, a bonded substrate formed by bonding a plurality of substrates is known. One method for manufacturing such a bonded substrate is to form an insulating film, for example, a silicon oxide film (SiO ２ A known method involves bonding one semiconductor wafer on which a thin film (film) is formed to another semiconductor wafer, and then thinning the semiconductor wafer on which elements are to be fabricated to form a thinned layer. In the above-described method, a grinding device is often used to thin the wafer on which elements are to be fabricated of the bonded substrate. Grinding using such a grinding device is usually performed so that the surface of the wafer on which elements are to be fabricated is flat. However, even if the surface of the wafer is flat, the thickness of the thinned device fabrication layer may not be uniform.

[0005] In view of the above-mentioned problems, the present disclosure provides a substrate manufacturing method and a grinding apparatus that can make the thickness of a thin film in a bonded substrate uniform.

[0006] A substrate manufacturing method according to a first aspect of the present disclosure is a substrate manufacturing method that is applied to a grinding device having a grinding wheel capable of rotary grinding a substrate, and includes a step of grinding the surface of a bonded substrate formed by bonding a plurality of substrates together, and a step of tilting at least one of the bonded substrates and the grinding wheel relative to one another to grind the outer periphery of the surface side of the bonded substrate.

[0007] In such a method for manufacturing a substrate, by grinding the outer periphery on the front surface side of the bonded substrate separately from the front surface, it is possible to reduce variations in thickness that occur between the center and outer periphery of the bonded substrate, particularly the substrate on the front surface side of the bonded substrate.

[0008] A substrate manufacturing method according to a second aspect of the present disclosure is the substrate manufacturing method according to the first aspect of the present disclosure, wherein in the step of grinding the outer periphery, the bonded substrate and the grinding wheel are tilted in a direction that moves them apart relative to each other.

[0009] In this method of manufacturing a substrate, it is easy to adjust the contact pressure acting on the bonded substrate when tilting the bonded substrate or the grindstone to grind the outer periphery of the front surface side of the bonded substrate, and therefore the degree of grinding can be stably controlled.

[0010] A substrate manufacturing method according to a third aspect of the present disclosure is the substrate manufacturing method according to the first or second aspect of the present disclosure, wherein in the step of grinding the surface, the grinding wheel is fed relative to the bonded substrate to a first position where the bonded substrate is ground by the grinding wheel to a first thickness, and the feeding relative to the bonded substrate is stopped, and in the step of grinding the outer periphery, the bonded substrate and the grinding wheel are tilted in a direction separating them from each other when the feeding of the grinding wheel is stopped.

[0011] In such a method for manufacturing a substrate, grinding of the outer periphery on the front surface side of the bonded substrate stack is carried out during grinding in spark-out, so that grinding of the bonded substrate stack can be completed in a short time.

[0012] A substrate manufacturing method according to a fourth aspect of the present disclosure is the substrate manufacturing method according to the third aspect of the present disclosure, wherein the step of grinding the outer periphery further includes a step of feeding the grinding wheel against the bonded substrate to a second position where the bonded substrate is ground by the grinding wheel to a second thickness, stopping the feeding of the bonded substrate, and grinding the outer periphery of the bonded substrate.

[0013] In such a method for manufacturing a substrate, the amount of grinding of the outer periphery on the front surface side of the bonded substrate can be freely adjusted.

[0014] A grinding device according to a fifth aspect of the present disclosure includes a rotatable holding unit that holds a substrate, a grinding unit having a grinding wheel that can rotatably grind the substrate, a feeding unit that feeds the grinding unit toward the holding unit, and a control unit that controls the holding unit, the grinding unit, and the feeding unit, wherein the control unit grinds the surface of a bonded substrate formed by bonding multiple substrates held by the holding unit with the grinding unit, and tilts at least one of the bonded substrate held by the holding unit and the grinding wheel relative to one another to grind the outer periphery of the surface side of the bonded substrate with the grinding unit.

[0015] Such a grinding device can grind not only the surface of the bonded substrate but also the outer periphery on the surface side, thereby reducing the variation in thickness that occurs between the center and outer periphery of the bonded substrate, particularly the substrate on the surface side of the bonded substrate.

[0016] According to the substrate manufacturing method and grinding apparatus of the present disclosure, it is possible to make the thickness of the thin film in the bonded substrate uniform.

[0017] 6 is a flowchart showing an example of a manufacturing process for a bonded substrate. FIG. 2 is an explanatory diagram schematically illustrating the manufacturing process shown in FIG. 1 ... enlarged view of a portion A of FIG. 2A. FIG. 2 is an enlarged view of a portion B of FIG. 2C. FIG. 2 is an enlarged view of a portion C of FIG. 2D. FIG. 2 is a schematic side view showing an example of a grinding apparatus according to an embodiment. FIG. 5 is a schematic plan view of the grinding apparatus shown in FIG. 5. FIG. 6 is a cross-sectional view taken along line D-D of FIG. 6. FIG. 7 is a flowchart showing an example of a manufacturing method for a substrate according to an embodiment. FIG. 8 is an explanatory diagram showing an example of the operation of the grinding apparatus in the manufacturing method for the substrate shown in FIG. 8. FIG. 8 is a graph showing the transition of the height position of the grinding stone and the thickness of the substrate in the manufacturing method for the substrate shown in FIG. 8. FIG. 9 is a graph showing the transition of the height position of the grinding stone and the thickness of the substrate in a manufacturing method for a substrate according to a modified example.

[0018] This application is based on Japanese Patent Application No. 2024-146657, filed on August 28, 2024, in Japan, the contents of which are incorporated herein by reference. The present disclosure will become more fully understood from the following detailed description. Further scope of application of the present application will become apparent from the following detailed description. However, the detailed description and specific examples are preferred embodiments of the present disclosure and are set forth for illustrative purposes only. From this detailed description, various changes and modifications will be apparent to those skilled in the art within the spirit and scope of the present disclosure. The applicant does not intend to dedicate any of the described embodiments to the public, and the applicants also consider disclosed modifications and alternatives, even if not literally included within the scope of the claims, to be part of the invention under the doctrine of equivalents. Like reference numbers and names in the various drawings indicate like elements.

[0019] Hereinafter, each embodiment for carrying out the present disclosure will be described with reference to the drawings. Note that the scope necessary for the explanation to achieve the object of the present disclosure will be schematically shown below, and the scope necessary for explaining the relevant parts of the present disclosure will be mainly explained, and the parts for which explanation is omitted will be referred to as publicly known technologies. Furthermore, identical or similar reference numerals will be used to refer to identical or corresponding components in the drawings, and redundant explanations will be omitted. Furthermore, when a plurality of identical or corresponding components are included in a drawing, only some of them may be referenced to make the drawing easier to understand.

[0020] Fig. 1 is a flowchart showing an example of a manufacturing process for a bonded substrate. Figs. 2A to 2D are explanatory views that schematically explain the manufacturing process shown in Fig. 1. An example of a manufacturing process for a bonded substrate W will be described below with reference to Fig. 1 and Figs. 2A to 2D.

[0021] In manufacturing the bonded substrate W, first, a first substrate W1 containing, for example, silicon (Si) is prepared, and a layer of, for example, silicon dioxide (SiO ２ ) is deposited (step S01). The specific deposition method for the insulating film 100 can be appropriately selected from well-known deposition methods such as sputtering, CVD (chemical vapor deposition), and thermal oxidation, depending on the material of the insulating film 100 itself and the material of the first substrate W1. For example, when the insulating film 100 is made of silicon dioxide, a thermal oxidation method can be used. The materials of the first substrate W1 and the insulating film 100 are not particularly limited.

[0022] 2A, it is preferable to trim the edge portion of the first substrate W1 to form a step 110. By performing so-called edge trimming in this manner, it is possible to prevent edge chipping and cracking of the first substrate W due to edge chipping.

[0023] After the insulating film 100 is formed on the first substrate W1, the insulating film 100 is then polished (step S02) to planarize the surface of the insulating film 100. When polishing the insulating film 100, for example, a polishing process using a chemical mechanical polishing or chemical mechanical planarization (CMP) device can be used.

[0024] After the planarization of the insulating film 100 is completed, a second substrate W2 is prepared, which functions as a base material for the bonded substrate W. The second substrate W2 can be made of the same material as the first substrate W1. The surface of the second substrate W2 can also be made of a material such as SiO ２ 2B, the first substrate W1 is bonded to the surface of the second substrate W2 by overlapping the first substrate W1 with the insulating film 100 abutting the insulating film 101 of the second substrate W2 (step S03). In this bonding, the first substrate W1 and the second substrate W2 may be bonded via an adhesive layer 130, such as SiCN. Alternatively, heat treatment may be performed to chemically bond the insulating films 100 and 101. The adhesive layer 130 is only shown in FIGS. 2C and 2D, and is omitted in the other figures.

[0025] Next, a bonded substrate W (see FIG. 2C ) obtained by bonding the first and second substrates W1 and W2 through the above-described processes is subjected to a thinning process to form a thinned layer 120 of the first substrate W1 (step S04). In this embodiment, the thinned layer 120 is formed by mainly grinding the first substrate W1 located on the surface of the bonded substrate W using a grinding device, more specifically, a grinding device 1 described later. When grinding of the first substrate W1 is completed, a bonded substrate W having the thinned layer 120 on the surface and an insulating film layer inside is obtained (see FIG. 2D ).

[0026] Incidentally, in the bonded substrate W obtained by the above-described series of processes, there was a tendency for local variations in the thickness of the thinned layer 120. It was found that this tendency is related to the precision of planarization of the insulating film 100 of the first substrate W1.

[0027] 3 is an enlarged view of portion A in FIG. 2A. In step S01, the insulating film 100 formed on the first substrate W1 by thermal oxidation or the like varies in thickness. Therefore, in the subsequent step S02, a polishing process, for example, is performed to flatten the insulating film. This polishing process is performed using a CMP apparatus or the like. During this polishing process, so-called edge sagging, in which the thickness of the insulating film formed on the substrate is thinner at the outer periphery than at the inner periphery, can occur. If edge sagging occurs during polishing of the insulating film 100, the thickness of the outer periphery 102 of the insulating film 100 becomes thinner than the thickness of the central portion 103 of the insulating film 100, as shown in FIG. 3.

[0028] 4A is an enlarged view of portion B in FIG. 2C. Also, FIG. 4B is an enlarged view of portion C in FIG. 2D. The first substrate W1, on which the insulating film 100 including the edge sagging described above has been formed, is superimposed on the second substrate W2 in step S03. At this time, the outer peripheral portion 102 of the insulating film 100 is bonded to the surface of the insulating film 101, similarly to the central portion 103 of the insulating film 100. During this bonding, the outer peripheral portion of the first substrate W1 corresponding to the outer peripheral portion 102 is pulled toward the second substrate W2 more than the central portion of the first substrate W1, as shown in FIG. 4A. Therefore, the bonded first substrate W1 has a shape in which its outer peripheral portion is curved toward the second substrate W2.

[0029] When the first substrate W1 of the above-described stacked substrates is ground in step S04 to form a bonded substrate W, as shown in Fig. 4B, the outer circumferential portion 121 of the thinned layer 120 becomes thicker than the central portion 122 of the thinned layer 120. In this embodiment, a substrate manufacturing method and a grinding apparatus are provided that are capable of suppressing variations in the thickness of the thinned layer 120 caused by the factors described above.

[0030] Fig. 5 is a schematic side view showing an example of a grinding apparatus according to an embodiment. Fig. 6 is a schematic plan view of the grinding apparatus shown in Fig. 5. The grinding apparatus 1 according to this embodiment can be configured as a surface grinding apparatus that can grind a bonded substrate W by aligning a grinding stone substantially parallel to the bonded substrate W to be ground during grinding.

[0031] As shown in Figures 5 and 6, the grinding apparatus 1 of this embodiment includes a wafer chuck 3 as an example of a rotatable holding unit that holds the bonded substrate W, a grinding unit 2 that grinds the bonded substrate W, a spindle feed mechanism 23 as an example of a feed unit that feeds the grinding unit 2 toward the bonded substrate W, and a control unit 8 that controls the above-mentioned respective units.

[0032] The grinding apparatus 1 can manufacture a bonded substrate W including a thinned layer 120 by grinding the surface of a bonded substrate W made by overlapping a first substrate W1 and a second substrate W2 in the grinding unit 2. The grinding unit 2 includes a grinding wheel 21 that is capable of rotary grinding at least the bonded substrate W. The grinding apparatus 1 may further include a spindle 22 having the grinding wheel 21 attached to its tip, and a spindle feed mechanism 23 that feeds the spindle 22 to which the grinding wheel 21 is attached in the vertical direction V.

[0033] The grindstone 21 may be attached horizontally to the tip of the spindle 22. When the grindstone 21 is pressed against the bonded substrate W, it grinds the surface of the bonded substrate W. Hereinafter, the arc-shaped range in which the grindstone 21 grinds the bonded substrate W is referred to as a "grinding region A1."

[0034] The spindle 22 can rotate the grindstone 21 in a rotation direction C1 around a rotation axis a1 by a motor (not shown).

[0035] The spindle feed mechanism 23 may include two linear guides 23a that connect the column 4 and the spindle 22, and a known ball screw slider mechanism (not shown) that raises and lowers the spindle 22 in the vertical direction V. Hereinafter, the feed direction in which the linear guides 23a raise and lower the spindle 22 will be referred to as the "roll axis Z." The grinding unit 2 is provided with a pitch axis direction X1 that connects the linear guides 23a arranged side by side and perpendicular to the roll axis Z, and a yaw axis Y1 that is perpendicular to the roll axis Z and passes through the center of rotation O1 of the grinding wheel 21.

[0036] A wafer chuck 3, which is an example of a holder, is disposed below the grinding unit 2. Although only one wafer chuck 3 is shown in Fig. 5, the grinding apparatus 1 is preferably provided with a plurality of wafer chucks 3 in order to continuously grind a plurality of bonded substrates W. The plurality of wafer chucks 3 may be disposed at predetermined intervals on a circumference centered on the rotation axis of the index table 5. The wafer chuck 3 may include a chuck 31 and an air bearing 32.

[0037] The chuck 31 may have an adsorbent (not shown) made of a porous material such as alumina embedded on its upper surface. The wafer chuck 3 may include a conduit (not shown) that passes through the chuck 31 and the air bearing 32 and extends to the surface of the chuck 31. This conduit may be connected to a vacuum source, a compressed air source, and a water supply source (also not shown) via a rotary joint (not shown) connected to the rotor 32a of the air bearing 32. When the vacuum source is activated, the bonded substrate W placed on the chuck 31 is adsorbed and held by the chuck 31. When the compressed air source or the water supply source is activated, the adsorption between the bonded substrate W and the chuck 31 is released.

[0038] The air bearing 32 may include a rotor 32a rotatable around a rotation axis a2 and a stator 32b disposed on the outer periphery of the rotor 32a. The rotor 32a and the chuck 31 may be fixed together by a fastening means such as bolts (not shown). The rotor 32a is connected to a rotary joint and rotates the chuck 31 in a rotation direction C2 around the rotation axis a2. A predetermined gap (air gap) is provided between the rotor 32a and the stator 32b. By supplying compressed air to this gap from the outside, the rotor 32a can rotate without contacting the stator 32b. The wafer chuck 3 has a yaw axis Y2 that is perpendicular to the roll axis Z and passes through the rotation center O2 of the wafer chuck 3. The yaw axis Y2 of the wafer chuck 3 is parallel to the yaw axis Y1 of the grinding unit 2. Furthermore, the grinding unit 2 and the wafer chuck 3 may be disposed so that the yaw axis Y1 of the grinding unit 2 and the yaw axis Y2 of the wafer chuck 3 are spaced apart by ¼ of the diameter of the wafer chuck 3. Therefore, the grinding area A1 is formed symmetrically on both sides of the yaw axis Y1, and the pitching component of the grinding area A1 is set to the minimum necessary.

[0039] Furthermore, the grinding region A1 is preferably formed from the center of the bonded substrate stack W toward the outer periphery of the bonded substrate stack W. This makes it possible to suppress edge chipping when the peripheral edge of the bonded substrate stack W comes into contact with the grindstone 21.

[0040] Fig. 7 is a cross-sectional view taken along line II in Fig. 6. As shown in Fig. 7, the grinding apparatus 1 may include a tilting unit 6 that tilts the rotation axis a2 of the wafer chuck 3 with respect to the rotation axis a1 of the grinding wheel 21, as an example of a configuration for changing the relative angle between the grinding wheel 21 and the bonded substrate W. The tilting unit 6 may include a tilt table 61, a fixed support unit 62, an upstream movable support unit 63, and a downstream movable support unit 64. Note that Fig. 7 does not illustrate the grinding unit 2, and the wafer chuck 3 is shown in a front view.

[0041] 6, the tilt table 61 may be formed in a substantially triangular shape in plan view. In the tilt table 61 of this embodiment, a fixed support part 62, an upstream movable support part 63, and a downstream movable support part 64 are arranged 120 degrees apart on a circumference of a circle centered on the rotation axis a2.

[0042] The fixed support part 62 may be fastened to the tilt table 61 by a bolt 62a. The fixed support part 62 is fixed at least in its position in the vertical direction.

[0043] The upstream-side movable support part 63 is a movable support part that is arranged upstream of the fixed support part 62 in the rotation direction C2 of the wafer chuck 3. The structure of the upstream-side movable support part 63 may be similar to that of the downstream-side movable support part 64. Therefore, the structure of the upstream-side movable support part 63 will be explained below in the same manner as the structure of the downstream-side movable support part 64, and redundant explanations will be omitted.

[0044] The downstream-side movable support part 64 is a movable support part arranged downstream of the fixed support part 62 in the rotation direction C2 of the wafer chuck 3. As shown in Fig. 7, the downstream-side movable support part 64 may include a nut 64a embedded in the tilt table 61, a tilt ball screw 64b fixed to the index table 5 and having an upper part that screws into the nut 64a, and a tilt motor 64c that rotates the tilt ball screw 64b. The downstream-side movable support part 64 is formed longer in the vertical direction V than the fixed support part 62.

[0045] Regarding the inclined portion 6 described above, it is preferable to incline the wafer chuck 3 so that the grinding stone 21 and the bonded substrate W are parallel, taking into consideration the axial tilt of the grinding portion 2 resulting from the rotational moment around the linear guide 23a due to the weight of the grinding portion 2. The grinding portion 2, which is cantilevered by the column 4, may tilt due to its own weight, and if grinding is performed with the grinding portion 2 tilted in this manner, there is a risk that the grinding stone 21 will make one-sided contact with the bonded substrate W. Therefore, it is preferable to tilt the tilt table 61 by the same angle as the tilt angle of the grinding portion 2.

[0046] In this embodiment, one of the plurality of support structures is the fixed support part 62, but the fixed support part 62 may be changed to a movable support part, and the wafer chuck 3 and the bonded substrate W supported by the wafer chuck 3 may be tilted by selectively fixing or operating three movable support parts. The number of fixed support parts and movable support parts used in the grinding apparatus 1 is not limited to three, and may be four or more. Furthermore, the grinding apparatus 1 may include a scale 7 for measuring the amount of sinking of the tilt table 61 due to the load when the grinding part 2 presses the bonded substrate W.

[0047] In addition, although the present embodiment has been described with reference to an example in which the wafer chuck 3 is tilted relative to the grinding wheel 21 by the tilting portion 6, the present disclosure is not limited to this. For example, instead of or in addition to the tilting portion 6, a tilting means for tilting the grinding wheel 21 relative to the bonded substrate W held by the wafer chuck 3 can be employed.

[0048] Various operations of the grinding apparatus 1 of this embodiment are controlled by a control unit 8. This control unit 8 can control each of the components constituting the grinding apparatus 1. The control unit 8 can be configured, for example, by a well-known computer. In detail, the control unit 8 may include at least a processor 81 and a memory 82.

[0049] The processor 81 may be configured by, for example, a CPU (Central Processing Unit). The processor 81 may be capable of controlling each of the components of the grinding device 1 by transmitting control signals to the components based on control commands stored in the memory 82 or the like.

[0050] The memory 82 may be configured with a volatile or non-volatile memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The memory 82 may store a program or the like including a control command that can be executed by the processor 81 to control the grinding device 1.

[0051] The control unit 8 may have various interfaces, storages, etc. in addition to the above-mentioned processor 81 and memory 82. The control unit 8 controls the grinding device 1 so that the grinding unit 2 grinds the front surface of the bonded substrate W held on the wafer chuck 3, and tilts at least one of the bonded substrate W held on the wafer chuck 3 and the grinding wheel 21 relatively to one another, thereby grinding the outer periphery of the front surface side of the bonded substrate W with the grinding unit 2. A substrate manufacturing method of this embodiment, including the grinding process by the grinding device 1, will be described below.

[0052] The method for manufacturing a substrate according to this embodiment will be described below, mainly with reference to Figures 8 to 10. The method for manufacturing a substrate described below corresponds to the step of forming thinned layer 120 (more specifically, step S04 described above) in the series of bonded substrate manufacturing processes described above. Note that, although the following description will discuss a method for manufacturing a substrate using the grinding apparatus 1 described above, the grinding apparatus used is not particularly limited.

[0053] The substrate manufacturing method according to this embodiment can be mainly realized by the control unit 8 of the grinding apparatus 1 controlling each component. The substrate manufacturing method according to this embodiment can be provided in the form of a program or program product for causing the processor 81 of the control unit 8 to execute predetermined operations, or in the form of a non-transitory computer-readable recording medium storing the program. The effects described below also serve as explanations of the effects achieved by the grinding apparatus 1 according to this embodiment described above.

[0054] Fig. 8 is a flowchart showing an example of a method for manufacturing a substrate according to one embodiment. Also, Figs. 9A and 9B are operation explanatory diagrams showing an example of the operation of a grinding apparatus in the method for manufacturing a substrate shown in Fig. 8. Furthermore, Fig. 10 is a graph showing the change in the height position of the grinding stone and the change in the thickness of the substrate in the method for manufacturing a substrate shown in Fig. 8, in which line L1 in the figure shows the change in the height position of the grinding stone, and line L2 shows the change in the thickness of the bonded substrate W. Note that the grinding apparatus 1 shown in Figs. 9A and 9B schematically shows each component and operating distance to make its operation easier to understand.

[0055] The method for manufacturing a substrate according to this embodiment includes at least a step of grinding the surface of the bonded substrate W (corresponding to step S12 described later), and a step of tilting at least one of the bonded substrate W and the grindstone 21 relative to one another to grind the outer periphery of the surface side of the bonded substrate W (corresponding to step S13 described later). These steps will be described in detail below.

[0056] 8 to 10, in the method for manufacturing a substrate according to the present embodiment, first, a bonded substrate W, which is obtained by bonding a first substrate W1 and a second substrate W2 together and before the thinned layer 120 is formed, is held on a wafer chuck 3 (step S11). At this time, it is preferable to hold the bonded substrate W so that the surface of the bonded substrate W, in other words, the first substrate W1 side, is exposed above the wafer chuck 3.

[0057] Next, the grinding wheel 21 is brought into contact with the surface of the bonded substrate W to grind the entire surface of the bonded substrate W (step S12). The grinding performed here includes a process of feeding the grinding wheel 21 relative to the bonded substrate W up to a first position h2 where the bonded substrate W has a first thickness as a result of the grinding, and then stopping the feeding of the grinding wheel 21 relative to the bonded substrate W.

[0058] 10, the control unit 8 first operates the spindle feed mechanism 23 to move the grindstone 21, which is located at the initial position h1, in the direction of arrow M1 (see FIG. 9A). When this movement brings the grindstone 21 into contact with the surface of the bonded substrate W, the control unit 8 rotates the spindle 22 to start grinding the surface of the bonded substrate W. Note that the rotation of the spindle 22 may be started before the grindstone 21 comes into contact with the bonded substrate W.

[0059] When grinding the entire surface of the bonded substrate W, the control unit 8 controls the attitudes of the grinding stone 21 and the wafer chuck 3 so that the grinding stone 21 and the surface of the bonded substrate W maintain a substantially parallel attitude. Note that the relative angle between the grinding stone 21 and the surface of the bonded substrate W during grinding can be adjusted as appropriate, taking into account the grinding conditions, etc.

[0060] The degree of progress of the grinding is controlled by using a thickness sensor (not shown) to measure the thickness of the bonded substrate W. When the measurement result of the thickness sensor detects that the bonded substrate W, more specifically the first substrate W1 included in the bonded substrate W, has been ground to a predetermined thickness (for example, at time t2), the control unit 8 stops the spindle feed mechanism 23 to stop the grindstone 21 at the first position h2, thereby completing grinding of the entire surface of the bonded substrate W.

[0061] When grinding of the entire surface of the bonded substrate W is completed, the control unit 8 then grinds the entire periphery of the outer periphery on the front surface side of the bonded substrate W (step S13). In order to grind the outer periphery on the front surface side of the bonded substrate W, more specifically the entire periphery of the edge portion, the control unit 8 operates the tilting unit 6 to tilt the wafer chuck 3 and the bonded substrate W supported by the wafer chuck 3, as shown in FIG.

[0062] When grinding the edge portion of the bonded substrate W, tilting the bonded substrate W and the grinding wheel 21 in a direction that moves them apart relatively is preferable because the contact pressure between the grinding wheel 21 and the bonded substrate W is less likely to change and grinding can be performed stably. In this embodiment, in order to move the wafer chuck 3 and a portion of the bonded substrate W away from the grinding wheel 21, the control unit 8 operates the upstream movable support unit 63 and the downstream movable support unit 64 to move one of the tilt tables 61 in the direction of arrow M2. The tilt angle θ of the bonded substrate W with respect to the grinding wheel 21 is preferably adjusted to match the tilt angle θ caused by edge sagging of the outer peripheral portion 121 of the thinned layer 120 shown in FIG. 4B . The tilt angle θ may be adjusted depending on the degree of edge sagging and may be, for example, 0.001 to 0.01°.

[0063] It is preferable that data on the amount of grinding of the bonded substrate W corresponding to the tilt angle θ is stored in advance in the memory 82 of the control unit 8. By using such data, the thickness of the bonded substrate W before grinding or the thickness of the bonded substrate W during grinding can be measured, and the amount of grinding and the tilt angle θ can be adjusted from the difference between this thickness and the desired thickness of the bonded substrate W.

[0064] Upon completion of the above-described step S13, the feeding of the grinding stone 21 is stopped, and the grinding unit 2 performs spark-out (also called "zero cut"), a grinding operation that does not create a cut, for a predetermined time, for example, up to time t3. In this embodiment, the grinding of the edge portion shown in step S13 is performed by utilizing a grinding operation that progresses slightly during this spark-out period. Specifically, the control unit 8 performs the tilting operation of the bonded substrate W using the tilting unit 6 described above while the feeding of the grinding stone 21 is stopped and the grinding unit 2 is performing the spark-out operation. At this time, the rotation of the wafer chuck 3 may continue. Then, the outer periphery of the bonded substrate W is ground by utilizing the operation of the grinding stone 21 that progresses slightly from the first position h2 to the stop position h3 during the spark-out operation. By controlling the grinding of the outer periphery of the bonded substrate W during the spark-out operation in this manner, even when the variation in thickness of the thinned layer 120 due to edge sagging is relatively small, the edge portion can be ground with precision, and the variation in thickness of the thinned layer 120 can be suppressed.

[0065] As described above, according to the substrate manufacturing method and grinding apparatus 1 of the present embodiment, variations in the thickness of the thinned layer 120 caused by edge sagging in the insulating film can be suppressed by adding a process of grinding the outer periphery on the front surface side of the bonded substrate W. As a result, the length of the electrodes provided in the thinned layer 120 can be made constant, making it possible to uniformize the electrical characteristics of the first substrate W1. In addition, in the above example, the grinding of the outer periphery on the front surface side of the bonded substrate W is performed after the feeding of the grindstone 21 is stopped, so the grinding operation of the outer periphery on the front surface side of the bonded substrate W can be completed in a short time.

[0066] In the substrate manufacturing method according to the embodiment described above, the grinding of the outer periphery on the front surface side of the bonded substrate W is performed after stopping the feeding of the grinding wheel 21. On the other hand, for example, when the edge sagging generated in the insulating film 100 is relatively large, it may become necessary to grind the outer periphery on the front surface side of the bonded substrate W with a relatively large cutting depth. Therefore, as a modification of the embodiment described above, an example in which the grinding process of the outer periphery on the front surface side of the bonded substrate W is changed will be described below.

[0067] In this modified example, in addition to the above-described embodiment, the grindstone 21 is fed relative to the bonded substrate W to a second position h4 where the bonded substrate W has been ground by the grindstone 21 to a second thickness, and the feeding relative to the bonded substrate W is stopped, thereby performing a step of grinding the outer periphery of the bonded substrate W. Note that in this modified example, only the grinding process of the outer periphery on the front surface side of the bonded substrate W is different from that of the above-described embodiment. Therefore, the following description will mainly focus on the control content unique to this modified example, and a description of the control content common to the embodiment will be omitted.

[0068] 11 is a graph showing the change in height position of the grindstone and the change in substrate thickness in a substrate manufacturing method according to one modified example, in which line L3 indicates the change in height position of the grindstone and line L4 indicates the change in thickness of the bonded substrate W. In this substrate manufacturing method according to this modified example, as in the above-described embodiment, the control unit 8 holds the bonded substrate W on the wafer chuck 3, and then, at time t1, operates the spindle feed mechanism 23 to move the grindstone 21 located at the initial position h1. Then, the grindstone 21 is brought into contact with the bonded substrate W, and grinding of the surface of the bonded substrate W is initiated.

[0069] As the grinding of the surface of the bonded substrate W progresses, at a predetermined time t4 the bonded substrate W is ground to a predetermined thickness, the control unit 8 stops the spindle feed mechanism 23 to stop the grindstone 21 at the first position h2. The grindstone 21, whose feed has been stopped, starts a spark-out operation. During this spark-out operation, the thickness of the bonded substrate W becomes slightly thinner as the grindstone 21 advances slightly to a stop position h3.

[0070] The spark-out operation continues, and when a predetermined time t5 is reached, the control unit 8 operates the tilting unit 6 to tilt the wafer chuck 3 and the bonded substrate W supported by the wafer chuck 3 to a predetermined tilt angle θ in order to grind the entire outer periphery of the front surface side of the bonded substrate W.

[0071] When tilting of the bonded substrate W is completed at a predetermined time t6, the control unit 8 operates the spindle feed mechanism 23 to move the grindstone 21 until it reaches a second position h4, which is closer to the wafer chuck 3 than the first position h2. Here, the second position h4 is preferably adjusted so that the bonded substrate W has a second thickness. When the grindstone 21 reaches the second position h4 at time t7, the spindle feed mechanism 23 is stopped, and the spark-out operation is performed again until time t8. During this second spark-out operation, the thickness of the edge portion of the bonded substrate W becomes even thinner as the grindstone 21 advances slightly to the final stop position h5.

[0072] As described above, the substrate manufacturing method according to this modification can also be used when it is desired to grind the outer periphery on the front surface side of the bonded substrate W with a relatively large cutting depth, and can reliably suppress variations in the thickness of the thinned layer 120. Note that the bonded substrate W in the above-described embodiment and modification may be an SOI substrate.

[0073] The present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure. All of these modifications are included in the technical concept of the present disclosure. Furthermore, unless otherwise specified in the specification, each component of the present disclosure is not limited to one, and may be present in multiple forms.

[0074] All references, including publications, patent applications, and patents, cited in this specification are herein incorporated by reference to the same extent as if each reference was individually and specifically indicated to be incorporated by reference and set forth in its entirety herein.

[0075] The use of nouns and similar referents in connection with the description of this disclosure (particularly in connection with the claims that follow) shall be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The words "comprises," "has," "includes," and "comprises" shall be construed as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise noted. The recitation of numerical ranges herein is merely intended to serve as a shorthand method for individually referring to each value falling within the range, unless otherwise indicated herein, and each value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context. Any example or exemplary language used herein (e.g., "such as"), unless otherwise claimed, is intended merely to better illustrate the disclosure and does not pose a limitation on the scope of the disclosure. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the present disclosure.

[0076] Preferred embodiments of the disclosure are described herein, including the best mode known to the inventors for carrying out the disclosure. Variations of these preferred embodiments will become apparent to those skilled in the art upon reading the foregoing description. The inventor expects that skilled persons will apply such variations as appropriate, and intends to practice the disclosure otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, this disclosure includes any combination of the above-described elements in all variations thereof unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims

1. A method for manufacturing a substrate that is applicable to a grinding device having a grinding wheel capable of rotary grinding a substrate, the method comprising: a step of grinding the surface of a bonded substrate formed by bonding a plurality of substrates together; and a step of tilting at least one of the bonded substrates and the grinding wheel relative to one another to grind the outer periphery of the surface side of the bonded substrate.

2. The method for manufacturing a substrate according to claim 1, wherein in the step of grinding the outer periphery, the bonded substrate stack and the grindstone are tilted in a direction that moves them apart relatively.

3. The method for manufacturing a substrate according to claim 1, wherein in the step of grinding the surface, the grindstone is fed relative to the bonded substrate to a first position where the bonded substrate is ground by the grindstone to a first thickness, and feeding relative to the bonded substrate is stopped; and in the step of grinding the outer periphery, when feeding of the grindstone is stopped, the bonded substrate and the grindstone are tilted in directions that move them apart relative to each other.

4. The method for manufacturing a substrate according to claim 3, wherein the step of grinding the outer periphery includes a step of feeding the grindstone relative to the bonded substrate to a second position where the bonded substrate is ground by the grindstone to a second thickness, and then stopping the feeding relative to the bonded substrate, thereby grinding the outer periphery of the bonded substrate.

5. A grinding apparatus comprising: a rotatable holding unit that holds a substrate; a grinding unit having a grinding wheel that can rotatably grind the substrate; a feed unit that feeds the grinding unit toward the holding unit; and a control unit that controls the holding unit, the grinding unit, and the feed unit, wherein the control unit grinds the surface of a bonded substrate formed by bonding multiple substrates held by the holding unit with the grinding unit, and tilts at least one of the bonded substrate held by the holding unit and the grinding wheel relatively to grind the outer periphery of the surface side of the bonded substrate with the grinding unit.

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