Bend correction method

Abstract

To provide a correction method for a plate-like material, capable of appropriately correcting the plate-like material that is bent in a chevron shape to a flat.SOLUTION: A correction method for a plate-like material, includes: a resin preparation step of preparing a first resin G1 that is hardened by being contracted by radiation of an ultraviolet ray UV, and comparatively easily peels from the plate-like material, and a second resin G2 that is hardened by being contracted by radiation of the ultraviolet ray UV, and is comparatively strongly adhered to the plate-like material; a first coating step of forming an uncoating region where the first resin G1 is coated to the center region 16a of the surface of the plate-like material that is bent and becomes a chevron shape, and is not coated to the outer periphery of the surface, or forming an uncoating region where the second resin G2 is coated to the outer peripheral region 16b of the surface the plate-like material that is bent and becomes the chevron shape, and is not coated to the center of the surface; a second coating step of coating the other resin so as to coat one resin coated by the first coating step from the first resin G1 and second resin G2 and the uncoating region after the first coating step; and an ultraviolet ray radiation step of radiating the ultraviolet ray and contracting and hardening the first and second resins.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for straightening a curved plate-like object by flattening the curved plate-like object. [Background technology]

[0002] A wafer has a number of devices such as ICs and LSIs formed on its front surface, separated by planned dividing lines. The back surface is ground by a grinding machine to form the wafer into the desired thickness. The wafer is then divided into individual device chips by a dicing machine and laser processing machine. These chips are then used in electrical devices such as mobile phones and personal computers.

[0003] In addition, a technology has been put into practical use in which the front surfaces of individual device chips are arranged facing each other on a wiring board having multiple areas corresponding to the device chips, and then a resin is molded over the entire back surface of the device chip to create a package substrate (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-032471 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a package substrate is produced by molding resin on the back surface side, a tensile force acts on the back surface side as the resin shrinks, causing the front surface side to curve in a mountain shape. When the front surface side of such a package substrate is placed on a chuck table and the entire substrate is suction-held in order to grind the back surface of the substrate, if the curvature is large, the front surface side of the package substrate does not come into close contact with the chuck table, and the substrate cannot be properly suction-held.

[0006] The present invention has been made in consideration of the above-mentioned facts, and its main technical object is to provide a method for straightening a plate-shaped object, which can appropriately straighten a plate-shaped object that is curved in a mountain shape to make it flat. [Means for solving the problem]

[0007] In order to solve the above-mentioned main technical problem, according to the present invention, a method for straightening a curved plate-like object for flattening the plate-like object includes a resin preparation step for preparing a first resin that shrinks and hardens by irradiation with ultraviolet light and peels off relatively easily from the plate-like object, and a second resin that shrinks and hardens by irradiation with ultraviolet light and adheres relatively firmly to the plate-like object; a first application step for applying the first resin to the central region of the surface of the plate-like object that has curved and become mountain-shaped and forming an uncoated region in which the first resin is not applied in the outer peripheral region, or applying the second resin to the outer peripheral region of the surface of the plate-like object that has curved and become mountain-shaped and forming an uncoated region in which the second resin is not applied in the central region; a second application step for applying the other resin of the first and second resins so as to cover one of the resins applied by the first application step and the uncoated region; and an ultraviolet irradiation step for irradiating ultraviolet light to shrink and harden the first and second resins. The method for straightening the curve includes the steps of:

[0008] When a first resin is applied to the central region of the surface of the plate-like object in the first application step, it is preferable to carry out the ultraviolet irradiation step after the first application step to harden the first resin, and then to carry out the second application step in which the second resin is applied to cover the first resin and the uncoated region of the outer circumferential region, and to carry out the ultraviolet irradiation step to shrink and harden the second resin.

[0009] If a second resin is applied to the peripheral region of the surface of the plate-like object in the first application step, it is preferable to carry out the ultraviolet irradiation step after the first application step to harden the second resin, and then to carry out the second application step in which the first resin is applied to cover the second resin and the uncoated region of the central region, and to carry out the ultraviolet irradiation step to shrink and harden the first resin. Effect of the Invention

[0010] The curvature correction method of the present invention includes a resin preparation step of preparing a first resin that shrinks and hardens when irradiated with ultraviolet light and peels off relatively easily from a plate-like object, and a second resin that shrinks and hardens when irradiated with ultraviolet light and adheres relatively firmly to the plate-like object; a first application step of applying the first resin to a central region of the surface of the plate-like object that has curved into a mountain shape and forming an unapplied region in the outer periphery where the first resin is not applied, or applying the second resin to the peripheral region of the surface of the plate-like object that has curved into a mountain shape and forming an unapplied region in the central region where the second resin is not applied; After the first coating step, the method includes a second coating step in which the other of the first and second resins is coated so as to cover one of the resins coated in the first coating step and the uncoated area, and an ultraviolet irradiation step in which ultraviolet light is applied to cause the first and second resins to shrink and harden.This makes it possible to straighten out the plate-shaped object even if its front surface is curved in a mountain shape, thereby eliminating the problem that, for example, when grinding the back surface, the plate-shaped object is curved and cannot be properly held by suction even if the front surface is sucked onto the chuck table. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is an overall perspective view of the curvature correction device. [Diagram 2] FIG. 2A is a perspective view of a wafer whose curvature is corrected by the curvature correction device shown in FIG. 1, and FIG. 2B is a schematic cross-sectional view showing the curvature of the wafer shown in FIG. [Diagram 3] (a) An oblique view showing an embodiment of the first coating step of Example 1, (b) an oblique view of a wafer on which a first resin has been coated by the first coating step shown in (a), (c) an oblique view showing an embodiment of an ultraviolet irradiation step, and (d) a cross-sectional view of the wafer on which the first resin has been hardened by the ultraviolet irradiation step (c). [Figure 4]FIG. 1A is an oblique view showing an embodiment of the second coating step of Example 1; FIG. 1B is an oblique view of a wafer to which a second resin has been applied by the second coating step shown in FIG. 1A; and FIG. 1C is a cross-sectional view of the wafer shown in FIG. 1B, in which ultraviolet rays have been irradiated to correct the curvature of the wafer. [Diagram 5] (a) An oblique view showing an embodiment of the first coating step of Example 2; (b) An oblique view of a wafer on which a second resin has been coated by the first coating step shown in (a); (c) An oblique view showing an embodiment of an ultraviolet irradiation step; (d) A cross-sectional view of the wafer on which the second resin has been hardened by the ultraviolet irradiation step (c). [Figure 6] FIG. 1(a) is an oblique view showing an embodiment of the second coating step of Example 2; FIG. 1(b) is an oblique view of a wafer to which a first resin has been applied by the second coating step shown in FIG. 1(a); and FIG. 1(c) is a cross-sectional view of the wafer shown in FIG. 1(b) in which ultraviolet rays have been irradiated to correct the curvature. [Figure 7] FIG. 1 is a perspective view showing an embodiment of a grinding process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a curvature correction method configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0013] FIG. 1 shows an overall perspective view of a curvature correction device 1 suitable for carrying out the curvature correction method of the present embodiment. The curvature correction device 1 includes a housing 2, a holding means 20 arranged in the housing 2 and holding a plate-like object, an ultraviolet curing resin application means 30 that applies an ultraviolet curing resin to the plate-like object held by the holding means 20, a conveying means 40 that moves the ultraviolet curing resin application means 30 in the Y-axis direction indicated by the arrow Y, a high-pressure air supplying means 50 that supplies high-pressure air W to the ultraviolet curing resin application means 30, an ultraviolet irradiation means 60 that irradiates ultraviolet rays to the plate-like object, an ultraviolet curing resin supplying means 70 that supplies ultraviolet curing resin to the ultraviolet curing resin application means 30, and a control means (not shown). Each of the means constituting the illustrated curvature correction device 1 is supported by an appropriate support stand, but is omitted in FIG. 1 for convenience of explanation.

[0014] The housing 2 is formed in a box shape with an open top. The bottom 2a of the housing 2 is inclined, and a drain 2b is provided at the end (deepest part) in the inclined direction to discharge excess ultraviolet curing resin and cleaning water generated when cleaning the inside of the housing 2. Furthermore, an opening 2d is formed in a side wall 2c of the housing 2 to which a suction duct 2e is connected, in which a suction means (not shown) is provided.

[0015] The holding means 20 includes a chuck table 21 formed on a rotating shaft 22 and a drive motor 23 for rotating the rotating shaft 22 in the direction indicated by the arrow R1, and is disposed in the center of the bottom 2a of the housing 2. The holding surface of the chuck table 21 is formed of a porous material having air permeability, and is connected to a suction source (not shown). By operating the suction source to generate negative pressure on the holding surface of the chuck table 21, a plate-like object can be sucked and held. The diameter of the chuck table 21 is set to be smaller than the plate-like part to be held.

[0016] The ultraviolet curing resin application means 30 includes a transport arm 31 and an ultraviolet curing resin injection nozzle 32 supported by the transport arm 31. The transport arm 31 includes a sliding portion 31a that slides in the Y-axis direction on a guide rail 45 of the transport means 40 described later, a horizontal portion 31b that supports a tip portion 32a of the ultraviolet curing resin injection nozzle 32, and a vertical portion 31c that supports a main body portion 32b of the ultraviolet curing resin injection nozzle 32. An ultraviolet curing resin introduction portion 32c into which the ultraviolet curing resin described later is introduced is formed at the upper end of the ultraviolet curing resin injection nozzle 32. The ultraviolet curing resin used in the curvature correction device 1 of this embodiment includes a first resin G1 that shrinks and hardens when irradiated with ultraviolet rays, has a weak adhesive force to a plate-like object that is the object of the curvature correction method of this embodiment, and can be relatively easily peeled off from the plate-like object, and a second resin G2 that shrinks and hardens when irradiated with ultraviolet rays and adheres more firmly to the plate-like object that is the object of the curvature correction method of this embodiment than the first resin G1. 1 shows only one ultraviolet curing resin supply means 70 for convenience of explanation, but it is also possible to provide an ultraviolet curing resin supply means 70 that supplies a first resin G1 and another ultraviolet curing resin supply means having the same configuration as the ultraviolet curing resin supply means 70 and supplying a second resin G2, or to supply the resin stored in the storage tank 71 of the ultraviolet curing resin supply means 70 by switching between supplying the first resin G1 and supplying the second resin G2. In the embodiment described below, it is described as providing an ultraviolet curing resin supply means 70 that supplies the first resin G1 and another ultraviolet curing resin supply means (not shown) that has the same configuration as the ultraviolet curing resin supply means 70 and supplies the second resin G2.

[0017] As shown in the figure, the transport means 40 is formed along the opening along the Y-axis direction of the housing 2, and includes a drive roller 41, a driven roller 42, a pulse motor 43 that rotates and drives the drive roller 41, a transport belt 44 (shown by a dashed line) that is wound around the drive roller 41 and the driven roller 42, and a guide rail 45 that supports the sliding part 31a of the transport arm 31 described above and is disposed adjacent to the transport belt 44 in the Y-axis direction. Since the transport belt 44 and the sliding part 31a of the transport arm 31 described above are connected, the pulse motor 43 is operated by the control means described above to rotate the drive roller 41, thereby moving the transport arm 31 to a desired position in the Y-axis direction. The ultraviolet curing resin spray nozzle 32 is disposed in the center of the housing 2 in the X-axis direction, and by operating the above-mentioned conveying means 40, it is possible to position the ultraviolet curing resin spray nozzle 32 on the ultraviolet curing resin supply means 70 side, and also to position the tip 32a of the ultraviolet curing resin spray nozzle 32 on the chuck table 21 side.

[0018] In the curvature correction device 1 of this embodiment, a high-pressure air supply means 50 is provided to supply high-pressure air W to the ultraviolet curing resin injection nozzle 32. The high-pressure air supply means 50 includes a high-pressure air source 51, an air supply path 52 connected to the high-pressure air source 51, and an opening / closing valve 53 provided in the air supply path 52. The pressure of the high-pressure air W supplied by the high-pressure air supply source 51 is, for example, 0.5 MPa. The high-pressure air W is supplied to the horizontal portion 31b of the transport arm 31, and is introduced into the tip portion 32a of the ultraviolet curing resin injection nozzle 32 within the horizontal portion 31b. By introducing the high-pressure air W into the ultraviolet curing resin injection nozzle 32, ultraviolet curing resins G1 and G2 can be injected from the ultraviolet curing resin injection nozzle 32.

[0019] In this embodiment, an ultraviolet irradiator 60 is disposed on the horizontal portion 31b of the transport arm 31. The ultraviolet irradiator 60 has ultraviolet lamps arranged in the X-axis direction on the underside, and can irradiate ultraviolet rays toward the underside over a wide range in the X-axis direction. Since the ultraviolet irradiator 60 is disposed on the horizontal portion 31b of the transport arm 31, it can be moved in the Y-axis direction by operating the transport means 40 described above, and can pass above the plate-like object held on the chuck table 21, irradiating the entire upper surface of the plate-like object with ultraviolet rays.

[0020] The ultraviolet curing resin supplying means 70 includes a storage tank 71 for storing ultraviolet curing resins G1 and G2, a supply pipe 72 disposed at the bottom of the storage tank 71, and an opening / closing valve 73 disposed at the supply pipe 72. The ultraviolet curing resin supplying means 70 is installed on one side (the back side in the figure) of the housing 2, and by operating the above-mentioned conveying means 40 to move the ultraviolet curing resin jet nozzle 32 in the Y-axis direction, the ultraviolet curing resin introduction part 32c of the ultraviolet curing resin jet nozzle 32 can be positioned directly below the tip part 72a of the supply pipe 72. This allows the ultraviolet curing resins G1 and G2 to be supplied to the ultraviolet curing resin jet nozzle 32 through the supply pipe 72. For convenience of explanation, the upper part of the illustrated storage tank 71 is shown in an open state, but the upper part of the storage tank 71 is closed by an appropriate lid member to prevent ultraviolet rays from entering the inside of the storage tank 71. Although not shown in the drawings, in the curvature correction device 1 of this embodiment, since the first resin G1 and the second resin G2 are used, two ultraviolet curing resin supplying means 70 are also prepared.

[0021] The first resin G1 and the second resin G2 of this embodiment are ultraviolet curing resins that shrink and harden when irradiated with ultraviolet light, and are mainly composed of a main material that determines adhesion, shrinkage, and hardening properties, a secondary material for controlling hardening properties and properties, and a photopolymerization initiator. The main material constituting the first resin G1 and the second resin G2 used in this embodiment is selected from urethane acrylate, epoxy acrylate, acrylic acrylate, polyester acrylate, alicyclic epoxy, oxetane compound, etc., the secondary material is selected from multifunctional acrylate monomer, monofunctional acrylate monomer, vinyl ether monomer, etc., and the photopolymerization initiator is appropriately selected and mixed from benzophenone, acetophenone, sulfonium salt, etc.

[0022] The curvature correction device 1 of this embodiment has a configuration generally as described above, and an embodiment of a curvature correction method carried out using this curvature correction device 1 will be described below.

[0023] Example 1 A first embodiment of the method for straightening a curvature of a plate-like object according to the present invention will be described below.

[0024] (Resin preparation process) In carrying out the curvature correction method of the present invention, a first resin G1 is prepared, which shrinks and solidifies when irradiated with ultraviolet light, and is relatively easily peeled off from a plate-like object, and a second resin G2 is prepared, which shrinks and solidifies when irradiated with ultraviolet light, and is relatively firmly attached to the plate-like object. The plate-like object in this Example 1 is a wafer 10, which will be described later.

[0025] In this resin preparation process, when preparing the first resin G1 and the second resin G2 having the desired characteristics, the adhesiveness to the workpiece and the volumetric shrinkage rate when irradiated with ultraviolet light and cured are adjusted by appropriately selecting the materials to be the materials from the main materials and secondary materials and adjusting the amount of the materials to be mixed. The ultraviolet curable resins G1 and G2 in this embodiment 1 are prepared by appropriately selecting an acrylic resin and an epoxy resin from the main materials and secondary materials and changing the mixing ratio to adjust the physical properties.

[0026] In preparing the ultraviolet curing resin in this embodiment 1, by increasing the mixing ratio of the acrylic resin to the epoxy resin, the resin tends to adhere relatively strongly to the plate-shaped object when it shrinks and hardens due to irradiation with ultraviolet light, and by decreasing the mixing ratio of the acrylic resin, the resin tends to be relatively easily peeled off from the plate-shaped object when it shrinks and hardens due to irradiation with ultraviolet light. Therefore, in order to prepare a first resin G1 that shrinks and hardens due to irradiation with ultraviolet light and can be relatively easily peeled off from the plate-shaped object, for example, a liquid ultraviolet curing resin is formed by mixing an acrylic resin and an epoxy resin selected from the above-mentioned main material and sub-material in a ratio of approximately equal amounts (49.5% each mixed) in addition to a photopolymerization initiator (1%). Also, in order to prepare a second resin G2 that shrinks and hardens due to irradiation with ultraviolet light and adheres relatively strongly to the plate-shaped object compared to the first resin G1, the ratio of the acrylic resin is increased (for example, to 69.5%) and the ratio of the epoxy resin is decreased (29.5%) compared to the first resin G1, and these are mixed to form a liquid ultraviolet curing resin. In this embodiment 1, the first resin G1 and the second resin G2 are set so that their volumetric shrinkage rates when irradiated with ultraviolet light are approximately the same.

[0027] In this embodiment 1, since the first resin G1 is used first, the conveying means 40 is operated to position the ultraviolet curing resin introduction portion 32c of the ultraviolet curing resin spray nozzle 32 at the tip 72a of the supply pipe 72 of the ultraviolet curing resin supplying means 70 that stores the first resin G1 in the storage tank 71. Next, the opening and closing valve 73 of the ultraviolet curing resin supplying means 70 is opened to fill the ultraviolet curing resin spraying nozzle 32 with a predetermined amount of the first resin G1. This completes the resin preparation process.

[0028] In addition, the present invention is not limited to the above-mentioned mixture ratio of acrylic resin and epoxy resin, and the mixture ratio of the main material and the sub-material may be appropriately adjusted according to the physical properties of the object. In this case, it is important to set the first resin G1 to have a property of shrinking and hardening by irradiation with ultraviolet light and peeling relatively easily from the plate-like object, whereas the second resin G2 has a property of shrinking and hardening by irradiation with ultraviolet light and attaching relatively firmly to the plate-like object, compared to the first resin G1.

[0029] (First Coating Step) The plate-like object to be corrected based on the curvature correction method of the present embodiment 1 is, for example, a wafer 10 shown in FIG. 2(a). The illustrated wafer 10 is a silicon wafer in which a plurality of devices 12 are formed on the front surface 10a, partitioned by the division lines 14, and a package wafer in which a resin is molded on the back surface 10b. The wafer 10 is a wafer with a thickness of 700 μm and a diameter of 200 mm. As shown in FIG. 2(b), the front surface 10a of the wafer 10 is curved in a mountain shape that is convex upward, and the central region is higher by A mm (for example, 1 mm) than the peripheral region. Note that in FIG. 2(b), the degree of curvature is exaggerated for the convenience of explanation, and does not match the actual degree of curvature.

[0030] When carrying out the first coating step, first, the wafer 10 is placed with the front surface 10a facing upward on the chuck table 21 of the holding means 20 arranged in the curvature correction device 1 described based on Fig. 1, and the wafer 10 is held by suction by operating a suction source (not shown). As described above, the wafer 10 is curved so that the front surface 10a side is convex, forming a mountain shape, but since the diameter of the chuck table 21 of the holding means 20 is set to a diameter sufficiently small compared to the wafer 10, there is no problem in suction-holding the wafer 10 by the chuck table 21.

[0031] After the wafer 10 is held by suction with the holding means 20, the conveying means 40 described based on Fig. 1 is operated to move the conveying arm 31 in the Y-axis direction, and the ultraviolet curing resin spray nozzle 32 filled with the first resin G1 is positioned above the center of the wafer 10 as shown in Fig. 3(a). Next, the rotating shaft 22 of the holding means 20 is rotated in the direction indicated by the arrow R1 to rotate the wafer 10 in the direction indicated by the arrow R2, and the high-pressure air supplying means 50 described above is operated for a predetermined time to introduce high-pressure air W into the horizontal part 31b of the conveying arm 31. The high-pressure air W introduced into the horizontal part 31b is introduced into the spraying passage (not shown) of the tip part 32a through a communication passage (not shown) in the horizontal part 31b and a ring-shaped introduction passage formed so as to surround the outer periphery of the tip part 32a of the ultraviolet curing resin spray nozzle 32, and the first resin G1 is sprayed from the tip part 32a. At this time, a suction means (not shown) is operated to discharge droplets of the first resin G1 scattered within the housing 2 to the outside via the suction duct 2e of the curvature correction device 1.

[0032] Here, in the first coating step, as shown in FIG. 3(b), the first resin G1 is applied only to the central region 16a of the surface of the wafer 10, which is curved and shaped like a mountain, and a non-coated region where the first resin G1 is not applied is formed in the outer peripheral region 16b surrounding the central region 16a. The central region 16a includes a circular region on the central side where the devices 12 are formed, and the outer peripheral region 16b is a small surplus region on the outside where the devices 12 are not formed, separated from the central region 16a by the dashed line L in the figure. When forming the non-coated region, for example, a ring-shaped mask sheet (not shown) may be laid on the outer peripheral region 16b, and the ring-shaped mask sheet may be peeled off after the first resin G1 is applied to the surface 10a of the wafer 10, or after performing an ultraviolet irradiation step before applying the second resin G2 described later. The thickness of the first resin G1 applied to the central region 16a may be a thickness that has little effect on the elimination of the curvature of the wafer 10 when it shrinks and hardens in the ultraviolet irradiation process described later, and it is sufficient that the thickness covers the entire central region 16a (e.g., 50 μm). With the above, the first application process in this embodiment 1 is completed.

[0033] (Ultraviolet irradiation process) After the first coating step is performed, the ultraviolet irradiation step is performed to shrink and harden the first resin G1. More specifically, the ultraviolet lamp of the ultraviolet irradiator 60 is turned on and the transport means 40 is operated, and the ultraviolet irradiator 60 is moved in the direction indicated by the arrow R3 as shown in FIG. 3(c) to irradiate the front surface 10a of the wafer 10 with ultraviolet rays UV. In this embodiment 1, the ultraviolet irradiator 60 is moved in the direction indicated by the arrow R3 to pass over the wafer 10, and then the ultraviolet irradiator 60 is moved in the opposite direction to perform reciprocating motion. As a result, the first resin G1 applied to the central region 16a of the front surface 10a of the wafer 10 is sufficiently irradiated with ultraviolet rays UV, and the first resin G1 is shrunk and hardened. At this time, the wafer 10 may be rotated at a low speed in the direction indicated by the R2 so as to prevent uneven hardening. In FIG. 3(c), the transport arm 31 supporting the ultraviolet irradiator 60 and the like are omitted for convenience of explanation. By irradiating the first resin G1 with ultraviolet rays UV in this manner, the first resin G1 applied to the central region 16a of the wafer 10 is cured, and the first resin G1 is not applied to the peripheral region 16b, as shown in Fig. 3(d). By carrying out the above-mentioned first application step and ultraviolet irradiation step, the curvature of the wafer 10 is slightly corrected.

[0034] (Second Coating Step) After the above-mentioned first coating process and ultraviolet irradiation process have been performed, a second coating process is performed in which the other resin not applied in the first coating process, i.e., the second resin G2, is applied to the entire surface 10a of the wafer 10 so as to cover the first resin G1 applied in the first coating process and the uncoated area of ​​the outer circumferential region 16b.

[0035] When carrying out the second application step, another ultraviolet curing resin supplying means (not shown) that has the same configuration as the ultraviolet curing resin supplying means 70 that supplies the first resin G1 and supplies the second resin G2 is positioned relative to the ultraviolet curing resin application means 30 of the curvature correction device 1, and the second resin G2 is filled into the ultraviolet curing resin spray nozzle 32. At this time, the first resin G1 has been removed in advance from the ultraviolet curing resin spraying nozzle 32 of the ultraviolet curing resin application means 30.

[0036] 4(a), the ultraviolet curing resin spray nozzle 32 is positioned above the central region 16a of the wafer 10, and the rotating shaft 22 of the holding means 20 is rotated in the direction indicated by the arrow R1 to rotate the wafer 10 in the direction indicated by the arrow R2, while the high-pressure air supply means 50 is operated for a predetermined time to introduce compressed air W into the horizontal part 31b of the transfer arm 31. As a result, the second resin G2 is sprayed from the tip 32a of the ultraviolet curing resin spray nozzle 32, and the suction means (not shown) is operated to discharge the droplets of the second resin G2 scattered inside the housing 2 to the outside via the suction duct 2e of the curvature correction device 1.

[0037] Here, in this second coating step, as can be seen from Fig. 4(b) in addition to Fig. 4(a), the second resin G2 is applied so as to cover the curved, mountain-shaped central region 16a of the wafer 10 and the non-coated peripheral region 16b, i.e., the entire front surface 10a of the wafer 10. The thickness of the second resin G2 applied in this second coating step is set as follows.

[0038] A correlation between the amount of warpage of the wafer 10 to be corrected in this embodiment 1 (A mm shown in FIG. 2(b)) and the thickness of the second resin G2 that corrects the warpage when the wafer 10 is applied to the entire surface 10a of the wafer 10 and cured by irradiating ultraviolet rays is obtained in advance by an experiment. When obtaining the correlation, for example, a wafer having the same material and dimensions as the wafer 10 to be corrected in this embodiment 1 and having a warpage of 1.5 mm with a mountain-shaped surface is selected, and the second resin G2 is applied little by little to the surface side of the wafer and cured while irradiating ultraviolet rays UV, gradually increasing the thickness of the second resin G2 to obtain a change in the amount of warpage of the wafer (degree of correction). As a result, the correlation between the degree of curvature of the wafer (A mm) and the thickness of the second resin G2 that corrects the curvature (X μm) can be obtained and stored in the control means 9.

[0039] In the second coating step of this embodiment 1, the degree of curvature of the wafer 10 is 1 mm, and the thickness of the second resin G2 capable of correcting the curvature of 1 mm is specified based on the correlation obtained in advance by the above-mentioned experiment, and is set to, for example, 1000 μm. Once the thickness of the second resin G2 is obtained in this way, the second resin G2 is applied to the front surface 10a of the wafer 10 so that the thickness of the second resin G2 applied by the completion of the second coating step is 1000 μm. Since the thickness applied by one coating step is, for example, about 400 μm, when the target thickness of the second resin G2 is 1000 μm, the second resin G2 is applied in three steps. At this time, the amount of curvature corrected by the first resin G1 described above may be taken into consideration.

[0040] (Ultraviolet irradiation process) After the second coating step is performed, an ultraviolet irradiation step is performed to shrink and harden the second resin G2 (not shown). This ultraviolet irradiation step is the same as the step described based on FIG. 3(c), and the ultraviolet lamp of the ultraviolet irradiator 60 is turned on and the conveying means 40 is operated to irradiate the entire surface 10a of the wafer 10 with ultraviolet rays UV. The second resin G2 applied to the wafer 10 is sufficiently irradiated with ultraviolet rays UV to shrink and harden the second resin G2. At this time, the wafer 10 may be rotated at a low speed. By irradiating the second resin G2 with ultraviolet rays UV in this way, as shown in FIG. 4(c), the second resin G2 applied to the central region 16a and the outer peripheral region 16b of the wafer 10 shrinks in the direction indicated by the arrow R4 when hardened, so that the outer peripheral side of the wafer 10 is lifted in the direction indicated by the arrow R5, and the curvature of the wafer 10 is corrected to a flat state, completing the curvature correction method in this embodiment 1.

[0041] The second coating step of coating the second resin G2 and the ultraviolet irradiation step of curing the second resin G2 can be performed in multiple steps. For example, the first second coating step is performed to spray the second resin G2 onto the surface 10a of the wafer 10 to a thickness of 400 μm, and then the ultraviolet irradiation step is performed to cure the second resin G2. The second coating step is then performed to spray the second resin G2 onto the surface 10a of the wafer 10 to a thickness of 400 μm, and then the ultraviolet irradiation step is performed to cure the second resin G2. The third second coating step is then performed to spray the second resin G2 onto the surface 10a of the wafer 10 to a thickness of 200 μm, and then the ultraviolet irradiation step is performed to cure the second resin G2.

[0042] Example 2 The present invention is not limited to the above-described first embodiment, but may be, for example, a second embodiment described below with reference to FIGS.

[0043] (Resin preparation process) When carrying out the curvature correction method of the present invention in this embodiment 2, a first resin G1 that shrinks and solidifies when irradiated with ultraviolet light and peels off relatively easily from a plate-like object, and a second resin G2 that shrinks and solidifies when irradiated with ultraviolet light and adheres relatively firmly to the plate-like object are prepared. Note that the specific procedure in the resin preparation step in this embodiment 2 can be carried out in the same manner as in the above-mentioned embodiment 1, so a detailed description will be omitted.

[0044] (First Coating Step) The plate-like object to be corrected based on the curvature correction method of the present embodiment 2 is the wafer 10 shown in Fig. 2(a) described above. The illustrated wafer 10 is a packaged wafer in which a plurality of devices 12 are formed on the front surface 10a and partitioned by the division lines 14, and a resin is molded on the back surface 10b. The wafer 10 is 700 µm thick and 200 mm in diameter. As shown in Fig. 2(b), the front surface 10a of the wafer 10 is curved in a mountain shape that is convex upward, and the center is higher by A mm (for example, 1 mm).

[0045] In the first coating step in this embodiment 2, the second resin G2 is applied to the outer periphery (outer periphery region 16b in FIG. 5(a)) of the front surface 10a of the curved and mountain-shaped wafer 10, and a non-coated region where the second resin G2 is not applied is formed in the center (center region 16a in FIG. 5(a)). In the first coating step, the front surface 10a of the wafer 10 is placed facing upward on the chuck table 21 of the holding means 20 arranged in the curve correction device 1 described based on FIG. 1, and the wafer 10 is held by suction by operating a suction source (not shown). In the first coating step in this embodiment 2, the second resin G2 is applied to the wafer 10 first, so that the ultraviolet curing resin supplying means 70 in which the second resin G2 is stored in the storage tank 71 is positioned in the curve correction device 1, and the ultraviolet curing resin spray nozzle 32 is filled with the second resin G2.

[0046] After the wafer 10 is held by suction with the holding means 20, the conveying means 40 described based on Fig. 1 is operated to move the conveying arm 31 in the Y-axis direction, and the ultraviolet curing resin spray nozzle 32 filled with the second resin G2 is positioned above the outer peripheral region 16b of the wafer 10 as shown in Fig. 5(a). Next, the rotating shaft 22 of the holding means 20 is rotated in the direction indicated by the arrow R1 to rotate the wafer 10 in the direction indicated by the arrow R2, and the high-pressure air supplying means 50 is operated for a predetermined time to introduce high-pressure air W into the horizontal part 31b of the conveying arm 31. The high-pressure air W introduced into the horizontal part 31b is introduced into the spraying passage (not shown) of the tip part 32a through a communication passage (not shown) in the horizontal part 31b and a ring-shaped introduction passage formed so as to surround the outer periphery of the tip part 32a of the ultraviolet curing resin spray nozzle 32, and the second resin G2 is sprayed from the tip part 32a. At this time, a suction means (not shown) is operated to discharge droplets of the second resin G2 scattered within the housing 2 to the outside via the suction duct 2e of the curvature correction device 1.

[0047] Here, in the first coating step of this embodiment 2, as shown in Fig. 5(b), the second resin G2 is coated only on the outer peripheral region 16b of the surface 10a of the curved, mountain-shaped wafer 10, and a non-coated region where the second resin G2 is not coated is formed in the central region 16a. The central region 16a includes a circular region near the center where the devices 12 are formed, and the outer peripheral region 16b is a small surplus region where the devices 12 are not formed, located on the outer periphery side separated from the central region 16a by the dashed line L shown in Fig. 5(a). When forming the non-coated region, for example, a circular mask sheet (not shown) may be laid in the central region 16a, and the above-mentioned second resin G2 may be coated on the surface 10a of the wafer 10, and then the circular mask sheet may be peeled off. In addition, the second resin G2 applied to the outer peripheral region 16b has almost no effect on the correction of the curvature of the wafer 10 when it shrinks and hardens by the ultraviolet irradiation process described later, so it is sufficient to apply the second resin G2 thinly to the outer peripheral region 16b (for example, a thickness of 50 μm). With the above, the first application process in this embodiment 2 is completed.

[0048] (Ultraviolet irradiation process) After the first coating step is performed, the ultraviolet irradiation step is performed to shrink and harden the second resin G2. More specifically, the ultraviolet lamp of the ultraviolet irradiator 60 is turned on and the transport means 40 is operated, and the ultraviolet irradiator 60 is moved in the direction indicated by the arrow R3 as shown in FIG. 5(c) to irradiate the front surface 10a of the wafer 10 with ultraviolet rays UV. In this embodiment 2, it is also preferable to move the ultraviolet irradiator 60 in the direction indicated by the arrow R3 to pass over the wafer 10, and then move the ultraviolet irradiator 60 in the opposite direction to perform reciprocating motion. This allows the second resin G2 applied to the outer peripheral region 16b of the front surface 10a of the wafer 10 to be sufficiently irradiated with ultraviolet rays UV, causing the second resin G2 to shrink and harden. At this time, the wafer 10 may be rotated at a low speed in the direction indicated by the R2 to prevent uneven hardening. Note that in FIG. 5(c), the transport arm 31 supporting the ultraviolet irradiator 60 and the like are omitted for convenience of explanation. By irradiating the second resin G2 with ultraviolet rays UV in this manner, the second resin G2 applied to the outer peripheral region 16b of the wafer 10 is cured, and the central region 16a is left uncoated with the second resin G2, as shown in Fig. 5(d). Even if the above-mentioned first coating step and ultraviolet ray irradiation step are performed, the curvature of the wafer 10 is hardly corrected.

[0049] (Second coating step) After the first coating step and ultraviolet irradiation step of the present embodiment 2 described above have been performed, a second coating step is performed in which the other resin not coated in the first coating step, i.e., the first resin G1, is coated over the entire surface 10a of the wafer 10 so as to cover the second resin G2 coated in the first coating step and the uncoated area of ​​the central region 16a.

[0050] When carrying out the second application step, another ultraviolet curing resin supplying means (not shown) that has the same configuration as the ultraviolet curing resin supplying means 70 that supplies the second resin G2 and supplies the first resin G1 is positioned relative to the ultraviolet curing resin application means 30 of the curvature correction device 1, and the first resin G1 is filled into the ultraviolet curing resin spray nozzle 32. At this time, the second resin G2 has been removed in advance from the ultraviolet curing resin spraying nozzle 32 of the ultraviolet curing resin application means 30.

[0051] 6(a), the ultraviolet curing resin spray nozzle 32 is positioned above the central region 16a of the wafer 10, and while the rotating shaft 22 of the holding means 20 is rotated in the direction indicated by the arrow R1 to rotate the wafer 10 in the direction indicated by the arrow R2, the high-pressure air supply means 50 is operated for a predetermined time to introduce compressed air W into the horizontal part 31b of the transfer arm 31. As a result, the first resin G1 is sprayed from the tip 32a of the ultraviolet curing resin spray nozzle 32, and the suction means (not shown) is operated to discharge the droplets of the first resin G1 scattered inside the housing 2 to the outside via the suction duct 2e of the curvature correction device 1 described above.

[0052] 6(b) in addition to Fig. 6(a), the second coating step coats the first resin G1 so as to cover the central region 16a, which is left uncoated in the curved, mountain-shaped wafer 10, and the outer peripheral region 16b, to which the second resin G2 has been previously coated, that is, the entire front surface 10a of the wafer 10. The thickness of the first resin G1 applied in the second coating step is set as follows.

[0053] In this embodiment, the correlation between the amount of warpage of the wafer 10 to be corrected in this embodiment (A mm shown in FIG. 2(b)) and the thickness of the first resin G1 that corrects the warpage when the wafer 10 is applied to the entire surface 10a of the wafer 10 and cured by irradiating ultraviolet rays is previously obtained by experiment. When obtaining the correlation, for example, a wafer having the same material and dimensions as the wafer 10 to be corrected in this embodiment, and having a warpage amount of, for example, 1.5 mm that makes the surface shaped like a mountain is selected, and the first resin G1 is applied little by little to the surface side of the wafer and cured while irradiating ultraviolet rays UV, gradually increasing the thickness of the first resin G1 to obtain a change in the amount of warpage of the wafer (degree of correction). As a result, the correlation between the degree of curvature of the wafer (A mm) and the thickness of the first resin G1 that corrects the curvature (X μm) is obtained, and the result can be stored in the control means 9.

[0054] The degree of curvature of the wafer 10 in this embodiment 2 is 1 mm, and the thickness of the first resin G1 capable of correcting the curvature of 1 mm is set to, for example, 1000 μm based on the correlation obtained in advance by the above-mentioned experiment. If the thickness of the first resin G1 is obtained in this way, the first resin G1 is applied to the front surface 10a of the wafer 10 so that the thickness of the first resin G1 applied in this second application step is 1000 μm. Since the thickness applied in one application step is, for example, about 400 μm, when the target thickness of the first resin G1 is 1000 μm, the first resin G1 is applied in three steps. Since the second resin G2 applied in the first application step hardly corrects the curvature of the wafer 10, it is not necessary to take this into account when setting the thickness of the first resin G1.

[0055] (Ultraviolet irradiation process) After the second coating step is performed, an ultraviolet irradiation step is performed to shrink and harden the first resin G1 (not shown). This ultraviolet irradiation step is the same as the step described based on FIG. 5(c), and the ultraviolet lamp of the ultraviolet irradiator 60 is turned on and the conveying means 40 is operated to irradiate the entire surface 10a of the wafer 10 with ultraviolet rays UV (not shown). The first resin G1 applied to the wafer 10 is sufficiently irradiated with ultraviolet rays UV to shrink and harden the first resin G1. At this time, the wafer 10 may be rotated at a low speed. By irradiating the first resin G1 with ultraviolet rays UV in this way, as shown in FIG. 6(c), the first resin G1 applied to the central region 16a and the outer peripheral region 16b of the wafer 10 shrinks in the direction indicated by the arrow R4 when hardened, so that the outer peripheral side of the wafer 10 is lifted in the direction indicated by the arrow R5, and the curvature of the wafer 10 is completely corrected to a flat state, completing the curvature correction method in this embodiment 2.

[0056] As in the above-described Example 1, the second application process of applying the first resin G1 and the ultraviolet irradiation process of curing the first resin G1 can be carried out multiple times (detailed explanation is omitted).

[0057] Once the curvature of the wafer 10 has been corrected and flattened by the above-mentioned Examples 1 and 2, the wafer 10 can be transported to the grinding device 80 shown in FIG. 7, placed on the chuck table 81, and held by suction, so that the grinding process of grinding the back surface 10b of the wafer 10 can be properly performed.

[0058] 7, the grinding device 80 includes a grinding means 82 for grinding and thinning the back surface 10b of the wafer 10 held by suction on a chuck table 81. The grinding means 82 includes a rotating shaft 83 rotated by a rotary drive mechanism (not shown), a wheel mount 84 attached to the lower end of the rotating shaft 83, and a grinding wheel 85 attached to the lower surface of the wheel mount 84 and having a plurality of grinding stones 86 arranged in an annular shape on the lower surface side. The holding surface of the chuck table 81 is formed with approximately the same diameter as the wafer 10, is formed of a porous member having air permeability, and is connected to a suction means (not shown).

[0059] When performing the grinding process, the wafer 10 is placed on the holding surface of the chuck table 81 with the back surface 10b side facing upward and the front surface 10a side on which the first resin G1 or second resin G2 layer is formed facing downward, and a suction means (not shown) is operated to generate a negative pressure on the chuck table 81. At this time, the wafer 10 has been subjected to the curvature correction method based on the above-mentioned embodiment, and the initial curvature is corrected and flattened. As a result, the wafer 10 is appropriately sucked and held on the chuck table 81, and the problem of being unable to suck and hold the wafer 10 does not occur. Then, the chuck table 81 is rotated in the direction indicated by the arrow R6 in the figure at, for example, 300 rpm, while the rotating spindle 82 is rotated in the direction indicated by the arrow R7 in the figure at, for example, 6000 rpm. Next, the grinding wheel 86 is brought into contact with the back surface 10b of the wafer 10, and the grinding wheel 85 is fed downward, indicated by R8 in the figure, at a grinding feed rate of, for example, 1.0 μm / sec. At this time, the grinding can be carried out while measuring the thickness of the wafer 10 with a contact or non-contact measuring gauge (not shown), and the back surface 10b of the wafer 10 is ground by a predetermined amount. Once the wafer 10 has reached the predetermined thickness, the grinding process of grinding the back surface 10b of the wafer 10 is completed through cleaning, drying, and other processes.

[0060] According to Examples 1 and 2 of the above-described embodiment, even if the front side of a plate-shaped object is curved in a mountain shape, it is possible to straighten it flat. For example, when grinding the back side, the problem that the curved plate-shaped object cannot be properly sucked and held even when the front side is sucked onto the chuck table is eliminated.

[0061] In the above-mentioned embodiment 1, the first resin G1, which is easily peeled off from the plate-like object, is applied to the central region 16a, and the outer peripheral region 16b is formed with an uncoated region where the first resin G1 is not applied, and the second resin G2, which adheres relatively firmly to the plate-like object, is applied to the first resin G1 and the uncoated region and hardened by ultraviolet light UV. As a result, when the curvature of the wafer 10 is corrected, the second resin G2 does not peel off from the outer peripheral region 16b, and the curvature is reliably corrected by the second resin G2, and further, after the grinding process is completed after the curvature is corrected, the first resin G1 and the second resin G2 can be easily peeled off from the surface 10a of the wafer 10.

[0062] Furthermore, in the above-mentioned second embodiment, the second resin G2 is applied to the outer peripheral region 16b, an uncoated region where the second resin G2 is not applied is formed in the central region, and the second resin G2 is cured by ultraviolet rays UV, and then the first resin G1, which is relatively easily peeled off from the wafer 10, is applied to the outer peripheral region 16b coated with the second resin G2 and the central region 16a which is the uncoated region, and curvature is cured by ultraviolet rays UV. As a result, the second resin G2 does not peel off from the outer peripheral region 16b when the curvature of the wafer 10 is corrected, and the curvature is reliably corrected by the first resin G1 applied to the entire surface 10a of the wafer 10, and further, after the grinding process after the curvature is corrected is completed, the first resin G1 and the second resin G2 can be easily peeled off from the surface 10a of the wafer 10. Furthermore, since the first resin G1 adheres relatively firmly to the second resin G2 applied to the outer peripheral region 16b, the first resin G1 does not peel off from the second resin G2 in the outer peripheral region 16b when the curvature of the wafer 10 is corrected.

[0063] In the above-mentioned Examples 1 and 2, a wafer identical to the wafer 10 to be corrected was prepared, and a correlation was obtained between the amount of warpage (A mm shown in FIG. 2(b)) of the curvature of the wafer 10 to be corrected and the thickness of the first resin G1 and the second resin G2 that correct the curvature when applied to the entire surface 10a of the wafer 10 and cured by irradiating ultraviolet rays. This is because the effect of correction when a predetermined ultraviolet curing resin (first resin G1, second resin G2) is applied and then irradiated with ultraviolet rays to shrink and harden varies depending on the material, thickness, size (diameter), etc. of the plate-like object to be corrected. Therefore, when there are multiple types of material, thickness, and size of the plate-like object to be corrected, it is preferable to obtain the correlation corresponding to each of them. [Explanation of symbols]

[0064] 1: Curvature correction device 2: Housing 2a: bottom 2b: Drain 2c: side wall 2d: opening 2e: Suction duct 10: Wafer (plate-shaped object) 10a: surface 10b: Back side 12: Device 14: Planned division line 16a: Central area 16b: Outer area 20: Holding means 21: Chuck table 22: Rotation axis 23: Drive motor 30: UV-curable resin application means 31: Transport arm 31a: Sliding part 31b:Horizontal part 31c: Vertical section 32: UV-curable resin spray nozzle 32a:Tip 32b: Main body 32c: Ultraviolet curing resin introduction part 40: Means of transportation 41: Drive roller 42: Driven roller 43: Pulse motor 44: Conveyor belt 45: Guide rail 50: High pressure air supply means 51: High pressure air source 52: Air supply line 53: Opening and closing valve 60: Ultraviolet irradiator 70: Ultraviolet curing resin supply means 71: Storage tank 72: Supply pipe 72a:Tip 73: Opening and closing valve 80: Grinding equipment 81: Chuck table 82: Grinding means 83: Rotation axis 84: Wheel mount 85: Grinding wheel 86: Grinding wheel G1: First resin G2: Second resin

Claims

1. A method for straightening a curved plate-like object by flattening the plate-like object, comprising the steps of: a resin preparation step of preparing a first resin that shrinks and hardens when irradiated with ultraviolet light, and is relatively easily peeled off from the plate-like object, and a second resin that shrinks and hardens when irradiated with ultraviolet light, and is relatively firmly attached to the plate-like object; a first coating step of coating the first resin in a central region of the surface of the curved, mountain-shaped plate-like object and forming an uncoated region in the peripheral region where the first resin is not coated, or coating the second resin in a peripheral region of the surface of the curved, mountain-shaped plate-like object and forming an uncoated region in the central region where the second resin is not coated; a second coating step of coating one of the first resin and the second resin so as to cover the other resin coated in the first coating step and the uncoated region, after the first coating step; an ultraviolet irradiation step of irradiating the first resin and the second resin with ultraviolet light to cause them to shrink and harden; A curve correction method comprising the steps of:

2. The curvature correction method described in claim 1, wherein, in the first coating step, a first resin is applied to the central region of the surface of the plate-like object, and then, after the first coating step, an ultraviolet irradiation step is carried out to harden the first resin, and then, a second coating step is carried out in which the second resin is applied to cover the first resin and the uncoated region of the outer circumferential region, and the ultraviolet irradiation step is carried out to shrink and harden the second resin.

3. The curvature correction method described in claim 1, wherein, in the first coating step, a second resin is applied to the peripheral region of the surface of the plate-like object, and then, after the first coating step, an ultraviolet irradiation step is carried out to harden the second resin, and then, a second coating step is carried out in which the first resin is applied to cover the second resin and the uncoated region of the central region, and an ultraviolet irradiation step is carried out to shrink and harden the first resin.

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