Wafer holding device and wafer processing method using the wafer holding device

Abstract

Provided are a wafer holding device and a wafer processing method using the wafer holding device, wherein the wafer holding device can perform processing to appropriately remove the undulations of the wafer. The wafer holding device holds the wafer, wherein the wafer holding device includes: a holding portion including a plurality of piezoelectric elements each having a suction path selectively connected to a suction source, wherein the front end surfaces of the plurality of piezoelectric elements constitute a holding surface for holding the wafer; a frame supporting the holding portion; and a control unit controlling the voltage applied to the plurality of piezoelectric elements in accordance with the undulations of the wafer, so that the holding surface constituted by the front end surfaces of the plurality of piezoelectric elements corresponds to the undulations of the wafer.

Description

Technical Field

[0001] The present invention relates to a wafer holding device for holding a wafer and a wafer processing method using the wafer holding device. Background Art

[0002] A wafer having a functional layer stacked on the upper surface of a substrate and multiple devices such as IC and LSI formed on the functional layer is divided into individual device chips by a cutting device or a laser processing device. The divided device chips are used in electronic devices such as mobile phones and personal computers.

[0003] The wafer is produced by slicing an ingot of silicon or the like using a wire saw, for example, and then grinding both surfaces to finish the wafer into flat surfaces.

[0004] The applicant has also obtained a patent for an invention of a method for effectively removing the undulation (warp) of a wafer (see Patent Document 1).

[0005] Patent Document 1: Japanese Patent No. 5324212

[0006] However, there is a problem that after the gel resin is fused with the wafer undulations, internal stress is generated in the process of curing the resin, causing the wafer undulations to slightly deform and harden, and even if the wafer is ground, the undulations cannot be properly removed. Summary of the invention

[0007] Therefore, an object of the present invention is to provide a wafer holding device capable of performing processing to appropriately remove the undulations of a wafer and a method for processing a wafer using the wafer holding device.

[0008] According to one embodiment of the present invention, a chip holding device is provided for holding a chip, wherein the chip holding device comprises: a holding portion, which includes a plurality of advance and retreat elements each having a suction hole selectively connected to a suction source, wherein the front end surfaces of the plurality of advance and retreat elements constitute a holding surface for holding the chip; a frame, which supports the holding portion; and a control unit, which controls the length of the advance and retreat element corresponding to the ups and downs of the chip, and the length of the advance and retreat element is controlled by the control unit corresponding to the ups and downs of the chip, thereby imitating the ups and downs of the chip to hold the chip.

[0009] Preferably, the advancing and retracting elements are formed of piezoelectric elements, and the control unit controls the voltage applied to each piezoelectric element so that the holding surface formed of the front end surface corresponds to the fluctuation of the wafer.

[0010] According to another aspect of the present invention, a method for processing a wafer is provided, wherein the method for processing a wafer uses a wafer holding device, wherein the wafer holding device comprises: a holding portion, which includes a plurality of advance-retract elements selectively connected to suction sources, respectively, wherein the front end surfaces of the plurality of advance-retract elements constitute a holding surface for holding the wafer; a frame, which supports the holding portion; and a control unit, which controls the lengths of the plurality of advance-retract elements in accordance with the ups and downs of the wafer, wherein the wafer has a first surface and a second surface on the opposite side of the first surface, wherein the method for processing the wafer comprises the following steps: an ups and downs detection step, wherein the ups and downs detection step is performed to detect the ups and downs of the wafer. The undulation of the first surface is detected; an undulation generating step is to control the lengths of the plurality of advancing and retreating elements of the chip holding device to generate undulations on the holding surface corresponding to the undulations of the chip; a holding step is to hold the chip using the holding surface in accordance with the undulations of the chip; a resin laying step is to lay a gel-like resin on a substrate having a flat surface; a resin hardening step is to make the second surface of the chip face the substrate, press the gel-like resin to lay the gel-like resin on the second surface of the chip and harden the gel-like resin; and a detaching step is to detach the chip from the substrate together with the hardened resin.

[0011] The preferred chip processing method also has the following steps: a second surface holding step, using a chuck worktable to hold the second surface of the chip covered with hardened resin; a first surface flattening step, using a grinding tool to grind the first surface of the chip held by the chuck worktable to finish it into a flat surface; a resin stripping step, after implementing the first surface flattening step, stripping the hardened resin from the chip; a first surface holding step, after implementing the resin stripping step, holding the first surface of the chip by the chuck worktable; and a second surface flattening step, using the grinding tool to grind the second surface of the chip held by the chuck worktable to finish it into a flat surface.

[0012] The wafer holding device of the present invention is configured to hold the wafer by imitating the undulation of the wafer, so even if internal stress is generated during the curing process of the resin after the gel-like resin is fused with the undulation of the wafer, the undulation of the wafer is maintained by the holding portion, and the wafer will not be deformed even if the resin is cured. Therefore, by using the wafer holding device of the present invention, the undulation can be appropriately removed by grinding the wafer after the resin is cured.

[0013] According to the wafer processing method of the present invention, even if internal stress is generated in the resin curing step after the gel-like resin is fused with the wafer undulations, the wafer undulations are maintained by the holding portion, and the wafer will not be deformed even if the resin is cured. Therefore, by implementing the wafer processing method of the present invention, the wafer can be ground after the resin is cured to appropriately remove the undulations. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a perspective view of a wafer holding device according to an embodiment of the present invention.

[0015] Figure 2 yes Figure 1 A partial cross-sectional view of a wafer holding device is shown.

[0016] Figure 3 It is shown that the Figure 1 Schematic diagram of the X-coordinate and Y-coordinate (position data) of each piezoelectric element in the random access memory of the control unit shown.

[0017] Figure 4 It is a schematic cross-sectional view of a wafer.

[0018] Figure 5 It is a perspective view showing a state where the undulation detection process is performed.

[0019] Figure 6 It is a perspective view showing a state where the undulation generating step is performed.

[0020] Figure 7 It is a perspective view showing a state in which a holding step is performed.

[0021] Figure 8 It is a perspective view showing a state where a resin laying process is being performed.

[0022] Fig. 9 It is a perspective view showing a state where a resin curing step is performed.

[0023] Fig.10 It is a perspective view showing a state where a detaching process is performed.

[0024] Fig.11 It is a perspective view showing a state where the other surface supporting step is performed.

[0025] Fig.12 It is a perspective view showing a state where a one-side planarization step is performed.

[0026] Description of symbols

[0027] 2: chip holding device; 4: holding part; 4a: holding surface; 6: frame; 8: piezoelectric element (advance and retraction element); 28: control unit; 36: chip; 36a: first surface of the chip; 36b: second surface of the chip; 40: substrate; 40a: flat surface of the substrate; 42: gel resin; 44: chuck worktable; 58: grinding tool. DETAILED DESCRIPTION

[0028] Hereinafter, a wafer holding device and a wafer processing method using the wafer holding device according to an embodiment of the present invention will be described with reference to the drawings.

[0029] First, refer to Figure 1 and Figure 2 The wafer holding device constructed according to the present invention is described. Figure 1 As shown, the wafer holding device, which is generally indicated by reference numeral 2 , includes: a holding portion 4 having a holding surface 4 a for holding a wafer; and a frame 6 for supporting the holding portion 4 .

[0030] The holding portion 4 is composed of a plurality of advancing and retreating elements. Figure 2 As shown, each advancing and retreating element is composed of a prismatic piezoelectric element 8, and the front end surface 8a ( Figure 2 The upper end surface in the middle) moves forward and backward in the length direction. Figure 2 A pair of terminals 10 are provided on the lower end surface 8b in the piezoelectric element 8. In addition, a suction hole 12 extending along the length direction from the front end surface 8a to the base end surface 8b is formed in each piezoelectric element 8. And, in the holding portion 4, the front end surfaces 8a of the plurality of piezoelectric elements 8 constitute a circular holding surface 4a as a whole. In addition, the size of the front end surface 8a and the base end surface 8b of the piezoelectric element 8 can be about 0.5mm×0.5mm, and the length of the piezoelectric element 8 can be about 10cm.

[0031] like Figure 2 As shown, the frame 6 has: a cylindrical peripheral wall 14; a circular inner wall 16 disposed inside the peripheral wall 14; and a circular end wall 18 disposed at the end of the peripheral wall 14. A plurality of piezoelectric elements 8 are housed in a housing space defined by the peripheral wall 14 and the inner wall 16. Figure 2 As shown, the inner wall 16 is provided with a plurality of electrodes 20 connected to the terminals 10 of the piezoelectric elements 8 and a plurality of through holes 22 connected to the suction holes 12 of the piezoelectric elements 8. In addition, a circular opening 24 is formed in the end wall 18, and a cylindrical connection portion 26 protruding outward from the periphery of the circular opening 24 is attached to the end wall 18.

[0032] Each suction hole 12 of the plurality of piezoelectric elements 8 constituting the holding portion 4 is selectively connected to a suction source (not shown) via each through hole 22 of the inner wall 16, a connection portion 26, and an appropriate flow path (not shown). Then, in the holding portion 4, the suction source is operated to generate suction force on the holding surface 4a, so that the wafer is sucked and held by the holding surface 4a.

[0033] like Figure 1As shown, the wafer holding device 2 further includes a control unit 28, which controls the advancing and retreating element (in this embodiment, the piezoelectric element 8) in accordance with the fluctuation of the wafer. The control unit 28 is composed of a computer and includes: a central processing unit (CPU) 30, which performs calculations according to a control program; a read-only memory (ROM) 32, which stores the control program, etc.; and a readable and writable random access memory (RAM) 34, which stores the calculation results, etc. The random access memory 34 stores Figure 3 The X-coordinate and Y-coordinate (position data) of each piezoelectric element 8 shown in FIG. 2 are stored in the random access memory 34. In addition, in the control unit 28, the fluctuation data of the wafer detected by the fluctuation detection device 38 described later is stored in the random access memory 34, and the voltage applied to each piezoelectric element 8 corresponding to each part of the wafer is controlled based on the fluctuation data of the wafer stored in the random access memory 34, and the length of each piezoelectric element 8 is adjusted, so that the fluctuation corresponding to the fluctuation of the wafer is generated on the holding surface 4a. And, in the wafer holding device 2, after the fluctuation corresponding to the fluctuation of the wafer is generated on the holding surface 4a, the wafer is adsorbed by the holding surface 4a, so that the wafer can be held by imitating the fluctuation of the wafer.

[0034] Next, refer to Figures 4 to 12 A method for processing a wafer using the above-described wafer holding device 2 will be described.

[0035] exist Figure 4 A partial cross-sectional view of a disk-shaped wafer 36 capable of implementing the wafer processing method of the present invention is shown in FIG. Figure 5 36 is a perspective view of a wafer 36. The wafer 36 is an initial stage wafer obtained by slicing a cylindrical ingot of silicon or the like into a predetermined thickness using a wire saw, and has undulations (warping) due to resistance generated during slicing. Figure 4 In the figure, for the sake of convenience, the undulations of the wafer 36 are exaggeratedly shown. After the first surface 36a of the wafer 36 and the second surface 36b on the side opposite to the first surface are ground and finished into flat surfaces, a functional layer is stacked on the first surface 36a or the second surface 36b, and a plurality of devices such as IC and LSI are formed on the functional layer.

[0036] In this embodiment, the undulation detection step is first performed to detect the undulation of the first surface 36a of the wafer 36. The undulation detection step can be performed, for example, Figure 5The undulation detection device 38 is implemented by a portion of which is shown in FIG. The undulation detection device 38 can be constituted by, for example, an optical height detection device. In the undulation detection process, after the length direction of the undulation detection device 38 is aligned with the Y-axis direction, the undulation detection device 38 and the chip 36 are relatively moved in the X-axis direction, and the first surface 36a of the chip 36 is divided into a mesh of appropriate size in the X-axis direction and the Y-axis direction to obtain a micro area (for example, an area of ​​about 0.5mm×0.5mm), and each Z-axis position of the micro area is measured in association with the X-coordinate and the Y-coordinate, thereby detecting the undulation of the first surface 36a of the chip 36. Then, the undulation data of the first surface 36a of the chip 36 detected by the undulation detection device 38 is stored in the random access memory 34 of the control unit 28. In addition, the X-axis direction is Figure 5 The direction indicated by the arrow X in the middle, the Y axis direction is Figure 5 The direction indicated by the arrow Y is perpendicular to the X-axis direction, and the Z-axis direction is Figure 5 The direction indicated by the arrow Z is a direction perpendicular to the X-axis direction and the Y-axis direction. In addition, the plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

[0037] After the undulation detection step is performed, the undulation generation step is performed to control the advancing and retreating elements of the wafer holding device 2 in accordance with the undulation of the wafer 36, thereby generating undulation on the holding surface 4a. Figure 6 To explain, in the undulation generation process, first, the Z-axis direction position of the undulation data stored in the random access memory 34 is converted into a voltage value by the control unit 28. Next, based on the undulation data obtained by converting the Z-axis direction position into a voltage value, the control unit 28 controls the voltage applied to each piezoelectric element 8 corresponding to each micro-region of the wafer 36 in association with the X-coordinate and the Y-coordinate, and adjusts the length of each piezoelectric element 8, thereby generating undulation corresponding to the undulation of the first surface 36a of the wafer 36 on the holding surface 4a.

[0038] After the undulation generating step is performed, a holding step is performed to hold the wafer 36 by making the holding surface 4a coincide with the undulation of the wafer 36. Figure 7 To explain, in the holding process, first, the undulation of the first surface 36a of the wafer 36 is made to coincide with the undulation of the holding surface 4a generated in the undulation generating process, and then the first surface 36a of the wafer 36 is brought into contact with the holding surface 4a. Next, the suction source connected to the holding portion 4 is operated to generate suction force on the holding surface 4a, thereby imitating the undulation of the wafer 36 and sucking and holding the wafer 36 by the holding surface 4a.

[0039] After the maintenance process is implemented, Figure 8As shown in the figure, a resin laying process is performed to lay a gel resin 42 on a substrate 40 having a flat surface 40a. As the gel resin 42 that can be used in the resin laying process, there can be cited an ultraviolet curing resin that is cured by ultraviolet irradiation, a thermosetting resin that is cured by heating, or a thermoplastic resin that is liquefied by heating and cured by cooling. In addition, when an ultraviolet curing resin is used as the gel resin 42, the substrate 40 is formed of a material that transmits ultraviolet light, such as glass.

[0040] After the resin application step, a resin curing step is performed, in which the second surface 36b of the wafer 36 faces the substrate 40, and the gel resin 42 is pressed to apply the gel resin 42 on the second surface 36b of the wafer 36 and then cured. Fig. 9 To explain, in the resin curing process, first, while the wafer 36 is being held by suction by the holding surface 4a of the holding portion 4, the gel resin 42 is pressed by the second surface 36b of the wafer 36. As a result, the gel resin 42 is spread and fused with the undulations of the wafer 36, and the gel resin 42 can be spread on the second surface 36b of the wafer 36. Next, the gel resin 42 is cured by using a curing member (e.g., an ultraviolet irradiation member, a heating member, or a cooling member) corresponding to the properties of the gel resin 42. At this time, the wafer 36 is held by the holding surface 4a of the holding portion 4 in a manner imitating the undulations of the wafer 36, so that the undulations of the wafer 36 are maintained by the holding portion 4, and the wafer 36 will not be deformed even if the gel resin 42 is cured.

[0041] After the resin curing step is performed, a detaching step is performed to detach the wafer 36 from the substrate 40 together with the cured resin 42. Fig.10 As shown, in the detaching step, the wafer 36 is detached from the substrate 40 together with the cured resin 42. Then, the operation of the suction source connected to the holding portion 4 is stopped, and the suction force of the holding surface 4a is released, so that the wafer 36 is detached from the wafer holding device 2.

[0042] After the release process is performed, the other side support process is performed, and the second side 36b of the wafer 36 on which the hardened resin 42 is laid is supported by the chuck table. In the other side support process, for example, Fig.11 The chuck table 44 is shown. A porous adsorption chuck 46 connected to a suction member (not shown) is arranged at the upper end portion of the chuck table 44. In addition, the chuck table 44 is configured to be rotatable around an axis extending in the vertical direction as a rotation center, and is configured to be movable between a workpiece loading and unloading position for loading and unloading a workpiece and a grinding position below a grinding device 48 described later.

[0043] Reference Fig.11 To continue the description, in the other-side supporting step, the wafer 36 is first placed on the upper surface of the adsorption chuck 46 with the first surface 36a of the wafer 36 facing upward. Then, the suction member is operated to generate a suction force on the upper surface of the adsorption chuck 46, so that the second surface 36b of the wafer 36 on which the cured resin 42 is laid is adsorbed and supported by the chuck table 44.

[0044] After the other-side support step is performed, a one-side flattening step is performed to grind the first surface 36a of the wafer 36 supported by the chuck table 44 using a grinding tool to finish the first surface 36a into a flat surface. The one-side flattening step can be performed, for example, Fig.12 The grinding device 48 is implemented by a grinding device 48, a part of which is shown in FIG. The grinding device 48 includes: a main shaft 50, which is connected to a main shaft motor (not shown) and extends in the up-down direction; and a disc-shaped grinding wheel mounting seat 52, which is fixed to the lower end of the main shaft 50. An annular grinding wheel 56 is fixed to the lower surface of the grinding wheel mounting seat 52 by bolts 54. A plurality of grinding tools 58 are fixed to the outer peripheral edge of the lower surface of the grinding wheel 56 and are arranged in an annular shape at intervals in the circumferential direction.

[0045] Reference Fig.12 To continue the description, in the grinding process, first, the chuck table 44 is moved from the workpiece loading and unloading position to the grinding position ( Fig.12 ). Next, the chuck table 44 is rotated counterclockwise when viewed from above at a predetermined rotation speed (e.g., 300 rpm). In addition, the spindle 50 is rotated counterclockwise when viewed from above at a predetermined rotation speed (e.g., 6000 rpm). Next, the spindle 50 is lowered by using a lifting member (not shown) of the grinding device 48 so that the grinding tool 58 contacts the first surface 36a of the wafer 36. Then, the spindle 50 is lowered at a predetermined grinding feed speed (e.g., 1.0 μm / s). Thus, the first surface 36a of the wafer 36 can be ground and finished into a flat surface by using the grinding tool 58.

[0046] After the one-side planarization process is performed, a one-side support process is performed in which the hardened resin 42 is peeled off from the wafer 36 and the first surface 36a of the wafer 36 is supported by the chuck table 44, and then the other-side planarization process is performed in which the second surface 36b of the wafer 36 supported by the chuck table 44 from which the hardened resin 42 is peeled off is ground by the grinding tool 58 to be finished into a flat surface. The one-side support process and the other-side planarization process can be performed in the same manner as the other-side support process and the one-side planarization process described above, as long as the hardened resin 42 is peeled off from the second surface 36b of the wafer 36 and the first surface 36a and the second surface 36b of the wafer 36 are exchanged with each other, and therefore detailed descriptions are omitted.

[0047] As described above, in this embodiment, the wafer 36 is held by the holding surface 4a of the holding portion 4 in a manner imitating the undulations of the wafer 36, so that the undulations of the wafer 36 are maintained by the holding portion 4, and the wafer 36 does not deform even if the gel-like resin 42 is hardened in the resin hardening step. Therefore, by using the wafer holding device 2 to implement the above-mentioned wafer processing method, the wafer 36 can be ground to appropriately remove the undulations.

Claims

1. A method for processing a wafer, the method for processing a wafer using a wafer holding device, the wafer holding device imitating the ups and downs of the wafer to hold the wafer, the wafer holding device consisting of at least a holding portion and a frame, the holding portion having a holding surface for holding the wafer, the frame supporting the holding portion, the holding portion consisting of a plurality of columnar advancing and retreating elements arranged in a lattice, and the holding surface consisting of the front end surfaces of the plurality of columnar advancing and retreating elements, suction holes for sucking and holding the wafer are formed on the front end surfaces of the plurality of columnar advancing and retreating elements respectively, the wafer holding device having a control unit, the control unit controlling the plurality of columnar advancing and retreating elements corresponding to the ups and downs of the wafer, the wafer having a first surface and a second surface on the opposite side of the first surface, wherein, The wafer processing method has the following steps: A fluctuation detection step of dividing the first surface of the wafer into a mesh having a size corresponding to the size of the front end surfaces of the plurality of columnar advancing and retracting elements in the X-axis direction and the Y-axis direction and measuring each Z-axis direction position of the area divided into the mesh in association with the X-coordinate and the Y-coordinate, thereby detecting the fluctuation of the first surface of the wafer; A undulation generating step of controlling the plurality of columnar advancing and retreating elements of the wafer holding device in accordance with the undulation of the wafer to generate undulation on the holding surface; A holding step, wherein the ups and downs of the wafer detected in the ups and downs detection step are made consistent with the ups and downs of the holding surface generated in the ups and downs generation step and suction is generated in each suction hole of the plurality of columnar advancing and retreating elements, and the holding surface on which the ups and downs are generated is used to hold the first surface of the wafer and maintain the ups and downs of the wafer; A resin laying step of laying a gel-like resin on a substrate having a flat surface; a resin curing step of placing the second surface of the wafer on the second surface of the wafer and curing the gel resin by pressing the gel resin while the wafer is held by the holding surface of the holding portion, with the second surface of the wafer facing the substrate; and In the detaching step, the wafer is detached from the substrate together with the cured resin.

2. The wafer processing method according to claim 1, wherein: The wafer processing method also has the following steps: a second surface holding step of holding the second surface of the wafer on which the hardened resin is laid using a chuck table; a first surface flattening step of grinding the first surface of the wafer held by the chuck table with a grinding tool to finish the first surface into a flat surface; A resin stripping step of stripping the hardened resin from the wafer after the first surface flattening step is performed; a first surface holding step of holding the first surface of the wafer using the chuck table after the resin stripping step is performed; and In the second surface flattening step, the second surface of the wafer held by the chuck table is ground using the grinding tool to finish the second surface into a flat surface.

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