Wafer reclamation method

Abstract

To effectively remove a film formed on a wafer by grinding.SOLUTION: Using a thickness measuring device 82, a film 103 starts to be ground while the thickness of the wafer 100 is measured through the film 103. When the measured value by the thickness measuring device 82 starts to decrease, it is determined that the film 103 has been removed, and the grinding is stopped. Therefore, even when the thickness of the film 103 is unknown, while suppressing the film 103 remaining on the wafer 100 and excessively grinding of an upper surface 101 of the wafer 100, the film 103 can be removed well from the wafer 100 by grinding.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for reclamation of a wafer. [Background technology]

[0002] Devices formed on a wafer are configured to include thin films, such as insulating films, conductive films, and semiconductor films, on the upper surface of the wafer. These thin films are formed, for example, by chemical vapor deposition (CVD).

[0003] When fabricating a device, a thin film is first experimentally formed on a test wafer to select film formation conditions suitable for device formation. Films are then formed on product wafers under the selected film formation conditions.

[0004] This test wafer is a wafer on which only a film containing no circuitry is formed for the purpose of selecting film formation conditions, and is discarded after the test.

[0005] In order to reduce costs, there is a technique for reclaiming test wafers by removing the film by polishing, as disclosed in Patent Document 1. However, if the film is thick, there is a problem that it takes a long time to remove the film. Therefore, the technique disclosed in Patent Document 2 removes the film by grinding. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-002606 [Patent Document 2] Japanese Patent Publication No. 2020-061515 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the technology of Patent Document 2, because a preset amount is ground, when the thickness of the film is unknown, not only the film but also the wafer is ground, resulting in a thin wafer, which may make it difficult to reuse the wafer. Alternatively, the film may remain, making it necessary to grind again, which may require a lot of time for regeneration.

[0008] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to effectively remove a film formed on a wafer by grinding. [Means for solving the problem]

[0009] The first wafer reclamation method (first reclamation method) of the present invention is a wafer reclamation method in which the underside of a wafer having a film on its upper surface is held by a chuck table of a grinding device, and the film is ground and removed using a grinding wheel of the grinding device to reclaim the wafer. The grinding device is equipped with a non-contact thickness gauge that irradiates measurement light having a wavelength that is transparent to the film and the wafer from above the wafer, receives top-reflected light reflected from the top surface of the wafer through the film, and bottom-reflected light reflected from the bottom surface of the wafer through the film and the wafer, and measures the thickness of the wafer by spectral interference. Grinding of the film is started while measuring the thickness of the wafer through the film using the non-contact thickness gauge, and grinding is stopped when the measurement value measured by the non-contact thickness gauge begins to decrease. The second wafer reclamation method (second reclamation method) of the present invention is a wafer reclamation method in which the underside of a wafer having a film on its upper surface is held by a chuck table of a grinding device, and the film is ground and removed using a grinding wheel of the grinding device to reclaim the wafer. The grinding device is equipped with a non-contact thickness gauge that irradiates measurement light from above the wafer, the measurement light having a wavelength that is blocked by the film and transparent to the wafer, receives the top-reflected light reflected from the top surface of the wafer and the bottom-reflected light that passes through the wafer and is reflected from the bottom surface of the wafer, and measures the thickness of the wafer by spectral interference. Grinding of the film begins when the non-contact thickness gauge is unable to measure the wafer thickness due to the film blocking the measurement light, and grinding is terminated when the non-contact thickness gauge becomes able to measure the wafer thickness. The third wafer reclamation method (third reclamation method) of the present invention is a wafer reclamation method in which the underside of a wafer having a film on its upper surface is held by a chuck table of a grinding device, and the film is ground and removed using a grinding wheel of the grinding device to reclaim the wafer. The grinding device is equipped with a non-contact top surface height measuring device that irradiates measurement light from above the wafer, having a wavelength that is transparent to the film and a wavelength that is opaque to the wafer, receives the top surface reflected light reflected from the top surface of the wafer through the film, and measures the top surface height of the wafer by triangulation or spectral interference. Grinding of the film is started while measuring the top surface height of the wafer through the film using the non-contact top surface height measuring device, and grinding is terminated when the measurement value measured by the non-contact top surface height measuring device begins to decrease. In the first, second or third regeneration method, the grinding device may be provided with a height measuring device that measures the height of the film on the wafer held on the chuck table, and the height measuring device may measure the height of the film on the wafer, and the lower surface of the grinding wheel may be positioned at a height corresponding to the height measured by the height measuring device, and grinding of the film may be started. [Effects of the Invention]

[0010] In the first regeneration method, grinding of the film is started while measuring the thickness of the wafer through the film using a thickness gauge, and when the measured value by the thickness gauge starts to decrease, it is determined that the film has been removed and grinding is stopped. Therefore, even if the thickness of the film is unknown, it is possible to successfully remove the film from the wafer by grinding while suppressing the film from remaining on the wafer and the wafer from being excessively ground.

[0011] In the second regeneration method, grinding of the film begins when the film blocks the measurement light of the thickness gauge, preventing the thickness gauge from measuring the wafer thickness, and when the thickness gauge becomes able to measure the wafer thickness, it is determined that the film has been removed and grinding ends. Therefore, even when the film thickness is unknown, the film can be successfully removed from the wafer by grinding while preventing the film from remaining on the wafer and excessive grinding of the top surface of the wafer.

[0012] In the third regeneration method, a non-contact top surface height measuring device is used to measure the top surface height of the wafer through the film while grinding the film is started, and when the measurement value from the non-contact top surface height measuring device begins to decrease, it is determined that the film has been removed and grinding is stopped. Therefore, even if the thickness of the film is unknown, the film can be successfully removed from the wafer by grinding while preventing the film from remaining on the wafer and the wafer from being ground excessively. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a perspective view showing the configuration of a grinding device. [Figure 2] FIG. 2 is an explanatory diagram showing the configuration of a workpiece holding mechanism. [Figure 3] FIG. 2 is an explanatory diagram showing the configuration of a workpiece holding mechanism. [Figure 4] FIG. 2 is an explanatory diagram showing the configuration of a non-contact upper surface height measuring device. [Figure 5] FIG. 10 is an explanatory diagram showing another configuration of the non-contact top surface height measuring device. DETAILED DESCRIPTION OF THE INVENTION

[0014] As shown in FIG. 1, the grinding apparatus 1 according to this embodiment is an apparatus for grinding a wafer 100 as an object to be ground. The wafer 100 is, for example, a semiconductor wafer for testing, and has an upper surface 101 and a lower surface 102. The wafer 100 has a film 103 on the upper surface 101. This film 103 was formed on the wafer 100 in a test for selecting film formation conditions. The wafer 100 is reclaimed by removing the film 103 in the grinding apparatus 1.

[0015] As shown in FIG. 1, the grinding apparatus 1 includes a rectangular parallelepiped base 10, a column 11 extending upward, and a control unit 7 that controls each member of the grinding apparatus 1.

[0016] An opening 13 is provided on the upper surface side of the base 10. A wafer holding mechanism 30 is disposed within the opening 13. The wafer holding mechanism 30 has a chuck table 20 having a holding surface 22 for holding the wafer 100.

[0017] Furthermore, as shown in FIG. 2, the wafer holding mechanism 30 includes a table base 55 that supports the chuck table 20, a table rotation mechanism 50 that rotates the chuck table 20 and the table base 55, and an inclination adjustment mechanism 40 that adjusts the inclination of the chuck table 20.

[0018] 2, the chuck table 20 includes a disk-shaped porous member 21 and a frame 23 that houses the porous member 21 so that the top surface of the porous member 21 is exposed. The top surface of the porous member 21 is a holding surface 22 that suction-holds the wafer 100. The holding surface 22 is formed as a conical surface with an apex at the center, and is connected to a suction source (not shown) to suction-hold the wafer 100. A frame surface 24, which is the top surface of the frame 23, is formed flush with the holding surface 22.

[0019] A table base 55 that supports the chuck table 20 is provided below the chuck table 20. A table rotation mechanism 50 that rotatably supports the table base 55 is disposed below the table base 55.

[0020] 2, the table rotation mechanism 50 includes a motor 521, a driving pulley 522 attached to the motor 521, a driven pulley 524 connected to the driving pulley 522 via an endless belt 523, and a rotary joint 525 disposed below the driven pulley 524. The motor 521 is attached to an annular member 45 (described later) via a fixing member 526. The driven pulley 524 is supported on a narrow-diameter portion of the lower part of the table base 55. The rotary joint 525 is used to connect the suction source and the holding surface 22.

[0021] In the table rotation mechanism 50, a motor 521 rotates a driving pulley 522, thereby rotating an endless belt 523 and a driven pulley 524. As a result, the table base 55 and the chuck table 20 are rotated around the rotation axis 221 of the holding surface 22 as shown by an arrow 502.

[0022] Additionally, around the periphery of the table base 55, an inclination adjustment mechanism 40 for adjusting the inclination of the holding surface 22 of the chuck table 20 is provided.

[0023] The tilt adjustment mechanism 40 includes an internal base 41 that is positioned below the chuck table 20 and has an opening 412 that surrounds the table rotation mechanism 50, a tilt adjustment shaft 42 that passes through the internal base 41, a fixed shaft 43 that is fixed to the internal base 41, and an annular member 45.

[0024] The annular member 45 rotatably supports the table base 55 so as to surround the table base 55 via a connecting portion 46 including a bearing.

[0025] The fixed shaft 43 has its upper end fixed to the lower surface of the annular member 45 and its lower end fixed to the upper surface of the internal base 41 .

[0026] The inclination adjustment shaft 42 is provided to pass through a through-hole 411 extending in the Z-axis direction formed in the internal base 41. In addition, a male screw 421 is formed on the upper end side of the inclination adjustment shaft 42.

[0027] Furthermore, a through-hole 450 is formed in the portion of the annular member 45 that corresponds to the inclination adjustment shaft 42. The through-hole 450 is formed with a female screw 451 that has a shape that corresponds to the male screw 421 of the inclination adjustment shaft 42. The tilt adjustment shaft 42 is inserted into this through-hole 450 and supports the annular member 45 with its male thread 421 screwed into the female thread 451 of the through-hole 450 .

[0028] The tilt adjustment mechanism 40 further includes a drive unit 48 that rotationally drives the tilt adjustment shaft 42, and a fixing member 47 that fixes the drive unit 48 to the underside of the internal base 41. When the drive unit 48 rotationally drives the tilt adjustment shaft 42, the portion of the annular member 45 where the through hole 450 into which the tilt adjustment shaft 42 is inserted (the +Y direction side in FIG. 2) moves up and down along the Z axis direction. As a result, the table base 55 supported by the annular member 45 and the +Y direction side of the chuck table 20 supported by the table base 55 also move up and down along the Z axis direction. This adjusts the tilt of the holding surface 22 of the chuck table 20.

[0029] In this embodiment, the tilt adjustment mechanism 40 is provided with two tilt adjustment shafts 42 (one of which is not shown) and one fixed shaft 43, and one or both of the tilt adjustment shafts 42 are rotationally driven to adjust the tilt of the holding surface 22 of the chuck table 20. These two tilt adjustment shafts 42 and one fixed shaft 43 are provided on the internal base 41, for example, at intervals of 120 degrees around the center of the holding surface 22.

[0030] The tilt adjustment mechanism 40 may be configured to include one tilt adjustment shaft 42 and two fixed shafts 43, and to adjust the tilt of the holding surface 22 of the chuck table 20 by driving one tilt adjustment shaft 42 to rotate. Alternatively, the tilt adjustment mechanism 40 may be configured to include three tilt adjustment shafts 42, and to adjust the tilt of the holding surface 22 of the chuck table 20 by driving any one of the tilt adjustment shafts 42 to rotate.

[0031] 1, a cover plate 39 that moves in the Y-axis direction together with the chuck table 20 is provided around the periphery of the chuck table 20. A bellows cover 12 that expands and contracts in the Y-axis direction is connected to the cover plate 39. A Y-axis direction moving mechanism (not shown) is disposed below the wafer holding mechanism 30. The Y-axis direction moving mechanism moves the wafer holding mechanism 30 in the Y-axis direction relative to the grinding mechanism 70.

[0032] A column 11 erected on the +Y direction side of the base 10 is provided with a grinding mechanism 70 for grinding the wafer 100 and an elevation mechanism 60.

[0033] The lifting mechanism 60 moves the grinding mechanism 70 in the Z-axis direction (grinding feed direction), which is a direction perpendicular to the holding surface 22 of the chuck table 20.

[0034] The lifting mechanism 60 includes a pair of Z-axis guide rails 61 parallel to the Z-axis direction, a Z-axis moving table 63 that slides on the Z-axis guide rails 61, a Z-axis ball screw 62 parallel to the Z-axis guide rails 61, a Z-axis motor 64, a Z-axis encoder 65, and a holder 66 attached to the Z-axis moving table 63. The holder 66 holds a grinding mechanism 70.

[0035] The Z-axis moving table 63 is slidably installed on the Z-axis guide rail 61. A nut portion (not shown) is fixed to the Z-axis moving table 63. A Z-axis ball screw 62 is threadedly engaged with this nut portion. A Z-axis motor 64 is connected to one end of the Z-axis ball screw 62.

[0036] In the lifting mechanism 60, the Z-axis motor 64 rotates the Z-axis ball screw 62, causing the Z-axis moving table 63 to move up and down in the Z-axis direction along the Z-axis guide rail 61. As a result, a holder 66 attached to the Z-axis moving table 63 and a grinding mechanism 70 held by the holder 66 move up and down in the Z-axis direction together with the Z-axis moving table 63. In addition, the Z-axis encoder 65 detects the rotation angle of the Z-axis motor 64, thereby recognizing the height of a grinding wheel 77 (described later) of the grinding mechanism 70, which is moved up and down by the lifting mechanism 60.

[0037] The grinding mechanism 70 grinds the wafer 100 held on the holding surface 22 of the chuck table 20 with a grinding wheel 77. As shown in Fig. 1, the grinding mechanism 70 includes a spindle housing 71 held by the holder 66, a spindle 72 for rotating the grinding wheel 77, a spindle motor 73 for driving the spindle 72 to rotate, a wheel mount 74 attached to the lower end of the spindle 72, and a grinding wheel 75 supported by the wheel mount 74.

[0038] The spindle 72 extends along the Z-axis direction so as to be perpendicular to the holding surface 22 of the chuck table 20, and is rotatably supported by the spindle housing 71. The spindle motor 73 is connected to the upper end side of the spindle 72. The spindle motor 73 causes the spindle 72 to rotate as indicated by the arrow 503 around a spindle rotation axis 721 extending in the Z-axis direction, as shown in FIG.

[0039] 1 and 2, the wheel mount 74 is formed in a disk shape and is fixed to the lower end of the spindle 72. The wheel mount 74 supports a grinding wheel 75.

[0040] The grinding wheel 75 is formed so that its outer diameter is approximately the same as the outer diameter of the wheel mount 74. The grinding wheel 75 includes an annular wheel base 76 made of a metal material.

[0041] A plurality of grinding wheels 77 are fixed to the underside of the wheel base 76 in a circular arrangement around the entire circumference. The grinding wheels 77 are rotated together with the spindle 72 by the spindle motor 73 around a spindle rotation axis 721 passing through the center of the wheel base 76, and grind the upper surface 101 of the wafer 100 held on the chuck table 20 or the film 103 formed on this upper surface 101.

[0042] As shown in FIG. 1, a measuring mechanism 80 for measuring the height and thickness of the wafer 100 is disposed on the side of the opening 13 in the base 10 .

[0043] The measuring mechanism 80 has a height measuring device 81 that measures the height of the wafer 100, a thickness measuring device 82 that measures the thickness of the wafer 100, an arm portion 83 that supports the height measuring device 81 and the thickness measuring device 82 at the tip, and a support member 84 that can support and rotate the arm portion 83.

[0044] The height measuring device 81 measures the height of the film 103 formed on the upper surface 101 of the wafer 100 as the height of the wafer 100. When the film 103 has been removed from the upper surface 101 of the wafer 100, the height measuring device 81 measures the height of the upper surface 101 of the wafer 100 as the height of the wafer 100.

[0045] In this embodiment, the height measuring device 81 is a contact-type height measuring device, and measures the height by bringing a contactor 85 (see Figure 2) into contact with the upper surface 101 or film 103 of the wafer 100 located below it. The height measuring device 81 may be a non-contact height measuring device, for example, a laser type or an ultrasonic type height measuring device.

[0046] The thickness measuring device 82 measures the thickness of the wafer 100 held on the chuck table 20. The thickness measuring device 82 is a non-contact thickness measuring device that irradiates the wafer 100 from above with measurement light having a wavelength that is transparent to the film 103 and the wafer 100, receives top-reflected light that is reflected off the top surface 101 of the wafer 100 through the film 103, and bottom-reflected light that is reflected off the bottom surface 102 of the wafer 100 through the film 103 and the wafer 100, and measures the thickness of the wafer by spectral interference. Thus, in this embodiment, the measurement light irradiated from the thickness measuring device 82 is light that is transmitted through the film 103 and the wafer 100.

[0047] 1 includes a CPU that performs arithmetic processing according to a control program, and a storage medium such as a memory. The control unit 7 controls the above-mentioned members of the grinding apparatus 1 to comprehensively control the components of the grinding apparatus 1. For example, the control unit 7 controls the above-mentioned members of the grinding apparatus 1 to perform a wafer reclamation method that removes the film 103 from the wafer 100 and reclaims the wafer 100.

[0048] This wafer reclamation method is described below. In this wafer reclamation method, the lower surface 102 of a wafer 100 having a film 103 on its upper surface 101 is held by the chuck table 20 of the grinding device 1, and the film 103 is ground and removed by the grinding wheel 77 of the grinding device 1, thereby reclaming the wafer 100.

[0049] [Holding process] Specifically, first, for example, an operator or a transfer device (not shown) places the wafer 100 on the holding surface 22 of the chuck table 20 with the lower surface 102 facing downward. Then, the control unit 7 connects a suction source (not shown) to the holding surface 22. As a result, the lower surface 102 of the wafer 100 is held by the holding surface 22 with the film 103 formed on the upper surface 101 of the wafer 100 facing upward, as shown in FIG.

[0050] [Grinding process] Next, the control unit 7 adjusts the position of the wafer holding mechanism 30 in the Y-axis direction using a Y-axis movement mechanism (not shown), thereby placing the chuck table 20 of the wafer holding mechanism 30 at a grinding position below the grinding mechanism 70. Thereafter, the control unit 7 rotates the grinding wheel 77 together with the spindle 72 using the spindle motor 73 (see FIG. 1) of the grinding mechanism 70. Furthermore, the control unit 7 rotates the chuck table 20 holding the wafer 100 using the table rotation mechanism 50 (see FIG. 2).

[0051] Next, as shown in FIG. 2, the control unit 7 measures the height of the film 103 formed on the upper surface 101 of the wafer 100 by bringing the contactor 85 of the height measuring device 81 into contact with the film 103.

[0052] Then, the control unit 7 uses the lifting mechanism 60 to lower the grinding mechanism 70, positioning the lower surface of the grinding wheel 77 at a height (for example, very close to the film 103) corresponding to the height measured by the height measuring device 81, and starts grinding the film 103. For example, the control unit 7 uses the lifting mechanism 60 to lower the grinding mechanism 70 at a relatively high initial speed, and positions the lower surface of the grinding wheel 77 very close to the film 103 on the wafer 100. Thereafter, the control unit 7 uses the lifting mechanism 60 to lower the grinding mechanism 70 at a relatively low grinding speed, and starts grinding the film 103.

[0053] At this time, the control unit 7 also uses the thickness measuring device 82 to measure the thickness of the wafer 100 through the film 103. That is, the control unit 7 starts grinding the film 103 while measuring the thickness of the wafer 100 through the film 103.

[0054] Then, when the thickness measurement value by the thickness measuring device 82 starts to decrease, the control unit 7 determines that the film 103 has been removed from the wafer 100 and the upper surface 101 of the wafer 100 has started to be ground, as shown in Figure 3, and ends the grinding.

[0055] As described above, in this embodiment, grinding of the film 103 is started while measuring the thickness of the wafer 100 through the film 103 using the thickness gauge 82, and when the measurement value by the thickness gauge 82 starts to decrease, it is determined that the film 103 has been removed, and grinding is terminated. Therefore, in this embodiment, even if the thickness of the film 103 is unknown, the film 103 can be satisfactorily removed from the wafer 100 by grinding while preventing the film 103 from remaining on the wafer 100 and preventing the top surface 101 of the wafer 100 from being excessively ground.

[0056] Furthermore, in this embodiment, the height of the film 103 formed on the upper surface 101 of the wafer 100 is measured by the height measuring device 81, and grinding is started after the lower surface of the grinding wheel 77 is positioned at a height (close to the film 103) corresponding to the measured height. Therefore, the grinding mechanism 70 including the grinding wheel 77 can be lowered at a relatively high speed until the lower surface of the grinding wheel 77 is close to (directly above) the film 103. This allows the time required for the grinding process to be shortened.

[0057] If the wafer 100 has a circuit, it is preferable to measure the thickness of a portion of the wafer 100 where no circuit is formed using the thickness gauge 82. This makes it possible to measure the thickness of the wafer 100 more accurately.

[0058] Furthermore, in the above-described embodiment, when the measured value of the thickness of the wafer 100 measured by the thickness gauge 82 starts to decrease, the control unit 7 determines that the upper surface 101 of the wafer 100 has started to be ground, and ends the grinding. Alternatively, when the measured value of the thickness measured by the thickness gauge 82 starts to decrease, the control unit 7 may grind the upper surface 101 of the wafer 100 by a preset grinding amount (for example, 2 to 3 μm), and then end the grinding.

[0059] Furthermore, the control unit 7 may continue to measure the height using the height measuring device 81 after starting grinding of the film 103. In this case, if the measurement value of the height measuring device 81 becomes low enough to determine that the film 103 has been removed, but the measurement value of the thickness of the wafer 100 measured by the thickness measuring device 82 does not start to decrease, the control unit 7 may determine that a malfunction has occurred in the height measuring device 81 or the thickness measuring device 82, and may stop grinding.

[0060] In this case, the control unit 7 can determine whether the measurement value of the height measuring device 81 has become sufficiently low based on, for example, an approximate value of the film thickness of the film 103. The approximate value of the film thickness of the film 103 may be set in advance in the grinding device 1 by, for example, an operator using an input / output panel (not shown).

[0061] Furthermore, in the above-described embodiment, the measurement light emitted from the thickness measuring device 82 is light that transmits through the film 103 and the wafer 100. In this regard, the measurement light emitted from the thickness measuring device 82 may be light that transmits through the wafer 100 but is blocked by the film 103. That is, the thickness measuring device 82 may be a non-contact thickness measuring device that irradiates the wafer 100 from above with measurement light that is blocked by the film 103 and has a wavelength that is transparent to the wafer 100, receives upper-surface reflected light that is reflected by the upper surface 101 of the wafer 100, and lower-surface reflected light that is transmitted through the wafer 100 and reflected by the lower surface 102 of the wafer 100, and measures the thickness of the wafer by spectral interference.

[0062] The wafer reclamation method in this case is similar to the reclamation method described above, in that the lower surface 102 of the wafer 100 having the film 103 on the upper surface 101 is held by the chuck table 20 of the grinding device 1, and the film 103 is ground and removed by the grinding wheel 77 of the grinding device 1, thereby reclamating the wafer 100.

[0063] In this case as well, the control unit 7 carries out the holding step described above to hold the wafer 100 on the holding surface 22.

[0064] Thereafter, the control unit 7 rotates the grinding wheel 77 and the chuck table 20 in the same manner as in the grinding process described above. 2, the control unit 7 causes the height measuring device 81 to measure the height of the film 103 formed on the upper surface 101 of the wafer 100 by bringing the contactor 85 of the height measuring device 81 into contact with the film 103. Then, the control unit 7 uses the lifting mechanism 60 to lower the grinding mechanism 70, positions the lower surface of the grinding wheel 77 at a height corresponding to the height measured by the height measuring device 81 (for example, very close to the film 103), and starts grinding the film 103.

[0065] At this time, the control unit 7 uses the thickness measuring device 82 to measure the thickness of the wafer 100 through the film 103. As described above, the measurement light of the thickness measuring device 82 is blocked by the film 103. Therefore, the control unit 7 starts grinding the film 103 from a state in which the thickness measuring device 82 cannot measure the thickness of the wafer 100 because the film 103 blocks the measurement light of the thickness measuring device 82.

[0066] Then, when the thickness measuring device 82 becomes able to measure the thickness of the wafer 100, the control unit 7 determines that the film 103 has been removed from the wafer 100, as shown in FIG. 3, and ends the grinding.

[0067] In this way, when the measurement light emitted from the thickness gauge 82 is light that is blocked by the film 103, grinding of the film 103 begins in a state where the thickness gauge 82 cannot measure the thickness of the wafer 100 because the film 103 blocks the measurement light of the thickness gauge 82, and grinding ends when the thickness gauge 82 becomes able to measure the thickness of the wafer 100. Therefore, even when the thickness of the film 103 is unknown, the film 103 can be satisfactorily removed from the wafer 100 by grinding while preventing the film 103 from remaining on the wafer 100 and preventing the top surface 101 of the wafer 100 from being excessively ground.

[0068] Also in this case, the control unit 7 may continue to measure the height using the height measuring device 81 after starting grinding of the film 103. Then, when the measurement value of the height measuring device 81 becomes low enough to determine that the film 103 has been removed, but the thickness of the wafer 100 cannot be measured using the thickness measuring device 82, the control unit 7 may determine that a malfunction has occurred in the height measuring device 81 or the thickness measuring device 82, and may stop grinding.

[0069] In the above-described embodiment, the grinding apparatus 1 is equipped with a thickness measuring device 82. In this regard, the grinding apparatus 1 may be equipped with a non-contact upper surface height measuring device 90 (see FIGS. 1 to 3) instead of or in addition to the thickness measuring device 82. The non-contact upper surface height measuring device 90 measures the upper surface height, which is the height of the upper surface 101 of the wafer 100 held on the chuck table 20.

[0070] 4, the non-contact top surface height measuring device 90 is a reflective measuring device that uses triangulation, and includes a light emitting element 91 and a light receiving element 92. The light emitting element 91 irradiates the wafer 100 with measurement light L1 from above the wafer 100. This measurement light L1 is light of a wavelength that is transmitted through a film 103 formed on the top surface 101 of the wafer 100 but is blocked by the wafer 100.

[0071] In the non-contact top surface height measuring device 90, measurement light L1 from a light emitting element 91 is irradiated onto the top surface 101 of the wafer 100 through a film 103. Furthermore, top surface reflected light L2 obtained when measurement light L1 is reflected by the top surface 101 is received by a light receiving element 92. Then, by detecting the receiving position of the top surface reflected light L2 on the light receiving element 92, the top surface height, which is the height of the top surface 101 of the wafer 100, can be measured.

[0072] In this way, the non-contact top surface height measuring device 90 is configured to irradiate measurement light L1 from above the wafer 100, which has a wavelength that is transparent to the film 103 and a wavelength that is opaque to the wafer 100, receive top surface reflected light L2 reflected by the top surface 101 of the wafer 100 through the film 103, and measure the top surface height of the wafer 100 by triangulation.

[0073] The wafer reclamation method in this case is similar to the reclamation method described above, in that the lower surface 102 of the wafer 100 having the film 103 on the upper surface 101 is held by the chuck table 20 of the grinding device 1, and the film 103 is ground and removed by the grinding wheel 77 of the grinding device 1, thereby reclamating the wafer 100.

[0074] In this case as well, the control unit 7 carries out the holding step described above to hold the wafer 100 on the holding surface 22.

[0075] Thereafter, the control unit 7 rotates the grinding wheel 77 and the chuck table 20 in the same manner as in the grinding process described above. 2, the control unit 7 causes the height measuring device 81 to measure the height of the film 103 formed on the upper surface 101 of the wafer 100 by bringing the contactor 85 of the height measuring device 81 into contact with the film 103. Then, the control unit 7 uses the lifting mechanism 60 to lower the grinding mechanism 70, positions the lower surface of the grinding wheel 77 at a height corresponding to the height measured by the height measuring device 81 (for example, very close to the film 103), and starts grinding the film 103.

[0076] At this time, the control unit 7 also measures the top surface height of the wafer 100 through the film 103 using the non-contact top surface height measuring device 90. That is, the control unit 7 starts grinding the film 103 while measuring the top surface height of the wafer 100 through the film 103.

[0077] Then, when the measurement value by the non-contact top surface height measuring device 90 starts to decrease, the control unit 7 determines that the film 103 has been removed from the wafer 100 and the top surface 101 of the wafer 100 has started to be ground, as shown in Figure 3, and ends the grinding.

[0078] In this way, when the non-contact top surface height measuring device 90 is used, grinding of the film 103 is started while measuring the top surface height of the wafer 100 through the film 103, and when the measurement value by the non-contact top surface height measuring device 90 starts to decrease, it is determined that the film 103 has been removed and grinding is stopped. Therefore, even if the thickness of the film 103 is unknown, the film 103 can be satisfactorily removed from the wafer 100 by grinding while preventing the film 103 from remaining on the wafer 100 and preventing the top surface 101 of the wafer 100 from being excessively ground.

[0079] The non-contact top surface height measuring device 90 may be configured to measure the top surface height of the wafer 100 by spectral interference instead of using triangulation. In this case, the non-contact top surface height measuring device 90 is provided with a reference plate 95 that serves as a reference for height measurement, as shown in Fig. 5. The reference plate 95 is made of, for example, glass or quartz.

[0080] In this configuration, a light emitting unit (not shown) of the non-contact top surface height measuring instrument 90 irradiates measurement light toward the reference plate 95. This measurement light is light of a wavelength that is transmitted through the film 103 formed on the top surface 101 of the wafer 100 but is blocked by the wafer 100.

[0081] A portion of the measurement light irradiated toward the reference plate 95, that is, measurement light L3, passes through the reference plate 95 and is irradiated onto the top surface 101 of the wafer 100 through the film 103. Top surface reflected light L4 obtained by the measurement light L3 being reflected by the top surface 101 is received by a light receiving unit (spectroscope) (not shown) of the non-contact top surface height measuring instrument 90. In addition, another part of the measurement light L5 irradiated toward the reference plate 95 is reflected by the reference surface 96 of the reference plate 95, and the reflected light, that is, reference surface reflected light L6, is received by the light receiving unit.

[0082] Thus, in this configuration, the light receiving unit is subjected to reference surface reflected light L6 reflected by the reference surface 96 and top surface reflected light L4 reflected by the top surface 101 of the wafer 100. The amplitude of the interference light between the reference surface reflected light L6 and the top surface reflected light L4 varies depending on the distance from the reference surface 96 to the top surface 101 of the wafer 100. Therefore, the non-contact top surface height measuring device 90 can calculate the distance from the reference surface 96 to the top surface 101 of the wafer 100 by analyzing the interference light between the reference surface reflected light L6 and the top surface reflected light L4, and thereby determine the height of the top surface 101 of the wafer 100.

[0083] In this way, the non-contact top surface height measuring device 90 may be configured to irradiate measurement light having a wavelength that is transparent to the film 103 and a wavelength that is opaque to the wafer 100 from above the wafer 100, receive the top surface reflected light reflected by the top surface 101 of the wafer 100 through the film 103, and measure the top surface height of the wafer 100 by triangulation or spectral interference.

[0084] Furthermore, even when the non-contact top surface height measuring device 90 is used, the control unit 7 may continue to perform height measurements using the height measuring device 81 after starting grinding of the film 103. Then, when the measurement value of the height measuring device 81 has become low enough to determine that the film 103 has been removed, but the measurement value of the top surface height of the wafer 100 measured by the non-contact top surface height measuring device 90 does not start to decrease, the control unit 7 may determine that a malfunction has occurred in the height measuring device 81 or the non-contact top surface height measuring device 90, and may stop grinding.

[0085] In addition, in the above embodiment, the height of the film 103 formed on the upper surface 101 of the wafer 100 is measured using the height measuring device 81, and the lower surface of the grinding wheel 77 is positioned at a height corresponding to the measured height, and grinding of the film 103 is started.

[0086] In this regard, the grinding apparatus 1 does not necessarily have to include the height measuring device 81. In this case, the control unit 7 may, for example, lower the grinding mechanism 70 at a constant grinding speed.

[0087] Furthermore, when the thickness measuring device 82 is used and the measurement light of the thickness measuring device 82 passes through the film 103, the control unit 7 may determine the height of the film 103 from the height of the holding surface 22 on the chuck table 20, the thickness of the wafer 100 measured by the thickness measuring device 82, and the film thickness of the film 103. Furthermore, when the non-contact upper surface height measuring device 90 is used, the control unit 7 may determine the height of the film 103 from the height of the upper surface of the wafer 100 measured by the non-contact upper surface height measuring device 90 and the film thickness of the film 103.

[0088] The control unit 7 may then position the lower surface of the grinding wheel 77 at a height corresponding to the determined height at a relatively high initial speed, and then start grinding at a relatively low grinding speed. In this case, the thickness of the film 103 is not limited to the exact thickness of the film 103, and may be the approximate value described above. In this configuration, the height measuring device 81 is not required, and therefore the cost of the grinding device 1 can be reduced.

[0089] In the grinding device 1, the height of the grinding wheel 77 can be measured using the Z-axis encoder 65 of the grinding mechanism 70 shown in Fig. 1. Therefore, the control unit 7 can obtain the amount of film 103 ground by the grinding wheel 77 based on the amount of change in the height of the grinding wheel 77 from the start of grinding of the film 103.

[0090] However, if the grinding wheel 77 does not correspond to the film 103, the film 103 may not be ground away and only the grinding wheel 77 may be worn away. In this case, even if the film 103 is not ground away, the height of the grinding wheel 77 changes due to the wear of the grinding wheel 77. This makes it difficult for the control unit 7 to obtain the amount of grinding of the film 103 from the height of the grinding wheel 77.

[0091] Therefore, when using the thickness measuring device 82, the control unit 7 may determine that the grinding wheel 77 does not correspond to the film 103 and stop grinding, for example, when the measured value of the height of the grinding wheel 77 obtained by the Z-axis encoder 65 becomes low enough to determine that the film 103 has been removed, but the measured value of the thickness measurement of the wafer 100 by the thickness measuring device 82 does not begin to decrease (when the measurement light of the thickness measuring device 82 passes through the film 103), or when the state in which the thickness measurement of the wafer 100 can be performed by the thickness measuring device 82 does not occur (when the measurement light is blocked by the film 103).

[0092] Similarly, when a non-contact top surface height measuring device 90 is used, if the measured value of the height of the grinding wheel 77 obtained by the Z-axis encoder 65 becomes low enough to determine that the film 103 has been removed, but the measured value of the top surface height of the wafer 100 measured by the non-contact top surface height measuring device 90 does not begin to decrease, the control unit 7 may determine that the grinding wheel 77 is not corresponding to the film 103 and stop grinding. [Explanation of symbols]

[0093] 1: grinding device, 7: control unit, 10: base, 11: column, 12: bellows cover, 13: opening, 20: chuck table, 21: porous member, 22: holding surface, 23: frame body, 24: frame body surface, 30: wafer holding mechanism, 39: cover plate, 40: tilt adjustment mechanism, 41: internal base, 42: tilt adjustment shaft, 43: fixed shaft, 45: annular member, 46: connecting portion, 47: fixed member, 48: driving portion, 50: table rotation mechanism, 55: table base, 60: lifting mechanism, 61: Z-axis guide rail, 62: Z-axis ball screw, 63: Z-axis moving table, 64: Z-axis motor, 65: Z-axis encoder, 66: holder, 70: grinding mechanism, 71: spindle housing, 72: spindle, 73: spindle motor, 74: Wheel mount, 75: Grinding wheel, 76: Wheel base, 77: Grinding stone, 80: Measuring mechanism, 81: Height measuring device, 82: Thickness measuring device, 83: Arm part, 84: Support member, 85: Contactor, 90: Non-contact top surface height measuring device, 91: Light emitting element, 92: Light receiving element, 95: Reference plate, 96: Reference surface, 100: wafer, 101: upper surface, 102: lower surface, 103: film, 221: Rotating shaft, 411: Through hole, 412: Opening, 421: Male screw, 450: through hole, 451: female screw, 502: arrow, 503: arrow, 521: motor, 522: driving pulley, 523: endless belt, 524: driven pulley, 525: rotary joint, 526: fixed member, 721: spindle rotation axis

Claims

1. A wafer reclamation method comprising holding the underside of a wafer having a film on its upper surface by a chuck table of a grinding device, and grinding and removing the film with a grinding wheel of the grinding device to reclaim the wafer, comprising: the grinding apparatus includes a non-contact thickness measuring device that irradiates the wafer from above with measurement light having a wavelength that is transparent to the film and the wafer, receives top-reflected light that is reflected off the top surface of the wafer through the film, and bottom-reflected light that is reflected off the bottom surface of the wafer through the film and the wafer, and measures the thickness of the wafer by spectral interference; grinding the film while measuring the thickness of the wafer through the film using the non-contact thickness gauge, and ending the grinding when the thickness measured by the non-contact thickness gauge begins to decrease; A method for reclamation of wafers.

2. A wafer reclamation method comprising holding the underside of a wafer having a film on its upper surface by a chuck table of a grinding device, and grinding and removing the film with a grinding wheel of the grinding device to reclaim the wafer, comprising: the grinding apparatus includes a non-contact thickness measuring device that irradiates the wafer from above with measurement light having a wavelength that is shielded by the film and is transparent to the wafer, receives upper-surface reflected light that is reflected from the upper surface of the wafer, and lower-surface reflected light that is transmitted through the wafer and reflected from the lower surface of the wafer, and measures the thickness of the wafer by spectral interference; Grinding of the film is started from a state in which the non-contact thickness gauge cannot measure the wafer thickness because the film blocks the measurement light, and grinding is terminated when the non-contact thickness gauge becomes able to measure the wafer thickness. A method for reclamation of wafers.

3. A wafer reclamation method comprising holding the underside of a wafer having a film on its upper surface by a chuck table of a grinding device, and grinding and removing the film with a grinding wheel of the grinding device to reclaim the wafer, comprising: the grinding apparatus includes a non-contact top surface height measuring device that irradiates measurement light having a wavelength that is transparent to the film and a wavelength that is opaque to the wafer from above the wafer, receives top surface reflected light that is reflected by the top surface of the wafer through the film, and measures the top surface height of the wafer by triangulation or spectral interference; starting to grind the film while measuring the top surface height of the wafer through the film using the non-contact top surface height measuring device, and ending the grinding when the measurement value by the non-contact top surface height measuring device begins to decrease; A method for reclamation of wafers.

4. the grinding apparatus includes a height measuring device that measures the height of the film on the wafer held on the chuck table; the height of the film on the wafer is measured by the height measuring device, the lower surface of the grinding wheel is positioned at a height corresponding to the height measured by the height measuring device, and grinding of the film is started; 4. The method for reclamation of a wafer according to claim 1, 2 or 3.

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