Wafer processing method

Abstract

To provide a new wafer processing method for forming a chip of a desired thickness from a wafer.SOLUTION: A wafer processing method includes a groove forming step of forming a groove (cutting groove 141) having a depth 140 which is equal to or more than a thickness 130 of a desired chip 160 from the surface 101 along a planned division line, a separation starting point forming step of positioning a focusing point of a laser beam having a wavelength that is transparent to the wafer 100 from the back surface 104 of the wafer 100 at a depth corresponding to the thickness 130 of the chip 160 to be generated, moving the focusing point and the wafer 100 relative to each other, irradiating with the laser beam, and forming a modified layer 131 and a crack 132 extending from the modified layer 131 to form a separation starting point 135 parallel to the surface 101, and a chip peeling step to peel the chip 160 from the wafer 100 by the separation starting point 135.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a wafer processing method for forming chips from a wafer. [Background technology]

[0002] 2. Description of the Related Art There is known a method of forming chips from a wafer by grinding and cutting the wafer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-218599 A Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, a new method for forming chips of a desired thickness from a wafer has been desired.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a new wafer processing method for forming chips having a desired thickness from a wafer. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a wafer processing method of the present invention is a wafer processing method for forming chips from a wafer having a plurality of planned division lines formed in a first direction and a second direction intersecting the first direction and chip regions partitioned by the planned division lines, the method comprising: a groove forming step of forming grooves from a front surface along the planned division lines to a depth equal to or greater than a desired thickness of the chips; a separation origin forming step of positioning a focal point of a laser beam having a wavelength that is transparent to the wafer from the rear surface of the wafer at a depth corresponding to the thickness of the chip to be generated, and irradiating the wafer with the laser beam while moving the focal point relative to the wafer, to form a modified layer and cracks extending from the modified layer to form separation origins parallel to the front surface; and a chip peeling step of peeling the chips from the wafer by the separation origins. A device is formed in the chip region, and in the chip region where the device is determined to be defective, the groove forming step, the separation starting point forming step, and the chip peeling step are performed to selectively cut out the device determined to be defective, and a device determined to be good is embedded in the chip region from which the device determined to be defective has been cut out. It is characterized by:

[0007] In the separation starting point formation step, the laser beam is positioned and irradiated at a depth corresponding to at least two or more different chip thicknesses for each chip region, in the groove formation step, a groove having a depth equal to or greater than the desired chip thickness is formed in the chip region in which the groove is formed, and in the chip peeling step, chips having at least two or more different thicknesses are formed for each chip region. Effect of the Invention

[0009] The present invention can provide a new wafer processing method for forming chips of a desired thickness from a wafer. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a flowchart showing an example of a processing procedure of the wafer processing method according to the first embodiment. [Diagram 2] FIG. 2 is a perspective view showing an example of a wafer to be processed by the wafer processing method of FIG. [Diagram 3] FIG. 3 is a cross-sectional view illustrating the separation starting point forming step of FIG. [Figure 4]FIG. 4 is a top view illustrating the separation starting point forming step in FIG. [Diagram 5] FIG. 5 is a cross-sectional view illustrating a first example of the groove forming step of FIG. [Figure 6] FIG. 6 is a top view illustrating a first example of the groove forming step of FIG. [Figure 7] FIG. 7 is a cross-sectional view illustrating a second example of the groove forming step of FIG. [Figure 8] FIG. 8 is a cross-sectional view illustrating the chip peeling step of FIG. [Figure 9] FIG. 9 is a cross-sectional view illustrating a first example of a groove forming step in the wafer processing method according to the first modified example. [Figure 10] FIG. 10 is a top view illustrating a first example of a groove forming step in the wafer processing method according to the first modification. [Figure 11] FIG. 11 is a sectional view illustrating a second example of the groove forming step in the wafer processing method according to the first modified example. [Figure 12] FIG. 12 is a cross-sectional view illustrating a separation start point forming step in the wafer processing method according to the first modification. [Figure 13] FIG. 13 is a top view illustrating a separation start point forming step in the wafer processing method according to the first modified example. [Figure 14] FIG. 14 is a cross-sectional view illustrating a separation start point forming step in the wafer processing method according to the second embodiment. [Figure 15] FIG. 15 is a top view illustrating a separation start point forming step in the wafer processing method according to the second embodiment. [Figure 16] FIG. 16 is a cross-sectional view illustrating a first example of a groove forming step in the wafer processing method according to the second embodiment. [Figure 17] FIG. 17 is a top view illustrating a first example of a groove forming step in the wafer processing method according to the second embodiment. [Figure 18] FIG. 18 is a cross-sectional view illustrating a second example of the groove forming step in the wafer processing method according to the second embodiment. [Figure 19]FIG. 19 is a cross-sectional view illustrating a chip peeling step in the wafer processing method according to the second embodiment. [Figure 20] FIG. 20 is a flowchart showing an example of a processing procedure of the wafer processing method according to the third embodiment. [Figure 21] FIG. 21 is a cross-sectional view illustrating the separation start point forming step of FIG. [Figure 22] FIG. 22 is a top view illustrating the separation start point forming step of FIG. [Diagram 23] FIG. 23 is a cross-sectional view illustrating a first example of the groove forming step of FIG. [Figure 24] FIG. 24 is a top view illustrating a first example of the groove forming step of FIG. [Diagram 25] FIG. 25 is a cross-sectional view illustrating a second example of the groove forming step of FIG. [Figure 26] FIG. 26 is a cross-sectional view illustrating the chip peeling step of FIG. [Figure 27] FIG. 27 is a top view illustrating the chip peeling step of FIG. [Figure 28] FIG. 28 is a cross-sectional view illustrating the adhesive filling step of FIG. [Figure 29] FIG. 29 is a top view illustrating the adhesive filling step of FIG. [Diagram 30] FIG. 30 is a cross-sectional view illustrating the chip fixing step of FIG. [Diagram 31] FIG. 31 is a top view illustrating the chip fixing step of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0012] [Embodiment 1] A wafer processing method according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart showing an example of a processing procedure of the wafer processing method according to the first embodiment. FIG. 2 is a perspective view showing an example of a wafer 100 to be processed by the wafer processing method of FIG. 1. FIG. 3 is a cross-sectional view explaining the separation start point forming step 1001 of FIG. 1. FIG. 4 is a top view explaining the separation start point forming step 1001 of FIG. 1. FIG. 4 is a view showing the state of FIG. 3 from the back surface 104 side. FIG. 5 is a cross-sectional view explaining a first example of the groove forming step 1002 of FIG. 1. FIG. 6 is a top view explaining a first example of the groove forming step 1002 of FIG. 1. FIG. 6 is a view showing the state of FIG. 5 from the front surface 101 side. FIG. 7 is a cross-sectional view explaining a second example of the groove forming step 1002 of FIG. 1. FIG. 8 is a cross-sectional view explaining the chip peeling step 1003 of FIG. 1. The wafer processing method according to the first embodiment includes a separation start point forming step 1001, a groove forming step 1002, and a chip peeling step 1003, as shown in FIG.

[0013] The wafer 100 to be processed by the wafer processing method according to the first embodiment is, for example, a disk-shaped semiconductor wafer or an optical device wafer made of silicon, sapphire, silicon carbide (SiC), gallium arsenide, or the like. As shown in FIG. 2, the wafer 100 has a flat surface 101, a plurality of division lines 102 formed along a first direction and a second direction intersecting the first direction, and a chip region 103 partitioned by the plurality of division lines 102. In the wafer 100 according to the first embodiment, a chip 160 (device, see FIG. 8) is formed in each chip region 103. In the wafer 100 according to the first embodiment, the first direction and the second direction are mutually orthogonal, and the plurality of division lines 102 are formed in a lattice pattern, but the present invention is not limited thereto.

[0014] In the first embodiment, the wafer 100 is subjected to processing in each step by attaching an adhesive tape 105 to the front surface 101 or the back surface 104 behind the front surface 101, as shown by the arrows 110 and 120 in FIG. 2, and attaching an annular frame 106 to the outer edge of the adhesive tape 105, as shown by the arrows 110 and 120 in FIG. 2, respectively; however, the present invention is not limited thereto.

[0015] The separation starting point formation step 1001 is a step in which, as shown in FIG. 3, a focal point 13 of a laser beam 12 having a wavelength that is transparent to the wafer 100 is positioned from the back surface 104 of the wafer 100 at a depth corresponding to the thickness 130 of the chip 160 (see FIG. 8) to be generated, and the laser beam 12 is irradiated while moving the focal point 13 and the wafer 100 relatively, to form a modified layer 131 and a crack 132 extending from the modified layer 131 at that depth, as shown in FIG. 3 and FIG. 4, thereby forming a separation starting point 135 parallel to the surface 101.

[0016] In the separation starting point forming step 1001, first, an adhesive tape 105 is attached to the surface 101 of the wafer 100. In the separation starting point forming step 1001, next, as shown in Fig. 3, the surface 101 side of the wafer 100 is held on a holding surface 16 by a holding table 15 of the laser processing device 10 via the adhesive tape 105. Here, in the first embodiment, the holding table 15 includes, for example, a disk-shaped frame body having a recess formed therein, and a disk-shaped suction part formed of a porous ceramic or the like having a large number of porous holes and fitted into the recess, and the upper surface of the suction part is the holding surface 16 that suction-holds the wafer 100 by negative pressure introduced from a suction source (not shown).

[0017] In the separation starting point forming step 1001, next, as shown in Fig. 3, the vertical position of the focal point 13 of the laser beam 12 oscillated by the laser oscillator 11 of the laser processing device 10 is positioned at a position higher by the thickness 130 of the chip 160 (see Fig. 8) than the front surface 101 of the wafer 100, for example, by an elevation movement unit (not shown) that moves the laser oscillator 11 or the holding table 15 up and down along the vertical direction, or a focusing unit (not shown) provided in the laser oscillator 11 that moves the focal position of the laser beam 12 up and down along the vertical direction. Note that in the first embodiment in which the laser beam 12 is irradiated from the back surface 104 of the wafer 100, the position higher by the thickness 130 of the chip 160 than the front surface 101 of the wafer 100 corresponds to a depth equivalent to the thickness 130 of the chip 160.

[0018] 3, for example, a moving unit (not shown) that moves the laser oscillator 11 or the holding table 15 along a direction parallel to the front surface 101 moves the focal point 13 and the wafer 100 relatively along a predetermined direction parallel to the front surface 101 (up and down on the paper surface of FIG. 4), while continuously vertically irradiating the laser beam 12 from the back surface 104 side of the wafer 100 toward the wafer 100, thereby forming a modified layer 131 in a straight line extending in the predetermined direction at a position higher than the front surface 101 of the wafer 100 by the thickness 130 of the chip 160 (see FIG. 8). In the separation starting point forming step 1001, for example, the laser oscillator 11 of the laser processing device 10 irradiates the wafer 100 with a pulsed laser beam 12.

[0019] The modified layer 131 formed in the separation starting point forming step 1001 is a layer in which the base material of the wafer 100 is made amorphous at the focal point 13 of the laser beam 12, and residual stress acts in a direction parallel to the surface 101. In the separation starting point forming step 1001, this residual stress forms a crack 132 extending from the modified layer 131 in a direction intersecting the predetermined direction, as shown in Figures 3 and 4. Both the modified layer 131 and the crack 132 formed in the separation starting point forming step 1001 become separation starting points 135 when a peeling process is performed in the chip peeling step 1003 described later.

[0020] In the separation starting point forming step 1001, as shown in FIG. 4, a plurality of linear modified layers 131 are formed parallel to each other at intervals according to the effective extension length of the crack 132 from the modified layer 131 (at intervals of about twice the effective extension length (1.9 times or more and 2.1 times or less) in the first embodiment), and the separation starting points 135 parallel to the surface 101 are formed sufficiently uniformly so as not to cause large intervals or uneven weighting. In the separation starting point forming step 1001, in the first embodiment, for example, the modified layers 131 are formed at intervals of about 10 μm, and the effective extension length of the crack 132 from the modified layer 131 is about 5 μm. Here, the effective extension length of the crack 132 from the modified layer 131 refers to the length of the crack 132 from the modified layer 131 that functions sufficiently effectively as the separation starting point 135. In the separation starting point forming step 1001, in the first embodiment, the laser beam 12 is irradiated over the entire surface of the wafer 100 in the direction of the arrows shown in Figures 3 and 4 to form the modified layer 131 and the cracks 132, but the present invention is not limited to this, and the modified layer 131 and the cracks 132 may be formed only in the region corresponding to the chip region 103. Note that, in reality, a plurality of modified layers 131 are further formed in the separation starting point forming step 1001, but these are omitted in Figures 4 and 6, and only some of the modified layers 131 are shown.

[0021] The groove forming step 1002 is a step of forming grooves along the intended dividing lines 102 to a depth equal to or greater than the thickness 130 of a desired chip 160 (see FIG. 8) from the front surface 101. The groove forming step 1002 is a so-called half cut in which grooves are formed to a depth equal to or less than the thickness of the wafer 100.

[0022] In the groove forming step 1002, first, the adhesive tape 105 attached to the front surface 101 of the wafer 100 after the processing in the separation starting point forming step 1001 is peeled off, and the adhesive tape 105 is attached to the back surface 104 of the wafer 100. In the groove forming step 1002, next, in the first example, as shown in Fig. 5, the back surface 104 side of the wafer 100 is held on the holding surface 26 by the holding table 25 of the cutting device 20 via the adhesive tape 105, and in the second example, as shown in Fig. 7, the back surface 104 side of the wafer 100 is held on the holding surface 36 by the holding table 35 of the laser processing device 30 via the adhesive tape 105. Both of the holding tables 25 and 35 have the same structure as the holding table 15.

[0023] 5, the cutting blade 21 of the cutting device 20 is rotated to cut into the wafer 100 from the surface 101 to a depth 140 equal to or greater than the thickness 130, and the cutting blade 21 and the wafer 100 are moved relatively along the dividing lines 102 by a moving unit (not shown) that moves the cutting blade 21 or the holding table 25 in a direction parallel to the surface 101, for example, to cut the wafer 100, thereby forming cutting grooves 141 of a depth 140 along the dividing lines 102. In the first example of the groove forming step 1002, cutting is performed for each dividing line 102, and cutting grooves 141 of a depth 140 are formed along all dividing lines 102, as shown in FIG. In reality, the modified layers 131 formed in the separation starting point forming step 1001 are formed more densely than the cut grooves 141 formed in the first example of the groove forming step 1002, as shown in Figure 6.

[0024] 7, while irradiating the wafer 100 with a laser beam 32 having a wavelength absorbed by the wafer 100 by the laser oscillator 31 of the laser processing device 30, the laser beam 32 and the wafer 100 are moved relatively along the dividing lines 102 by, for example, a moving unit (not shown) that moves the laser oscillator 31 or the holding table 35 along a direction parallel to the surface 101, to sublimate or evaporate the wafer 100 by the laser beam 32, so-called ablation processing is performed, thereby forming a laser processed groove 151 having a depth 150 and a thickness 130 or more along the dividing lines 102. In the second example of the groove forming step 1002, for example, the pulsed laser beam 32 is irradiated to the wafer 100 by the laser oscillator 31 of the laser processing device 30. In the second example of the groove forming step 1002 , similarly to the first example of the groove forming step 1002 , laser processed grooves 151 having a depth 150 are formed along all of the intended division lines 102 .

[0025] 8, the chip peeling step 1003 is a step of peeling the chip 160 from the wafer 100 by the separation origin 135 formed in the separation origin forming step 1001. In the example shown in Fig. 8, the chip peeling step 1003 is performed after the first example of the groove forming step 1002, but the same applies to the case where it is performed after the second example of the groove forming step 1002.

[0026] 8, in the chip peeling step 1003, the back surface 104 side of the wafer 100 is held on the holding surface 46 by the holding table 45 of the chip peeling device 40 via an adhesive tape 105. The holding table 45 has a structure similar to that of the holding table 15.

[0027] In the chip peeling step 1003, next, an adhesive piece 43 attached to the lower end of an ultrasonic horn 41 of a chip peeling device 40 is brought into contact with the surface 101 side of the chip region 103 of the wafer 100, and then ultrasonic oscillator 42 applies ultrasonic waves to the ultrasonic horn 41 to cause ultrasonic vibration. The ultrasonically vibrated ultrasonic horn 41 then applies ultrasonic vibration to the chip region 103 of the wafer 100 via the adhesive piece 43, thereby destroying the separation starting point 135 of the chip region 103, and peeling off the chip 160 formed in the chip region 103 from the wafer 100.

[0028] In the chip peeling step 1003, the chip 160 peeled off from the wafer 100 is sucked and held from above by the suction piece 43 and picked up to obtain the individual chip 160. Here, in the first embodiment, for example, a negative pressure is introduced from a suction source (not shown) to the lower surface of the suction piece 43, and the chip 160 is sucked and held from above by the negative pressure. In the chip peeling step 1003, in the first embodiment, the chip 160 is peeled off and picked up for each chip region 103, and all the chips 160 formed on the wafer 100 are obtained as individual chips. Note that in the chip peeling step 1003, if the chip 160 can be peeled off only by suction with the suction piece 43, the chip peeling step 1003 may be performed by a chip peeling device 40 that does not include an ultrasonic oscillator 42.

[0029] In the wafer processing method according to the first embodiment having the above-mentioned configuration, in a separation origin forming step 1001, the focal point 13 of the laser beam 12 having a wavelength that is transparent to the wafer 100 is positioned at a depth corresponding to the desired thickness 130 of the chip 160 along the bottom surface of the chip 160, and the laser beam 12 is irradiated to form a separation origin 135, in a groove forming step 1002, a groove (cut groove 141 in the first example, laser processed groove 151 in the second example) is formed along the intended division line 102, and in a chip peeling step 1003, the chip 160 is peeled off from the wafer 100 starting from the separation origin 135. Therefore, the wafer processing method according to the first embodiment has an effect of being able to form a chip 160 having a desired thickness 130 from the wafer 100 by changing the height at which the focal point 13 of the laser beam 12 having a wavelength that is transparent to the wafer 100 is positioned. Furthermore, the wafer processing method according to embodiment 1 forms a separation layer over the entire bottom surface of the chip 160, in which separation starting points 135 each consisting of a modified layer 131 and a crack 132 extending from the modified layer 131 are connected in a planar direction parallel to the surface 101 of the wafer 100, so that the chip 160 can be peeled off smoothly.

[0030] Moreover, in the wafer processing method according to the embodiment 1, in the separation origin forming step 1001, a laser beam 12 having a wavelength that is transparent to the wafer 100 is irradiated from the back surface 104 side, which is the opposite side to the front surface 101 on which the chips 160 of the wafer 100 are formed, to form the separation origins 135. Therefore, in the wafer processing method according to the embodiment 1, when a device (chip 160) is formed on the front surface 101, the laser beam 12 is not obstructed and the separation origins 135 can be formed satisfactorily. In addition, in the wafer processing method according to the embodiment 1, when a device (chip 160) is formed on the front surface 101, the effect of damage to the chip 160 from the laser beam 12 irradiated for forming the separation origins 135 can be reduced.

[0031] Moreover, the wafer processing method according to the first embodiment can form chips 160 of a desired thickness without using a grinding device. Furthermore, in the wafer processing method according to the first embodiment, when the groove forming step 1002 is performed by the laser processing device 30, the chips 161 of a desired thickness can be formed only by the laser processing devices 10 and 30, and by using the same laser processing devices 10 and 30, the installation area of ​​the device can be reduced and the production costs can be reduced. Furthermore, in the conventional method, a step of reducing the adhesive strength of the adhesive tape is required when peeling off the chips, but in the wafer processing method according to the first embodiment, the chips 160 are peeled off from the separation origin 135 formed inside the wafer 100, so that the step of reducing the adhesive strength of the adhesive tape 105 is not required. Furthermore, in the wafer processing method according to embodiment 1, after irradiating laser beam 12 from the back surface 104 side of wafer 100 in separation starting point formation step 1001, groove formation step 1002 and chip peeling step 1003 are successively performed from the front surface 101 side of wafer 100. Therefore, whereas the adhesive tape 105 needs to be replaced twice in variant example 1 described below, the adhesive tape 105 needs to be replaced only once after separation starting point formation step 1001, thereby reducing the number of steps.

[0032] [Variation 1] A wafer processing method according to the first modified example of the present invention will be described with reference to the drawings. FIG. 9 is a cross-sectional view for explaining a first example of the groove forming step 1002 of the wafer processing method according to the first modified example. FIG. 10 is a top view for explaining a first example of the groove forming step 1002 of the wafer processing method according to the first modified example. FIG. 10 is a view of the state of FIG. 9 seen from the front surface 101 side. FIG. 11 is a cross-sectional view for explaining a second example of the groove forming step 1002 of the wafer processing method according to the first modified example. FIG. 12 is a cross-sectional view for explaining the separation start point forming step 1001 of the wafer processing method according to the first modified example. FIG. 13 is a top view for explaining the separation start point forming step 1001 of the wafer processing method according to the first modified example. FIG. 13 is a view of the state of FIG. 12 seen from the back surface 104 side. In FIG. 9 to FIG. 13, the same parts as those in the first embodiment are given the same reference numerals, and the description will be omitted.

[0033] The wafer processing method according to Modification 1 is the same as that according to Embodiment 1 except that the order of performing separation start point forming step 1001 and groove forming step 1002 is reversed, and other processing is the same as that according to Embodiment 1. That is, in the wafer processing method according to Modification 1, groove forming step 1002 is performed before separation start point forming step 1001.

[0034] The groove forming step 1002 in variant example 1 is the same as that in embodiment 1, except that an adhesive tape 105 is first attached to the back surface 104 of the wafer 100, and a groove (a cut groove 141 in the first example, and a laser-machined groove 151 in the second example) is formed in the wafer 100 where the separation starting point 135 is not formed, as shown in Figures 9 and 10 in the first example, and as shown in Figure 11 in the second example.

[0035] The separation start point forming step 1001 of the wafer processing method according to the modified example 1 is the same as that of the embodiment 1, except that the adhesive tape 105 attached to the back surface 104 of the wafer 100 after the processing of the groove forming step 1002 is peeled off and the adhesive tape 105 is attached to the front surface 101 of the wafer 100, and that the separation start point 135 is formed on the wafer 100 on which a groove (a cut groove 141 in the first example and a laser processed groove 151 in the second example) is formed, as shown in Fig. 12 and Fig. 13. The examples shown in Fig. 12 and Fig. 13 show the separation start point forming step 1001 performed after the first example of the groove forming step 1002, but the same applies to the case where the separation start point forming step 1001 is performed after the second example of the groove forming step 1002.

[0036] The chip peeling step 1003 of the wafer processing method according to the modified example 1 is the same as that of the embodiment 1, except that it is performed after peeling off the adhesive tape 105 attached to the front surface 101 of the wafer 100 after the processing of the separation starting point formation step 1001, and attaching the adhesive tape 105 to the back surface 104 of the wafer 100.

[0037] The wafer processing method of variant example 1 having the above-described configuration reverses the order of steps 1001 and 1002 of forming separation start points in embodiment 1, and therefore has the same effect as embodiment 1.

[0038] [Embodiment 2] A wafer processing method according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 14 is a cross-sectional view for explaining the separation start point forming step 1001 of the wafer processing method according to the second embodiment. FIG. 15 is a top view for explaining the separation start point forming step 1001 of the wafer processing method according to the second embodiment. FIG. 15 is a view of the state of FIG. 14 seen from the back surface 104 side. FIG. 16 is a cross-sectional view for explaining a first example of the groove forming step 1002 of the wafer processing method according to the second embodiment. FIG. 17 is a top view for explaining a first example of the groove forming step 1002 of the wafer processing method according to the second embodiment. FIG. 17 is a view of the state of FIG. 16 seen from the front surface 101 side. FIG. 18 is a cross-sectional view for explaining a second example of the groove forming step 1002 of the wafer processing method according to the second embodiment. FIG. 19 is a cross-sectional view for explaining the chip peeling step 1003 of the wafer processing method according to the second embodiment. In FIGS. 14 to 19, the same reference numerals are assigned to the same parts as those in the first embodiment, and the description thereof will be omitted.

[0039] 19, the wafer processing method according to the second embodiment is a modification of the first embodiment in that chips 160-1 having a thickness 130-1 are generated from a half region 170 on one side of the wafer 100, and chips 160-2 having a thickness 130-2 are generated from a half region 180 on the other side of the wafer 100, and other processing is similar to that of the first embodiment. In the second embodiment, the thicknesses 130-1 and 130-2 are different from each other.

[0040] The separation starting point forming step 1001 of the wafer processing method according to the second embodiment is the same as that of the first embodiment, except that the depth at which the focal point 13 of the laser beam 12 is positioned is changed for each of the regions 170, 180 of the wafer 100, thereby changing the depth at which the separation starting point 135 is formed; the other processing steps are the same as those of the first embodiment. Specifically, in the separation starting point formation step 1001 of the wafer processing method of embodiment 2, as shown in Figures 14 and 15, in region 170, the focal point 13 of the laser beam 12 is positioned at a depth corresponding to the thickness 130-1 of the chip 160-1 to be generated (see Figure 19), and the laser beam 12 is irradiated to form a modified layer 131 and a crack 132 at that depth to form a separation starting point 135, and in region 180, the focal point 13 of the laser beam 12 is positioned at a depth corresponding to the thickness 130-2 of the chip 160-2 to be generated (see Figure 19), and the laser beam 12 is irradiated to form a modified layer 131 and a crack 132 at that depth to form a separation starting point 135.

[0041] The groove forming step 1002 of the wafer processing method of embodiment 2 is a modification of embodiment 1, modified so as to form a groove (cut groove 141 in the first example, laser-machined groove 151 in the second example) having a depth (depth 140 in the first example, depth 150 in the second example) greater than or equal to thickness 130-1 of the thicker of the desired chips 160-1, 160-2 (see FIG. 19) (chip 160-1 in the examples shown in FIG. 16 and FIG. 18) from the surface 101, as shown in FIG. 16 and FIG. 17 in the first example, and as shown in FIG. 18 in the second example, and the other processing is the same as that of embodiment 1.

[0042] In the groove forming step 1002 of the wafer processing method according to the second embodiment, the groove (cut groove 141 in the first example, laser processed groove 151 in the second example) surrounding the chip region 103 may be formed to a depth (depth 140 in the first example, depth 150 in the second example) greater than the thickness (thickness 130-1, 130-2) of the chip (chip 160-1, 160-2) desired in the chip region 103. In the groove forming step 1002 of the wafer processing method according to the second embodiment, the depth (depth 140 in the first example, depth 150 in the second example) of the groove (cut groove 141 in the first example, laser processed groove 151 in the second example) may be changed for each division line 102 according to the thickness (thickness 130-1, 130-2) of the chip (chip 160-1, 160-2) desired in the chip region 103 adjacent to the division line 102.

[0043] As shown in FIG. 19, chip peeling step 1003 of the wafer processing method of embodiment 2 is a modification of embodiment 1 in which chip 160-1 with thickness 130-1 is peeled and picked up in region 170, and chip 160-2 with thickness 130-2 is peeled and picked up in region 180; the other processes are the same as those of embodiment 1.

[0044] In the second embodiment, chips 160-1, 160-2 having two different thicknesses 130-1, 130-2 are generated for each of the two regions 170, 180 of the wafer 100, but the present invention is not limited to this, and may have three or more types, or may have any form in which chips having at least two different thicknesses are generated for each chip region 103 of the wafer 100. In this case, in the separation start point forming step 1001, the focus point 13 of the laser beam 12 is positioned at a depth corresponding to the thickness of at least two different chips for each chip region 103 of the wafer 100, and the laser beam 12 is irradiated to form the separation start point 135, and in the groove forming step 1002, a groove surrounding the chip region 103 is formed to a depth equal to or greater than the desired chip thickness for each chip region 103.

[0045] Conventionally, when chips of different thicknesses are formed from one wafer, an inefficient method of changing the grinding thickness for each individual chip is used. However, the wafer processing method according to the second embodiment having the above configuration can form chips 160-1, 160-2 of two or more different thicknesses 130-1, 130-2 (two types in the examples of Figs. 14 to 19) by changing the depth at which the separation starting point 135 is formed for each chip region 103. Therefore, the wafer processing method according to the second embodiment has an effect of forming chips 160-1, 160-2 of different thicknesses 130-1, 130-2 from one wafer 100 more efficiently than conventional methods.

[0046] In addition, in the wafer processing method according to the second embodiment, the order of the separation start point forming step 1001 and the groove forming step 1002 may be reversed by applying the first modification.

[0047] [Embodiment 3] A wafer processing method according to the third embodiment of the present invention will be described with reference to the drawings. FIG. 20 is a flow chart showing an example of a processing procedure of the wafer processing method according to the third embodiment. FIG. 21 is a cross-sectional view explaining the separation start point forming step 1001 in FIG. 20. FIG. 22 is a top view explaining the separation start point forming step 1001 in FIG. 20. FIG. 22 is a view of the state of FIG. 21 seen from the back surface 104 side. FIG. 23 is a cross-sectional view explaining a first example of the groove forming step 1002 in FIG. 20. FIG. 24 is a top view explaining a first example of the groove forming step 1002 in FIG. 20. FIG. 24 is a view of the state of FIG. 23 seen from the front surface 101 side. FIG. 25 is a cross-sectional view explaining a second example of the groove forming step 1002 in FIG. 20. FIG. 26 is a cross-sectional view explaining the chip peeling step 1003 in FIG. 20. FIG. 27 is a top view explaining the chip peeling step 1003 in FIG. 20. FIG. 27 is a view of the state of FIG. 26 seen from the front surface 101 side. Fig. 28 is a cross-sectional view illustrating adhesive filling step 1004 in Fig. 20. Fig. 29 is a top view illustrating adhesive filling step 1004 in Fig. 20. Fig. 29 is a view of the state of Fig. 28 viewed from the front surface 101 side. Fig. 30 is a cross-sectional view illustrating chip fixing step 1005 in Fig. 20. Fig. 31 is a top view illustrating chip fixing step 1005 in Fig. 20. Fig. 31 is a view of the state of Fig. 30 viewed from the front surface 101 side. In Figs. 20 to 31, the same parts as those in embodiments 1 and 2 are designated by the same reference numerals, and description thereof will be omitted.

[0048] As shown in FIG. 20, the wafer processing method according to the third embodiment includes a device determination step 1011, a separation start point formation step 1001, a groove formation step 1002, a chip peeling step 1003, an adhesive filling step 1004, and a chip fixing step 1005.

[0049] The device determination step 1011 is a step of detecting whether or not each of the chips 160 formed on the wafer 100 is defective. Here, the chips 160 being defective means that the chips 160 do not meet the quality requirements for use as products. In the device determination step 1011, for example, a plurality of probe needles of a device detector (prober) (not shown) are brought into contact with electrodes formed on the chips 160, a predetermined electric signal is input to the chips 160 through the probe needles by a tester (not shown) electrically connected to the probe needles, and whether or not the chips 160 are defective is detected based on the electric signal returned from the chips 160. In the device determination step 1011, the present invention is not limited to this, and various other well-known inspections for detecting whether or not the chips 160 are defective may be performed.

[0050] In the wafer processing method according to the third embodiment, when all the chips 160 are judged to be not defective in the device judgment step 1011 (No in the device judgment step 1011), the processing is terminated. In the wafer processing method according to the third embodiment, when at least one chip 160 is judged to be defective in the device judgment step 1011 (Yes in the device judgment step 1011), information on the position of the chip 160 judged to be defective in the wafer 100, the size and thickness 130 of the chip region 103, etc. are transmitted to a control unit (not shown) that controls each device (laser processing device 10, cutting processing device 20, laser processing device 30, and chip peeling device 40) that performs each step of the wafer processing method according to the third embodiment, and the processing proceeds to a separation start point formation step 1001.

[0051] In the third embodiment, the control unit includes a computer system. The computer system included in the control unit includes an arithmetic processing device having a microprocessor such as a CPU (Central Processing Unit), a storage device having a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and an input / output interface device. The arithmetic processing device of the control unit performs arithmetic processing according to a computer program stored in the storage device of the control unit, and outputs control signals for controlling each of the above devices to each component of each of the above devices via the input / output interface device of the control unit.

[0052] As shown in Figures 21 and 22, the separation starting point formation step 1001 of the wafer processing method of embodiment 3 is modified in embodiment 1 so that a separation starting point 135 is formed at a depth equivalent to the thickness 130 of a chip 160 determined to be defective in the device determination step 1011 only in the chip region 103 in which the chip 160 is formed; the other processing steps are the same as those of embodiment 1.

[0053] The groove forming step 1002 of the wafer processing method of embodiment 3 is modified in such a way that a groove (cut groove 141 in the first example, and laser-machined groove 151 in the second example) having a depth greater than or equal to the thickness 130 of the chip 160 (depth 140 in the first example, and depth 150 in the second example) is formed only in the portion of the planned division line 102 surrounding the chip region 103 in which the chip 160 determined to be defective in the device determination step 1011 is formed, as shown in Figures 23 and 24 in the first example, and in Figure 25 in the second example, and the other processing is the same as in embodiment 1.

[0054] In addition, in a first example of the groove forming step 1002 of the wafer processing method according to embodiment 3, specifically, for each portion of the planned dividing line 102, the cutting blade 21 is positioned over that portion of the planned dividing line 102, and while rotating the cutting blade 21, it is lowered vertically to a height at which a cutting groove 141 of depth 140 is formed to perform cutting processing, and then the cutting blade 21 is raised vertically and withdrawn, thus performing a so-called chopper cut. However, the present invention is not limited to chopper cut, and the cutting groove 141 of depth 140 may be formed along the planned dividing line 102 surrounding the chip region 103 in a manner similar to embodiment 1.

[0055] 26 and 27, the chip peeling step 1003 of the wafer processing method according to the third embodiment is a modification of the first embodiment in which only the chips 160 determined to be defective in the device determination step 1011 are peeled off and picked up, and other processing is the same as that of the first embodiment. In the chip peeling step 1003 of the wafer processing method according to the third embodiment, the chips 160 determined to be defective in the device determination step 1011 are picked up, thereby forming recesses 162 having a depth corresponding to the thickness 130 of the chips 160 in an area including the chip region 103 of the wafer 100 in which the chips 160 were formed and the planned division lines 102 surrounding the chip region 103.

[0056] Conventionally, when a chip was completely cut in the thickness direction and peeled off, a procedure was required in which the adhesive strength of the adhesive tape was reduced only in the chip area to be peeled off and then the chip was peeled off. However, in the chip peeling step 1003 of embodiment 3, peeling begins at the separation starting point 135 formed inside the wafer 100, so that the step of reducing the adhesive strength of the adhesive tape 105 only in the chip area 103 where the chip 160 to be peeled off is formed is not required.

[0057] 28 and 29, adhesive filling step 1004 is a step in which adhesive supply device 50 supplies and fills adhesive 53 into recess 162 formed in chip peeling step 1003. In the third embodiment, adhesive 53 is a liquid resin that solidifies in air and is used to fix chip 165 (see FIGS. 30 and 31) that will be supplied later in chip fixing step 1005, and for example, an adhesive containing a well-known organic solvent, surfactant, or the like is preferably used.

[0058] 28, in adhesive filling step 1004, the back surface 104 side of the wafer 100, on which the recesses 162 are formed, is held by holding table 55 of adhesive supply device 50 via adhesive tape 105 on holding surface 56. Holding table 55 has a structure similar to that of holding table 15 of embodiment 1. In adhesive filling step 1004, next, adhesive 53 supplied from adhesive supply source 52 of adhesive supply device 50 is supplied from nozzle 51 to recess 162, and is filled to a depth just sufficient to prevent the recess 162 from overflowing when chip 165 is subsequently supplied in chip fixing step 1005.

[0059] 30 and 31, the chip fixing step 1005 is a step in which the chip fixing device 60 supplies the chip 165 onto the adhesive 53 filled in the recess 162 in the adhesive filling step 1004, and presses and fixes the chip 165 against the adhesive 53. In the third embodiment, the chip 165 has the same specifications, shape and size as the chip 160 peeled off from the wafer 100 in the chip peeling step 1003, and is determined to be non-defective (good) by the same determination method as in the device determination step 1011.

[0060] 30, in the chip fixing step 1005, the back surface 104 side of the wafer 100, in which the adhesive 53 has been filled in the recess 162, is held by the holding surface 66 via the adhesive tape 105 by the holding table 65 of the chip fixing device 60. The holding table 65 has a structure similar to that of the holding table 15 of the first embodiment. In the chip fixing step 1005, next, the suction part 61 of the chip fixing device 60, which has suction-held the chip 165, is positioned on the adhesive 53 in the recess 162, and the suction part 61 presses the chip 165 against the adhesive 53 to a height where the upper surface of the chip 165 is flush with the front surface 101 of the wafer 100, and then the suction-holding of the chip 165 is released.

[0061] In the chip fixing step 1005, the height of the upper surface of the chip 165 based on the bottom surface of the recess 162 is equal to the thickness of the chip 165 plus the thickness of the adhesive 53, so that the separation starting point 135 may be formed to a depth deeper than the thickness 130 of the chip 160 in the separation starting point forming step 1001 performed before the chip fixing step 1005. After the chip fixing step 1005, a step of holding the front surface 101 of the wafer 100 on an adhesive tape 105 and grinding the back surface 104 side may be provided.

[0062] In the example of the wafer processing method according to embodiment 3 shown in Figures 21 to 31, one chip 160 is judged to be defective, and the processing of each step from separation starting point formation step 1001 onwards is carried out in the chip area 103 in which this single chip 160 judged to be defective is formed; however, the present invention is not limited to this, and multiple chips 160 may be judged to be defective, and the processing of each step from separation starting point formation step 1001 onwards may be carried out for each chip area 103 in which these multiple chips 160 judged to be defective are formed.

[0063] Conventionally, when a stacking process (Wafer On Wafer, WOW) is performed in which a plurality of semiconductor device wafers are stacked, a through electrode is formed through the stacked semiconductor device wafers to connect the wafers, and then the stacked wafers are divided to form stacked chips, if a wafer has a defective chip, the chip stacked on the defective chip also becomes unusable. However, the wafer processing method according to the third embodiment having the above configuration selectively cuts out the chip 160 (device) determined to be defective and embeds the chip 165 determined to be good in place of the cut-out chip region 103, so that the chips 160, 165 formed in all chip regions 103 on the wafer 100 can be determined to be good, thereby suppressing the occurrence of chips 160 that cannot be used when the WOW process is performed.

[0064] In the wafer processing method according to the third embodiment, the order of the separation start point forming step 1001 and the groove forming step 1002 may be reversed by applying the first modification.

[0065] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. [Explanation of symbols]

[0066] 12 Laser Beam 13 Focus point 100 wafers 101 Surface 102 Division line 103 Chip Area 104 Back side 130,130-1,130-2 Thickness 131 Modified layer 132 Crack 135 Separation starting point 140,150 Depth 141 Cutting groove 151 Laser-machined groove 160,160-1,160-2,165 chips

Claims

1. A wafer processing method for forming chips from a wafer having a plurality of dividing lines formed in a first direction and a second direction intersecting the first direction, and chip areas partitioned by the dividing lines, comprising: a groove forming step of forming a groove from the surface along the intended dividing line to a depth equal to or greater than the desired thickness of the chip; a separation origin forming step of positioning a focal point of a laser beam having a wavelength that is transparent to the wafer from the back surface of the wafer at a depth corresponding to the thickness of the chip to be generated, irradiating the wafer with the laser beam while moving the focal point and the wafer relatively to each other, forming a modified layer and a crack extending from the modified layer to form a separation origin parallel to the surface; a chip peeling step of peeling the chip from the wafer by the separation starting points; Equipped with A device is formed in the chip region, In the chip region where the device is determined to be defective, the groove forming step, the separation start point forming step, and the chip peeling step are performed to selectively hollow out the device determined to be defective; A wafer processing method comprising the steps of: embedding a device determined to be good in place of a chip area where a device determined to be bad has been hollowed out.

2. In the separation starting point forming step, the laser beam is irradiated to each of the chip regions at a depth corresponding to at least two or more different chip thicknesses; In the groove forming step, a groove is formed having a depth equal to or greater than a desired chip thickness in the chip region where the groove is to be formed, 2. The wafer processing method according to claim 1, wherein in said chip peeling step, chips having at least two different thicknesses are formed for each chip region.

Images