Wafer manufacturing method

Abstract

To provide a method of manufacturing a wafer by which the wafer is excellently peeled from a workpiece by ultrasonic waves even when the workpiece is thin.SOLUTION: The method of manufacturing the wafer W includes the peeling start point forming step S2 of forming the peeling start point 15 including the modified regions 16 and the cracks extending from the modified regions 16 by applying the laser beam from the 11a portion of the front side 11a of the single-crystal SiC ingot 11 in the condition where the focal point of the laser beam is set at a position deeper than the 11a portion of the front side 11a of the single-crystal SiC ingot 11, and the peeling step S3 of peeling the wafer W from the peeling start point 15 by applying the ultrasonic waves to the 11a portion of the front side 11a of the single-crystal SiC ingot 11. 11a. In the peeling step S3, the substrate 7 is attached to the 11b of the back side 11b of the single-crystal SiC ingot 11.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Patent Document 1 describes a method for producing wafers of semiconductors or the like, in which a laser beam with a transparent wavelength is focused and irradiated onto the surface side of a hexagonal single crystal ingot to form a modified layer inside the ingot and separation starting points consisting of cracks extending from the modified layer, and then a plate-like object is peeled off from the ingot to produce wafers.

[0003] Furthermore, Patent Document 2 describes a method for producing wafers by immersing a hexagonal single crystal ingot, on which separation starting points have been formed, in water and applying ultrasonic waves to the ingot to separate a plate-like object from the ingot. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-111143 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-146446 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 2, as the ingot becomes thinner, it becomes more difficult to separate the wafer from the ingot using ultrasonic waves, which causes a problem of reduced wafer manufacturing efficiency.

[0006] The present invention provides a wafer manufacturing method in which the wafer can be successfully separated from a workpiece by ultrasonic waves even when the workpiece is thin. [Means for solving the problem]

[0007] The present invention provides A wafer manufacturing method for manufacturing a wafer from a workpiece having a first surface and a second surface opposite to the first surface, comprising: a delamination initiation forming step of forming a delamination initiation including a modified region and a crack extending from the modified region by irradiating the workpiece with a laser beam having a wavelength that is transparent to the workpiece from the first surface, with the focused point of the laser beam positioned deeper than the first surface of the workpiece; a peeling step of peeling a plate-like object including the first surface of the workpiece as the wafer from the peeling starting point by applying ultrasonic waves to the first surface of the workpiece, The workpiece in the peeling step has a substrate attached to the second surface. [Effects of the Invention]

[0008] According to the present invention, even when the workpiece is thin, the wafer can be effectively separated from the workpiece by ultrasonic waves, resulting in improved wafer manufacturing efficiency. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view showing a laser processing device 1. [Figure 2] 2 is a diagram illustrating a laser beam irradiation mechanism 8 of the laser processing device 1. FIG. [Figure 3] 10 is a diagram showing a state in which a laser beam is irradiated from a surface 11a of an ingot 11 by a condenser 84. FIG. [Figure 4] 10 is a diagram illustrating a laser beam irradiation mechanism 8 according to a modified example. FIG. [Figure 5] 1 is a schematic side view of a peeling device 9, showing a state in which an ultrasonic wave is applied to an ingot 11 by an ultrasonic oscillation unit 91. FIG. [Figure 6] 1 is a schematic side view of the delamination apparatus 9, showing a state in which a wafer W is delaminate|separated from an ingot 11 by a delamination unit 96. FIG. [Figure 7]FIG. 1 is a flow diagram of an embodiment of a method for manufacturing a wafer. [Figure 8] FIG. 10 is a diagram showing a modified example of the peeling device 9. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the wafer manufacturing method of the present invention will be described below with reference to the accompanying drawings. First, a laser processing device 1 and a peeling device 9 used in the wafer manufacturing method will be described.

[0011] (Laser processing equipment) 1 is a perspective view showing a laser processing apparatus 1. In the following description, the X-axis direction is one direction on a horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction on a horizontal plane. The Z-axis direction is a direction perpendicular to the X-axis and Y-axis directions.

[0012] The laser processing apparatus 1 of this embodiment comprises a base 2, a first slide block 4 mounted on the base 2 so as to be movable in the Y-axis direction, a second slide block 6 mounted above the first slide block 4 so as to be movable in the X-axis direction, a holding table 10 provided on the second slide block 6, a column 12 erected on the base 2, a laser beam irradiation mechanism 8 attached to the column 12, and a control unit 14 for controlling the laser processing apparatus 1.

[0013] The first slide block 4 is configured to be movable in the indexing direction, that is, the Y-axis direction, along a pair of guide rails 48 by an indexing mechanism 46 configured of a ball screw 42 and a pulse motor 44 .

[0014] A second slide block 6 is mounted above the first slide block 4 so as to be movable in the X-axis direction. That is, the second slide block 6 is configured so as to be movable in the processing feed direction, i.e., in the X-axis direction, along a pair of guide rails 68 by a processing feed mechanism 66 composed of a ball screw 62 and a pulse motor 64.

[0015] A holding table 10 is mounted on the second slide block 6. The holding table 10 is movable in the X-axis direction and the Y-axis direction by a processing feed mechanism 66 and an indexing feed mechanism 46, and is rotatable by a motor housed in the second slide block 6.

[0016] A column 12 is erected on the base 2, and a laser beam irradiation mechanism 8 is attached to this column 12.

[0017] Figure 2 is a diagram illustrating the laser beam irradiation mechanism 8 of the laser processing device 1. As shown in Figures 1 and 2, the laser beam irradiation mechanism 8 is composed of a laser beam generating unit 82 housed in a casing 13, and a condenser (laser head) 84 attached to the tip of the casing 13. An imaging unit 86 having a microscope and a camera is attached to the tip of the casing 13 adjacent to the condenser 84.

[0018] The laser beam generating unit 82 includes a laser oscillator 80 that oscillates a YAG laser or a YVO4 laser, and an output adjustment unit 81. Although not specifically shown, the laser oscillator 80 has a Brewster window, and the laser beam emitted from the laser oscillator 80 is a linearly polarized laser beam.

[0019] The pulsed laser beam, adjusted to a predetermined power by the output adjustment unit 81 of the laser beam generating unit 82, is reflected by the mirror 87 of the collector 84 and then irradiated by the collector lens 88, with the focal point positioned inside the ingot 11, which is an example of a workpiece fixed on the holding table 10.

[0020] The material of the ingot 11 is not particularly limited, and may be, for example, a SiC single crystal ingot or a GaN single crystal ingot. The ingot 11 is not limited to a single crystal ingot, but may also be a polycrystalline ingot. The ingot 11 has a front surface 11a and a back surface 11b opposite to the front surface 11a. The front surface 11a of the ingot 11 is polished to a mirror finish as it is the surface to be irradiated with the laser beam. The thickness of the ingot 11 is, for example, 0.35 mm to 100 mm. In this embodiment, a substrate 7 is attached to the back surface 11b of the ingot 11, as will be described in detail later.

[0021] The control unit 14 controls each of the above-mentioned components of the laser processing apparatus 1, causing the laser processing apparatus 1 to perform various processes on the workpiece. The control unit 14 is a computer including a control unit that performs various calculations, a memory unit having a storage medium, and an input / output interface (not shown) that controls input and output of data to and from the control unit 14. The control unit includes a microprocessor such as a CPU (Central Processing Unit). The memory unit has memories such as an HDD (Hard Disk Drive), ROM (Read Only Memory), or RAM (Random Access Memory). The control unit performs various calculations based on predetermined programs stored in the memory unit. The control unit outputs various control signals to each of the above-mentioned components via the input / output interface according to the calculation results, thereby controlling the laser processing apparatus 1.

[0022] 3 is a diagram showing a state in which a laser beam is irradiated from the surface 11a of the ingot 11 by a condenser 84. As shown in FIGS. 2 and 3, the laser processing apparatus 1 forms a peeling starting point 15 including a plurality of modified regions 16 inside the ingot 11.

[0023] More specifically, the laser processing apparatus 1 positions the focal point of a laser beam having a wavelength (e.g., a wavelength of 1064 nm) that transmits through the ingot 11 held on the holding table 10 at a position deeper than the surface 11a of the ingot 11, and focuses the laser beam from the surface 11a of the ingot 11 to form the modified region 16. The laser processing apparatus 1 then feeds the ingot 11 for processing so that the focal point moves from one end of the ingot 11 to the other along the X-axis direction, forming the modified region 16 along the X-axis, and then indexes and feeds the ingot 11 a predetermined distance in the Y-axis direction, after which it feeds the ingot 11 for processing so that the focal point moves from the other end of the ingot 11 to one end along the X-axis, repeating the process of forming the modified region 16 along the X-axis. This forms a peeling starting point 15 inside the ingot 11, including the modified region 16 and a crack (not shown) extending from the modified region 16.

[0024] The laser beam irradiation mechanism 8 of the laser processing apparatus 1 is not limited to the configuration described above. FIG. 4 is a diagram illustrating a modified laser beam irradiation mechanism 8. In the modified laser beam irradiation mechanism 8, a laser beam generating unit 82 further includes a branching unit 83 in addition to a laser oscillator 80 and an output adjustment unit 81. The branching unit 83 branches the laser beam, whose output has been adjusted by the output adjustment unit 81, into multiple beams (e.g., five beams) at predetermined intervals in a predetermined direction within the XY plane. For example, by branching the laser beam in the Y-axis direction within the XY plane, multiple modified regions 16 can be formed along the X-axis direction in a single processing feed.

[0025] (peeling device) 5 and 6 are schematic side views of the delamination apparatus 9. Fig. 5 is a diagram showing a state in which ultrasonic waves are being applied to the ingot 11, and Fig. 6 is a diagram showing a state in which the wafer W is being delaminate from the ingot 11.

[0026] The peeling device 9 includes a cylindrical holding table 90 that holds the ingot 11 with the surface 11a of the ingot 11 facing up, an ultrasonic oscillation unit 91 that applies ultrasonic waves to the ingot 11, a peeling unit 96 that peels a wafer W (see Figure 6) from the ingot 11, and a moving mechanism 100 that moves the ultrasonic oscillation unit 91 and the peeling unit 96 horizontally.

[0027] The holding table 90 holds the ingot 11, for example, via an epoxy resin adhesive, or by suction using a suction force generated by a suction source (not shown). The holding table 90 is rotatable about an axis that passes through the center in the radial direction and extends in the vertical direction.

[0028] The moving mechanism 100 has a rectangular opening 101 extending horizontally, and a moving piece 110 that supports the ultrasonic oscillation unit 91 and a moving piece 120 that supports the peeling unit 96 are provided so as to be movable along the opening 101. Although not shown in the figure, the moving mechanism 100 is configured to include a ball screw connected to the moving pieces 110 and 120, a motor that rotates the ball screw, and the like.

[0029] As shown in FIG. 5 , the ultrasonic oscillator unit 91 includes an ultrasonic vibrator 92 having an end face 92a facing the surface 11a of the ingot 11 held on the holding table 90, which applies ultrasonic waves to the ingot 11; a liquid supply nozzle 93 for supplying liquid (e.g., pure water) between the surface 11a of the ingot 11 and the end face 92a of the ultrasonic vibrator 92; a vibrator lifting mechanism 94 extending downward from the underside of the moving piece 110 and adjusting the vertical position of the ultrasonic vibrator 92; and a nozzle lifting mechanism 95 extending downward from the underside of the moving piece 110 and adjusting the vertical position of the liquid supply nozzle 93. The vibrator lifting mechanism 94 and the nozzle lifting mechanism 95 may be configured with an air cylinder, a ball screw, a motor, or the like. The dashed arrows in FIG. 5 indicate the flow of liquid ejected from the liquid supply nozzle 93.

[0030] The ultrasonic vibrator 92 is positioned by the vibrator lifting mechanism 94 at a position where a small gap (for example, 0.6 mm) is provided between the end face 92a and the surface 11a of the ingot 11. The ultrasonic waves applied to the ingot 11 have a frequency of, for example, 20 kHz to 50 kHz.

[0031] While applying ultrasonic waves to the ingot 11, the liquid supply nozzle 93 continues to supply liquid to the gap between the end face 92a of the ultrasonic vibrator 92 and the surface 11a of the ingot 11 to form a liquid layer WL. The ultrasonic waves irradiated from the ultrasonic vibrator 92 are transmitted to the ingot 11 through the liquid layer WL, extending the crack at the peeling starting point 15 formed in the ingot 11. This reduces the strength of the peeling starting point 15.

[0032] The separation unit 96 includes a suction pad 97 that suction-holds the wafer W to be separated from the ingot 11, and a pad lifting mechanism 98 that extends downward from the lower surface of the moving piece 120 and adjusts the vertical position of the suction pad 97. The pad lifting mechanism 98 may be formed of an air cylinder, a ball screw, a motor, or the like.

[0033] 6, after ultrasonic waves are applied to the entire surface 11a of the ingot 11, the moving pieces 110 and 120 move, and the suction pad 97 moves to a position facing the ingot 11 held on the holding table 90. Then, the peeling unit 96 adsorbs the surface 11a of the ingot 11 to the suction pad 97 and moves the suction pad 97 upward, thereby peeling off the plate-like object including the surface 11a of the ingot 11 from the peeling starting point 15 of the ingot 11 as a wafer W.

[0034] (Wafer manufacturing method) Next, an embodiment of the wafer manufacturing method of the present invention will be described.

[0035] The processing by the laser processing device 1 and the peeling device 9 described above is repeatedly performed on the ingot 11, and a plurality of wafers W are produced from one ingot 11. For example, a plurality of wafers W each having a thickness of 0.4 mm are produced from an ingot 11 having a thickness of 40 mm.

[0036] When one ingot 11 is repeatedly processed by the laser processing device 1 and the delamination device 9 and the ingot 11 becomes thinner, it becomes difficult to delaminate the wafer W from the ingot 11 even when ultrasonic waves are applied by the ultrasonic oscillation unit 91 of the delamination device 9. Specifically, when ultrasonic waves are applied to an ingot 11 having a certain thickness, the upper and lower portions of the ingot 11 vibrate out of phase with respect to the delamination starting point 15, promoting the extension of cracks at the delamination starting point 15 formed in the ingot 11. On the other hand, when ultrasonic waves are applied to the ingot 11 in a thin state (for example, when the thickness of the ingot 11 is about 5 mm), the weight difference between the upper and lower portions of the ingot 11 with respect to the delamination starting point 15 becomes smaller, and the phase difference between them becomes smaller during vibration, causing them to vibrate together. This makes it difficult for cracks formed at the separation starting points 15 in the ingot 11 to extend, and as a result, it becomes difficult for the wafer W to separate from the ingot 11.

[0037] Therefore, in the method for manufacturing the wafer W of this embodiment, the substrate 7 is attached to the back surface 11b of the ingot 11, and ultrasonic waves are applied to the ingot 11 with the substrate 7 attached from the front surface 11a.

[0038] The substrate 7 is a member that is significantly heavier than the wafer W to be manufactured, and is attached to the back surface 11b of the ingot 11 via, for example, an epoxy resin adhesive or tape. The substrate 7 is formed in a plate shape and has a thickness of, for example, 5 mm or more, but the thickness can be set arbitrarily and may be less than 5 mm. The substrate 7 is formed from glass, silicon, resin, ceramics, etc., and may be formed from the same material as the ingot 11. In the example shown in FIG. 5, the substrate 7 has the same diameter as the ingot 11, but it may also have a smaller or larger diameter than the ingot.

[0039] In this way, since the substrate 7 is attached to the back surface 11b of the ingot 11, sufficient weight is imparted to the ingot 11 even if the ingot 11 is thinned. Therefore, when ultrasonic waves are applied to the ingot 11, a sufficient weight difference occurs between the upper and lower portions of the ingot 11 relative to the delamination starting point 15, causing them to vibrate out of phase with each other, thereby promoting the extension of cracks at the delamination starting point 15 formed in the ingot 11. Therefore, even if the ingot 11 is thinned, the wafer W can be successfully delaminate from the ingot 11, resulting in improved manufacturing efficiency of the wafer W.

[0040] 7 is a flow diagram of one embodiment of a wafer manufacturing method. The wafer manufacturing method includes a bonding step S1 of bonding a substrate 7 to the back surface 11b of an ingot 11, a delamination start point forming step S2 of forming delamination start points 15 in the ingot 11 by a laser processing device 1, and a delamination step S3 of delaminating a wafer W from the delamination start points 15 of the ingot 11 by a delamination device 9.

[0041] As described above, in the delamination start point forming step S2, the focal point of the laser beam is positioned deeper than the surface 11a of the ingot 11, and the laser beam is irradiated from the surface 11a to form a modified region 16 and a delamination start point 15 including a crack extending from the modified region 16. In the delamination step S3, ultrasonic waves are applied to the surface 11a of the ingot 11, thereby delaminating the plate-like object including the surface 11a of the ingot 11 as a wafer W from the delamination start point 15. The delamination start point forming step S2 and the delamination step S3 are repeatedly performed, and a plurality of wafers W are produced from the ingot 11.

[0042] The attaching step S1 is preferably performed, for example, before the first peel start point forming step S2 of the repeatedly performed peel start point forming steps S2 and S3. By attaching the substrate 7 to the ingot 11 from the beginning, work efficiency can be improved compared to the case where the substrate 7 is attached to the ingot 11 after the ingot 11 has been thinned. Note that the attaching step S1 may be performed after the ingot 11 has been thinned.

[0043] (Variation) 8 shows a modified example of the delamination apparatus 9. The modified delamination apparatus 9 has a water tank 99 containing a liquid, and an ultrasonic vibrator 92, an ingot 11, and a substrate 7 are placed in the liquid. That is, ultrasonic waves irradiated from the ultrasonic vibrator 92 are applied to the ingot via the liquid contained in the water tank 99. This configuration also facilitates the extension of the crack at the delamination starting point 15 formed in the ingot 11.

[0044] Although one embodiment of the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiment may be combined in any manner without departing from the spirit of the invention.

[0045] For example, the wafer manufacturing method of the above-described embodiment has been described with reference to an example in which the workpiece is an ingot 11, but the present invention is not limited to this, and the workpiece may be, for example, a wafer W. That is, by performing the wafer manufacturing method of the above-described embodiment on a single wafer W, the single wafer W may be further divided into a plurality of wafers. In this case, since the substrate 7 is attached to the wafer W in the peeling step S3, a sufficient weight is applied to the wafer W, which is a thin plate-like object, and a plurality of wafers are successfully peeled from the wafer W.

[0046] This specification describes at least the following: In parentheses, components corresponding to those in the above-described embodiments are shown as examples, but the present invention is not limited to these.

[0047] (1) A wafer manufacturing method for manufacturing a wafer (wafer W) from a workpiece (ingot 11, wafer W) having a first surface (front surface 11a) and a second surface (back surface 11b) opposite to the first surface, a peeling origin forming step (peeling origin forming step S2) in which a focal point of a laser beam having a wavelength that is transparent to the workpiece is positioned deeper than the first surface of the workpiece, and the laser beam is irradiated from the first surface to form a modified region (modified region 16) and a peeling origin (peeling origin 15) including a crack extending from the modified region; a peeling step (peeling step S3) of peeling a plate-like object including the first surface of the workpiece as the wafer from the peeling starting point by applying ultrasonic waves to the first surface of the workpiece, In the peeling step, the workpiece has a substrate (substrate 7) attached to the second surface. Wafer manufacturing method.

[0048] According to (1), since the substrate is attached to the second surface of the workpiece in the peeling step, even if the workpiece is thin or has become thin, sufficient weight is imparted to the workpiece, and the wafer is successfully peeled off from the workpiece.

[0049] (2) A method for manufacturing a wafer according to (1), the substrate is attached to the second surface of the workpiece before the peeling start point forming step that is first performed among the peeling start point forming step and the peeling step that are repeatedly performed on the workpiece; Wafer manufacturing method.

[0050] According to (2), by attaching a substrate to the workpiece from the beginning, work efficiency can be improved compared to attaching a substrate after the workpiece has become thin. [Explanation of symbols]

[0051] 7 Substrate 11 Ingot (workpiece) 11a Surface (first surface) 11b Back side (second side) 15 Peeling origin 16 Modification Area S2 Peeling initiation step S3 Peeling step W Wafer (wafer, workpiece)

Claims

1. A wafer manufacturing method for manufacturing a wafer from a workpiece having a first surface and a second surface opposite to the first surface, comprising: a delamination initiation forming step of forming a delamination initiation including a modified region and a crack extending from the modified region by irradiating the workpiece with a laser beam having a wavelength that is transparent to the workpiece from the first surface, with the focused point of the laser beam positioned deeper than the first surface of the workpiece; a peeling step of peeling a plate-like object including the first surface of the workpiece as the wafer from the peeling starting point by applying ultrasonic waves to the first surface of the workpiece, In the peeling step, a substrate is attached to the second surface of the workpiece. Wafer manufacturing method.

2. 2. The method for manufacturing a wafer according to claim 1, the substrate is attached to the second surface of the workpiece before the peeling start point forming step that is first performed among the peeling start point forming step and the peeling step that are repeatedly performed on the workpiece; Wafer manufacturing method.

Images